Homology And Terminology Of Higher Teleost Postcleithral Elements
M D Gottfried · Transactions of the San Diego Society of Natural History · 1989
Primitively, actinopterygians have a single postcleithrum, which is not homologous to the anocleithrum of sarcopterygians.The possession of multiple postcleithra is a shared derived feature of leleosts.Three to five postcleithra are typically found in lower teleosts; as many as seven are present in primitive fossil forms.Consideration of the positional relationships of postcleithra in primitive teleosts provides criteria for homoiogizing and naming teleost postcleithra.Ctenosquamate teleosts (myctophiforms and acanthomorphs) typically possess two postcleithra; on the basis of positional relationships these are interpreted as postcleithra two and three (not "one and two," "upper and lower," "dorsal and ventral," or "proximal and distal" as in previous interpretations).Ctenosquamates are therefore derived in having lost postcleithrum one.which is considered here to be the homologue of the single postcleithrum of primitive actinopterygians.