Eopelobates, Parker, 1929
|
publication ID |
https://doi.org/ 10.26879/772 |
|
persistent identifier |
https://treatment.plazi.org/id/03FD514F-EC5E-FFF5-FE8B-FE1410222BE7 |
|
treatment provided by |
Felipe |
|
scientific name |
Eopelobates |
| status |
|
Eopelobates aff. Eopelobates bayeri
Figures 1-2 View FIGURE 1 View FIGURE 2
Material. Volchaya Balka locality: two frontoparietals (GIN 1143-200, 201); 10 maxillae (GIN 1143- 202–211); nine presacral vertebrae (GIN 1143- 212–220); one sacral vertebra (GIN 1143-221); one ilium (GIN 1143-222).
Description. The frontoparietal ( Figure 1.1-4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 ) is represented by two posterolateral fragments of the bone. The dorsal surface of the frontoparietal complex is flat and covered by small and rounded shallow pits, which are bordered by smooth ridges (= pit-and-ridge sculpture sensu Roček et al., 2014) located along the posterolateral margin of the bone. The median portion of the frontoparietal is unsculptured. The lateral margin of the dorsal, sculptured surface is nearly straight, does not extend laterally into the tectum supraorbitale and was not in contact with the squamosum. Anteriorly, it shows a partly broken processus lateralis inferior. The margo prootica is slightly concave. The posterolateral part of the frontoparietal forms a well-developed paraoccipital process (= processus paraoccipitalis), which is distally obtuse. It bears the foramen arteriae occipitalis, which is placed medially to the base of the paraoccipital process and is not hidden in dorsal view. Laterally, the foramen is bordered by small crests. The medial one is triangular and extended slightly beyond the posterior margin of the frontoparietal. The posterior bor- der of the bone was convex. Ventrally, the frontoparietal surface is slightly concave. Only the posterolateral part of the frontoparietal incrassation (= incrassatio frontoparietalis) is visible. It has welldelimited margins and the posterior one is slightly concave. There is a deep groove situated on the anterior border of the processus lateralis inferior in the specimen GIN 1143-201 ( Figure 1.4 View FIGURE 1 ), representing the sulcus arteriae occipitalis.
The maxilla ( Figure 1.5 View FIGURE 1 -10) is represented mostly by various central parts of the bone, lacking the processus posterior and lamina anterior (= rostellum). All the specimens are fully covered by sculpture, which is similar to that of the frontoparietal. In some areas the pits are anteroposteriorly elongated and may partially coalesce. The zygomaticomaxillar process (= processus zygomaticomaxillaris) is not preserved. The margo orbitalis is deeply concave. The processus frontalis is partly exposed and projects at an oblique angle. The fossa maxillaris is relatively shallow. The lamina horizontalis is wide and projects lingually. It terminates in a wide and short pterygoid process (= processus pterygoideus). The tooth row reaches the posterior termination of the horizontal lamina or only slightly extends behind it.
The vertebrae ( Figure 2.1 View FIGURE 2 -8) are represented by several incomplete presacrals and one fragmentary sacrum. The presacral vertebrae ( Figure 2.1 View FIGURE 2 -5) are procoelous with elongated and cylindrical centra. Their neural arches in dorsal view are anteroposteriorly elongated and flattened, not imbricated. Anteriorly they are variously concave, posteriorly only two vertebrae form a very short pointed median process. The transverse processes (= processus transversus) are partly preserved only in two vertebrae. These vertebrae bear thin and anteriorly inclined transverse processes, which indicates that they come from the posterior section of the presacral region. In both lateral views, the neural arches of all presacral vertebrae surround the large spinal foramina.
The sacral vertebra ( Figure 2.6 View FIGURE 2 -8) consists of a long procoelous centrum, neural arch, and incomplete right transverse process. The cotyle is deep and circular. The condyle is cylindrical and well outlined. It is not fused with the urostyle. The neural canal is dorsoventrally compressed. The transverse processes are incomplete, but reconstructed as a broadly dilated. The prezygapophyses are well developed and extended laterally. Because the posterior part of both sacral wings is broken off it cannot be decided whether there was a sign of an additional transverse process of the first caudal vertebra, which is marked by a ledge on the impression of Eopelobates anthracinus (see Roček et al., 2014, fig. 2d). In the lateral and posterior views, the large spinal foramina are visible.
The all ilia ( Figure 2.9 View FIGURE 2 -11) are fragmentary. They lack the tuber superior and the iliac crest. The acetabular region is nearly triangular. The processus ascendens is relatively wide, whereas the processus descendens is short, slightly concave anteriorly. The spiral groove is relatively poorly developed. The medial surface of the acetabular region is only slightly striated and the interiliac synchondrosis is undeveloped.
Comments. The described elements are assigned to Eopelobates based on the sculpture of the frontoparietal and maxilla developed as small shallow pits (= pit-and-ridge pattern) and absence of frontoparietal-squamosal contact. The pit-and-ridge sculpture is also characteristic of the Oligo-Miocene Pelobates clade (sensu Venczel, 2004), where it consists of well-marked pits and ridges, contrary to relatively smooth and shallow pits and ridges in Eopelobates . In addition, the frontoparietals GIN 1143-200 and GIN 1143-201 are not ornamented along the midline, which is typical for Eopelobates . The flat dorsal surface of the described frontoparietal is also in contrast to those of most Pelobates species (except an undescribed species from the middle Miocene of Petersbuch 38; Böhme, 2010), which have a convex dorsal surface. The morphology of vertebrae in Caucasian frog points to both Eopelobates and Oligo-Miocene Pelobates . The spinal nerve foramina in presacral vertebrae are known in Eopelobates and in the Oligo-Miocene Pelobates . The condition of sacral vertebra, i.e., its fusion or not with the urostyle, varies in Pelobates , but these elements are generally fused in the Recent Pelobates species and free in Eopelobates and Oligo-Miocene Pelobates . The morphology of the described ilium (shallow spiral groove between the iliac shaft and acetabulum and poorly developed interiliac synchondrosis) also points to Eopelobates rather than to the Pelobates .
Currently, four species of Eopelobates are known in Europe and only one of them ( E. bayeri ) survived into the Miocene. Eopelobates from Volchaya Balka differs from E. anthracinus by sculpture of the frontoparietal consisting of small pits, and is similar to E. bayeri and E. hinschei in having the greater part of the maxilla sculpture covered. But it differs from E. bayeri in the free sacral vertebra (fused with urostyle in E. bayeri ). But, within the material assigned to E. bayeri , a variation may exist with respect to the sacro-urostylar connection—by a concrescence, or by a joint ( Estes, 1970; Hodrová, 1988). All known species of Eopelobates are preserved as flattened skeletons, thus the fragmentary remains of Eopelobates from Volchaya Balka cannot be undoubtedly determined to a species level. Taking into consideration the chronological proximity (Miocene) of E. bayeri and Eopelobates from Volchaya Balka, we tentatively attribute the latter to Eopelobates aff. E. bayeri . At the same time, Eopelobates from Volchaya Balka is highly similar to Eopelobates sp. from the late Miocene of Suchomasty ( Hodrová, 1987a) in shape of posterolateral part of the frontoparietal and frontoparietal incrassation, and sculpture. Thus, Eopelobates from Volchaya Balka and Eopelobates sp. from Suchomasty may belong to a same form.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.