psittacosaurids

10

Carnegie Museum - Part 3

The first thing to greet one’s arrival to the Cretaceous hall is one of the famous quilled specimens of Psittacosaurus. Across the way are some other Jehol Biota animals, complete with models (like this Sinornithosaurus). They look fairly well, so far as museum models of feathered dinosaurs go—that is to say, they don’t look quite like naked dinosaurs with feathers just glued on. Beside the models are a couple specimens, including this Caudipteryx with feathers and its last meal, preserved in its stomach.

A step ahead is Protoceratops, doing what it does best, whatever that may be, and across from that, Corythosaurus. Just ahead are the heavy-hitters of the Cretaceous exhibit, a pair of Tyrannosaurus rex feuding over a corpse. It’s that of Edmontosaurus, being snarled over by tyrannosaurs because this is all edmontosaurs ever did.

Just around the corner is a rare site in most dinosaur halls, a mounted Pachycephalosaurus at full charge. Next to him are a rogue’s gallery of his marginocephalian buddies, the ceratopsians. From the left clockwise, they're Pachyrhinosaurus, Zuniceratops, Diabloceratops, and Torosaurus. Their more famous cousin, Triceratops, stands a bit further down.

Last on the way out of the dinosaur hall is the recently-named caenagnathid Anzu wileyi. The fossil was discovered 15 years ago, and the holotype at this point was presumably sitting just under my feet. Spooky.

Past here, some Cenozoic skeletons and another photoset.

plosone.org
PLOS ONE: Lujiatun Psittacosaurids: Understanding Individual and Taphonomic Variation Using 3D Geometric Morphometrics

Psittacosaurus is one of the most abundant and speciose genera in the Dinosauria, with fifteen named species. The genus is geographically and temporally widespread with large sample sizes of several of the nominal species allowing detailed analysis of intra- and interspecific variation. We present a reanalysis of three separate, coeval species within the Psittacosauridae; P. lujiatunensis, P. major, and Hongshanosaurus houi from the Lujiatun beds of the Yixian Formation, northeastern China, using three-dimensional geometric morphometrics on a sample set of thirty skulls in combination with a reevaluation of the proposed character states for each species. Using these complementary methods, we show that individual and taphonomic variation are the joint causes of a large range of variation among the skulls when they are plotted in a morphospace. Our results demonstrate that there is only one species of Psittacosaurus within the Lujiatun beds and that the three nominal species represent different taphomorphotypes of P. lujiatunensis. The wide range of geometric morphometric variation in a single species of Psittacosaurus implies that the range of variation found in other dinosaurian groups may also be related to taphonomic distortion rather than interspecific variation. As the morphospace is driven primarily by variation resulting from taphonomic distortion, this study demonstrates that the geometric morphometric approach can only be used with great caution to delineate interspecific variation in Psittacosaurus and likely other dinosaur groups without a complementary evaluation of character states. This study presents the first application of 3D geometric morphometrics to the dinosaurian morphospace and the first attempt to quantify taphonomic variation in dinosaur skulls.