Cranial Skeleton of Tetrapods

Question 1

Eusthenopteron

Answer 1

• Early sarcopterygian fish closely related to tetrapods
• Considered transitional between fish and tetrapods

Question 2

What feature of the nose is shared between Eusthenopteron and tetrapods?

Answer 2

• Nasal openings on their skull allowing them to breathe air
• A critical adaptation for transitions from aquatic to terrestrial environments
• This connects early fish to tetrapods

Question 3

What major changes occurred in skull structure associated with the transition from water to land? What is their functional significance?

Answer 3

• Loss of connection of skull to pectoral girdle (Neck)
• A neck increases mobility
• Loss of operculum
• Not needed for air breathing on land
• Relative lengthening of snout
• improves ability to feed effectively

Question 4

How does Tiktaalik fit into this?

Answer 4

• An example of the first fish to transition from water to land seen in the fossil record.

Question 5

Syanpids

Answer 5

• Mammals
• One hole in the head

All mammals are synapsids but not all synapsids are mammals. Probainognathus is a synapid but not a mammal.

Question 6

Diapsid

Answer 6

• Modern reptiles
• Two holes in the head

Question 7

Anapsid

Answer 7

• No holes in the head
• Extinct reptiles
• Sea turtles, but are thought to have derived from diapsids