Wednesday, November 13, 2013

New Apatosaurus ajax remains from Lakes Quarry, Colorado

An interesting article from Huffington Post:

Apatosaurus Snout Bone, Missing Piece Of Long-Neck Dinosaur, Finally Discovered

A small roadside quarry west of Denver, site of some of the infamous "Bone Wars" of the 19th century, has revealed a new treasure: the snout of the long-necked dinosaur Apatosaurus ajax.

The specimen, nicknamed Kevin, is the first Apatosaurus ajax muzzle ever found, and the discovery is likely to help paleontologists un

derstand how A. ajax is related to other Apatosaurus kin, said Matthew Mossbrucker, the director of the Morrison Natural History Museum in Morrison, Colo., and the paleontologist who first identified the bones.

While a skull of Apatosaurus louisae from Dinosaur National Monument in Utah (CM 11162) has become the basis for most restorations of the head of Apatosaurus, it should be noted the type specimen of Apatosaurus ajax (YPM 1860) includes some cranial remains, as does another A. ajax specimen, YPM 1840 (type of Atlantosaurus immanis). Moreover, a skull of Apatosaurus ajax found in situ with the neck vertebrae (CMC VP 7180) provides more info on the cranial anatomy of this species (Barrett et. al. 2011).

The article then states:

Teeth found in Quarry 5 by Lakes were declared by Marsh in 1884 to belong to Diplodocus lacustris, another long-neck species. But those teeth, now held in Yale's collections, look just like Kevin's. In other words, Diplodocus lacustris didn't exist — instead, Lakes found part of Kevin and missed the rest.

If the type specimen of Diplodocus lacustris is the same individual as the snout found by Matthew Mossbrucker, then YPM 1922 would become the fourth known specimen of Apatosaurus ajax that includes cranial remains. Not a bad idea.

Barrett, P. M., G. W. Storrs, M. T. Young, and L. M. Witmer. 2011. A new skull of Apatosaurus and its taxonomic and palaeobiological implications. Annual Symposium of Vertebrate Palaeontology and Comparative Anatomy, Lyme Regis, UK.


Update: The cladistic analysis by Tschopp et al. (2015) fails to recover Atlantosaurus immanis as sister to Apatosaurus ajax to the exclusion of other apatosaurine diplodocids, but it confirms that the braincase labeled YPM 1860 and considered by McIntosh (1995) to be from the same individual as YPM 1840 is apparently from the holotype of A. ajax. Moreover, Tschopp et al. throw cold water on the possibility that the Lakes Quarry 5 apatosaurine premaxilla and maxilla could be from the same individual as Diplodocus lacustris. Until the specimen discussed in the Huffington Post article is described in more detail, YPM 1860 and CMC VP 7180 should be considered the only Apatosaurus ajax specimens that include cranial material.

Tuesday, November 12, 2013

About the author

Hello all,

My name is Vahe Demirjian and I have been a freelance expert in Mesozoic animals for over 10 years. With universal recognition that birds are not a group separate from reptiles but instead a group of theropod dinosaurs closely aligned with the raptor dinosaurs of Jurassic Park fame, I now tend to view dinosaurs not as terrifying animals but instead one of the surviving groups of Mesozoic animals (just as mammals are merely living derivatives of extinct reptiles like Dimetrodon), having come in a huge variety of shapes, size, habitats, adaptations, et cetera.

I first learned about the names of many extinct dinosaurs when I bought a copy of the book Scholastic Dinosaurs A to Z and my grandpa gave me a copy of David Lambert's book Field Guide to Dinosaurs. The purpose of my blog, however, is to comment on the sauropod dinosaurs, with respect to their taxonomy, biogeography, biology, and discovery. I hope this blog will provide interesting never-before-heard facts about the largest group of extinct dinosaurs that ever lived.