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Babiacetus

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Babiacetus
Temporal range: Middle Eocene, 48.6–40.4 Ma
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: †Protocetidae
Subfamily: †Georgiacetinae
Genus: †Babiacetus
Trivedy & Satsangi 1984
Species

Babiacetus is an extinct genus of early cetacean that lived during the late Lutetian middle Eocene of India (48.6 to 40.4 million years ago).[1][2] It was named after its type locality, the Harudi Formation[3] in the Babia Hills (23°30′N 68°48′E / 23.5°N 68.8°E / 23.5; 68.8: paleocoordinates 5°54′N 61°48′E / 5.9°N 61.8°E / 5.9; 61.8), Kutch District, Gujarat, India.[2]

Babiacetus was named by Trivedy & Satsangi 1984 in an abstract based on the specimen's type (GSI 19647, left and right dentaries with cheek teeth).[4] Gingerich and colleagues found a skull (GSP-UM 3005, much of a skull and lower jaws)[4] while collecting a skeleton of a new species of Protosiren (Protosiren sattaensis)[5] in the Drazinda Formation (30°48′N 70°30′E / 30.8°N 70.5°E / 30.8; 70.5, paleocoordinates 16°54′N 67°06′E / 16.9°N 67.1°E / 16.9; 67.1)[6] in the Sulaiman Range of Punjab, Pakistan. Gingerich et al. 1995 described both the original find and their new specimen.[7] Bajpai & Thewissen 1998 described B. mishrai from the specimen (RUSB 2512, a partial skull)[4] collected in the Harudi Formation.[7][8]

Babiacetus is one of the larger protocetids.[9] Its hydrodynamic skull and pointed, anteroposteriorly (front-back) oriented incisors are typical of archaeocetes. A densely ossified auditory bulla and large mandibular canal indicate it was adapted for hearing in water.[10] Babiacetus differs from pakicetids and ambulocetids (more primitive families) by the large mandibular foramen and a medially concave ascending ramus; distinct from remingtonocetids and basilosauroids (more derived families) by the single-cusped trigonid and talonid on the lower molars.[7] Its long synostotic (fused) mandibular symphysis, which reaches as far back as P2, distinguishes it from Pappocetus and Georgiacetus (other protocetids). Its auditory bulla is more narrow than Rodhocetus'. Babiacetus lacks the prominent molar protocone present in Indocetus.[11] The anterior premolars are large.[9]

Its large size as well as robust teeth suggest that it fed on larger fishes or aquatic vertebrates, or both. To date, only cranial remains have been found, hence nothing is known of Babicetus' mode of locomotion or degree of aquatic adaptation.[10]

The mandible is longer in B. indicus than in B. mishrai, and P1 is single-rooted in the former but double-rooted in the latter. The diastemata between P1 and P4 in B. indicus is absent in B. mishrai. B. indicus has larger cheek teeth and a larger M3.[11]

Notes

  1. ^ Babiacetus in the Paleobiology Database. Retrieved March 2013.
  2. ^ a b Babia Hills in the Paleobiology Database. Retrieved April 2013.
  3. ^ Harudi in the Paleobiology Database. Retrieved April 2013.
  4. ^ a b c "Babiacetus". Palaeocritti. Retrieved 27 March 2013.
  5. ^ Gingerich et al. 1995, Introduction, p. 332
  6. ^ Bari Nadi 2 in the Paleobiology Database. Retrieved April 2013.
  7. ^ a b c Bajpai & Thewissen 1998, pp. 226–8
  8. ^ Babiacetus mishrai in the Paleobiology Database. Retrieved March 2013.
  9. ^ a b Gingerich et al. 1995, pp. 348–53
  10. ^ a b Gingerich et al. 1995, pp. 354–5
  11. ^ a b Williams 1998, pp. 12–13

References

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