Ouranopithecus macedoniensis, (Bonis, Bouvrain, Geraads & Melentis, 1974) (Bonis, Bouvrain, Geraads & Melentis, 1974)

Koufos, George D., Plastiras, Christos-Alexandros, David, Constantine N. & Sagris, Dimitrios, 2023, The Late Miocene hominoid Ouranopithecus macedoniensis (Bonis, Bouvrain, Geraads & Melentis, 1974): maxillary deciduous dentition and virtual reconstruction of the unerupted permanent teeth, Comptes Rendus Palevol 22 (33), pp. 667-688 : 674-680

RESULTS

DESCRIPTION OF THE DECIDUOUS DENTITION

Upper deciduous canine

The dC1 is well preserved, missing a small part of its distolingual basal margin ( Fig. 2C, F, I). It is small and low with a rounded occlusal crown outline (index-a = 101.4; Table 4 ). Across the mesial margin of the crown there is a stripe-like enamel wear facet from the apex to the base, where it merges with a rounded dentine pit ( Fig. 2G, red dotted-line). The mesial enamel wear facet probably corresponds to a mesial crest, that wears away, and the rounded basal dentine pit to a very small mesial cingular cusplet. The distal margin of the crown is less worn; there is a narrow and short dentine pit, starting from the rounded one at the apex and extending over the distal margin ( Fig. 2I, red dotted-line). The buccal wall of the crown is mesiodistally curved and featureless ( Fig. 2B, E). The lingual cingulum is prominent and forms a narrow ledge across the lingual margin of the crown; it is slightly damaged in the distal part ( Fig. 2C, F, I). A weak distal pillar extends from the base towards the apex of the crown and ends almost at the middle height of the crown. The basal part of this pillar is worn and forms a dentine pit of undermined shape because the tooth is damaged in this part (the triangular-shaped pit shown in Figure 2I is not the original one). Mesial to this dentine pit there is another elliptical pit limited to the cingulum ( Fig. 2I). There is also a rudimentary mesial pillar and a shallow basin between the two pillars. The poorly preserved part of the root indicates that it is elongated and less stout in relation to the crown ( Fig. 2B, E). The preserved buccal height of the root is 6.8 mm and that of the crown 7.2 mm.

Upper deciduous premolars

The dP3 is well preserved and moderately worn ( Fig. 2J). The outline of the occlusal crown is trapezoidal. It is truncated mesiolingually and the buccal mesiodistal length is much longer than the lingual length. Paracone and metacone, although worn, are almost equal and separated by well-developed occlusal and buccal grooves. The paracone has a small and round dentine pit on its apex, while the metacone has a trace of enamel wear facet ( Fig. 2J). Despite the wear, a small parastyle can be seen in the mesiobuccal corner of the crown, separated from the paracone by a faint vertical groove on the buccal wall ( Fig. 2E). The protocone is worn and there is a rudimentary hypocone in the distolingual corner of the tooth, separated from the protocone by a weak lingual vertical groove; a very small dentine pit is visible at its apex ( Fig. 2C, F, red arrow). A mesiodistal groove separates the buccal cusps from the lingual ones. The distal fovea is short and weak, and the cingulum is absent.

The dP4 is crushed mesiolingually and lacks a small enamel peel ( Fig. 2C, F, K). The occlusal outline of the crown is sub-squared and less truncated mesiolingually than dP3. The paracone and metacone are equal in size, low, and separated by an occlusal and buccal groove. There is no parastyle. The protocone is large and separated from the smaller hypocone by a deep occlusal and a distinct buccal groove. Both protocone and paracone are poorly worn and retain a small dentine pit at their apex.Two low crests run from the apex of the protocone to the paracone and metacone, forming a large trigon basin. Another small crest connects the hypocone and the metacone. The distal fovea is short, broad, and unworn. There are no traces of cingulum.

DESCRIPTION OF THE PERMANENT DENTITION

The upper permanent canine and the third and fourth premolars are still into the maxillary bone. These teeth are unworn, and it is interesting to have access to their full morphology, given that unworn teeth of this species were previously unknown. They will also help in the classification and sexing of the specimens studied. They have been virtually reconstructed using aµCT scan ( Fig. 3) and we have produced physical casts using a 3D printer. The present description of these teeth is based on their virtual reconstruction ( Fig. 3) and casts. The dimensions of the permanent teeth were measured on both casts and scans.

Upper permanent canine

The C1 is small with triangular external profile ( Fig. 3) and almost rounded occlusal outline; the index-a is 102.8 ( Table 4 ). The crown is low, the maximum buccal height is 12.1 mm. The buccal wall is curved mesiodistally and lacks any feature as well as the cingulum. A mesiolingual groove runs from the base to the apex, it is narrow and situated more lingually. The distal margin of the canine is more inclined distally than mesially. Lingually, the cingulum is prominent, forms a horizontal surface, like a shelf. The lingual wall of the main cusp is triangular and perpendicular to the cingulum. The distal margin of the mesiolingual groove and that of the distal margin of the tooth form a triangular basin-like feature in the distolingual part of the tooth. A small and weak pillar divides it into two smaller parts, the mesial being larger than the distal one.

Upper permanent premolars

The P3 has an elliptical crown outline with the mesiodistal length shorter than the buccolingual one ( Fig. 3). It bears two cusps separated by a mesiodistal groove; the buccal cusp is larger than the lingual one. A weak parastyle, like a small prominence, is present at the mesiobuccal corner of the tooth, giving a slight asymmetry to its occlusal crown outline. The buccal wall is curved mesiodistally and featureless. The lingual cusp is low and its base projects lingually. The mesial and distal marginal ridges are well developed. The occlusal surface is wrinkled, and the cingulum absent. The P4 is broken, lacking its buccal half ( Fig. 3). The preserved part bears a small lingual cusp, while the remains of the buccal one suggests that it was larger and higher. The enamel of the occlusal surface is wrinkled and the cingulum absent.

Upper permanent molars

The M 1 is well preserved and slightly worn, lacking its roots ( Figs 2L; 3). The occlusal outline of the crown is squared, and the main cusps are low. The paracone and metacone are almost equal in size and height, separated by a deep groove on the occlusal crown and the buccal wall. These two cusps and the protocone form a large and deep basin. The protocone dominates the crown and it is separated from the hypocone by a weak occlusal groove and a deep lingual one. The mesial fovea is relatively long, wide, and deep. The distal fovea is smaller and less deep. Remains of enamel wrinkles are present on the cusps of the distal part of the tooth. The cingulum is absent.

COMPARISON WITH EXTANT HOMINOIDS

The comparison with extant hominoids is based on recent material studied in NHML, NMHS, and DPUT. Unfortunately, the sample of the comparative deciduous teeth lacks sex indications. The dental measurements of the deciduous teeth used for comparison are given in Table 1 .

Compared to Gorilla Geoffroy Saint-Hilaire, 1852 , the dC1 of O. macedoniensis is smaller, lower, less pointed, more reduced relative to the length of the deciduous premolar row and has a rounded occlusal crown outline. The dP 3 is smaller with a trapezoidal occlusal crown outline, a distinct metacone (absent in Gorilla ), a smaller parastyle, and no cingulum. The dP4 is smaller, has a relatively low crown with a more squared outline of the occlusal crown, smaller cusps, smaller mesial and distal foveae, and lacks a cingulum ( Figs 4B, C; 5; 6; Table 4 ).

The dC1 of O. macedoniensis compared to that of Pongo Lacépède, 1799 is shorter, but its buccolingual length is within the ranges of variation for Pongo ; it is more reduced relative to the length of the premolar row, with more curved mesiodistally buccal wall and with a rounded occlusal crown outline. The dP3 is similar in size to Pongo , but it differs in that it has a smaller parastyle, a trapezoidal outline of the occlusal crown, a metacone, a rudimentary hypocone and no cingulum. The size of dP4 is similar to that of Pongo , but it differs in that it has a relatively smaller metacone and no cingulum ( Figs 4B, C; 5; 6; Table 4 ).

Compared to Pan , the dC1 of O. macedoniensis is shorter and wider, lower, more reduced relative to the length of the premolar row, with rounded occlusal crown outline. The dP3 is larger and differs in having smaller parastyle, metacone, trapezoidal occlusal crown outline and absence of cingulum. The dP4 is larger, with lower cusps and absence of cingulum ( Figs 4B, C; 5; 6; Table 4 ).

The dC1 of O. macedoniensis is larger compared to Homo , slightly more reduced relative to the length of the premolar row, with a more rounded occlusal crown outline, more mesiodistally curved buccal wall and more developed lingual cingulum. The dP3 is larger with a small parastyle and it has slightly less squared occlusal crown outline. The dP 4 of O. macedoniensis has less squared occlusal crown outline and larger size ( Figs 4B, C; 5; 6; Table 4 ).

COMPARISON WITH EXTINCT HOMINOIDS

Proconsul Hopwood, 1933 is the earliest known Miocene hominoid. The latest revision of the material referred to this genus allowed its separation into two genera, Proconsul and Ekembo McNulty, Begun, Kelley, Manthi & Mbua, 2015 ( McNulty et al. 2015). According to these authors, the material from Rusinga and Mfagano ( Kenya) described by Andrews (1978) belongs to E. heseloni (Walker, Teadford, Martin & Andrews, 1993) and that from Songhor ( Kenya) to P. major Le Gros Clark & Leaky, 1950 , while the remaining material needs revision. Another Proconsul species named P. meswae Harisson & Andrews, 2009 is known from Meswa ( Kenya). The comparison of O. macedoniensis is therefore based on: 1) P.meswae (maxillary fragment with dC1-dP4, KNM-ME 11, cast housed in NHML; Fig. 7P) and the descriptions of Andrews et al. (1981) and Harrison & Andrews (2009); and 2) P. major from the descriptions and illustrations of Andrews (1978: 102, pl. 4, fig.3).

Compared to P. meswae , dC1 of O. macedoniensis is larger, lower, more reduced relatively to the length of the premolar row, with a slightly more rounded occlusal crown outline (subrounded in P. meswae ; Table 4 ), a wider lingual cingulum, (narrow in P. meswae ; Harrison & Andrews 2009) and bears two pillars on the lingual wall (one in P. meswae ; same authors). McNulty et al. (2015) and Pickford et al. (2020) mention a “blade-like” tip or “burin-like” in both the deciduous and permanent upper canine of Proconsul ; this feature is absent in O. macedoniensis . The larger size, the trapezoidal occlusal crown outline (triangular in P. meswae , Fig. 7P), the presence of metacone and rudimentary hypocone, the smaller parastyle and the absence of cingulum distinguish the dP3 of O. macedoniensis from that of P. meswae . The dP 4 is larger, has a more squared occlusal crown outline and lacks the cingulum ( Figs 5-7P; Table 4 ). The dC1 of O. macedoniensis is larger compared to that of P. major ( Fig. 5) and relatively reduced compared to the length of the premolar row, with a rounded occlusal crown outline and no buccal cingulum. The smaller size, the presence of metacone and hypocone and the absence of cingulum in the dP3 of O. macedoniensis distinguish it from P. major . The dP4 of O. macedoniensis differs with a larger size, a larger hypocone, a more squared occlusal crown outline and the absence of a cingulum ( Fig. 5; Table 4 ).

The comparison with Ekembo is based on the cast of E. heseloni (KNM-RU 1803, housed in NHML; Fig. 7Q) and the descriptions of McNulty et al. (2015). The dC1 of O. macedoniensis is larger compared to that of E. heseloni , more reduced relatively to the length of the premolar row, and with a more rounded occlusal crown outline. The dP3 is larger, has a trapezoidal outline of the occlusal crown, a metacone, a rudimentary hypocone and no cingulum. The dP 4 is larger, has a more squared outline of the occlusal crown and does not have a cingulum ( Figs 5-7Q; Table 4 ).

The comparison of O. macedoniensis with Griphopithecus alpani is based on the casts of several isolated teeth from Paşalar, Turkey, housed in NHML; this sample lacks dC1. The material was studied by Mortzou & Andrews (2008), and all referred to G. alpani . Compared to G. alpani , the dP3 of O. macedoniensis is larger with a metacone, a rudimentary hypocone and without cingulum. The dP4 is larger, has a more squared occlusal crown outline and lacks the cingulum ( Figs 5-7 B-O; Table 4 ).

The comparison of O. macedoniensis with Hispanopithecus laietanus Villalta Comella & Crusafont Pairó, 1944 is based on some casts from Can Llobateres I, II, Spain ( Fig. 7 R-T) and the descriptions of Alba et al. (2012). Compared to H. laietanus , the dC1 of O. macedoniensis is larger, and more reduced relative to the length of the premolar row, with a more rounded occlusal crown outline, and without the large distolingual basin-like groove of H. laietanus . In addition, H. laietanus has a strong lingual ridge extending to the middle of the canine height, which is weaker in O. macedoniensis . The dP 3 is larger and it has a trapezoidal occlusal crown outline, a metacone (in H. laietanus there is a crest in the position of the metacone), a rudimentary hypocone, and lacks the cingulum. The dP4 is larger with a more squared occlusal crown outline and lacks the lingual cingulum ( Figs 5-7 R-T; Table 4 ).

The comparison with Rudapithecus hungaricus Kretzoi, 1969 is based on the photos (no permission to publish the photos) of an undescribed isolated dP3 and another dP4 from Rudabanya, Hungary. The dP 3 of O. macedoniensis is larger with a trapezoidal occlusal crown outline (in R. hungaricus is sub-rectangular, MD<BL), a smaller parastyle, a metacone, a rudimentary hypocone, and absence of the cingulum. The dP4 is larger with more squared occlusal crown outline (in R. hungaricus is sub-rectangular, MD<BL), and without cingulum ( Figs 5; 6; Table 4 ).

Two species of Lufengpithecus are known from China L. hudienensis Ho, 1990 and L. lufengensis Xu, Lu, Pan, Qi, Zhan & Zheng, 1978 . A juvenile cranium of L. hudienensis (YV 0999) is known from the Yuanmou Basin, which preserves the deciduous dentition ( Ho 1990; Kelley & Gao 2012). The mesiodistal diameter of dC1 is longer than the buccolingual one in L. hudienensis ( Ho 1990: 315) , implying an elliptical occlusal crown outline, whereas it is rounded in O. macedoniensis . The dP3 has a triangular shape ( Ho 1990: fig. 4) with a prominent parastyle, unlike O. macedoniensis , which has trapezoidal occlusal crown outline, a very small parastyle, and a rudimentary hypocone. A juvenile cranium (ZT 299) of L. lufengensis is known from Southern China ( Ji et al. 2013: fig. 5). The cranium preserves only the dP4 which differs from that of O. macedoniensis in having a weaker hypocone, a shorter mesiodistal than buccolingual length, and a smaller size ( Figs 5; 6).

The comparison with Australopithecus afarensis Johanson et al. 1978 was based on the material from Hadar ( Ethiopia) and Laetoli ( Tanzania), ( Fig. 7 U-W) and on the descriptions and illustrations of White (1977, 1980) and Johanson et al. (1982). The dC 1 of O. macedoniensis has similar mesiodistal length to that of A. afarensis , but it is wider with rounded occlusal crown outline and more flattened mesiodistal buccal wall. The dP 3 of both species is of similar size, but that of O. macedoniensis has less squared occlusal crown outline, larger parastyle, rudimentary hypocone (in A. afarensis it is quite distinct and larger) and lacks a cingulum (a weak lingual cingulum is present in the dP3 of KNM-AL 333-86; Fig. 7U). The dP4 is slightly smaller and lacks a cingulum (a weak mesiolingual cingulum is present in the dP4 of KNM-AL 333-86), ( Figs 5-7 U-W; Table 4 ).

The dC 1 of O. macedoniensis is larger compared to a cast of Australopithecus africanus Dart, 1925 (Taung skull; Fig. 7X), but both have similar occlusal crown outlines (rounded) and relative size compared to the length of the premolar row. The dP3 has similar size, a less squared occlusal crown outline, and a more developed parastyle. The dP4 of O. macedoniensis is slightly longer and narrower and lacks the crest connecting the hypocone with the mesial margin ( Figs 5-7X; Table 4 ).