Amphibian Body Impressions from the Mississippian of Pennsylvania, USA

Abstract

Temnocorpichnus isaacleai is a new ichnogenus and ichnospecies of temnospondyl amphibian body impression from the Mississippian (Visean) Mauch Chunk Formation of eastern Pennsylvania, United States. The shovel-shaped head, robust limbs, relatively short trunk and smooth integument diagnose the ichnotaxon and readily distinguish it from Hermundurichnus and Sauropleura, the only other named body impressions of Paleozoic tetrapods. Temnocorpichnus is a compound ichnogenus in which the footprint ichnogenus Batrachichnus is a behaviorally distinct component. The temnospondyl identity of Temnocorpichnus adds to the sparse and earliest records of temnspondyls, which are of Visean age. The smooth integument of the ichnogenus does not support the presence of ventral scales or armor in the earliest temnospondyls, but body proportions of the Mauch Chunk body impressions indicate a relatively terrestrial temnospondyl not matched by any taxon now known from bones. Three closely associated impressions of Temnocorpichnus on a single bedding plane suggest some sort of gregarious behavior in Mississippian temnospondyls and may support speculation that internal fertilization and associated courtship behavior evolved independently in one group of amphibians more than 300 million years ago.

Keywords:

• Body impression
• temnospondyl
• Mississippian
• Pennsylvania
• Mauch Chunk Formation
• Temnocorpichnus

ACKNOWLEDGMENTS

We thank the staff and management of the Reading Public Museum for access to the fossils. Robert Holmes commented on the identity of the tracemaker, and Matt Celeskey drew Figure 2. Funding was provided by the Kutztown University Research Committee and the Professional Development Committee of the Pennsylvanian State System of Higher Education. Christian A. Meyer provided a very helpful review of the manuscript.