Archaeopithecus, Ameghino, 1897

Tejedor, Marcelo F., Goin, Francisco J., Gelfo, Javier N., López, Guillermo, Bond, Mariano, Carlini, Alfredo A., Scillato-Yané, Gustavo J., Woodburne, Michael O., Chornogubsky, Laura, Aragón, Eugenio, Reguero, Marcelo A., Czaplewski, Nicholas J., Vincon, Sergio, Martin, Gabriel M. & Ciancio, Martín R., 2009, New Early Eocene Mammalian Fauna from Western Patagonia, Argentina, American Museum Novitates 3638, pp. 1-43 : 25-27

Archaeopithecus cf. A. rogeri Ameghino (1897)

Several maxillary and mandibular fragments (e.g., LIEB-PV 1625 to 1628), as well as isolated teeth (e.g., LIEB-PV 1629) referred to this family have been found in La Barda and Laguna Fría. The Archaeopithecidae is based on Archaeopithecus rogeri Ameghino (1897) , of unclear stratigraphic provenance, probably Barrancan, and Acropithecus rigidus Ameghino (1901) , from Cañadón Vaca (Vacan). Based on the morphology of the ectoloph and for the presence of a strong anterolingual cingulum in the premolars, the materials collected at the Paso del Sapo localities are closely related to Archaeopithecus rogeri , but the species assignment is still uncertain.

Family Interatheridae ( Ameghino, 1897) Subfamily Notopithecinae ( Simpson, 1945)

This subfamily includes the oldest and more generalized members of the Interatheriidae but since this grouping is mainly recognized on the basis of plesiomorphic characters, its taxonomic status is debated. The notopithecines are typotheres of small size, probably browsers and, in part, ecologically equivalent to the members of the families Oldfieldthomasiidae and Archaeopithecidae . Some Notopihecinae (e.g., Notopithecus ) show craniodental and postcranial characters convergent with those found in lemuriform primates from the early Tertiary of the Northern Hemisphere, thus explaining why Ameghino characterized this group as ‘‘southern monkeys’’.

The Notopithecinae appeared in the fossil record in the uppermost levels of the Riochican from Bajo Palangana, eastern Chubut province ( Simpson, 1967b), and its youngest record came from the Tinguirirican of central Chile ( Flynn et al., 2003). Among the Eocene faunal associations of Patagonia, the notopithecines are abundant with five genera recognized: Notopithecus Ameghino (1897) , for the Riochican and Casamayoran of Patagonia, and with some doubts for the Eocene of Bolivia; Antepithecus Ameghino (1901) and Transpithecus Ameghino (1901) from the Casamayoran (s.l.) of Patagonia; Guiliermoscottia Ameghino (1901) from the Mustersan of Patagonia; and Punapithecus López and Bond (1995) from levels referred to the Mustersan in Catamarca, northwestern Argentina.

Gen. et sp. indet. J

A few isolated teeth that may be attributable to the Notopithecinae were collected at Laguna Fría. Some of these are probably related to the genus Notopithecus (e.g., LIEB- PV 1655, an isolated lower p3) but a broader systematic revision is needed.

Family Isotemnidae ( Ameghino, 1897)

The Isotemnidae are moderate to large ungulates characterized by having large canines and a generalized molar pattern for the Toxodontia. This family is represented by numerous maxillary and mandibular fragments and isolated teeth in both localities of Paso del Sapo.

Isotemnus sp. Ameghino (1897)

Figure 7H, I

There are two specimens, a left maxilla with P4–M3, slightly worn (LIEB-PV 1647) and a right maxilla also with P4-M3 (LIEB-PV 1646; fig. 7h, i), with transverse molars, well-developed, columnar metacone and lingual cingulum absent. These traits characterize Isotemnus and clearly differ from Pleurostylodon Ameghino (1897) . Also, there are several mandibular fragments (LIEB-PV 1650 to 1653) referred to the genus Isotemnus , based on the structure of the metaconid, which is not oriented posteriorly and thus the talonid basin is open. The lower molars have better developed lophids than Isotemnus ctalego from Cañadon Hondo (Itaboraian) and Isotemnus sp. from the Ernestokokenia chaishoer zone of Bajo Palangana. This is indicative of a post- Riochican evolutionary stage. In Patagonia, the genus Isotemnus is also recorded in Riochican and Vacan levels.

Order Astrapotheria ( Lydekker, 1894) Family indet. Gen. et sp. indet. K

A left m1 or m2 (LIEB-PV 1623) recovered at Laguna Fría is attributed to the Astrapotheria . However, the family attribution is difficult because the morphology resembles that in the genus Trigonostylops Ameghino (1901) ( Astrapotheria , Trigonostylopidae ) as well as that in Tetragonostylops Price and Paula Couto (1950) ( Astrapotheria , Astrapotheriidae ). Both genera can be recognized by their upper molariforms, but the lowers lack diagnostic characteristics. The species of Trigonostylops are known from the Riochican through the Mustersan of Patagonia, while Tetragonostylops comes from the Itaboraian of Brazil and Vacan of Argentina.

Order? Astrapotheria Gen. et sp. indet. L

Among the materials from Laguna Fría, there is a right maxillary fragment with part of the hypertrophied and compressed canine that may be attributable to the Astrapotheria (LIEB-PV 1624) , but its more precise attribution is doubtful. We are unable to refer this specimen to any other South American order of ungulates.

Figures

Fig. 7. South American native ungulates from Laguna Fría (LF) and La Barda (LB). A, LIEB-PV 1612, Didolodontidae, gen. et sp. nov., right m2–3; B, Asmithwoodwardia subtrigona, LIEB-PV 1636, left M2; C, Asmithwoodwardia subtrigona, LIEB-PV 1617, right m2; D, Spartnotheriodontidae, Gen. et sp. indet. G, MLP-66-V-12-2, right maxillary fragment with three molariforms (P4–M2?) (LF); E, Henricosbornia lophofonta, LIEB-PV 1633, right maxilla with P4–M2 (LB); F, Othnielmarshia lacunifera, LIEB-PV 1618, right maxilla with M1–3 (LF); G, Edvardotrouessartia sola, LIEB-PV 1619; right maxilla with P2–4 (LF); H, Isotemnus sp., LIEB-PV 1646, right maxilla with P4–M3 (LF); I, Isotemnus sp., LIEB-PV 1659, left m2 (LF). Scale bar 5 1 mm.