. Devonian fishes of Iowa. Fishes, Fossil; Paleontology; Paleontology. 210 IOWA GEOLOGICAL SURVEY Family CTENODONTIDAE.* Cranial roof bones numerous; no secondary upper jaw, and no marginal series of teeth above or below; jugular plates pres- ent or absent. Dentition consisting of an upper and lower pair of triangular "ctenodont" dental plates, whose outwardly radi- ating ridges usually terminate in rows of conical denticles or tubercles, rarely smooth or nearly so; no vomerine teeth so far as known. Tail heterocercal or apparently diphycercal. Ex- cluding the anal, which is always d
. Devonian fishes of Iowa. Fishes, Fossil; Paleontology; Paleontology. 210 IOWA GEOLOGICAL SURVEY Family CTENODONTIDAE.* Cranial roof bones numerous; no secondary upper jaw, and no marginal series of teeth above or below; jugular plates pres- ent or absent. Dentition consisting of an upper and lower pair of triangular "ctenodont" dental plates, whose outwardly radi- ating ridges usually terminate in rows of conical denticles or tubercles, rarely smooth or nearly so; no vomerine teeth so far as known. Tail heterocercal or apparently diphycercal. Ex- cluding the anal, which is always distinct, the remaining median fins are either distinct or continuous (two dorsals in all genera but Phaneropleuron). Genus DIPTEMS Sedgwick and Murchison. Body elongate, not much laterally compressed, covered with enamelled cycloid scales; head depressed, snout obtuse. Dental plates, above and below, triangular in shape, with outwardly radiating ridges, tuberculated or strongly crenulated, sometimes becoming obsolescent. Paired fins acutely lobate, two remote dorsal fins opposed to the pelvic and anal fins, separated from the Fig. 33. Fig. 33. Dipterus valenciennesi Sedgw. & Murch. Lower Old Red Sandstone; Scotland. stored by Dr. R. H. Traquair. x I. (alter Traquair.) Left lateral aspect as re Our knowledge of the complete form of this genus, shown in text-figure 33, is dependent entirely upon the small, well-pre- served skeletons found in the Scottish Lower Old Eed Sand- stone. These remains were originally described in successive *On the propriety of using this term instead of Dipterida?, see Traquair in Geol. Mag. 1893, dec. 3, 10, p. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Eastman, Charles Rochester, 1868-1918; Iowa Geological Survey. Des Moines : Iowa Geological Survey
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