The Cambay Shale formation from the Vastan Lignite Mine to the northeast of Surat in Gujarat State, India, has produced a diverse and significant Vertebrate fauna, including a diverse assemblage of Bats, the oldest known Ailuravine Rodents in Asia, the oldest known Lagomorphs (Rabbits), the oldest known Tillodont from India, early Adapoid and Omomyid Primates and Artiodactyls (the group that includes Antelopes, Cattle, Deer, Giraffes ect.), as well as Fish, Snakes, Lizards and Birds. A variety of Anuran species (Frogs and Toads) also appear to be present, although these are represented by a large volume of disarticulated bones, and have not therefore been studied in detail to date.
In a paper published in the journal Acta Palaeontologica Polonica on 27 January 2012, a team of scientists led by Annelise Folie of the Department of Paleontology at the Royal Belgian Institute of Natural Sciences, describe these Anuran bones in some detail, and conclude that at least four species from different Anuran families are present.
The majority of the bones are thought to come from a single species within the Fire-bellied Toad family Bombinatoridae. Modern members of this family are aquatic toads with flattened bodies; all extant species being highly toxic, and have colouration that reflects this. Fire-bellied Toads are noted for the ‘Unken reflex’ in which the animal responds to danger by arching its back strongly, exposing its brightly coloured underside as a warning of its toxic nature. Living members of this family are divided into two genera; Bombina, which is found in Europe and East Asia, and Barbourula, which is found in Borneo and the Philippines. The oldest known fossil assigned to this group has previously been a member the genus Bombina from the Miocene of Germany.
Folie et al. assign these bones to the species Eobarbourula delfinoi, where ‘Eobarbourula’ means ‘dawn-Barbourula’ and ‘delfinoi’ honours the Italian paleontologist Massimo Delfino. A total of 58 illia, 120 vertebrae and 12 urostyles are assigned to this species. The vertebrae assigned to Eobarbourula delfinoi have a zygosphene−zygantrum complex on their articulations, in which an anterior process on the vertebra, the zygosphene, inserts into a wedge-shaped cavity on the vertebra in front, the zygantrum. This is found in modern members of the family, as well as in the Salamander Salamandrina, and in Lacertid, Teiid, and Cordylid Lizards, and is associated with the Unken reflex. Similar structures have been seen in some Dinosaur species, and on the cervical (neck) vertebrae of some early Birds, suggesting that these too may have exhibited this behaviour.
Nearly complete ilium of Toad Eobarbourula delfinoi from the Early Eocene of the Vastan Lignite Mine in Gujarat, India. (A) Left ilium in lateral (A1), posterior (A2), medial (A3), and dorsal (A4) views. (B) Left ilium in lateral (B1), posterior (B2), medial (B3), and dorsal (B4) views. (C) Right ilium in medial (C1), posterior (C2), lateral (C3), and dorsal (C4) views. Folie et al. (2012).
Vertebrae of Toad Eobarbourula delfinoi from the Early Eocene of the Vastan Lignite Mine in Gujarat, India. (A) Atlas in anterior (A1), posterior (A2), left lateral (A3), dorsal (A4), and ventral (A5) views. (B). Anterior trunk vertebra in anterior (B1), posterior (B2), left lateral (B3), dorsal (B4), and ventral (B5) views. (C) Trunk vertebra in anterior (C1), posterior (C2), left lateral (C3), dorsal (C4), and ventral (C5) views. (D) Trunk vertebra in anterior (D1), posterior (D2), right lateral (D3), dorsal (D4), and ventral (D5) views. (E) Presacral vertebra in anterior (E1), posterior (E2), right lateral (E3), dorsal (E4), and ventral (E5) views. (F) Sacral vertebra in anterior (F1), posterior (F2), left lateral (F3), dorsal (F4), and ventral (F5) views. (G) Urostyle in anterior (G1), left lateral (G2), dorsal (G3), and ventral (G4) views. Folie et al. (2012).
Close up views of vertebrae of Toad Eobarbourula delfinoi from the Early Eocene of the Vastan Lignite Mine in Gujarat, India. (A) Presacral vertebra in dorsal (A1) and anterior (A2) views. (B) Trunk vertebra in posterior view. Folie et al. (2012).
Secondly a single ilium is thought to come from a member of the Spadefoot Toad family, Pelobatidae. This family only contains a single extant genus, Pelobates, a burrowing Toad known from Europe and West Asia, but has a fossil record going back to the Late Cretaceous (several earlier specimens have been reported, but are now considered dubious). This ilium is assigned to the genus Eopelobates, which has previously been used to describe specimens from the Middle Eocene-Miocene of Germany and the Czech Rebublic, but is not assigned to species level. Eopelobates lacks the adaptations for burrowing seen in the modern Pelobates, and was probably a terrestrial (ground dwelling) Toad, though it has been suggested that it might have lived in trees.
Pelvic girdle of frog Eopelobates. (A) Eopelobates wagneri from the Middle Eocene Messel Shale of Germany. (A1) Complete skeleton in dorsal view; (A2) pelvic girdle in mediodorsal view showing anatomical characters of ilia. (B) Eopelobates sp. from the Early Eocene of the Vastan Lignite Mine in Gujarat, India. Nearly complete right ilium in posterior (B1), lateral (B2), dorsal (B3), and medial (B4) views. Folie et al. (2012).
Thirdly a nearly complete ilia, seven vertebrae and two urostyles are assigned to the True Frog family Ranidae. This family is currently found across much of the globe, with its earliest described fossils coming from the Late Eocene of England and France, and possible specimens reported but never properly described from the Late Cretaceous of Africa and India. It has previously been suggested that this group may have reached Eurasia via the Indian Subcontinent, and the assignment of fossils from Vastan to this group supports this hypothesis.
Nearly complete right ilium of a Frog assigned to the Ranidae from the Early Eocene of the Vastan Lignite Mine in Gujarat, India, in lateral (A), posterior (B), medial (C), and dorsal (D) views. Folie et al. (2012).
Vertebrae of Frog assigned to the Ranidae, from the Early Eocene of the Vastan Lignite Mine in Gujarat, India. (A) Presacral vertebra in anterior (A1), posterior (A2), left lateral (A3), dorsal (A4), and ventral (A5) views. (B) Last presacral vertebra in anterior (B1), posterior (B2), left lateral (B3), dorsal (B4), and ventral (B5) views. (C) Sacral vertebra in anterior (C1), posterior (C2), left lateral (C3), dorsal (C4), and ventral (C5) views. (D) Fragmentary urostyle in anterior (D1), left lateral (D2), dorsal (D3), and ventral (D4) views. Folie et al. (2012).
Finally an incomplete left ilium and associated pubis, left ischium and half a right ischium are tentatively assigned to the family Rhacophoridae, Shrub Frogs or Old World Tree Frogs. These are currently distributed across tropical parts of Africa, India and Australasia, but have a limited fossil record. Specimens have been reported from the Late Eocene of France, but these have not been described and the presence of such Frogs in the Eocene of Europe is considered doubtful. The only other recorded fossils in this group are from the Pleistocene of Japan, so if the Vastan fossils are Rhacophorids, then they represent the earliest record of this group. These specimens are assigned to a new species, Indorana prasadi, where ‘Indorana’ means ‘Indian Frog’ and ‘prasadi’ honours the Indian palaeontologist Guntupalli Prasad, an expert on Indian Frogs.
Pelvic girdle of Frog Indorana prasadi, from the Early Eocene of the Vastan Lignite Mine in Gujarat, India. (A) Nearly complete left ilium with the two ischia and pubis in lateral (A1), posterior (A2), medial (A3), and dorsal (A4) views. (B) Incomplete left ilium with left ischium in lateral (B1), posterior (B2), medial (B3), and dorsal views (B4). Folie et al. (2012).
See also…
Bush Frogs (Rhacophoridae) are found throughout tropical areas of Africa and Asia. They are tree-dwelling frogs that seldom venture down to the ground, their eggs being laid in a foamy construct...
Flying Frogs of the genus Racophorus are found from Madagascar and Africa across India to Southeast Asia and Japan. They have...
The earliest known Frogs in the fossil record hail from the earliest Triassic of Madagascar, though it is thought the group probably has its origins deeper in the Permian. A number of Frogs have been described from the Early Cretaceous Jehol Biota, a fossil Lagarstätte (rich fossil deposit) from...
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