James M. Clark

My research addresses the interpretation of fossil land vertebrates (tetrapods), especially those from fossil deposits of the Age of Dinosaurs (the Mesozoic). My field work includes participation in the American Museum of Natural History-Mongolian Academy of Sciences expeditions to the Gobi Desert of Mongolia from 1991 to 2002 (at times as co-field leader), and extensive work in Mexico. My current NSF-funded field project is an exploration of the Middle to Late Jurassic Shishugou Formation of Xinjiang, China, in collaboration with Dr. Xu Xing of the Institute of Vertebrate Paleontology and Paleoanthropology, Beijing. Research projects focus upon the evolutionary relationships of birds to theropod dinosaurs, based upon the collections from the Gobi Desert of Mongolia and China, and the function of the foot of pterosaurs based upon a new specimen from the Early Jurassic of Mexico. Check out the latest news from China.

Dinosaurs and the Origin of Birds

The theropod dinosaurs and primitive birds collected by the AMNH-MAS expeditions to the Gobi Desert include numerous skeletons providing important new information on the relationships of birds to other dinosaurs. Among these are the first embryonic dinosaur skeleton from Mongolia and specimens of oviraptors sitting on nests in a bird-like position. My NSF-funded research, in collaboration with M. Norell, L. Chiappe, and P. Makovicky, focuses on the relationships among the closest relatives of birds, especially oviraptorids, dromaeosaurids, troodontids, the bizarre therizinosaurs, and the unusual basal bird Mononykus. Supported by a $3 million NSF Tree of Life grant in 2002 (along with J. Cracraft, G. Barrowclough, and S. Hackett), we are now developing an online database of theropod and bird morphological characters including images of each character.

Locomotion in Pterosaurs

An exquisite skeleton of a primitive pterosaur from Huizachal Canyon in Mexico provides important information about the capacity for walking and running in these animals. In particular, the joint at the base of the toes (the metatarsal-phalangeal joints) are nearly flat, preventing them from bending back into a posture in which the animal walked or ran on its toes, rather than on the ball of its foot. This research is in collaboration with James Hopson of the University of Chicago.

Thalattosaurs

Abundant isolated bones and articulated skulls of this obscure group of lizard-like reptiles distantly related to dinosaurs were collected in Nevada and are currently being removed from their limestone matrix in acid baths. This work is in collaboration with Hans-Dieter Sues of the Royal Ontario Museum and Nick Hotton of the National Museum of Natural History and funded by the National Geographic Society.

Phylogeny of Crocodylomorpha

My dissertation work on crocodylomorph phylogeny identified the major clades in this large group, which includes living crocodylians and a wide variety of extinct forms related more or less distantly to them. Clark (1994) presented a cladogram and data matrix for the Crocodyliformes, and Clark et al. (2000) presented an analysis of the remaining crocodylomorphs.

Phylogenetic Studies of Fossils

Fossils offer important information about evolutionary relationships, but they also are difficult to study because of they are invariably incomplete. My research explores the limitations and advantages of information from fossils, especially regarding the effect of missing data and the inference of non-morphological features of fossils.

Field Work

My field research, undertaken nearly every summer since my co-discovery of the Fruita Paleontological Area in the Late Jurassic of Colorado with George Callison in 1975, has focused on fossil vertebrates in dinosaur-age deposits (i.e., the Mesozoic). Two areas of special interest are the Cretaceous dinosaur deposits of Mongolia, as a member and co-organizer of the American Museum of Natural History-Mongolian Academy of Sciences expeditions to the Gobi Desert since 1991, and an Early Jurassic locality in the Sierra Madre Oriental of Mexico I discovered in 1982 with R. Cifelli, in Huizachal Canyon. Other field work includes expeditions to Late Triassic marine deposits of Nevada (with H.-D. Sues and N. Hotton), Early Jurassic fluvial deposits of the Glen Canyon Group in Arizona (with D. Fastovsky and K. Padian), Early Jurassic deposits in southern Arizona, Cretaceous-Tertiary boundary deposits of eastern Montana (with W. Clemens), Early Cretaceous deposits of central Mexico (with R. Hernandez and M. Montellano), Jurassic deposits of Venezuela (with M. Sanchez-Villagra), Tertiary deposits of Yemen (with I. Tattersall and P. Whybrow), and Cenozoic deposits of Vietnam (with I. Tattersall and J. Schwartz).

In 2000 I began a new field project in Middle to Late Jurassic deposits of Xinjiang, northwestern China along with Dr. Xu Xing. Organized in collaboration with the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, this project is directed towards discovering the earliest members of dinosaur lineages dominating the Cretaceous Period, including the theropod dinosaurs most closely related to birds.