Are Devil’s Cigar mushrooms poisonous? My dad has
this mushroom
growing on his land, in large quantities.

He is curious if these are poisonous to humans, as he is interested in cooking them. He commented that he has seen some that look to have been partially eaten by animals.
I cannot find specific information about Urnula Geaster (devil's Cigar; Texas Star), however, almost all of the members of the Urnula family are inedible.  I would hazard a guess that this variety is as well.

A Field Guide to Mushrooms