Assignment 4 (1)
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GEOL 110 Dinosaurs and Their World
NAME: ______________________________
Homework #4
IDENTIFYING DINOSAURS
Background:
When a paleontologist discovers a new bone or skeleton, they determine
which clade it belongs to by examining it for the presence of synapomorphies
, shared derived characters owing to common descent. Synapomorphies are used to diagnose dinosaur clades, and they can be used to identify which clade a fossil most likely belongs to. Note the use of the words "most likely" in the previous sentence - this is because it is possible for the same derived character to evolve twice (or more) in separate lineages, termed homoplasy
. However, recognition of synapomorphies present in the morphology of a fossil bone or skeleton provide an initial estimate of what kind of animal you have likely discovered. *Note* - Also remember that a particular fossil may not preserve every synapomorphy
of the clade to which the animal belongs, usually due to some bones being preserved and others not, or due to taphonomic damage. For example, if all you find of your new dinosaur is its skull, you may still be able to tell which clade your dinosaur most likely belongs to based on synapomorphies preserved in its skull.
INSTRUCTIONS:
⮚
Over the last two weeks we have discussed all of the major clades of herbivorous (plant eating) dinosaurs, namely Ornithopoda, Thyreophora, Marginocephalia, and Sauropodomorpha, including synapomorphies used to diagnose each clade. You will now apply that information to identify dinosaur fossils to clades and "sub"-clades. Read carefully
through the example on Page 2, then use your notes from class to answer the questions on the following pages.
EXAMPLE
:
Imagine you are a dinosaur paleontologist, you found a new partial skeleton, and you worked with a paleoartist to create the skeletal drawing of it shown below: ⮚
Dinosaurs initially split into the clades Ornithischia and Saurischia. You know your dinosaur is a saurischian
dinosaur because its pubis only has one projection pointing anteriorly (no second, posterior-pointing projection as in ornithischian dinosaurs).
⮚
Among saurischian dinosaurs, you know it is a sauropodomorph
because it has more than 10 cervical vertebrae and they are elongated compared to the rest of its vertebrae. ⮚
Among sauropodomorph dinosaurs, you know it is a sauropod
because it has more than 11 cervical vertebrae (your dinosaur has 13 cervicals).
⮚
Among sauropod dinosaurs, you do NOT
know
if it is a neosauropod
because synapomorphies diagnosing that clade are in the hand and teeth, and
your specimen does not preserve either a hand or a tooth.
⮚
Among sauropod dinosaurs, you do NOT
know
if it is a diplodocoid
because synapomorphies diagnosing that clade are in the skull and tail, and your specimen does not preserve either the skull or tail.
⮚
Among sauropod dinosaurs, you do NOT
know
if it is a titanosauriform
because synapomorphies diagnosing that clade are in the femur, which is not
preserved, and the internal structure of the vertebrae, which you have not yet
examined. ?
YOUR END CONCLUSION / FINEST SCALE DIAGNOSIS: My dinosaur is a Sauropod
WAIT - that looks like a sauropod dinosaur
! How did you determine what kind of dinosaur your new find was? (Or from the paleoartist's perspective, how did you determine what the rest of the animal's silhouette in black should look like?):
QUESTIONS:
1) Imagine you found a new partial dinosaur skeleton, and you worked with a paleoartist to create the skeletal drawing of it shown below:
Is your dinosaur a member of Ornithischia or Saurischia? What synapomorphy(s) lead you to
this conclusion? This dinosaur is most likely to be a member of the ornithischia. The bird shaped structure of the pelvis and the extra bone at the trop of the jaw are the synapomorphies that helped me determine this. Is your dinosaur a member of the clade Ornithopoda, Thyreophora, Marginocephalia, or Sauropodomorpha? What synapomorphy(s) lead you to this conclusion?
This dinosaur is a member of the clade ornithopoda because of the way the structure of his feet are. He has bird-like feet. He also has a extra bone at the tip of the lower jaw, toothless horn-
like beak helps indicates this. 2) Imagine you found a new partial dinosaur skull, and you worked with a paleoartist to create the skeletal drawing of it shown below:
Zoom in:
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Is your dinosaur a member of the clade Ornithopoda, Thyreophora, Marginocephalia, or Sauropodomorpha? What synapomorphy(s) lead you to this conclusion?
I would say that this dinosaur is a part of the clade Ornithopoda family. The large single horn that
comes from the top of the nose helped me make this decision. It also has 2 projecting spikes in reverse and 2 forward bending snares. Within the clade you chose above, diagnose your dinosaur to as small (least inclusive) of a clade as possible, and explain what synapomorphy(s) lead you to your conclusion:
Orthopods are described as having no shield and the improvement of a horny snout and a missing
opening in the lower jaw. 3) Imagine you found the tail of a new dinosaur skeleton preserved in a block of sandstone, photographed below (dark areas = bone, light areas = sandstone):
Does your specimen preserve a synapomorphy allowing you to diagnose it? If yes, what is this feature and
which clade does it belong to? If not, why not?
The tails in Anklosaurs have club tails that were used as a biological weapon which is the most recognizable feature of an ankylosaurus. posterior anterior
4) Imagine you found a new complete dinosaur skeleton, and you worked with a paleoartist to create the skeletal drawing of it shown below:
Is your dinosaur a member of the clade Ornithopoda, Thyreophora, Marginocephalia, or Sauropodomorpha? What synapomorphy(s) lead you to this conclusion?
This dinosaur is a member of the clade marginocephalia. The bone extending back over the occupational region of the skull helped me determine this. Within the clade you chose above, diagnose your dinosaur to as small (least inclusive) of a clade as possible, and explain what synapomorphy(s) lead you to this conclusion:
5) Imagine you found a new partial dinosaur skeleton, and you worked with a paleoartist to create the skeletal drawing of it shown below:
Is your dinosaur a member of Ornithischia or Saurischia? What synapomorphy(s) lead you to
this conclusion? This dinosaur is an ornithischia. The forward facing ilium and the pubis pointing down in a backward direction help determine that it is an ornithischian. Is your dinosaur a member of the clade Ornithopoda, Thyreophora, Marginocephalia, or Sauropodomorpha? What synapomorphy(s) lead you to this conclusion?
This dinosaur is a thyreophora. The plates on its back and the spike on the tail help determine this. Within the clade you chose above, diagnose your dinosaur to as small (least inclusive) of a clade as possible, and explain what synapomorphy(s) lead you to this conclusion:
6) Consider the skeletal drawing of the titanosauriform sauropod Puertasaurus
below:
How did the paleontologists who discovered these 4 bones discern that they belong to a titanosauriform sauropod dinosaur? Or, in other words, what synapomorphies must be Puertasaurus reuli
Titanosauriform sauropod
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present among these vertebrae (hint: there are three synapomorphies, and you cannot see one of them in the drawing above)?