Pelorochelon, Adán Ṕerez-Garćia, Francisco Ortega & Emiliano Jiménez Fuentes, 2016

Adán Ṕerez-Garćia, Francisco Ortega & Emiliano Jiménez Fuentes, 2016, Taxonomy, systematics, and diversity of the European oldest testudinids, Zoological Journal of the Linnean Society 177, pp. 648-675 : 657

PELOROCHELON GEN. NOV.

( FIGS 2 , 3 , 4, 5 , 6 E, F, G, H)

Type species. Pelorochelon soriana sp. nov.

Other included species. Pelorochelon eocaenica ( Hummel, 1935) .

Etymology. Peloro -, meaning monstrous and gigantic in Greek, because it is the European oldest known testudinid with a shell of more than 50 cm, and the largest testudinid in the European Eocene record; and - chelon, from the ancient Greek word χελώνη (cheloni), which means turtle or tortoise.

Distribution. Eocene (Ypresian to Bartonian) of Europe.

Diagnosis. Western European Cenozoic testudinid, with the length of the shell close to 70 cm, differing from all the medium and large European testudinids by the presence of a well-developed visceral elevation in the lateral margin of the epiplastra, expanded toward the anterior region, and characterized by a unique character combination: shallow notch in the anterior carapace margin; slightly wider than long nuchal; eight to nine neurals; first suprapygal embrassing the lenticular second one; dorsally directed distal margins of the anterior and posterior peripherals; absence of pointed tips in the anterior and posterior carapacial rim; posterior carapace margin not undulating; presence of a cervical scute; cervical almost as wide as long; markedly divergent latero-posterior margins of the first vertebral scute; third vertebral longer than wide; first pair of pleurals not overlapping the nuchal; third pleural contacting the seventh to ninth pair of marginals; medial margins of the marginals not contacting the costo-peripheral suture; second marginals not contacting the nuchal; fourth marginals medially in contact with the first pleurals; presence of twelve pairs of marginals; overlap of the twelfth marginals on the second suprapygal; anterior plastral lobe as long as the posterior one; medially notched anterior plastral lobe; concave dorsal lip of the epiplastra; presence of gular protrusions; absence of gular pocket; absence of step-like morphology behind the epiplastral lip; epiplastra as long as wide; sutured contact between all plastral plates; gular scutes not contacting or not overlying the anterior region of the entoplastron; anterior angle between the sagittal axis and the gularo-humeral sulcus of 65° or more obtuse; humero-pectoral sulcus generally perpendicular to the axial plane in the medial area, with a well-developed lateral change of curvature.

Figures

Figure 2. STUS 14223, holotype of Pelorochelon soriana, from the early Bartonian (middle Eocene) of the Spanish site of Mazateŕon (Soria Province), in dorsal (A) and ventral (B) views. Scale bar = 10 cm.

Figure 3. Some of the paratypes of Pelorochelon soriana, from the early Bartonian (middle Eocene) of the Spanish site of Mazateŕon (Soria Province). A, shells STUS 14227 and STUS 14228, in ventral view. B, shells STUS 14229 and STUS 14230, in dorsal view. C, STUS 14399, anterior half of a shell, in dorsal (C 1) and ventral (C 2) views. D, STUS 14398, anterior half of a shell, in dorsal (D 1) and ventral (D 2) views. Scale bar = 10 cm.

Figure 5. Some of the paratypes of Pelorochelon soriana, from the early Bartonian (middle Eocene) of the Spanish site of Mazateŕon (Soria Province). A, STUS 8707, right epiplastron, in ventral (A 1), dorsal (A 2), anterior (A 3), and lateral (A 4) views. B, STUS 13802, left epiplastron, in dorsal (B 1), ventral (B 2), anterior (B 3), and lateral (B 4) views. C, STUS 11698, right epiplastron, right half of the entoplastron and anterior region of the right hyoplastron, in ventral (C 1), dorsal (C 2), anterior (C 3), and lateral (C 4) views. D, STUS 10857, right epiplastron, in ventral (D 1) and dorsal (D 2) views. E, STUS 10849, left epiplastron, in dorsal (E 1) and ventral (E 2) views. F, STUS 11697, left epiplastron and left half of the entoplastron, in dorsal (F 1) and ventral (F 2) views. G, STUS 10843, right epiplastron, in ventral (G 1) and dorsal (G 2) views. H, STUS 13753, left epiplastron, in dorsal (H 1) and ventral (H 2) views. I, STUS 11693, left epiplastron, in dorsal (I 1) and ventral (I 2) views. J, STUS 10850, right epiplastron, in ventral (J 1) and dorsal (J 2) views. K, STUS 10852, left epiplastron, in dorsal (K 1) and ventral (K 2) views. L, STUS 11695, left epiplastron, in dorsal (L 1) and ventral (L 2) views. M, STUS 10853, left epiplastron, in dorsal (M 1) and ventral (M 2) views. N, STUS 13763, left epiplastron, in dorsal (N 1) and ventral (N 2) views. O, STUS 11694, left epiplastron, in dorsal (O 1) and ventral (O 2) views. P, STUS 13736, right epiplastron, in ventral (P 1) and dorsal (P 2) views. Q, STUS 13762, left epiplastron, in dorsal (Q 1) and ventral (Q 2) views. R, STUS 13754, left epiplastron, in dorsal (R 1) and ventral (R 2) views. S, STUS 10860, right epiplastron, in ventral (S 1) and dorsal (S 2) views. T, STUS 10864, right epiplastron, in ventral (T 1) and dorsal (T 2) views. U, STUS 10856, right epiplastron, in ventral (U 1) and dorsal (U 2) views. V, STUS 10861, left epiplastron, in dorsal (V 1) and ventral (V 2) views. W, STUS 10814, left epiplastron, in dorsal (W 1) and ventral (W 2) views. Scale bar = 10 cm.