| Description |
vi, 89 leaves : illustrations ; 28 cm |
| Summary |
"Otoliths are calcareous structures occurring in the auditory labyrinths of teleost (bony) fishes. Three pairs of these earstones normally are found: the sagitta, in the sacculus; the asteriscus, in the lagena; and the lapillus in the utriculus. In fishes other than the Order cypriniformes (carp, catfishes, and related forms), the sagitta is the largest otolith, and it may be used in taxonomic and other studies. Fossil earstones of cuskeels (Family Ophidiiae-Brotulidae), constituting the Preophidion complex, occur in relative abundance at various levels in the Claiborne, Jackson, and Vicksburg groups of the Lower Tertiary on the Gulf Coast. The present study was undertaken in order to separate and define the taxonomic units making up the complex. Three genera are recognized: Preophidion Dante and Frizzell (in press), with four described and seven new species; New Genus A, with one new species and New Genus B, with a single species. Detailed descriptions are given for all of these genera and species. Successful separation of these taxa resulted from conventional morphological treatment . Height/length ratios were plotted, and in some instances aided in separation of species. Thin sections of sagittae of Recent sunfishes (Lepomis cyanellus, Family Centrarchidae) were studied, in a partially successful attempt to determine the nature of the seasonal rings. Similar sections of the cuskeel otoliths furnished evidence for approximate age determinations that were of critical importance in the taxonomic study. The fossils belonged to three lineages within the complex, most of them included within the genus Preophidion. Evolution within the genus seems to have resulted in a sequence of closely related species found as fossils in the middle Eocene to Oligocene strata of the Gulf Coast. The entire complex belongs to a major lineage that includes Otophidium and Lepophidium of the living fauna (otoliths of O. taylori, O. scrippsae and L. brevibarbe examined). Sagittae of Ophidion barbatum and Brosmophycis marginata showed those genera to belong to distinct major lineages "--Abstract, leaves ii-iii. |
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