Yadagiri & Ayyasami, 1989
Bruhathkayosaurus (//; meaning "huge bodied lizard") is a dinosaur, with remains found in India, claimed by some researchers to have been the largest dinosaur that ever lived. Estimates of size exceed the titanosaur Argentinosaurus, as longer than 35 metres (115 ft) and weighing over 80-200 tons. 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 (see below: Size estimates).
Bruhathkayosaurus was found near the southern tip of India, specifically in the Tiruchirappalli 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. The name chosen, Bruhathkayosaurus, is derived from Sanskrit word Bruhathkaya (bṛhat बृहत्, 'huge, heavy' and kāya, काय 'body'), plus the Greek sauros (lizard).
The type species, Bruhathkayosaurus matleyi, is based on 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 uncertain position (incertae sedis). However, Chatterjee (1995) re-examined the remains and demonstrated that Bruhathkayosaurus is actually a titanosaur sauropod.
Until the remains are properly described, the validity of the genus and any size estimates will be questionable. It is possible that the only known remains of Bruhathkayosaurus have been lost to monsoon flooding. Thus the only remaining evidence is likely the very simple and indistinct line-drawings of the bones. However, 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.
According to the published description, the shin bone (tibia) of Bruhathkayosaurus is 2 m (6.6 ft) long. This is 29 percent larger than the tibia of Argentinosaurus, which is only 1.55 m (5.1 ft) long. The fragmentary femur is similarly huge, across the distal end, it measures 75 cm (2.46 ft), 33% larger than the femur of Antarctosaurus giganteus, which measures 56 cm (1.84 ft).
No total body size estimates for Bruhathkayosaurus have been published, but paleontologists and researchers have posted tentative estimates on the Internet. In a blog post from June 2001, Mickey Mortimer estimated that Bruhathkayosaurus could have reached 40–44 m (131–144 ft) in length and might have weighed 175–220 tons, but in later blog posts retracted these estimates, reducing the estimated length of Bruhathkayosaurus to 28–34 m (92–112 ft), and declined to provide a new weight estimate, describing the older weight estimates as inaccurate. 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 126 metric tons.
By comparison, the titanosaur Argentinosaurus is estimated to have reached 35 m (115 ft) in length, and to have weighed 80–100 tons. Another huge titanosaurid, Paralititan, was probably 32 m (105 ft) long, and weighed 59–80 tons. 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 size estimates for Bruhathkayosaurus are accurate it would be similar in size to the Blue Whale. Mature Blue Whales can reach 30 m (98 ft) in length, which is a little shorter than Bruhathkayosaurus, but the record-holder Blue Whale weighed in at 177 tons, which is probably heavier than Bruhathkayosaurus.
Another poorly known sauropod apparently approaches Bruhathkayosaurus in size. Maraapunisaurus fragillimus, based on a now-missing dorsal vertebra, was estimated by Carpenter (2006) to be 58 m (190 ft) in length and weigh only about 122.4 tons. However, Carpenter (2018) estimated Maraapunisaurus to be 30–32 m (98–105 ft) in length upon comparisons with known rebbachisaurids.
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- 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.
- Schneiderman, P. (Nov 1994). "Report on the initial description". Dinosaur Mailing List
- Chatterjee, S. (1995). “The last dinosaurs of India”. The Dinosaur Report, Fall 1995. p. 12-18.
- UPCHURCH, P., BARRETT, P. M. and DODSON, P. 2004. Sauropoda. pp. 259–322. In WEISHAMPEL, D. B., DODSON, P. and OSMÓLSKA, H. (eds). The Dinosauria, Second Edition. University of California Press, Berkeley, 861 pp.
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- Mortimer, M. (2001), "Re: Bruhathkayosaurus", discussion group, The Dinosaur Mailing List, 19 June 2001. Accessed 23 May 2008.
- Mortimer, M. (2004), "Re: Largest Dinosaurs", discussion group, The Dinosaur Mailing List, 7 September 2004. Accessed 23 May 2008.
- Mortimer, M. (2001), "Titanosaurs too large?", discussion group, The Dinosaur Mailing List, 12 September 2001. Accessed 23 May 2008.
- Wedel, M. "SV-POW! showdown: sauropods vs whales." [Weblog entry.] Sauropod Vertebra Picture of the Week. 20 May 2008. Accessed 23 May 2008.
- Paul, Gregory S. (1997). "Dinosaur models: the good, the bad, and using them to estimate the mass of dinosaurs". In Wolberg, D. L.; Stump, E.; Rosenberg, G. D. DinoFest International Proceedings. The Academy of Natural Sciences. pp. 129&ndash, 154.
- Smith, J.B.; Lamanna, M.C.; Lacovara, K.J.; Dodson, P.; Smith, J.R.; Poole, J.C.; Giegengack, R.; 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. PMID 11387472.
- J. Calambokidis & G. Steiger (1998). Blue Whales. Voyageur Press. ISBN 0-89658-338-4.
- "What is the biggest animal ever to exist on Earth?". How Stuff Works. Retrieved 2007-05-29.
- 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.
- Carpenter, Kenneth (2018). "Maraapunisaurus fragillimus, N.G. (formerly Amphicoelias fragillimus), a basal Rebbachisaurid from the Morrison Formation (Upper Jurassic) of Colorado". Geology of the Intermountain West. 5: 227–244.
- Report on the initial description from the Dinosaur Mailing List.