Oldest Chasicotatus (Cingulata, Xenarthra) remains give a new approach to this lineage biochron and taxonomic status

BARASOAIN DANIEL; LUNA, CARLOS A.; QUIÑONES SOFIA I.

Madrid

Congreso; 2nd Palaeontological Virtual Congress; 2020

Eutatini armadillos are a tribe within the subfamilyEuphractinae (Chlamyphoridae), characterizedby large piliferous foramina and the absence of awell-defined carapace scapular buckler. Thoughthere are no living representatives, they are presentin the fossil record from late Eocene to Holocenedeposits of southern South America. Herewe report new materials (CTESPZ-7852, isolatedosteoderms) assigned to the genus ChasicotatusScillato-Yané from Cañadón del Tordillo site(Colloncuran SALMA) of Neuquén Province (Argentina).This represents the southern recordof the genus and extends its biochron by ~6 Ma(previously recorded in ~9?10 Ma). Though thegenus Stenotatus Ameghino was the only Eutatinirecorded for the Colloncuran SALMA so far,remains are assigned to Chasicotatus accordingto traditional diagnosis based on dorsal carapacefeatures; including a flat transitional zonebetween articular and caudal portions of mobileosteoderms, a more dorsal orientation of thepiliferous foramina of the osteoderms, and amore extended main figure of osteoderms ornamentation,that reaches the posterior margin ofthe osteoderm, unlike in Stenotatus. These samecharacters have been used from the first descriptionsof these taxa without being later discussed.However, it is to remark that the morphologicalvariability that they present in current Euphractinaearmadillos such as Chaetophractus villosusDesmarest, or even in other groups such as Dasypodinaeor Tolypeutinae, suggests the futureneed of more detailed revisions in order to verifytheir validity and/or the identification of newmore robust diagnostic characters that allow tokeep supporting the validity of these two taxa.