Saturday, August 17, 2013

New Multituberculate fossil shows keys to their success

Reconstruction of Rugosodon eurasiaticus.
Multituberculates are a highly successful group of early mammals and they were surprisingly long lived having evolved in the Jurassic, survived the KT extinction event before disappearing during the Oligocene period. They are in fact the most long-lasting group of mammals, having survived at least 130 million years, more than any other group of mammals either alive or extinct. A new mostly complete fossil discovered in China, Rugosodon eurasiaticus, greatly help clarify the origin of the group. It shows that some of the key characteristics of the multituberculates, such as highly flexible spine and mobile ankle joints, evolved very early, and were probable the reasons of their success.


Ref: Yuan C.-X., Ji Q., Meng Q.-J., Tabrum A. R., Luo Z.-X. 2013. Earliest evolution of multituberculate mammals revealed by a new Jurassic fossil. Science 341 (6147): 779–783

Abstract: Multituberculates were successful herbivorous mammals and were more diverse and numerically abundant than any other mammal groups in Mesozoic ecosystems. The clade also developed diverse locomotor adaptations in the Cretaceous and Paleogene. We report a new fossil skeleton from the Late Jurassic of China that belongs to the basalmost multituberculate family. Dental features of this new Jurassic multituberculate show omnivorous adaptation, and its well-preserved skeleton sheds light on ancestral skeletal features of all multituberculates, especially the highly mobile joints of the ankle, crucial for later evolutionary success of multituberculates in the Cretaceous and Paleogene. 

Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission (Email: nobu dot tamura at yahoo dot com). Check out my portfolio at

Thursday, August 15, 2013

And then there were nine...

The top right species is now synonymous with the top left one.

Up to 15 species of Psittacosaurus have been described in the scientific litterature, but a few are dubious and others have been shown to be synonymous. With the latest 3D geometric morphometric study of the skulls of the three species of Psittacosaurids from the Lujiatun beds of the Yixian Formation of China, this number is now down to nine: Hongshanosaurus houi and Psittacosaurus major are now taxonomically dead...

Psittacosaurus lujiatunensis

Here is the paper and abstract:
Hedrick BP, Dodson P (2013) Lujiatun Psittacosaurids: Understanding Individual and Taphonomic Variation Using 3D Geometric Morphometrics. PLoS ONE 8(8): e69265.


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.

Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission (Email: nobu dot tamura at yahoo dot com). Check out my portfolio at