Kolpochoerus phillipi, Souron & Boisserie & White, 2015

Souron, Antoine, Boisserie, Jean-Renaud & White, Tim D., 2015, A new species of the suid genus Kolpochoerus from Ethiopia, Acta Palaeontologica Polonica 60 (1), pp. 79-96 : 82-90

Kolpochoerus phillipi sp. nov.

Figs. 1–3 .

Etymology: Named in honor of the late and great South African paleoanthropologist Phillip V. Tobias for his support of the Middle Awash research project, and in recognition of his work on African fossil hominids never losing sight of the importance of associated vertebrate faunas and their environmental context ( White 2012).

Type material: Holotype: MAT-VP-1/5 (housed at the ARCCH), partial cranium with alveoli for I1–I3, isolated I1 and I2, partial C, and P1–M3; associated mandible with i1, i2, alveoli for i3, partial c, and p2–m3) ( Figs. 1–3 ) . Paratype: MAT-VP-5/1 (housed at the ARCCH), left mandible fragment with p4, m2, m3 and alveoli for m1 ( Fig. 3B ). Type locality: Matabaietu Vertebrate Paleontology Locality One , Middle Awash study area, Afar Depression, Ethiopia .

Type horizon: “W” Formation, Unit 9 sandstone (in situ), Plio-Pleistocene, ca. 2.5 Ma.

Material.—Seven isolated third molars, here referred to Kolpochoerus cf. phillipi sp. nov. ( Table 1, Fig. 3C–I ): KL 234-1, KL 234-3-5, MAT-VP-5/2, Matabaietu area, Middle Awash study area, Ethiopia: KL 10-3, KL 24-1 b, KL 39-4, KL 73-1, Wilti Dora area, Middle Awash region, Ethiopia; “W” Formation, Plio-Pleistocene, ca. 2.5 Ma.

Diagnosis. —Differs from all species of Potamochoerus and Hylochoerus , but resembles Kolpochoerus , in the presence of a ventrally extended and laterally expanded zygomatic arch, as well as a marked angle separating the rostrum and the elevated neurocranium in lateral view. Differs from all species of Kolpochoerus except K. majus in the presence of mesiodistally compressed lateral pillars of the molars, and zygomatic arches oriented at a 40° angle to the sagittal plane in dorsal view in males; differs from K. deheinzelini , K. millensis , and K. cookei in having much larger and more complex teeth; differs from K. afarensis in having a dorsoventrally thickened mandibular symphysis, a more swollen mandibular body, less developed lower incisors, a less acute lower incisor arcade, more developed upper and lower canines, a less constricted parietal roof, and an anteroposteriorly elongated supra-canine flange (with the latter only being present in males); differs from K. limnetes in having a relatively shorter cranium, a rostrum retaining a constant width throughout, a narrower mandibular symphysis, and less symmetric and less complex m3 talonids; differs from K. olduvaiensis , K. paiceae , and K. phacochoeroides in having much shorter, lower and simpler third molars, unreduced premolars, an orbit located below the dorsal surface of the frontal, and a well-developed supra-canine flange in males; differs from K. majus in having a narrower mandibular symphysis, a more constricted parietal, near-parallel cheek tooth rows, and a strongly developed supra-canine flange in males.

Description. —The holotype cranium preserves the complete rostrum, most of the parietal roof, and the incomplete left zygomatic arch ( Fig. 1 ), but lacks the entire occipital bone and the ventral portion of the braincase. An isolated piece of the basicranium was found, but is poorly preserved and cannot be attached to the rest of the skull. Judging from the eruption of all of the teeth and the presence of heavy wear on the first two molars, the specimen represents an adult. It can furthermore be identified as a male, based on the presence of well-developed lower and upper canines, a strong supra-canine flange, a laterally inflated zygomatic arch, a strongly swollen mandibular body, and a long mandibular symphysis. Sexual dimorphism in canine size is well documented in the Suidae ( Harris and White 1979; Groves 1981; Made 1991; Cooke 2007), while the lateral expansion of the zygomatic arch in males occurs in several species of living and fossil African suids, including Hylochoerus , Kolpochoerus , and Metridiochoerus ( Harris and White 1979; Geraads 2004). Similarly, a dorsoventrally developed, crest-like supra-canine flange characterizes males of Potamochoerus and some species of Sus , such as S. celebensis ( Hardjasasmita 1987) , and is supposedly linked to the protection of the rhinarium muscles in species that fight using snout boxing ( Kingdon 1979).

In terms of overall size, the skull is close to the average size of Hylochoerus , slightly smaller than female specimens of K. majus , and much smaller than K. limnetes and the only known male specimen of K. majus (BOU-VP-25/107; Gilbert 2008; Table 3). As in other species of Kolpochoerus , the cranium is relatively tall compared to Potamochoerus and Hylochoerus , and further resembles K. majus and early specimens of K. limnetes , but not K. olduvaiensis , in being relatively short anteroposteriorly ( Fig. 4D ). The postorbital constriction is comparable to the average K. limnetes , being weaker than in most specimens of Potamochoerus and K. olduvaiensis , but stronger than in K. majus and Hylochoerus ( Fig. 4B , Table 3). The dental rows are almost parallel, unlike in K. majus in which the latter diverge anteriorly ( Fig. 4C ). The premaxilla is relatively wide transversely and inclined ventrally in lateral view, as in K. majus and K. limnetes . By contrast, the premaxilla is relatively narrow and more horizontal in Potamochoerus and Hylochoerus ( Fig. 4A ). In cross section, the rostrum is square, with vertical edges as seen in Potamochoerus and early specimens of K. limnetes ( Fig. 1C ). The transverse width of the rostrum remains constant along its entire length, unlike in K. limnetes in which the rostrum is widest somewhat posterior to the supra-canine flange and tapers anteriorly. As in Potamochoerus and early K. limnetes , the nasals overhang the maxilla in anterior view ( Fig. 1C ). In contrast to K. olduvaiensis and K. paiceae , the orbit is located below the dorsal surface of the frontal, as in K. afarensis , K. majus , and K. limnetes . In lateral view, the dorsal surfaces of the frontal and parietal are arched dorsally, more so than in K. afarensis , but similar to K. majus and early K. limnetes .

The supra-canine flange is elongated anteroposteriorly and developed dorsoventrally, resembling the condition seen in males of early Kolpochoerus limnetes , although in the latter the dorsal edge of the flange is less rounded in lateral view. By contrast, the ventral part of the flange is short anteroposteriorly in males of Potamochoerus , and greatly reduced with only a weak lateral crest and a shallow gutter in K. olduvaiensis , K. majus , and Hylochoerus ( Gilbert 2008) . The zygomatic arch strongly projects ventrally, and is oriented at a 40° angle to the sagittal plane in dorsal view. In the latter feature, the present material resembles females of K. majus from the Daka Member of the Bouri Formation (ca. 1 Ma; Gilbert 2008) and the site of Asbole (Busidima Formation, 0.8–0.6 Ma; Geraads et al. 2004a), although it differs from males of this species in its slightly more obliquely oriented and less laterally inflated zygomatic arch (see above; Gilbert 2008). By contrast, the angle of the zygomatic arch to the sagittal plane is close to 90°, and the zygomatic knob is usually covered with rugose bone in male specimens of K. afarensis , K. limnetes , and K. olduvaiensis . As in K. afarensis and early K. limnetes , the insertion scars for rostral muscles are relatively well marked in K. phillipi sp. nov., although less so than in Potamochoerus . In Hylochoerus and other species of Kolpochoerus , the muscle scars are reduced.

Upper dentition. —The upper dental formula is 3.1.4.3. The right I1 and I2 were found isolated ( Fig. 3A ), and resemble those of K. limnetes and K. majus . The upper canine is slightly triangular in cross section, much larger than in Potamochoerus , and much smaller than in males of K. limnetes and K. majus ( Table 3). There are no marked grooves as in the canines of male K. limnetes , K. majus , and Hylochoerus , and the ventral side of the tooth displays a strongly ribbed enamel band.As in Hylochoerus , the canine is oriented slightly anterodorsally, at an angle of approximately 45° to the sagittal plane of the cranium (in dorsal view). The total length of the cheek tooth row is similar to that of the largest specimens of Potamochoerus , K. afarensis , and the smallest specimens of K. limnetes and K. majus ( Table 3). The diastema between the upper canine and the premolars is relatively long compared to Potamochoerus , but within the range of K. majus , and relatively shorter than in

A 130 B 90

length 120 width 80

premaxillary 110

100

/ frontal width

70 60

/

width 90 parietal 50 40 premaxillary 80 x least 30

x 70 100

100 20

60 10

138 142 146 150 154 158 80 90 100 110 120 130 140 150 160 Angle C19 (°) Frontal width (mm)

C 170 D 120

width 160 115

palate 150

height 110

/

posterior 140 130

neurocranium

105 100 95

width 120 / 90 palate 110 width 85

frontal

anterior

100

90

x

100

80

75 x

100 80 70

30354045505560657075 262830323436384042 100 x posterior palate width / cheek teeth row length 100 x frontal width / cranial length Kolpochoerus phillipi sp. nov. Kolpochoerus olduvaiensis Kolpochoerus afarensis Potamochoerus porcus Hylochoerus meinertzhageni Kolpochoerus majus Kolpochoerus limnetes Potamochoerus larvatus the average K. limnetes and Hylochoerus ( Table 3). The upper premolars are similar in proportion and size ( Table 5) to those of the smallest specimens of K. limnetes and K. majus , but relatively wider, with a higher width/length ratio, than those of K. afarensis (especially P3). P1 is small, and separated from P2 by a small diastema ( Fig. 3A ). The ratio between the premolar and molar row lengths is relatively high (C16/C17*100 = 50), similar to Potamochoerus (average C16/C17*100 = 56; n = 63) and K. majus (average C16/C17*100 = 54; n = 12), and relatively higher than in the average K. limnetes (average C16/C17*100 = 44; n = 20). Both M1 and M2 are heavily worn, and fall within the range of K. afarensis , K. limnetes , and K. majus in terms of their size and proportions ( Table 5). Finally, M3 comprises two pairs of lateral pillars, followed by a strong terminal pillar and several small ectostyles ( Fig. 3A ), and resembles the corresponding teeth of K. afarensis , K. majus , and early K. limnetes from members B and C of the Shungura Formation ( Fig. 5B ). The wear pattern of the lateral pillars is simple, and similar to specimens of K. majus .

Mandible. —The holotype mandible is essentially complete ( Fig. 2 ). As in other species of Kolpochoerus and Hylochoerus , the cheek tooth rows are nearly parallel, in contrast to the more anteriorly convergent condition seen in Potamochoerus . The mandibular symphysis is dorsoventrally thick as in K. majus and K. limnetes , but unlike Potamochoerus and K. afarensis . As in K. majus , the mandibular symphysis is thinnest close to its anterior extremity ( Fig. 6D ). The symphyseal area is relatively narrow, with its width/length ratio (M4/

Kolpochoerus deheinzelini Kolpochoerus phillipi sp. nov. Kolpochoerus cf. phillipi sp. nov. Hylochoerus meinertzhageni Kolpochoerus millensis Kolpochoerus afarensis Kolpochoerus limnetes (all levels) Potamochoerus porcus

B, C, Kolpochoerus limnetes (from members

Kolpochoerus olduvaiensis Kolpochoerus majus D–F B, C, D–F of Shungura Formation) Potamochoerus larvatus

M3*100 = 75) falling within the range of Potamochoerus (59–85; n = 51) and K. afarensis (77–82; n = 2), while being narrower than in K. majus (93–114; n = 7) and males of K. limnetes (75–90; n = 3) ( Fig. 6B, C ). In female specimens of K. limnetes (recognized by their small lower canines and short mandibular symphysis), this region is comparatively narrow (ratio of 61–74; n = 3). In K. phillipi sp. nov., the posterior edge of the symphysis is fairly vertical, as in K. majus , but unlike the inclined condition seen in K. limnetes and Potamochoerus ( Fig. 6D ). The postcanine constriction is strong, although it should be noted that this character is related to sexual dimorphism (the differential development of canines in males and females), and hence highly variable within each species. The incisor arcade is relatively straight, as in Hylochoerus and K. majus ( Fig. 6C ). It is possible that this character may be highly variable and related to sexual dimorphism as in Potamochoerus , K. afarensis , and K. limnetes , with relatively straight and angled incisor arcades characterizing males and females, respectively.

As in Hylochoerus and K. majus , but unlike in Potamochoerus , the width across both mandibular bodies at the level of the third molars is relatively large compared to the width of the mandible across the mandibular condyles ( Table 4). The ascending ramus is relatively short, and similar to that of other species of Kolpochoerus . The mandibular body is relatively high compared to the overall height of the mandible, and marked by a prominent swelling at the level of the molars. The latter feature, typical of Kolpochoerus , is to a lesser degree also present in Potamochoerus ( Fig. 6A ). The main anterolateral mental foramen is located relatively more dorsally than in Potamochoerus and K. limnetes , and more ventrally than in Hylochoerus and K. majus . In lateral view, the coronoid process terminates below the level of the dorsal border of the mandibular condyle, unlike in Potamochoerus , Hylochoerus , and other species of Kolpochoerus .

Lower dentition. —The mandibular dental formula is 3.1.3.3, with no evidence for p1. As in Kolpochoerus limnetes and K. majus , the lower incisors are reduced compared to K. afarensis and Potamochoerus . The enamel of the cheek teeth is relatively thick, as in K. afarensis , K. majus , early K. limnetes , and Potamochoerus . The lower canine is verrucose (the distal face being smaller than the labial one), as in every species of Kolpochoerus . The canine is relatively wider than in K. afarensis , resulting in a relatively open, triangular cross section as seen in K. majus and K. limnetes ; however, the height of the canine (measured from the alveolar rim to the crown apex) is smaller than in the latter two species.

The total length of the cheek tooth row is similar to K. afarensis , somewhat smaller than in K. limnetes and K. majus , and larger than in average specimens of Potamochoerus ( Table 4). The diastema between the lower canine and the premolars is relatively short compared to the average K. lim-

A 48 B 150

4

p 46 140

of

level

faces m 2 42 44 120 130

lingual

- 1 m at 40) mm (110

between mandible

36 38 width 100 90

width of width

34 32 Symphysis 70 80

mandible

x greatest 30 28 60 50

100 / 26 70 80 90 100 110 120 130 140 150 160 170 40

70 80 90 100 110 120 130 140 150 Greatest width of mandible at m1-m2 level (mm) Symphysis length (mm)

C 120 D

length 110 Kolpochoerus MAT-VP- phillipi 1/ 5 sp. nov. Kolpochoerus A.L. 220 afarensis -2

symphysis 100 5 cm

/ 90

width

80

Kolpochoerus KL 255- majus 1 Kolpochoerus OMO 27/3-1967 limnetes -1044

symphysis 70

dorsal

x

100 60 anterior posterior

50

10 15 20 25 30 35 40 45 50 55 60

ventral

Angle of incisor arcade (°)

Kolpochoerus phillipi sp. nov. Kolpochoerus majus Kolpochoerus afarensis Kolpochoerus limnetes Potamochoerus porcus Hylochoerus meinertzhageni Potamochoerus larvatus netes and K. majus , and relatively longer than in K. afarensis and Potamochoerus . The premolars are similar in proportion and size to the smallest specimens of K. limnetes and K. majus . The ratio of premolar row to molar row length (M14/ M15*100 = 49) resembles that of Potamochoerus (average M14/M15*100 = 52; n = 62), early K. limnetes (for example, L 36-27 from Member D of Shungura Formation has a ratio of 46) and K. majus (average M14/M15*100 = 49; n = 7) ( Fig. 5D ). Both the m1 and m2 of the holotype mandible are heavily worn, and within the range of K. afarensis , K. limnetes , and K. majus in terms of their size and proportions ( Fig. 5C ; Table 5). The m2 of the paratype mandible is slightly smaller than that of the holotype, similar in size to the specimens of K. afarensis ( Fig. 5C ).

Judging from the isolated m3s referred to Kolpochoerus cf. phillipi sp. nov. ( Fig. 3C–G ), it seems that they were small- er, on average, than those of K. majus and early K. limnetes (Member C of the Shungura Formation). The holotype m3 is one of the largest specimens, which is congruent with its identification as a male ( Fig. 5A ; Table 5), and comprises three pairs of lateral pillars, followed by a small terminal pillar. The labial pillar of the third pair is more developed than the lingual one. In terms of its size and proportions, the m3 of K. phillipi sp. nov. is largely indistinguishable from that of K. afarensis , early K. limnetes (e.g., from members B and C of the Shungura Formation), and K. majus ( Fig. 5A ). However, the m3 talonid is more complex than in K. afarensis , which is characterized by two pairs of lateral pillars, followed by a single, well-developed terminal pillar. By contrast, the talonid of K. phillipi sp. nov. is less complex than that of contemporary specimens of K. limnetes from Member C of the Shungura Formation (ca. 2.7–2.5 Ma), which have a symmetric third pair of lateral pillars and a well-developed terminal pillar ( Fig. 3M, N ); however, older representatives of K. limnetes from Member B of the Shungura Formation (ca. 2.9 Ma) resemble K. phillipi sp. nov. in terms of m3 talonid complexity ( Fig. 3K, L ). In Middle Pleistocene specimens of K. majus , there are three pairs of lateral pillars and a well-developed terminal pillar ( Fig. 3P–S ). With the exception of the smaller size of the terminal pillar, the holotype m3 thus resembles that of K. majus , having well-separated and mesiodistally compressed lateral pillars and a simple, rounded wear pattern, resulting in a bunolophodont aspect ( Fig. 3A ). Both of the holotype m3s are too worn to determine whether there are one or two median pillars between the second and third pairs of lateral pillars. Several authors consider this character to be diagnostic of the genus Kolpochoerus ( van Hoepen and van Hoepen 1932; Geraads 2004), although it is absent in K. deheinzelini , K. millensis , K. cookei , and usually also K. afarensis . In K. cf. phillipi sp. nov., the median pillar is single, or faintly divided

Fig. 3B–G ), whereas there is a double median pillar in the earliest K. limnetes ( Fig. 3K, L ) and K. majus ( Fig. 3P–S ).

Stratigraphic and geographic range.—Known only from ca. 2.5 Ma old deposits in the Matabaietu and Wilti Dora areas, Middle Awash study area, Afar Depression, northern Ethiopia.

Figures

Fig. 1. Holotype cranium (MAT-VP-1/5) of the suid Kolpochoerus phillipi sp. nov. from Matabaietu area, ca. 2.5 Ma, Plio-Pleistocene, in dorsal (A), ventral (B), anterior (C), and lateral (D) views.

Fig. 2. Holotype mandible (MAT-VP-1/5) of the suid Kolpochoerus phillipi sp. nov. from Matabaietu area, ca. 2.5 Ma, Plio-Pleistocene, in dorsal (A), anterior (B), and lateral (C) views.

Fig. 3. Dental morphology of the suid mammal Kolpochoerus phillipi sp. nov. (A, B), Kolpochoerus cf. phillipi sp. nov. (C–I), Hylochoerus meinertzhageni (J), Kolpochoerus limnetes (K–O), and Kolpochoerus majus (P–S). Matabaietu area, ca. 2.5 Ma (A, B, E, F, I); Wilti Dora area, ca. 2.5 Ma (C, D, G, H); extant (J); unit B-10, Shungura Formation, ca. 2.95 Ma (K, L); unit C-8, Shungura Formation, ca. 2.58 Ma (M, N); lower part of Member J, Shungura Formation, ca. 1.7 Ma (O); Daka Member of Bouri Formation, ca. 1 Ma (P); Upper Bodo Sand Unit, ca. 0.5 Ma (Q, S). A. Holotype MAT-VP-1/5, left p2–m3 in occlusal view (A1), right P1–M3 in occlusal view (A2), right I2 (A3) and I1 (A4) in labial views. B. Paratype MAT-VP-5/1, left p4–m3 in occlusal view. C. KL 39-4, left m3 in occlusal (C1) and lingual (C2) views. D. KL 73-1, right m3 in occlusal (D1) and lingual (D2) views. E. KL 234-1, right m3 in occlusal (E1) and lingual (E2) views. F. KL 234-3-5, left m3 in occlusal (F1) and lingual (F2) views. G. KL 24-1 b, left m3 in occlusal view. H. KL 10-3, mesial fragment of left m3 in occlusal view. I. MAT-VP-5/2, right M3 in occlusal (I1) and labial (I2) views. J. MNHN-ZM-AC 1951-208, right m3 in occlusal view. K. OMO 28-1968-2100, right m3 in occlusal (K1) and lingual (K2) views. L. OMO 211-10005, right m3 in occlusal (L1) and lingual (L2) views. M. OMO 18-1968-2823, left m3 in occlusal (M1) and lingual (M2) views. N. OMO 18-1968-2104, right m3 in occusal view. O. OMO 354-10004, left m3 in occlusal view. P. BOU-VP-3/50, right m3 in occlusal (P1) and lingual (P2) views. Q. BOD-VP-1/9, right m3 in occlusal (Q1) and lingual (Q2) views. R. KL 185-2, right m3 in occlusal view. S. KL 251-2, right m3 in occlusal view.

Fig. 4. Scatterplots of cranial measurements comparing Kolpochoerus phillipi sp. nov. with other species of Kolpochoerus and extant African species. A. Premaxillary proportions vs. premaxillary orientation. B. Parietal constriction vs. frontal width. C. Palate convergence vs. palate proportions. D. Cranium relative height vs. relative cranium length.

Fig. 5. Scatterplots of dental measurements comparing Kolpochoerus phillipi sp. nov. with other species of Kolpochoerus and extant species of African suids. A. Proportions of m3. B. Proportions of M3. C. Proportions of m2. D. Proportions of lower premolar and molar series. Data for K. millensis from Haile-Selassie and Simpson 2013.

Fig. 6. Scatterplots of mandibular measurements comparing Kolpochoerus phillipi sp. nov. with other species of Kolpochoerus and extant African species. A. Degree of mandibular swelling. B. Proportions of mandibular symphysis. C. Proportions of symphysis vs. angle of incisor arcade. D. Sagittal profiles of mandibular symphysis in various suids.