Nigersaurus

Nigersaurus Temporal range: Early Cretaceous
Mounted skeleton cast
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Sauropsida
Superorder:	Dinosauria
Order:	Saurischia
Suborder:	Sauropodomorpha
Family:	Rebbachisauridae
Genus:	Nigersaurus Sereno et al., 1999
Species
N. taqueti Sereno et al., 1999 (type)

Nigersaurus (meaning "Niger lizard") is a genus of diplodocoid sauropod dinosaur from the middle Cretaceous period, about 119 to 99 million years ago during the Aptian or Albian age. This dinosaur was described by Paul Sereno and colleagues in 1999.^[1] It is one of the most common genera found in the rich fossil vertebrate fauna of the Elrhaz Formation, Gadoufaoua, in the Niger Republic, discovered by Philippe Taquet, and described in a paper published in 1976.^[2]

Skeletal diagram of Nigersaurus taqueti, known remains shown in upper right

Nigersaurus was a plant-eater that had an unusual mouth "shaped like the wide intake slot of a vacuum" that took in food and chewed it with over a hundred very small, sharp teeth.^[3] Previously, such tooth batteries have been known only in hadrosaur and ceratopsian dinosaurs, but the discovery of Nigersaurus showed that at least one sauropod lineage, the rebbachisaurids, had them, as well.

Although a common genus, Nigersaurus had been poorly known until 2005, because of the delicate and highly pneumatic (filled with air spaces) construction of the skull and skeleton, which means that the fossil remains have been disarticulated. Sereno and Jeffrey A. Wilson in 2005 provided the first description of the skull and feeding adaptations. Nigersaurus had as many as 500 [1] or 600 teeth in its shovel-shaped head.^[4] In 2007 an article published in the Public Library of Science (PLoS) by Sereno et al. detailed the unique anatomy of Nigersaurus. Study of its inner ear shows that Nigersaurus head was oriented downwards and was best suited for low level browsing.^[5]

The New York Times reports:

"In contrast to other plant-eating dinosaurs, this one had more than 50 columns of teeth, all lined up along the jaws’ front edges, forming, in effect, foot-long scissors. The CT scans of the jawbones showed up to nine replacement teeth stacked behind each cutting tooth. When one wore out, another immediately took its place, at a rate, perhaps, of one a month in each column. 'Among dinosaurs,' Dr. Sereno said, 'Nigersaurus sets the Guinness record for tooth replacement.'" ^[6]

Model of Nigersaurus taqueti head at the Australian Museum, Sydney.

Like other sauropods from what used to be Gondwana, it had a shorter neck than Laurasian sauropods like Barosaurus. Despite these stockier proportions, Nigersaurus reached about 9 meters (29.5 ft) in length. At nine meters in length, Nigersaurus was smaller than other members of the Rebbachisaur family, such as Rebbachisaurus itself, a large animal with a distinctive low spinal ridge on its back. Nigersaurus, although smaller, had a similar ridge, which in life would have consisted of skin and perhaps also flesh stretched across elongate neural spines in the vertebrae.

References

1. ^ Sereno, P.C., Beck, A.L., Dutheil, D.B., Larsson, H.C.E., Lyon, G.H., Moussa, B., Sadleir, R.W., Sidor, C.A., Varricchio, D.J., Wilson, G.P, and Wilson, J.A. (1999). "Cretaceous Sauropods from the Sahara and the Uneven Rate of Skeletal Evolution Among Dinosaurs". Science, 286(5443): 1342-1347 (Nov 12 1999).
2. ^ Taquet, P. (1976). "Géologie et paléontologie du gisement de Gadoufaoua. (Aptien du Niger)". Cahiers de paléontologie, Paris, 191 pp.
3. ^ Dinosaur found with vacuum-cleaner mouth - Science - MSNBC.com
4. ^ Wilson, J. A. and Sereno, P. C. (2005). "Structure and Evolution of a Sauropod Tooth Battery". In Curry Rogers, K., and Wilson, J.A. (eds.), The Sauropods: Evolution and Paleobiology, University of California Press, Berkeley, ISBN 0-520-24623-3.
5. ^ Sereno PC, Wilson JA, Witmer LM, Whitlock JA, Maga A, et al. (2007) Structural Extremes in a Cretaceous Dinosaur. PLoS ONE 2(11): e1230. doi:10.1371/journal.pone.0001230.
6. ^ New York Times article A Cowlike Dinosaur Comes Into Focus published 2007-11-16.

External links

• Dinosaur Expedition 2000
• NPR - "'Mesozoic Cow' Rises from the Sahara Desert" by Christopher Joyce
• University of Michigan - The University Record - "U-M researchers study toothy, ground-feeding dinosaur" by Nancy Ross-Flanigan

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