Epural bones in teleost fishes: A problem of phylogenetic homology
2015
Doosey, M.H. (University of Kansas, Biodiversity Institute, Lawrence, Kansas (USA)) | Wiley, E.O.
In the past, epural bones of teleost fishes have been labeled sequentially from anterior to posterior (e.g., epural 1, epural 2, etc.) without regard to their position relative to centra and ventral elements of the caudal fin. Recent research on caudal fin development of basal teleosts (e.g., Elops saurus and Hiodon spp.) and salmonids (e.g., Thymallus thymallus and Oncorhynchus spp.) indicates that simple numbering of epural bones is not phylogenetically meaningful. Our purpose is to demonstrate that 'higher' teleost fishes show a variety of patterns of epural formation and development and that some of these may be phylogenetically informative characters. We describe the early ontogeny of the caudal fin with special reference to the epurals for selected species of teleosts. Development of epurals is detailed beginning with the earliest detection of chondrocytes in growth series of various teleosts. Epurals form after notochord flexion in the examined otomorphs, salmonids, and Mallotus villosus, as well as in Chauliodus macouni and Synodus foetens. Epurals form before flexion in the examined ctenosquamates, which allows for simple association of an epural with a ventral caudal element (i.e., hypural). After notochord flexion, epurals may reposition relative to their corresponding hypurals and this is a factor that can confuse homology assessment in adult specimens. It is recommended that epurals be named using the polyural terminology according to their position relative to ventral caudal elements early in ontogeny (e.g., epural of preural segment 1 or epural of hypural 2).
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