ERYMNOCHELYINAE Broin, 1988

Pérez-García, Adán, Broin, France de Lapparent de & Murelaga, Xabier, 2017, The Erymnochelys group of turtles (Pleurodira, Podocnemididae) in the Eocene of Europe: New taxa and paleobiogeographical implications, Palaeontologia Electronica 15 (2), pp. 1-28 : 7

Subfamily ERYMNOCHELYINAE Broin, 1988

ERYMNOCHELYS GROUP sensu Pérez-García and Lapparent de Broin, 2015

Genus Eocenochelus gen. nov.

Figures 3-8

zoobank.org/ EC68A3B2-1722-4B33-B2F7-D6ED3011287B

1965 Podocnemys [sic]; Taugourdeau, p. 165.

1977 Erymnochelys ; Broin, p. 89.

2008 ‘aff. Erymnochelys ’; Lapparent de Broin in Merle, p. 154, pl. 9, figure 2.

2015 ‘aff. Erymnochelys ’; Pérez-García and Lapparent de Broin, p. 915.

Type species. Erymnochelys eremberti Broin, 1977

Other included species. Eocenochelus lacombianus sp. nov.; Eocenochelus farresi sp. nov.

Etymology. This generic name refers to the Eocene, the Epoch in which this taxon lived, and chelus (Greek), turtle.

Distribution. Eocene (middle Ypresian to Priabonian) of Europe.

Diagnosis. Member of the Erymnochelys group with the following autapomorphies: Wide interorbital space, its minimum width being greater than the maximum length of the orbits; suborbital space markedly higher than the orbits; absence of a cheek emargination by the wide insertion of the jugal between the maxilla and the quadratojugal; medial concavity of the interparietal scute anterior margin; absence of overlap of the interparietal on the frontals; very robust mandible, with substraight labial margins, from the coronoid process to the fossa premaxillaris; high and robust dentary, wide in ventral view, without lateral border concavity; long mandibular symphysis, about 40% of the total length of the lower jaw, reaching the level of the foramen intermandibularis medius; and dorsal surface of the posterior border of the mandibular symphysis not vertical but constituting a slope of about 45º. It is distinguished from the other representatives of the Erymnochelys group by an exclusive combination of cranial characters: Short anterior snout, less than half of the length of the orbits (shared with T. pattersoni ); wider than long nares (shared with ‘Podocnemis’ fajumensis and Erymnochelys madagascariensis ); absence of premaxillary beak (shared with ‘P.’ fajumensis); absence of an interorbital longitudinal depression (shared with Turkanemys pattersoni , Er. madagascariensis and some specimens of ‘P.’ fajumensis); prefrontals shorter than frontals (shared with ‘P.’ fajumensis); transverse to slightly sinuous prefrontal-frontal contact, lacking a medial protusion (shared with T. pattersoni and Er. madagascariensis ). It is also distinguished from the other representatives of the Erymnochelys group by an exclusive combination of shell characters: Absence of a partial or complete medial keel on the carapace (shared with ‘P.’ fajumensis, ‘Podocnemis’ aegyptiaca, Er. madagascariensis and most specimens of T. pattersoni ); first vertebral heptagonal, with short latero-anterior margins, and as wide or wider than the nuchal plate (shared with ‘P.’ fajumensis, ‘Podocnemis’ aegyptiaca, T. pattersoni and Er. madagascariensis ); second vertebral approximately as wide as the third, both scutes lacking wide lateral protrusions anterior to the limit between the pleural sulci (shared with ‘P.’ fajumensis, T. pattersoni , Kenyemys williamsi and Er. madagascariensis ); first pair of marginals overlapping no more than half of the length of the lateral nuchal margins (shared with ‘P.’ fajumensis, ‘P.’ aegyptiaca, T. pattersoni and Er. madagascariensis ); posterior plastral lobe narrower than the anterior (shared with T. pattersoni and Er. madagascariensis ); absence of clear gular protrusions with parallel borders (shared with ‘P.’ aegyptiaca, T. pattersoni , Er. madagascariensis and some specimens of ‘P.’ fajumensis); relatively long intergular scute, reaching the anterior margin of the entoplastron or overlying its most anterior region (shared with ‘P.’ fajumensis, ‘P.’ aegyptiaca, T. pattersoni and some Er. madagascariensis ); moderate length of the anal scutes, being shorter than two times the femoral length on the lateral borders of the xiphiplastra (shared with ‘P.’ fajumensis and ‘P.’ aegyptiaca); very short dorsal expansion of the plastral scute borders (shared with ‘P.’ aegyptiaca, T. pattersoni , K. williamsi and Er. madagascariensis ).

Figures

FIGURE 3. Skull of the holotype of Eocenochelus eremberti comb. nov., MNHN.F CGR 101, from the middle Eocene (Lutetian) of Saint-Germain-en-Laye (Yvelines, Île-de-France, France), in dorsal (1–2), ventral (3–4) and right lateral (5–6) views. Abbreviations: ane, apertura narium externa; ang, angular; bo, basioccipital; bs, basisphenoid; cm, condylus mandibularis; cpt, cavum pterygoidei; cv, cervical vertebra; den, dentary; ex, exoccipital; fct, foramen anterius chorda tympani; fo, fossa orbitalis; fpo, fenestra postotica; fpp, foramen palatinum posterius; fr, frontal; FR, frontal scute; fst, foramen stapedio-temporale; IP, interparietal scute; ju, jugal; MS, masseterian scute; mx, maxilla; MX, maxillary scute; op, opisthotic; pa, parietal; PA, parietal scute; pal, palatine; pf, prefrontal; pm, premaxilla; po, postorbital; pr, prootic; pt, pterygoid; ptp processus trochlearis pterygoidei; pw, pterygoid wing; q, quadrate; qj, quadratojugal; so, supraoccipital; SO, subocular scute.

FIGURE 4. Some elements of the carapace of the holotype of Eocenochelus eremberti comb. nov., MNHN.F CGR 101, from the middle Eocene (Lutetian) of Saint-Germain-en-Laye (Yvelines, Île-de-France, France). 1–2, plates of the carapace, in dorsal and ventral views. 3–4, reconstruction of the dorsal view of the shell, showing the position of all these elements of the carapace. 4–6, details of the outer surface of some plates of the carapace: the second left peripheral (4), the distal region of the sixth right costal (5), and the proximal region of the fourth left costal (6). Abbreviations: c, costal; M, marginal scute; n, neural; p, peripheral; PL, pleural scute; py, pygal; V, vertebral scute.

FIGURE 5. Plastron of the holotype of Eocenochelus eremberti comb. nov., MNHN.F CGR 101, from the middle Eocene (Lutetian) of Saint-Germain-en-Laye (Yvelines, Île-de-France, France), in ventral (1–2) and dorsal (3–4) views. Abbreviations: AB, abdominal scute; AN, anal scute; en, entoplastron; ep, epiplastron; FE, femoral scute; GU, gular scute; hp, hypoplastron; HU, humeral scute; hy, hyoplastron; IG, intergular scute; M, marginal scute; ms, mesoplastron; PC, pectoral scute; xi, xiphiplastron.

FIGURE 6. Fragmentary skeletal bones of the holotypes of Eocenochelus eremberti comb. nov., MNHN.F CGR 101, from the middle Eocene (Lutetian) of Saint-Germain-en-Laye (Yvelines, Île-de-France, France) (1–49), and Eocenochelus lacombianus sp. nov., MNHN.F EBA 534, from the lower Eocene (Ypresian) of Soulane (Jonquières, Aude, France) (50–57). 1–4, left hyoid horn, second branchial horn, in dorsal (1), medial (2), ventral (3) and lateral (4) views. 5–9, acromion of the right scapula with the partial glenoid articular region, in posterior (5), ventral (6), anterior (7) and dorsal (8) views, and articular part in ventrolateral view (9). 10–14, acromion of the left scapula with the partial glenoid articular region, in posterior (10), ventral (11), anterior (12) and dorsal (13) views, and proximal articular section (14). 15–19, left coracoid in dorsal (15), posteroventral (16), ventral (17) and anterior (18) views, and articular-glenoid facet part, in proximal view (19). 20–25, left ischium, in anterior (20), medial (21), posterior (22) and distal (23) views, and dorsal (24) and ventral (25) sections. 26–31, right ilium, in posterior (26), lateral (27), anterior (28) and medial (29) views, and dorsal (30) and ventral (31) sections. 32–37, left pubis, in anterior (32), medial (33), posterior (34) and lateral (35) views, proximal articular-acetabular region in dorsal view (36), and ventral section (37). 38–43, left humerus, in anterior (38), ventral (39), posterior (40) and dorsal (41) views, and proximal (42) and distal (43) sections. 44–49, right femur, in anterolateral (44), ventral (45), posteromedial (46) and dorsal (47) views, and proximal (48) and distal (49) sections. 50–53, right hemipelvis, in lateral (50), posterior (51), anterior (52) and medioventral (53) views. 54–57, left hemipelvis, in lateral (54), posterior (55), anterior (56) and medial (57) views.

FIGURE 7. Shell of the holotype of Eocenochelus lacombianus sp. nov., MNHN.F EBA 534, from the lower Eocene (Ypresian) of Soulane (Jonquières, Aude, France). 1–2, carapace, in dorsal view. 3–4, carapace, in ventral view. 5, reconstruction of the dorsal view of the shell, showing the position of the preserved elements of the carapace. 6–7, plastron, in ventral view. 8–9, plastron, in dorsal view. Abbreviations: AB, abdominal scute; AN, anal scute; c, costal; en, entoplastron; ep, epiplastron; FE, femoral scute; GU, gular scute; hp, hypoplastron; HU, humeral scute; hy, hyoplastron; IG, intergular scute; M, marginal scute; ms, mesoplastron; n, neural; nu, nuchal; p, peripheral; PC, pectoral scute; PL, pleural scute; py, pygal; V, vertebral scute; xi, xiphiplastron.

FIGURE 8. Shell of the holotype of Eocenochelus farresi sp. nov., MGSB 74.641-GLV.T.45, from the upper Eocene (Priabonian) of Can Beuloví (Sobremunt, Barcelona, Spain), in dorsal (1–2) and ventral (3–4) views. Abbreviations: AB, abdominal scute; AN, anal scute; c, costal; en, entoplastron; ep, epiplastron; FE, femoral scute; GU, gular scute; hp, hypoplastron; HU, humeral scute; hy, hyoplastron; IG, intergular scute; M, marginal scute; ms, mesoplastron; n, neural; p, peripheral; PC, pectoral scute; PL, pleural scute; py, pygal; V, vertebral scute; xi, xiphiplastron.