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Re: Needing Dinosaur Info
One source of information on Dinosaurs (and other extinct
vertebrates) is the Macmillan Illustrated Encyclopedia of Dinosaurs and
Prehistoric Animals. It is somewhat technical in terminology, but clearly
written and not difficult to understand. The information is up to date
and represents contemporary theory.
As for Nothosaurus:
The Nothosauria are a clade, or group of similar animals, that
are early relatives of plesiosaurs (but not direct ancestors). They are
not dinosaurs and existed before the dinosaurs dominated the land. They
are characterized by long necks and tails and lived for the most part in
water. Nothosaurs had webbed feet instead of flippers and may have lived
much like modern seals and sealions.
Nothosaurus is a typical nothosaur and is the namesake for the
clade. It wasn't well adapted to aquatic life but had five long toes on
each foot with webbing in between and may have had a fin running down the
length of the back and tail. The backbone wasn't stiff like a plesiosaur
so it probably swam by undulating its body from side to side and paddling
with it's feet. The teeth were long and sharp for its diet of fish.
If you (or your students) are wondering why this animal isn't a
dinosaur the answer has to do with the arrangement of the temporal
openings in the skull (the temples). Vertebrates have been grouped
together based on the number and arrangement of these openings.
Mammals and their ancestors have a single opening behind the eye
sockets. This is called a Synapsid arrangement.
Archosaurs (dinosaurs, pterosaurs, and crocodiles) have two
openings behind the eyes, one on top of the other. This is called
Diapsid. Modern lizards, snakes and birds have modified diapsid skulls.
The aquatic reptiles (plesiosaurs, nothosaurs, sphenacodonts, and
icthyosaurs) had just one opening above and behind the eye socket that
corresponds to the upper opening in diapsids. This is called Euryapsid.
Turtles, amphibians, and most fish have no openings other that
the eyes and nostrils and that is called Anapsid.
Scientists aren't entirely certain what the purpose of the
openings is, or why their arrangement is so important, but current theory
is that it allows for a lighter skull, more room in the braincase, and
better attaching points for the jaw muscles.
I hope this is what you were looking for. All of this information (and a
lot more) is in the book mentioned above. Good luck on the project.