Pegomastax
| Pegomastax | ||||||||||||
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Holotype of Pegomastax africana : partially preserved skull with jawbone and teeth. The scale bar corresponds to 2 cm. |
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| Temporal occurrence | ||||||||||||
| Lower Jurassic ( Hettangian to Sinemurian ) | ||||||||||||
| 201.3 to 190.8 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Pegomastax | ||||||||||||
| Sereno , 2012 | ||||||||||||
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Pegomastax is a genus of pelvic dinosaur from Lower Jurassic Africa. The only species of the genus, Pegomastax africana , was a small, herbivorous representative of the Heterodontosauridae and lived in what is now South Africa around 200 to 190 million years ago.
The fossil remains of the genus were found in the Elliot Formation , which is approximately 200 to 190 million years old. Species and genus were described by Paul Sereno in 2012 . According to phylogenetic studies, Pegomastax is a relatively derived member of the Heterodontosauridae, it probably forms the sister taxon to the genus Manidens .
features
The surviving fossil material only allows conclusions to be drawn about the head morphology of Pegomastax . It had a rounded keratin beak typical of the Heterodontosauridae , which served as an extension of the upper and lower jaw, as can be ascertained by means of appropriate approaches at the tip of the snout. In its shape it resembled that of today's parrots and was suspended from the jaw so that it could move. The muzzle itself was short and narrow, the lower jaw was wedge-shaped. As with all heterodontids and in contrast to most other dinosaurs, the dentition had different types of teeth ( heterodontics ). The front teeth of P. africana were vampire-like and slightly serrated on the front edge, but unlike other heterodontosaurids, they were not curved backwards. The front teeth were joined by ten diamond-shaped teeth on both sides of the lower jaw, the cutting surfaces of which were serrated.
Other morphological features of P. africana can be speculated partly through the proportions of the skull and partly through comparison with closely related genera. The position in the family tree of the Heterodontosauridae suggests that the jaw muscles started relatively far back on the lower jaw. The tooth row of Pegomastax is 27 mm much shorter than that of the related Heterodontosaurus with 42 mm, which was about 1.2 m long. Since the Heterodontosaur Tianyulong has been handed down in fossil form together with elongated bristle feathers, it is possible that Pegomastax also had similar bristles.
Site, fossil material and stratigraphy
All that has survived from Pegomastax is a severely broken skull in a sandstone block, from which mainly the teeth and parts of the lower jaw could be dissected. The fossil comes from the Elliot Formation near the South African Voyizane ( Eastern Cape ). The formation extends over the chronostratigraphic stages of the Hettangian and Sinemurian (201.3 to 190.8 million years ) and thus comes from the Lower Jura . At that time, the region was still connected to the east coast of today's South America , where the closest known relatives of the genus also lived.
Paleoecology
The wear and tear of the teeth in the jaws of Pegomastax and other heterodontosaurs suggests that all representatives were predominantly or obligatory herbivores , a thesis that is supported by the shape of the keratin beaks. Similar mouth shapes occur in fruit-eating parrots or in herbivorous turtles . The elongated, fang-like front teeth may have served at most for defense or exhibition fights, as they sat too deep in the mouth to serve as effective weapons and showed hardly any wear.
Systematics and taxonomy
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| Systematic position of Pegomastax according to Sereno (2012). The genus is part of the Heterodontosaurinae , an early to middle Jurassic group restricted to West Gondwana . |
The later holotype of Pegomastax ( inventory number SAM -PK-K10488) was already found in 1966/67 during joint excavations by Yale University , the British Museum of Natural History and the University of London . The fossil was dissected at the University of Harvard , where Paul Sereno concluded that it must be a taxon in its own right. However, the fossil remained undescribed for several decades before Sereno placed it in its own genus and species in 2012 .
He chose the generic name Pegomastax based on the Greek combination pegos (German for "strong") and mastax (German for "jaw"). The specific epithet refers to the African location of the holotype. Originally it was africanus , but had to be subsequently corrected from Sereno to africana in order to comply with the rules of nomenclature. Comparisons with well-preserved representatives of the Heterodontosauridae showed Pegomastax as a representative of this group; Phylogenetic analyzes of morphological features showed that the genus is within the Heterodontosaurinae . This group includes heterodontosaurs with a deep suspension of the jaw and is geographically limited to what was then Western Gondwana . It occurs for the first time at the Triassic - Jura border and can be followed with Manidens , the South American sister genus of Pegomastax , as far as the middle Jura.
swell
literature
- Paul C. Sereno : Taxonomy, morphology, masticatory function and phylogeny of heterodontosaurid dinosaurs (= ZooKeys 226, Special Issue ). Pensoft, Sofia 2012, ISBN 978-954-642-652-9 , doi : 10.3897 / zookeys.226.2840 .
- Paul C. Sereno: Corrigenda: Sereno PC (2012) Taxonomy, Morphology, Masticatory Function and Phylogeny of Heterodontosaurid Dinosaurs. ZooKeys 226: 1-225. In: ZooKeys. Vol. 227, 2012, p. 101, doi : 10.3897 / zookeys.227.4091 .
