Implication of the presence of Megathericulus (Xenarthra: Tardigrada: Megatheriidae) in the Laventan of Peruvian Amazonia

• Autores: Pujos, François Roger Francis; Salas Gismondi, Rodolfo; Baby, Guillaume; Baby, Patrice; Goillot, Cyrille; Tejada, Julia; Antoine, Pierre Olivier
• Año de publicación: 2013
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Xenarthra; Megatheriidae; Western Amazonia; Plesiomorphic Condition; Tardigrada; Megathericulos Patagonicus; Middle Miocene; Western Amazonia
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

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 South American Land Mammal Age - SALMA; 13.5–11.8 Ma) of the Amazonian Peru 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, the 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, strongly developed odontoid tuberosity, and astragalus with prominent odontoid process. The genus Eomegatherium Kraglievich is therefore restricted to the Huayquerian SALMA of Argentina and represented by a single species, E. nanum Burmeister. Megatheriinae constitute 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 westernmost part of South America. These giant ground sloths might have dispersed latitudinally 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.
Fil: Pujos, François Roger Francis. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Institut Français d’ Etudes Andines; Perú
Fil: Salas Gismondi, Rodolfo. Universidad Nacional Mayor de San Marcos. Museo de Historia Natural. Departamento de Paleontología de Vertebrados; Perú
Fil: Baby, Guillaume. Université de Toulouse; Francia
Fil: Baby, Patrice. Université de Toulouse; Francia. Centre National de la Recherche Scientifique. Laboratoire de Mécanismes de Transfert en Géologie; Francia
Fil: Goillot, Cyrille. Université de Toulouse; Francia. Centre national de la recherche scientifique. Laboratoire de Mécanismes de Transfert en Géologie; Francia
Fil: Tejada, Julia. Universidad Nacional Mayor de San Marcos. Museo de Historia Natural. Departamento de Paleontología de Vertebrados; Perú
Fil: Antoine, Pierre Olivier. Université Montpellier. Institut des Sciences de l’Evolution; Francia