Epachthosaurus

Skeletal reconstruction of Epachthosaurus National Museum in Prague.

  • Argentina, Chubut ( Bajo- Barreal Formation)
  • Epachthosaurus sciuttoi

Epachthosaurus is a genus of sauropod dinosaur from the group of Titanosauria that during the early Cretaceous (late Cenomanian ) lived in South America.

While initially only a few were known vertebral and pelvic bones, could in 2004 a nearly complete, but skull -less skeleton are described - thus Epachthosaurus one of the most completely known genera of Titanosauria.

All findings are from the reference Ocho Hermanos in the Argentine province of Chubut, which is part of the Bajo- Barreal Formation and is dated to the late Cenomanian -early Turonian. So far, only the type species Epachthosaurus is sciuttoi described.

Features

Epachthosaurus was a medium sized sauropod with a length of about 18 meters. The weight of the almost perfectly preserved specimen is estimated by T. Galarza and J. Gallegos to 11.29 tons. In 10 of the 40 previously known Titanosauria skin bony plates ( osteoderms ) were detected. Because of Epachthosaurus despite the almost complete, articulated skeleton no osteoderms were discovered, it is assumed that these species actually wore no osteoderms.

From other genres to Epachthosaurus can differentiate by various autapomorphies ( unique features). While the back spine of most sauropods is reinforced with additional mechanical fasteners of the vertebral arches, the Hyposphen - Hypantrum connections, these structures are absent in almost all Titanosauria. Epachthosaurus However, similar Argentinosaur, secondary, and formed in analogy to the compounds Hyposphen - Hypantrum another particular type of fasteners to the vertebrae. Unique among titanosaurs is furthermore that Hyposphen - Hypantrum compounds were present in the 1 to 14 caudal vertebrae. These connecting elements as well as ossified tendons at the sacrum resulted in the spine of Epachthosaurus was probably significantly more rigid than that of other Titanosauria. The Phalangenformel, with the number of phalanges is described per toe of the hind foot is 2-2-3-2-0.

System

The exact systematic position within the Titanosauria is unclear. However, the caudal vertebrae were strong procoel (on the front concave), a feature which for derived (modern ) Titanosauria is typical ( Lithostrotia or Titanosauridae ). So is the very basal ( original ) Andesaurus throughout amphiplatische ( flattened on both sides ) caudal vertebrae. It was presumably at Epachthosaurus a basal Titanosauria, which is somewhere between Andesaurus and the more derived species.

History of discovery, discoveries and naming

Epachthosaurus was described in 1990 by Jaime Eduardo Powell for the first time scientifically, based on an isolated vertebrae, a series of six vertebrae, a part of the sacrum and a part of the pubic bone ( pubis ). Only the isolated vertebra ( holotype, specimen number MACN -CH 1317 ) could actually be collected - the rest of the bone ( copy number MACN -CH 18689 ) are still trapped at the site in the rock, as the surrounding rock matrix was too hard for an exposure. Instead, casts were made ​​from the visible to the surface portions of bone.

A nearly complete skeleton ( copy number UNPSJB - PV 920) was, in 1988 and 1989 by Martinez and colleagues described briefly, but a more extensive description published this research in 2004 This skeleton was at its discovery almost completely in the original anatomical composite -. It missing only the skull, neck, four to five anterior vertebrae and the posterior caudal vertebrae. Other fossils - a front vertebrae and parts of the basin ( copy numbers UNPSJB PV - 1006 and PV - UNPSJB 956) - were recognized in 2010 as Epachthosaurus sp. described.

All findings are from a reference within the Ocho Hermanos Ranch. This famous reference hid beside the Epachthosaurus fossils a number of other finds, including the skeletons of turtles Bonapartemys and Prochelidella, the Cerato Xenotarsosaurus dinosaurs and other, as yet undetermined sauropod remains. The site belongs to the upper portion of the lower layer member of the Bajo- Barreal lineup.

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 exploring the Ocho Hermanos locality.

Taphonomy

The nearly complete skeleton was found in the prone position, with folded his hind legs and the front legs were stretched out diagonally to the rear. The tail was curved to the right. The high degree of articulation of the skeleton suggests that it was transported to its embedding in the sediment by water. The sediments which buried the carcasses could have been entered by a seasonal flood event. Perhaps the lack of neck and skull are also fossilized, but went later lost by erosion, as the fossil came back to the earth's surface for days.

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