Isisaurus

''Isisaurus'' (named after the Indian Statistical Institute) is a genus of titanosaurian dinosaur from the Late Cretaceous Lameta Formation of India. The genus contains a single species, ''Isisaurus colberti''.

Discovery and Naming

The type specimen of ''Isisaurus colberti'', ISI R 335/1-65, was originally described and named as '' Titanosaurus colberti'' by Sohan Lal Jain and Saswati Bandyopadhyay in 1997. The specific name honours Edwin Harris Colbert. In 2003, the fossils were designated as belonging to its own genus by Wilson and Upchurch. The generic name, "''Isisaurus''," combines a reference to the Indian Statistical Institute (ISI) with the Greek "saurus," meaning "lizard." It had a short, vertically directed neck and long forelimbs, making it considerably different from other sauropods. The humerus is 148 centimetres long.

''Isisaurus'' is known from better remains than many other titanosaurs that were known at the time of its description. Much of its postcranial skeleton is known. The skeletal material found by Jain and Bandyopadhyay between 1984 and 1986 was "in associated and mostly articulated condition." The holotype includes cervical, dorsal, sacral and caudal vertebrae, ribs, pelvis, scapula, coracoid, left forelimb and other bones. No skull, hindlimb, or foot bones are known. Since the original description of ''Isisaurus'', titanosaur fossils belonging to more complete individuals have been discovered.

The site locality is Dongargaon Hill, which is in a Maastrichtian crevasse splay claystone in the Lameta Formation of India. Dongargaon Hill (20.212318N,79.090709E) is located near Warora, in Chandrapur District, Maharashtra.

Description

Two types of sauropod skulls are known from the Maastrichtian of India. The first type is from the coeval '' Jainosaurus,'' and the other is from ''Isisaurus''. While ''Jainosaurus'' had a broad and flat cranium, the skull of ''Isisaurus'' was more robust and compact. Additionally, the angle between the occipital bone and occipital condyle is different in the two taxa. In the specimen from Dongargaon it is equal to 120°. In that matter, the cranium of ''Isisaurus'' resembles the skulls of '' Diplodocus'' and '' Apatosaurus'' (genera belonging to the Diplodocidae), but the bone modifications are different.

Palaeobiology

Fungus in coprolites believed to have been voided by ''Isisaurus'' indicate that it ate leaves from several species of tree, since these fungi are known to be pathogens which infect tree leaves.Sharma, N., Kar, R.K., Agarwal, A. and Kar, R. (2005). "Fungi in dinosaurian (''Isisaurus'') coprolites from the Lameta Formation (Maastrichtian) and its reflection on food habit and environment." ''Micropaleontology'', 51(1): 73-82.

Paleoecology

''Isisaurus'' lived in the area belonging nowadays to India during the Maastrichtian age of the Cretaceous period. Its remains are the most complete among the Cretaceous dinosaurs known from that region. Khosla et al. (2003) listed the following Indian sauropods:
* '' Titanosaurus indicus''
* ''T. blanfordi''
* ''T. rahiolensis''
* '' Jainosaurus septentrionalis''.

Wilson et al. (2009) listed only two Indian titanosaurs, ''Isisaurus'' and its distant relative, ''Jainosaurus''. ''Isisaurus'' and ''Jainosaurus'' lived sympatrically in the area of middle and western India. ''Isisaurus'' fossils have also been reported from western Pakistan.

Other dinosaurs, including the abelisaurs '' Indosuchus'', ''Rahiolisaurus'', and '' Rajasaurus'', also existed in the Lameta Formation.

References

{{Commons category, Isisaurus

Lithostrotians
Late Cretaceous dinosaurs
Dinosaurs of India and Madagascar
Fossil taxa described in 2003
Taxa named by Sohan Lal Jain