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in Ke, Wu, Zelenitsky, ... et Han, 2021 Illustration: Masato Hattori. |
Abstract
Turtle eggs containing embryos are exceedingly rare in the fossil record. Here, we provide the first description and taxonomic identification, to our knowledge, of a fossilized embryonic turtle preserved in an egg, a fossil recovered from the Upper Cretaceous Xiaguan Formation of Henan Province, China. The specimen is attributed to the Nanhsiungchelyidae (Pan-Trionychia), an extinct group of large terrestrial turtles (possibly the species Yuchelys nanyangensis). The egg is rigid, spherical, and is one of the largest and thickest shelled Mesozoic turtle eggs known. Importantly, this specimen allowed identification of other nanhsiungchelyid egg clutches and comparison to those of Adocidae, as Nanhsiungchelyidae and Adocidae form the basal extinct clade Adocusia of the Pan-Trionychia (includes living soft-shelled turtles). Despite the differences in habitat adaptations, nanhsiungchelyids (terrestrial) and adocids (aquatic) shared several reproductive traits, including relatively thick eggshells, medium size clutches and relatively large eggs, which may be primitive for trionychoids (including Adocusia and Carrettochelyidae). The unusually thick calcareous eggshell of nanhsiungchelyids compared to those of all other turtles (including adocids) may be related to a nesting style adaptation to an extremely harsh environment.
Keywords: Nanhsiungchelyidae, China, thick egg, shell, Upper Cretaceous, embryo, turtle egg
Systematic palaeontology:
Order Testudines Linnaeus, 1758
Infraorder Cryptodira Cope, 1868
Superfamily Trionychoidae Fitzinger, 1826
Family Nanhsiungchelyidae Yeh, 1966
Genus and species indet.
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| A Nanhsiungchelyid turtle egg containing an embryo. |
Material. CUGW EH051, a complete egg containing embryonic remains.
Locality and horizon. Specimen CUGW EH051 was collected in Neixiang County, Nanyang City, Henan Province, China (electronic supplementary material, figure S1); Xiaguan Formation, Upper Cretaceous. ....
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Illustration: Masato Hattori. |
Yuzheng Ke, Rui Wu, Darla K. Zelenitsky, Don Brinkman, Jinfeng Hu, Shukang Zhang, Haishui Jiang and Fenglu Han. 2021. A Large and Unusually Thick-shelled Turtle Egg with Embryonic Remains from the Upper Cretaceous of China. Proceedings of the Royal Society B. DOI: 10.1098/rspb.2021.1239
