Phylogenetic revision of the South American notopithecines (Mammalia: Notoungulata)

Abstract

A phylogenetic analysis of all Eocene taxa assigned to Notopithecinae has been conducted, evaluating relationships amongst notopithecines, basal interatheriids and Interatheriinae. Other groups of native ungulates were also included. New dental and postcranial characters are considered with respect to previously published data; some characters are evaluated in notoungulates for the first time. Two different searches were performed under parsimony and equal weights. The inclusion of postcranial characters strongly influenced tree topology. The most significant result of the phylogenetic analysis was the identification of a novel monophyletic group, including species traditionally grouped as Patagonian Notopithecinae. The 'notopithecid' name is linked to the new clade defined as the clade stemming from the most recent common ancestor of the species Notopithecus adapinus, Antepithecus brachystephanus, Transpithecus obtentus and Guilielmoscottia plicifera. This phylogeny supports the main morphological differences of the new clade with respect to Interatheriinae Interatheriidae. In consequence, a diagnosis is proposed based on phylogenetic results, to which some other morphological characters are added. The Chilean basal interatheriids Johnbell and Ignigena as well as Punapithecus (Argentinean Puna) are excluded from the notopithecid clade, implying biostratigraphical and biogeographical changes. Notopithecid distribution now becomes restricted to the middleÀlate Eocene part of the Sarmiento Formation outcropping in central Chubut and north-east Santa Cruz provinces, Argentina. Other extra-Patagonian records of notopithecids are not confirmed. The resulting phylogeny resolves some relationships within basal interatheriids differently from previous analyses. Interatheriinae is not recovered as a monophyletic group, and Oldfieldthomasiidae and Henricosborniid are paraphyletic. The position of the Archaeopithecidae Acropithecus rigidus is controversial; it appears at the base of the Typotheria lineage or in the notopithecid clade, but systematic taxonomy and phylogenetic relationships amongst members of Archaeopithecidae remain to be established.

Ontogenetic and life history trait changes associated with convergent ecological specializations in extinct ungulate mammals

“…However, even if evergrowing teeth and modifications of the pattern of dental eruption show an almost perfectly replicated codistribution, some differences still exist in their timing of appearance. The geologically earliest occurrence of this modified eruption sequence (i.e., faster eruption of third molars) was reported for Interatheriidae and occurred during the Late Eocene (approximately 35 Ma) (36,37). This modification preceded a significant crown height increase in the clade (Fig.…”

Patagonian Eocene Archaeopithecidae Ameghino, 1897 (Notoungulata): systematic revision, phylogeny and biostratigraphy

“…A phylogenetic analysis was performed based on a modified version of Vera's (2016) matrix. It consists of 29 terminal taxa and 87 morphological characters (0-57, upper and lower dentition; 58-70, skull and mandible; and 71-86, postcranium).…”

“…However, there are a few older (Riochican SALMA) and younger (Mustersan SALMA) records, yet to be confirmed, that could modify first and last appearances (see below). Little is known about this group-its systematic background is complicated, being frequently related in the literature and collections to notopithecids, which is another Patagonian group of Eocene notoungulates that recently has been revised (Vera, 2013b(Vera, , 2016. This emphasizes the difficulty in differentiating archaeopithecids from notopithecids based on dental morphology, as well as from other taxa such as Oldfieldthomasiidae or Henricosborniidae, or an "oldfieldthomasiid-archaeopithecidnotopithecine complex" as Simpson (1967b, p. 63) expressed.…”

“…Since Simpson's work (1967b), the members of this group have not been subjected to systematic revision or other detailed studies, and Acropithecus rigidus is practically the only species considered in subsequent studies including Archaeopithecidae (Cifelli, 1985(Cifelli, , 1993Hitz et al, 2006;Reguero and Prevosti, 2010;Billet, 2011;Elissamburu, 2012;Vera, 2016), most likely because the specimens of Acropithecus are represented by much more complete material that the type of Archaeopithecus.…”

“…2B), Acropithecus rigidus is nested into the notopithecid clade as the sister taxon of Guilielmoscottia plicifera and Transpithecus obtentus. Based on morphological characters, Vera's (2016) analysis was the first to suggest a possible link between archaeopithecids and notopithecids from a phylogenetic point of view.…”