A new phylogenetic interpretation of the Notopithecinae (Mammalia, Notoungulata)

VERA, BÁRBARA

Mendoza

Congreso; IV International Paleontological Congress; 2014

The families Notopithecidae and Archaeopithecidae (Notoungulata) were created by Ameghino to include Eocene taxa from central Patagonia, Argentina. These extinct mammals have brachydont dentition and are among the smallest known notoungulates. The systematic of both groups is complex. Simpson established numerous synonyms and proposed a new rank for the notophithecids, regarding them as the Subfamily Notopithecinae, including the oldest and more generalized members of the Family Interatheriidae. Besides, Simpson also observed that they are morphologically very close to archaeopithecids, but he considered Archaeopithecidae to be separate from Notopithecinae. More recently, extra-Patagonian records have been described, including the notopithecine Punapithecus minor López and Bond from the Geste Formation (Catamarca and Salta provinces, Argentina), and the basal interatheriids Ignigena minisculus and Johnbell hatcheri Hitz et al. from the Abanico Formation (central Chile). The Interatheriidae, considered traditionally as a group of rodent-like notoungulates included in the Suborder Typotheria, have been the subject of several phylogenetic analyses focusing on the Interatheriinae; however, notopithecines, as well as archaeopithecids, have been practically neglected in most of them. A phylogenetic definition for Interatheriinae has been proposed, but no synapomorphies have been identified that unite Notopithecinae, which represents a paraphyletic assemblage and consequently is referred to as basal interatheriids. Concerning Archaeopithecidae, different authors have stated that they do not belong to Typotheria but rather constitute their sister group. The present revision of notopithecines and archaeopithecids yielded novel taxonomic modifications with respect to previous reviews. Based on these data, a phylogenetic analysis was conducted in order to examine for the first time the relationships of all taxa grouped under the name Notopithecinae. The results indicate that the Patagonian notopithecines (Notopithecus, Antepithecus, Transpithecus and Guilielmoscottia) plus the archaeopithecid Acropithecus form a monophyletic assemblage. On the one hand, this arrangement supports the main morphological differences observed between Notopithecinae and Interatheriinae; on the other hand, it supports a close relationship between notopithecines and archaeopithecids. The exclusion of the Chilean basal interatheriids and Punapithecus from the new monophyletic group has biostratigraphic and geographic implications because both were considered to represent the latest record of the group (early Oligocene) and occurrences of the group outside Patagonia. This new phylogenetic interpretation for notopithecines supports their exclusion from the Interatheriidae and regards them as a family as originally proposed by Ameghino. Studies in progress will provide more data on the close relationship of these ?notopithecids? and archaeopithecids, both of which could eventually be placed in the same family.