Pelvic dinosaur

Pelvic dinosaur
Basin region of Edmontosaurus , a hadrosaurid ornithic animal
Temporal occurrence
Upper Triassic ( Carnian ) to Upper Cretaceous
228 to 65.5 million years
Locations
worldwide
Systematics
Sauropsida Diapsida Archosauria Ornithodira Dinosaur (dinosauria) Pelvic dinosaur
Scientific name
Ornithischia
Seeley , 1887

The bird pelvic dinosaurs (Ornithischia) are one of the two orders of the dinosaurs next to the lizard dinosaurs (Saurischia) .

This differentiation of the dinosaurs was a big step towards a better understanding of their relationship and was made in 1887 by Harry Govier Seeley of King's College London . By then, some well-preserved dinosaur skeletons had been described and Seeley noticed that they could be divided into two groups based on their pelvic anatomy . Seeley named these two groups Saurischia and Ornithischia.

features

Pelvic anatomy of bird pelvic dinosaurs (simplified model )

Rough systematics of the dinosaurs with comparison of the pelvic anatomy of the lizard and the bird pelvic dinosaur

Stegosaurus , live reconstruction

The arrangement of the pelvic bones of the bird pelvic dinosaurs is similar to that of the birds, which led Seeley to choose this name. However, the birds are pelvis dinosaurs, the anatomical similarity is only superficial. While ischial (ischium) and iliac (Ilium) are arranged in the orientation as in the lizard Beck dinosaurs showing pubis (pubic) is not down and slightly forward to the head, but consists of a narrow, rod-shaped bone, the longitudinally adjacent the ischium lies and points backwards. The ilium, ischium and pubis thus form a two-ray structure, whereas the pelvis of the Saurischiern has three rays. In some bird pelvic dinosaurs - especially those from the Upper Cretaceous such as the Ceratopsia or the Ankylosauria - the pelvis deviates from this structure. The pubic bone is shortened and forms a new, forward-facing bone process, the prepubis ; however, the basic structure remains recognizable.

The cause of the "turned back" pubis is unclear, since there is no fossil evidence for the early phase of development. An explanation based solely on the bipedal (two-legged) way of life contradicts the fact that this feature is absent in similarly living Saurischia such as Coelophysis and on the other hand, for example, in the Hypsilophodontidae , which belong to the Ornithischia, due to the development of a distinctive prepubic process towards the front, an alignment the Saurischia basin structure took place. Would be possible for the data needed for forward movement of the thigh muscles to other bones instead of the pubis anneal so that it re-formed or could be moved back to the thigh to gain more freedom and more space are important for the plant for digestion food tract to accomplish. Another reason may have been the more advantageous position of the center of gravity for these often bipedal dinosaurs.

In addition to the different pelvic bones, this group has other peculiarities that do not occur in the pelvic lizard. All pelvic dinosaurs had a bone on the tip of their lower jaw, the predentale . The rows of elongated vertebral processes, which probably helped to tighten and support the back, are somewhat less prominent. Unlike the pelvis dinosaurs, the pelvic dinosaurs were pure herbivores with a significantly greater diversity of species .

External system

The following important information is missing from this article or section:

This system overturns the current state of knowledge and cannot stand alone and in isolation in the otherwise unchanged article - see discussion: Vogelbeckensaurier # Systematics from 2017 is unsuitable on its own . - KnightMove ( discussion ) 3:40 pm , Feb 28, 2020 (CET)

Help Wikipedia by researching and pasting it .

In a detailed phylogenetic study from 2017, based on 74 taxa and 457 traits, the paleontologists Matthew G. Baron , David B. Norman and Paul M. Barrett propose a radically new systematics. Accordingly, Ornithischia and Theropoda are combined as sister groups in the clade Ornithoscelida , while the Sauropodomorpha together with the Herrerasauridae form the newly defined clade Saurischia. The dinosaurs thus consist of the two clades Saurischia and Ornithoscelida:

Dinosauria	Saurischia    Herrerasauridae      Sauropodomorpha   Ornithoscelida    Ornithischia      Theropoda

Internal system

The following cladogram shows the relationships between the main groups within the Ornithischia:

Ornithischia	Pisanosaurus      Heterodontosauridae   Genasauria     Thyreophora    Stegosauria      Ankylosauria   Neornithischia    Stormbergia      Hexinlusaurus      Agilisaurus   Cerapoda    Ornithopoda   Marginocephalia    Pachycephalosauria      Ceratopsia

Web links

Commons : Ornithischia  - Collection of images, videos and audio files

• Ornithischia near Palaeos

Individual evidence

1. ^ Harry G. Seeley : The classification of the Dinosauria. In: Report of the Fifty-Seventh Meeting of the British Association for the Advancement of Science held at Manchester in August and September 1887. ISSN  0262-690X , pp. 698-699, digitized .
2. ^ Robert L. Carroll : Paleontology and Evolution of the Vertebrates. Thiemig, Stuttgart et al. 1993, ISBN 3-13-774401-6 , p. 319, fig. 14-28.
3. ^ Robert L. Carroll: Paleontology and Evolution of the Vertebrates. Thiemig, Stuttgart et al. 1993, ISBN 3-13-774401-6 , p. 316.
4. ^ K Padian: Palaeontology: Dividing the dinosaurs . In: Nature . 543, 2017, pp. 494-495. PMID 28332523 .
5. ^ MG Baron, Norman DB, Barrett PM: A new hypothesis of dinosaur relationships and early dinosaur evolution . In: Nature . 543, 2017, pp. 501-506. PMID 28332513 .
6. ^ Richard J. Butler, Paul Upchurch , David B. Norman : The phylogeny of the ornithischian dinosaurs. In: Journal of Systematic Palaeontology. Vol. 6, No. 1, 2008, ISSN  1477-2019 , pp. 1-40, doi : 10.1017 / S1477201907002271 .