Chirotherium Trackways from the Middle Triassic of Guizhou, China

Abstract

Triassic tetrapod footprints from China are less well known than those from the Jurassic and Cretaceous. Archosaurian trackways of the ichnogenus Chirotherium were found in the Middle Triassic Guanling Formation in Zhenfeng County (Guizhou Province) at the southwestern edge of the Yangtze plate in the early 1960s but were not correctly identified and adequately described until 40 years later. Here we give a detailed re-description and review of the trackways, which are known from two localities near the villages of Niuchang and Longchang. They occur on the bedding surface of a mud-cracked argillaceous dolostone deposited in a near-shore, shallow-water environment. Their morphology and general trackway pattern indicate that they pertain to the ichnospecies Chirotherium barthii, well known from Middle Triassic track surfaces of Europe, North and South America, and northern Africa. A peculiarity of the trackways from China are the low pace angulation and stride length, reflecting slow-moving trackmakers, which were basal crown-group archosaurs, possibly early representatives of the dinosaur-bird line or, alternatively, stem-group crocodylians. These tracks constitute the only chirotheriid record known from Asia thus far and indicate a Pangea-wide distribution for this ichnotaxon. Biostratigraphically, assemblages with C. barthii are characteristic of the early Anisian, an age assignment already supported for the Guanling Formation based on conodont and bivalve biostratigraphy. In contrast, however, radiometric data from an interlayered ash bed indicate a Ladinian age.

Keywords:

• Chirotherium barthii
• Middle Triassic
• Basal archosaurs
• Guanling Formation

ACKNOWLEDGMENTS

The authors appreciate helpful reviews and comments of Sebastian Voigt, Grzegorz Niedźwiedzki, and the associate editor of this journal. We thank Hongbo Lü (Institute of Earth Resources and Information, University of Petroleum, Shandong Province, China) and Yuxu Zhang (Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China) for their helpful information and photos. Also, we appreciate Xingbo Deng and his family from Beipanjiang Township for their help in field work. Ralf Werneburg, Natural History Museum Schleusingen, Germany, helped with a photograph of the Chirotherium–Monument. This research was supported by Junfeng Zhao (BG4CIP), Backpacker and HAMER (Amateur (Ham) Radio). Jungfeng Zhao also assisted and provided logistical support for the studies during the field expedition.