Lesson 12 (Life in Mesozoic Oceans) Flashcards
what types of organisms were prominent in the cambrian
Trilobites and Burgess Shale type organisms
what types of organisms were prominent in the paleozoic
trilobites and other forms of marine life (brachiopods, echinoderms on fixed stalk (crinoids) and corals)
how did the look of the mesozoic oceans change following the permian extinction
- bivalves (clams) and gastropods (snails) become the more important shelly fossils as opposed to brachiopods
- cephalopods became even more common
- rugose and tabulate corals are extinct
- echinoderms move away from stalked crinoids to mobile starfish and echnoids (sea urchins)
- large marine reptiles become top predators
what is the most common fish in the mesozoic
Bony fish, cephalopods also common
what are cephalopods
“head foot”: group of mollusks that are relatives of squid and octopus
what is a unique trait about Orthoconic Nautiloids, one of the early cephalopods
Straight shells
what is a unique trait about Belemnites, one of the early cephalopods
10 arms, double row of hooks but no suckers
- belemnite comes from the greek word for dart/arrow
What is the cousin of Belemnites? How did they get their name?
- Ammonites
- Egyptian god Ammon who is shown to have ram horns
How do ammonites help with biostratigraphy?
Since they were so common, ammonite fossils are used to split geological time into separate ammonite zones
how did ammonites move
backwards, through the water by jet propulsion created by squirting water through a tube called the hyponome
How are Nautilus and Ammonites similar
- spiral shell with different chambers
- internal chambers divided from next chamber with chamber wall called ‘septum’
- grow by moving forward in their body chamber and adding a new chamber to the back of their existing body chamber when they become too large
- tube called siphuncle runs the full length of all chambers and attaches on to the living creature
- animals use siphuncle to vary fluid in each chamber, allowing them to control bouyancy in the water
what is the first ammonoid to evolve? When did they go extinct?
Goniatities, Mesozoic
how do ammonoids counterbalance an offset siphuncle?
- higher volume of septal face on the other side
- septal face centroid offset to the other side
what characteristics did ammonites start to get prior to their extinction?
shells started to uncoil and take on unusual shapes, likely due to the changing climate
How long was the coral gap and when was it
10 million years after the permian extinction
what was the creature that new corals evolved from called
scleractinian corals
what are corals composed of
soft, living coral polyps sitting within hard calcium carbonate cups
what are infaunal bivalves
- dig down into the hard rock of reed
- bioeroders of reef environment
what are rudist bivalves
- some stood vertically with one of their shells buried in sediment and the other acting like a lid
- others encrusted on surfaces
- others just lay on the sediment surface
- good collector of oil (many hooks, crannies that are well connected)
Which type of fish went extinct during the permian extinction
Acanthodian fish - preevolution of bony fish
Which evolution of bony fish could grow up to 6m long
Xiphactinus
Which shark was prevalent in the late cretaceous
Cretoxyrhina or Ginsu Sharks
- similar size to great white
what kinds of tetrapods shared the mesozoic environment with the invertebrates and fish?
- turtles (archelon): 10ft long turtle
- giant alligators (mainly fed on sea turtles)
who collected the fossils displayed at the national history museum
Mary Anning
What dinosaurs did Mary Anning discover?
Discovered and extracted Ichthyosaur, Several marine reptiles and the first pterosaurs outside of Germany. Also plesiosaur
How did Anning’s idea help support the idea of extinction?
Supported George Cuvier’s ideas of extinction
How does ichthyosaurs differ from modern day dolphins? Which feature would be the most significant?
- Position of the eye
- colour
- size of the dorsal fin
- orientation of the tail fluke. (most significant)
what is convergent evolution
unrelated organisms develop similar features when living in similar environments (ichthyosaurs is a reptile while dolphin is a mammal, yet they look similar)
what are dolphins and whales ancestor? How are they similiar?
Indohyus, a small herbivorous deer, the size of a raccoon
- bones that surround inner ears are similar adapted for hearing under water
What features of ichthyosaurs indicate a terrestrial origin for the group?
- 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.
What is the biggest Ichthyosaurs
Shonisaurus, grew up to 50 feet long
What happened to shonisaurus?
37 triassic specimens were found side by side in Nevada, suggesting a mass stranding event
What are some traits about Ichthyosaurs?
- Good Eyesight
- Viviparous (gave birth to living creature as opposed to egg)
What are the two kinds of plesiosaurs
Short neck (PLIOSAUR)
Long neck (PLESIOSAUR)
Largest pliosaur?
Kronosaurus, 12m long
Largest plesiosaur?
Elasmosaurus, 14m long
- neck had 76 vertebrae
What is the only mesozoic aquatic reptile that people claim still exist
Plesiosaur (Lochness moster)
What is the history of the Lochness monster
1) Saint Columba, local had been mauled, lured monster out, stopped monster with the sign of the cross
2) George Spicer saw monster pass in front of car
What are lazarus taxa
Organisms that were thought to have been extinct but were subsequently found
Example of lazarus taxa
Coelecanths
Example of living fossil
Horse shoe crab, has not changed whatsoever since it first evolved 450 million years ago
Why is the loch ness thoery false
1) lack of fossils suggest none of the creatures survived the end of the cretaceous
2) it is unlikely plesiosaurs moved around on land like described by the Spicers
3) in order for there to be a viable population of plesiosaurs in the Loch there would have to be many of them and there is probably not enough fish to support that
What explains the humps that people see in the water and claim is the Loch Ness monster?
Logs, Seals, Otters
Potentially the Sturgeon fish (responsible for creating caviar)
Mosasaur Evolution Path?
Aigialosaurus - Cretaceous (small semi-aquatic lizard)
Dallasaurus - more aquatically adapted lizard
Tylosaurus - Largest Mosasaur
Qualities of Mosasaurs
- backward pointing teeth
- additional set of teeth on their palate
- didnt chew, instead gulped
- ambush predators
