E.S.C.O.N.I.

Disney’s "DINOSAUR"

So have you seen this movie yet? I have and I did enjoy seeing the depiction of the dinosaurs and what their world may have been like. Of course, there are elements that the paleontologists do not like; lemurs did not live 65 MYA, and it is not likely that there would be a Brachiasuarus around then either. However, this is Disney and it is fiction. But the computer depiction of the beasts seems quite good. Another factor is that they chose to use a Carnotaurus instead of a T rex as its carnivore. The Carnotaurus does have an interesting look with his eye horns, but may not have lived at the same time either. There is only one skeleton that has been found. It is almost complete, is from Argentina, and is dated at about 100 MYA. It is somewhat less fierce in that it is more lightly built and has a smaller, shorter and taller skull than the T rex. The skull is 22 inches long (compared to SUE at 62 inches long). It has the same very small forearms but has four fingers instead of the T rex two fingers. Another exciting find was several parts of skin impression that showed that it had a pattern of small semiconical protuberances in rows about 10 cm apart. It is likely that the skin design and the eye horns attracted Disney to this animal.

Recent articles in Geology and Paleobiology by Carrier and Farmer titled "The Integration of Ventilation and Locomotion in Archosaurs" present the results of an interesting study. They have concluded that the pelvic structure contributes to lung ventilation in crocodiles and birds. Lizards can not breath and walk at the same time, but alligators can. Their theory makes use of the gastralia of theropods which have been difined as dermal ossifications in the belly wall. These structures have not been found in ornithischians and probably not in sauropods. They consist of from 14 to 21 forward pointing, V shaped segments that are rod like. Their proposal involves the use of a muscle attached to the ischium running to the middle of the gastralia while stretched under the pubic foot. This muscle would increase the volume of the body cavity during inspiration. This may have been important in non-avian theropods whose gastralia form a crisscross pattern at the joints down the middle. In addition to this interlocking formation there are also muscle and ligament scars on the gastralia that indicate that they were being actively used. The elongated pubes and boot would help to orient the force of the muscle to pull the gastralia down as well as back. As a theropod walked, it would breath out as it started a step and breath in as it finished the step. The front of the trunk and the tail would sag down around the pelvis and rebound when breathing in. Birds have a breathing pattern opposite to that of the dinosaurs. There are four reasons for this change; birds have great reduction in the mass and length of tail, birds have a backward rotation of the pubes, birds lose gastralia, and birds have enlarged flight muscles and sternum causing an increase in thoracic volume.

On the other hand, ornithischian dinosaurs lost gastralia as an aid to breathing. This may have been because of the large herbivorous gut that had to be lifted. They also had a completely different hip structure. Other animals discussed in the article were pterosaurs and bats. The fossil evidence and living animals show that they had different systems. These articles are long and detailed so I can not do them justice here. However, they do appear to be logical and sound theories based on both fossil and extant structures. It will be interesting to see how they are accepted by the paleontological community.

Greg Buckley of Roosevelt University and Chris Brochu of the Field Museum have recently reported on an exciting new crocodile find from Madagascar. The skull is very different from the long pointed snout of other crocodiles and its teeth indicate that it was a plant eater. It lived about 70 MYA along with six other species of meat-eating crocs. It may have turned to herbivory so that it was not competing for the meat that the others ate. The pug nosed croc has been named Simosuchus clarki and will be on temporary display at the Field Museum beginning in mid July (in the Life Over Time exhibit). It is about three feet long and may have burrowed in dry land instead of living in the swamps like its cohorts. It has some similarities with other species that were found in Uraguay in South America. This reinforces the tectonic position of South America joined with Africa and Antarctica. The animals then evolved differently after these land masses separated. The rounded nose may have meant that is was a burrower rather than a swamp dweller like the other crocs. It has some features that are somewhat like those of some of the ornithischian dinosaurs like ankylosaurs.

There is some more excitement in the dino-bird controversy. An old specimen of longisquama is being restudied to determine if it could have had the earliest feathers when it lived 225 MYA. The specimen was found in central Asia in 1969 and has been sitting in a drawer in Moscow. Longisquama is thought to be an archosaur which is an ancestor of dinosaurs, crocodiles and birds. Archaeopteryx did not show up until about 145 MYA and is recognized as the first known bird. Not all paleontologists agree with the theory by John Rubens and Terry Jones (reported in Science), because it is a poor specimen. But it will probably stir things up a little for a while. It seems to me that since feathers have been found on dinosaurs now, they can no longer be considered an exclusive characteristic of birds. Feathers may have evolved several times on different animals at different times for different purposes. So this specimen, even if proves to be valid, would not discount the dino-bird theory. There are many many other characteristics upon which that theory is based. I expect that there will be much more discussion of this "find".

The June issue of the Journal of Vertebrate Paleontology has just arrived and there are three dinosaur items in it.

The first is by Catherine Forster et al and reports of a new coelurosaur from the Early Cretaceous of South Africa. 70% of the articulated skeleton named Nqwebasaurus thwazi (pronounced n-KWE-bah saurus TWAH-zee, for the region and "fast runner"). The bones found include skull fragments, shoulder girdle and forelimb, 7 neck vertebrae, hind limb, and gastralia. Also found were gastroliths which are rare with theropods. The prescence of this animal here reinforces the belief that coelurosaurs were global early in their evolution.

Robert Sullivan and Spencer Lucas report an extension of the supposed "sauropod hiatus" in North America from 97 to 60 MYA. During that time period it was believed that there were no sauropods around. Some sparse fossils now being studied may mean that there were back in North America as soon as about70 MYA. It is likely that they migrated here from South America or Asia. The tooth and 3 vertebrae pieces are of the titanosaur Alamosaurus and they were found in New Mexico.

Ronan Allain and Philippe Taquet reported on a new dromaeosaurid from the Upper Cretaceous in southeastern France. They call it Pyroraptor olympius ( "fire thief" from Mt. Olympe, found after a forest fire). Dromaeosaurids are rare in Europe. The bones found include a couple teeth, foot claws, ulna and radius, and some vertebrae. The dromaeosaurid origins is uncertain because finds have been made in North American (Utahraptor) and now in China as well.

      Karen Nordquist, ESCONI Paleontology Study Group

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