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Antiquity of forelimb ecomorphological diversity in the mammalian stem lineage (Synapsida)

2019; National Academy of Sciences; Volume: 116; Issue: 14 Linguagem: Inglês

10.1073/pnas.1802543116

1091-6490

Jacqueline K. Lungmus, Kenneth D. Angielczyk,

Morphological variations and asymmetry

Significance Mammals and their closest fossil relatives use their shoulders and forelimbs for many functions, which is reflected by the great range of mammalian forelimb shapes. We found that forelimb shape diversity in the early mammalian lineage (Synapsida) began to increase about 270 million years ago, with the emergence of a group called Therapsida, and is accompanied by new forelimb functions. The functional diversification of therapsid forelimbs was curtailed by the Permo-Triassic mass extinction, but eventually continued as more mammal-like therapsids evolved new ecologies. Our analyses characterize the deep time origin of a quintessential part of the mammalian body plan: evolutionarily labile forelimbs that can be deployed in a wide range of functional and ecological roles.