What is a characteristic that defines Ornithischia?

Ornithischians are so called because their hip bones were superficially arranged like those of birds in that a large portion of the pubic bone pointed down and toward the tail instead of down and forward as in other reptiles.

What is the difference between saurischians and ornithischians?

Saurischians and ornithischians are the two groups of dinosaur, defined in terms of pelvic structure. Saurischians, whose name means “lizard-hipped,” had a pelvic structure more similar to that of modern lizards, while the ornithischians (“bird-hipped”) had a pelvic structure more like modern birds.

What is the meaning of ornithischian?

Definition of ornithischian : any of an order (Ornithischia) of herbivorous dinosaurs (such as a stegosaurus) that have the pubis of the pelvis rotated backward to a position parallel and close to the ischium — compare saurischian.

What did Ornithischia evolve into?

The meat-eating theropods, which included the famous Tyrannosaurus rex, have evolved into the modern dinosaurs: birds. And the bird-hipped ornithischians, an assorted group of herbivorous dinosaurs, evolved some of the most bizarre anatomy known in evolutionary history.

Is a Stegosaurus a saurischian?

Know Your Ornithischian Dinosaurs. Towering giants such as Tyrannosaurus rex and Apatosaurus are both saurischians, but many plant-eating dinosaurs, including Triceratops and Stegosaurus, are classified as ornithiscians—which means bird-hipped—because their pubis bone was originally thought to resemble that of birds.

What is characteristic of Saurischians?

Saurischians are called lizard-hipped dinosaurs because a special bone in their pelvises tilts in the same way that a lizard’s bones tilt. The fossils of the pelvis have three major bones: the ilium, the ischium, and the pubis. In lizard-hipped dinosaurs, the pubis points forward and downwards and is almost vertical.

What are the two key Synapomorphies of the Ornithischia?

Numbers indicate the acquisition of key ornithischian synapomorphies within the clade: 1, complete loss of recurvature in maxillary and dentary teeth; 2, edentulous anterior end of the dentary; 3, predentary bone at the anterior end of the lower jaw; 4, retroversion of the pubis; 5, rod-like pubic shaft; 6, pubic …

Where did ornithischians live?

Their skulls were triangular and had very large eye sockets. They were herbivorous and would have used agility to escape predators. Fabrosaurids are known from southern Africa in the Upper Triassic and Lower Jurassic, as well as in China from the Middle and Upper Jurassic periods.

Where did Ornithischia live?

What makes something a dinosaur?

Defining Dinosaurs. A more handy general definition would go something like this: Dinosaurs are extinct animals with upright limbs that lived on land during the Mesozoic Era (252 to 66 million years ago). This would basically capture how paleontologists long thought about dinosaurs.

(Show more) Ornithischian, any member of the large taxonomic group of herbivorous dinosaurs comprising Triceratops and all dinosaurs more closely related to it than to birds. The ornithischians (meaning “bird-hipped”) are one of the two major groups of dinosaurs, the other being the saurischians.

What are the characteristics of ornithischian dinosaurs?

Ornithischian. As these teeth came into use, the side with thinner enamel was worn down, so the upper and lower jaws formed an efficient grinding surface. All ornithischians were herbivorous, which made ornithischian dinosaurs the first major group of terrestrial vertebrates to have been dominated by plant eaters.

What are the characteristics of the ornithischian pelvis?

The two most notable traits are a “bird-like” hip and beak-like predentary structure, though they shared other features as well. The ornithischian pelvis was “opisthopubic”, meaning that the pubis pointed down and backwards ( posterior ), parallel with the ischium (Figure 1a).

How many feet did ornithischians walk?

These Ornithischians could walk on either two feet or four. Some Marginocephalians had spikes on their heads to help defends themselves, while others were small and fast in order to evade predators. A famous Marginocephalian is the triceratops.