Geometric morphometrics as a tool to identify Dasypodini osteoderms: Implications for the oldest records of Dasypus
SALGADO-AHUMADA, JUAN S.; ERCOLI, MARCOS D.; ÁLVAREZ, ALICIA; CASTRO, MARIELA C.; CIANCIO, MARTÍN R.
JOURNAL OF MAMMALIAN EVOLUTION
Año: 2023 vol. 30 p. 597 - 614
Cingulata (Mammalia, Xenarthra) is one of the most conspicuous clades in the Cenozoic fossil record of South America, largely due to the high abundance of disarticulated osteoderms in most fossiliferous sites of the continent. Nevertheless, the fragmentary nature of this material hinders the identification of extinct taxa, particularly in groups that do not exhibit great shape diversity in the ornamentation of the osteoderms, as occurs in armadillos of the clade Dasypodini (long-nosed armadillos). Methodologies that quantify shape variability could offer an alternative strategy for identifying these fragmentary fossil remains. In the present study, we apply geometric morphometric analysis to assess shape variation of Dasypodini osteoderms. First, we evaluate previous referrals of two isolated late Miocene osteoderms to Dasypus, one identified as Dasypus sp. from the Guanaco Formation (Jujuy province, Argentina) and the other identified as D. neogaeus from the Ituzaingó Formation (Entre Ríos province, Argentina). Second, we evaluate the identification of a disarticulated osteoderm from the middle Miocene of Brazil to Anadasypus sp. nov.?. Our results distinguish two main generic clusters, Plesiodasypus + Anadasypus and Dasypus + Propraopus, supporting previous referral of disarticulated osteoderms from Jujuy and Entre Ríos to the genus Dasypus. This confirms the extension of the biochron of Dasypus by at least 3 million years, from the early Pliocene to the late Miocene. The present contribution offers a new application for geometric morphometrics to evaluate taxonomic assignments of fossil Dasypodini osteoderms.