Lecture 17: Marine Monsters

Question 1

What was the top predator in the Ordovician?

Answer 1

Camerocerus: an orthoconic nautiloid

6-9 m long

Question 2

What was the dunkleosteus?

Answer 2

The late Devonian placoderm fish.
10 m long, 3.5 tonnes
Bladed jaws 
Sucked prey in with water
1st vertebrate to catch prey larger than mouth

Question 3

What was the biggest fish in the Late Jurassic, UK?

Answer 3

Leedsichthys
22 m long (2x whale shark)
Sieved plankton through gills

Question 4

What was the largest late cretaceous bony fish?

Answer 4

Xiphactinus- a bony fish ~7m

Ate its prey whole and headfirst

Question 5

Several reptiles returned to the water at different times mostly during the Mesozoic: why?

Advantages:

Answer 5

More food & fewer predators
Low reptilian metabolic rate good aquatically, despite needing to breath air
Moving in water takes only 25% of the energy required by land animals

Question 6

When were the sea going crocs about? Info about them?

Answer 6

Mid Jurassic to early Cretaceous
Up to 7 m long
Flippers and fish-like tails
Some had lost bony armour (scutes)

Question 7

When were Triassic nothosaurs?

Answer 7

Long necked/tailed reptiles up to 3 m long
Small pointed teeth & long narrow jaws - fish catchers
Webbed feet: main propulsion still the hind legs

Question 8

What was transitional to plesiosaurs?

Answer 8

Triassic nothosaurs

Question 9

When were plesiosaurs and pliosaurs about?

Answer 9

Triassic to Cretaceous

Question 10

What were plesiosaurs and pliosaurs?

Answer 10

Broad, flat bodies, relatively short tails, like “a snake strung through a turtle”
2-20 m long
Limbs became flippers
Fingers fused/elongated, loss of elbow/wrist flexibility

Question 11

What plesiosaur had an extremely long neck?

Answer 11

Elasmosaurs

Question 12

What plesiosaur was large-headed, short-necked?

Answer 12

Plesiosaur

Question 13

Plesiosaur ecology

Answer 13

Endurance swimmers
Upward-pointing eyes: ambushed prey from below
Interlocking teeth, couldn’t chew – prey same size as mouth

Question 14

Plesiosaur diet

Answer 14

Ate fish, cephalopods, etc.

Gastroliths for stablity & digestion

Question 15

What are ichthyosaurs?

Answer 15

Fishy lizards highly evolved to aquatic environment with a “dolphin-like” body, short neck, elongated jaws and paddles longer at front.
Wrist/elbow inflexible
Increase number of finger bones – hyperphalangy – hydrofoils

Question 16

When did ichthyosaurs appear and die out?

Answer 16

appeared in Triassic, died out 90 Ma (Late K)

Question 17

Ichthyosaurs birthing

Answer 17

gave birth to live young
females contain foetuses
mother dies, spontaneous abortion 
early forms gave birth head-first
later forms, tail-first birth

Question 18

What were mosasaurs?

Answer 18

Efficient predators 3 – 17 m long

Competed with pliosaurs as top predators

Question 19

When were mosasaurs around?

Answer 19

Late Creteceous

Question 20

What did mosasaurs replace?

Answer 20

Ichthyosaurs

Question 21

Mosasaurs eating

Answer 21

Double-hinged jaws and flexible skulls (like snakes)

Could gulp down prey almost whole, a snake-like habit

Question 22

Mosasaurs diet

Answer 22

Diet included ammonites, fish, diving birds

Question 23

How did mosasaurs swim?

Answer 23

Whole body flexed like an eel in early ichthyosaurs – angulliform swimmers
Flexed rear body/tail – carangiform