INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
Implication of the presence of Megathericulus (Xenarthra: Tardigrada: Megatheriidae) in the Laventan of Peruvian Amazonia
PUJOS, F.; SALAS-GISMONDI, R.; BABY, G.; BABY, P.; GOILLOT, C.; TEJADA, J.; ANTOINE, P.-O.
JOURNAL OF SYSTEMATIC PALAEONTOLOGY
CAMBRIDGE UNIV PRESS
Lugar: Cambridge; Año: 2013 vol. 11 p. 973 - 973
Middle Miocene remains of giant megatheriine ground sloths (Tardigrada, Megatherioidea) are scarce and generally located in southern South America. The discovery of a well-preserved edentulous dentary of Megathericulus sp. from the Middle Miocene (Laventan SALMA; 13.5-11.8 Ma) of the Peruvian Amazon increases our knowledge of this genus, which had previously been recognized in Argentina. A preliminary revision of the earliest Megatheriinae allowed clustering the four middle Miocene species within the genus Megathericulus Ameghino: M. patagonicus Ameghino, M. primaevus Cabrera, M. andinum (Kraglievich), and M. cabrerai (Kraglievich). This small-sized genus is mainly characterized by a lateral depression that borders m1, a posterior external opening of the mandibular canal anterior to the base of the ascending ramus that opens anteriorly or anterodorsally, base of the symphysis located anteriorly to the m1, important anteroposterior compression of the teeth, elongation of the region of the maxilla anterior to the M1, humerus elongated and gracile, patellar trochlea of femur contiguous with medial and lateral articular facets for tibia, and strongly developed odontoid tuberosity, sesamoidal facet, and subodontoid fossa of the astragalus. The genus Eomegatherium Kraglievich is therefore restricted to the Huayquerian SALMA of Argentina and represented by a single species, E. nanum Burmeister. Megatheriinae form the first clade of Tardigrada in which the caniniform tooth has been secondarily modified into a molariform tooth. Three molariform patterns can be observed during megatheriine evolution in relation to tooth compression and loph or lophid orientation. Middle Miocene Megatheriinae occur only in the western quarter of South America. These giant ground sloths could have used the Andes as a "dispersion-route" to disperse southward/northward from Colombia/Patagonian Argentina before colonizing eastern areas of Andean South America (Bolivia, Venezuela, north and east of Argentina) during the late Miocene and early Pliocene.