This is the family of hard-bodied ticks, with a hard exoskeleton as opposed to the soft-bodied ticks (Argasidae) which have more of a leathery exoskeleton. The head of species from this family protrudes from the body as opposed to the family, Argasidae, where the head is hidden underneath.
The hard-bodied ticks of this family are the ones currently in the park database. If you encounter the soft-bodied type, please report it to the park, and bring in a specimen to park staff during the weekdays at the Twin Creeks Science and Education Building or any of the visitor centers.