Agustinia
| Agustinia | ||||||||||||
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Live reconstruction of Agustinia ligabuei |
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| Temporal occurrence | ||||||||||||
| Lower Cretaceous (Upper Aptian to Lower Albian ) | ||||||||||||
| 123 to 110.2 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Agustinia | ||||||||||||
| Bonaparte , 1999 | ||||||||||||
| Art | ||||||||||||
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Agustinia is a genus of sauropod dinosaur that lived in the Lower Cretaceous South America. The only species described is Agustinia ligabuei .
The fossil remains of Agustinia consist only of series of the spinous processes of the dorsal, sacrum and caudal vertebrae, parts of the hind legs and at least three different types of skin ossification (probably osteoderms ). These skin ossifications are preserved in the form of plates and spikes and could have been arranged along the back line. A recent study notes, however, that these bones may not have been osteoderms, but simple, age-related ossifications. The fossils come from the Lohan Cura Formation (Upper Aptian to Lower Albian ) in Patagonia ( Argentina ) and were scientifically described by José Bonaparte in 1999 .
features
The remnants of 18 vertebrae were discovered in two rock blocks, the first block including the three posterior vertebrae, six sacral vertebrae, and two anterior caudal vertebrae, while the second block consists of eight of the anterior and middle caudal vertebrae. The vertebrae are badly weathered, which is why only spinous processes have been preserved. The position of the vertebral remnants in a row, however, indicates that the vertebrae have shifted little after the animal's death, and represent a series of consecutive, articulated vertebrae.
Eight well-preserved osteoderm-like bones are known, six of which seem to have been preserved in the living position on the vertebral series. José Bonaparte writes that these bones, which he interpreted as osteoderms , were arranged in two parallel rows following the vertebrae of the back and sacrum. He also suspects that the osteoderms could have been mechanically connected to each other and to the spinous processes of the vertebrae by tissue. There were at least three unique types of skin ossification present in this form in no other dinosaur: On the one hand, there was a leaf-shaped plate with a diameter of 21 centimeters. A second type is represented by a thin plate with a diameter of 64 centimeters, which shows two lateral appendages, which possibly represent the bases of earlier long spines. Another four osteoderms each show a lateral process; presumably these are halves of the second type. A third type is characterized by spiky bones that are up to 80 centimeters long and split at one end. According to Bonaparte, these three types of osteoderm can be used to distinguish this genus from other genera.
Bonaparte also found six sacral vertebrae, a feature that only the Titanosauria show among the sauropods . The shin and fibula are two feet long. The lower half of the tibia was thin when viewed from the front (anteroposterior), indicating that the tibia was thinner than that of titanosaurs such as Antarctosaurus or Saltasaurus . The foot bones correspond to those of the titanosaurs.
Systematics
The scanty remains make it difficult to classify Agustinia taxonomically. Similarities with the Diplodocoidea and the Titanosauria were found, whereby the presumed osteoderms and the six sacral vertebrae speak for an affiliation to the Titanosauria. Upchurch and colleagues (2004) regard Agustinia as a Titanosauria (Titanosauria incertae sedis ) that cannot be further assigned . Kristina Curry Rogers assigns Agustinia within the Titanosauria to the group Lithostrotia , which includes more modern forms.
Researchers working with Michael D'emic (2009) note, however, that the remains of the sacral vertebrae found are not clearly connected to one another, but that the rearmost and foremost vertebrae are separated from the rest of the vertebral series. It is therefore not clear whether Agustinia actually had six sacral vertebrae like the Titanosauria. Furthermore, the supposed osteoderms differ from the osteoderms of other archosaurs . Michael D'emic and colleagues note that it cannot be ruled out that these bones were not osteoderms at all, but age-related ossification, as was also discovered in the sacrum region of Camarasaurus . The researchers conclude that there is no unique features are present that would allow a classification within the diplodocoidea or titanosaur, and classify agustinia therefore as not attributable Neosauropoden (neosauropoda incertae sedis ).
Bonaparte assigned Agustinia in his first description to a separate family , the Agustiniidae. This family - just like Agustinia itself - should be delimited by the presence of the three types of osteoderms. However, this family has not found widespread acceptance among researchers.
Find and naming
The only find so far was discovered in 1997 by an expedition from the Museo Argentino de Ciencias Naturales ( Buenos Aires ) a few kilometers west of the city of Picún Leufú in the south of the Neuquén province . The rocks of the site belong stratigraphically to the upper section of the Lohan Cura Formation . This excursion was part of a program run by the museum in 1996 and 1997 to discover new vertebrate fossils in the Lohan Cura Formation. A year earlier (1996) a new sauropod was discovered 50 kilometers west of Picún Leufú.
The name Agustinia honors the then student Agustin Martinelli, who discovered the skeleton and was part of the excavation team of the Museo Argentino de Ciencias Naturales . The Artepitheth ligabuei honors Giancarlo Ligabue, an Italian supporter of the 1997 expedition into the Lohan-Cura formation.
The find ( holotype , copy number MCF-PVPH-110) is now in the Cármen Funes Museum in Plaza Huincul . It consists of the vertebral arches and spines of three dorsal, six sacral and ten caudal vertebrae. In addition, the almost complete right was shinbone (tibia) and fibula (fibula), five articulated left metatarsal and nine dermal bones discovered.
supporting documents
Main source
- Jose F. Bonaparte : An armored sauropod from the Aptian of northern Patagonia, Argentina. In: Yukimitsu Tomida, Thomas H. Rich , Patricia Vickers-Rich (Eds.): Proceedings of the Second Gondwanan Dinosaur Symposium. (Held at the National Science Museum in Tokyo on July 12-13, 1998) (= National Science Museum monographs. No. 15, ISSN 1342-9574 ). National Science Museum, Tokyo 1999, pp. 1–12, digitized version (PDF, 940.23 kB) .
Individual evidence
- ^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , p. 205, online .
- ↑ a b Michael D. D'Emic, Jeffrey A. Wilson, Sankar Chatterjee : The titanosaur (Dinosauria: Sauropoda) osteoderm record: review and first definitive specimen from India. In: Journal of Vertebrate Paleontology. Vol. 29, No. 1, 2009, ISSN 0272-4634 , pp. 165-177, doi : 10.1671 / 039.029.0131 .
- ^ A b 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 A. 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, doi : 10.1525 / california / 9780520246232.003.0003 .