A NEW BIZARRE ARMADILLO (MAMMALIA, XENARTHRA, DASYPODIDAE) FROM THE LATE MIOCENE OF ECUADOR

BARASOAIN, D.; ROMÁN CARRION, J.L.; ZURITA, A.E.; MIÑO BOILINI, A. R.

Otro; RCAPA 2022; 2022

The Dasypodidae (Astegotheriinae, Stegotheriinae and Dasypodinae), constitute the sister group of the remaining diversity of “armadillos” (Chlamyphoridae), and the most ancient group withinXenarthra, with a divergence estimated in ca. 40 Ma. Among Dasypodidae, only Dasypodinae hasliving representatives, including over 8 species of Dasypus. Dasypodinae armadillos have theiroldest records coming from the middle Miocene of La Venta (Colombia), and become relativelyabundant at lower latitudes in South America during the Miocene. Recognized taxa for this lapseinclude Plesiodasypus colombianus (La Victoria Formation, ca. 13 Ma) and Anadasypus hondanus (Villavieja Formation, ca. 12 Ma) for the middle Miocene of La Venta, Colombia, and Anadasypus aequatorianus (Letrero Formation, ca. 11.2–9 Ma) for the late Miocene of Nabón, Ecuador. Here, we report a new and bizarre armadillo exhumed from the Letrero Formation levels outcropping at Nabón basin, southern Ecuador. Materials (EPNPv-6381) are housed in the Colección de Paleontología, Escuela Politécnica Nacional (Quito, Ecuador), and include several fixed and mobile osteoderms of the dorsal carapace belonging to a single individual, which was found partiallyarticulated in the field. The presence of enlarged mobile osteoderms with a very developed articular portion and a clear dasypodine-like ornamentation pattern (shared by all dasypodine armadillos) on their exposed surface allow to include it within Dasypodidae Dasypodinae. In turn, the presence of fixed osteoderms with a rectangular outline, and an ornamentation pattern composed of an elongated and keeled central figure surrounded by minor peripheral figures allow its inclusionwithin Plesiodasypus. This new taxon is supported by some unusual features that represent solidautapomorphic characters, being the most relevant: 1) denticulated lateral edges in fixed osteodermsand the articular portions of mobile osteoderms, and 2) very large foramina along the main sulcusthat delimitates the central figure of mobile osteoderms, tentatively interpreted as a complexglandular system restricted to mobile osteoderms, though a certain degree of associated pilositycannot be discarded. A morphological cladistic analysis including several extinct and extantChlamyphoridae and Dasypodidae armadillos corroborates its inclusion within Plesiodasypus, aswell as the early divergent position of this genus within Dasypodinae. This taxon represents thesecond armadillo recorded for the Letrero Formation (the other being A. aequatorianus), increasingthe Dasypodidae diversity at low latitudes during the late Miocene. Additionally, the unusualmorphology of this taxon is concordant with the associated endemic paleofauna previously recordedat Nabón basin, which suggests some kind of isolation.