THE STATUS OF EUCHOLOEOPS FRONTO AND E. LAFONEI (XENARTHRA, FOLIVORA, MEGALONYCHIDAE) IN THE SYSTEMATICS OF THE EARLY MIOCENE EUCHOLOEOPS (SANTA CRUZ, ARGENTINA)

DE IULIIS, GERARDO; BARGO, SUSANA; TOLEDO, NÉSTOR; TSUJI, LEONARD; VIZCAÍNO, SERGIO

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Año: 2023

0002-7014

This reportis a continuation of the work published a decade ago on the status of specimensassigned in the literature and museum records to the megalonychid sloth Eucholoeops from the Early-middleMiocene Santa Cruz Formation (~ 18 to15.6 Ma, Santacrucian Age) of Argentine Patagonia. This previous reportconcluded that several species (i.e., E. latirostris, E. externus,and E. curtus) are junior synonyms of E.ingens, but the authors were unableto analyze several other species and remains assigned to this genus. Here,analysis of these other species and remains suggest that E. fronto and E. lafoneiare also junior synonyms of E. ingens. Included in the current reportis a specimen recently recovered from the field of E. ingens that preserves,for the first time, an ectotympanic of Eucholoeops.In addition to the mainly cranial skeletal features analyzed here,consideration of postcranial remains indicate that the medial and lateraldistal articular condyles of the femur are both contiguous with the patellartrochlea, in contrast to the previously reported condition of a separatelateral articular condyle in E.ingens. The authors further conclude that several features of E. latifronssuggest that this species is indeed distinct from E. ingens and that somespecimens assigned in the literature to E.ingens cannot be so assigned withconfidence.