Chirotheria and Other Ichnotaxa of the European Triassic

Abstract

At the end of the Permian, numerous amphibians and therapsids vanished, creating many empty ecological niches, which were occupied by new creatures. This event brought new trends in animal locomotion thanks to modifications of the skeleton limbs. The newcomers were faster and more dangerous for other families. The prominent ichnogenera were Synaptichnium, Chirotherium, Brachychirotherium, Isochirotherium, and Sphingopus. Their trackmakers were Thecodonts, reptiles having the above-mentioned evolutive characteristics. Dinosaurs, which appeared at the end of the Triassic period, were likely their descendants, which raises the question of when and where the dinosaurs originated. The comparison of the trackways of the Middle and upper Triassic with those of the lower Jurassic leads to the conclusion that the two sets of tridactyl ichnites were similar and were made by the same group of trackmakers, the dinosaurs. We had many passionate discussions on this subject with Bill Sarjeant when studying the discoveries made in Europe the past 40 years.

Keywords:

• Ichnofossils
• Triassic
• Thecodonts
• locomotion
• evolution
• dinosaurs

Acknowledgments

The authors are most grateful to Dr. S. George Pemberton, University of Alberta at Edmonton, who helped us prepare this work; Prof. Martin G. Lockley, University of Colorado at Denver and Dr. Spencer G. Lucas, New Mexico Museum of Natural History, Albuquerque, for their helpful review of the manuscript and suggestions for improvements.