Rajasaurus

 Rajasaurus  (meaning "king" or "king of lizards") is a genus of carnivorous abelisaurian theropod dinosaur with an unusual head crest. Between 1982 and 1984, its fossilized bones were discovered by Suresh Srivastava of the Geological Survey of India (GSI). Excavated from the Narmada River valley in Rahioli in the Kheda district of Gujarat, India, the find was announced as a new genus of dinosaur by American and Indian scientists on August 13, 2003.[1]

Paleontologists Paul Sereno of the University of Chicago, Jeff Wilson of the University of Michigan, and Srivastava worked together as an Indo–American group to study the Narmada River fossils.[2] The fossils represented the partial skeleton of the new species Rajasaurus narmadensis, which means "princely lizard from the Narmada Valley."[3] The fossilized bones of Rajasaurus have also been found in the upriver region of the Narmada, at Jabalpur, in the state of Madhya Pradesh.

Description
Rajasaurus was an abelisaurid, a member of a group of theropod predators known to have lived only on landmasses that were part of the supercontinent Gondwana, such as Africa, India, Madagascar, and South America. Rajasaurus closely resembles Majungasaurus, a contemporary abelisaur from Madagascar, an island that had separated from the Indian landmass about 20 million years earlier.[4] It was found to be an abelisaurid through a phylogenetic analysis of anatomical characteristics, and was described as a carnotaurine abelisaurid (the subfamily including Carnotaurus) because of the configuration of its nasal bones and its possession of a growth ("excrescence") on its frontal bone. Rajasaurus is distinguished from other genera by its single nasal-frontal horn, the elongated proportions of its supratemporal fenestrae (holes in the upper rear of the skull), and the form of the ilia (principle bones of the hip) which feature a transverse ridge separating the brevis shelf from the hip joint.[3]

Rajasaurus was identified from a partial skeleton including a well–preserved skull (with a complete braincase and 70% of the rest of the skull bones recovered), hip bones and parts of the hind legs, backbone and tail. This specimen, GSI 21141/1–33, serves as the type specimen of the genus and species.[3] Rajasaurus measured about 7.6–9 m (24.9–29.5 ft) long, 2.4 m (7.9 ft) in height, and weighed about 3 to 4 tons. The skull was short, measuring 60 cm (23.6 in) in length, and bore a distinctive low rounded horn.[1][5] This horn is made up of outgrowths from the nasal and frontal bones.

History of discovery
The Narmada River in central India drains its valley from east to west, in a rift valley and eventually into the Arabian Sea after traveling 1,312 km (815.2 mi). Dinosaur bones have been reported from the Narmada valley since the late 19th century, including some belonging to Titanosaurus indicus.[6]

The history of the fossils named Rajasaurus begins in 1981. When G.N. Dwivedi and D.M. Mohabey, geologists of the Geological Survey of India, were on a mapping mission, the workers of the ACC Cement quarry at Rahioli, in Gujarat showed them smooth ball-like limestone structures from the quarry. These "balls" turned out to be dinosaurian eggs. The geologists also found that the limestone bed containing the fossilized eggs was underlain by a layer of coarse sandstone and conglomerate with abundant dinosaurian fossil bones.[2]

During the years 1982–84 Suresh Srivastava, a GSI geologist at the Palaeontology Division of the GSI's Western Region, collected large numbers of bone fossil fragments from Rahioli, and also precisely mapped the area. These fossils were taken to the Palaeontology Division at Jaipur for identification. U. B. Mathur and Suresh Srivastava, under the supervision of S. C. Pant, meticulously cleaned many of the skeletal parts (braincase, dorsal and caudal vertebrae, sacrum, thigh bone, upper arm, shin bones, and others), leading to the publication of multiple research papers.[7][8] There was a lull in further activity until a Memorandum of Understanding (MOU) was signed with the Punjab University in 1994–95.[2]

In 2001, further research on the fossils was continued by two American scientists sponsored by the American Institute of Indian Studies, New Delhi and the National Geographic Society, U.S.A.[2] The Americans, Paul Sereno and Jeff Wilson, started the reconstruction of the collection of dinosaur bones gathered in 1983 and 1984. The team of scientists, after a detailed study of the maps prepared earlier by Srivastava, were able to reconstruct the partial skull, left and right hip bones, and a sacrum. They interpreted the part of a skull and a horn as resembling those of dinosaurs found in Madagascar.[1] Fossils of Rajasaurus were also found near Jabalpur in Madhya Pradesh. In all, the collected fossils include a partial skull, limb bones, hip bones, and vertebrae.[5]

Although Rajasaurus was formally described in 2003, there are fossils described in 1923 that may belong to this genus. Charles Alfred Matley described Lametasaurus indicus in that year from specimens including an ilium, a sacrum, a shin bone, and armor scutes found at Bara Simla.[9] Lametasaurus was later shown to be a chimera, and Wilson et al. suggested that the ilium and sacrum (now lost) were exemplars of the similarly stout Rajasaurus.[3]

The discovery of Rajasaurus could lead to additional information on the evolutionary relationships of abelisaurs, since previously described specimens from India were mainly isolated bones.[1] At a press conference held in 2003 on the discovery of Rajasaurus, Sereno stated:

The discovery, which will be put for examination before global experts, was important since it would help in adding to the current knowledge of dinosaur belonging to the family of Abelisaur predators and adding a new angle to dinosaur in the Indian subcontinent.