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hmmm wrote:

Questions (Click to Show Hidden Text)

Are these organisms diapsid,anapsids,synapsids or euryapsids?
1.dinosaurs
2.birds
3.dogs
4.plesiosaurs
5.ichthyosaurs

1. Diapsid
2. Diapsid
3. Synapsid
4. Euryapsid
5. Euryapsid

wec01 wrote:

hmmm wrote:

Questions (Click to Show Hidden Text)

Are these organisms diapsid,anapsids,synapsids or euryapsids?
1.dinosaurs
2.birds
3.dogs
4.plesiosaurs
5.ichthyosaurs

Answers (Click to Show Hidden Text)

1. Diapsid
2. Diapsid
3. Synapsid
4. Euryapsid
5. Euryapsid

wec01 wrote:1. Why are crinoids rarely found as complete fossils?
2.a. What are two major differences between most modern crinoids and most fossil crinoids?
2.b. When and why did this shift happen?
3. What are two morphological commonalities between crinoids and blastoids?

1. The loosely bound ossicles fall apart after death.
2. a. Today most crinoids are either mobile, live in the deep sea, and/or are nocturnal; this was not true in the past.
   b. During the Mesozoic Marine Evolution, a radiation of crinoids caused a radiation of durophagous predators. Crinoids that could not defend or thwart such predators died out and were replaced by mobile ones. Sessile crinoids survived in the deep sea because predators were less common there.
3. Crinoids and blastoids both have pentamerous symmetry. They also both have a stalk attached to a theca.

dchen22 wrote:

wec01 wrote:1. Why are crinoids rarely found as complete fossils?
2.a. What are two major differences between most modern crinoids and most fossil crinoids?
2.b. When and why did this shift happen?
3. What are two morphological commonalities between crinoids and blastoids?

Click to Show Answer

1. The loosely bound ossicles fall apart after death.
2. a. Today most crinoids are either mobile, live in the deep sea, and/or are nocturnal; this was not true in the past.
   b. During the Mesozoic Marine Evolution, a radiation of crinoids caused a radiation of durophagous predators. Crinoids that could not defend or thwart such predators died out and were replaced by mobile ones. Sessile crinoids survived in the deep sea because predators were less common there.
3. Crinoids and blastoids both have pentamerous symmetry. They also both have a stalk attached to a theca.

dchen22 wrote:

Images (Click to Show Hidden Text)

A.
[img]https://assets.catawiki.nl/assets/2018/10/18/f/9/f/f9fd70fa-8f59-49e0-a9ae-f83aad3179a7.jpg[/img]
B.
[img]https://upload.wikimedia.org/wikipedia/commons/thumb/b/b9/Burmirhynchia_jirbaensis_Callovian_Israel.jpg/1200px-Burmirhynchia_jirbaensis_Callovian_Israel.jpg[/img]

1. Identify these two specimens and the material that each specimen is made of.
2. What is an umbo? What is a commissure?
2. Which one of the two taxa is extant?
3. Which one had eyes?

1. Pecten - aragonite, Rhychonellida - calcite
2. Umbo - the bump on the brachial valve, Commisure - the fissure between the two valves
3. Both
4. Pecten

wec01 wrote:

dchen22 wrote:

Images (Click to Show Hidden Text)

A.
[img]https://assets.catawiki.nl/assets/2018/10/18/f/9/f/f9fd70fa-8f59-49e0-a9ae-f83aad3179a7.jpg[/img]
B.
[img]https://upload.wikimedia.org/wikipedia/commons/thumb/b/b9/Burmirhynchia_jirbaensis_Callovian_Israel.jpg/1200px-Burmirhynchia_jirbaensis_Callovian_Israel.jpg[/img]

1. Identify these two specimens and the material that each specimen is made of.
2. What is an umbo? What is a commissure?
2. Which one of the two taxa is extant?
3. Which one had eyes?

Answers (Click to Show Hidden Text)

1. Pecten - aragonite, Rhychonellida - calcite
2. Umbo - the bump on the brachial valve, Commisure - the fissure between the two valves
3. Both
4. Pecten