Life In The Mesozoic Oceans Flashcards
What kinds of marine life are alive during the Mesozoic?
Bivalves, gastropods, cephalopods, large marine reptiles. Rugose and tabulate corals go extinct and for the echinoderms, there is a move away from the stalked crinoids to more mobile star fish and echinoids (sea urchins).
What marine creatures travelled in schools?
Cephalopods.
Describe belemnites.
Like modern squid but they had ten arms with a double row of hooks but no suckers.
Describe the ammonites.
Spiral shells that coil in single horizontal planes. They moved backwards through jet propulsion created when they squirted water through a tube called the hyponome. May have moved in shoals.
Describe the shell of Nautilus and ammonites.
Spiral form with many different chambers divided by a wall called a septum. They have a body chamber and they grow by moving forward in their body chamber and adding a new chamber to the back. A tube called a siphuncle runs the fulls length of all chambers and attaches to the creature in the body chamber.
Where were ammonites found?
The open ocean.
What corals replaces rugose and tabulate corals?
Scleractinian corals.
Describe the structure of corals.
Corals consist of soft, living coral polyps, sitting within hard calcium carbonate cups.
What did rudist bivalves do?
During later Jurassic and Cretaceous, they occupied niches populated by corals and were reef builders.
Where were rudist important?
On the margins of the Tethys Ocean and the early Atlantic, fringing North America from the Gulf of Mexico to the Maritime Provinces.
What fish diversified during the Mesozoic?
The bony fish.
Who patrolled the oceans during the late Cretaceous?
Sharks the size of the Great White Shark (Cretoxyrhina).
What tetrapods existed during the Mesozoic?
Turtles (evolved by Late Triassic) and giant alligators (evolved by Late Cretaceous).
Who was Mary Anning?
Paleontologist from Lyme Regis. Lyme Regis had many Jurassic fossils that she and her father found. Mary Anning was the first person to discover and extract an ichthyosaur, several other marine reptiles, and the first pterosaurs outside of Germany. Also contributed to George Cuvier’s idea that creatures can go extinct.
Describe the ichthyosaurus.
Resembled dolphins. Differences: extra set of fins, position of the eye, colour, size of the dorsal fin, orientation of the tail fluke. Might have travelled in groups and participated in mass stranding event.
What is convergent evolution?
The process that accounts for why unrelated organisms independently evolve very similar features when they adapt to similar niches.
How do dolphins and ichthyosaurs demonstrate convergent evolution?
Very different in biology, one mammal and one reptile. They existed in similar environments and exploited this environment in similar ways, so ended up looking much alike.
Describe the ancestor of whales and dolphins (cetaceans).
Indohyus. Size of a raccoon and terrestrial. They don’t look like cetaceans, but they have similarities like the auditory bulla (the bones that surround the inner ear).
Describe the ancestor of ichthyosaurus.
Don’t know exactly, but they were terrestrial and thought to be egg laying tetrapod. Why terrestrial?: Two pairs of limbs with bones that resembled digits in their flippers. The roof of the skull had a pair of openings called fenestra which are very typical of reptiles. They lacked gills, so they had to draw oxygen from the atmosphere.
Describe pliosaurs.
Short necked in comparison to plesiosaurs. Pliosaurs came in a number of sizes but the Late CretaceousKronosauruswas probably one of the largest at 12 m long. It probably hunted other marine reptiles in addition to fish and ammonites.
Describe plesiosaurs.
Long necked in comparison to pliosaurs. Mary Anning found first complete plesiosaur at Lyme Regis. Large plesiosaur called Elasmosaurus paddled to imitate underwater flying and had strong ligaments.
Describe Loch Ness.
Freshwater loch in Scotland where people claim to have seen Nessie. Stories came from Saint Columba and George Spicer and his wife. Became tourist attraction with photos.
Give an example of Lazarus Taxa and living fossil.
Lazarus Taxa: coelacanths.
Living fossil: horseshoe crab, sturgeon
Describe Mosasaurs.
Aigialosaurus from Cretaceous was a small semi aquatic lizard. It evolves into Dallasaurus which was also small but more aquatically adapted. It evolves into Tylosaurus that was really large and that fed on anything it wanted. Mosasaurs had backward pointing teeth and an extra set of teeth on their palate. Probably ambush predators that waited for their prey.
