Thursday, July 27, 2006

Life in the Oxford Clay sea

Following the metriorhynchid post a few people have asked for more details on the Oxford Clay fauna. Luckily the accompanying image shows you all you need to know :) [for the same image at much better resolution visit the relevant page at my flickr site]. Note that it’s a CARTOON (in fact it was deliberately made to go on the front of a t-shirt). The term Oxford Clay refers to a series of mudrocks, formally grouped together as the Oxford Clay Formation, laid down during the Callovian and early Oxfordian of the Middle Jurassic, a time when shallow tropical seas covered much of Europe. Layers of Oxford Clay several hundred metres thick were deposited over Britain and northern France. Judging by the huge number of fossils discovered in the unit, organic productivity was extremely high and rich sources of terrestrially-derived nutrients must have been discharged into the sea. Pretty much everything you’d want to know about the Oxford Clay Formation is included in Martill & Hudson (1991).

The most abundant macrofossils of the Oxford Clay Formation are ammonites and belemnites. Fishes were also diverse and abundant – there were a number of sharks and other chondrichthyans but also bony fishes, and among them is probably the biggest bony fish of them all: Leedsichthys. In the picture here it looks like an immense tuna with a sort of little bony cap on its head, and this is because I followed the very odd life restoration produced by Martill (1985). How big Leedsichthys was has been controversial, but last I heard it was definitely over 10 m long.

Enough of the non-tetrapods. Marine reptiles are what make the Oxford Clay really interesting, and they’re represented by three groups: thalattosuchian crocodilians, plesiosaurs and ichthyosaurs. Thalattosuchians – the ‘sea crocodiles’ – are represented by both of their sub-groups, the amphibious teleosaurids and the fully aquatic metriorhynchids. Unlike metriorhynchids, teleosaurids possessed dorsal osteoderms. Their limbs, though proportionally small, were apparently not unlike those of extant crocodilians so they could likely still use them to move around on land. Two metriorhynchids (both coloured black) are in the scene, while the teleosaurid Steneosaurus (the long-snouted gharial-like crocodilian) swims at centre-left.

Plesiosaurs included both long-necked and short-necked forms. The latter, generally known as pliosaurs, include the huge scary macropredator Liopleurodon, shown at top right biting an ichthyosaur to death. Its immense long-jawed skull and huge, subconical caniniform teeth were well suited for predation on other marine reptiles, and numerous Oxford Clay reptiles exhibit bite marks that match Liopleurodon teeth (Anderson 2005). As in the case of Leedsichthys, the total length reached by Liopleurodon has been controversial. It definitely got to 6 m (Noè et al. 2003), and perhaps to 10 m, with some unpublished bits and pieces hinting at lengths of 15 m or so (McHenry et al. 1996, Naish et al. 2001).

A smallish, gracile-snouted pliosaurid, Peloneustes, is shown at far left in the scene. There are some indications that Peloneustes had particularly big wing-like paddles (Bakker 1993), but further study is needed to confirm this. Its slim snout suggests that it wasn’t a macropredator. The small, short-necked plesiosaur near the sea floor is the pachyostotic pliosaurid Pachycostasaurus, described by Cruickshank et al. (1996). Only known from one juvenile specimen that would have been about 3 m long, it’s poorly known but seems to have been a specialised bottom-cruising form. It might then have preyed on benthic animals, such as burrowing shrimps. The adjacent image of a Peloneustes skeleton is borrowed from

Long-necked plesiosaurs are represented in the Oxford Clay by Cryptoclidus, Muraenosaurus and a few others. Cryptoclidus had numerous gracile teeth and has usually been interpreted as a predator of small prey like little fish or crustaceans and is relatively well known thanks to recent redescriptions (Brown 1981, Brown & Cruickshank 1994). Views on Muraenosaurus have changed recently. Conventionally imagined as a dainty-headed predator of small prey, and an early elasmosaurid, new specimens show that it was quite robust-skulled with features suggesting that its head was well suited for handling fairly large prey (M. Evans, data presented at SVPCA). Rather than being an elasmosaurid, it may in fact be a close relative of the cryptoclidids (O’Keefe 2001).

Finally, ichthyosaurs. Only thunniform Ophthalmosaurus – named for its immense eyes – is known from the Oxford Clay, though jaw fragments sporting big teeth have been suggested to belong to a second genus by some workers. However, these fragments might belong to Ophthalmosaurus as, while usually characterised as toothless, there are now indications that this wasn’t so. The huge eyes suggest that Ophthalmosaurus was a deep-diver, perhaps hunting well offshore for deep-sea cephalopods. The adjacent image is taken from the Saurier Museum Rundgang site.

And I could say more but I tried to be as brief as possible. Coming next: Why putting your hand in a peccary’s mouth is a really bad idea. For the latest news on Tetrapod Zoology do go here.

Refs - -

Anderson, K. 2005. A new system of classifying bite marks on marine reptile bones from the Oxford Clay, Peterborough. The Quarterly Journal of the Dinosaur Society 4 (3), 12-15, 28.

Bakker, R. T. 1993. Plesiosaur extinction cycles - events that mark the beginning, middle and end of the Cretaceous. In Caldwell, W. G. E. & Kauffman, E. G. (eds) Evolution of the Western Interior Basin: Geological Association of Canada, Special Paper 39, 641-664.

Brown, D. S. 1981. The English Upper Jurassic Plesiosauroidea (Reptilia) and a review of the phylogeny and classification of the Plesiosauria. Bulletin of the British Museum of Natural History (Geology Series) 35, 253-347.

- . & Cruickshank, A. R. I. 1994. The skull of the Callovian plesiosaur Cryptoclidus eurymerus, and the sauropterygian cheek. Palaeontology 37, 941-953.

Martill, D. M. 1985. The world’s largest fish. Geology Today 2, 61-63.

- . & Hudson, J. D. 1991. Fossils of the Oxford Clay. The Palaeontological Association, London.

McHenry, C., Martill, D., Noè, L. & Cruickshank, A. 1996. Just when you thought it was safe to go back to the water - the biggest pliosaur yet. Palaeontology Newsletter 32, 22.

Naish, D., Noè, L. F. & Martill, D. M. 2001. Giant pliosaurs and the mysterious ‘Megapleurodon’. Dino Press 4, 98-103.

Noè, L., Liston, J. & Evans, M. 2003. The first relatively complete exoccipital-opisthotic from the braincase of the Callovian pliosaur, Liopleurodon. Geological Magazine 140, 479-486.

O’Keefe, F. R. 2001. A cladistic analysis and taxonomic revision of the Plesiosauria (Reptilia: Sauropterygia). Acta Zoologica Fennica 213, 1-63.

Sunday, July 23, 2006

My party and those marvellous metriorhynchids

[From left to right, the photo shows: Mike P. Taylor, Jeff Liston, Lorna Steel, Luis Rey, Carmen Naranjo, Anthony Butcher, Darren Naish, Will D. Naish, Toni Naish, Graeme Elliott, Mark Witton, Julian Hume, Will J. H. Naish. Look, I’d been drinking. A few people had left before I took the photo, and as usual many of those invited didn't turn up. You know who you are].

The party is over and everyone has gone home, and the last to leave was Jeff Liston of the University of Glasgow's Hunterian Museum. That’s not because he’s hard to get rid of, but because we drove him to the airport for his flight home. Jeff has just completed his phd on the immense suspension-feeding* Jurassic fish Leedsichthys, and while – heaven forbid – I’m not going to talk about fish today, it’s the neat insights I got into Oxford Clay marine reptiles that I’m going to cover here (the Oxford Clay is a globally important Middle Jurassic mudstone, stuffed full of fossil marine vertebrates and invertebrates). I have a thing about Mesozoic marine reptiles right now anyway, as I’m trying to finish a project on a pliosaur. More on that later.

* Not ‘filter-feeding’ as I said in a previous post. Jeff tells that filter-feeding is a specific form of suspension-feeding, and one that was likely not practised by Leedsichthys. Huh.

In a poster presented at the 1997 conference on secondarily aquatic vertebrates, Colin McHenry and I proposed that the flippered Jurassic marine crocodilian Metriorhynchus brachyrhynchus might have been a tough, aggressive little mother, a bit like the modern Pygmy killer whale Feresa attenuata. We partly came to this conclusion because a remarkable specimen – a Metriorhynchus tooth embedded in a skull roof bone of a Leedsichthys – indicates that Metriorhynchus was mean enough and nasty enough to take on anything. Metriorhynchus was about 3 m long whereas Leedsichthys was err, umm (checks to see if Dave Martill is around) at least 15 m long. In this case, healed bone around the tooth shows that the Leedsichthys survived the encounter, and swam around with the crocodilian’s tooth embedded in its head (Martill 1986). But, alas, this lovely story has had its day. I’ll say no more as Jeff hasn’t published yet. We move swiftly on.

Crocodilians today are more diverse than most people realise, but – forget this rubbish about crocodilians being evolutionary conservative – the diversity present among the fossil forms is seriously impressive (for a review see Naish 2001: free pdf here). While there are extant crocodilians that spend a lot of time at sea, the fossil record shows us that several groups became specialised for full-time marine life, and among them none were more specialised than the metriorhynchids, a Jurassic-Early Cretaceous group of tubular-skulled crocodilians that had limbs modified into paddles. A specialised down-curved tail tip formed the lower lobe to a tail fin, the upper part of which was formed entirely from soft tissues, though with internal support provided by tall, curved neural spines. We know that the tail fin was present because – like that of ichthyosaurs – it is preserved as a soft-tissue impression in some specimens (as shown in the adjacent image).

Unlike other crocodilians, metriorhynchids are remarkable in lacking the bony scutes that ordinarily cover the dorsal surface, and they are also remarkable for possessing massive laterally projecting prefrontal bones that stick out above and in front of the eye sockets. These expanded prefrontals appear to have gotten larger during the evolution of the group, and their function has always been mysterious: did they somehow protect the eyes during predation behaviour, or did they somehow enhance streamlining? While these possibilities remain untested (to my knowledge) it now seems that the primary function of the bones was that they housed enlarged salt glands, as exceptionally well preserved Argentinian metriorhynchids actually have their salt glands preserved within the prefrontals (Fernández & Gasparini 2000).

Reptiles haven’t evolved hyper-efficient kidneys as mammals have, and living marine reptiles void unwanted salt via specialised cranial glands. We’ve assumed that metriorhynchids (and other fossil marine crocodilians) had salt glands, but now we know exactly where those glands were. And the presence of the glands in this location might explain another unusual aspect of metriorhynchid cranial anatomy, namely the strange elongate, groove-like antorbital fossae present in these animals (the antorbital fossa is an accessory opening present on the side of the skull in archosaurs). Fernández & Gasparini (2000) suggested that the specialised fossae might have been used to drain unwanted saline secretions from the glands – a novel function for the structures not seen in other archosaurs.

Metriorhynchids are commonly depicted in artistic scenes showing Jurassic marine life, but it turns out that they looked rather different from conventional restorations. Most artists have depicted them as looking something like long-tailed pliosaurs, albeit of course with that subtriangular fin at the tail tip. Their fore- and hindlimbs are shown as proportionally large, similar in shape, and about equal in size. But good articulated skeletons show that metriorhynchids were different from this, with a fairly long body and limbs that differ substantially in size and shape. The forelimbs were surprisingly short, rounded paddles with only limited mobility. The hindlimbs were altogether different, being much longer and relatively slender. So Samuel Williston got all this right when he restored a metriorhynchid correctly in his 1914 book Water Reptiles of the Past and Present (see adjacent image), but hardly anyone seems to have taken any notice of him.

Combine these weird limbs with the triangular tail-fin, and you can understand why there has been some uncertainty over how metriorhynchids swam. Hua (1997) showed that the metriorhynchid skull was remarkably porous and hence probably highly buoyant, and that they might therefore have floated at the water surface, ambushing prey with a swift burst. The tail-tip shape is most like that of carchariniform sharks and, according to Hua (1994), suggestive of sudden acceleration employed during slow, stalking predation.

What did metriorhynchids eat? Given that we’re talking about multiple species that differed in snout shape and tooth morphology, it seems that the species varied in their diet and behaviour. Massare (1987) and Vignaud (1997) looked at tooth morphology in Metriorhynchus. They showed that the long-snouted species M. superciliosus and M. leedsi had rather straight, robust, blunt-tipped teeth that belonged to the ‘crunch’ feeding guild, while broad-skulled species like M. cultridens had slender, slightly compressed, carinate teeth (carinae=cutting edges) that belonged to the ‘pierce’ guild.

Based on tooth style and feeding behaviour in living aquatic tetrapods, ‘crunch’ guild animals feed on prey with hard exteriors (such as shelled molluscs) while ‘pierce’ guild animals pierce the bodies of prey like fish. Accordingly, different metriorhynchid species were apparently doing different things, and contemporaneous taxa like the Metriorhynchus species that lived in the Oxford Clay fauna were probably exploiting different prey.

Stomach contents of a metriorhynchid were described by Dave Martill (1986) and included cephalopod hooklets, a belemnite guard and some long bones that Dave identified as those of the pterosaur Rhamphorhynchus. On the basis of these remains he proposed that metriorhynchids were probably opportunistic carnivores which, rather like most extant crocodilians, ate whatever came within reach. The ‘pterosaur’ bones at least proved misidentified however and turned out to be fish bones (Unwin, cited as pers. comm. in Forrest 2003), so the interesting idea of metriorhynchids feeding on pterosaurs presently lacks fossil support. A partial skeleton of the long-necked plesiosaur Cryptoclidus bears tooth marks, apparently made by a metriorhynchid, around the edges of its vertebrae, and Forrest (2003) interpreted this discovery as evidence for scavenging behaviour in members of the group. It is quite plausible then that they fed from submerged or floating carcasses, and given that they were contemporaneous with a diversity of large-bodied bony fishes, sharks, plesiosaurs and ichthyosaurs it’s likely that at least some of their diet was obtained this way.

At least some metriorhynchids look like they were big, scary macropredators whose diets extended beyond fish and molluscs. Dakosaurus, the geologically youngest member of the group, was in the news a lot in 2005 as D. andiniensis, an Argentinian species first named in 1985 (though initially misidentified as a species of Metriorhynchus), was described from new specimens (Gasparini et al. 2005). It even made the cover of National Geographic (Nat Geo image at left). These new fossils showed that D. andiniensis was a really fearsome looking beast, with a deep, broad rostrum and a remarkably low number of big, laterally compressed, serrated teeth. Teeth of this form are termed ziphodont. Metriorhynchids generally have 25-40 teeth in the maxilla, but D. andiniensis has just 10 or 11.

And while serrated teeth are no big deal among terrestrial predatory reptiles, they are in marine forms: mosasaurs have serrated teeth, but the serrations are ultra-fine. We don’t really know what D. andiniensis was doing, but terrestrial reptiles with deep snouts and ziphodont teeth – like theropods and sebecosuchian crocodilians – made a living by taking slashing, debilitating bites from large prey animals. Among marine reptiles and possibly marine tetrapods, D. andiniensis would have been unique.

That’ll do for now. Took Jeff to my trusty slow-worm location, but no sightings today. For the latest news on Tetrapod Zoology do go here.

Refs - -

Adams-Tresman, S. M. 1987. The Callovian (Middle Jurassic) marine crocodile Metriorhynchus from central England. Palaeontology 30, 179-194.

Fernández, M. S. & Gasparini, Z. 2000. Salt glands in a Tithonian metriorhynchid crocodyliform and their physiological significance. Lethaia 33, 269-276.

Forrest, R. 2003. Evidence for scavenging by the marine crocodile Metriorhynchus on the carcass of a plesiosaur. Proceedings of the Geologists’ Association 114, 363-366.

Gasparini, Z., Pol, D. & Spalletti, L. A. 2005. An unusual marine crocodyliform from the Jurassic-Cretaceous boundary of Patagonia. Sciencexpress 10.1126/science.1120803.

Hua, S. 1994. Hydrodynamique et modalités d'allègement chez Metriorhynchus superciliosus (Crocodylia, Thalattosuchia): implications paléoécologiques. Neues Jahrbuch fur Geologie und Paläontologie, Abhandlungen 193, 1, 1-19.

Martill, D. M. 1986. The diet of Metriorhynchus, a Mesozoic marine crocodile. Neues Jahrbuch fur Geologie und Paläontologie, Monatshefte 1986, 621-625.

Massare, J. A. 1987. Tooth morphology and prey preference of Mesozoic marine reptiles. Journal of Vertebrate Paleontology 7, 121-137.

Naish, D. 2001. Fossils explained 34: Crocodilians. Geology Today 17 (2), 71-77.

Vignaud, P. 1997. La morphologie dentaire des Thalattosuchia (Crocodylia, Mesosuchia). Palaeovertebrata 26, 35-59.

Friday, July 21, 2006

Meet peccary # 4

Having spent the better part of the day tidying up the house for the garden party we’re having tomorrow (yet again a celebration of my graduation: will this decadence ever end?), I thought I should try and finish one of the blog posts I said I would write. You know, the one on peccaries [first promised in More on what I saw at the zoo].

Peccaries are predominantly herbivorous, pig-like artiodactyls, restricted today entirely to the Americas, and for reasons that I’ll get to in a minute EVERYONE should be talking about them right now. Living species range in weight from 15-40 kg. They are highly social, living in mixed-sex herds of just a few individuals to several hundred, and females produce just one or two precocial babies that follow the mother soon after birth. Peccaries make an interesting assortment of noises: Collared peccaries Tayassu tajacu produce loud, dog-like barks, and White-lipped peccaries T. pecari scream, bellow and retch when in large groups (small groups tend to be quiet). All species make loud tooth-clacking noises, especially when disturbed.

Peccaries are ecologically flexible, with the three [cough cough] living species being distributed across rainforest, parkland, scrubland, steppe and even desert, and with Collared peccaries in fact occupying all of these habitats. Habits differ according to habitat: rainforest Collared peccaries are diurnal, eat fruit, palm nuts and shrubs, and sleep in burrows, while desert populations are nocturnal, eat mostly cacti, and don’t use burrows. This flexibility is reflecting in their variable tooth anatomy. Judging from fossils the primitive tooth type for peccaries is bunodonty (viz, where each tooth sports multiple low rounded mound-like cusps), but zygodonty (viz, where mound-like cusps are connected by transverse crests) evolved several times. Among living species, the bunodont White-lipped peccary mostly eats nuts while the zygodont Chacoan peccary Catagonus wagneri mostly eats cacti. The Collared peccary includes both bunodont and zygodont individuals across its range, and it seems that desert populations are more zygodont while populations from wetter places tend to be bunodont (Wright 1998). Peccaries are reported to occasionally eat carrion, and they will also eat snails and other invertebrates as well as small vertebrates.

The Collared peccary or Javelina Tayassu tajacu (or Pecari tajacu or Dicotyles tajacu) is the best studied species and is the archetypal peccary, occurring from central Arizona and central Texas south to northern Argentina (though with introduced populations in northern Texas, southern Oklahoma and Cuba). Its nomenclature is a bit confused: some authors use the generic name Dicotyles G. Cuvier, 1817 or Pecari Reichenbach, 1835 for it, but most common is its inclusion within Tayassu Fischer, 1814. Pecari is apparently an objective synonym of Dicotyles and thus not available, and use of Dicotyles therefore depends on whether or not you consider this species distinct enough from the White-lipped peccary to warrant separation. Indeed this confusion is related to a similar controversy over which formal name is used for peccaries: are they Tayassuidae Palmer, 1897 or Dicotylidae Gray, 1868? A few artiodactyl specialists make a point of using the latter name, but the former is more widely used and would easily win in a fight.

Collared peccaries release an odour like cheese or chicken soup, apparently (Emmons 1997). In fact a vernacular name for them in parts of the USA is musk hog, and you are said to smell them before you see them.

The White-lipped peccary, a species that ranges from southern Mexico to Argentina (and has also been introduced to Cuba), is substantially bigger than the Collared peccary. Mostly an animal of forests, it is semi-nomadic. The third species, the Chacoan peccary, Roman-nosed peccary or Tagua, is particularly notable in being both relatively recently discovered in living state, and for being initially named from fossils. I mentioned it before in a post on rodents (New, obscure, and nearly extinct rodents of South America.... and when fossils come alive). The species’ scientific history began in 1930 when, in his lengthy paper on Argentinian fossil peccaries, C. Rusconi named the new subspecies Platygonus carlesi wagneri. By 1948 Rusconi had decided that this form was distinct enough for its own species, P. wagneri.

The story then moves on to 1972 when, while working on a mammal inventory project in the semiarid thorn forest and steppe of the Gran Chaco area of Argentina, Paraguay and Bolivia, Ralph Wetzel and colleagues were surprised to hear from local people of a large peccary – distinct from the Collared and White-lipped – known to them as the tagua, pagua or curé-buro (meaning donkey-pig). Their enquiries eventually led to the successful procurement of tagua skulls, and they clearly represented a third, modern-day peccary species. Yet again we see a case where good, honest, card-carrying zoologists track down an ethnoknown animal with successful results, or in other words an unarguable example of cryptozoological investigation being carried out by people who don’t consider themselves cryptozoologists (for other examples see At last: the Odedi revealed and The interesting and contentious discovery of the kipunji). Rather than being new, it now turned out that the tagua was the same thing as Rusconi’s fossil species Platygonus wagneri: it really was a ‘fossil come to life’. But rather than being a member of Platygonus, a genus known from the Miocene, Pliocene and Pleistocene of both North and South America, Wetzel concluded that the species was instead better classified within Catagonus, a genus first named by Florentino Ameghino in 1904 for Pleistocene Argentinian fossils (Wetzel 1977a, b, Wetzel et al. 1975) [The adjacent picture shows two captive Chacoan peccaries, borrowed from the Florida Museum of Natural History site. The individual at the rear is scent-marking a fence post with its tail gland].

The Chacoan peccary is specialised for life in semiarid forests and steppes. It browses on ground cacti, is reported to not drink, and is superior in cursorial ability compared to other living species. Its teeth are particularly tall-crowned and it only has two hind toes, not three like other living peccaries. Reports from hunters suggest that it occurs in several parts of Bolivia where its presence has yet to be verified (Mayer & Wetzel 1986) and it turns out that its fur was being used in the manufacture of New York coats and hats long prior to 1972.

But here’s the big news. While the 1975 discovery of the Chacoan peccary was a major zoological discovery – indeed one of the most significant mammalogical discoveries of the 20th century – it seems that history is repeating itself, for there is now a fourth living peccary species: the Giant peccary. As in the case of the Chacoan peccary, this new species appears to have been discovered by listening to local people: in this case the Caboclos people (descendants of rubber collectors) of the Brazilian Amazon. And the discover is Marc van Roosmalen, the Dutch primatologist well known for the many new species of primate he has discovered (about 20) within recent years.

After learning of the fabled new peccary, apparently larger than the documented species, van Roosmalen set off with GEO magazine author and film maker Lothar Frenz and two photographers. And after four days of waiting in a hide they were rewarded with views of a group of four of the animals. Good photos were obtained, and one is reproduced here (at top). The animals look distinct from the other living peccaries – they’re most like Collared peccaries but larger and without the collar, and they’re reported to be even bigger than Chacoan peccaries, hence the name Giant peccary.

German newspapers first reported the successful observation of live Giant peccaries in June 2004, and the news was apparently held back in order to coincide its release with the airing of Frenz’s documentary on the expedition. So far as I can tell however, Karl Shuker was first to break the news as he mentioned it in his 2002 book The New Zoo. Citing personal communication from van Roosmalen, Shuker implied that the Giant peccary had first been encountered in January 2000 (Shuker 2002). It also seems that van Roosmalen and Frenz observed the successful capture and killing of one of the animals: an article in Suiform Soundings* entitled ‘New mammal discovered in South America – and eaten’ (Anon. 2004) stated that ‘Frenz said he and van Roosmalen abstained from trying the meat, but collected some of the remains for a genetic study’. The GEO article includes a photo of hunters with a dead Giant peccary (image below), so maybe this is the same individual that Frenz and van Roosmalen watched being eaten.

* The newsletter of the IUCN/SSC Pigs, Peccaries, and Hippos Specialist Group. Formerly Asian Wild Pig News.

GEO magazine published an article (in German) on the discovery in 2004 (the online version is here), and in December 2005 Suiform Soundings published an English version (Carstens 2005). I don’t know if van Roosmalen is planning to publish a description based only on the meat sample he collected (species have been described from photos and tissue samples before, the best known case being that of the Bulo Burti boubou Laniarius liberatus), or if he’s waiting until better material is obtained, but it seems that we have here the valid discovery of a large, terrestrial mammal. That’s a big deal, though admittedly not as big a deal as so many people – zoologists included – still seem to think. Multiple new large mammals have been described in recent years, and there’s every reason to think that more such discoveries will occur in the future.

But, like I said, say hello to peccary number 4. More to come on peccaries soon. For the latest news on Tetrapod Zoology do go here.

Refs - -

Anon. 2004. New mammal discovered in South America – and eaten. Suiform Soundings 4 (2), 66.

Carstens, P. 2005. Scientist find [sic] new species of large mammal. Suiform Soundings 5 (2), 38-39.

Emmons, L. H. 1999. Neotropical Rainforest Mammals: A Field Guide (Second Edition). University of Chicago Press (Chicago & London).

Mayer, J. J. & Wetzel, R. M. 1986. Catagonus wagneri. Mammalian Species 259, 1-5.

Shuker, K. P. N. 2002. The New Zoo. House of Stratus (Thirsk, North Yorkshire).

Wetzel, R. M. 1977a. The extinction of peccaries and a new case of survival. Annals of the New York Academy of Science 288, 538-544.

- . 1977b. The Chacoan peccary, Catagonus wagneri (Rusconi). Bulletin of the Carnegie Museum of Natural History 3, 1-36.

- ., Dubos, R. E., Martin, R. L. & Myers, P. 1975. Catagonus, an ‘extinct’ peccary alive in Paraguay. Science 189, 379-381.

Wright, D. B. 1998. Tayassuidae. In Janis, C. M., Scott, K. M. & Jacobs, L. L. (eds) Evolution of Tertiary Mammals of North America. Volume 1: Terrestrial Carnivores, Ungulates, and Ungulatelike Mammals. Cambridge University Press, pp. 389-401.

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Wednesday, July 19, 2006

The joy of graduation

Yesterday (18th July) was graduation day. How fetching I look in my splendid robes, no? Truly, it was a great day to be standing around in clothes like this, given the 34 degree C temperatures. There are other photos, but I won't post them here. Think 'When newly graduated doctoral candidates attack' and 'Naish: super-doctor!'. Right, back to the leptocleidine pliosaurs.

For the latest news on Tetrapod Zoology do go here.

Monday, July 17, 2006

Finally: big cat kills uncensored and uncut

Something quite important just happened on British TV. Well, important to me. Last week the BBC screened Big Cat Week: a series of five programmes broadcast from Kenya’s Masai Mari, and featuring the day-to-day lives of a number of individual wild lions, leopards and cheetahs. This is essentially a pared-down version of Big Cat Diary, a highly successful TV series the BBC has been showing since September 1996 (go see their website here). Screening the individual life histories of particular cats, the series has followed the animals as they have gone about their business hunting, defending territories, courting, mating and raising cubs, and over the years it has become a multi-generational soap-opera as the original stars have died or disappeared, their places being taken by their offspring or by the animals that usurped them. It is easily one of the best things on TV in my opinion – so many remarkable things have been filmed.

As a spin-off for the digital channel BBC Three, the BBC has also been broadcasting Big Cat Week Uncut, with each episode being shown immediately after that day’s Big Cat Week episode. And uncut it truly was. One of things that has always bugged me about nature documentaries is that full acts of predation are almost never shown: you get to see a bit of the chase, then the predators catching their prey, and then a bit of the predators eating the deceased victim. This goes for predation behaviour in lions, hunting dogs, spotted hyaenas, wolves and killer whales.

Why are kills edited? Basically because they are often far more gory than most people expect – kills are often not clean and simple, but may involve the prey animal getting eaten when still alive. Sure, experienced individuals belonging to species that practise precision bites, such as large cats, may well execute a fairly tidy, bloodless killing, but this does not always happen, plus some species – notably hyaenas and hunting dogs – seem to ordinarily take chunks out of the prey while it’s still very much alive. In some cases the prey dies from the resulting trauma and blood-loss, and not from tidy bites to its throat or vital organs. Let me add, by the way, that I’m basing these bold assertions on what I’ve read in books and seen on TV: I have no field experience whatsoever as goes African megafauna. I also want to add that I’m interested in this area, not because I have a love of gore and violence, but because I find macropredation behaviour a fascinating part of the evolutionary biology of the species that practise it.

As you’ve by now guessed, the big deal about Uncut is that it has been showing uncensored kills. To most viewers I hope that these scenes are eye-opening and remarkable, even if gory and horrific, and I have been pleased to see them. Simon King, one of the three presenters*, provides commentary on the footage as he views it. His take on what happens is insightful and accurate, though he has a really annoying habit of describing animals as being ‘designed’ for certain functions. I met King during 2001 when he was presenting Live From Dinosaur Island. We spoke very briefly about co-operative hunting in corvids and raptors, and about Big Cat Diary. I got to tell him how awesome I thought the series was, but that was about it.

* The other two are Jonathan Scott, well known for his work on the Serengeti, and Saba Douglas-Hamilton, qualified social anthropologist and daughter of elephant expert Iain Douglas-Hamilton.

First introduced to the series when she was a tiny cub in 2005, Duma the cheetah is now about a year old and nearly equal in size to her mother (the image of Duma used above is from the Duma slideshow on the BBC website). Both cats were filmed walking through long grass when Duma spotted a Grant’s gazelle Gazella granti reclining ahead, only its horn tips visible. Alerted by Duma’s body language, her mother then began stalking too, and eventually both cats got to within a few metres of the still oblivious gazelle. At up to 80 kg, a male Grant’s gazelle is near the upper limit of the cheetah’s typical prey choice, though they will also take 90-kg antelopes like topi on occasion, and Hans Kruuk documented cheetahs killing wildebeest and young kudus and zebras.

Almost on top of the gazelle, the cheetahs – very interestingly – deliberately startled it into a run (one cheetah, I forget which, did this by hunching its shoulders and making distinctive stiff-legged bounds in the gazelle’s direction). The gazelle didn’t have a chance, and both cheetahs were on top of it immediately. After a bit of a struggle, it was pinned down, and Duma began to administer a throat bite. But it seems she wasn’t very good at it, and gave up far too early. Experienced cheetahs may require 20 minutes to be confident that they’ve suffocated their prey, though this might also be the amount of time it takes for them to recover from the exertions of their run (Brakefield 1993). Duma, however, seemed to be holding on for only a few minutes, if that. The gazelle struggled to its feet and had to be pinned down again. Again, Duma tried a throat bite, and again she gave up too soon. But by now her mother had secured a firm purchase on the gazelle’s rump, had bitten through the skin, and had started feeding on the animal’s haunches. Again the gazelle struggled to its feet, panting and wide-eyed, and again it had to be pinned down. And again another unsuccessful attempt at strangling was performed. As the gazelle stood up again, still struggling and very much alive, it essentially had most of its back end opened up, with a huge bloody hole showing that the mother cheetah had managed to eat in as far as the guts. It was literally being eaten alive. Though the end of the sequence wasn’t shown, King explained that the gazelle must have endured a slow, agonising death [the adjacent image, showing two cheetahs taking down an impala, is nothing to do with Duma or the attack I've just been discussing: it's from].

In The Velvet Claw (required watching if you’re interested in the evolution of carnivorans: first broadcast by the BBC in 1992), a sequence featuring hostilities between hyaenas and lions showed a similar thing. This time, a lion pride captured a Cape buffalo Syncerus caffer. The lions were clearly eating the animal’s back end, yet its head was up and it was definitely still alive (if I remember correctly, the animal’s head is partially obscured during the sequence by a superimposed ‘less alive looking’ head!).

During another episode of Uncut, King looked in detail at Spotted hyaenas Crocuta crocuta, and in particular at the interactions that hyaenas have with lions. As most people know, the two species hate one another, and will kill each other when the opportunity arises. But with one hyaena weighing (at most) 90 kg compared to a female lion’s 120-180 kg, and a male’s 150-260 kg, hyaenas rarely get to kill adult lions. A lion pride known properly as the Bila Shaka Pride, but dubbed the Marsh Pride for TV, has been a constant presence since filming for Big Cat Diary began. Spending most of their time near Musiara Marsh, the pride’s history is complex (Scott 2001), as is that of any pride when it’s studied for long enough.

During one episode of Uncut, a hyaena clan spent a lot of time pestering some of the pride’s lionesses. But things went badly wrong for the hyaenas when two male lions showed up. One unfortunate hyaena got stuck in mud: the lions caught it, pinned it down, and one of the lions bit hard into its neck. Smothered in mud, it hung limp in the lion’s jaws. But it wasn’t dead, and when the lion released it, it clamped onto the lion’s upper lip. It was an awesome sequence as, though the hyaena was killed eventually, it endured phenomenal trauma before succumbing. Cats are hard to kill, and I guess hyaenas are too. At the end of the sequence, the lions carried the body out of the mud and water where the fighting had occurred and dumped it on a dry bank. They had no plans to eat the hyaena – they just wanted it dead [the adjacent image is again nothing to do with the case discussed here, and is borrowed from].

Dean William Buckland once wrote that predatory animals were equipped with sharp teeth and claws so that death was swift and merciful. While nature isn’t all red in tooth and claw as some people like to say, predation is often decidedly unpretty, and compassion is a human trait. We might not like the idea that predators sometimes start eating their prey while it’s still alive, but the fact that it happens is an interesting facet of their behaviour as worthy of knowing as any other.

For the latest news on Tetrapod Zoology do go here.

Refs - -

Brakefield, T. 1993. Big Cats: Kingdom of Might. Voyageur Press (Stillwater, MN).

Scott, J. 2001. Pride under siege. BBC Wildlife 19 (2), 42-48.

Saturday, July 15, 2006

‘Angloposeidon’, the unreported story, part IV

This post follows on from the previous three (part I here, part II here, and part III here), and if you read to the end of part III you’ll know that I got as far as talking about the media attention that the Naish et al. (2004) paper received in late November 2004. As mentioned, I spoke to lots of journalists, and among them, one in particular had something very interesting to say. Unfortunately I forget his name, but I do recall that he was based on the Isle of Wight. His recollection was that the specimen had in fact been brought to the attention of the media before. Basing my conclusions on what happened with Eotyrannus, this is almost certainly correct.

Steve Hutt’s plan with Isle of Wight dinosaur discoveries (and you’ll recall from the previous posts that Steve was the first person other than Gavin Leng to become acquainted with MIWG.7306) has always been to get publicity both on the discovery of a specimen, and on the publication of the formal description. So Eotyrannus was in the newspapers as a new dinosaur discovery in 1998, and then again in 2001 when it was formally named and described (Hutt et al. 2001). Most of us hold off on talking to the press until our technical work has been published, but I’m not knocking Steve for his double-whammy approach, as the media are evidently interested enough to cover these stories twice.

So while I’ve never seen the relevant articles, it seems that MIWG.7306 was reported in the newspapers at the time of its discovery. It also turns out that a semi-technical report was published on the specimen, and to my annoyance I didn’t find out about this until recently. The article in question is by Jon Radley, well known for his excellent work on Wealden stratigraphy, and it includes two paragraphs on the specimen and a photo (Radley 1997, pp. 108-109). The relevant section reads (though with some typos corrected)…

A brachiosaurid sauropod vertebra from the Wessex Formation (Wealden Group, Lower Cretaceous) of Sudmoor Point

In the autumn of 1993 Mr. G. Leng discovered a large sauropod vertebra derived from a plant debris bed exposed in the cliff top approximately 1 km northwest of Chilton Chine (SZ 399825). Mr. Leng has generously donated this important specimen to the Museum of IW Geology (MIWG 7306) with the permission of the National Trust. The specimen is preserved in a large, well-cemented sideritic concretion and is consequently only partly crushed. Small quantities of pyrite occur in the bone material and appear to be quite stable.

The bone is 0.75 m long and now ranks as the largest sauropod vertebra in the museum collection. Mr. S. Hutt has identified it as a cervical (neck) vertebra of an adult brachiosaurid sauropod. It is deeply socketed and possesses large prezygapophyses and postzygapophyses. The nature of construction is extremely light with well developed networks of pleurocoels (air chambers). From its size, one can calculate that it came from an animal approximately 22 to 25 m in length. Most brachiosaurid remains discovered so far on the Island are of considerably smaller animals – Radley & Hutt (1993) provided outline details of a recent find. It is hoped that the vertebra will be on temporary display in the museum in the near future.

A few things make Jon’s article particularly interesting. The ‘autumn of 2003’ date he provides is different from the 2002 one I was provided by MIWG staff, and the 750 mm length he provides is of course accurate (and presumably so because it’s the centrum length alone). The article also includes the first ever figure of the specimen, showing it in its unprepared, siderite-encased case (a scan of that figure is included here). Of course the article doesn’t in any way diminish the value of the final published description (Naish et al. 2004) and is nothing more than an initial, preliminary report. I just wish that I’d known about it when writing Dinosaurs of the Isle of Wight and the final MIWG.7306 paper, as then I could have cited it. Oh well.

It turns out that the final published description – while not bad as descriptions go – only really scratches the surface in terms of what information we can learn from MIWG.7306. Previously I discussed the incredible fact that brachiosaurid vertebrae are as much as 80 or 90% air, and that this degree of pneumatisation might mean an awful lot as goes physiology and biology. Because MIWG.7306 is broken into halves, making examination of its pneumatic interior possible, a current project is to get lots more data about pneumaticity out of it. That’s ongoing however, so I don’t want to talk more about it now.

MIWG.7306 also gives us new information on the diversity and distribution of brachiosaurids. MIWG.7306 clearly shares a number of detailed features only with Brachiosaurus of the Late Jurassic of North America and eastern Africa, and with Sauroposeidon of the Early Cretaceous of the USA, and as discussed in the paper (Naish et al. 2004) it seems that MIWG.7306 might even be phylogenetically intermediate between these two forms. One of the big questions concerning brachiosaurids is which other sauropods are members of this clade too, and this is an area currently under study by my colleague Mike P. Taylor, who has a lot of new data (and some new species) on this subject.

But if MIWG.7306 represents an animal that is ‘phylogenetically intermediate’ between Brachiosaurus and Sauroposeidon, and given that it’s been publicised as a ‘new’ dinosaur, why didn’t we name it? That’s a good question, and there are two answers.

Firstly, most experts agree that specimens should only be named as new taxa if they can be can be shown to be diagnostic: that is, they possess unique features which allow them to be differentiated from other taxa. Given that taxa evolve from ancestors, and evolve into descendants, there aren’t sharp boundaries between species and genera – rather, they grade into one another. Consequently, so-called diagnostic features must also, at some stage in any lineage, morph into the slightly different conditions present in ancestors and/or descendants, and multiple intermediate conditions must exist between any two ‘diagnostic’ end-states. We therefore, arbitrarily, chose cut-off points in how much variation we tolerate within any taxon – in other words, we arbitrarily decide how we chop up a lineage into those units we call species and genera. As a rough rule of thumb this all works, more or less, so long as it’s understood that species are artificial segments of lineages (though having said that, any species that can be shown to be the ‘end point’ of its respective lineage is a clade, and of course this applies to living species given that they don’t have descendants). Anyway, I’m going off here at a tangent: this is the sort of heavy philosophical stuff that systematists have been arguing over for decades.

MIWG.7306 possesses loads of anatomical features that are also present in Brachiosaurus and Sauroposeidon, and it even shares some features that are present in Sauroposeidon and not in Brachiosaurus but, so far as we can tell, it doesn’t possess any features that are unique and thereby allow it to be reliably differentiated from all other sauropods. That’s almost certainly is an artefact resulting from the fact that we only have two cervical vertebrae of course – if we had the whole skeleton things would be different. But, as it stands, MIWG.7306 cannot presently be diagnosed as a new species.

Actually, for a while I’ll admit that we thought that MIWG.7306 could be diagnosed. One of several unsolved mysteries about the specimen is the identity of a bizarre, oddly shaped chunk of bone found encased in the same nodule (Dave Martill is holding it in the adjacent image). Smoothly convex on one side, but with a series of subparallel ribs on the other, it was tentatively identified by David Cooper as part of the apex of the neural spine. I thought later on that it might be a partial diapophysis*, as those of brachiosaurids can descend ventrally from the side of the centrum as plate-like processes with smoothly convex lateral surfaces. If this identification is right, then the diapophysis of MIWG.7306 is uniquely odd, as it possesses a small rhomboidal opening near its (presumed) posterior border. Such a feature is unknown elsewhere in sauropods, and it’s the sort of feature we might chose to regard as diagnostic. I now have serious doubts about my identification of this object as a diapophysis, and I think that David was right with the neural spine identification. Images of the object were shown to sauropod-obsessed colleagues, and they remains uncertain as to what it is however, so the thing remains mysterious.

* In tetrapods with two-headed ribs, the more ventral rib head contacts a facet on the vertebra known as the parapophysis (plural parapophyses), while the more dorsal rib head contacts a facet known as the diapophysis (plural diapophyses). The positions of the parapophyses and diapophyses change along the length of the vertebral column, and indeed their relative positions allow us to identify where in the sequence an isolated vertebrae came from.

The second answer [to the question: why didn’t we name it?] is that MIWG.7306 comes from a geological unit (the Wessex Formation) where there are already lots of named sauropods, virtually all of which are based on non-overlapping fragments, such as vertebrae. What’s more, some of these (notably Eucamerotus, a form named for dorsal vertebrae), seem to be good honest brachiosaurids closely related to Brachiosaurus (and hence to MIWG.7306). It’s possible and perhaps likely that some of the other Wessex Formation sauropods, Eucamerotus among them, actually represent the same taxon as MIWG.7306, though of course this can’t be tested until we have good, more complete specimens (here you’ll recall the Barnes High brachiosaurid, still floating in scientific limbo). In view of this situation it would be regarded as bad practise to coin a new name for MIWG.7306.

Partly because it’s easier to say than ‘MIWG.7306’ we’ve elected to use a totally unofficial nickname for the taxon represented by MIWG.7306, and this is ‘Angloposeidon’, coined by brachiosaurophile Mike P. Taylor (who is irritated by my continual reference to him as such*). So long as it stays on the internet we’re ok: it must NOT be published!

* So why do I do it? Because there is already a well known Mike Taylor in the world of tetrapod zoology: the marine reptile expert Mike A. Taylor.

What do other experts think of MIWG.7306? During the long period of time in which the manuscript was in preparation I spoke to several European colleagues who told me of new sauropods from Portugal and Spain that would easily outclass MIWG.7306 in terms of size. I had this on my mind all the way through the submission process, and at any time I expected there to be some report of a new European sauropod that had a total length exceeding 30 m. But even today such discoveries have yet to materialise, and having now seen some of the specimens in question I know that they fail to come close to the 20 m + estimated for MIWG.7306. The accompanying image – a composite produced by Matt Wedel and Mike – shows the forelimb of one of these ‘gigantic’ European sauropods (with me for scale) adjacent to the Chicago mount of Brachiosaurus (with Mike for scale). ‘Angloposeidon’ was about equivalent in size to Brachiosaurus so far as we know, and as you can see, Brachiosaurus knocks spots off the European animal (which, by the way, is as yet undescribed and unnamed).

The MIWG.7306 paper hasn’t been cited much in the literature, but this results from the fact that bugger all has been published on Lower Cretaceous British sauropods since 2004. Matt Wedel – pneumaticity and giant brachiosaurid expert – has certainly been interested and even came to see the specimen in March 2004. He’s agreed with our interpretations, and in recent publications on Sauroposeidon has noted that MIWG.7306 shows that Britain was once home to a close relative of this Oklahoman giant (Wedel 2005: free pdf here). Sauroposeidon is from the Aptian-Albian Antlers Formation, whereas the Wessex Formation that yields MIWG.7306 is just a little older, being late Barremian in age. We also know that similar giant brachiosaurids were present in the Aptian-Albian Cloverley Formation of Montana, as evidenced by a single cervical vertebra held today at the Yale Peabody Museum. The specimen is from a juvenile brachiosaurid but, as Wedel (2005) noted, at 47 cm in length the specimen ‘is longer than the vertebrae of many adult sauropods’ (p. 55). Footprints produced by Sauroposeidon, or by a similar, closely related brachiosaurid are known from the Glen Rose Limestone of the Paluxy River, Texas. At up a metre in diameter, they must have been produced by a real giant, and, among roughly contemporaneous North American sauropods, only Sauroposeidon is big enough (Wedel 2005).

And that’s pretty much the whole story up to now. The main message I suppose you should take away is that producing a technical paper on a specimen – even a short one devoted to the description of a single bone – can be an absurdly drawn-out, lengthy affair literally years in the making, and this is all the more so when other projects and life in general get in the way. Discovered by an enthusiastic amateur who donated the specimen to his local museum (Gavin Leng), prepared by an amateur with scientific training (David Cooper), and eventually described technically by a team of palaeontologists, the MIWG.7306 story is also a nice example of the sort of successful collaboration that can result if people work together.

However, there is also a sad ending to this story. David Cooper, who devoted so much time to the specimen and initiated the research that culminated in the paper, had been suffering for some time from cancer, and by 2005 he knew his condition was terminal. Late in June 2005 I received an unexpected and saddening phonecall. Given that I received this news the day before his funeral, I was unable at such short notice to make the arrangements to attend. This, I regret.

For the latest news on Tetrapod Zoology please go here.

Refs - -

Hutt, S., Naish, D., Martill, D. M., Barker, M. J. & Newbery, P. 2001. A preliminary account of a new tyrannosauroid theropod from the Wessex Formation (Early Cretaceous) of southern England. Cretaceous Research 22, 227-242.

Naish, D., Martill, D. M., Cooper, D. & Stevens, K. A. 2004. Europe’s largest dinosaur? A giant brachiosaurid cervical vertebra from the Wessex Formation (Early Cretaceous) of southern England. Cretaceous Research 25, 787-795.

Radley, J. 1997. Geological report 1993-1994. Proceedings of the Isle of Wight Natural History and Archaeology Society 13, 107-114.

Wedel, M. J. & Cifelli, R.L. 2005. Sauroposeidon: Oklahoma’s native giant. Oklahoma Geology Notes 65, 40-57.

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‘Angloposeidon’, the unreported story, part III

[click for larger version]

This post follows on from the previous two (part I here and part II here). Given that, in June 2002, the MIWG.7306 manuscript had now come back from review, and had fared well during the review process, it was all systems go. But as usual, MIWG.7306 wasn’t the only thing I was working on during 2002. We were also working on the Mirischia project, the Leedsichthys dig at Whittlesey (Leedsichthys was a giant Jurassic filter-feeding fish, equivalent in size to a small whale), the palaeopathology project, and other stuff. So by September of that year, when I attended the 50th SVPCA meeting at the University of Cambridge to gave a talk on MIWG.7306, I still hadn’t resubmitted the post-review version of the manuscript.

For the duration of our work on MIWG.7306, Dave had been corresponding with Kent Stevens, best known for his dinomorph software and for his work on the neck posture of sauropods (his excellent website is here). Dave and Kent had become friends since meeting during the 1998 making of Walking With Dinosaurs, and Kent and I had gotten to know each other at SVPCA 1999, held at Edinburgh (SVPCA = Symposium on Vertebrate Palaeontology and Comparative Anatomy. Website here).

Kent was of course very interested in MIWG.7306, and when I met up with him again at SVPCA 2002, one of the things that he, I and Dave Martill discussed was progress with the MIWG.7306 manuscript. To my mild surprise, Dave suggested during conversation that Kent be made a co-author on the manuscript. Don’t get me wrong: I was of course very pleased to have Kent in on the project, but I think it was a poor decision of Dave’s to bring in another author this late in the day. Doing this would necessitate a major delay, as we'd now have to account for the views and input of another person.

Kent’s contribution was useful of course: not only did he produce an excellent, new-look figure of MIWG.7306, he also just happened to have excellent photos of the cervical vertebrae of the Brachiosaurus brancai specimen HM SII (originally taken by Chris McGowan, whom you’ll know of from my recent ichthyosaur post). Largely for comparative purposes, we included these figures in the final paper, and they occupy an entire glorious page. In between other projects, Kent and I worked to rehaul the manuscript during 2003 and 2004, and regularly sent lengthy emails to one another. Using various measurements taken off the specimen, we argued extensively over which vertebra it might be (viz, which position it occupied in the neck: brachiosaurids had 13 cervical vertebrae), and what the result might then mean for the total length of the whole animal. The latter sort of calculation is essentially speculative, as we don’t know whether proportional neck length was constant across brachiosaurids (Wedel et al. 2000). Long-necked Sauroposeidon, for example, may not necessarily have had a body that was, proportionally, as big for its neck as was that of Brachiosaurus [adjacent image, depicting various Wessex Formation dinosaurs including a giant brachiosaurid, is borrowed from my flickr site].

Anyway, even in June 2004, Kent and I were still talking things through, and we still hadn’t declared closure on the manuscript. We finally did just this on June 14th, and on June 23rd the final, post-review, updated, modified version of the article was finally submitted. Finally, the paper was in press. You might have noted, incidentally, that I keep fairly reasonable track of dates. I’ve been keeping diaries since 1997 or so.

Though based only on two vertebrae, only one of which is any good, there is little doubt that MIWG.7306 and IWCMS : 2003.28 represent the largest dinosaur we know of from Britain, and indeed from Europe. It follows then that Dinosaur Isle – the specimen’s home repository – hoped to get some nice juicy publicity from the publication of the Cretaceous Research paper, and during November 2004 the University of Portsmouth publicity department worked in conjunction with Dinosaur Isle on a planned press release. But here’s the problem: Cretaceous Research releases its papers when they’re still at proof stage, and it releases them as open access on its website (which you can visit here). The proofs arrived at the start of October 2004, and I was alerted to the fact that they were available online on 19th November (a Friday). I immediately contacted Dinosaur Isle to let them know, and only at this stage did we produce a press release. The plan was to hold a press conference or something the following week.

But on the morning of Monday 22th I received a phonecall from Paul Rincon, a science reporter for BBC News. He’d seen the on-line Cretaceous Research proof and wanted to run a story. I asked if he could wait, given that a press conference and official press release was planned, but, oooh no, that’s just not how it works once a story breaks. By 13:40 on that day, the full story, featuring quotes from me and Steve Hutt, was on the BBC News website, and this is where all hell broke loose. The press loved the story, and it was carried in just about every British newspaper, as well as quite a few international ones. I literally spent the entire day on the phone, and I lost track of how many journalists I spoke to. Greg Paul kindly let me use his (now dated) Tendaguru scene depicting a few Brachiosaurus individuals, and this was used all over the place in conjunction with photos of MIWG.7306 (though, as always, many publications produced their own god-awful in-house graphics, or used stock images of sauropods, dated c. 1957).

‘Britain’s biggest dinosaur roamed the Isle of Wight’, proclaimed The Times; ‘Scientists unearth biggest dinosaur to be found in UK’, announced The Scotsman; and ‘Experts bone idle’, explained the Daily Record. The Independent's article (reproduced at top) is one of my favourites for its use of hyperbole, as 'Dinosaur bones on Isle of Wight rewrite evolutionary history' seems, even to me, to be just a little over-enthusiastic.

While the specimen’s size and status proved to be of great interest, also of interest was the fact that the specimen had gone unpublicised for so long. The Daily Record title is a direct reference to this, and their article stated 'Scientists have [sic] not had enough time to look at the bone, found on the Isle of Wight in 1992. Darren said: “There are thousands of fossils waiting to be studied”’. The Daily Mirror quoted me as saying “We just hadn’t got round to studying it”. Even better, after discussing the specimen’s remarkable size, the Daily Telegraph’s Roger Highfield wrote ‘Just as remarkable, the neck bone languished in a box for more than a decade before anyone summoned up enough curiosity to study it, according to one of the team, Darren Naish of the University of Portsmouth’. Err, somehow I don’t think that those were my exact words. I also got on local TV, but I sort of lost out by doing the interviews from my house, rather than from Dinosaur Isle, where the specimen is.

More to come in part IV.

Refs - -

Wedel, M. J., Cifelli, R. L. & Sanders, R. K. 2000. Osteology, paleobiology, and relationships of the sauropod dinosaur Sauroposeidon. Acta Palaeontologica Polonica 45, 343-388.

Friday, July 14, 2006

‘Angloposeidon’, the unreported story, part II

In the previous post I introduced the long, tedious, much-delayed technical project on MIWG.7306, a giant brachiosaurid cervical vertebra from the Isle of Wight. Here we look at more details of this story. You should regard all of this as the back-story to the paper eventually published as Naish et al. 2004 (free pdf available here).

So, by February 2002 we had a provisionally complete, submitted manuscript. Mathew Wedel (well known by 2002 as an expert on giant sauropods) and Paul Upchurch (a sauropod expert specialising on phylogenetic relationships) were chosen as reviewers. Their reviews were back by June 2002, and both were highly positive. Pending minor corrections and additions, this all meant green light to publication.

Looking at it now, I can see that the 2002 version of the manuscript wasn’t too bad, but that it could do with improvement and expansion on a few areas. Little known (and perhaps I should have mentioned this earlier) is that a second vertebra was actually discovered at the same place as MIWG.7306, though it’s substantially less complete and consists only of a poorly preserved centrum 640 mm long (see adjacent photo - and that's Dave in the photo, not me). This second specimen was mentioned in the pre-review version of the manuscript, but not until November 2003 did I obtain its specimen number (IWCMS : 2003.28). You might be wondering why some specimens at Dinosaur Isle are ‘MIWG’ while others are ‘IWCMS’. Essentially, the former accession code was applied prior to the closure of the old Museum of Isle of Wight Geology, while the latter code was applied to specimens accessioned after the 2001 opening of Dinosaur Isle (IWCMS stands for Isle of Wight County Museum Service).

The figures of the 2002 pre-review version of the manuscript were a bit of a mess. Given that we’d now described the anatomy of MIWG.7306 in detail, a major shortcoming was that the figures didn’t point out which bits of the specimen had which names. You really need to do this on sauropod vertebrae, as their anatomy is complex.

In MIWG.7306, three large concavities (termed fossae) occupy most of the lateral surfaces, and these fossae themselves are subdivided into smaller fossae, with some of these subdivisions having further subdivisions. Importantly, the fossae are connected (via openings on their bony walls) to large internal chambers. Bony struts, called laminae, divide the fossae and connect the main ‘landmarks’ of the bone (such as the pre- and postzygapophyses), and each of these laminae has a name. We presently use a system devised by sauropod expert Jeff Wilson, and his paper on this subject is obligatory reading if you want to understand this nomenclature properly (Wilson 1999).

What are all these fossae and laminae for? Perhaps the most remarkable thing about sauropod vertebrae is how pneumatic they were – the lateral fossae, and the interior of the vertebrae, were occupied, in life, by air sacs. That is, by pneumatic sacs that were connected by tubes both to one another, and to the animal’s lungs. How do we know this? Essentially because the detailed anatomy is identical to that of living birds. In birds, bony openings on the sides of the vertebrae also lead into large internal chambers, just as they do in sauropods, and given that the bony openings and internal chambers of bird vertebrae house air sacs, they almost certainly did so in sauropod vertebrae as well. To date no one has proposed a better explanation for the structures seen in sauropods, quite simply because there isn’t one. This has obvious implications for mass, as it means that the animals weighed a lot less than you might otherwise think: Wedel (2005: free pdf here) showed that, by calculating for the presence of air sacs, a sauropod comes out at 8-10% lighter than it would have if its mass were uncorrected. This is actually a conservative estimate, as it doesn’t account for air sacs that would have been distributed among the soft tissues.

Extensive pneumatisation also has implications for various aspects of sauropod palaebiology (Wedel 2003: free pdf here). Don Henderson (2003: free pdf here) has worked out what difference it would make for buoyancy were sauropods to go swimming (which they presumably did at times, even though they weren’t amphibious or otherwise strongly tied to aquatic environments). Pneumaticity also indicates that sauropods enjoyed the relatively high oxygen extraction levels seen in birds, suggests that sauropods were quite capable of efficient heat dumping, and overall is highly suggestive of an elevated metabolism (as is indicated by the amazingly fast growth style now well documented for sauropods: see Erickson et al. 2001, Sander et al. 2004). Biologists today seem to think that they’re being particularly good, sceptical scientists if they outright reject the silly idea of dinosaurian endothermy, but it’s very clear that none of the work that has been done on dinosaur physiology accounts for the amazing degree of pneumatisation seen in sauropods and other groups. There’s an awful lot that could be said on the debate over dinosaur physiology however, and I don’t want to tackle it in depth here.

In its degree of pneumaticity, MIWG.7306 appears intermediate between Brachiosaurus and Sauroposeidon. I worked out that about 60% of each of its lateral surfaces was occupied by the fossae that housed lateral air sacs, and because the specimen is broken in half I could also see that very little of its interior was filled up by internal bony struts: most of it would have been air. The jaw-droppingly amazing thing about the degree of pneumatisation within MIWG.7306 and other brachiosaurids is that their vertebrae consisted of about 80-90% air. Reread that last sentence for emphasis, and you might like to memorise it and trot it out at cocktail parties.

In the previous post we saw how the first published measurement of MIWG.7306 gave its length as 920 mm. Measuring a giant sauropod vertebra isn’t as simple as you might think: firstly, because the long articular processes (the zygapophyses) may be incomplete, secondly, because the zygapophyses might have become bent or distorted during preservation, and, thirdly, because there’s more than one way to gain a vertebra’s ‘total length’! While MIWG.7306 includes a complete, intact left postzygapophysis, its left prezygapophysis is missing, and its right is broken off. Dave Martill and I re-articulated the broken right prezygapophysis and, measuring from its tip to the posterior-most rim of the posterior articular condyle, came up with a new total length of 1060 mm. That’s immense.

In 2002 I was asked to contribute an article on sauropods to an issue of The Quarterley Journal of the Dinosaur Society, and I sent it off in late February. For reasons entirely unrelated to the long delay that beset the MIWG.7306 manuscript, this article was also delayed and wasn’t published until 2005. It included a few paragraphs on MIWG.7306, stated its total length as 1060 mm, and even included a rather fetching photo of me posing with the specimen (Naish 2005). In 2002 I was commissioned to write an article on Isle of Wight dinosaurs for the excellent Japanese magazine Dino Press (now, sadly, defunct). Here again I discussed MIWG.7306, again gave its total length as 1060 mm, and again included a silly photo of me, alongside the specimen (Naish 2002). Amusingly, I’ve just noticed that the latter article states of MIWG.7306 ‘It is due to be published some time in 2002, so look out for it!’ (English text supplement, p. 25).

Alas, the 1060 mm that I gave in those two articles is, while not technically incorrect, not the standardised ‘total length’ of the specimen for, rather than including prezygapophysis length, the standard way of measuring a sauropod vertebra is to stick to centrum length alone. And the centrum length of MIWG.7306 is 745 mm, which is still highly respectable, and on par with some of the longer cervical vertebrae of HM SII (the larger of the two Brachiosaurus brancai specimens described by Janensch). In that specimen, the sixth cervical has a centrum length of 780 mm, while the longest in the series (C10 and C11) each have centrum lengths of 870 mm long. In extra-long Sauroposeidon, C8 has a centrum length of 1250 mm while C6 is 1220 mm. Luckily this oversight was caught long before the MIWG.7306 manuscript was resubmitted.

And that’s not the end of the story: far from it. More to come in the next thrilling instalment (go here).

Refs - -

Erickson, G. M., Curry Rogers, K. & Yerby, S. A. 2001. Dinosaurian growth patterns and rapid avian growth rates. Nature 412, 429-433.

Henderson, D. M. 2003. Tipsy punters: sauropod dinosaur pneumaticity, buoyancy and aquatic habits. Proceedings of the Royal Society of London B (Supp.) 271, S180-S183.

Naish, D. 2002. Thecocoelurians, calamosaurs and Europe’s largest sauropod: the latest on the Isle of Wight’s dinosaurs. Dino Press 7, 85-95.

- . 2005. The sauropod dinosaurs of the Wealden succession (Lower Cretaceous) of southern England. The Quarterly Journal of the Dinosaur Society 4 (3), 8-11.

- ., Martill, D. M., Cooper, D. & Stevens, K. A. 2004. Europe’s largest dinosaur? A giant brachiosaurid cervical vertebra from the Wessex Formation (Early Cretaceous) of southern England. Cretaceous Research 25, 787-795.

Sander, P. M., Klein, N., Buffetaut, E., Cuny, G., Suteethorn, V. & Le Loeuff, J. 2004. Adaptive radiation in sauropod dinosaurs: bone histology indicates rapid evolution of giant body size through acceleration. Organisms, Diversity & Evolution 4, 165-173.

Wedel, M. J. 2003. Vertebral pneumaticity, air sacs, and the physiology of sauropod dinosaurs. Paleobiology 29, 243-255.

- . 2005. Postcranial skeletal pneumaticity in sauropods and its implications for mass estimates. In Wilson, J. A. & Curry Rogers, C. (eds) The Sauropods: Evolution and Paleobiology. University of California Press, Berkeley, pp. 201-228.

Wilson, J. A. 1999. A nomenclature for vertebral laminae in sauropods and other saurischian dinosaurs. Journal of Vertebrate Paleontology 19, 639-653.

Wednesday, July 12, 2006

‘Angloposeidon’, the unreported story, part I

An uncensored big cat kill is screened for the first time on TV, the aquarboreal theory as applied to hominids and sloths becomes personally relevant, and the bizarre social lives of small brown passerines come to dominate my thoughts. Then there are the agamas. But today I want to talk about sauropods, sort of (though be warned: this post has less to do with sauropods, and more to do with the rather dull back-story of one sauropod discovery in particular) [Image used here produced by Mark Witton and nicked from his flickr site].

If Mirischia the Brazilian theropod is one of my little pets, the enormous sauropod represented by the cervical vertebra MIWG.7306 – affectionately (and unofficially) known to some of us as 'Angloposeidon' – is one of the biggest [the image at left, and that below, are my drawings of the specimen]. I don’t specialise on sauropods, but I sometimes collaborate on technical work on these awesome beasts. Mike P. Taylor and I co-authored a paper on the phylogenetic systematics of diplodocoids last year (Taylor & Naish 2005: for the free pdf go here) and we have a few other sauropody projects in the pipeline, and Matt Wedel and I are going to be publishing sauropod stuff some time in the future. It’s a recent sauropod-themed post on Matt’s blog site that’s inspired me to put finger to keyboard on the following. His post is somewhat err, irreverent perhaps, but I still found it inspirational :)

2000 was a really busy year for me, in part because of the huge Dorling Kindersley encyclopaedia I worked on, the Dinosaurs of the Isle of Wight book, my work on the preliminary description of Eotyrannus (Hutt et al. 2001), and the completion of my M.Phil. thesis. And a great deal of time that year was spent, with Dave Martill, running around the Isle of Wight looking at specimens we were planning to include in Dinosaurs of the Isle of Wight. On several occasions we stumbled over unreported specimens that we ‘discovered’ in collections, but in other cases we made specific trips to look at, and photograph, specimens that we’d seen discussed or described in the literature.

Among the latter was an allegedly enormous sauropod vertebra, mentioned on the last page of a booklet entitled ‘The discovery of the island’s largest dinosaur’ and produced by Dinosaur Farm Museum. Written anonymously (but actually penned, I think, by Steve Hutt), the booklet discusses the discovery and excavation of the Barnes High brachiosaurid, a specimen discovered by Steve in 1992 and currently on display at Dinosaur Isle Visitor Centre, Sandown. It’s still owned by Dinosaur Farm Museum: a tourist attraction that lacks official museum credentials, the frustrating consequence being that the Barnes High brachosaurid is still unavailable for technical study. This is maddening as the specimen is easily the most complete European brachiosaurid, and in fact one of the best European sauropods (only little Europasaurus from Germany being better represented). The booklet (which includes no publication data at all and can only be cited as ‘Anon. undated’!) states on p. 7….

Last year an enthusiastic young collector, Gavin Leng, found and gave to the Sandown Museum a single giant neck vertebra which is 920mm (2’6”) long. This was from an adult brachiosaurid which would have had a complete neck 8.8-11 metres (24-30 feet) long and a total length of 26 – 29.6 metres (70 – 80 feet)!

Highly intrigued, in the summer of 2000 I asked around. It turned out that, while the specimen was quite obviously a sauropod cervical vertebra, it had been discovered encased within a hard sideritic matrix, and literally years of careful preparation had been required to prep it out. It had been discovered, in 1992, on the foreshore at Sudmoor Point on the south-west coast of the Isle of Wight. Leng, its discoverer, is well known in the world of Isle of Wight palaeontology for finding a particularly good valdosaur specimen and for discovering Eotyrannus, so he’s a pretty significant guy.

He had handed it over to what was then known as the Museum of Isle of Wight Geology, and from here it had been the pet project of David Cooper, a former pathologist and now amateur palaeontologist, who was working on the specimen at his house. I already knew David from many previous meetings and discussions we’d had about Isle of Wight dinosaurs, and when Dave (Martill) and I visited him during the summer of 2000 the specimen was looking pretty good, with clean bone surfaces almost entirely free of matrix.

We carefully carried it out on to David’s back lawn and photographed it there on the grass, and one of the resulting images was published as Plate 14B in Dinosaurs of the Isle of Wight. David had not just been preparing the specimen, he had also been trying to interpret its morphology and affinities, and we decided then and there that we would collaborate on getting a description into print. It was easily the biggest British dinosaur vertebra I’d ever seen, and I knew that it was about on par with the similarly enormous cervical vertebrae of Brachiosaurus. In its degree of elongation it appeared similar too. I was later to learn that it had an accession number – MIWG.7306 – and I’ll use that from hereon.

Early in 2000 I began corresponding with Mathew Wedel, then of the Sam Noble Oklahoma Museum of Natural History (but today of the University of California Museum of Paleontology). In March 2000 Matt published (with co-authors Richard Cifelli and R. Kent Sanders) his preliminary description of a giant brachiosaurid from the Antlers Formation of Oklahoma, named Sauroposeidon proteles (Wedel et al. 2000a: download the pdf here). Sauroposeidon is known only from its immense cervical vertebrae, two of which are depicted in the adjacent image (provided courtesy of Matt). A fuller description, with tons of new data, was published later in the year in Acta Palaeontologica Polonica (Wedel et al. 2000b: pdf also available - go here).

When Matt and I started corresponding I didn't even know of the existence of MIWG.7306: Matt was contacting me as he was curious as to whether there might be any evidence for giant Sauroposeidon-like brachiosaurids in the British Wealden Supergroup. I was therefore very excited when, one day in the summer of 2000, I was able to tell him about my first viewing of MIWG.7306 at David’s house. David had been comparing MIWG.7306 with Janensch’s figures of Brachiosaurus, and while this was still entirely appropriate, I figured that, because Sauroposeidon was closer in age to MIWG.7306 than was Brachiosaurus, MIWG.7306 might prove to be more like it than was Brachiosaurus.

In between other projects (including papers on Eotyrannus, Aristosuchus and Thecocoelurus), I really got to work on the MIWG.7306 paper during 2001, and visited the specimen several more times. While it was obvious which end was which on MIWG.7306, that’s about all that was obvious. The thing was a complex mess of bony laminae and concavities (termed fossae), few of which were symmetrical when you compared the two sides. Massive ventrolaterally projecting flanges projected from the bottom surface of the specimen: they were highly similar to the hypertrophied centroparapophyseal laminae regarded by Wedel et al. (2000a) as diagnostic for Sauroposeidon. My notes and sketches were a complete mess, as every time I looked at the specimen I ended up reinterpreting my previous identifications.

Dinosaurs of the Isle of Wight was finished during May 2001, and a brief comment on MIWG.7306 was added to the sauropod section (Naish & Martill 2001, p. 212). Copies of the book arrived from the Palaeontological Association (the publishers) on 11th July 2001 (the same day that I attended an [unsuccessful] job interview on the Isle of Wight), and at the time I thought that – excepting that brief mention in ‘Anon. undated’ – this was the first time the specimen had made it into print. How wrong I was – but more on that later.

Completion of the manuscript came slowly, and not until the very end of 2001 was I able to finish the figures. The final manuscript – listing myself, Dave Martill and David Cooper as co-authors – was technically submitted to the chosen journal, Cretaceous Research, in February 2002. Why chose Cretaceous Reseach, when a journal devoted to vertebrate palaeontology might seem like a more obvious choice? The answer is that the BBC series Live from Dinosaur Island was screened in June 2001, and that the production of a special issue of Cretaceous Research – devoted entirely to Isle of Wight palaeontology – had been agreed on as a sort of spin-off of the series. A space within that issue was sort of 'booked' for the MIWG.7306 paper.

For various reasons, that special volume never materialised, and the MIWG.7306 manuscript was shelved for what seemed like an eternity, plus the handling editor (who, I should note, was not anyone on the current editorial staff of Cretaceous Reseach) managed to lose the original figures of the manuscript. Don’t forget that this was in the days before digital submission, so the figures were the original photographs.

And I’ll have to stop there, apologies if you’re bored to tears. Part II will follow next (unless hoardes of blog readers object and insist that I go back to sea snakes). .. it's now available, click here.

Refs - -

Anon. Undated. The discovery of the island’s largest dinosaur. Dinosaur Farm Museum (Brighstone, Isle of Wight).

Hutt, S., Naish, D., Martill, D. M., Barker, M. J. & Newbery, P. 2001. A preliminary account of a new tyrannosauroid theropod from the Wessex Formation (Early Cretaceous) of southern England. Cretaceous Research 22, 227-242.

Naish, D. & Martill, D. M. 2001. Saurischian dinosaurs 1: Sauropods. In Martill, D. M. & Naish, D. (eds) Dinosaurs of the Isle of Wight. The Palaeontological Association (London), pp. 185-241.

Taylor, M. P. & Naish, D. 2005. The phylogenetic taxonomy of Diplodocoidea (Dinosauria: Sauropoda). PaleoBios 25, 1-7.

Wedel, M. P., Cifelli, R. L. & Sanders, R. K. 2000a. Sauroposeidon proteles, a new sauropod from the Early Cretaceous of Oklahoma. Journal of Vertebrate Paleontology 20, 109-114.

- ., Cifelli, R. L. & Sanders, R. K. 2000b. Osteology, paleobiology, and relationships of the sauropod dinosaur Sauroposeidon. Acta Palaeontologica Polonica 45, 343-388.

Saturday, July 08, 2006

The war on parasites: an oviraptorosaur’s eye view

In the previous post we saw how avian bill morphology is crucial to the control of parasites, an assertion that comes from recent studies of bill shape and ectoparasite control in scrub-jays, pigeons and numerous Neotropical bird species. So important is parasite control in a bird’s overall fitness that preening might be one of the most important functions of the bill and, accordingly, adaptive radiations of beak morphology should be re-assessed with both feeding and preening in mind.

The several studies that have looked at bird bills and their function in preening only considered what implications there might be for living birds. But as a palaeontologist I’m going to do the logical thing and wonder what this might mean for fossil feathered taxa. I’ll note now that the previous post is essential reading before you embark. Ok, here we go.

Fossil birds belonging to the same groups as extant species, surely, used their bills in the same manner as extant species, so dodos, teratorns and presbyornithids almost certainly found their bills to be as essential for preening as do modern pigeons, raptors and ducks. But of course we know that feathers weren’t unique to ‘modern-type’ birds: they were also present in the basal birds of the Mesozoic (going all the way back to the archaeopterygids, and including a diverse aviary of yandangornithids, confuciusornithids, enantiornitheans, hesperornitheans and others) AND they were also present in non-avian maniraptoran theropods. We know that true feathers were present in oviraptorosaurs, microraptorians (which might be part of Dromaeosauridae: it depends on the phylogeny) and almost certainly troodontids (Jinfengopteryx, a luxuriantly feathered little theropod described last year as an archaeopterygid, is almost certainly a troodontid). Furthermore, probable ‘proto-feathers’ (rather simple quill-like integumentary structures, almost certainly the morphological ancestors of true, complex feathers) were present in compsognathids, basal tyrannosauroids and alvarezsaurids.

We also know that ectoparasites were infesting feathers by the Cretaceous at least. How do we know this? Martill & Davis (1998, 2001) described an isolated feather from the Lower Cretaceous Crato Formation of Brazil that is covered in more than 240 hollow spheres that are almost certainly feather mite eggs. We also know that fleas were present in the Lower Cretaceous as there are two particularly good ones known from Australia (Riek 1970), and we also know of possible fleas and odd long-legged possibly parasitic insects from the Lower Cretaceous of the former USSR (Ponomarenko 1976). Terrestrial birds whose plumage is superficially similar to that of fuzzy small theropods are notorious for harbouring ectoparasites, with kiwis in particular being reported to crawl with numerous fleas, ticks, feather mites and lice (Kleinpaste 1991). So I would be confident that Mesozoic birds, and fuzzy and feathered non-avian theropods, had to contend with ectoparasites. What then did they do about parasite control?

Unfortunately we don’t know enough about the rhamphothecae of Mesozoic birds and bird-like maniraptorans to determine whether or not they had a maxillary overhang: the preservation simply isn’t good enough. But maybe some of these animals didn’t need a maxillary overhang given that many of them had teeth. Indeed several Mesozoic maniraptorans possess just a few teeth at the jaw tips, or even just in the upper jaw tips.

Take the feathered turkey-sized short-skulled basal oviraptorosaurs Protarchaeopteryx* and Caudipteryx (if you’ve heard that these animals aren’t oviraptorosaurs but actually flightless birds, ignore it: it’s a theory based on wishful thinking and misinterpretation of morphological evidence). In Protarchaeopteryx, teeth are restricted to the premaxillae and anterior parts of the maxillae and dentaries, with the premaxillary teeth being a few times taller than the others (Ji et al. 1998). In Caudipteryx, four procumbent teeth are present in each premaxilla, but the rest of the skull is edentulous. Incisivosaurus – closely related to, and possibly congeneric with, Protarchaeopteryx – has a reduced compliment of teeth, all of which are restricted to the anterior parts of the jaws, and two enlarged, bunny-like incisiform teeth project from each premaxilla (image at top: widely available on the web). More derived oviraptorosaurs were toothless, but the bony premaxillary margins of their upper jaw were serrated, raising the possibility that the tomium was serrated too. Could these serrations have been used in ectoparasite control? (incidentally, for more on oviraptorosaurs go to Luis Rey and the new oviraptorosaur panoply).

* Not a typo! I’ve lost count of how many times I’ve seen this name ‘corrected’ by well-meaning editors.

Among other non-avian feathered maniraptorans, it’s worth noting that microraptorians also exhibit an unusual premaxillary dentition. In Sinornithosaurus, a diastema separates the premaxillary teeth from the maxillary teeth, and the premaxillary teeth appear notably shorter than the maxillary ones (Xu & Wu 2001). While proportionally small premaxillary teeth are seen elsewhere in theropods (e.g., in tyrannosauroids), the combination of reduced dentition and diastema isn’t, and we know without question that microraptorians had complex, vaned feathers on their limbs and tails. It’s at least suggestive that the premaxillary teeth were used for preening.

Having mentioned tyrannosauroids, I might also note that basal forms combine proportionally small premaxillary teeth with quill-like integumentary structures that would have needed preening (or is grooming the correct term here?). Could those little premaxillary teeth have been specialized for ectoparasite control? I know this is grotesque speculation of the worst kind, but read on.

Basal tyrannosauroids and other basal coelurosaurs that possess specialised premaxillary teeth that might have been used in preening/grooming of quill-like integumentary structures. A, Proceratosaurus; B, Guanlong; C, Ornitholestes; D, Dilong. This excellent image is taken from Frederik Spindler & Peter Tschernay’s Dinosauromorpha site.

Moving now to Mesozoic birds, given that there was a trend in some lineages toward reduction and loss of teeth, it follows that members of these lineages exhibit reduced numbers of teeth relative to archaeopterygids and non-avian theropods. It seems that these birds lost the teeth from the back of the jaws first, and kept their premaxillary and dentary-tip teeth the longest. Even in forms that don’t have a reduced dentition however, we see slight heterodonty, and thus some suggestion that the anterior-most teeth were being used for something special. In archaeopterygids for example, the premaxillary teeth are more peg-like and more procumbent than are the other teeth. Aberratiodontus - an odd enantiornithean from the Chinese Jiufutang Formation - has teeth lining both its upper and lower jaws, but is reported to have rather small teeth at the jaw tips (Gong et al. 2004).

When we start looking at some of the more unusual Mesozoic birds groups, we see marked specialisation of the rostral-most dentition. Bizarre long-tailed, robust-jawed Jeholornis (almost certainly synonymous with Shenzhouraptor, and perhaps with Jixiangornis too), known from stomach contents to have eaten seeds at least occasionally, has just three very small teeth at each lower jaw tip (Zhou & Zhang 2002): the upper jaw was edentulous.

The unusual long-armed Sapeornis, also from the Jiufutang Formation, had a rather short, Caudipteryx-like skull, and short, conical, unserrated, procumbent teeth projected from its premaxillae (Zhou & Zhang 2003). Its dentaries were toothless (and its maxillae probably were too). The somewhat similar Omnivoropteryx, also from the Jiufutang Formation, was also short-skulled, and also has just a few procumbent teeth restricted to the premaxillae (Czerkas & Ji 2002).

Most (but not all) enantiornitheans were toothed, and ancestrally they had teeth lining their upper and lower jaws as archaeopterygids did. But in the Yixian Formation enantiornithean Protopteryx (image at left: taken from there are just two conical, unserrated teeth in the premaxillae and two subtriangular teeth at the dentary tips (Zhang & Zhou 2000). It doesn’t seem that having a total of four teeth is a tremendously useful thing if you need those teeth to procure or dismember your food, and it’s intriguing that Protopteryx sports highly elongate, strap-like rectrices that would (presumably) have needed careful preening. The euenantiornithean Eoenantiornis has four subconical teeth in each premaxilla while there were probably six or seven teeth in each dentary, the rostral-most two of which were larger than the others (Zhou et al. 2005). Long-skulled Longirostravis has ten small, conical teeth restricted entirely to its slim jaw tips (Hou et al. 2004) and short, conical teeth are similarly only at the jaw tips in another long-skulled enantiornithean, Longipteryx (Zhang et al. 2001). And there are yet other examples of this sort of thing.

So far as I can see from all these unusual patterns of dentition, there are three possible explanations:-
(1) as dental reduction occured, a gradual step-wise loss of teeth simply meant that premaxillary and/or dentary-tip teeth were the last to go;
(2) premaxillary and/or dentary-tip teeth were retained in specialized taxa that used those teeth to procure or dismember whatever it was that they were eating;
(3) premaxillary and/or dentary-tip teeth were retained - even when not essential to foraging or feeding - as they were used in ectoparasite control.

While it’s nice to speculate – and so far that’s all I’ve done here – how might we test the idea that these Mesozoic taxa were using their unusual rostral teeth to preen with? Herein lies the rub, as I can't think of a reliable test. So far as we know, feathers aren’t abrasive enough to leave any sort of distinctive microwear on teeth, or even on rhamphothecae, so there isn’t going to be any sort of tooth wear that can be correlated with preening. It’s possible that there might be some sort of correlation between tooth spacing and feather morphology, but I find this unlikely.

Conversely, we can test the idea that teeth were used in feeding, as feeding does leave visible sorts of micro- or macrowear. Earlier I mentioned the bunny-like teeth of Incisivosaurus, and because its incisiform teeth do exhibit wear facets, they were almost certainly used in feeding. This confirms ‘explanation 2’ given above, and therefore indicates that ‘explanation 3’ didn’t apply in this case. But the two ‘explanations’ aren’t mutually exclusive, as the teeth could still have been important in ectoparasite control.

Those short premaxillary teeth present in tyrannosauroids have conventionally been regarded as having a primary role in feeding, and it might be easy to confirm this by looking for micro- or macrowear. And yes, I consider it highly highly speculative to wonder if those teeth might have functioned in grooming/preening, but I couldn’t resist mentioning it (I want to discuss here the SEM data I have on the premaxillary teeth of the basal tyrannosauroid Eotyrannus, but that would require adding too many extra words).

Finally, if specialised teeth could be shown to have no important function in foraging or feeding behaviour it might then be logical to infer that preening was their primary function - - but, how on earth would you show that they had ‘no function’ in foraging or feeding behaviour? This just isn’t possible in Mesozoic animals when so little is known of their ecology. An analogy does come to mind: it’s been shown that the unusual dentary teeth of Impala Aepyceros melampus have a morphology specialised for a primary function in grooming. If impalas were extinct I suppose it’s possible that people might have worked this out, but how would you verify it?

Does anyone have any better ideas?

I’m far from the first person to look at Mesozoic feathered theropods this way – many other people have mentioned these ideas before, and artists have even illustrated ectoparasite control in dinosaurs. In Dinosaurs of the Air Greg Paul illustrated a Sinosauropteryx scratching in order to remove ectoparasites, and the cover of The Dinosauria, Second Edition (the current industry-standard volume on dinosaurs) features a Sinosauropteryx (this time by Mark Hallett) nibbling at its proto-feathers, again presumably as a form of ectoparasite control.

But I don’t think anyone’s really married data on Mesozoic birds and other theropods with the new work of Dale Clayton and colleagues on ectoparasite control in extant birds. Maybe this idea will bear proverbial fruit down the line, but for now this is where my contribution ends.

Finally, here’s another spin on this subject. Theropods weren’t the only Mesozoic tetrapods with a furry coat of integumentary fibres: we also know that pterosaurs were fuzzy too. So did they also have to contend with ectoparasites? I’ll say no more on this topic, but perhaps it can be elaborated on at another time. For the latest news on Tetrapod Zoology do go here.

Refs - -

Czerkas, S. A. & Ji, Q. 2002. A preliminary report on an omnivorous volant bird from northeast China. In Czerkas, S. J. (ed) Feathered Dinosaurs and the Origin of Flight. The Dinosaur Museum (Blanding, Utah), pp. 127-135.

Gong, E., Hou, L. & Wang, L. 2004. Enantiornithine bird with diapsidian skull and its dental development in the Early Cretaceous in Liaoning, China. Acta Geologica Sinica 78, 1-7.

Hou, L., Chiappe, L. M., Zhang, F. & Chuong, C.-M. 2004. New Early Cretaceous fossil from China documents a novel trophic specialization for Mesozoic birds. Naturwissenschaften 91, 22-25.

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