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

The Archaeopithecidae is a very poorly known group of native ungulates
from the Eocene of Patagonia (Argentina), whose alpha taxonomy has
remained obscure since Ameghino’s times. It is traditionally considered as
a family representative of the Casamayoran (middle Eocene) South American
Land Mammal Age and it is thought to be morphologically close to the
notopithecids. After studying more than 200 specimens from several
institutions, including all the type specimens, a taxonomic overestimation
is established. Out of the six species considered originally as
archaeopithecids, Archaeopithecus rogeri is here recognized as the only
valid name and species; subsequent synonymies are proposed and previous
taxonomic hypotheses discarded. This exhaustive revision has permitted
improving the knowledge of A. rogeri and, for the first time, it has
revealed many craniodental characters which allow amending its diagnosis
and differentiating this taxon from other Eocene notoungulates.
Archaeopithecus rogeri is a small-sized taxon characterized by its
complete and rooted dentition, which is relatively higher than that of
other contemporaneous short-crowned notoungulates and shows ontogenetic
variation in size and morphology. The body mass range of A. rogeri
(1.4–2.5 kg) is comparable to those of notopithecids and some small
hegetotheriids. The phylogenetic analysis shows A. rogeri is not directly
related to any family within Notoungulata, appearing into a polytomy, as a
basal taxon of typotherians. The biochronological range of A. rogeri is
adjusted to Vacan (middle Eocene) through the Barrancan subages (late
middle Eocene); older (Riochican, late early Eocene) and younger
(Mustersan, late Eocene) records remain to be confirmed.