Jainosaurus

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Jainosaurus
Temporal range: Late Cretaceous, 68 Ma
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Dinosauria
Order: Saurischia
Suborder: Sauropodomorpha
Clade: Neosauropoda
Clade: Macronaria
Clade: Titanosauria
Genus: Jainosaurus
Hunt et al., 1995
Type species
Antarctosaurus septentrionalis
von Huene & Matley, 1933
Species

Jainosaurus is a large titanosaurian dinosaur of India and wider Asia, which lived in the Maastrichtian (approximately 68 million years ago). A herbivorous quadruped, an adult Jainosaurus would have measured around eighteen metres long and held its head six metres high. No accurate estimate of the weight has yet been made. The humerus of the type specimen is 134 centimetres long.

Etymology[edit]

The specific name of J. septentrionalis means "northern" in Latin, a reference to the fact that the species was discovered on the Northern hemisphere whereas Antarctosaurus means "saurian from the Southern hemisphere" because its type species Antarctosaurus wichmannianus was found in Argentina.The generic name honours the Indian paleontologist Sohan Lal Jain,[1] who worked on the cranial nerve impressions in the skull;[2] and in 1982 published a study about the results.[3] Ironically, Jain himself considered the remains synonymous with Titanosaurus in the 1997 description of Isisaurus.[4] However, Wilson and Upchurch (2003) rejected the synonymy of Jainosaurus and Titanosaurus due to the dubious status of the latter.[5]

History[edit]

The type species of Jainosaurus, J. septentrionalis has a long and complex taxonomic history closely connected to the history of the problematic genera Titanosaurus and Antarctosaurus. The first remains were between 1917 and 1920 found by Charles Alfred Matley near Jabalpur in the Lameta Formation. These were named Antarctosaurus septentrionalis by Friedrich von Huene and Matley in 1933.[6]

In 1995 Adrian Paul Hunt et al., believing Antarctosaurus to belong to Dicraeosauridae, made the clearly titanosaurian Antarctosaurus septentrionalis the type species of a new genus, Jainosaurus, and determined that the braincase, GSI IM K27/497, should be the lectotype.[7] Jainosaurus was further distinguished from Antarctosaurus by details of the braincase.

In 2009, Jeffrey Wilson and others made a detailed reassessment of Jainosaurus septentrionalis and confirmed its validity. The postcrania, which had been assumed lost, were shown to be largely present in the collection of the Geological Survey of India at Calcutta. They include: dorsal rib fragments (GSI K20/326, K27/425); a caudal vertebra (GSI K20/317), four chevrons (GSI K27/492–494, 496), the left and right scapula (only a cast still extant); a sternal plate (GSI K20/647); a humerus (lacking an inventory number), a radius (GSI K27/490) and an ulna (GSI K27/491). In 1996 Sankar Chatterjee referred a second braincase to the species: ISI R162. Some material from Pakistan also possibly belongs to Jainosaurus.

Wilson e.a. concluded that Jainosaurus is a valid taxon, clearly distinguishable from Isisaurus. It would have been a fairly derived member of the Titanosauria, more closely related to South-American forms like Pitekunsaurus, Muyelensaurus and Antarctosaurus than to Isisaurus or Rapetosaurus.[8]

References[edit]

  1. ^ http://web.archive.org/web/20101225025430/http://dinosauria.com/dml/names/dinoj.htm
  2. ^ Sahni, Ashok (2001). Dinosaurs of India. National Book Trust, New Delhi. ISBN 81-237-3109-4. 
  3. ^ Berman, D. S. and S. L. Jain, 1982, "The braincase of a small sauropod dinosaur (Reptilia: Saurischia) from the Upper Cretaceous Lameta Group, Central India, with review of Lameta Group localities", Annals of the Carnegie Museum 51: 405–422
  4. ^ Jain, Sohan L.; Bandyopadhyay, Saswati (1997). "New Titanosaurid (Dinosauria: Sauropoda) from the Late Cretaceous of Central India". Journal of Vertebrate Paleontology. Norman, Okla.: University of Oklahoma. 17 (1): 114. doi:10.1080/02724634.1997.10010958.
  5. ^ Wilson, Jeffrey A.; Upchurch, P. (2003). "A revision of Titanosaurus Lydekker (Dinosauria – Sauropoda), the first dinosaur genus with a 'Gondwanan' distribution" (PDF). Journal of Systematic Palaeontology. Cambridge, U.K.: Cambridge University Press. 1 (3): 125–160. doi:10.1017/s1477201903001044. Retrieved December 31, 2012.
  6. ^ F. v. Huene and C. A. Matley, 1933, "The Cretaceous Saurischia and Ornithischia of the Central Provinces of India", Palaeontologica Indica (New Series), Memoirs of the Geological Survey of India, 21(1): 1-74
  7. ^ Hunt, A.P., Lockley M., Lucas S. & Meyer C., 1995, "The global sauropod fossil record", In: M.G. Lockley, V.F. dos Santos, C.A. Meyer, and A.P. Hunt, (eds.) Aspects of sauropod paleobiology, GAIA 10: 261-279
  8. ^ Wilson, Jeffrey; D'Emic, Michael; Rogers, Christina A. Curry; Mohabey, Dhananjay M.; Sen, Subashis, 2009, "Reassessment of Sauropod Dinosaur Jainosaurus (="Antarctosaurus") septentrionalis from the Upper Cretaceous of India", Contributions from the Museum of Paleontology, University of Michigan, 32(2): 17-40