Skeletal remains of a freshwater jalodontid chondrichthyan from the Upper Triassic Arden Sandstone Formation of Warwickshire, UK.
- 1University of Birmingham
Abstract
The Triassic was a significant period in the evolution of modern chondrichthyans (sharks, rays and chimaeras), bridging the gap between Paleozoic chondrichthyans and more recognizably modern Mesozoic forms. Although only a handful of Triassic skeletal fossils of chondrichthyans are known worldwide their calcified cartilages provide rare insight into their anatomy, evolution, and lifestyle. Here we use computed tomographic methods to describe six chondrichthyan skeletal fossils from the Carnian (Upper Triassic) Arden Sandstone Formation of Shrewley, Warwickshire, UK, consisting of a partial braincase, jaws, pectoral fin radials, caudal fin hypurals, and dorsal fin basal cartilages, and characterize their paleoenvironment. We assign the braincase and jaws, and tentatively assign the post-cranial remains, to the jalodontid taxon Keuperodus brodiei, previously described on the basis of teeth including those from the same locality. This represents the first known occurrence of articulated chondrichthyan skeletal remains from the Upper Triassic and the first interpretable cranial cartilages of the Order Jalodontiformes. The partial braincase of K. brodiei preserves an unusual basicranial circulation, almost completely embedded in the basicranium, and the jaws have an elongate extended shape; both features are akin to Paleozoic phoebodontid chondrichthyans. Phylogenetic analysis recovers K. brodiei as a stem-group elasmobranch with a close relationship to phoebodonts, one of several Paleozoic shark lineages to have independently survived the end-Permian mass extinction. However, unlike Phoebodontiformes and all other Jalodontiformes, K. brodiei occupied freshwater lake shorelines and associated fluvial feeder channels, revealing a possible freshwater refugium for Jalodontiformes towards at the end of their stratigraphic range.
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BibTeX
@misc{tokeley2026skeletal,
title = {{Skeletal remains of a freshwater jalodontid chondrichthyan from the Upper Triassic Arden Sandstone Formation of Warwickshire, UK.}},
author = {R. R. Tokeley and R. P. Dearden and S. D. Burley and J. D. Radley and I. Sansom},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.08.749451},
url = {https://www.biorxiv.org/content/10.64898/2026.09.08.749451v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Skeletal remains of a freshwater jalodontid chondrichthyan from the Upper Triassic Arden Sandstone Formation of Warwickshire, UK.
AU - R. R. Tokeley
AU - R. P. Dearden
AU - S. D. Burley
AU - J. D. Radley
AU - I. Sansom
PY - 2026
DA - 2026/09/08
PB - bioRxiv
DO - 10.64898/2026.09.08.749451
UR - https://www.biorxiv.org/content/10.64898/2026.09.08.749451v1
AB - The Triassic was a significant period in the evolution of modern chondrichthyans (sharks, rays and chimaeras), bridging the gap between Paleozoic chondrichthyans and more recognizably modern Mesozoic forms. Although only a handful of Triassic skeletal fossils of chondrichthyans are known worldwide their calcified cartilages provide rare insight into their anatomy, evolution, and lifestyle. Here we use computed tomographic methods to describe six chondrichthyan skeletal fossils from the Carnian (Upper Triassic) Arden Sandstone Formation of Shrewley, Warwickshire, UK, consisting of a partial braincase, jaws, pectoral fin radials, caudal fin hypurals, and dorsal fin basal cartilages, and characterize their paleoenvironment. We assign the braincase and jaws, and tentatively assign the post-cranial remains, to the jalodontid taxon Keuperodus brodiei, previously described on the basis of teeth including those from the same locality. This represents the first known occurrence of articulated chondrichthyan skeletal remains from the Upper Triassic and the first interpretable cranial cartilages of the Order Jalodontiformes. The partial braincase of K. brodiei preserves an unusual basicranial circulation, almost completely embedded in the basicranium, and the jaws have an elongate extended shape; both features are akin to Paleozoic phoebodontid chondrichthyans. Phylogenetic analysis recovers K. brodiei as a stem-group elasmobranch with a close relationship to phoebodonts, one of several Paleozoic shark lineages to have independently survived the end-Permian mass extinction. However, unlike Phoebodontiformes and all other Jalodontiformes, K. brodiei occupied freshwater lake shorelines and associated fluvial feeder channels, revealing a possible freshwater refugium for Jalodontiformes towards at the end of their stratigraphic range.
ER -