Eocenochelus eremberti ( Broin, 1977 ) Pérez-García, Adán, Broin, France de Lapparent de & Murelaga, Xabier, 2017

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 : 9-13

publication ID	https://doi.org/ 10.26879/687
publication LSID	lsid:zoobank.org:pub:1D985176-5AD4-45FF-8BD7-C4AD17C7DE52
persistent identifier	https://treatment.plazi.org/id/03814F39-FFAC-4A3F-FF2D-E3E3F0C381B5
treatment provided by	Felipe
scientific name	Eocenochelus eremberti ( Broin, 1977 )
status	comb. nov.

Treatment

Eocenochelus eremberti ( Broin, 1977) comb. nov.

Figures 3-6.49 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6

1965 Podocnemys [sic] eremberti ; Taugourdeau, p. 165: nomen nudum

1977 Erymnochelys eremberti ; Broin, p. 89.

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

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

Holotype. MNHN.F CGR 101, a partial skeleton including the articulated skull with two anterior partial vertebrae, the fragmentary but partially reconstructed carapace, the relatively complete plastron, and various partial remains of the axial skeleton including a hyoid horn, the partial humerus, fragments of both scapulae, the two acromions with the partial glenoid part, a partial left coracoid, the partial femurs, the fragmentary right ilium, the left pubis and the left ischium ( Figures 3-6.49 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 ).

Type locality and horizon. Grande Terrasse of the Chateau de Saint-Germain-en-Laye, Saint-Germain-en-Laye, Yvelines, Île-de-France, France ( Figure 2 View FIGURE 2 ). “Banc Vert”, upper part of the Milioles limestone, Abrard’s zone 3, boundary below the “Marnes et Caillasses”, upper middle Lutetian, middle Eocene ( Taugourdeau, 1951; Aubry, 1986; Merle, 2008; Gély, 2009; White, 2013).

Diagnosis. Member of Eocenochelus with at least seven neurals, lacking medial contact of the sixth pair of costals (shared with Eocenochelus lacombianus but not with Eocenochelus farresi ); long pubic scar, being almost five times longer than wide (not shared with Eo. lacombianus and not known in Eo. farresi ); poorly developed posterior branch of the ischiatic scar, the distance from the posterior tip of this scar to the anal notch being greater than the maximum length of this branch (unique to this species); relatively long epiplastral symphysis, its length being about half of that of the entoplastron (shared with Eo. lacombianus but not with Eo. farresi ); intergular narrow, with subparallel margins throughout much of its path, and with the anterior border being much narrower than that of each gular (unique to this species); relatively short overlap of the latero-posterior region of the humeral scutes on the hyoplastra (shared with Eo. lacombianus but not with Eo. farresi ); subrounded lateral margins of the posterior plastral lobe (unique to this species); relatively wide and short anal notch, its full length being approximately about half of its width (shared with Eo. lacombianus but not with Eo. farresi ).

Description. The skull of MNHN.F CGR 101 is dorso-ventrally crushed ( Figure 3 View FIGURE 3 ). It lacks its posterior region. The length of the preserved region, measured on the axial plane, is about 11 cm. Most of the lower jaw, except the distal part of its left branch, is also preserved. Due to its preservation, the beak point is pushed in the fossa premaxillaris and the jaw has not been isolated from the skull. Therefore, the characters corresponding to the dorsal region of the jaw, and those corresponding to the anterior and lateral palate areas, are not known. The preserved region of the skull is subtriangular in dorsal view. The contour shows a slightly shortened and protrudent snout, the lateral borders widening just at the orbits, creating a weak lateral concavity, and diverging up to the quadratojugal area. The dorsal roof is weakly elevated, with a small elevation at the fronto-parietal suture. This skull lacks a premaxillary beak. The nares are rectangular, and wider than long. The snout is short, its length being less than one third of the length of the orbits. It lacks nasal bones. The prefrontals are slightly longer than wide. Their medial length is less than that of the frontals. The interorbital space is relatively wide, its minimum width being greater than the maximum length of the orbits. It lacks an interorbital Podocnemis groove or any longitudinal depression. The sutures between the prefrontals and the frontals, and those between the frontals and the parietals, are subperpendicular to the axial plane. The frontals are in contact with the postorbitals latero-posteriorly, and with the parietals posteriorly. The prefrontals, frontals and postorbitals delimit the dorsal margin of the orbits. The orbits are dorso-laterally located and elliptical. The postorbitals are longer than wide, completely separating the jugals from the parietals. The jugals are in contact with the maxillae and the orbits anteriorly, the postorbitals dorsally, and the quadratojugals posteriorly. The maxillae define the lower margin of the orbits. The suborbital space is higher than the orbits. The skull lacks a cheek emargination, the jugal going down between the quadratojugal and the maxilla, creating a wide straight ventral lateral border. The premaxillae separate the maxillae, both in the anterior and in the palatal views. The pterygoids are medially in contact. The left processus trochlearis pterygoidei is much externally eroded, and the right one is slightly incomplete. Its anterior face is not perpendicular to the axial plane, but posteriorly slightly directed. The basisphenoid is wider than long. It forms a short, obtuse wedge that penetrates between the rear regions of both pterygoids. The contact between the basisphenoid and the basioccipital is convex. A well-developed cavum pterygoidei is present, showing a large anterior opening. It was partly covered by the pterygoid wings, best preserved on the left side. Its wide dorsal opening in the sulcus cavernosus is visible on the right side. The condylus mandibularis quadrati seems neither particularly shortened nor relatively elongated in relation to its width.

The interparietal scute has a medial concavity on the anterior margin, with two short anterior arcs, forming a heart-shape. It does not contact the frontal bones. The frontal-parietal scutes boundary obliquely crosses the postorbital bones. The ventralmost region of the frontal scutes is located on the antero-dorsal area of the jugal bones. Probably the complete subocular scutes, but also the partial frontal, masseterian and maxillary scutes, overlap the jugals.

The lower jaw is very robust ( Figure 3.3-3.6 View FIGURE 3 ). Its labial margin, from the symphysis to the coronoid process, is nearly straight, the dorsally directed beak being therefore short. Due to the thickening of the dentary, its lateral surface lacks a concavity in ventral view. The mandibular symphysis, anteriorly ending in an acute angle, is long and constitutes about 40% of the total length of the lower jaw. Thus, it reaches the level of the foramen intermandibularis medius. The dorsal surface of the posterior region of the mandibular symphysis is not vertical, constituting a slope of about 45 degrees. The surangular is low laterodorsally and, below, the angular is long and laterally concave around the well-developed processus retroarticularis. In ventral view, the posteroventral foramen of the chorda tympani is visible, being fully enclosed in the jaw.

MNHN.F CGR 101 has a relatively large shell, the length of its plastron being of at least 60 cm ( Figures 4-5 View FIGURE 4 View FIGURE 5 ) and, therefore, being relatively long for its estimated width (estimated maximum width about 38 cm). The dorsal shell is decorated by the combination of several patterns: presence of millimetric short linear and dichotomic sulci; weakly undulated surface composed of small and very weak pits and granulations; presence of narrow and low rounded ridges, radially oriented from the vertebral and pleural centers of radiation ( Figures 4.4-4.6 View FIGURE 4 ). The outer surface of the plastron is decorated by sparce fine punctuations, weak pits and minute sulci ( Figure 5 View FIGURE 5 ). The carapace lacks a medial keel ( Figure 4 View FIGURE 4 ). It has at least seven neurals. At least the fifth and sixth neurals, partially preserved, are hexagonal in morphology, and long relative to their width. Their anterolateral-margins are shorter than the posterolateral. The anterior nuchal border is interpreted as not as elongated as that of the first pair of peripherals, considering the slightly rounded anterior border of these plates. The preserved three anterior and three posterior peripherals are relatively elongated, being approximately as long as wide. All of them are thinned in section toward the free border. The lip of the peripherals ninth and tenth, at the visceral boundary of the marginals, is not strongly developed. The axillary processes have a relatively long contact with the first pair of costals, anteriorly reaching the posterior margin of the second pair of peripherals. The inguinal processes contact the lateral region of the fifth costals. The iliac scars are located in the visceral region of both the seventh and the eighth costals. Posterior peripheral points are not present. The first vertebral is heptagonal, with short latero-anterior margins. It is wider than the nuchal plate. The overlap of the first pair of marginals on the nuchal is shorter than half of the length of the lateral side of this plate, but the second to fourth marginals are long, overlapping more than half of the length of the peripherals. Viscerally, the first marginal scute is very short, especially toward the medial region. However, the posterior marginals are long.

The posterior plastral lobe is narrower than the anterior ( Figure 5 View FIGURE 5 ). The anterior is trapezoid, with its lateral borders being anteriorly converging, its length being half of its width. It lacks gular protrusions. The epiplastral symphysis is relatively long, its length being about half of that of the entoplastron. The entoplastron is rhomboidal. The mesoplastra are subrounded, longer than wide. The lateral margins of the posterior plastral lobe are subrounded. The anal notch is relatively shallow, its length being about half of its width. Its lateral margins are also subrounded. The gular scutes are anteriorly wider and longer than the intergular. They meet medially. The intergular reaches the anterior entoplastron margin. It is narrow, with subparallel margins throughout much of its path. The posterior margins of the humerals are located on the anterior half of the entoplastron and on the epiplastra, except in the lateral region, where the humerals slightly overlap the hyoplastra. The pectoral scutes do not contact the mesoplastra. A relatively long distance separates the anal scutes from the hypoplastra. Thus, the anal scutes overlap on the lateral border of the xiphiplastra is longer than that of the femorals, although less than twice as long (anal margins about 30% longer than those of the femorals). The dorsal expansion of the plastral scute borders is very short. The oblique transversal pubic scar is relatively long and narrow, being almost five times longer than wide. The ischatic scar is slightly longer laterally than medially. It is not close to either the anal notch margin or the xiphiplastral point.

The preserved fragmentary postcranial bones are robust, compared with those of other members of Pleurodira , including Erymnochelys madagascariensis (see Gaffney et al., 2011; Lapparent de Broin and Murelaga 1999; Lapparent de Broin et al., 2004; Reinach, 1903; Tronc and Vuillemin, 1973) ( Figure 6.1-6.49 View FIGURE 6 ). They show the general pattern present in freshwater podocnemidid turtles such as Er. madagascariensis . The humerus has a wide open angle of 115° between the trochanters ( Figure 6.38-6.43 View FIGURE 6 ). As in Er. madagascariensis and in all the freshwater turtles, but also as in Bairdemys healeyorum , the femur is longer than the humerus, its shaft being relatively longer and robust ( Figure 6.44-6.49 View FIGURE 6 ). The scapula has a wide angle of about 90° with the acromion ( Figure 6.5- 6.14 View FIGURE 6 ), approximately as in B. healeyorum . The acetabular part is wide for its height: the height of the scapula and its acromion is relatively short at their fusion, and on the right scapulo-acromion remain, the width at the level of the corresponding coracoid sutural border is 68% of the height ( Figure 6.15- 6.19 View FIGURE 6 ). The pelvis is short, being composed by relatively massive elements ( Figure 6.20-6.37 View FIGURE 6 ). The iliac body is wide and not medially narrowed, short for its height between the suture with the pubis and the proximal widening for the eroded costal scar part ( Figure 6.26-6.31 View FIGURE 6 ). The pubis is relatively low, its width being 103% of its height at the medial acetabular border ( Figure 6.32-6.37 View FIGURE 6 ). The ischium is also low and, mediolaterally, its shaft is slightly narrowed, being rounded below the proximal extremity ( Figure 6.20-6.35 View FIGURE 6 ). The preserved ventral suture with the xiphiplastron is anteromedially short, according to the scar on the plastron ( Figure 5.3- 6.4 View FIGURE 5 View FIGURE 6 ).