April 2, 2016

Very large, sparsely distributed, sinuous, gently dipping and occasionally branching tunnels with subordinate swells, chambers and scratches, are described from the Hettangian Dealul Budinic Member of the Lower Jurassic continental Steierdorf Formation at Anina in the South Carpathians, Romania, and are interpreted as tetrapod burrows. No bone remains have been found in association with these structures. The morphology and large dimensions of the burrows suggest that the trace-makers were sauropsid amniotes, most probably either crocodyliforms or small-sized basal euornithopod dinosaurs, but their therapsid affinities, although less likely, cannot be discarded either. The age, large size and probable origin of these burrows add important information to a poorly documented period of the evolution of tetrapod fossoriality. It may be suggested that within a relatively short interval following the Triassic⁄Jurassic extinction event, when environmental conditions were still marked by strongly seasonal climate with prolonged droughts as well as extreme moisture and temperature fluctuations, fossorial habit probably became yet again an endurance strategy for the burrow makers.

Zoltan Csiki-Sava, Artur Kedzior, Grzegorz Pienkowski & Mihai Emilian Popa (2016)
Hettangian tetrapod burrows from the continental Steierdorf Formation at Anina, western Romania.
Geological Quarterly (advance online publication)
doi: 10.7306/gq.1278