Term
Ornithischia Background
What did these dinos become highly modified for?
What kind of diet?
Which era? |
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Definition
Ornithischian dinosaurs represent a diverse lineage of highly successful taxa. The
lineage diverged from the ancestral dinosaur and became highly modified for an
herbivorous diet. The ancestral dinosaur, and most other archosaurs for that matter, was
probably a carnivore. Meat is easy to digest and is high in nutritional value, yet
ornithischians adopted a completely herbivorous diet. Keeping these advantages and
disadvantages in mind, consider the kinds of plants early ornithischians had available to
them in the early Mesozoic Era.Ornithischian dinosaurs represent a diverse lineage of highly successful taxa. The
lineage diverged from the ancestral dinosaur and became highly modified for an
herbivorous diet. The ancestral dinosaur, and most other archosaurs for that matter, was
probably a carnivore. Meat is easy to digest and is high in nutritional value, yet
ornithischians adopted a completely herbivorous diet. Keeping these advantages and
disadvantages in mind, consider the kinds of plants early ornithischians had available to
them in the early Mesozoic Era. |
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Term
Ornithischian Diversity
By the Early Jurassic the group had diversifed into what two main linages? |
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Definition
The earliest ornithischian fossils known are Late Triassic in age. By the Early
Jurassic the group had diversified into two main lineages: Heterodontosauridae and
Genasauria. Heterodontosauridae is a group of primitive ornithischians with
heterodont dentition. This type of dentition, where different regions of teeth in the skull
are specialized for specific functions, is unique among ornithischians and has contributed
to uncertainty about the group’s phylogenetic position. Genasauria is a group containing
Thyreophora and Cerapoda, and it is characterized by expanded crowns of their
premaxillary teeth.
Thyreophora is characterized by extensive osteoderms set in the skin on the
body. The earliest member of this group is Scelidosaurus, a small animal known from
Early Jurassic rocks of Arizona. Scelidoosaurus had numerous small osteoderms
adorning its sides, back, and neck. From an ancestor similar to Scelidosaurus, the two
main thyreophoran lines developed, Stegosauria and Anklyosauria.
Stegosaurs are among the most publicly recognized dinosaurs. Instead of
scattered, circular osteoderms found on primitive thyreophorans, the osteoderms are
aligned in a double row along the back of the animal. Different taxa of stegosaurs have
various combinations of flattened plates or large spikes along the back. Many also have
some arrangement of spines near the tip of the tail. The fossil record of stegosaurs is
most diverse during the Jurassic, but the group declined and finally went extinct in the
Cretaceous. |
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Term
Conifers
Cyads
Angiospers |
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Definition
Conifers are familiar to most of us. They include pines, spruces, junipers, and
their kin. Conifers are characterized by having very narrow, reduced leaves with a thick
waxy outer layer called a cuticle. We commonly refer to these tough, narrow leaves as
needles, and they probably evolved to withstand dry, windy, or cold environments.
Conifers reproduce using cones that dangle from the tips of branches. Today there are
approximately 300-400 species of conifer, and they are most diverse in relatively cooler
or higher altitude environments.
In the Mesozoic, cycads were abundant, but they have declined in diversity and
range since then. Now they are mainly restricted to the tropics and subtropics. Cycads
also reproduce with cones, but the cones are nestled in the center of the plant with large
frond-like leaves radiating outward from the central hub. Each cycad plant is either male
or female, unlike conifers. A few species of cycads are hardy enough to withstand the
climate of southern North America and are used as ornamental plants.
The first angiosperms appeared in either the latest part of the Jurassic or the
Early Cretaceous. Angiosperms differ from their gymnosperm cousins in that they
reproduce with flowers, and the seed is usually enclosed or covered by some sort of
fleshy layer, or fruit. Angiosperms quickly spread across the globe during the Cretaceous
and became the dominant type of terrestrial plant on Earth. There are thousands of
species alive today, and there is a long fossil record for some groups. |
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Term
Cladogram - Ornithischian
First diagnal |
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Definition
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Term
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Definition
1. In-turned femoral head
2. Opposable thumb
3. Perforate acetabulum
4. S-shaped neck |
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Definition
5. Characteristic pelvis with back-turned pubis
6. Predentary bone in lower jaw
7. Ossified tendons along part of vertebral column
8. Teeth inset from margin of jaws (indicating the presence of muscular cheeks) |
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Definition
| 9. Expanded crown in premaxillary teeth |
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Term
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Definition
| Asymmetrical distribution of tooth enamel |
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Term
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Definition
| 11. Expanded shelf at back of skull |
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Term
| Ceratopsia (upper most right) |
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Definition
| Rostral bone present on upper jaw to form sharp beak |
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Term
| ***Start of the top horizontal latter going across |
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Definition
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Term
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Definition
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Term
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Definition
| 13. Laqrge, spike-like caniniform tooth in dentary bone |
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Term
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Definition
17. Scutes form interlocking mosaic that covers most of body
***NEXT Clade goes vertical downwards |
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Term
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Definition
16. The anterior portion of the ilium is much longer than the posterior portion
***Next card goes vertical downwards |
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Definition
14. Armor made of bony scutes that cover back and/or flanks
15. Tibia shorter than femur
***Next card braches off of "Eurypoda", then the following off of "Threophora |
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Definition
18. Scutes enlarged to form two rows of large plates extending along vertical column
***Next card is next to "Steogosauria" along the top but branches off of "Thyreophora" |
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Term
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Definition
none
***The next card is next to "Scelidosaurus" along the top but branches off from "Cerapoda" on the original horizontal bar |
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Term
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Definition
| 19. Articulation of skull and jaw well below the level of the tooth row |
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Term
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Definition
20. Skull roof greatly thickened to form solid "dome" that is usually surrounded by various bumps and tubercles
21. Occipital plate roatated beneath skull
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