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A new notosuchian crocodyliform from the Early Paleocene of Patagonia and the survival of a large-bodied terrestrial lineage across the K–Pg mass extinction

Bravo, Gonzalo; Pol, Diego; Leardi, Juan; Krause, Marcelo; Nicholl, Cecily; Rougier, Guillermo; Mannion, Philip; (2025) A new notosuchian crocodyliform from the Early Paleocene of Patagonia and the survival of a large-bodied terrestrial lineage across the K–Pg mass extinction. Proceedings of the Royal Society B: Biological Sciences , 292 (2043) , Article 20241980. 10.1098/rspb.2024.1980. Green open access

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Abstract

Sebecid notosuchians are the only terrestrial crocodyliforms to survive theCretaceous–Palaeogene extinction, 66 Ma, which eliminated large-bodiedspecies (above approximately 5 kg) in terrestrial ecosystems. Early sebecidevolution is unclear due to the scarcity of remains from both sides ofthe boundary. We present the stratigraphically earliest post-extinctionnotosuchian record, from the lower Palaeocene Salamanca Formation ofPatagonia. Tewkensuchus salamanquensis n. gen. n. sp. has unique features,including a skull roof with elevated lateral margins, and an accessory pegand socket articulation between the postorbital and posterior palpebral.Our phylogenetic analysis allies Tewkensuchus with a clade of predatorialcrocodyliforms from the Eocene of Europe (and possibly of Africa, asEremosuchus may also belong to this clade). This clade forms the sistertaxon of South American sebecids. We name Sebecoidea for this moreinclusive clade of Eurogondwanan notosuchians and suggest that its spatialdistribution reflects earlier diversification and dispersal events, whichare only partially known. We estimate a body mass of around 300 kgfor Tewkensuchus, one of the largest known notosuchians. Phylogeneticoptimization of notosuchian body size change reconstructs a Cretaceous–Palaeogene boundary-crossing sebecoidean lineage with an estimated massbetween 332 and 443 kg. This provides the first support for the survival of alarge-bodied terrestrial vertebrate lineage across the K–Pg boundary.

Type: Article
Title: A new notosuchian crocodyliform from the Early Paleocene of Patagonia and the survival of a large-bodied terrestrial lineage across the K–Pg mass extinction
Open access status: An open access version is available from UCL Discovery
DOI: 10.1098/rspb.2024.1980
Publisher version: https://doi.org/10.1098/rspb.2024.1980
Language: English
Additional information: © 2025 The Authors. Published by the Royal Society under the terms of the Creative Commons AttributionLicense (http://creativecommons.org/licenses/by/4.0/).
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10205233
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