lec 10- transitions Flashcards
what are theropods, therapsids, and synapsids?
-Theropods: meat-eating dinosaurs, have three toes and walk on hind legs
-Therapsids: “mammal-like” reptiles that are descended from synapsids, all went extinct
-Synapsids: a clade that includes the extinct therapsids and their mammal descendants, including living mammals
what was the transitional organism from land to water for whales called?
ambulocetus
what was the first fish to go from water to land?
Tiktaalik
what fish led to the transition to tetrapods?
lobe-fin lungfish
what are lobe-fin fish?
a class of fishes with bones inside their fins
how many living lobe-fin fish are there?
coelacanths, and three different lungfish (6 taxa in all) are still living
are any living lobed fin fish related to tetrapods?
no, but they share a common unknown ancestor with another lineage that did lead to the tetrapods
which lobe-fin fish is the closest living relative to tetrapods?
coelacanths
how do coelacanths relate to tetrapods in fin bone structure when compared to ray-finned fish?
coelacanths have one bone connecting to the shoulder like tetrapods, but ray-finned fish have multiple
what was the “age of fishes” called?
The devonian
what lobe-fin fish briefly moved to the edge of land and where was its fossil discovered?
eushtenopteron, found in Quebec, Canada
what was the early tetrapod and amphibian called?
early tetrapod: Acanthostega
early amphibian: Ichthyostega
what was the transitional fossils between lobe-fin lungfish and tetrapods?
tiktaalik
where were the fossils of tiktaalik found and which scientists did it?
found on Ellesmere Island, Canada, and was found by Ted Daeschler and Neil Shubin
what were the characteristics of tiktaalik?
-weak hindlimbs, bones poorly developed and not joined to pelvic bone
-strong forelimb bones, allowed for walking and had a neck and wrist (tetrapod synapomorphy)
–was a walking fish that spent most time underwhater
what did the antievolutionaries believe about tiktaalik?
that it was just an alligator
how does tiktaalik vary from alligators?
-tiktaalik had external ears, fish scales, side nostrils, sharp small uniform teeth
-alligators have no external ears, bony scutes, nostrils on top, and variable large teeth with different jaw shape, blunt teeth
how does tiktaalik relate to lobe fins and tetrapods?
its forelimb bone structure is homologous with the other two
what was the trait evolution of tiktaalik?
weight bearing elbows, bending wrist, neck, loss of bony operculum
