Studies on the Seorpaenoid Fishes of Japan : IV On a New Classification of Two Subfamilies, Sebastinae and Scorpaeninae, Based on the Osteological Characteristies of Suborbital Ring (Prelimiuary Report)
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The separation of two subfamilies, Sebastinae and Scorpaeninae, has been made on. the basis of counts in dorsal spines and vertebrae. 12 spines and 24 vertebrae for the latter subfamily and higher counts in both spines and vertebrae for the former (JORDAN and STARKS, 1904). From an examination of 47 species referred to 16 genera (Table I), the count of vertebrae was found graduating from species to species, not always coordinating with that of dorsal spines. The number of vertebrae within species, moreover, was not so constant as formerly believed, but a considerable degree of variation was noticed to exist in some species. These meristic characters, therefore, can not be of importance in the demarcation of two subfamilies. The under-mentioned characters involving configuration and number of suborbital bones demand to assort these genera included in these two subfamilies to three groups (Fig. I). (1) FIRST TYPE (Fig. I, 1).-In this probably most primitive type including Sebastes, Sebastodes, Sebastichthys and Sebastiscus, the second suborbital bone is always T-shaped, short and tapering posteriorly into a pointed or very rarely truncated (only in Sebasticus) tip, and remote from the upper ridge of preopercle; third to fifth or sixth suborbital bones invariably present, firmly attached with each other in a series surrounding the posterior margin of orbit, with the exception of the last one which is separated from the others and situated on sphenotic bone. (2) SECOND TYPE (Fig. I, II and III). - This type involves Helicolenus, Hozukius, Sebastosemus, Sebastolobus and Plectogenium, of which the first two closely resemble the former type in general appearance, but the second suborbital bone, being modified T-shape, is becoming narrower posteriorly and truncated at the extremity, and firmly attached to the upper ridge of preopercle, whilst in other three genera the second suborbital bone much broader, T-shaped in Sebastosemus, but uniformly broad in Sebastolobus and even expanded posteriorly in Plectogenium and firmly attached to the upper ridge of preopercle; third to fifth suborbital bones always present in all genera noted above and firmly attached witheach other except the last one which is located as in the first type. (3) THIRD TYPE (Fig. I, IV). - This most specialized type of the three involves Hoplosebastes, Scorpaenodes, Merinthe, Pontinus, Scorpaena, Scorpaenopsis and Setarches. The second suborbital bone, never T-shaped, is uniformly broad or gradually becoming wider posteriorly or toward middle part, and firmly attached to the upper ridge of preopercle, forming a typical suborbital stay; the third to fourth or fifth suborbital bones usually absent, but frequently a small suborbital bone is placed both on sphenotic and on the space between second suborbital bone and sphenotic bone, but they are separated from each other instead of being firmly connected. In these three types, the second one seems to represent the intermediate form, but its resemblance to the first type in features of third to fifth suborbital bones convinced the writer to place it under the category of the latter type although the second suborbital bone of Plectogenium and Sebastolobus closely resembles that of the third type.