Pelobatidae BONAPARTE , 1850

Rage, Jean-Claude, 2016, Frogs (Amphibia, Anura) From The Eocene And Oligocene Of The Phosphorites Du Quercy (France). An Overview, Fossil Imprint 72 (1 - 2), pp. 53-66 : 55-56

Pelobatidae BONAPARTE, 1850

( Text-fig. 2 : 7, 8)

The Pelobatidae , as defined by Roček et al. (2014), include only one extant genus ( Pelobates WAGLER, 1830 ) and the extinct Eopelobates PARKER, 1929 . Extant pelobatids inhabit Europe, western Asia and northwesternmost Africa. The earliest known pelobatids were recovered from the earliest Eocene (MP 7) of Europe ( Rage and Roček 2003, Rage 2012). Older pelobatids were reported, but they are better referred to as pelobatids s.l., an assemblage that encompasses the Asian Megophryidae BONAPARTE, 1850 and North American Scaphiopodidae COPE, 1865 in addition to Pelobatidae s.s.; these three groups were formerly regarded as subfamilies of the Pelobatidae . Pelobatids from the early Eocene of Europe remain unidentified below family level. Although Eopelobates sp. was reported from the early Eocene (Ypresian) of Europe ( Sanchiz 1998) and Asia ( Folie et al. 2013), the earliest confirmed representatives of the genus are E. wagneri ( WEITZEL, 1938) from the early middle Eocene (MP 11) of Messel, Germany (Wuttke 2012), and the approximately coeval E. deani ROČEK, WUTTKE, GARDNER et BHULLAR, 2014 from Wyoming, the USA ( Roček et al. 2014). According to Duffaud (2000) and Roček et al. (2014), the earliest representatives of Pelobates are disarticulated remains from the early Oligocene (MP 22) of Mas-de-Got, a locality of the Phosphorites.

Pelobatidae were first reported from the Phosphorites by Hoffstetter (1945), but this identification was erroneous (see below ‘ Thaumastosaurus ’). However, the presence of pelobatids in the Phosphorites subsequently was confirmed (e.g., de Bonis et al. 1973, Crochet et al. 1981, Duffaud 2000, Rage 2006), but identification of these fossils below family level is difficult.

The distinction between Pelobates and Eopelobates is not easy. It is mainly based on skull bones ( Roček et al. 2014) and most of the specimens from the Phosphorites do not appear to be adequate for distinguishing between these two genera. Isolated bones from the Phosphorites are generally post-cranial elements, whereas the available skull bones are often incomplete and may be confused with those of the ranoid Thaumastosaurus DE STEFANO, 1903 , which bears a pelobatid-like ornamentation. The pelobatid material from the Phosphorites needs to be revised. The most frequent bones are ilia and vertebrae. Within pelobatids, the morphology of the ilia is quite homogenous ( Text-fig. 2 : 7) and it does not permit easy identification. Posterior presacral vertebrae might be useful because spinal foramina are sometimes present ( Rage and Augé 2015, Blain et al. 2016), which is an exceedingly rare character in anurans; however, the taxonomic significance of this feature, if any, remains unknown. Sacral vertebrae are generally found to be a useful tool for identification, but they are rare in localities and usually poorly preserved ( Text-fig. 2 : 8).

Duffaud (2000) mentioned Eopelobates aff. bayeri from the late Eocene (MP 19) and the earliest Oligocene (MP 21) of the Phosphorites. Rage (2006) reported those fossils as Eopelobates aff. anthracinus because Sanchiz (1998) regarded E. bayeri ŠPINAR, 1952 as a junior synonym of E. anthracinus PARKER, 1929 ; however, this synonymy was not recognized by Roček et al. (2014). However, the available material does not permit such precise identification. At present, it is only possible to state that Pelobatidae are present in the Phosphorites from MP 16, late middle Eocene ( Rage 1988) to MP 23, early/ middle Oligocene ( Duffaud 2000). In younger levels of the Phosphorites, anurans become rare and, despite the report of a pelobatid as cf. Pelobates from the late Oligocene (MP 28) ( Crochet 1972), the presence of representatives of the family after MP 23 has not been confirmed.

Figures

Text-fig. 2. Alytidae and Pelobatidae from the Phosphorites du Quercy. 1: Alytid indeterminate, urostyle UM-ROS1-601, from the late Eocene of Rosières 1 (MP 19), in anterior (a) and dorsal (b) views. 2: Alytid indeterminate, urostyle UM-ABL1-1901, from the earliest Oligocene of Aubrelong 1 (MP 21), in anterior (a), dorsal (b), and left lateral (c) views. 3: Alytid indeterminate, urostyle UM-BEL 1513, from the middle Oligocene of Belgarric (MP 25), in anterior (a), dorsal (b), and left lateral (c) views. 4: Alytid indeterminate, left ilium UM-GAO3-01, from the early/middle Oligocene of Gardiol 3 (MP 23), in lateral view. 5: Alytid indeterminate, presacral vertebra UM-BEL 1512, from the middle Oligocene of Belgarric (MP 25), in anterior (a), ventral (b), and dorsal (c) views. 6: Alytid indeterminate, left humerus UM-BEL 1514, from the middle Oligocene of Belgarric (MP 25), in ventral view. 7: Pelobatid indeterminate, right ilium UM-RAV 3500, from the earliest Oligocene of Ravet (MP 21), in lateral view. 8: Pelobatid indeterminate, sacral vertebra UM-ECC 2547, from the late Eocene of Escamps (MP 19), in dorsal (a), ventral (b), and posterior (c) views. Each scale bar = 3 mm.