Mesozoic Marine Reptiles (final exam)

Question 1

What kind of fish were prevalent in Mesozoic?

Answer 1

• bony fish (Osteichthyes) were abundant
• mostly ray-finned fishes (dominant today)
• only a few lobe-finned fish survived into Mesozoic

Question 2

What’s the debate about turtles on the phylogenetic chart of evolution?

Answer 2

Inconsistencies about where we put them on the chart
> do they evolve straight from the stem reptiles or do they evolve later from the archosaurs

Question 3

Explain the significance of sea turtles > and what are their characteristics?

Answer 3

• they are the only fully marine reptiles that are left today
• shell is fused to vertebrae and ribs - which are outside of their shoulder blades (only animals whose shoulder blades are inside their ribs)
• swim primarily with front flippers
• no teeth - beak only
• lay eggs on land

Question 4

What are the important characteristics of Ichthyosaurs?

Answer 4

• order of large extinct marine reptiles (known as the fish lizard)
• streamlined shape
• 0.7-15m long (very diverse in size)
• tail for propulsion > flippers for maneuvering
• numerous sharp teeth > ate fish, cephalopods
• live birth > eggs kept within females

Question 5

Explain the main Plesiosaurs characteristics

Answer 5

• short and long necked
  > short: possibly bottom feeders
  > long: caught fish
• 3.6 - 15m long
• probably live birth, possible they laid eggs on land?

Question 6

What are the 2 super families of Plesiosaurs and the what is in each family?

Answer 6

1. Plesiosauroidea > eaters of little things
   > Elasmosauridae (long neck, short face)
   > Polycotylidae (short neck, long face)
   > Leptocleididae (short neck, short face)
2. Pliosauroidea > eaters of everybody
   > Thomaleosauridae (long neck, long face)
   > Pliosauridae (short neck, long face)

Question 7

Explain the Mosasaur group (time period, main characteristics, diet)

Answer 7

• late Cretaceous
• 2.5-9m long (but highest estimate about 15m)
• fully aquatic
• closely related to snakes and monitor lizards
• limbs resemble paddles > maneuvering
• tail for propulsion
• ate fish, birds, ammonoids, smaller reptiles, etc.

Question 8

What is the world’s largest mosasaur on display?

Answer 8

Bruce > in the Morden Canadian Fossil Discovery Centre

Question 9

Explain the studies/debate around the behaviour of Mosasaurs?

Answer 9

Many scars and mutilations are found on their skulls > were they overly aggressive and pugnacious?
- look at the behaviour of animals they’re related to (lizards and snakes)
- lizards head butt during sex > females dying shortly after getting pregnant
- snakes don’t do that
- evidence of face biting > maybe this is an escalation of conflict more than initial conflict itself
- kind of inconclusive but basically we might just see Mosasaurs with their big teeth and aggression evidence and assume they’re overly pugnacious when really they’re just normal animals