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

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.

KEYWORDS:

• Early Jurassic
• dinosaur
• podokesaurus
• taphonomy
• pseudomorphs
• bone casts
• bone dissolution

Acknowledgments

We chiefly thank the Nash family of Granby, Massachusetts, for which the specimen described herein is named to honor the memory of Kornell R. Nash and his father Carlton S. Nash. We also express gratitude to the Curator of the Bruce Museum in Greenwich, Connecticut, Daniel Ksepka, for accessioning the Nash Specimen for the benefit of museum goers and researchers. Author Agostini extends special thanks to Matthew Seney and Alex Ruger of the Black Hills Institute of Geological Research and Joshua Schnell of Brown University for their assistance in making the first mold replicas of the Nash Specimen. Rebecca Melius and Katie Barrett of the Museum of Science in Boston provided unprecedented access to MOS.2001.248. Claire Pless, a geology technician at Mount Holyoke College, prepared the petrographic thin sections for this study. Lauren Kirby provided assistance with line drawings and figure editing. Communications with Paul Olsen, Patrick Getty, Stephen Gatesy, Peter Falkingham, Robert Bakker, Nicholas McDonald, Will Sillin, and Murray Gingras were instrumental in interpreting the specimen, strengthening arguments, and aiding interdisciplinary collaboration.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Dedication

We, the authors, dedicate this paper to the life, legacy, and memory of Patrick R. Getty, Ph.D. The Nash Specimen (BRCM 2021.10) described herein from the Hartford Basin was of great interest to the late Professor Getty. This paper would not have been possible or as meaningful without his important contributions to ichnology and paleontology.

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.