Proboscidipparion heintzi Eisenmann & Sondaar, 1998

Bernor, Raymond L. & Sen, Sevket, 2017, The Early Pliocene Plesiohipparion and Proboscidipparion (Equidae, Hipparionini) from Çalta, Turkey (Ruscinian Age, c. 4.0 Ma), Geodiversitas 39 (2), pp. 285-314 : 302-304

Proboscidipparion heintzi Eisenmann & Sondaar, 1998

HOLOTYPE. — Right MCIII of the central digit (MNHN.F.ACA49A), associated with the entire MCII (ACA149C) and the entire proximal portion of the MCIV (ACA49B). Collections are maintained at the Laboratoire de Paléontologie , MNHN, Paris.

PARATYPE. — 1PHIII (MNHN.F.ACA125; Eisenmann & Sondaar 1998: fig. 16C).

TYPE LOCALITY. — Çalta, Turkey.

AGE. — Early Ruscinian, MN15, c. 4.0 Ma.

DISTRIBUTION. — Turkey.

DIAGNOSIS (modified from Eisenmann & Sondaar 1998 with augmentation). — Skull as known from a juvenile individual large, lacking preorbital fossa with nasals retracted posterior to infraorbital foramen and directly above parastyle of dP3 (as conserved on the right side of MNHN.F.ACA336) with a broad narial opening. Deciduous cheek teeth with large dP1 retained into subadulthood; dP2 with very elongate anterostyle; fossette plications well developed; protocones short, oval to rounded; mandibular i1 very large being mesio-distally expanded. Metapodials very robustly built being relatively short and broad. 1PHIIIs robust, being long relative to metapodials, radii and tibiae. 3PHIIIs are extremely wide, and flat. MCVs are fused with MCIV’s.

DESCRIPTION

The hypodigm for Çalta Proboscidipparion heintzi is listed in Table 1. The juvenile skull MNHN.F.ACA336 ( Fig. 11A ) is well preserved and virtually complete except for the premaxilla and the right side of the cranium. The narial opening, as seen in oblique view ( Fig. 11B ), is very wide. The dP1 is large and wide and retracted posterior to the infraorbital foramen and level of dP3 parastyle, suggesting that the premaxilla supported a mobile snout not unlike that of a tapir. The dP1 is rotated so as to have the mesial extent directed mesiolabially and distal extent oriented distolingually. The dP2 has anterostyle extended mesially; mesial and distal borders of the prefossette are strongly plicated, with the postfossette having a complex mesial border but simpler posterior border; the anterolingual enamel band is likewise complex, while the distolingual enamel band is simple; pli caballin is double with plis broadly separated; hypoglyph is very shallow; protocone is oval shaped and lacking a pli. The dP3 has the mesial border of prefossette worn with obliterated plis, while the posterior border is complex; mesial and distal borders of the postfossettes are likewise worn and not preserving the original plication frequency; pli caballin is complex with multiple folds; hypoglyph is moderately deeply incised; protocone is short and round. The dP4 is in relatively early wear and preserves moderately complex plications of the prefossette and lesser plication of the postfossette likely due to the early stage-ofwear; pli caballin would appear to be complex; hypoglyph is deeply incised; protocone is short, rounded with a flattened lingual border. The M1 is just emerging from its crypt.

Eisenmann & Sondaar (1998; MNHN.F.ACA337A) figured a juvenile right maxilla with dP1-4, M1 and M2 emerging from the crypt and M3 within its crypt ( Fig. 12A ) and an associated mandible with dp2-4 and m1-m2 ( Fig. 12B ). The maxillary deciduous cheek teeth are more worn than in ACA336 with resulting morphological differences. The dP1 is still retained but worn, with a similar orientation as ACA336. The dP2 still has an elongate anterostyle. All deciduous teeth have simpler plications of the fossettes; protocones are short and round; hypoglyphs are moderately deeply incised; M1 and M2 are too unworn to preserve occlusal details. The juvenile mandible (ACA337B) has rounded to elongate metaconids and metastylids (“caballine pattern” ofEisenmann & Sondaar 1998); pre- and postflexids have simple enamel margins; linguaflexid is shallow on dp2, V-shape on dp3-4 and m1; ectoflexid is progressively deeper on dp2 to m1, separating metaconid and metastylid on dp4 and m1.ACA337B includes a mandibular symphysis ( Fig. 12C ) that preserves a left i1 crown, in its crypt. This crown is extremely large in its mesiodistal dimension, and is only found in advanced members of the “ Sivalhippus Complex”, namely African Pleistocene Eurygnathohippus cornelianus .

Proboscidipparion heintzi is derived in its very robust, relatively short and wide MCIIIs ( Figs 4A, B; 8B ), as exemplified by the type specimen MNHN.F.ACA49A ( Fig. 13A, B ) exhibiting similarity in these dimensions to eastern African Lothagam, Late Miocene Sivalhippus turkanensis following Wolf et al. (2013). Çalta MCIII Proboscidipparion heintzi is extraordinary however in its combination of short and at the same time broad proximal, distal and midshaft dimensions. The Proboscidipparion heintzi MCIV ( Fig. 13C ) is not analysed and otherwise not very informative. Perpignan MCIII (w; Fig. 4) is extraordinary in its own right having extremely short and wide dimensions; shorter than Çalta Proboscidipparion heintzi .

Çalta Proboscidipparion heintzi 1PHIII is short and robustly built ( Figs 6B; 10C ; 14A, B ) comparing most closely with Eurygnathohippus woldegabrieli , Eu. afarense and Proboscidipparion heintzi . Eisenmann & Sondaar (1998: fig.16) illustrated the contrasting 3PHIII morphologies of Plesiohipparion cf. longipes (MNHN.F.ACA87; Eisenmann & Sondaar [1998: fig. 16A] and Proboscidipparion heintzi (ACA89 and ACA125; Eisenmann & Sondaar [1998: fig. 16B, C]). Both our series of bivariate plots and log10 ratio diagrams for MCIII, MTIII and 1PHIII clearly show the strongly contrasting morphological proportions of Çalta Plesiohipparion aff. longipes and Proboscidipparion heintzi .

REMARKS

Sefve (1927) nominated the nomen Proboscidipparion sinense based on a complete skull and mandible from the Early Pleistocene of Langou, Mianchi County, Henan Province, China ( Zdansky 1923; PMU M3925, Bernor et al. 1990: figs 17 and 18). Sefve (1927) recognized Proboscidipparion sinense unique in its very large size, and extraordinarily derived nasal and muzzle structure with characters that are absent in other known species of “ Hipparion ”. Proboscidipparion sinense has deeply retracted nasals, a very elongate and narrow premaxilla and very strong plications of the upper cheek teeth (re: Bernor et al. 1990; Bernor & Sun 2015). Teilhard de Chardin & Piveteau (1930) described specimens of Proboscidipparion from Nihewan, Hebei but did not believe that a generic distinction was warranted (hence their H. Proboscidipparion sinense ). Proboscidipparion sinense also cited as coming from Bajiazui in Qingyang, Gansu ( Wang et al. 1966; Wang & Xue 1982), Banqiao in Heshui, Gansu ( Zheng et al. 1975), Kehe in Ruicheng, Shanxi ( Chia et al. 1962), Yangguo in Weinan, Shaanxi ( Chi 1975), and Tuozidong in Nanjing-Jiangsu ( Dong & Fang 2005). The age of Proboscidipparion sinense is Early Pleistocene (c. 2.6 Ma; Deng 2012).

Hipparion (Proboscidipparion) pater Matsumoto, 1927 was identified from the Gaozhuan Formation, Baihaicun based on a male skull (THP 14312) and nominated as a Lectotype by Qiu et al. (1987; pls. I and II). Another complete skull (THP20763) was reported from the Gaozhuang Formation Nihe, Yushe by Qiu et al. (1987: pl. II). Qiu et al. (1987: pl. IV; Fig. 15 A-C) further reported a juvenile skull and mandible from the Gaozhuang Formation, Yushe,THP20847 which compares closely with the Çalta MNHN.F.ACA 336 juvenile skull in maxillary, nasal and deciduous cheek tooth occlusal morphology.

Bernor et al. (1990), Bernor & Sun (2015) and Bernor et al. (2015a) have recognized Proboscidipparion as a distinct lineage of hipparion warranting generic rank. We include Proboscidipparion heintzi in this lineage because of its retracted nasals with broad narial opening, elongate dP2 anterostyle and exhibition of complex plication of the cheek teeth (as per Bernor & Sun 2015). The skull of Proboscidipparion heintzi compares most closely with Early Pliocene Proboscidipparion pater Qiu, Huang & Guo, 1987 in its nasal retraction and maxillary cheek tooth morphology ( Qiu et al. 1987). Postcrania for Chinese Proboscidipparion species are not certainly known and may be confused with the elongate slender morphology of Plesiohipparion spp. It would appear that Proboscidipparion first evolved in the very Latest Miocene or earliest Pliocene of China and extended its range to Turkey in the Early Pliocene. Eisenmann & Sondaar (1998) estimated that Proboscidipparion heintzi was a large hipparion that weighed 300-360 kg when alive.

Figures

FIG. 11. — MNHN.F.ACA336, juvenile skull: A, lateral view; B, oblique view of nasal opening; C, dP1-M1 occlusal view. Scale bars: A, B, 10 cm; C, 5 cm.

FIG. 12. — MNHN.F.ACA337, juvenile maxilla and mandible: A, right dP1-M2 (in crypt), occlusal view; B, left dp2-m2 (in crypt); C, close up of very large i1 (in crypt). Scale bar: 5 cm.

FIG. 8. — Log10 ratio diagram of MCIII: A, primitive Old World Hipparion; B, robust limbed Old World Hipparion and Çalta Proboscidipparion heintzi (Eisenmann & Sondaar, 1998); C, slender limbed Old World Hipparion and Çalta Plesiohipparion cf. longipes (Gromova, 1952).

FIG. 13. — MNHN.F.ACA49A, type Proboscidipparion heintzi (Eisenmann & Sondaar, 1998), MCIII: A, cranial view; B, caudal view; C, MNHN.F.ACA49B, ACA140, type Proboscidipparion heintzi MCIV, lateral view. Scale bar: 5 cm.

FIG. 10. — Log10 ratio diagram of 1PHIII:A, slender limbed Cremohipparion Qiu, Huang & Guo, 1987 and Hipparion campbelli Bernor,1985, 1PHIII Log10 Ratios, Ho Std; B, slender limbed Eurygnathohippus 1PHIII; C, robust limbed Hipparions.

FIG. 14. — MNHN.F.ACA78, Proboscidipparion heintzi (Eisenmann & Sondaar, 1998), 1PHIII: A, cranial view; B, caudal view. Scale bar: 5 cm.

FIG. 15. — THP 20847, Yushe Basin, China Proboscidipparion pater Qiu, Huang & Guo, 1987 juvenile skull and mandible: A, skull in right lateral view; B, occlusal view of palate; C, left mandible labial view; D, left mandible occlusal view. Scale bar: 5 cm.