A New Specimen of Sand Pseudomorph Dinosaur Bones with Tetrapod Tracks from the Early Jurassic, Hartford Basin, USA

Abstract

ABSTRACT Tetrapod tracks from the Lower Jurassic strata of the Hartford Basin (Newark Supergroup) abound in areas of Massachusetts and Connecticut, USA. However, tetrapod skeletal fossils are uncommon, and the co-occurrence of tracks with skeletal material in the same bedding plane is exceedingly rare. Due to this paucity of skeletal material, spatiotemporal gaps and taxonomic incompleteness continue to hamper research on bones preserved as natural casts. Here we report on the discovery of new bone cast specimens and three grallatoroid (Anchisauripus) tracks on a single sandstone slab originating from Portland or Middletown, Connecticut. The Nash Specimen – BRCM 2021.10 – holds important implications for Early Jurassic dinosaur taphonomic history and the paleoenvironment in which dinosaur footprints and bones as natural casts were preserved. Results from this study describe three Anchisauripus tracks and five natural bone casts from an early theropod dinosaur. Judicious comparisons to the only comparable specimen of dinosaur bone casts (MOS.2001. 248) are made in describing the morphological structures and the taphonomic pathways leading to cast formation. The unique taphonomic circumstances of bone casts preserved alongside dinosaur tracks on the same substrate layer provide an intriguing case of the non-preservation of body fossils that merits further research in the Hartford Basin.