Ostafrikasaurus

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

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

Discovery and naming

Am Tendaguru - Leben und Wirken einer deutschen Forschungsexpedition zur Ausgrabung vorweltlicher Riesensaurier in Deutsch-Ostafrika (1912) (18161657722)
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

Ostafrikasaurus Comparison PaleoGeek
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

Dicraeosaurus BW
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.
2012 in archosaur paleontology

The year 2012 in Archosaur paleontology was eventful. Archosaurs include the only living dinosaur group — birds — and the reptile crocodilians, plus all extinct dinosaurs, extinct crocodilian relatives, and pterosaurs. Archosaur palaeontology is the scientific study of those animals, especially as they existed before the Holocene Epoch began about 11,700 years ago. The year 2012 in paleontology included various significant developments regarding archosaurs.

This article records new taxa of fossil archosaurs of every kind that have been described during the year 2012, as well as other significant discoveries and events related to paleontology of archosaurs that occurred in the year 2012.

Giraffatitan

Giraffatitan (name meaning "titanic giraffe") is a genus of sauropod dinosaur that lived during the late Jurassic Period (Kimmeridgian–Tithonian stages). It was originally named as an African species of Brachiosaurus (B. brancai), but this has since been changed. Giraffatitan was for many decades known as the largest dinosaur but recent discoveries of several larger dinosaurs prove otherwise; giant titanosaurians appear to have surpassed Giraffatitan in terms of sheer mass. Also, the sauropod dinosaur Sauroposeidon is estimated to be taller and possibly heavier than Giraffatitan.

All size estimates for Giraffatitan are based on the specimen HMN SII, a subadult individual between 21.8–22.5 metres (72–74 ft) in length and about 12 meters (39 ft) tall. Mass estimates are varied and range from as little as 15 tonnes (17 short tons) to as much as 78.3 tonnes (86.3 short tons) but there is evidence supporting that these animals could grow larger; specimen HMN XV2, represented by a fibula 13% larger than the corresponding material on HMN SII, might have attained 26 metres (85 ft) in length or longer.

Kentrosaurus

Kentrosaurus ( KEN-tro-SAWR-əs) is a genus of stegosaurian dinosaur from the Late Jurassic of Tanzania. The type species is K. aethiopicus, named and described by German palaeontologist Edwin Hennig in 1915. Often thought to be a "primitive" member of the Stegosauria, several recent cladistic analyses find it as more derived than many other stegosaurs, and a close relative of Stegosaurus from the North American Morrison Formation within the Stegosauridae.

Fossils of K. aethiopicus have been found only in the Tendaguru Formation, dated to the late Kimmeridgian and early Tithonian ages, about 152 million years ago. Hundreds of bones were unearthed by German expeditions to German East Africa between 1909 and 1912. Although no complete skeletons are known, the remains provided a nearly complete picture of the build of the animal.

Kentrosaurus generally measured around 4.5 metres (15 ft) in length as an adult, and weighed about one tonne (1.1 tons). It walked on all fours with straight hindlimbs. It had a small, elongated head with a beak used to bite off plant material that would be digested in a large gut. It had a, probably double, row of small plates running down its neck and back. These plates gradually merged into spikes on the hip and tail. The longest spikes were on the tail end and were used to actively defend the animal. There also was a long spike on each shoulder. The thigh bones come in two different types, suggesting that one sex was larger and more stout than the other.

List of African dinosaurs

This is a list of dinosaurs whose remains have been recovered from Africa. Africa has a rich fossil record, but it is patchy and incomplete. It is rich in Triassic and Early Jurassic dinosaurs. African dinosaurs from these time periods include Coelophysis, Dracovenator, Melanorosaurus, Massospondylus, Euskelosaurus, Heterodontosaurus, Abrictosaurus, and Lesothosaurus. In the Middle Jurassic, the sauropods Atlasaurus, Chebsaurus, Jobaria, and Spinophorosaurus, flourished, as well as the theropod Afrovenator. The Late Jurassic is well represented in Africa, mainly thanks to the spectacular Tendaguru Formation. Veterupristisaurus, Ostafrikasaurus, Elaphrosaurus, Giraffatitan, Dicraeosaurus, Janenschia, Tornieria, Tendaguria, Kentrosaurus, and Dysalotosaurus are among the dinosaurs whose remains have been recovered from Tendaguru. This fauna seems to show strong similarities to that of the Morrison Formation in the United States and the Lourinha Formation in Portugal. For example, similar theropods, ornithopods and sauropods have been found in both the Tendaguru and the Morrison. This has important biogeographical implications.

The Early Cretaceous in Africa is known primarily from the northern part of the continent, particularly Niger. Suchomimus, Elrhazosaurus, Rebbachisaurus, Nigersaurus, Kryptops, Nqwebasaurus, and Paranthodon are some of the Early Cretaceous dinosaurs known from Africa. The Early Cretaceous was an important time for the dinosaurs of Africa because it was when Africa finally separated from South America, forming the South Atlantic Ocean. This was an important event because now the dinosaurs of Africa started developing endemism because of isolation.

The Late Cretaceous of Africa is known mainly from North Africa. During the early part of the Late Cretaceous, North Africa was home to a rich dinosaur fauna. It includes Spinosaurus, Carcharodontosaurus, Rugops, Bahariasaurus, Deltadromeus, Paralititan, Aegyptosaurus, and Ouranosaurus.

List of dinosaur genera

This list of dinosaurs is a comprehensive listing of all genera that have ever been included in the superorder Dinosauria, excluding class Aves (birds, both living and those known only from fossils) and purely vernacular terms.

The list includes all commonly accepted genera, but also genera that are now considered invalid, doubtful (nomen dubium), or were not formally published (nomen nudum), as well as junior synonyms of more established names, and genera that are no longer considered dinosaurs. Many listed names have been reclassified as everything from birds to crocodilians to petrified wood. The list contains 1559 names, of which approximately 1192 are considered either valid dinosaur genera or nomina dubia.

Spinosauridae

Spinosauridae (meaning "spined lizards") is a family of megalosauroidean theropod dinosaurs. The genus Spinosaurus, from which the family, subfamily, and tribe borrow their names, is the longest terrestrial predator known from the fossil record, and likely reached lengths of 15 m (49 ft). Most spinosaurids lived during the Cretaceous Period, with possible origins in the Late Jurassic, and fossils of them have been recovered worldwide, including in Africa, Europe, South America, Asia, and Australia, although none have been formally named from the latter continent. Spinosaur remains have generally been attributed to the Early to Mid Cretaceous, with the exception of the Ostafrikasaurus from the Late Jurassic.

Spinosaurids were large bipedal carnivores with elongated, crocodile-like skulls lined with conical teeth bearing little to no serrations, and small crests on top of their heads. The teeth in the front end of their lower jaws fanned out into a spoon-shaped structure similar to a rosette, which gave the animal a characteristic look. Their shoulders were robust, prominent and bore stocky forelimbs with giant "hooked" claws on the first finger of their hands. Many genera had unusually tall neural spines on their vertebrae, which supported sails or humps of skin or fat tissue.

Direct fossil evidence and anatomical adaptations indicate that spinosaurids were at least partly piscivorous, with additional fossil finds indicating they also hunted pterosaurs and small to medium-sized dinosaurs. Osteological analyses have suggested a semiaquatic lifestyle for some members of this clade.

Tendaguru Formation

The Tendaguru Formation, or Tendaguru Beds are a highly fossiliferous formation and Lagerstätte in southeastern Tanzania. The formation represents the oldest sedimentary unit of the Mandawa Basin, overlying Neoproterozoic basement, separating by a long hiatus and unconformity. The formation reaches a total sedimentary thickness of more than 110 metres (360 ft). The formation ranges in age from the late Middle Jurassic to the early Early Cretaceous, Oxfordian to Hauterivian stages, with the base of the formation possibly extending into the Callovian.

The Tendaguru Formation is subdivided into six members; from oldest to youngest Lower Dinosaur Member, the Nerinella Member, the Middle Dinosaur Member, Indotrigonia africana Member, the Upper Dinosaur Member, and the Rutitrigonia bornhardti-schwarzi Member. The succession comprises a sequence of sandstones, shales, siltstones, conglomerates with minor oolitic limestones, deposited in an overall shallow marine to coastal plain environment, characterized by tidal, fluvial and lacustrine influence with a tsunami deposit occurring in the Indotrigonia africana Member. The climate of the Late Jurassic and Early Cretaceous was semi-arid with seasonal rainfall and the eustatic sea level was rising in the Late Jurassic from low levels in the Middle Jurassic. Paleogeographical reconstructions show the Tendaguru area was located in the subtropical southern hemisphere during the Late Jurassic.

The Tendaguru Formation is considered the richest Late Jurassic strata in Africa. The formation has provided a wealth of fossils of different groups; early mammaliaforms, several genera of dinosaurs, crocodyliforms, amphibians, fish, invertebrates and flora. More than 250 tonnes (250 long tons; 280 short tons) of material was shipped to Germany during early excavations in the early twentieth century. The faunal assemblage of the Tendaguru is similar to the Morrison Formation of the central-western United States, with an additional marine interbed fauna not present in the Morrison.

The dinosaur fauna found in the formation is similar to that of other highly fossiliferous stratigraphic units of the Late Jurassic; among others the Kimmeridge and Oxford Clays of England, the Sables de Glos, Argiles d'Octeville, Marnes de Bléville of France, the Alcobaça, Guimarota and Lourinhã Formations of Portugal, the Villar del Arzobispo Formation of Spain, the Shishugou, Kalazha and Shangshaximiao Formations in China, the Toqui Formation of Chile and Cañadón Calcáreo Formation of Argentina and the Morrison Formation, with the presence of dinosaurs with similar counterparts, e.g., Brachiosaurus and Stegosaurus in the Morrison, and Giraffatitan and Kentrosaurus in the Tendaguru.

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