The Tet Zoo field guide to ostrich dinosaurs (part I)

As events conspire, I again find myself unable to devote time to completing any new blog posts. That's a shame, as I'm desperate to finish and publish my article on the terrifying sex organs of male turtles (yes really: stay tuned). In desperation, I've opted to dig out and recycle some old text. If you like dinosaurs, you might be pleased...

We've seen before that - perhaps more than most scientist-authors - I've lost/wasted an unbelievable amount of time on projects that ultimately failed, or have yet to come to fruition. There was the taphonomy book, and there are a long string of academic projects that I try not to talk about for fear of internal haemorrhaging. Among the list of the lost is, believe it or not, a field guide to dinosaurs. Yes, a field guide to all of the Mesozoic's dinosaurs. Familiar story: months and months of work, tons of research, stacks of writing, loads and loads and loads of to-ing and fro-ing with the publishers.... and, ultimately, explosion on the launch pad. So, what the hell, why not recycle some of the text I produced. Entirely at random, I've decided to reproduce the ornithomimosaur text, and here it is. It's nothing more than a genus-by-genus popular-level review (taxa arranged in rough phylogenetic sequence), with no long intro on phylogenetic position, palaeobiology or biogeography. It might, or might not, be useful. Because it was written for a popular book, the original text didn't include any references. I've therefore shoved a few in, but have not cited all of the literature I consulted. Also, the text was written in 2004 and thus does not necessarily incorporate everything from the last three years (e.g., Kobayashi & Barsbold 2005a, b, 2006). I leave in peace.

Pelecanimimus polyodon was described in 1994 by Bernandino Pérez-Moreno and colleagues from Spanish rocks of the Hauterivian-Barremian Calizas de La Huérguina Formation (Pérez-Moreno et al. 1994, 1999). It changed the idea that ornithomimosaurs were unique to Asia and North America. Pelecanimimus was like the more derived ornithomimid ornithomimosaurs in that all three fingers were nearly equal in length, forming a hook-like hand, but its skull, however, was most certainly not like that of ornithomimids. Its snout was long and shallow, and lining its jaws were an incredible 220 or so unserrated teeth, more than in any other dinosaur. This explains the species name, which means 'many teeth'. These teeth were not all identical: those at the front of the upper jaw were D-shaped in cross-section while those near the back of the upper jaw were more blade-like than the lower jaw teeth. Skin impressions show that Pelecanimimus had a vaguely pelican-like throat pouch (this is why its generic name means 'pelican mimic') and it appears to have had a soft-tissue head crest of some kind. Pelecanimimus had a total length of 2-2.5 m [adjacent skull reconstruction of Pelecanimimus, by Ville Sinkkonen, from here. Life restoration at top from here. It's excellent, but the animal should be decked out with integumentary fibres of some sort (go here for more on that)].

Members of most major coelurosaurian groups are now known from the famous Lower Cretaceous Yixian Formation of Liaoning Province, China. Shenzhousaurus orientalis, described and named by Qiang Ji and colleagues in 2003, is the first Yixian Formation ornithomimosaur (Ji et al. 2003). Like most other Yixian Formation coelurosaurs, Shenzhousaurus was a small and primitive member of its group. The incomplete type specimen represents a near-adult animal that would have been less than 1.5 m long. The skull of Shenzhousaurus was long and shallow-snouted and, as in other basal ornithomimosaurs, conical, unserrated teeth were present. However, unlike all other ornithomimosaurs except Harpymimus, only lower jaw teeth were present and these were restricted entirely to the jaw tips. The hands of Shenzhousaurus were primitive compared to those of most other ornithomimosaurs because its thumbs were shorter than its other digits. In most other ornithomimosaurs the three hand digits were nearly equal in length because the thumb was especially elongate. Shenzhousaurus has gastroliths preserved in its gut region, indicating that it was a herbivore. Herbivory therefore seems to have evolved in ornithomimosaurs among primitive, toothed forms, and not just in the toothless ornithomimids [adjacent image of Shenzhousaurus from here].

Harpymimus okladnikovi, named in 1984 by Rinchen Barsbold and Altangerel Perle after the harpies of Greek mythology, was a basal Mongolian ornithomimosaur from the Albian Shinehuduk Formation. The only known specimen was discovered in 1981 by members of the Soviet-Mongolian Palaeontological Expedition. Harpymimus is like Shenzhousaurus in exhibiting primitive features that were lost or modified by more derived ornithomimosaurs. In the skull, both genera have conical teeth restricted only to the tips of the lower jaws and, in the forelimbs, both genera have thumbs which are notably shorter than the second and third fingers. The feet of Harpymimus are primitive in that the third metatarsal was not compressed in its upper half, as it was in ornithomimids, and in that a hallux was still present. Harpymimus had 10-11 teeth in each dentary, more than were present in Shenzhousaurus. Its lower jaw has been illustrated as being strongly down-curved but it now seems that this was inaccurate. Like some ornithomimids and unlike Shenzhousaurus, Harpymimus had a protruding 'chin' on the underside of the lower jaw. Its specific name honours the scientist A. P. Okladnikov. The total length of Harpymimus has been estimated at 3.6 m [image of Harpymimus holotype from here].

The first ornithomimosaur to be discovered that wasn't a member of Ornithomimidae, Garudimimus brevipes is from the Cenomanian-Turonian Bayanshiree Formation of Mongolia. Its remains indicate a total length of about 4 m and include a well preserved skull as well as bones from the feet. Unlike more basal ornithomimosaurs but like ornithomimids, Garudimimus was toothless. The tip of its upper jaw seems to have been blunter than that of most other ornithomimosaurs. There have long been claims that Garudimimus possessed a horn of some kind, either a backward-pointing spike on its forehead or a nasal horn, but both claims are incorrect and Garudimimus was in fact hornless. As is suggested by its specific name (meaning 'short foot'), Garudimimus had proportionally shorter, broader feet than ornithomimids. It also still possessed a hallux. When Rinchen Barsbold named Garudimimus in 1981 he regarded it as distinct enough for its own family, Garudimimidae. Today Garudimimus is regarded as a basal ornithomimosaur closer to Ornithomimidae than are Pelecanimimus, Shenzhousaurus and Harpymimus (Makovicky et al. 2004). Its generic name, meaning 'Garuda mimic', is a reference to Garuda, the king of the birds from Hindu mythology [adjacent image of Garudimimus skull from here].

More next...

Refs - -

Ji, Q., Norell, M. A., Makovicky, P. J., Gao, K.-Q., Ji, S.-A. & Yuan, C. 2003. An early ostrich dinosaur and implications for ornithomimosaur phylogeny. American Museum Novitates 3420, 1-19.

Kobayashi, Y. & Barsbold, R. 2005a. Reexamination of a primitive ornithomimosaur Garudimimus brevipes Barsbold, 1981 (Dinosauria: Theropoda), from the Late Cretaceous of Mongolia. Canadian Journal of Earth Sciences 42, 1501-1521.

- . & Barsbold, R. 2005b. Anatomy of Harpymimus okladnikovi Barsbold and Perle 1984 (Dinosauria: Theropoda) of Mongolia. In Carpenter, K. (ed) The Carnivorous Dinosaurs. Indiana University Press, Bloomington and Indianapolis, pp. 97-126.

- . & Barsbold, R. 2006. Ornithomimids from the Nemegt Formation of Mongolia. Journal of the Paleontological Society of Korea 22, 195-207.

Makovicky, P. J., Kobayashi, Y. & Currie, P. J. 2004. Ornithomimosauria. In Weishampel, D. B., Dodson, P. & Osmólska, H. (eds) The Dinosauria, Second Edition. University of California Press (Berkeley), pp. 137-150.

Pérez-Moreno, B. P. & Sanz, J. L. 1999. Theropod breathing mechanism: the osteological evidence. In Renesto, S. (ed) Third International Symposium on Lithographic Limestones (Bergamo, Italy). Revista del Museo Civico di Scienze Naturali 'Enrico Caffi' (Bergamo), Supplement to no. 20, pp. 121-122.

- ., Sanz, J. L., Buscalioni, A. D., Moratalla, J. J., Ortega, F. & Rasskin-Gutman, D. 1994. A unique multitoothed ornithomimosaur dinosaur from the Lower Cretaceous of Spain. Nature 370, 363-367.