Saurischia
From Palaeos
| DINOSAURIA (The Dinosaurs) | |
| Taxonomy | Phylogeny (some taxa are of uncertain relationship and hence mentioned twice) |
Class: Reptilia/Sauropsida
|
o Dinosauromorpha `--o DINOSAURIA |--Ornithischia `--o Saurischia |?-Eoraptor |?-Guaibasaurus |?-Herrerasauria `--+--Sauropodomorpha `--o Theropoda |?-Eoraptor `--+?-Herrerasauria `--+?-Guaibasaurus `--Neotheropoda / Avepoda (= Theropoda?) |
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Contents |
Introduction
The Saurischia or "lizard hipped" dinosaurs are conventionally divided in turn into two groups, one carnivorous, the other herbivorous. The first of these are the Theropoda, the bipedal carnivorous dinosaurs, with their bird-like legs and necks. Theropoda means "beast-feet", a rather inappropriate name; "bird(-like) feet" would have been better. Included in this huge and diverse group are both small forms (among them the ancestors of birds) and large predators such as Allosaurus and Tyrannosaurus.
The other group of Saurischia, the Sauropodomorpha, are the herbivores. There are two main subgroups, the Sauropoda (the inappropriately named "lizard-feet"), and their ancestors, the Prosauropoda ("before the sauropods". Although the primitive prosauropods were relatively small, the more advanced types, and especially all of the sauropods, were elephantine giants with tiny heads, very long necks and tails, massive bodies, and pillar-like legs. This group includes the famous Apatosaurus and its relatives. Like modern-day elephants, they relied on their great size as a defense against carnivores.
Information
Saurischia: All dinosaurs closer to birds than to Triceratops.
Range: from Middle Triassic.
Phylogeny: Dinosauria: Ornithischia + *: Sauropodomorpha + Theropoda.
Characters
- No contact between maxillary process of premaxilla and nares;
- $ Subnarial foramen;
- Antorbital fenestrae;
- $ Forked post process of jugal;
- $ Jugal overlaps laterally onto lacrimal;
- Temporal musculature extends into frontals;
- Neck elongated and S-shaped;
- Posterior cervical vertebrae elongated;
- $ Axial postzygapophyses lateral to prezygapophyses;
- Trunk vertebrae have accessory articulations;
- Enlarged manus I; metacarpal I short, robust, and has 2 asymmetrical distal condyles so that digit is set off at an angle (the "grasping hand");
- Manus III longest (hand characters would exclude Herrerasauridae);
- $ Ischium with rod-like shaft;
- Pubis points forward (propubic);
- Wedge-shaped ascending process of astragalus.
Links
Credits
Palaeos com ATW010708. This page MAK061024
