Tazoudasaurus

Tazoudasaurus
Representative cervical, back and tail vertebrae of Tazoudasaurus .
Temporal occurrence
Lower Jurassic ( Toarcium )
182.7 to 174.1 million years
Locations
Ouarzazate , Morocco ( Toundoute continental series )
Systematics
Dinosaur (dinosauria) Lizard dinosaur (Saurischia) Sauropodomorpha Sauropods (Sauropoda) Tazoudasaurus
Scientific name
Tazoudasaurus
Allain et al., 2004
Art
Tazoudasaurus naimi

Tazoudasaurus is a genus of sauropod dinosaur , the remains of which were discovered in the High Atlas of Morocco and are dated to the Lower Jurassic ( Toarcium ).

Tazoudasaurus is one of the most original known sauropods, its skeleton shows a mosaic of advanced features, as they are typical for sauropods, and original features, as they are found in the ancestors of the sauropods (original sauropodomorpha or "prosauropods"). Tazoudasaurus is the most completely transmitted, very original sauropod and is therefore of great importance for understanding the early evolution of this group. The only species is Tazoudasaurus naimi .

Tazoudasaurus is named after one of the places where it was found, Tazouda, while the epithet naimi comes from the Arabic language and means something like "slim" - this is to indicate the comparatively small body size of the animal.

features

As with all sauropods, it was a herbivore with a long neck and tail. Unlike the two-legged precursors of the sauropods, Tazoudasaurus was already four-legged, like all sauropods. Tazoudasaurus was a relatively small sauropod. Adult animals reached a length of 9.5 to 10 meters and an estimated weight of 8 tons, one of the young animals found, however, is reconstructed to a weight of 140 kilograms. The skull is reconstructed to a length of 32 centimeters.

The skeleton shows typical sauropod features as well as original features that were characteristic of the ancestors of the sauropods (original sauropodomorpha ), but have been lost in more advanced sauropods. The lower jaws were set with 18 D-shaped teeth on each side, which did not overlap one another. The rows of teeth were straight and converged in a V-shape when viewed from above, the muzzle was only slightly rounded. In contrast, advanced sauropods had shorter rows of teeth with fewer teeth, but which overlapped one another; also the rows of teeth, viewed from above, were U-shaped, and not V-shaped as in Tazoudasaurus . Signs of wear and tear caused by direct contact with the teeth of the upper jaw suggest that the food was processed orally before swallowing.

In the early evolution of the sauropods, a far-reaching remodeling of the hand skeleton took place. The original building plan was characterized by splayed hand rays with fully developed finger bones; in advanced sauropods, on the other hand, the fingers were greatly reduced, and the rays of the metacarpal were not splayed, but were close together and formed a semicircle. Tazoudasaurus is the first to be discovered original sauropod known to have a complete hand skeleton, and clarifies the long-debated question of when the specialized hand skeleton of the more advanced sauropods evolved. Tazoudasaurus showed only three phalanges in the second finger and two in the third finger - fewer than in the original Sauropodomorpha. The hand skeleton, however, followed the splayed, original blueprint, which confirms the hypothesis that the specialized blueprint of the advanced sauropods first appeared in the original representatives of the neosauropods . The foot of Tazoudasaurus also showed original features, so the foot bones were still relatively long.

Finds and research history

The Tazoudasaurus fossils were discovered by an international team of researchers near the village of Toundoute in the Moroccan province of Ouarzazate as part of the "Dinoatlas project" launched in 1999 . By 2010, the remains of at least 10 specimens could be recovered, which is why most of the skeleton is known today. However, parts of the spine and most of the facial skull are missing. The finds belong to both adults and young animals and come from six sites close together. One of these sites contained the Tazoudasaurus fossils and the remains of the ceratosaur Berberosaurus . Most of the fossils are now archived in the collection of the Musée des Sciences de la Terre in Rabat .

In 2004, Tazoudasaurus was scientifically described for the first time by researchers around Ronan Allain . The description was based on two fragmentary skeletons, some of which were found in the anatomical skeletal system: The holotype specimen includes both skull and bone remains of a partial skeleton of an adult animal, as well as the skeleton of a young animal. In 2008 an extensive anatomical description followed, taking into account further, newly discovered specimens. A reconstruction of the skeleton was published in a third publication published in 2010.

Morocco is relatively rich in remains of early sauropods, which are very rare worldwide. The sauropods "Cetiosaurus" mogrebiensis and Atlasaurus imelakei were also found in the mountains of the High Atlas . Similar old sauropods are unknown from North America; Since the separation of Africa and America only began in the Middle Jurassic, North America was probably home to the same fauna.

Cladogram , simplified from Allain and Aquesbi (2008)
Sauropoda     Vulcanodontidae   Vulcanodon      Tazoudasaurus   Eusauropoda   Shunosaurus        Omeisaurus      Neosauropoda
Systematic position of Tazoudasaurus

Systematics

The closest known relative of Tazoudasaurus is the contemporary Vulcanodon , both genera differ only in features on the vertebrae. Tazoudasaurus displays a number of features previously known only from Vulcanodon . In order to underpin the similarity with Vulcanodon and to distinguish it from other primitive sauropods such as Barapasaurus , the first descriptors put Tazoudasaurus together with Vulcanodon in the family Vulcanodontidae , which forms the sister group of the Eusauropoda . The Vulcanodontidae (Cooper, 1984) originally included the species Vulcanodon and Barapasaurus as well as later other basal sauropods, but with this definition it is no longer recognized by most researchers, since Barapasaurus is now classified as a Eusauropod - this would make the Vulcanodontidae paraphyletic . The first descriptors of Tazoudasaurus redefined the Vulcanodontidae as a group that includes all species more closely related to Vulcanodon than to Eusauropods; this definition excludes Barapasaurus from this group. The new definition has not been widely accepted; in more recent analyzes (e.g. in Wilson, 2005) the Vulcanodontidae is mostly not used.

Taphonomy and behavior

The Tazoudasaurus fossils come from two very bone-rich layers - so-called bonebeds - which are stratigraphically separated from each other by a 30-meter- thick sediment sequence. Both bonebeds are interpreted as debris flows, meaning that they are deposited within a very short time by mud flows flowing down into the valley. Most of the specimens come from the upper bonebed, while only 2 specimens have been recovered from the lower one. The researchers suspect that at least the animals of the upper bonebed were buried by the debris flow and thus perished. If this interpretation is correct, it would indicate a life in groups, which consisted of both adult and very young animals. Together with the two Tazoudasaurus specimens of the lower bonebed, the remains of the ceratosaur Berberosaurus , which may have hunted the sauropods, were found.

literature

• Ronan Allain, Najat Aquesbi, Jean Dejax, Christian Meyer, Michel Monbaron, Christian Montenat, Philippe Richir, Mohammed Rochdy, Dale Russell, Philippe Taquet: A basal sauropod dinosaur from the Early Jurassic of Morocco . In: Comptes Rendus Palevol . tape 3 , no. 3 , April 2004, p. 199–208 , doi : 10.1016 / j.crpv.2004.03.001 ( PDF ).
• Ronan Allain, Najat Aquesbi: Anatomy and phylogenetic relationships of Tazoudasaurus naimi (Dinosauria, Sauropoda) from the late Early Jurassic of Morocco . In: Geodiversitas . tape 30 , no. 2 , 2008, p. 345-424 ( [6] ).
• Karin Peyer, Ronan Allain: A reconstruction of Tazoudasaurus naimi (Dinosauria, Sauropoda) from the late Early Jurassic of Morocco . In: Historical Biology . tape 22 , no. 1–3 , 2010, pp. 134-141 , doi : 10.1080 / 08912960903562317 .

Individual evidence

1. ^ Gregory S. Paul: The Princeton Field Guide To Dinosaurs , 2010. ISBN 978-0-691-13720-9 , p. 172 online
2. ↑ ^{a b} Ronan Allain, Najat Aquesbi, Jean Dejax, Christian Meyer, Michel Monbaron, Christian MONTENAT, Philippe Richir, Mohammed Rochdy, Dale Russell, Philippe Taquet: A basal sauropod dinosaur from the Early Jurassic of Morocco . In: Comptes Rendus Palevol . tape 3 , no. 3 , April 2004, Systematic Palaeontology Section , p. 3–7 , doi : 10.1016 / j.crpv.2004.03.001 ( PDF ).
3. ↑ ^{a b c d e} Ronan Allain, Najat Aquesbi, Jean Dejax, Christian Meyer, Michel Monbaron, Christian Montenat, Philippe Richir, Mohammed Rochdy, Dale Russell, Philippe Taquet: A basal sauropod dinosaur from the Early Jurassic of Morocco . In: Comptes Rendus Palevol . tape 3 , no. 3 , April 2004, section Discussion , p. 206-207 , doi : 10.1016 / j.crpv.2004.03.001 ( PDF ).
4. ^ ^{A b} Karin Peyer, Ronan Allain: A reconstruction of Tazoudasaurus naimi (Dinosauria, Sauropoda) from the late Early Jurassic of Morocco . In: Historical Biology . tape 22 , no. 1-3 , 2010, section Reconstruction , pp. 2-4 , doi : 10.1080 / 08912960903562317 .
5. ^ Karin Peyer, Ronan Allain: A reconstruction of Tazoudasaurus naimi (Dinosauria, Sauropoda) from the late Early Jurassic of Morocco . In: Historical Biology . tape 22 , no. 1-3 , 2010, section Description , p. 4-8 , doi : 10.1080 / 08912960903562317 .
6. ^ Ronan Allain, Najat Aquesbi: Anatomy and phylogenetic relationships of Tazoudasaurus naimi (Dinosauria, Sauropoda) from the late Early Jurassic of Morocco . In: Geodiversitas . tape 30 , no. 2 , section Forefoot posture in basal Sauropods , p. 406-408 ( [1] ).
7. ^ Ronan Allain, Najat Aquesbi: Anatomy and phylogenetic relationships of Tazoudasaurus naimi (Dinosauria, Sauropoda) from the late Early Jurassic of Morocco . In: Geodiversitas . tape 30 , no. 2 , section Introduction , p. 346-349 ( [2] ).
8. ^ Karin Peyer, Ronan Allain: A reconstruction of Tazoudasaurus naimi (Dinosauria, Sauropoda) from the late Early Jurassic of Morocco . In: Historical Biology . tape 22 , no. 1-3 , 2010, section Specimen examined ; Table 1, p. 1, 3 , doi : 10.1080 / 08912960903562317 .
9. ↑ Ronan Allain, Najat Aquesbi, Jean Dejax, Christian Meyer, Michel Monbaron, Christian Montenat, Philippe Richir, Mohammed Rochdy, Dale Russell, Philippe Taquet: A basal sauropod dinosaur from the Early Jurassic of Morocco . In: Comptes Rendus Palevol . tape 3 , no. 3 , April 2004, section Introduction , p. 200 , doi : 10.1016 / j.crpv.2004.03.001 ( PDF ).
10. ^ Ronan Allain, Najat Aquesbi: Anatomy and phylogenetic relationships of Tazoudasaurus naimi (Dinosauria, Sauropoda) from the late Early Jurassic of Morocco . In: Geodiversitas . tape 30 , no. 2 , section Fig. 46 , p. 411 ( [3] ).
11. ↑ Jeffrey A. Wilson: Integrating ichnofossil and body fossil records to estimate locomotor posture and spatiotemporal distribution of early sauropod dinosaurs: a stratocladistic approach . In: Paleobiology . tape 31 , no. 3 , May 20, 2005, pp. 400-423 , doi : 10.1666 / 0094-8373 (2005) 031 [0400: IIABFR] 2.0.CO; 2 ( [4] ).
12. ^ Ronan Allain, Najat Aquesbi: Anatomy and phylogenetic relationships of Tazoudasaurus naimi (Dinosauria, Sauropoda) from the late Early Jurassic of Morocco . In: Geodiversitas . tape 30 , no. 2 , section Taphonomy and inferred behavior of Tazoudasaurus , p. 405 ( [5] ).