In the late 1980s fragmentary postcranial remains from the Kallamedu Formation in Tamil Nadu, southern India, were described by Indian paleontologists P. Yadagiri and Krishnan Ayyasami as a new genus and species of carnosaurian theropod, Bruhathkayosaurus matleyi, in a paper published in 1987. However, in the 1990s the theropod placement of Bruhathkayosaurus was disputed and this taxon was soon recognized as being a titanosaurian sauropod. Due to the paucity of line drawings and photographs of the Bruhathkayosaurus material as it lay on the ground, there was online speculation that this taxon was based on fossilized tree trunks rather than genuine dinosaur bones, and varying size estimates for Bruhathkayosaurus based on the published description by Yadagiri and Ayyasami (1987) posted on internet forums precluded Bruhathkayosaurus from being touted in record books as the biggest dinosaur that ever lived. Nevertheless, various authors (e.g. Krause et al. 2006; Hone et al. 2016) have come to agree with Chatterjee (1995) that Bruhathkayosaurus matleyi is a sauropod, although the questionable validity of this taxon was further compounded by the type material falling victim to the effects of local monsoons (Galton and Ayyasami 2017). Thanks to additional published photographs of the B. matleyi type material and new morphological information on this poorly known dinosaur, it is apparent that the material of Bruhathkayosaurus is indeed from a giant titanosaur and that past hints about this dinosaur being based on non-vertebrate material do not hold water.
 |
| Photographs of the holotype ilium and paratype tibia of Bruhathkayosaurus matleyi (left) and line drawings of the B. matleyi ilium and tibia (right). From Yadagiri and Ayyasami (1987). |
When Bruhhathkyosaurus was first described by Yadagiri and Ayyasami (1987), it was considered by the authors to be a very large theropod possibly comparable to or exceeding Tyrannosaurus rex in size (radius and pubis of Bruhathkayosaurus matleyi were not described or illustrated). The first author to question the theropod classification of this taxon was Olshevsky (1994), who noted that the proportions of the ilium and tibia were unusually large for a huge theropod judging from the illustrations in Yadagiri and Ayyasami (1987), therefore suggesting that Bruhathkayosaurus might not be a theropod. In a 1994 post on Dinosaur Mailing list, John Schneiderman regarded the tibia of Bruhathkayosaurus as either a sauropod or petrified wood, while Thomas Holtz Jr. in a 1995 post on the DML suggested that the type material of B. matleyi could be fossilized tree trunks due to the poor quality of the line drawings of the ilium and tibia by Yadagiri and Ayyasami (1987) Chatterjee (1995) showed that B. matleyi represented a titanosaurian sauropod by noting that the high iliac crest of the holotype ilium (GSI PAL/SR/20) and proportions of the distal femur and tibia were consistent with that of titanosaurs. Upchurch et al. (2004) tabulated Bruhathkayosaurus matleyi as a nomen dubium without any further comment, most probably aware of Chatterjee's (1995) re-assessment of Bruhathkayosaurus because that paper is not included in the bibliography for the second edition of the book The Dinosauria. Krause et al. (2006) also classified Bruhathkayosaurus as a sauropod, and Hone et al. (2016) likewise agreed with Chatterjee's (1995) identification of Bruhathkayosaurus as a titanosaur. Pal and Ayyasami (2022) provide photographs of the tibia of Bruhathkayosaurus matleyi during excavation from the Cauvery Basin and after being wrapped in a plaster jacket, and they clinch the titanosaur identification of the tibia by noting that the cnemial crest of the tibia is identical to that of titanosaurs in being smaller and less prominent than in abelisaurids, while debunking online suggestions that the B. matleyi type material is merely fossilized wood.
Now all this brings me to discussions online and published scientific literature regarding the possible size of Bruhathkayosaurus. Mickey Mortimer wrote in a June 2001 post on the Dinosaur Mailing List that Bruhathkayosaurus most likely measured 145 feet (44.1 meters) based on measurements provided by Yadagiri and Ayyasami (1987), but in later posts on the DML he revised to size estimate for this taxon to 92-154 feet (28-47 meters). In a May 2008 post on his blog Sauropoda Vertebra of the Week, Mike Taylor suggested that Bruhathkayosaurus was 20 percent bigger than Argentinosaurus based on the length of the tibia. Although Pal and Ayyasami (2022) declined to provide a precise size estimate for B. matleyi given the limited material, they did confirm the gigantic nature of Bruhathkayosaurus by showing that its tibia was bigger than that of Argentinosaurus and Dreadnoughtus and that the width of the distal femur was bigger than that of Patagotitan. The authors also noted that the holotype ilium and paratype tibia are unlikely to belong the same individual due to size differences (the length of the ilium of B. matleyi is shorter than the ilium of the Dreadnoughtus schrani holotype), supporting Olshevshy's (1994) suggestion that the Bruhathkayosaurus material might be chimeric, but the ilium itself would still be comparable in size to those known for some large-sized titanosaurs, namely Futalognkosaurus, because its length is much greater than the longest ilia of any abelisaurid. Paul and Larramendi (2023) provide a narrower size estimate for Bruhathkayosaurus ranging from 115-148 feet (35-45 meters) with a mean length of 131 feet (40 meters). In my opinion, Bruhathkayosaurus is probably close to the lower end of the size range deduced by Paul and Larramendi (2023) for this taxon, at 120 feet (36 meters) in length, because Diplodocus hallorum and Maraapunisaurus were once considered to attain lengths of 170 feet (52 meters) and 190 feet (58 meters) respectively, only to have their size estimates reduced drastically to within 100-115 feet (30-35 meters) by later research. Regardless of the fact that the holotype ilium and paratype tibia of Bruhathkayosaurus matleyi do not appear to come from the same individual, the the tibia indicates that Bruhathkayosaurus is indeed a taxon of gigantic titanosaur as surmised online by Mickey Mortimer and Mike Taylor.
Although it is unfortunate that monsoons ended up causing the type material of Bruhathkayosaurus matleyi to disintegrate before being taken to its respective paleontological institution and there were rumors online that Bruhathkayosaurus was based on petrified wood rather than genuine dinosaur fossils even if it was clear by the mid-1990s that the original theropod classification of this taxon did not hold water, it is heartening to see that additional photographic evidence has vindicated the conclusion by Chatterjee (1995) that Bruhathkayosaurus itself is not just a titanosaur but also roughly comparable to Argentinosaurus and Diplodocus hallorum in size. Considering that Matley (1929) was the first author to report giant titanosaur remains from the Kallamedu Formation, Bruhathkayosaurus constitutes the second instance of a super-size titanosaur from this geologic unit, suggesting that giant titanosaurs had a widespread distribution across Gondwana by the Maastrichtian.
References:
Chatterjee, S., 1995. The
last dinosaurs of India. The Dinosaur Report (Fall 1995): 12-18.
Galton, P.M., and Ayyasami, K., 2017. Purported latest bone of a plated dinosaur (Ornithischia: Stegosauria), a "dermal plate" from the Maastrichtian (Upper Cretaceous) of southern India. Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 285 (1): 91–96. doi:10.1127/njgpa/2017/0671.
Hone, D.W. E., Farke, A.A.,
and Wedel, M.J., 2016. Ontogeny and the fossil
record: what, if anything, is an adult dinosaur? Biology Letters 12 (2): 20150947. doi:10.1098/rsbl.2015.0947.
Krause, D.W., O'Connor, P.M., Rogers, K.C., 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. doi:10.3417/0026-6493(2006)93[178:LCTVFM]2.0.CO;2.
Matley, C.A., 1929. The Cretaceous dinosaurs of the Trichinopoly District, and the rocks associated with them. Records of the Geological Survey of India 61: 337–349.
Olshevsky, G., 1994. Bruhathkayosaurus:
Bigger Than T. rex? The Dinosaur Report (Winter 1994): 12–13.
Pal, S., and Ayyasami, K., 2022. The lost titan of Cauvery. Geology Today 39: 112–116.
Paul, G.S., and Larramendi, A., 2023. Body mass estimate of Bruhathkayosaurus and other fragmentary sauropod remains
suggest the largest land animals were about as big as the greatest whales. Lethaia 56 (2): 1–11. doi:10.18261/let.56.2.5.
Upchurch, P., Barrett, P.M., and Dodson, P. 2004. Sauropoda. pp. 259-322. In: Weishampel, D.B., Dodson, P., and Osmólska, A.H. (eds). The Dinosauria, second edition. University of California Press: Berkeley, CA.
No comments:
Post a Comment