Ctenosauriscus
The holotype of Ctenosauriscus. Get vortex are with the highly elongated spinous processes and some ribs.
- Lower Saxony, Germany
- Ctenosauriscus koeneni
Ctenosauriscus is an extinct genus of Archosauria from the group Poposauroidea. The so far only find dates from the Middle Buntsandstein of Lower Saxony (late Olenekian, Lower Triassic ). Ctenosauriscus is the eponymous representative of Ctenosauriscidae, a family, which is characterized by a high ridge sail. Ctenosauriscus lived during the Olenekiums (before about 247 million years ago), making it one of the oldest archosaurs. The genus was first described by Friedrich von Huene in 1902 and 1964 as Ctenosaurus renamed by Oskar Kuhn in Ctenosauriscus.
Description
The most striking feature of Ctenosauriscus is the back sail, which is formed by the elongated spinous processes of the cervical and dorsal vertebrae. The spinous processes are slightly curved in the front area of the sail to the front and the rear of the sail slight backwards. Some other members of the Poposauroidea how Lotosaurus and Ctenosaurisciden Hypselorhachis and Xilousuchus, also showed prolonged spinous processes - but the sail of Ctenosauriscus was one of the largest of this group. Ctenosauriscus is Arizonasaurus from the Middle Triassic of the southwestern USA most similar. Both classes showed on spinous processes, which were up to 12 times as high as the vertebral body. In Centosauriscus the ends of the spinous processes are wider than in related genera, as well as the postal and prezygapophyses ( mechanical connecting elements of the vertebrae) were larger and more robust. The related Hypselorhachis also had widened at the top of the spinous processes; these were, however, shorter than Ctenosauriscus. Also Lotosaurus from the Middle Triassic of China shows elongated spinous processes, but straighter, wider and much shorter than in the case were Ctenosauriscus.
System
Ctenosauriscus is the eponymous representative of Ctenosauriscidae. Typical of this group are back sailing, which are formed from elongated spinous processes of the vertebrae. The Ctenosauriscidae were particularly common during the Lower and Middle Triassic in Eurasia and North America. Representatives of the group include Arizonasaurus from the Moenkopi Formation in Arizona ( USA), Hypselorhachis from the Manda Formation of Tanzania, Xilousuchus from the Chinese Heshanggou lineup, the little-known British Bromsgroveia from Bromsgrove - Sandstone formation, as well as an untitled copy from the German Röt lineup with a. Butler et al. (2011 ) defines the Ctenosauriscidae as a trunk line based taxon ( stem- based definition), which includes all taxa that koeneni as gracilis closer with Ctenosauriscus with Poposaurus, Effigia okeeffeae, Postosuchus kirkpatricki, Crocodylus niloticus, Ornithosuchus longidens or Aetosaurus Ferratus are related.
The Ctenosauriscidae be placed in the Poposauroidea. The sister taxon of Ctenosauriscidae forms an unnamed group of derived genera of Poposauroidea how Poposaurus, Sillosuchus and Shuvosaurus. The relationships within the Ctenosauriscidae are unclear. Below is a cladogram according to Butler et al. (2011):
Lotosaurus
Sillosuchus
Poposaurus
Shuvosaurus
Effigia
Hypselorhachis
Ctenosauriscus
Arizonasaurus
Bromsgroveia
Hypselorhachis
Unnamed Ctenosauriscide
Research and discovery history
Ctenosauriscus is only known by a single Fund ( holotype, specimen number GZG.V.4191 ), consisting of a partial postcranial skeleton including an incomplete spinal column, ribs, and possibly some elements of the shoulder girdle. The Fund is available on four sandstone slabs. The first plate (as cataloged A1 ) contains vertebrae, while the second plate (B1 ) contains tail, sacrum, and the posterior dorsal vertebrae. Two further plates ( A2, B2) each of which forms the counter- plates A1 and B1.
The specimen was found at the beginning of 1871 in a quarry of Bremketals southeast of Göttingen. It comes from the Solling- Bausandstein, a unit of the Solling Formation of the Middle Buntsandstein. Later that year it was donated by the architect Eduard Freise the University of Göttingen. The first description as Ctenosaurus koeneni published Friedrich von Huene in 1902, but only on the basis of a photograph of the fossil. Later traveled von Huene himself to Göttingen to study the fossil directly, and published in 1914 a more extensive description.
Von Huene suspected that C. koeneni a later Pelycosaurier was - a distantly related to the mammalian Synapside. Such basal synapsids are mainly known from the Pennsylvanian ( Upper Carboniferous ) and Permian. Von Huene this assignment reasoned with the similarity of this animal to sail bearing Pelycosauriern as Dimetrodon. The Austrian paleontologist Othenio Abel C. koeneni classified as amphibian from the group Temnospondyli, which should have been closely related to the back sail carrying Platyhystrix which, like Dimetrodon comes from the Lower Permian.
Later it was found that the selected von Huene Ctenosaurus name was already taken and the black iguanas (now Ctenosaura ) designated, so the genus of the paleontologist Oskar Kuhn in 1964 was renamed. B. Krebs described the holotype in 1969 and newly recognized Ctenosauriscus as a representative of the Archosauria, based on similarities with the sail -carrying Pseudosuchier Hypselorhachis from the Middle Triassic of Tanzania.
Ctenosauriscus was found in the Solling Formation, which is dated at 247.5 to 247.2 million years. This dating is based on radiometric methods and measurements on the Milankovitch cycles.
A research team led by Richard J. Butler published in 2011, a redescription of the holotype. Although it saw no autapomorphies ( unique features ), but noted that the holotype of other Ctenosaurisciden can be distinguished by a unique combination of features. Ctenosauriscus is considered one of the oldest archosaurs; about the same age was Vytshegdosuchus from Russia and probably Xilousuchus, a Ctenosauriscidae from China.
Paleobiology
Bipedalism
A study by Ebel and colleagues ( 1998) comes to the conclusion Ctenosauriscus have bipedal running ( biped ) moves, with the elongated spinous processes of the vertebrae should have cushioned the forces acting on two legs while running. Although no bones have been preserved, these researchers suggest that the forces at work on the upper ends of the spinous processes, were focused to a point below the vertebral column, in which it could have been around the knee joint. Butler and colleagues ( 2011) contradict this hypothesis and argue that muscle would constitute a direct connection between the knee and back, to create such forces between the knee joint and spinous processes. Instead, the forces would, however, transfer of the hind legs to the pelvis and sacral vertebrae, and not on the vertebrae. In addition, the sail of Ctenosauriscus would have shifted the focus of the body forward, which would make a bipedal locomotion difficult to impossible.