Ostafrikasaurus

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

Ostafrikasaurus
Temporal range: Late Jurassic, (Tithonian) 152.1–145 Ma
Ostafrikasaurus by PaleoGeek Variant 1.png
Speculative restoration and holotype tooth
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Clade: Megalosauria
Family: Spinosauridae
Genus: Ostafrikasaurus
Buffetaut, 2012
Species:
O. crassiserratus
Binomial name
Ostafrikasaurus crassiserratus
Buffetaut, 2012

Ostafrikasaurus is a genus of spinosaurid theropod dinosaur known from the Jurassic of Tendaguru, southeastern Tanzania. It contains a single species, Ostafrikasaurus crassiserratus.[1]

Discovery and naming

Fossil excavation site during the Tendaguru expedition, 1912

During the time of the German colonial empire, the Museum für Naturkunde (Natural History Museum) of Berlin arranged an expedition in German East Africa (now Tanzania) that took place from 1909 to 1913; now considered by scientists as one of the largest expeditions in palaeontological history.[2][3] The expedition led to the discovery of the first bones from the sauropod Giraffatitan brancai, which was at the time described as a new species of Brachiosaurus. Most of the excavations were situated in the southeastern Tendaguru Formation, a fossil-rich site part of the Mandawa Basin.[2][3] Among the many dinosaur fossils retrieved from the dig sites was the holotype and only known specimen of Ostafrikasaurus, an isolated tooth catalogued as MB R 1084.[4] It was originally referred to Labrosaurus? stechowi in 1920 by German palaeontologist Werner Janensch, the fossil was one among 230 specimens of theropod teeth brought back from the Tendaguru.[5] A large and detailed monograph by Janensch published in 1925 assigned nine of these teeth to L.? stechowi and divided them into five morphotypes.[6]

The genus Ostafrikasaurus was named by French palaeontologist Eric Buffetaut in a 2012 paper, based his 2007 reinterpretation of the fossil teeth; the type species is Ostafrikasaurus crassiserratus. The generic name is derived from the German name of the colony in which the holotype was found, Deutsch-Ostafrika, meaning "German East Africa". It is combined with the Greek σαῦρος/sauros, which means "lizard" or "reptile". The specific name is derived from the Latin crassus, meaning "thick"; and serratus, meaning "serrated", in reference to the morphology of the holotype tooth.[4]

MB R 1084 was found in the Upper Dinosaur Member of the formation, it differs in several respects from the other eight teeth found in the Middle Dinosaur Member.[4] Although in 2008 Buffetaut suggested that another isolated tooth (MB R 1091) from the Middle Dinosaur Member, may represent the same genus as MB R 1084, when naming Ostafrikasaurus in 2012, he did not refer it to the genus.[4] The Upper Dinosaur Member of the Tendaguru Formation is composed mostly of siltstones, calcareous sandstones, and claystone beds. These rocks likely date back to the Tithonian stage of the Late Jurassic, approximately 152.1-145 million years ago.[3][7] However, the precise chronological boundary between the Early Cretaceous and Late Jurassic of the Tendaguru Formation is still unclear.

Description

Size comparison

The thick and serrated holotype tooth is about 49 mm (1.9 in) in length. Buffetaut (2008) suggested that this tooth represents a new genus of Spinosauridae, and that it differs from other teeth previously referred to L.? stechowi.[1] Oliver Rauhut (2011) listed some of these differences: MB R 1084 has a much higher number of lingual ridges (up to eleven) and presents three ridges and grooves on the labial side. Furthermore, some of the lingual ridges extend over almost the entire length of the crown, leaving only the apicalmost 5 mm of the crown smooth, whereas others are restricted to the basal part, being intercalated with ridges that extend further apically. Additionally, ridges are present over almost the entire mesial (front) threefifths of the crown, whereas the distal (back) two-fifths are devoid of any ornamentation. Mesially, the ridged area is slightly set off from the mesial carina by a slightly mesiodistally concave area. However, its general shape and serration density is very similar to the teeth from the Middle Dinosaur Marl, as all teeth have 10 denticles per 5 mm distally and 13 denticles per 5 mm mesially. Finally, Rauhut suggested that it is possible that this tooth represents the same taxon as the other teeth, or a closely related taxon.[8]

Classification

In 2012 Buffetaut assigned Ostafrikasaurus to the Spinosauridae, based on the fact that the tooth displays an enamel ornamentation that resembles many baryonychines including Baryonyx, but differs from all other known spinosaurids by the large size of the denticles borne by the carinae. Thus, Ostafrikasaurus, according to Buffetaut, represents the earliest currently known spinosaurid. The tooth suggests that the dental evolution of spinosaurids could have been characterised by reduction of the denticles.[1]

Palaeoecology

Depiction of two Dicraeosaurus traversing tidal flats in the Tendaguru Formation

Ostafrikasaurus' habitat would have been subtropical to tropical, shifting between periodic rainfall and pronounced dry seasons. Three types of palaeoenvironments were present at the Tendaguru Formation, the first was a shallow water marine setting with lagoon-like conditions shielded behind shoals of ooid and siliciclastic rocks, evidently subjected to tides and storms. The second was a coastal environment of tidal flats, consisting of brackish water lakes, ponds, and fluvial channels. There was little plant-life in these environments for sauropods to feed on and most dinosaurs likely came to these areas only during droughts. The third and most inland habitat would have been dominated by conifer plants in a well-vegetated area, offering a large feeding ground for sauropod dinosaurs.[9]

Extensive fossil finds have revealed that the Tendaguru was home to a diverse abundance of organisms. Invertebrates like bivalves, gastropods, oysters, echinoderms, arthropods, brachiopods, corals, and many microfauna are known from the deposits. Sauropod dinosaurs were prominent in the region, represented by Giraffatitan brancai, Dicraeosaurus hansemanni and D. sattleri, Australodocus bohetii, Janenschia robusta, Tornieria africana and Tendaguria tanzaniensis; they would have coexisted with low-browsing ornithischians like the ornithopod Dysalotosaurus lettowvorbecki, and the stegosaurian Kentrosaurus aethiopicus.[10][11] Theropods besides Ostafrikasaurus included the carcharodontosaurid Veterupristisaurus milneri and the noasaurid Elaphrosaurus bambergi. Fragmentary material from the formation also indicates the presence of a basal ceratosaur and tetanuran, an unidentified abelisaur, as well as a possible abelisaurid, carcharodontosaurid, and megalosauroid.[8]

Many other vertebrates contemporary with Ostafrikasaurus have been found at the formation, such as amphibians, lizards, bony and cartilaginous fish, various small mammals, the pterosaur Tendaguripterus, and the crocodile Bernissartia.[10] Buffetaut (2012) stated that due to the presence of such a basal spinosaurid taxa in Africa, spinosaurids may have been widely distributed early in their evolutionary history.[1]

References

  1. ^ a b c d Buffetaut, Eric (2012). "An early spinosaurid dinosaur from the Late Jurassic of Tendaguru (Tanzania) and the evolution of the spinosaurid dentition" (PDF). Oryctos. 10: 1–8.
  2. ^ a b Tamborini, Marco; Vennen, Mareike (2017-06-05). "Disruptions and changing habits: The case of the Tendaguru expedition". Museum History Journal. 10 (2): 183–199. doi:10.1080/19369816.2017.1328872. ISSN 1936-9816.
  3. ^ a b c Bussert, Robert; Heinrich, Wolf-Dieter; Aberhan, Martin (2009-08-01). "The Tendaguru Formation (Late Jurassic to Early Cretaceous, southern Tanzania): definition, palaeoenvironments, and sequence stratigraphy". Fossil Record. 12 (2): 141–174. doi:10.1002/mmng.200900004.
  4. ^ a b c d Buffetaut, Eric (2012). "An early spinosaurid dinosaur from the Late Jurassic of Tendaguru (Tanzania) and the evolution of the spinosaurid dentition" (PDF). Oryctos. 10: 1–8.
  5. ^ W. Janensch, 1920, "Ueber Elaphrosaurus bambergi und die Megalosaurier aus den Tendaguru-Schichten Deutsch-Ostafrikas", Sitzungsberichte der Gesellschaft Naturforschender Freunde zu Berlin 1920: 225-235
  6. ^ Janensch, W., 1925, "Die Coelurosaurier und Theropoden der Tendaguru-Schichten Deutsch-Ostafrikas", Palaeontographica Supplement 7: 1–99
  7. ^ "ICS - Chart/Time Scale". www.stratigraphy.org. Retrieved 2018-07-13.
  8. ^ a b Rauhut, Oliver W. M. (2011). "Theropod dinosaurs from the Late Jurassic of Tendaguru (Tanzania)". Special Papers in Palaeontology. 86: 195–239. doi:10.1111/j.1475-4983.2011.01084.x (inactive 2019-08-20).
  9. ^ Aberhan, Martin; Bussert, R; Heinrich, Wolf-Dieter; Schrank, E; Schultka, Stephan; Sames, Benjamin; Kriwet, Jürgen; Kapilima, S (2002-01-01). "Palaeoecology and depositional environments of the Tendaguru Beds (Late Jurassic to Early Cretaceous, Tanzania)". Fossil Record. 5: 19–44. doi:10.5194/fr-5-19-2002.
  10. ^ a b Bussert, Robert; Heinrich, Wolf-Dieter; Aberhan, Martin (2009-08-01). "The Tendaguru Formation (Late Jurassic to Early Cretaceous, southern Tanzania): definition, palaeoenvironments, and sequence stratigraphy". Fossil Record. 12 (2): 141–174. doi:10.1002/mmng.200900004.
  11. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 132. ISBN 978-1-84028-152-1.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Ostafrikasaurus&oldid=916547801"
This content was retrieved from Wikipedia : http://en.wikipedia.org/wiki/Ostafrikasaurus
This page is based on the copyrighted Wikipedia article "Ostafrikasaurus"; it is used under the Creative Commons Attribution-ShareAlike 3.0 Unported License (CC-BY-SA). You may redistribute it, verbatim or modified, providing that you comply with the terms of the CC-BY-SA