Ceratotherium neumayri ( Osborn, 1900 )

Antoine, Pierre-Olivier & Saraç, Gerçek, 2005, Rhinocerotidae (Mammalia, Perissodactyla) from the late Miocene of Akkașdağı, Turkey, Geodiversitas 27 (4), pp. 601-632 : 603-615

Ceratotherium neumayri ( Osborn, 1900)

Atelodus neumayri Osborn, 1900: 263 , text-fig. 16.

Diceros pachygnathus Guérin, 1980: 202-400 , textfigs 30, 31, 33, 39-43, 46, 51-56, tabl. 45-49, 51-56, 59-63, 65, 67-72, 75-78.

Ceratotherium neumayri – Geraads 1988: 13-41, textfigs 1-5, pl. 2; 1994: 82-85, text-figs 1, 2, pl. 2, fig. 5. — Geraads F Koufos 1990: 151-154, pl. 1. — Kaya 1994: 13-22, pls 1, 2. — Heissig 1996: 341-342, 347, text-fig. 27.1.

For synonymy anterior to 1980, see Geraads (1988: 36).

MATERIAL. — Complete skull with P2-M3, AK4-212; right M1, much worn, AK2-294; fragment of left M1/2, AK4-243; left p4, AK2-295; left maxilla with D1-3 and D4 erupting, AK5-502; right maxilla with D3 and alveolus of D4, AK6-61; fragment of a left juvenile mandible, with d3 and the alveolus of d2, AK2-296; right D1, AK5-424; fragment of left D2, AK2-435; anterior fragment of left d3, AK5-425 and right d3, AK6-134 (same individual); left ulna lacking distal end, AK6-132; right humerus, right radius and right ulna from the same individual, AK4-w.n.; proximal part of a right humerus, AK6-301; distal part of a right humerus, AK-w.n.; fragment of diaphysis of a left humerus (juvenile), AK4-183; distal epiphyses of a left (GOK-17) and a right radius (GOK-16) from the same young individual; left radius in two parts, GOK- 18 and GOK-19; left radius, AK5-627; proximal end of a left radius, AK4-213; left radius lacking distal end, AK4-241; proximal end of a left radius, AK5-67; left ulna, AK6-133; left ulna lacking distal end (juvenile), AK6-131; left ulna lacking distal end, AK7-156; right ulna, AK3-118; right ulna, AK4-184; right ulna (predated olecranon), AK6-302; proximal part of a right ulna, AK2-95; proximal part of a right ulna, AK6-303; left scaphoid, AK2-437; right scaphoid, AK5-630; right pyramidal (fragment), AK5-631; left magnum without posterior tuberosity (GOK-11), left unciform (GOK-10), left metacarpus (McII, GOK-2; McIII, GOK-4; McIV, GOK-3) and right metacarpus (McII, GOK-6; McIII, GOK-1; McIV, GOK-5) from the same individual; left magnum, AK5-632; right magnum, AK7-38; left unciform, AK5-633; left unciform lacking posterior tuberosity, AK6-58; left unciform lacking posterior tuberosity, AKK-157; right unciform, AK4-74; right unciform, AK7-147; posterior tuberosity of a right unciform, AKK-156; posterior tuberosity of a right unciform, AKK-282; left McII, AK6-55; proximal part of a left McII, AK7-37; proximal part of a left McII (juvenile), AK5-182; left McIII, AK5-68; proximal part of a left McIII, AK3-202; proximal part of a left McIII, AK14-23; distal part of a left McIII, AKB-83; left McIV, AK3-230; right McIV, AK5-436; proximal fragment of a right McIV, AK13-2; left femur, AK4-253; left femur (diaphysis), AK5-367; left femur (diaphysis), AK6-153; distal part of a left femur, AK7-39; femoral head, AK5-323; distal end of a right femur, AK3-63; left patella, AK11-82; fused left tibia and fibula, AK7-40; distal end of a right tibia, AK5-366; distal end of a right tibia, AK7-63; distal end of a right tibia, AKK-154; distal epiphysis of a left fibula, AK13-3; left astragalus (young), AK2-438; left astragalus, AK4-75; left astragalus, AK5-523; left astragalus, AK5-423; lateral part of a left astragalus (young), AK5-319; left astragalus (young), AK6-56; left astragalus, AK7-148; left astragalus, AK11-1; right astragalus, AK5-69; right astragalus, AK5-634; medial fragment of a right astragalus, AK13-4; left calcaneus, AK3-66; right calcaneus, AK7-36; left navicular, AK4-76, and broken left ectocuneiform, AK4-77, from the same individual; right navicular, AK5-439; right cuboid, AK5-636; left entocuneiform, AK13-5; right mesocuneiform, AK5-637; left ectocuneiform, GOK-13; right ectocuneiform, AK5-635; left metatarsus (MtII, GOK-9; MtIII, GOK-7; MtIV, GOK-8); proximal end of a right MtII, AK5-440; left MtIII, AK2-163; right MtIII lacking distal epiphysis (young), AKA-44; distal end of a right MtIII, AK4-238; proximal end of a right MtIV, AK5-437; distal fragment of a metapodial, AK4-214.

Additional material: cervical vertebra, AK3-61; cervical vertebra, AK3-67; cervical vertebra, AK4-182; cervical vertebra, without caudal epiphysis, AK5-435; thoracic vertebra, AK7-186; thoracic vertebra, AK6-300; thoracic vertebra, AK3-133; thoracic vertebra, AK5-324; thoracic vertebra, AK14-22. These specimens are tentatively referred to C. neumayri , based on their large size and the domination of that very species with respect to other associated rhinos in Akkasdagw ı. However, their assignment to S. pikermiensis cannot be ruled out.

DESCRIPTION

Skull ( Fig . 1; Appendix: Table 1)

The adult skull AK4-212, complete and not deformed, is large and dolichocephalic (width/length ratio = 0.46). The premaxillae are rather long (length = 75 mm) and edentulous. The nasal bones do not bear any lateral apophysis. The foramen infraorbitalis is open above the P3/P4 limit. The nasal notch reaches the middle of P3 while the anterior border of the orbit is above the middle of M2. There is no nasal septum ossification. The only preserved suture is the jugal/squamosal one, which is straight and smooth. The processus lacrymalis is absent, but a strong lateral projection of the orbit widens the skull (zygomatic width/frontal width ratio = 1.47). The processus postorbitalis is absent on the frontal. The base of the processus zygomaticus maxillari is high: it begins several centimetres above the neck of M2/3. The zygomatic arch is low and poorly developed. It forms a thin stripe, without any processus postorbitalis. The dorsal profile of the skull is mainly flat, only rising in its posterior third. The foramen sphenorbitale and the foramen rotundum are fused. The temporal crest is short, so that the area between the latter and the nuchal crest is flat. The external auditory pseudomeatus is partially closed. The occipital side is inclined backward: the occipital condyle is anterior to the occipital crest. The nuchal tubercle is poorly developed. Yet, there is a deep axial fossa reaching the occipital crest. The toothrow is restricted to the anterior half of the skull. The thin and straight hamulus pterygoideus is very close to the M3. The posterior margin of the pterygoid is nearly horizontal. The rostral end of the nasal bones is very broad and round- ed. The nasal dome and the rough vascular prints testify the presence of a well developed median nasal horn. The nasal bones are totally fused, but there is a shallow median groove from the tip of the nasals until the top of the horn dome. They are long (about the third of the total skull length). A wide and low dome on the frontals further indicates the presence of a smaller frontal horn. The fronto-parietal crests are smooth and widely separate (minimum distance = 50 mm). The occipital crest is strongly concave, nearly forked. The temporal fossa is hugely developed, forming a platform at each side of the braincase.

In distal view, the anterior start of the processus zygomaticus maxillari is progressive, following the curvature of the teeth row. The palate is narrow (Appendix: Table 1). The palatine fossa reaches the posterior part of the M2. The vomer is thick and rounded. The articular tubercle for the mandible, transversally concave, forms a high and salient semi-cylindre in lateral view. The foramen postglenoideum is not visible. The processus postglenoidalis is long, strong and narrow transversally. The articular surface of the latter defines a right dihedron in cross section. The foramen nervi hypoglossi is open in the middle of the condylar fossa. A sagittal crest runs all along the basilar process of the basioccipital. The posterior part of the processus zygomaticus of the squamosal is concave, due to a transverse groove. The processus posttympanicus is curved forward and very short, while the processus paraoccipitalis is long and well developed. Their bases are fused. The foramen magnum is circular. A median transverse ridge runs all over the occipital condyle, but there is no axial truncation on the condyle (at least at adult stage).

Two juvenile maxillae (with D4 erupting) are also preserved (AK5-502; AK6-61). They show a few morphological features: the foramen infraorbitalis is located above the posterior third of D2 and the nasal notch reaches the middle of D2 on both specimens. The processus zygomaticus maxillari begins at the level of D4. The alveolus for M1 is preserved on AK5-502. The palate is narrow.

The only mandible referable to C. neumayri is a fragmentary mandible with an unworn d3 (i.e. new born individual; Hillman-Smith et al. 1986). The inferior border is convex. The foramen mentale is located under the d2/d3 limit. The sulcus mylohyoideus is very deep.

Dentition

Except for the complete series of the skull AK4- 212 ( Fig. 2A ) and the milk series of the juvenile maxillae (AK5-502; AK6-61; Fig. 2 B-D), dental remains are very rare in Akkasdagw ı, with respect to postcranial specimens.

The upper dental formula is 3P-3M (there is neither alveolus nor any trace of D1/P1 on P2). The premolar series is long when compared to the molar series (L P3-4 /L M1-3 ratio = 0.62). There are no enamel foldings on the crowns. A thin layer of cement is present on the ectolophs. Elsewhere, the cement is scarcely preserved. The enamel is thin, wrinkled at the neck and corrugat- ed on the top of the crowns (permanent and milk teeth). The crowns are high but neither hypsodont nor subhypsodont (sensu Antoine 2002). No isolated permanent tooth has been unearthed, thus the morphology of the roots is unknown. The dental structures are very simple.

There is neither antecrochet nor anterior constriction on the protoloph on upper molars and premolars. The protoloph is curved backwards on the whole upper series. The crochet and the crista are always present. Both are simple, acute and sharp. The former is sagittal, while the crista is transverse. There is no medifossette, despite the constant strong development of the crochet and the crista. They nearly join, especially on P4. The paracone fold is present but weak. The parastyle is sagittal. The metacone fold is absent from the whole series, except on P4, where it is restricted to the basal half of the teeth.

Upper premolars. The premolars are molariform, with separate lingual cusps. There is no labial cingulum, but a reduced lingual cingulum is always present. The metaloph is not constrict- ed. The postfossette is deep and narrow. On P2, the protocone is less developed than the hypocone. The protoloph is thin but continuous and connected with the ectoloph. The hypocone is posterior to the metacone on P2-4. There is no pseudometaloph on P3.

Upper molars. The molars are lacking labial and lingual cingula, except on M3, where a wide and low tubercle is laying at the entrance of the median valley. The metastyle is long. The metaloph is short and the posterior part of the ectoloph is concave on M1-2. There is no cristella. The posterior cingulum is low and reduced. There is no antero-lingual groove on the hypocone of M1-2: the metaloph is continuous. The central valley is open lingually (no junction between antecrochet and hypocone). There is no lingual groove on the protocone of M2. The mesostyle is thick on M1 and M2. M3 has a triangular outline, with fused ectoloph and metaloph. The protoloph is transverse, even if curved backwards. There is no posterior groove on the ectometaloph.

Lower series. The only permanent lower tooth unearthed in Akkasdagw ı and referred to C. neumayri is a left p4. The ectolophid groove is developed until the neck. The paraconid and the protoconid are angulous. Thus, the trigonid is angulous and it forms a right angle. There is no constriction on the metaconid and the entoconid. The posterior valley is V-shaped in lingual view. There is neither lingual nor labial cingulum.

Upper milk teeth. Two juvenile maxillae are preserved. The first one bears D1-3 and erupting D4 (AK5-502) whilst AK6-61 bears D3. Isolated D1 (AK5-424) and D2 (AK2-435) have also been unearthed. The teeth have large dimensions (Appendix: Table 2). The crowns are high, but not so.

The upper milk molars bear a mesostyle and a long sagittal parastyle. The mesostyle is sharper and stronger in D2. The paracone fold is thick and salient while the metacone fold is lacking. The protoloph is curved backwards, without anterior constriction or antecrochet. The crista is long and transverse, reaching the lingual half of the tooth (AK5-502). The crochet is strong and straight, sagittal (D1-4), getting longer from D1 to D4. The metaloph is lacking any anterolingual groove. There is no labial cingulum. The lingual cingulum is variably developed: present and continuous on both D2, it is weak on the D3 AK5-502 (one spur at the entrance of the median valley). There is no trace of lingual cingulum on the D3 AK6-61. The postfossette is narrow and deeper than the median valley. The posterior cingulum is low while the anterior one is thick and high.

D1 is triangular, with a lingual wall. Its postfossette is open backwards. D2 has no lingual wall nor mesoloph, but secondary folds and small structures (medifossette-like). D3-4 may present a small vertical ridge posteriorly to the crochet, on the posterior side of the metaloph (AK5-502). Lower milk teeth. Three germs of d3 are preserved, among which two belong to the same individual (AK5-425 and AK6-134). The enamel is corrugated. The metaconid and entoconid are constricted. The protoconid fold is lacking or weak (AK2-296). There are no vertical roughnesses, nor anterior groove nor median fold on the ectolophid. The external groove is developed but smooth. The paralophid is double. It determines a small and wide closed pit in front of the tooth. Only the reduced cingula exist on the anterior and posterior faces. The posterior valley is widely open, as is the trigonid valley. There is no lingual groove on the entoconid. The crown is moderately high.

Postcranial skeleton

The bones from Akkasdagw ı are large and robust, with thick long bones and broad and low manus and pes. The dimensions and proportions correspond essentially to those of the large/largest individuals of Ceratotherium simum as listed by Guérin (1980, 2000); they even sometimes reach the average of Rhinoceros unicornis ( Guérin 1980) . On the other hand, they are 5 to 30% smaller than corresponding remains referred to the Miocene African rhinocerotine Diceros australis Guérin, 2000 .

Atlas. AK5-w.n. is badly preserved, lacking the processi transversi. The bone is thick and the articular width fits the skull AK4-212, which leads us to assign it tentatively to the same individual. The foramen vertebrale has a wide piriform outline. The foramen transversarium is large, only connected with the foramen vertebrale. The condylar facets are kidney-shaped, while the axisfacets are slightly concave transversally.

Cerviwal and thorawiw vertebrae. They bear no significant character.

Humerus (Appendix: Table 3; Fig. 3A ). This bone is robust. The length is approximately 440 mm, owing to the proximal end AK6-30 and the distal end AK4-w.n. The proximal end is thick and deep (APD), with a high and strong tuberculum majus. The caput humeri is wide, weakly rounded. The tuberculum minus is low. Both are separate by a shallow depression. The deltoid tuberosity is wide and high, thickly developed, with a strong and extended insertion for the m. deltoideus. The diaphysis is narrowing below the deltoid tuberosity. The lateral epicondyle is again wide, but rather low, forming a right angle at its proximal end in anterior view. The trochlea is huge, especially the medial lip. The latter is much more developed (APD) than the lateral one. The median narrowing is strong. The fossa olecrani is wide and low. There is no synovial fossette on the antero-proximal part of the trochlea. A shallow distal gutter separates the lateral epicondyle from the trochlea. The lateral epicondyle is the lowest tip of the humerus.

Radius ( Fig. 3B ). The bone is strong, with thick ends. The proximal cochlea is higher in its posterior border. The proximal end is wide and deep (APD), much deeper medially. The anterior bor- der is straight in proximal view. The posterior facets, for the ulna, are separate. The medial one is low (10 mm) while the lateral one is very high and hugely developed (triangular). The insertion for the m. biceps brachii is wide and marked by roughnesses, but there is no deep depression. The diaphysis is straight medially and strongly concave laterally. The contact between the radius and the ulna extends all along the diaphysis, except for a short spatium interosseum, located at the proximal third of the bone. These observations indicate a twisted diaphysis for the ulna. In lateral view, the diaphysis is curved, with a convex ante- r i o r b o r d e r. T h e d i s t a l w i d e n i n g i s s t r o n g (Appendix: Table 4). No radius-ulna fusion has been observed in Akkasdagw ı. The gutter for the m. extensor carpi is deep and wide, deepened by the latero-distal tubercle (tuberculum dorsale) laying close to it. The lateral ulna-facet is unique, crescentiform and low. It is vertical and sagittally orientated. The distal articulation is only for the scaphoid and semilunate. The distal end is getting lower medially than laterally. The scaphoidfacet is visible in anterior view on a considerable height. This facet has a sigmoid sagittal cross section. Its posterior expansion forms a high rounded triangle. The semilunate-facet is wide, concave antero-posteriorly and flat transversally. There is no pyramidal-facet.

Ulna ( Fig. 3C, D ). There is an unexpected number of preserved ulnae (10 more or less complete specimens). They are as long as the femora, with a variable length (Appendix: Tables 5; 12). The olecranon is thick, and developed with variable shapes. It is always long, forming a closed angle with the diaphysis. The posterior tip of the olecranon (insertion of the m. triceps brachii) is salient with respect to the distal border of the process. The humeral cochlea is wide, as high medially as laterally. The median constriction is particularly marked. Distally to this articular surface, there is a broad oval area which is not articulated with the humerus. It forms a shallow depression on the whole sample. The radiusfacets are separate: the medial facet is vertical and transversally elongated, determining a low stripe, while the lateral facet is higher than wide. The medial facet is transversally convex, with a transverse lateral end and a sagittal medial end. The fossa between both facets is deep. The roughness corresponding to the contact with the radius runs all along the diaphysis, except for a short spatium interosseum, at the proximal third of the diaphysis. The diaphysis is curved and twisted. Its cross section is triangular, with sharp ridges. The distal end widens strongly. The distal radius-facet is low and crescentiform. The distal articulation, for the carpus, shows three facets. The smallest and medial one is for the semilunate (almondshaped); the rest of the surface corresponds to the pyramidal-facet (quarter circle) and the pisiformfacet. The latter is large but restricted to the postero-lateral side of the articulation. It is triangular and nearly vertical. Both are separated by a smooth ridge. There is no distal tubercle (tuberculum dorsale) on the antero-lateral side of the ulna. All these features are also shared by the juvenile ulnae (e.g., AK6-131).

Swaphoid. Two specimens are complete. They are cubic (Appendix: Table 6). The anterior and posterior heights are equal. The proximal facet is deep (ADP) and concave in medial view. There are only two facets for the semilunate. The proximal one is flat and wide. There is a large and rounded tubercle in the vicinity of the latter. On the distal side, the magnum-facet forms an equilateral triangle. Its surface is concave anteroposteriorly and slightly convex transversally. The trapezoid-facet is wide (TD) and saddle-shaped. The trapezium-facet is triangular, narrow (APD) and very high (Appendix: Table 6).

No semilunate, trapezium, trapezoid nor pisiform have been discovered in Akkasdagw ı.

Pyramidal. The specimen AK5-631 is badly preserved and broken. It is low and wide. The proportions and structures correspond to those of Ceratotherium neumayri from other Turolian localities of Turkey ( Saraç 1994). The proximal facet, for ulna, is small. So is the pisiform-facet. There is a strong tubercle on the lateral side. The medial facets for the semilunate are not preserved. On the distal side, the unciform-facet is flat transversally and concave antero-posteriorly.

Magnum ( Fig. 3E ). The posterior tuberosity is lacking in the three specimens (GOK-11, AK5- 632, AK7-38). The anterior side is broad and low (Appendix: Table 7), with a salient central tubercle (m. interossei dorsales). Its lateral border is oblique and straight. In proximal view, the scaphoid-facet is wide and transversally concave. The semilunate-facet has a question mark outline in lateral view. The proximal process is high, with a small diameter, and rounded. This facet reaches the anterior side of the bone. It is difficult to distinguish it from the unciform-facet, which is drop-shaped. On the medial side, there is a shallow anterior indentation between the scaphoid- and the McII-facets. The latter forms a flat sagittal stripe, horizontal and nearly rectangular. Distally, the McIII-facet is wide and saddleshaped, tapering backwards.

UnwiForm. The unciform is well represented (eight specimens). It is a large bone, with a broad anterior side and a long posterior tuberosity (low and wide). The anterior side is smooth, nearly flat, except on the medial corner where a sharp horizontal tubercle is salient (insertion of the m. interosseus dorsalis). The proximal facets are separate by an acute ridge. The semilunate-facet determines a quarter-circle. It may be transversally flat (AK7-147, AK4-74) or concave (GOK-10, AK6-58, AKK-157). The pyramidal-facet is larger, flat transversally and regularly convex sagittally. There is a wide and short postero-lateral expansion to this facet, which generally connects it to the McV-facet (except on AK7-147). The distal facets (magnum, McIII, McIV) are not distinct, except the most lateral one, for the McV. In anterior view, the latero-distal border of the bone is straight (McV-facet) while the rest of the distal border is rounded. This McV-facet forms an angle about 60° with the horizontal line. This orientation points out a tridactyl manus. AK5- 633 and GOK-10 are about 25% larger than other specimens (Appendix: Table 8).

MwII ( Fig. 4A, B ). The McII is wide on all its length (Appendix: Table 9). The proximal facet, for the trapezoid, is pentagonal and saddleshaped, transversally concave and sagittally convex. There is no trapezium-facet. The proximo-lateral facet (magnum) forms a sagittal stripe which widens backwards, at 45° from the horizontal line. There is only one McIII-facet, the anterior one, which is triangular, vertical and sagittally elongated. This facet is slightly concave. A large tubercle widens the proximal end on the medial side. The diaphysis is wide and deep, slightly flattened sagittally. It is nearly straight, only a little bit curved inwards. The insertion for the m. interossei is short. There is no distal widening. The distal trochlea is roughly square in distal view. Its anterior border is straight, as the lateral border (at right angle). The intermediate relief is low but sharp and restricted to the posterior side. The medial lip is wider than the lateral one. The latter is transversally flat, while the former is deeply concave. The medial part is deeper (APD) than the lateral lip.

MwIII ( Fig. 4A, B ). The McIII is a wide bone, slightly widened distally. The proximal end is wide, due to the strong lateral development of the unciform-facet. The magnum-facet is visible in anterior view. It is regularly concave transversally and separate from the unciform-facet by a sharp ridge (80° angle). The latter is wide (TD), slightly convex sagittally and triangular. The McII-facet has large dimensions. It is semi-circular and nearly vertical. The surface for the m. interossei is restricted to the proximal quarter of the diaphysis on the medial side, and it extends down to the distal third on the lateral side. The McIV-facets are large, well developed and fused on AK5-68 (close in AK3-202). The anterior one is dropshaped and the posterior one is circular and vertical. It is distally displaced with respect to the proximal end of the bone. The diaphysis is straight and flattened. On the anterior side, the insertion for the m. extensor carpalis is broad but without relief. There is no distal tubercle on the posterior side of the diaphysis. The distal trochlea has an antero-proximal border regularly rounded. In distal view, this surface is wider than deep (Appendix: Table 10). It is deeper medially. The anterior border is slightly convex while the medial and lateral ones are straight. The intermediate relief is sharp and high, visible in anterior view. It separates the trochlea into two equal halves.

MwIV ( Fig. 4A, B ). The McIV is shorter than the McII and McIII (Appendix: Table 11). The bone is wide, without median narrowing. The proximal side, exclusively devoted to the unciform, forms a rectangle triangle. On the medial side, the McIIIfacets are separate by a few millimetres. The anterior one is drop-shaped, while the posterior one is circular (45° angle between them). The diaphysis is curved laterally, at the half of the bone. The m. interosseus area reaches the half of the diaphysis. It is very salient, determining a large pad. The diaphysis is a little flattened. The distal trochlea is nearly square in distal view. The intermediate relief is low but sharp and restricted to the posterior side of the trochlea. This relief is displaced medially, so that the lateral lip is wider than the medial one. The latter is transversally flat whilst the former is concave.

Femur. AK4-253 is the only femur almost complete. The only part lacking is the trochanter major. Other specimens are distal ends, except for AK5-323, which is a caput femoris from a juvenile individual. The femur is rather slender. The head is wide and hemispheric. The surface of epiphysis is marked by a sharp transversal ridge (nor flat, nor crescentiform). The third trochanter is developed but not so much. It is high (Appendix: Table 12) and only forming a wide stripe. The trochanter minor determines a thin and narrow ridge, almond-shaped in anterior view. The proximal border of the wide patellar condyle is curved, in anterior view. The distal end is thickly developed, with well separate condyles for the tibia.

Patella. The only specimen is as high as wide (Appendix: Table 13). It is thick, with rounded structures. The APD is high. On the articular side, the medial lip is large and broad. The lateral one is narrower and transversally concave, as is the former. The proximal process (for the tendon m. quadriceps) is strongly developed but not very

Antoine P.-O. F Saraç G.

salient. The latero-proximal border of the articular surface is straight.

Tibia. The tibia is robust, with broad ends (Appendix: Table 14). AK7-40 corresponds to fused tibia and fibula. The contact probably occurs at early growth stages, because all the specimens bear traces of the contact between both bones. The fusion may occur later, at adult stage ( Fig. 3F ). The proximal condyles are well separat- ed by a deep intercondylar fossa. The medial condyle is sagittally flat and transversally concave – horizontal in its medial part and nearly vertical in its lateral tip. The lateral condyle for the femur is convex antero-posteriorly and slightly concave transversally. The latter is smaller (TD, APD), but equally high. It is oblique (45° with respect to the horizontal line). The tuberositas tibiae is very developed, with a broad and rough surface. In posterior view, the fibula is totally fused proximally with the tibia. Its proximal end is high but it does not bear any articular facet for the femur. The diaphysis is narrowing in its median part, with a triangular cross section. The spatium interosseum is the only area where the tibia and the fibula are not fused. It is restricted to the second proximal quarter of the bone. The tibia thickens strongly in its distal part (TD, APD). The antero-distal groove is wide and rather deep, running obliquely to the medial lip of the astragalus cochlea. The sulcus malleolaris is much deeper and narrower. It occurs at the posterior third of the bone, in medial view. The posterior apophysis is rounded and low, very broad. The medial lip of the astragalus cochlea is deeper (APD), more concave (transversally and sagittally) and narrower (transversally) than the lateral one. The latter is almost flat transversally.

Fibula ( Fig. 3F ). The only specimens are the fused tibia/fibula (AK7-40) and a distal epiphysis from a young individual (AK13-3). The proximal end is merely crushed. The thin diaphysis, with sharp ridges, thickens distally. The TD is twice lesser than the APD (Appendix: Table 15), so it keeps a slender shape in front view. Latero-distally, the sulcus malleolaris is deep, with sharp ridges, especially on the adult fibula. It is located in the posterior third of the bone. The astragalus-facet is flat, low, and nearly vertical.

Astragalus ( Fig. 2 E-G). The astragalus is well represented (11 specimens). It is a large, wide and deep bone ( TD /H ratio = 1.16; APD /H ratio = 0.70; Appendix: Table 16). On the lateral side, the fibula-facet is flat and nearly vertical. It forms a narrow stripe, tapering in its proximal quarter. The trochlea is high, with acute borders. The medial lip is shorter and more convex transversally than the lateral one. On the medial side, the articular surface corresponding to the malleolus medialis is narrow and it tapers regularly proximally. The caudal border of the trochlea is nearly straight in proximal view. The collum tali is high on adult specimens and even higher on juvenile specimens (AK2-438, AK6-56, AK5-319). The medial tubercle is very high, nearly reaching the mid-height of the bone, both in juveniles and adults. It is slightly salient from the trochlea, with a vertical medial border in anterior view. The posterior side shows three facets for the calcaneus, as usual. The facet 1 is strongly concave, with a distal horizontal ridge determining a wide latero-distal expansion. The latter forms a right angle with respect to the rest of the facet, both in juveniles and adults. The facet 2 is high, narrow, and oval-shaped. Its surface is strongly convex transversally. The facet 3 is always separate from the facet 2. The former is wide and low, almondshaped. In distal view, the trochlea is very oblique with respect to the axis of the distal articulation. This articulation (navicular and cuboid) is well developed. The navicular-facet is lozengic, while the cuboid-facet is wide and short (oval), with a smooth posterior break .

Calwaneus ( Fig. 3G, H ). The specimens are robust, with a massive tuber calcanei. The fibulafacet is lacking, while the tibia-facet is hugely developed and drop-shaped. The astragalus-facet 1 is question mark-shaped in lateral view. The facet 2 is oval, higher than wide and transversally concave. It is separate from the facet 3, which is smaller and almond-shaped. The sustentaculum tali is thick, but not wide (TD) when compared to the general dimensions of the bone (Appendix: Table 17). The proximal tip of the tuber calcanei is deeper (APD) than the processus in lateral view, but it is still massive. The cuboid-facet, on the distal side, is saddle-shaped and very wide. The insertion for the m. fibularis longus forms a smooth tubercle, without any sharp ridge.

Naviwular ( Fig. 3I, J ). Two specimens are preserved (Appendix: Table 18). They have a lozengic but subrectangular proximal outline; so is the outline of the proximal facet. The lateral facets are roughly separated. The proximal one runs all along the proximal border, while the distal one (hemicircular) is restricted to the posterior half of the bone. The distal side bears three facets for the cuneiforms. The ectocuneiform-facet is L-shaped and separated from the drop-shaped mesocuneiform-facet by a shallow groove. The entocuneiform-facet is smaller, semi-circular and oblique, whilst the ectocuneiform- and mesocuneiformfacets are horizontal.

Cuboid. The only specimen (AK5-636; Appendix: Table 19) lacks the distal part of the anterior side. The proximal articulation is oval and bears two facets. The medial one (astragalus) is oblique and flat transversally while the lateral one (calcaneus) is saddle-shaped: concave sagittally and convex transversally. They are separated by an acute sagittal ridge. On the medial side, the posterior facets are not equally developed: the proximal one is larger and much higher. The preserved part of the MtIV-facet, on the distal side, is flat and not elongated posteriorly. The posterior tuberosity is very high, vertical and not broad (TD) nor deep (APD).

EntowuneiForm ( Fig. 3K ). The only specimen (AK13-5) is large (Appendix: Table 20), with a laterally projected distal tuberosity. The proximal facet, for the navicular, is almond-shaped and biconcave. The ectocuneiform-facet is low and crescentiform, while the MtII-facet is nearly circular and flat. The distal border is horizontal, except for the developed latero-distal tuberosity, which is particularly salient. The posterior side is smooth, lacking any relief.

MesowuneiForm. It is semi-circular in proximal view. The proximal facet is flat transversally and concave sagittally. The anteromedial side is s m o o t h. T h e e n t o c u n e i f o r m -f a c e t i s s e m i - circular. The ectocuneiform-facet is long (APD) and low (Appendix: Table 21). The distal facet is flat sagittally and convex transversally, with a semi-circular outline.

EwtowuneiForm. The bone is low and wide (Appendix: Table 22). The navicular-facet occupies the whole proximal side. A broad tubercle for the m. interossei dorsales runs all along the anterior side. In anterior view, this side has a concave proximal border and a convex distal one. On the medial side, three facets are preserved: the antero-proximal one (for the mesocuneiform) is drop-shaped, with a higher posterior tip; the antero-distal facet (for the MtII) forms a distally truncated circle; the postero-distal facet is badly preserved. On the distal side, the MtIII-facet is convex transversally and flat sagittally.

MtII ( Fig. 4C, D ). The proximal end is triangular, in proximal view. The antero-medial side is lacking any proximal tubercle. The proximal facet, for the mesocuneiform, is kidney-shaped. On the posterior side, the entocuneiform-facet is high and it forms a proximally truncated oval (AK5-440), in contact with the proximal facet. On the lateral side, there are two facets. Both are high, separate from the proximal facet in AK5- 440. The anterior facet is oval and vertical. The posterior facet is rectangular and split into two equal halves. It is higher than the former and the sub-facets are rather distinct, owing to a horizontal ridge. The distal sub-facet corresponds to the MtIII. The insertion for the m. interossei dorsalis reaches the distal half of the diaphysis. The diaphysis is nearly straight, with a circular cross section. The distal widening is slight but present. The distal trochlea is deeper than wide (Appendix: Table 23), with parallel medial and lateral borders. In distal view, the anterior border is rounded, while the posterior one is sigmoid: the intermediate relief is low and smooth, displaced into the lateral half of the trochlea. The medial lip is concave, with a lateral deepening, whilst the lateral one is flat transversally, tapering laterally.

MtIII ( Fig. 4C, D ). Two complete adult specimens have been unearthed (GOK-7, AK2-163; Appendix: Table 24). Another one, lacking the distal epiphysis, belongs to a juvenile individual (AKA-44). They have comparable structures and proportions: they are rather slender, with straight diaphyses. The distal widening is very slight, except for AKA-44, where it is stronger. In proximal view, the proximal end is trapezium-shaped, with a straight medial border, a nearly straight lateral border, and a convex anterior border forming an open dihedron. There is no cuboidfacet. In anterior view, the proximal border is concave, higher laterally. The MtII-facets are high, semi-circular, the anterior one being lower. On the lateral side, the MtIV-facets are close to each other, only separate by a few millimetres. The anterior one is vertical, while the posterior one is visible in proximal view. Both are circular and equally developed. The insertion for the m. interossei is shorter for the MtII (proximal third) than for the MtIV (half of the diaphysis). There is no posterior tubercle on the posterior side of the diaphysis. The distal trochlea is deep (APD) and rather narrow (TD). It is much deep- er medially. The intermediate relief is low and smooth, but it is visible in anterior view. This relief determines two equally developed halves.

MtIV ( Fig. 4C, D ). There is a complete specimen (GOK-8, from the left metatarsus) and a proximal end (AK5-437). It is more robust than that of the MtII (Appendix: Table 25). The proximal outline is triangular, much wider than deep. The proximal facet, for the cuboid, is trapezoid, slightly concave transversally and sigmoid sagittally. The postero-lateral tuberosity is hugely developed and continuous, pad-shaped. It is partly destroyed on GOK-8. On the anterior side, the insertion for the m. fibularis is thick and salient. Between the cuboid-facet and the medial facets, runs a narrow oblique sagittal stripe, for the ectocuneiform. A few millimetres separate the MtIII-facets, which are circular and equally developed. The diaphysis is strongly curved and distally widened. It has a semi-circular cross section and a thick antero-distal tubercle. The distal articulation is trapezoid in distal view, and it has a smooth and low intermediate relief; the medial lip is flat, while the lateral lip is concave transversely. The insertion for the m. interossei forms a salient pad, which thickness almost reaches 1 cm.

No phalanx has been attributed to C. neumayri .

DISCUSSION

Ceratotherium neumayri is very widespread in the late Miocene of Greece, Turkey, and Iran ( Geraads 1988; Geraads F Koufos 1990; Saraç 1994; Heissig 1996). The most abundant rhinocerotid taxon in Akkasdagw ı bears cranial, dental, and postcranial features that are characteristic for C. neumayri : dolichocephalic two-horned skull, with a very broad and rounded nasal tip, a nearly flat dorsal profile, a forked occipital crest, a strongly inclined occipital side, long and edentulous premaxillae, forwards bent processus postglenoidalis, laterally projected orbits, short temporal crests, teeth rows restricted to the anterior half of the skull; no anterior constriction on the protocone nor antecrochet on the upper teeth, backw a r d s b e n t p r o t o l o p h s, m o l a r i f o r m u p p e r premolars, D1 lacking a metaloph, upper milk teeth with a crista; frequent absence of a trapezium-facet on the McII, early fusion of tibia and fibula, high and narrow medial tubercle on the astragalus, low and transversally convex calcaneus-facet 2 on the astragalus, low ectocuneiform, large articular facets between second and third metapodials, low and acute intermediate relieves on central metapodials; as a preliminary result of a cladistic analysis in process (Antoine unpubl. data), these features are provisionally assumed as diagnostic (autapomorphies) for C. neumayri .

According to age estimation of recent white rhinos ( C. simum ) by Hillman-Smith et al. (1986), the juvenile maxillae belong to individuals aged less than 1.5 year, meanwhile the adult skull corresponds to a 10-15 years old individual.

The dimensions of the remains found at Akkasdagw ı and identified as C. neumayri are very large (Appendix: Tables 1-25). The cranial and dental remains are equal in size and proportion to the average of C. simum , while the postcranials fit with the large individuals of the latter taxon ( Guérin 1980). Some bones are even larger (scaphoid, McII, patella, astragalus, cuneiforms, MtII), reaching the average size observed in Rhinoceros unicornis ( Guérin 1980) . In addition, several specimens of C. neumayri from Akkasdagw ı exceed in size the conspecific remains from other late Miocene Eastern Mediterranean localities, such as Samos, Maragha, Pikermi, Pentalophos-1, or Kemiklitepe ( Guérin 1980, 2000; Geraads 1988, 1994; Geraads F Koufos 1990; direct observation by P.-O. A.), being up to 10% larger than the largest specimens ever described for this species (radius, McII, astragalus, MtII; Guérin 2 000). According to Heissig (1975b) and Kaya (1994), the size of C. neumayri increases from the late Vallesian to the late Turolian in Turkey and Greece. The same tendency might exist between Kemiklitepe D (MN 11) and Kemiklitepe A+B (MN 12), but the material is scant ( Bonis et al. 1994; Geraads 1994). Even though latest Miocene (MN 12-13) localities bearing C. neumayri are too scarce to make a consistent comparison, there seems to be no contradiction between the large size of C. neumayri and the late middle Turolian age of Akkasdagw ı (MN 12), as argued owing to the associated fauna and radiometric ages ( Karadenizli et al. 2005).

Figures

FIG. 1. — Ceratotherium neumayri (Osborn, 1900), AkkaSdağı (Anatolia, Turkey), middle Turolian, skull (AK4-212); A, left lateral view; B, dorsal view; C, palatine view. Scale bar: 20 cm.

FIG. 2. — Ceratotherium neumayri (Osborn, 1900), AkkaSdağı (Anatolia, Turkey), middle Turolian; A, upper left series (P2-M3) from the skull AK4-212, occlusal view; B-D, left juvenile maxilla with D1-D3 and erupting D4 (AK5-502); B, occlusal view; C, labial view; D, lingual view; E-G, right astragalus (AK5-69); E, anterior view; F, posterior view; G, distal view. Scale bars: 5 cm.

FIG. 3. — Ceratotherium neumayri (Osborn, 1900), AkkaSdağı (Anatolia, Turkey), middle Turolian; A, right humerus, distal end (AK4- w.n.), posterior view; B, left radius, anterior view (AK5-627); C, D, right ulna (AK3-118); C, anterior view; D, medial view; E, right magnum, lacking the posterior tuberosity (AK7-38), medial view; F, left fused tibia and fibula (AK7-40), anterior view; G, H, left calcaneus (AK7-36); G, anteromedial view; H, posterolateral view; I, J, left navicular (AK4-76); I, proximal view; J, distal view; K, left entocuneiform (AK13-5), anterior view. Scale bars: 5 cm.

FIG. 4. — Ceratotherium neumayri (Osborn, 1900), AkkaSdağı (Anatolia, Turkey), middle Turolian; A, B, left metacarpus (GOK-2 to GOK-4); A, proximal view; B, anterior view; C, D, left metatarsus (GOK-7 to GOK-9); C, proximal view; D, anterior view. Scale bar: 5 cm.