Helladotherium, Gaudry, 1860

Kostopoulos, Dimitris S. & Saraç, Gercek, 2005, Giraffidae (Mammalia, Artiodactyla) from the late Miocene of Akkaşdağı, Turkey, Geodiversitas 27 (4), pp. 735-745 : 736-739

Helladotherium sp.

MATERIAL EXAMINED AND MEASUREMENTS (in mm). — P3 left (AK7-29): L occl = 34.0, W occl = 26.0, W alv = 38.5; M2 right (AK2-441): L occl = 46.8, W max-anterior lobe = 44.0, W max-posterior lobe = 41.0; radius left (AK7- 64): L max = 580.0, DT prox = 123.0, DAP prox = 73.0, DT diaph = 78.8, DAP diaph = 60.0, DT dist-art = 101.3, DAP dist-art = 62.2; tibia right (AK7-129): L = 540.0, DT prox-max = 166.5, DAP prox = 130+, DT diaph = 74.5, DAP diaph = 53, DT dist = 106.2, DAP dist = 82.4); part of calcaneus (GOK-200): L sustentaculum tali = 167.0; talus (GOK-197): L lat = 115.5, L med = 99.3, DT dist = 76; cubonavicular (AK7-101): DT max = 100.0, DAP max = 99.0; phalanx I (AK7-152): L = 114.0, DT prox = 53.2, DAP prox = 58.2, DT dist = 47.2, DAP dist = 35.3; (AK3- 310): L = 109.2, DT dist = 42.5, DAP dist = 33.7; (GOK-201): L = 115.0, DT prox = 52.5, DAP prox = 56.3, DAP dist = 41.2; phalanx II (AK7-35a): L = 62.5, DT prox = 45.3, DAP prox = 46.2, DT dist = 40.8, DAP dist = 44.5; (AK7-27): L = 65.4, DT prox = 46.4, DAP prox = 46.2, DT dist = 43.5, DAP dist = 44.5; phalanx III (AK7- 35b): DT art = 35.0, H art = 58.6.

Provisionally ascribed: metacarpal III+IV of immature individual (AK7-65): DT prox = 87.5, DAP prox = 55.0, DT diaph = 50.0, DAP diaph = 42.5.

DESCRIPTION AND DISCUSSION ( FIGS 1-4 )

The cranial elements are limited to two isolated teeth with finely rippled enamel and barely visible cingulum ( Fig. 1 ). The P3 is large with strong parastyle and well developed paracone rib. The internal side of the labial crescent is weakly divid- ed into paracone and metacone. The occlusal surface looks sub-quadrangular with an antero-lingual protuberance of the lingual wall and a clear hypoconal spur on the central cavity ( Fig. 1 ). The M2 has simple morphology with strong parastyle, slim but well built mesostyle, weak metastyle and strong paracone rib. The lingual wall of the protocone is rounded, while the hypocone is slightly narrower and more angular lingually. The anterior flange of the protocone is connected with the parastyle; its posterior flange is short, curves anteriorly and do not confine the posterior flange of the hypocone. A relatively strong hypoconal spur is present ( Fig. 1 ).

The absence of cranial or more complete dental material makes the identification of the largest giraffid from Akkaşdagwı quite difficult. Similar sized Turolian forms are usually referred to the genera Samotherium Forsyth-Major, 1888 and Helladotherium Gaudry, 1860 which however, belong to different phylogenetic lineages, the Palaeotraginae and Sivatheriinae respectively ( Bohlin 1926; Hamilton 1978; Geraads 1986). Geraads F Güleç (1999) mention that the type specimen of Helladotherium duvernoyi Gaudry, 1860 , type species of the genus, belongs to a female individual of a different genus and, recalling Matthew’s statement ( Matthew 1929: 550 fide Hamilton 1978: 218) they suggest a provisional synonymy of Helladotherium with Bramatherium Falconer, 1845 . Although quite possible, this synonymy is not yet formally founded and, following Hamilton (1978), we shall continue to use Helladotherium as a valid taxon.

According to Bohlin (1926) and Geraads (1974), Helladotherium differs from Samotherium in the larger premolar row relatively to the molars, the unmolarized p3, the less developed styles on the cheek teeth and the more massive limbs.

At first sight the large P3 from Akkaşdagwı, significantly larger than usually recorded in Samotherium and notably large comparatively to M2, indicate the presence of Helladotherium ( Fig. 2 ). In contrast to the studied specimen and Helladotherium , the P3 of Samotherium is more rounded and presents stronger metastyle and more centrally placed paracone-metacone pillar. The M2 structure (thin mesostyle, posterior

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flange of the protocone, presence of hypoconal spur, etc.) also differentiates the studied specimen from Samotherium , supporting close relationships with Gaudry’s genus. However, the available M2 appears relatively narrower than that of the type species Helladotherium duvernoyi from Pikermi (MNHN, BMNH, LGPUT) and closer to the Maragha ( Iran; MNHN, BMNH) and Kerassia ( Greece; Iliopoulos 2003) samples.

Although more robust, the dimensions of the postcranials of Helladotherium are usually hardly distinguished from those of the large samotheres (e.g., S. major Bohlin, 1926 and S. sinense Bohlin, 1926 ). The limb proportions of the studied specimens from Akkaşdagwı are placed between those of Samotherium and Helladotherium , being closer to the second genus.

Differently from Samotherium boissieri Forsyth- Major, 1888 and S. major , the proximal articulation of the preserved metacarpal, provisionally ascribed to Helladotherium , presents a large synovial fossa, which opens widely towards the cau- dal face. This character strongly recalls Helladotherium from Pikermi but also Samotherium sinense ( Bohlin 1926: fig. 103), while the immaturity of the individual may influence the fossa pattern (Geraads pers. comm. 2004). Regarding the absolute dimensions, this young individual falls, however, within the range of large samotheres, indicating probably an even larger and stouter adult animal, hence, closer to those of Helladotherium .

The rectangular epiphyses of the complete radius AK7-64 are not significantly wider than the shaft ( Fig. 3A ), the lateral tuberosity is weak, the radial tuberosity is placed below the medial proximal articular surface, the antero-lateral corner of the proximal part forms an almost right angle, the radial styloid process is more projected downwards than the ulnar one, the shallow groove of the extensor capri rarialis muscle is defined by two blunt crests of more or less equal length and it is symmetrically located above the medial ulnar ridge, the groove of the abductor digiti I longus muscle is shal- low and located rather anteriorly than medially, the anterior margins of the distal articular facets are low, the anterior part of the scaphoid facet is rather quadrangular with flat anterior border bended medially, the anterior part of the lunar facet is spindle-shaped with clear posterior margin, the lateral crest of the lunar is shorter, less prominent and more oblique than the medial one, the articular surface for the cuneiform is rather narrow and the transverse crest of the posterior face is weakly developed ( Fig. 4 ).

The tibia (AK7-129, Fig. 3B ) is relatively long a n d m o d e r a t e l y r o b u s t (D T d i a p h × 1 0 0/L = 13.5). The tibial crest is relatively short, laterally located, not very prominent and with wideshallow tuberosity. Consequently, in the upper part of the anterior face the restricted tibial sulcus is oval-shaped and not very deep. The tibial spine is relatively high. A small facet for the fibula is present at the lateral side. The muscle imprint at the posterior side of the bone is located in the medial part of the diaphysis. The antero-lateral tuberosity of the distal part is weakly developed. Both the medial malleolus and the lateral malleolar facets of the distal epiphysis are strong.

The dorsal and plantar edges of the calcaneus are rectangular. The large talus has strongly assymetrical proximal trochlea, the scar for the external tendon of the cubonavicular is missing and the limit between the articular facets for the calcaneum and the cubonavicular is well marked. The cubonavicular is almost square with extremely developed caudal tuberosity, coating the proximal articular surface. The posterior metatarsal facet is present. The first phalanx is large and robust.

This set of postcranial morphological characters rules out the association with Samotherium and place the Akkaşdagwı form closer to Helladotherium ( Bohlin 1926; Geraads 1974; Iliopoulos 2003; Iliopoulos pers. comm. 2004; pers. data). Nonetheless, the observed morphological features are not fully identical to those of the Pikermian form (BMNH sample), suggesting either a larger intraspecific variability for Gaudry’s species or – less possibly – a distinction at a higher taxonomic level. In the absence of adequate data we refer at the moment this form to Helladotherium sp.

Figures

FIG. 1. — Helladotherium sp., Akkaşdağı, Turkey, occlusal view; A, M2 right; B, P3 left. Scale bar: 1.5 cm.

FIG. 2. — Scatter diagram “Width of P3 against Width of M2” of Helladotherium sp., Akkaşdağı, Turkey (N) in comparison with Helladotherium duvernoyi from Kerassia (KER), Pikermi (PIK, several collections); Samotherium major from Vathylakkos (VAT), Kemiklitepe B (KTB), Taşkınpaşa (TAS); Samotherium boissieri from Samos (MGL and BMNH collections); S. sinense (China) and S. neumayri (Maragha) (data from Bohlin 1926; Şenyürek 1954; Geraads 1974, 1994; Iliopoulos 2003; and pers. data).

FIG. 3. — Helladotherium sp., Akkaşdağı, Turkey, anterior view; A, left radius AK7-64; B, right tibia AK7-129. Scale bar: 5 cm.

FIG. 4. — Helladotherium sp., Akkaşdağı, Turkey, distal articulation of radius AK7-64. Scale bar: 2 cm.