Dismantling the trachinoidei: Evidence of a scorpaenoid relationship for the Champsodontidae

Abstract

An examination of the osteology and myology of the Champsodontidae reveals a number of apomorphic features (e.g., double-headed palatine, large pelvic radial, epaxial muscle inserting on the medial pelvic-fin ray, posterior levator internus inserting on the third epibranchial). The evidence for a Champsodontidae/Chiasmodontidae relationship is examined through a re-evaluation of the basal characters used to define the suborder Trachinoidei. The Champsodontidae are removed from the Trachinoidei and a chiasmodontid sister relationship is rejected. After investigation of several possible alternative relationships (Paracanthopterygii, Gobioidei, Callionymoidei, Kurtoidei, Apogonidae, Blennioidei, Trichodontidae), champsodontids are hypothesized to be members of the perciform suborder Scorpaenoidei. This hypothesis is based largely on the synapomorphy of a parietal spine with an opening for passage of the supratemporal sensory canal, a unique condition of champsodontids and some scorpaenoids. A shared Type 1 epaxial muscle morphology, with separate fibre insertions on the distal tips of the spine-bearing dorsal-fin pterygiophores, is unusual and probably derived among perciforms. Champsodontids also share with some scorpaenoids Type 5 spinoid scales and the origin of Baudelot's ligament from the first vertebra rather than the basi-occipital, although neither of these features is unique to these taxa. The occurrence of an enclosed sensory canal on the parietals of Trichodontidae suggest that their relationships might also lie with the Scorpaenoidei. Arguments pertaining to the removal of champsodontids from the trachinoids apply equally to the hypothesized membership of the Cheimarrichthyidae, Pinguipedidae, Percophididae, Trichonotidae, Creediidae, Chiasmodontidae, and notothenioids in the Trachinoidei. Inclusion of these taxa within the Trachinoidei is not well-supported, and their relationships require further investigation.