New anatomical and phylogenetic data on the late Neogene armadillo Macrochorobates scalabrinii (Chlamyphoridae, Euphractinae)

Abstract

Macrochorobates is a genus of big sized Euphractinae armadillos restricted to the late Neogene of Argentina. It includes the species M. scalabriniiand M. chapalmalensis. Particularly, M. scalabriniiis recorded in the late Miocene (Chasicoan-Huayquerian) of Buenos Aires, La Pampa, and San Juan provinces, and the late Miocene-early Pliocene (Messinian-Zanclean) of Tucumán, La Rioja, Catamarca, and Jujuy provinces. Most specimens are represented by isolated osteoderms, while more complete specimens are quite rare. We analyze here the most complete dorsal carapace (FMNH-P14510) and skull (FMNH-P14360) known for the genus, coming from late Miocene-early Pliocene levels of Andalhuala Formation outcropping at Puerta de Corral Quemado and Santa María Valley localities respectively, in Catamarca Province. This study provides the first detailed anatomical description of the skull and increases the knowledge of the dorsal carapace morphology. These aspects allowed to include this taxon for the first time into a morphological phylogenetic analysis. Obtained results support its inclusion within Euphractinae, revealing a close affinity with other late Neogene genera, and a sister group relationship with the genus Macroeuphractus, based on: a) anterior teeth oriented obliquely to the long axis of toothrow; b) very flattened braincase with parietals dorso-ventrally compressed; c) well developed sagittal crest; d) large and wide orbits; e) underdeveloped scapular shield of the dorsal carapace; and f) mobile osteoderms with very deviated central figures and undivided peripheral figures. Geographic distribution seem to vary with its biochron, as older records come from Pampean Region while most modern ones come from Cuyo and NOA regions.