Surviving the Cretaceous-Paleogene mass extinction event: A terrestrial stem turtle in the Cenozoic of Laurasia

Adán Pérez-García

doi:10.1038/s41598-020-58511-8

Abstract

Findings of terrestrial stem turtles are not uncommon at Mesozoic continental sites in Laurasia, especially during the Upper Cretaceous. Thus, the record of several lineages is known in uppermost Cretaceous ecosystems in North America (Helochelydridae), Europe (Helochelydridae and Kallokibotion) and Asia (Sichuanchelyidae). No terrestrial stem turtle had been described in Laurasia after the Cretaceous-Paleogene mass extinction event. Thus, the only representatives described in the Cenozoic record worldwide corresponded to forms from southern Gondwana, where some of them survived until the Holocene. A bizarre terrestrial stem turtle from the upper Thanetian (upper Paleocene) of Europe is described here: Laurasichersis relicta gen. et sp. nov. Despite its discovery in France, in Mont de Berru (Marne), this Laurasian taxon is not recognized as a member of a European clade that survived the Cretaceous-Paleogene extinction event. It belongs to Sichuanchelyidae, a hitherto exclusively Asian Mesozoic group, known from the Middle Jurassic. Finds at the Belgian site of Hainin (Hainaut) show that this dispersion from Asia and the occupation of some niches previously dominated by European Mesozoic terrestrial stem forms had already taken place a few million years after the mass extinction event, at the end of the lower Paleocene.

Highlights

Findings of terrestrial stem turtles are not uncommon at Mesozoic continental sites in Laurasia, especially during the Upper Cretaceous
After the currently recognized disappearance of the terrestrial stem turtles known in the Upper Cretaceous in Europe (Kallokibotion bajazidi and several members of Helochelydridae4,13) at the end of the Maastrichtian, probably as a result of the Cretaceous-Paleogene mass extinction event, some of the available European niches are identified here as occupied by this Asian lineage
The analysis of the new form from the upper Thanetian in France allows the reassignment of some remains from the upper Danian site of Hainin (Province of Hainaut)[16], located in the Franco-Belgian Basin, but in Belgium

Summary

Introduction

Findings of terrestrial stem turtles are not uncommon at Mesozoic continental sites in Laurasia, especially during the Upper Cretaceous. Despite its discovery in France, in Mont de Berru (Marne), this Laurasian taxon is not recognized as a member of a European clade that survived the Cretaceous-Paleogene extinction event It belongs to Sichuanchelyidae, a hitherto exclusively Asian Mesozoic group, known from the Middle Jurassic. During the uppermost Cretaceous, three lineages of terrestrial stem turtles, all of them belonging to Perichelydia, inhabited Laurasia: the abundant and diverse helochelydrids, restricted to Euramerica, and known from the Late Jurassic (Tithonian); Kallokibotion bajazidi, from the Maastrichtian in Romania, the record of this exclusively European lineage being identified from the Santonian; and the Mongolian Maastrichtian Mongolochelys efremovi, recognized as the youngest descendant of an exclusively Asian clade, Sichuanchelyidae, identified from the Middle Jurassic, but with an extensive ghost lineage that spans from the Late Jurassic to the Late Cretaceous[1,2,3,4,5] They are all currently recognized as exclusively Mesozoic clades, and no stem terrestrial representative has been described in the Laurasian Cenozoic record. Testudinata Klein, 1760 Mesochelydia Joyce, 2017 Perichelydia Joyce, 2017 Sichuanchelyidae Tong et al, 2012 Laurasichersis relicta gen. et sp. nov. (Figures 1–7)

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Conclusion