Grouping behavior in a Triassic marine apex predator

Neil P Kelley; Randall B Irmis; Paige E dePolo; Paula J Noble; Danielle Montague-Judd; Holly Little; Jon Blundell; Cornelia Rasmussen; Lawrence M E Percival; Tamsin A Mather; Nicholas D Pyenson

doi:10.1016/j.cub.2022.11.005

Grouping behavior in a Triassic marine apex predator

Curr Biol. 2022 Dec 19;32(24):5398-5405.e3. doi: 10.1016/j.cub.2022.11.005.

Authors

Affiliations

¹ Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, 1001 Madison Drive NW, Washington, DC 20560, USA. Electronic address: neil.p.kelley@vanderbilt.edu.
² Natural History Museum of Utah, University of Utah, 301 Wakara Way, Salt Lake City, UT 84108, USA; Department of Geology & Geophysics, University of Utah, 115 S 1460 E, Salt Lake City, UT 84112, USA.
³ School of GeoSciences, University of Edinburgh, Grant Institute, James Hutton Road, Edinburgh, Scotland EH9 3FE, UK; Department of Geological Sciences and Engineering, University of Nevada-Reno, 1664 N. Virginia Street, Reno, NV 89557, USA.
⁴ Department of Geological Sciences and Engineering, University of Nevada-Reno, 1664 N. Virginia Street, Reno, NV 89557, USA.
⁵ Natural History Museum of Utah, University of Utah, 301 Wakara Way, Salt Lake City, UT 84108, USA; Department of Geosciences, University of Arizona, 1040 E 4th St, Tucson, AZ 85721, USA.
⁶ Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, 1001 Madison Drive NW, Washington, DC 20560, USA.
⁷ Digitization Program Office 3D Lab, Office of the Chief Information Officer, Smithsonian Institution, Landover, MD 20758, USA.
⁸ Natural History Museum of Utah, University of Utah, 301 Wakara Way, Salt Lake City, UT 84108, USA; Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, 2305 Speedway Stop C1160, Austin, TX 78712-1692, USA.
⁹ Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, 2305 Speedway Stop C1160, Austin, TX 78712-1692, USA; Analytical, Environmental and Geochemistry Group (AMGC), Vrije Universiteit Brussel, Pleinlaan 2, Brussels 1050, Belgium.
¹⁰ Analytical, Environmental and Geochemistry Group (AMGC), Vrije Universiteit Brussel, Pleinlaan 2, Brussels 1050, Belgium.
¹¹ Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK.

PMID: 36538877
DOI: 10.1016/j.cub.2022.11.005

Abstract

Marine tetrapods occupy important roles in modern marine ecosystems and often gather in large aggregations driven by patchy prey distribution,¹^,² social or reproductive behaviors,³^,⁴ or oceanographic factors.⁵ Here, we show that similar grouping behaviors evolved in an early marine tetrapod lineage, documented by dozens of specimens of the giant ichthyosaur Shonisaurus in the Luning Formation in West Union Canyon, Nevada, USA.⁶^,⁷ A concentration of at least seven skeletons closely preserved on a single bedding plane received the bulk of previous attention. However, many more specimens are preserved across ∼10⁶ square meters and ∼200 stratigraphic meters of outcrop representing an estimated >10^5-6 years. Unlike other marine-tetrapod-rich deposits, this assemblage is essentially monotaxic; other vertebrate fossils are exceptionally scarce. Large individuals are disproportionately abundant, with the exception of multiple neonatal or embryonic specimens, indicating an unusual demographic composition apparently lacking intermediate-sized juveniles or subadults. Combined with geological evidence, our data suggest that dense aggregations of Shonisaurus inhabited this moderately deep, low-diversity, tropical marine environment for millennia during the latest Carnian Stage of the Late Triassic Period (237-227 Ma). Thus, philopatric grouping behavior in marine tetrapods, potentially linked to reproductive activity, has an antiquity of at least 230 million years.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Biological Evolution
Ecosystem*
Fossils*
Humans
Infant, Newborn
Oceanography
Phylogeny