Isa wies auf das fünfzackige Kopfschild sowie auf die obersten Erhebungen der fingerförmig gezahnten Vorderschienen des Käfers.
I can’t find a definition for Vorderschienen. I’m also a bit fuzzy on Erhebungen but I think it means “protrusion” in this context.
This sentence is about biology, to be more precise about beetles ("Käfer"). The term "Vorderschiene" (Plural "Vorderschienen") refers to the lower part of the front leg (Tibia). I found two articles on Wikipedia on that topic, one in English, the other one in German. For humans, the part of the leg is called "Schienbein", but since beetles have six legs, the prefix "Vorder-" is added in order to denote the front leg.
In this case, the "Vorderschienen" are "fingerförmig gezahnt", which means "serrated in a finger shape".
Regarding "Erhebungen", I agree that "protrusion" fits quite well here. Since the context is a beetle, the protrusion is probably not too much. (Note that "Erhebung" could also mean "small mountain" if used in a geographical context).
