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Journal of Paleontology 91(6):1272–1295


separating incisors and canine, and between the canine and first premolar. Conic-shaped incisors and canine and the presence of diastemata distinguish Archaeopithecus from notopithecids, oldfieldthomasiids, and interatheres. From P1 to P4 (Figs. 2.1, 3.3, 4.1), the series is pre-


molariform, clearly distinguished from molars (see below). As a whole, the distal cingulum is high, wide, and well developed throughout the face, and it fuses with the metaloph in much- worn teeth; the mesial cingulum can be absent (Fig. 4.1, 4.3) or, when present, it is very narrow, near the base of the crown (Fig. 2.1); both cingula descend lingually. The parastyle, para- cone, and metacone folds form a very undulate ectoloph and delimit deep labial sulci. There are mesiolabial and central fos- settes in all premolars; on P1–2 the central fossette is small and circular, but on P3–4 it also has a labial portion that forms an isolated mediolabial fossette in worn teeth.Adistolabial fossette was only observed in P4. The mesial and distal borders of P2–4 are undulate. P1 and P2 (Figs. 2.1, 4.1) are triangular in outline, with


conical protocone, centrally placed. They lack a lingual sulcus; instead, there is a sulcus in the middle of the mesial face, as in Transpithecus (Vera, 2012a), connecting to the central fossette on unworn teeth (Fig. 2.7). P1 is much narrower than P2 (Table 1), but the difference is not so significant between P2 and P3–4; P1 has a narrow and mesiodistally enlarged central fossette (Fig. 2.7) and a parastyle fold, in contrast to other notoungulates (e.g., Notopithecus, Colbertia) in which the P1 is much reduced or canine-like. In addition, P1 is non-overlapping by C and P2 (Fig. 3.3), differing from typotherians. P3 is very similar to P1–2, but differs in having a lingual


sulcus dividing the protocone column in two lobes (Figs. 2.7, 4.2), although in some cases, the lingual sulcus is absent (Figs. 2.1, 4.1). A smooth sulcus in the mesial face is also observed in some specimens (Fig. 2.7). P4 has a wider protocone than P3, lacks the characteristic


triangular shape of the preceding premolars, and its mesial face can be singularly concave (Fig. 2.3, 2.11). The lingual sulcus is deep, forming two well-folded (Fig. 4.2) or softly folded (Figs. 2.4, 3.3) columns. InAMNHFM28841, the paracone and metacone folds are not as undulate as in other specimens (Fig. 2.7). There are mesio- and distolabial fossettes, the latter being the shallowest and the first one to disappear. The central fossette can be circular or elongated and has a narrow labial extension; in some cases, there are internal crests in the central fossette and the mesial extension can be also variable in shape (Fig. 4.4). As the wear advances in P2–4, the metaloph starts to con-


nect with the distal cingulum at a middle point (Fig. 4.1, 4.2), forming two small pits, lingually and labially to the union; the lingual pit, just posterior to the protocone, is deeper than the labial pit and becomes a shallowfossette when worn (Fig. 2.11). In a very old individual (AMNH FM 28782; Fig. 3.3), M1 shows only the central fossette, while P2 and P3 also have a mesial fossette. Compared with the premolars, the molars are squared or


rectangular in outline, depending on the wear stage.M1 and M2 are very similar to each other, and it is difficult to identify them among isolated teeth. Unworn or very little worn molars have the central valley completely open on the lingual face and


separating protocone from metacone (SW = 1 in Fig. 5.1). When wear increases, these lingual cones fuse through a crest (entoloph), isolating the central fossette, and a sulcus on the lingual face is formed, which differentiates protocone and metacone columns (SW = 2 in Fig. 5.1). This peculiarity is shared with some notopithecids (Vera, 2012a, 2012b; Vera and Cerdeño, 2014). On P4 and molars, the central fossette is mesiodistally elongated and has a narrow labial projection, which extends from the most anterior part of the central fossette in the M1 and from the middle part on M2 and M3 (Fig. 4.1). This labial projection becomes isolated as well, separated from the central fossette and forming an independent mediolabial fossette (Fig. 3.3) or internal fossette in Archaeohyrax suniensis (Billet et al., 2009). However, in Archaeopithecus, the isolation of this fossette seems to be independent from the increase of wear. There are much-worn specimens preserving the labial projection united to the central fossette (Figs. 2.15, 4.5, 4.6) and little-worn specimens showing the mediolabial fossette com- pletely separated from the central part (Fig. 4.7, 4.9). As with the premolars, the distal cingulum in molars is much more devel- oped than the mesial cingulum. M1–2 have hypocone more developed than protocone and lingually protruding (Fig. 4.8, 4.12), a feature also described for the notopithecid Antepithecus (Vera and Cerdeño, 2014; Vera, 2016), but in contrast to noto- pithecids, the protoloph-protocone are inclined and curving posteriorly in Archaeopithecus; there are some exceptions, however, in which the protocone protrudes lingually more than the hypocone, giving a ‘bilobed’ shape (Fig. 4.10). In some specimens (Fig. 4.12), M1 has a small ‘cuspule’ at the base of the sulcus between paracone and metacone, such as occurs in Notopithecus (Vera, 2013b). Besides the ‘complex’ central fossette, molars have mesio- and distolabial fossettes, which are irregular in shape and similarly sized. The occlusal surface shows the typical ‘face’ described for other groups of notoun- gulate, with fossettes occupying the eyes, mouth, and nose of this virtual face. These fossettes disappear in much-worn spe- cimens (Fig. 3.3; SW = 3 in Fig. 5.1). The ectoloph is not as undulate as on premolars. The M3 is characterized by its trapezoid shape, with the


distal face narrower than the mesial face, producing a distally inclined labial face (Fig. 4.13); it differs from notopithecids, oldfieldthomasiids and other Eocene notoungulates in having a developed hypocone. The protocone is wider and more devel- oped than the hypocone (Fig. 4.11, 4.13), whereas the opposite condition is observed in M1–2; in some cases, the protocone is pointed (Fig. 2.13). The wider protocone causes the central valley to be displaced distally. The mesial cingulum is low and short (Fig. 2.14), little to moderately developed, although also it can be absent (Fig. 2.13). The distal cingulum is as well devel- oped as in M1–2, but differs in being more convex distally. The general pattern of fossettes is similar to that on M1–2: two labial fossettes, and the central fossette formed by two transverse and vertical parts; occasionally small fossettes form when the mesial and distal cingula merge with the occlusal surface. In worn spe- cimens (Fig. 2.12), M3 assumes a nearly square outline and sev- eral fossettes are formed: the mesiolabial and distolabial fossettes, the shallow fossette between the mesial cingulum and protoloph, and a deeper fossette between the distal cingulum and metaloph, just below the distolabial fossette.


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