Diverse assemblage of Middle Triassic continental tetrapods from the Newark Supergroup of Nova Scotia (Canada)

ABSTRACT

Triassic strata of the Economy Member of the Wolfville Formation (Newark Supergroup) exposed along the shorelines in Colchester County, Nova Scotia, have yielded an assemblage of continental tetrapods that is clearly different from other Triassic tetrapod communities in eastern North America, including the Late Triassic (Carnian) one from the overlying Evangeline Member of the Wolfville Formation. Although dissociated and fragmentary, the skeletal elements document the presence of a lonchorhynchine trematosaurid and at least two taxa of capitosauroid temnospondyls, procolophonid parareptiles, several taxa of archosauromorph reptiles, and a kannemeyeriiform dicynodont synapsid. Particularly noteworthy is the first definite record of the long-necked archosauromorph Tanystropheus from eastern North America. The strata of the Economy Member were deposited in a semiarid setting but the presence of various temnospondyls indicates the existence of perennial bodies of water. The age of this unit has long been regarded as Middle Triassic (Anisian to Ladinian) based on the tetrapod record, and the present study supports this assessment. The tetrapod assemblage most closely resembles those from the upper Moenkopi Formation of the American Southwest and the upper Middle to Upper Buntsandstein of Germany. The Economy Member is the oldest known Triassic tetrapod-bearing stratigraphic unit as well as the first occurrence of Middle Triassic continental tetrapods in eastern North America.

ACKNOWLEDGMENTS

We would like to acknowledge the late D. Baird who first discovered tetrapod remains from the Economy Member. He also encouraged and actively supported P.E.O. and H.-D.S. in their own fieldwork in the Fundy Basin over many years. C. F. Kammerer identified YPM VPPU.030405, and H.-D.S. acknowledges informative discussions with M. D. Ezcurra regarding the archosauriform specimens. We are particularly indebted to D. Serratos for supplying photographs of the procolophonid jaws housed at the Fundy Geological Museum. James Morrison skillfully drew Figs. 7A, B and 8C–E, and A. Mann took the photograph for Fig. 8B. D. Brinkman provided curatorial assistance for the specimens from the former Princeton collection. We thank C. F. Kammerer and T. Sulej for helpful comments on a draft of the manuscript.