Lecture 17: Marine Monsters Flashcards
What was the top predator in the Ordovician?
Camerocerus: an orthoconic nautiloid
6-9 m long
What was the dunkleosteus?
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
What was the biggest fish in the Late Jurassic, UK?
Leedsichthys
22 m long (2x whale shark)
Sieved plankton through gills
What was the largest late cretaceous bony fish?
Xiphactinus- a bony fish ~7m
Ate its prey whole and headfirst
Several reptiles returned to the water at different times mostly during the Mesozoic: why?
Advantages:
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
When were the sea going crocs about? Info about them?
Mid Jurassic to early Cretaceous
Up to 7 m long
Flippers and fish-like tails
Some had lost bony armour (scutes)
When were Triassic nothosaurs?
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
What was transitional to plesiosaurs?
Triassic nothosaurs
When were plesiosaurs and pliosaurs about?
Triassic to Cretaceous
What were plesiosaurs and pliosaurs?
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
What plesiosaur had an extremely long neck?
Elasmosaurs
What plesiosaur was large-headed, short-necked?
Plesiosaur
Plesiosaur ecology
Endurance swimmers
Upward-pointing eyes: ambushed prey from below
Interlocking teeth, couldn’t chew – prey same size as mouth
Plesiosaur diet
Ate fish, cephalopods, etc.
Gastroliths for stablity & digestion
What are ichthyosaurs?
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
When did ichthyosaurs appear and die out?
appeared in Triassic, died out 90 Ma (Late K)
Ichthyosaurs birthing
gave birth to live young females contain foetuses mother dies, spontaneous abortion early forms gave birth head-first later forms, tail-first birth
What were mosasaurs?
Efficient predators 3 – 17 m long
Competed with pliosaurs as top predators
When were mosasaurs around?
Late Creteceous
What did mosasaurs replace?
Ichthyosaurs
Mosasaurs eating
Double-hinged jaws and flexible skulls (like snakes)
Could gulp down prey almost whole, a snake-like habit
Mosasaurs diet
Diet included ammonites, fish, diving birds
How did mosasaurs swim?
Whole body flexed like an eel in early ichthyosaurs – angulliform swimmers
Flexed rear body/tail – carangiform
