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| Patagomaia chainko Chimento, Agnolín, García-Marsà, Manabe, Tsuihiji & Novas, 2024 |
Abstract
Theria represent an extant clade that comprises placental and marsupial mammals. Here we report on the discovery of a new Late Cretaceous mammal from southern Patagonia, Patagomaia chainko gen. et sp. nov., represented by hindlimb and pelvic elements with unambiguous therian features. We estimate Patagomaia chainko attained a body mass of 14 kg, which is considerably greater than the 5 kg maximum body mass of coeval Laurasian therians. This new discovery demonstrates that Gondwanan therian mammals acquired large body size by the Late Cretaceous, preceding their Laurasian relatives, which remained small-bodied until the beginning of the Cenozoic. Patagomaia supports the view that the Southern Hemisphere was a cradle for the evolution of modern mammalian clades, alongside non-therian extinct groups such as meridiolestidans, gondwanatherians and monotremes.
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| Patagomaia chainko holotype, MPM-PV-23365 (a) fragments of the left pelvis; (b) silhouette and skeletal scheme with details of the preserved bones; (c) distal end of the left ulna; (d) proximal end of the right femur and distal end of the left femur; e, proximal half of the left tibia. Scale bar: 20 mm. |
Class Mammalia Linnaeus 1758
Subclass Theria Parker and Haswell, 1897
Patagomaia nov. gen.
Generic diagnosis: Patagomaia is a large mammal (~ 14 kg) distinguished by the following unique combination of character states: fused acetabulum with a complete rim lacking a dorsal emargination; femur with subspherical head having a well-defined fovea capitis; femur head separated from the rest of the bone by a well-defined and medially tilted neck; lesser trochanter of femur small and located on the posteromedial surface of the shaft; distal end of femur with nearly symmetrical distal condyles and reduced epicondyles. Patagomaia further differs from other Mesozoic mammals in having the autapomorphic condition of a thick, well-defined, and obliquely oriented intercondylar ridge delimiting a deep fossa at the distal end of the femur.
Etymology: Patago, from Patagonia; maia, mother in Greek.
Patagomaia chainko sp. nov.
Etymology: The species name is derived from the Aonikenk language: chaink, large and ko, bone.
Nicolás R. Chimento, Federico L. Agnolín, Jordi García-Marsà, Makoto Manabe, Takanobu Tsuihiji and Fernando E. Novas. 2024. A large therian Mammal from the Late Cretaceous of South America. Scientific Reports 14: 2854. DOI: 10.1038/s41598-024-53156-3