Implication of the presence of Megathericulus (Xenarthra: Tardigrada: Megatheriidae) in the Laventan of Peruvian Amazonia
Abstract
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.
Additional Information
We thank the following colleagues for facilitating access to fossil collections under their care: B. Simpson (FMNH), A. Kramarz (MACN), M. Reguero and S. Bargo (MLP), C. Argot, C. de Muizon, and P. Tassy (MNHN), and N. Valencia (MUSM). Special thanks to D. Brandoni (CICYTTP-CONICET) for information on Middle Miocene Megatheriinae from Argentina, C. I. Montalvo (UNLPAM) who allowed us to mention and present the GHUNLPAM 8010 specimen from La Pampa, and G. De Iuliis (ROM) for pictures of La Venta specimens. M. Superina (IMBECU, CCT-CONICET-Mendoza) improved linguistic aspects of the text. We thank C. de Muizon and an anonymous reviewer for their interesting comments and suggestions which helped improve the manuscript. This research project was possible thanks to the IRD-Perupetro S.A. research agreement, and supported by IRD (UR 154), French INSU-CNRS programmes DyETI (Dynamique et Evolution de la Terre Interne) and ECLIPSE II (Evolution néogène du Bassin amazonien occidental et biodiversité: relations avec la géodynamique andine), and post doctoral fellowships of the IFEA (2003–2006) and CONICET (2008–2010) for one of us (F.P.).Additional details
- Eprint ID
- 119962
- Resolver ID
- CaltechAUTHORS:20230313-433389000.8
- Centre National de la Recherche Scientifique (CNRS)
- UR 154
- Institut de Recherche pour le Développement (IRD)
- Institut national des sciences de l'Univers (INSU)
- Institut français d'études anatoliennes (IFEA)
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
- Perupetro S.A.
- Created
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2023-03-15Created from EPrint's datestamp field
- Updated
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2023-03-15Created from EPrint's last_modified field