Biology Forums - Study Force

1. A trilobite is considered an index fossil because this organism existed during a  limited period in Earth's history. That means that any fossil located in a layer of rock beneath a layer containing trilobite fossils is ____________ than a trilobite.

2. According to this diagram, monotremes, marsupials, and placentals have the same _________ known as therapsid.

For this one, there is a cladogram with the therapsid at the bottom and the monotremes and marsupials on the top.

I think 1 is "older" and 2. is "ancestor."

Both correct imo.