LSAT PT 25 # 12 Lizards

Perminology wrote:It has long been thought that lizards evolved from a group of amphibians called anthracosaurs, no fossils of which have been found in any rocks older than 300 million years. However, a fossil of a lizard was recently found that is estimated to be 340 million years old. Lizards could not have evolved from creatures that did not exist until after the first lizards. Therefore, lizards could not have evolved from anthracosaurs.

An assumption made in the argument is that there are no

A) unknown anthracosaur fossils older than 340 million years
D) known antrhacosaur fossils that predate some lizard fossils


When you attempt the question, please do so within a 2 minute time limit!
OA A
Discuss!

IMO A:
Situation: oldest lizard fossils known 340 myrs old, oldest anthracosaur fossils known 300 myrs old
lizards could not have evolved from anthracosaurs because the oldest anthracosaurs known is younger than oldest lzard known.

Assumption: Any assumption is going to be about an possibility of older age of anthracosaurs . Only option dealing with age of anthracosaurs are A and C:

A) unknown anthracosaur fossils older than 340 million years : Yes, if there are yet to be known anthracosaur fossils older than 340 myr old reasoning falls apart, so its an asumption.
D) known antrhacosaur fossils that predate some lizard fossils : we are not looking for some anthracosaur fossils that predate some of the lizards fossils, but the one anthracosaur fossils that predate the oldest known lizard that is 340 myr old.

I go with option A . What is the correct answer?

maihuna:

A) unknown anthracosaur fossils older than 340 million years : Yes, if there are yet to be known anthracosaur fossils older than 340 myr old reasoning falls apart, so its an asumption.

great reasoning! But, after confirming that, did you look at the other choices? Instead of checking the other four choices, you should just take an extra second to confirm that choice A is correct. We don't care about wrong answers, and why they are wrong, and we don't want them to take up our time.

I solved it by this approach.

put this events on time line.



-------------A (340 Myears) .....B (300 Myears)............. today.


Now as question says that " Lizards evolved from a group of amphibians called anthracosaurs, no fossils of which have been found in any rocks older than 300 million years.

which mean point B is where lizards had evolved frm anthra.......

Next statement "a fossil of a lizard was recently found that is estimated to be 340 million years old. " which contradict first one. Means lizards were existed before 340 MY. so Point A.


Now last statement
Lizards could not have evolved from creatures that did not exist until after the first lizards. Therefore, lizards could not have evolved from anthracosaurs.

which means that there is an assumption by author that there was no antra..... older then 340 MY. Choice A.