We don't have synonyms for hyostylic yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are homostylic.
(adj) :
(anatomy) Having the mandible suspended by the hyomandibular, or upper part of the hyoid arch, as in fishes, instead of directly articulated with the skull as in mammals.
(adj) :
(anatomy) Having the mandible suspended by the hyomandibular, or upper part of the hyoid arch, as in fishes, instead of directly articulated with the skull as in mammals.