Epachthosaurus
| Epachthosaurus | ||||||||||||
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Skeletal reconstruction of Epachthosaurus in the Prague National Museum . |
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| Temporal occurrence | ||||||||||||
| Upper Cretaceous (late Cenomanian ) | ||||||||||||
| 95.5 to 93.9 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Epachthosaurus | ||||||||||||
| Powell , 1990 | ||||||||||||
| Art | ||||||||||||
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Epachthosaurus is a genus of sauropod dinosaur from the Titanosauria group thatlived in South Americaduring the Early Upper Cretaceous (late Cenomanian ).
While initially only a few vertebral and pelvic bones were known, in 2004 an almost complete, but skullless skeleton was described - thus Epachthosaurus is one of the most fully known genera of the Titanosauria.
All finds come from the Ocho Hermanos site in the Argentine province of Chubut , which is part of the Bajo Barreal Formation and is dated to the late Cenomanian to early Turonian . So far only the type species Epachthosaurus sciuttoi has been described.
features
Epachthosaurus was a medium-sized sauropod about 18 meters long. The weight of the almost completely preserved specimen is estimated by T. Galarza and J. Gallegos at 11.29 tons. Skin bone plates (osteoderms) have been detected in 10 of the more than 40 previously known Titanosauria . Since no osteoderms were discovered from Epachthosaurus despite the almost complete, articulated skeleton, it is assumed that this genus actually did not carry any osteoderms.
Epachthosaurus can be distinguished from other genera by various autapomorphies (unique features). While the back spine of most sauropods is reinforced by additional mechanical connecting elements of the vertebral arches, the hyposphene-hypantrum connections , these structures are absent in almost all titanosauria. However, similar to Argentinosaurus , Epachthosaurus developed a different, special type of connecting elements on the vertebrae in a secondary manner and in analogy to the hyposphene-hypantrum connections. What is also unique among titanosaurs is that hyposphene-hypantrum connections were present in the 1st to 14th caudal vertebrae. These connecting elements as well as ossified tendons on the sacrum meant that the spine of Epachthosaurus was probably much more rigid than that of other Titanosauria. The phalangeal formula used to describe the number of phalanges per toe of the hind foot is 2-2-3-2-0.
Systematics
The exact systematic position within the Titanosauria is unclear. The caudal vertebrae, however, were strongly procoel (concave on the front), a feature that is typical for derived (modern) Titanosauria ( Lithostrotia or Titanosauridae). The very basal (original) Andesaurus shows amphipathic (flattened on both sides) tail vertebrae throughout. Presumably, Epachthosaurus was a basal Titanosauria, which is located between Andesaurus and the more strongly derived genera.
History of discovery, finds and naming
Epachthosaurus was scientifically described for the first time in 1990 by Jaime Eduardo Powell , based on an isolated vertebra, a series of six vertebrae, part of the sacrum and part of the pubis . Only the isolated dorsal vertebra ( holotype , specimen number MACN-CH 1317) could actually be collected - the remaining bones (specimen number MACN-CH 18689) are still trapped in the rock at the site because the surrounding rock matrix was too hard to be exposed. Instead, casts were made of the bone parts visible on the surface.
An almost complete skeleton (copy number UNPSJB-PV 920) was briefly described by Martínez and colleagues in 1988 and 1989, but these researchers did not publish a more comprehensive description until 2004. When it was discovered, this skeleton was still almost completely in the original anatomical structure - es only the skull, neck, four to five front vertebrae and the rearmost caudal vertebrae are missing. Other fossils - an anterior vertebra and parts of the pelvis (specimen numbers UNPSJB-PV 1006 and UNPSJB-PV 956) - were identified as Epachthosaurus sp. described.
All finds come from a site within the ranch Ocho Hermanos . In addition to the Epachthosaurus fossils, this famous site contained a number of other finds, including the skeletons of the turtles Bonapartemys and Prochelidella , the ceratosaur Xenotarsosaurus and other, as yet undetermined sauropod remains. The site belongs to the upper section of the lower stratum of the Bajo Barreal Formation .
The name Epachthosaurus ( gr. Epakhthes - "heavy"; sauros - "lizard") means something like "heavy lizard". The second part of the species name, sciuttoi , honors Dr. JC Sciuttoi, who campaigned for the exploration of the Ocho Hermanos site.
Taphonomy
The almost complete skeleton was found in the prone position, with the hind legs folded and the front legs stretched backwards at an angle. The tail was curved to the right. The high degree of articulation of the skeleton indicates that it was not transported by water before it was embedded in the sediment. The sediments that buried the carcass could have been brought in by a seasonal flood event. The missing neck and skull may also have been fossilized, but were subsequently lost through erosion when the fossil reappeared on the surface of the earth.
Individual evidence
- ^ A b Thomas R. Holtz Jr .: Supplementary Information. to: Thomas R. Holtz Jr .: Dinosaurs. The most complete, up-to-date Encyclopedia for Dinosaur Lovers of all ages. Random House, New York NY 2007, ISBN 978-0-375-82419-7 , online (PDF; 184.08 kB) .
- ↑ a b c d e f g h Rubén D. Martínez, Olga Giménez, Jorge Rodríguez, Marcelo Luna, Matthew C. Lamanna: An articulated specimen of the basal titanosaurian (Dinosauria: Sauropoda) Epachthosaurus sciuttoi from the early Late Cretaceous Bajo Barreal Formation of Chubut province, Argentina. In: Journal of Vertebrate Paleontology. Vol. 24, No. 1, 2004, ISSN 0272-4634 , pp. 107-120, doi : 10.1671 / 9.1 .
- ↑ 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, pp. 165-177, doi : 10.1671 / 039.029.0131 .
- ↑ Sebastián Apesteguía: Evolution of the Hyposphene-Hypantrum Complex within Sauropoda. In: Virginia Tidwell, Kenneth Carpenter (Eds.): Thunder-lizards. The Sauropodomorph Dinosaurs. Indiana University Press, Bloomington IN et al. 2005, ISBN 0-253-34542-1 , pp. 248-267.
- Jump up ↑ Gabriel Casal, Lucio Ibiricu: Materiales asignables a Epachthosaurus Powell, 1990 (Sauropoda: Titanosauria), de la Formación Bajo Barreal, Cretácico Superior, Chubut, Argentinia. In: Revista Brasileira de Paleontologia. Vol. 13, No. 3, 2010, ISSN 1519-7530 , pp. 247-256, doi : 10.4072 / rbp.2010.3.08 .
- ↑ Jaime Eduardo Powell: Epachthosaurus sciuttoi (gen. Et sp. Nov.), Un dinosaurio sauropodo del Cretácico de Patagonia (Provincia de Chubut, Argentina). In: Actas del V Congreso Argentino de Paleontología y Bioestratigrafía, Tucumán, Argentina (= Serie Correlación Geológica. No. 7, ISSN 1514-4186 = Publicación (Universidad Nacional de Tucumán). No. 1434). Universidad Nacional de Tucumán - Instituto Superior de Correlación Geológica, San Miguel de Tucumán 1990, pp. 123-128.