Bruhathkayosaurus

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Bruhathkayosaurus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Superorder: Dinosauria
Order: Saurischia
Suborder: Sauropoda
(unranked) Titanosauria?
Genus: Bruhathkayosaurus
Yadagiri & Ayyasami, 1989
Species
  • B. matleyi Yadagiri & Ayyasami, 1989 (type)

Bruhathkayosaurus (pronounced /bruːˌhæθkeɪoʊˈsɔrəs/, meaning 'huge bodied lizard') might have been the largest dinosaur that ever lived. The accuracy of this claim, however, has been mired in controversy and debate. All the estimates are based on Yadagiri and Ayyasami's 1989 paper, which announced the find.[1]

The authors originally classified the dinosaur as a theropod, a member of a large group of bipedal, carnivorous dinosaurs that includes Tyrannosaurus, but several unpublished opinions beginning in 1995 suggested that the remains actually belonged to a sauropod (probably a titanosaur), a member of a very different group of quadrupedal, herbivorous dinosaurs with long necks and tails similar to Brachiosaurus. In 2006, the first published reference to Bruhathkayosaurus as a sauropod appeared in a survey of Malagasy vertebrates by David Krause and colleagues.[2]

Until the remains are properly described, the validity of any estimates will be questionable.

Contents

[edit] Discovery

Bruhathkayosaurus was found near the southern tip of India, specifically in the Tiruchirapalli district of Tamil Nadu, to the northeast of Kallamedu village. It was recovered from the rocks of the Kallemedu Formation, which are dated to the Maastrichtian faunal stage of the late Cretaceous period. It lived toward the end of Mesozoic era, about 70 million years ago. The fossilized remains include hip bones (the ilium and ischium), part of a leg bone (femur), a shin bone (tibia), a forearm (radius) and a tail bone (part of a vertebra, specifically a platycoelous caudal centrum). The remains were originally classified as belonging to a carnosaur.[1] The name chosen, Bruhathkayosaurus, is derived from bruhath (misspelled Sanskrit brhat (बृहत), huge, or heavy), and kāya (काय) (body); and the Greek sauros (lizard).

[edit] Classification

The Bruhathkayosaurus genus has only one known species, Bruhathkayosaurus matleyi. The species is represented by the holotype specimen GSI PAL/SR/20, which was described by Yadagiri and Ayyasami in 1989 (not 1987, as some sources indicate). It was originally classified as a carnosaur (like Allosaurus), of an unknown (incertae sedis) family. It was later recognized as a sauropod.

The original publication described little in the way of diagnostic characteristics and was only supported by a few line drawings. This has led to speculation that the bones might actually be petrified wood, akin to the way the original discoverers of Sauroposeidon initially believed their find to be fossilized tree trunks.

[edit] Size estimates

According to the published description, the shin bone (tibia) of Bruhathkayosaurus is 2 m (6 ft, 7 in) long. This is 29 percent larger than the tibia of Argentinosaurus, which is only 1.55 m (5 ft, 1 in) long. Comparing the bones in the upper forelimb gives a similar result. While the humerus of Bruhathkayosaurus is incomplete, it is extrapolated to have been 2.34 m (7 ft, 8 in) long. This is 30 percent larger than the humerus of Argentinosaurus, which is 1.81 m (5 ft, 11 in) long.

No total body size estimates for Bruhathkayosaurus have been published, but paleontologists and researchers have posted tentative estimates on the Internet. One early estimate by Mickey Mortimer estimated that Bruhathkayosaurus could have reached 40 m (130 ft) to 44.1 m (145 ft) in length and to have weighed from 175 to 220 t (190 to 240 tons).[3] However, Mortimer later retracted these estimates, reducing his estimated length of Bruhathkayosaurus to 28 - 34 m (90 - 110 ft), and declined to provide a new weight estimate, describing the older mass estimates as inaccurate.[4][5] In a May 2008 article for the Weblog Sauropod Vertebra Picture of the Week, paleontologist Matt Wedel used a comparison with Argentinosaurus and calculated the weight of Bruhathkayosaurus at up to 139 t.[6]

By comparison, the titanosaur Argentinosaurus is estimated to have reached 34.6 m (114 ft) in length, and to have weighed from 80 to 100 t (90 to 110 tons). Another huge titanosaurid, Paralititan, was probably 31.9 m (105 ft) long, and weighed 65 to 80 t (72 to 88 tons).[7] All of these sauropods are known only from partial or fragmentary remains, so the size estimates are uncertain. Length is calculated by comparing existing bones to the bones of similar dinosaurs, which are known from more complete skeletons and scaling them up isometrically. However, such extrapolation can never be more than an educated guess and the length of the tail, in particular, is often hard to judge. Determining mass is even more difficult, because little evidence of soft tissues survives in the fossil record. In addition, isometric scaling is based on the assumption that body proportions remain the same, which is not necessarily the case. In particular, the proportions of the titanosaurs are not well known, due to a limited number of relatively complete specimens.

If the large size estimates for Bruhathkayosaurus are accurate, the only real competition would be the blue whale. The largest on record reached an estimated 33.5 m (110 ft) in length, which is shorter than Bruhathkayosaurus; but was equally massive, weighing in at 177 t (195 tons).

Among the dinosaurs, other poorly known specimens may approach or exceed Bruhathkayosaurus in size. Edward Drinker Cope's Amphicoelias fragillimus would have been longer, reaching 56 to 62 m (185 to 200 ft) in length, but it was a slender diplodocid, weighing only 120 t (135 tons). Unfortunately, the only bone recovered (a massive vertebra) is now missing, and only a description and drawing of the specimen remain.[8]

[edit] References

  1. ^ a b Yadagiri, P. and Ayyasami, K. (1989). "A carnosaurian dinosaur from the Kallamedu Formation (Maestrichtian horizon), Tamilnadu." In M.V.A. Sastry, V.V. Sastry, C.G.K. Ramanujam, H.M. Kapoor, B.R. Jagannatha Rao, P.P. Satsangi, and U.B. Mathur (eds.), Symposium on Three Decades of Development in Palaeontology and Stratigraphy in India. Volume 1. Precambrian to Mesozoic. Geological Society of India Special Publication, 11(1): 523-528.
  2. ^ Krause, D.W., O'Connor, P.M., Curry Rogers, K., Sampson, S.D., Buckley, G.A., and Rogers, R.R. (2006). "Late Cretaceous terrestrial vertebrates from Madagascar: Implications for Latin American biogeography." Annals of the Missouri Botanical Garden, 93(2): 178-208.
  3. ^ Mortimer, M. (2001), "Re: Bruhathkayosaurus", discussion group, The Dinosaur Mailing List, 19 June 2001. http://dml.cmnh.org/. Accessed 23 May 2008.
  4. ^ Mortimer, M. (2001), "Titanosaurs too large?", discussion group, The Dinosaur Mailing List, 12 September 2001. http://dml.cmnh.org/. Accessed 23 May 2008.
  5. ^ Mortimer, M. (2004), "Re: Largest Dinosaurs", discussion group, The Dinosaur Mailing List, 7 September 2004. http://dml.cmnh.org/. Accessed 23 May 2008.
  6. ^ Wedel, M. "SV-POW! showdown: sauropods vs whales." [Weblog entry.] Sauropod Vertebra Picture of the Week. 20 May 2008. (http://svpow.wordpress.com/2008/05/20/sv-pow-showdown-sauropods-vs-whales/), accessed 23 May 2008.
  7. ^ Smith, J.B.; Lamanna, M.C.; Lacovara, K.J.; Dodson, P.; Smith, J.R.; Poole, J.C.; Giegengack, R.; and Attia, Y. (2001). "A giant sauropod dinosaur from an Upper Cretaceous mangrove deposit in Egypt". Science 292 (5522): 1704–1706. doi:10.1126/science.1060561. 
  8. ^ Carpenter, K. (2006). "Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus." In Foster, J.R. and Lucas, S.G., eds., 2006, Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin 36: 131-138.[1]

[edit] External links

Dinosaurs Portal