Comparative Osteology of Representative Salmonid Fishes, with Particular Reference to the Grayling ( Thymallus arcticus ) and its Phylogeny

• Published in: Journal of the Fisheries Research Board of Canada
• Main Author: Norden, Carroll R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1961
• Subjects: General Medicine; Thymallus arcticus
• Online Access: http://dx.doi.org/10.1139/f61-052; http://www.nrcresearchpress.com/doi/pdf/10.1139/f61-052

The purpose of this study is to describe the morphology, particularly the osteology, of the grayling (Thymallus arcticus), in relation to that of the other salmonid fishes, in order to assess the phylogenetic position of the grayling and to synthesize the natural classification of the Salmonidae.Fresh and preserved material of 33 species in 9 genera of Salmonidae were studied. The study materials included dried whole skeletons from fresh fishes, stained bones of preserved specimens, and cross sections of larval stages. Effort was made to eliminate bias due to ontogenetic and sexual differences.The Salmonidae are soft-rayed teleost fishes belonging to the suborder Salmonoidei of the generalized order Clupeiformes (Isospondyli). Prior classifications of the salmonids have arranged them into one, two, or three families. As herein visualized, the family Salmonidae contains those salmonoid fishes that have three upturned caudal vertebrae. They are divided into three subfamilies: Salmoninae, the trouts and salmons, with an orbitosphenoid bone and a suprapreopercular bone, a basibranchial plate, teeth on the maxilla, no dermosphenotic bone, and parietals separate at the midline; Thymallinae, the graylings, with no orbitosphenoid, suprapreopercle or basibranchial plate, a dermosphenotic bone, teeth on the maxilla, and parietals meeting at the midline; and Coregoninae, with orbitosphenoid and dermosephnotic bones, no suprapreopercle, no teeth on the maxilla, and parietals meeting at the midline.The grayling possesses only two invariable morphological differences from other salmonids. These are the absence of an orbitosphenoid bone and the presence of seventeen or more dorsal fin rays. In other characters, there is overlap with one or the other subfamilies.Three osteological characteristics are thought to be more fundamental than the others: the toothless maxilla in the Coregoninae, the lack of an orbitosphenoid in the Thymallinae, and the separation of the parietals by the supraoccipital in the Salmoninae. Each character ...