Alright the last exam for Dinosaurs is today so lets discuss the two final topics, swimming reptiles and (appropriately enough) Extinction. I’ll use my original style for Dinosaur exams because frankly I’m pretty tired.
Short and long-necked plesiosaurs, ichthyosaurs, and mosasaurs. Their relative speeds and individual characteristics?
Plesiosaurs were likely the slowest of the group, which frankly was not much of a hindrance given their size. Whales don’t exactly travel at mach 1 through the sea but they get the job done. In the world of plesiosaurs you have the long neck versions, Elasmosaurs, and the short necked version, Pliosaurs. The Elasmosaurs may have struck their pray like a snake, recoiling their long necks and lashing out from the fog of the sea. This would actually seem like a more reasonable origin for the snake striking system than just getting high one day and telling all your snake buddies you have a ‘great idea’.
Mososaurs are probably the second group in terms of speed. These fellows were short necked, long, snake-ish (not so much snake moreso ish), reptiles with four fins (not unlike Plesiosaurs). Now while second they were second in speed, when taking their size into account, isn’t much of a silver medal. They were gold in the sense that their size would cause you to poo in fear and then their speed would gobble you up before you could escape.
One thing I forgot to mention is their long paddle tails, this would of sucked because its in the study notes as “something you need to know” so that could have very well been a missed question ;).
The final group to talk about is the Ichthyosaurs, these little dudes are adorable-ish and fast like dolphins. They had fish like fins that waggled left to right and everything else really was so fish like that I might as well use the slide image instead of trying to describe a fish.
They gave live birth like sea mammals, tail first even, scientists know this because they found a fossil that died during birth and it has a smaller fossil (a baby) sticking out its rump tail first. What a way to go out.
How did plesiosaurs swim?
Obviously we can’t ask them but there are many visual cues when you look at an animals bone structure as to how it likely moved. They had four sets of flippers that they probably used like oars, which is pretty neato and quite a cool visual. There is no modern day animal in the sea that does this (to my knowledge) which makes it all the more interesting.
What are fish-eating teeth like?
Long, Pointed, and Spaced. Essentially they are like those pronged spears people use to not only possible spear a fish but to at the very least entrap it between the prongs.
What are the adaptations for speed in Ichthyosaurs?
I already gave this one away, they were built like dolphins and swam with a tail that was side to side and not up and down or anything else.
How did they give birth?
Ah…gave this one away too. Just like sea mammals they birthed live and backwardly facing so that the animal could breath the longest (since the umbilical cord wouldn’t have snapped yet).
How did Eurhinosaurus live?
An Ichthyosaur with a very long upper jaw or bill that looked a lot like a sawfish. They likely swam through fields of fish and swung their heads around to chop up pray then came back through and gobbled that stuff up. Regardless they weren’t winning any beauty competitions.
What were Mosasaurs related to and how did they swim and eat.
Lizards, especially Komodo Dragons and Snakes. These are the large snakelike fellas I told you about earlier that were pretty fast and pretty huge. They had a ratcheting snake like jaw just like a snake that probably…well..ratcheted food down their gullet.
Mass vs background extinctions?
Background extinctions happen all the time, something like 99+% of all things that have ever lived on the planet are dead and gone. Given time all species go extinct, unfortunately even we are extremely vulnerable.
Mass Extinctions involve basically everything on the Earth dying off geologically instantly.
What were the two biggest mass extinctions?
The P-TR (Permian-Triassic) and the K-T extinctions, had you been alive for either you wouldn’t be alive (which goes without saying ;D).
What is the probable cause of the K-T extinction?
An asteroid dropping hits junk into the Gulf of Mexico region of the world.
What were the consequences of an asteroid impact?
Temperatures rise dramatically for a short period of time (hundreds of degrees dramatically), matter is rocketed into the atmosphere and blankets the entire planet in darkness for a while, most vegetation and anything else that can burn on the surface of the earth does. Also you have animals dying and anything that eats them dying and anything that eats them dying. See where I’m going with this?
What evidence do we have to support this hypothesis?
There are large quantities of Iridium about the point where the KT boundary is which is not an element you’d commonly see on the surface of Earth, however from an extraterrestrial source its not all that unheard of. They also have found a crater that fits the estimated 10 km asteroid. Yeah I know big dude. Essentially in a flash 10 billion Hiroshima sized bombs were exploded and the world was changed forever (organically speaking).
Amazing stuff. Looking forward to the exam, all credit here should be directed to my Professor. The images, the questions, and indeed the knowledge I gained to answer them are thanks to him.