Isisaurus
| Isisaurus | ||||||||||||
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| Temporal occurrence | ||||||||||||
| Upper Cretaceous ( Maastrichtian ) | ||||||||||||
| 72 to 66 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Isisaurus | ||||||||||||
| Wilson & Upchurch , 2003 | ||||||||||||
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Isisaurus is a genus of sauropod dinosaur from the Titanosauria group . So far, a single fragmentary, skullless skeleton is known, which comes from the late Upper Cretaceous ( Maastrichtian ) India . The only species is Isisaurus colberti .
Initially, this skeleton was described in 1997 as a type of Titanosaurus - Titanosaurus colberti . In 2003, Jeffrey A. Wilson and Paul Upchurch found that this species must actually be assigned to a genus of its own, which they called Isisaurus .
features
Isisaurus was a medium-sized sauropod. Like all sauropods, this herbivore was characterized by a barrel-shaped body and a long neck and tail. Isisaurus belonged to the more advanced (more derived) Titanosauria, which is shown by a number of jointly derived features ( synapomorphies ): For example, the additional mechanical connecting elements of the vertebrae, the hyposphere-hypantrum connections , which are typical for other sauropod groups, were missing , which made the spine more flexible. In addition, the ulna showed a pronounced olecranon , a bone spur that extended at the upper end to over the articular cartilage . Furthermore, the anterior spinous processes of the caudal vertebrae were relatively wide, while the vertebral bodies of the anterior and middle caudal vertebrae were strongly concave (procoel) on the anterior side.
Isisaurus differs from other Titanosauria through various unique features ( autapomorphies ) on the vertebrae: For example, the parapophyses of the caudal vertebrae were elongated in the direction of the body axis (anteroposterior). In addition, the chevron bones were shortened in the direction of the body axis.
Systematics
The relationships within the Titanosauria are controversial. Isisaurus is usually classified within the Lithostrotia (= Titanosauriae), a group of more advanced Titanosauria. Within the Lithostrotia, the Saltasauridae group is often led, which includes very advanced Titanosauria such as Saltasaurus . While Wilson (2002) considers Isisaurus to be the sister taxon of the Saltasauridae - that means classifying the genus outside of the Saltasauridae - Curry Rogers (2005) suggests a classification within the Saltasauridae - as a representative of the Opisthocoelicaudiinae .
Paleobiology
Researchers working with Neeta Sharma (2005) discovered fossilized dung ( coprolite ) that could have come from Isisaurus . These coprolites contained various fungi that enter the intestinal tract of these animals via the leaves of trees. From this, the researchers conclude that Isisaurus grazed the canopy of trees.
Find, research history and naming
The site is located near Dongargaon Hill District Chandrapur in Maharashtra in central India. The rocks at the site belong to the Lameta Formation and were deposited during the Maastrichtian , the last stage of the Upper Cretaceous . The skeleton ( holotype , specimen number ISI R335 / 1-65) is associated and well preserved, in contrast to almost all other Indian dinosaur finds, which mostly consist of isolated bones. It consists of parts of the spine, shoulder girdle, pelvis and a front leg without a hand skeleton. Skull bones were not found.
This skeleton was first scientifically described by Jain and Bandyopadhyay in 1997 as Titanosaurus colberti . The skeleton overlaps with the type material of Titanosaurus , which only consists of two central caudal vertebrae, which allows a direct comparison. Jain and Bandyopadhyay noted important differences, such as the shape of the vertebral bodies and the definition of the attachment points of the chevron bones. However, Upchurch and Wilson (2003) note that these differences are too great and that the common features are insufficient to continue to consider Titanosaurus colberti as a species of Titanosaurus . Thus, they described the skeleton as a new genus - Isisaurus .
The name isisaurus honors the Indian Statistical Institute ( Indian Statistical Institute , ISI), whose scientists have discovered the skeleton and first described. The ending saurus is ancient Greek for lizard.
Individual evidence
- ^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ 2010, ISBN 978-0-691-13720-9 , p. 206, online ( memento of the original of July 13, 2015 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. .
- ↑ a b c d e f g Jeffrey A. Wilson, Paul Upchurch : A revision of Titanosaurus Lydekker (dinosauria - sauropoda), the first dinosaur genus with a "Gondwanan" distribution. In: Journal of Systematic Palaeontology. Vol. 1, No. 3, 2003, pp. 125-160, doi : 10.1017 / S1477201903001044 .
- ^ Paul Upchurch, Paul M. Barrett , Peter Dodson : Sauropoda. In: David B. Weishampel , Peter Dodson, Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. 2004, ISBN 0-520-24209-2 , pp. 259-324.
- ↑ Kristina Curry Rogers: Titanosauria. A Phylogenetic Overview. In: Kristina Curry Rogers, Jeffrey A. Wilson (Eds.): The Sauropods. Evolution and Paleobiology. University of California Press, Berkeley CA et al. 2005, ISBN 0-520-24623-3 , pp. 50-103.
- ↑ Neeta Sharma, RK Kar, Anil Agarwal, Ratan Kar: Fungi in dinosaurian (Isisaurus) coprolites from the Lameta Formation (Maastrichtian) and its reflection on food habit and environment. In: Micropaleontology. Vol. 51, No. 1, 2005, ISSN 0026-2803 , pp. 73-82, doi : 10.2113 / 51.1.73 .
