. Bulletin. Natural history; Natuurlijke historie. EARLY JURASSIC SEMIONOTID FISHES 67. Fig. 24. Variation in dorsal ridge scales of the 5. tenuiceps group. A, classic "tenuiceps" dorsal ridge scales; camera lucida drawing of the neotype, 5". tenuiceps, YPM 8162; Sunderland, Massachusetts. B, hypermorphic ''tenuiceps'' dorsal ridge scales, YPM 6960; Turner's Falls, Massachusetts. C, moderate or globular ''tenuiceps" dorsal ridge scales (YPM 8932); Yale excavation in Wayne, New Jersey. Note the size of the dorsal ridge scales relative to the flank scales in each type. Scale
. Bulletin. Natural history; Natuurlijke historie. EARLY JURASSIC SEMIONOTID FISHES 67. Fig. 24. Variation in dorsal ridge scales of the 5. tenuiceps group. A, classic "tenuiceps" dorsal ridge scales; camera lucida drawing of the neotype, 5". tenuiceps, YPM 8162; Sunderland, Massachusetts. B, hypermorphic ''tenuiceps'' dorsal ridge scales, YPM 6960; Turner's Falls, Massachusetts. C, moderate or globular ''tenuiceps" dorsal ridge scales (YPM 8932); Yale excavation in Wayne, New Jersey. Note the size of the dorsal ridge scales relative to the flank scales in each type. Scale = 1 cm. about 6 to 9 robust, angular scales. These scales are broad at the base in an anterior-posterior direction and 2 to 3 times the width of a normal flank scale. Dorsally and along an anterior-posterior axis, the spines are convex. In lateral view, they are undercut slightly beneath the spine and the bases of the scales expand ventrally. The posteriormost scales are simple and convex with well- developed spines, each one overlapping the scale behind it. Very much like this robust series are hypermorphic scales, which differ from robust scales by their much larger size relative to flank scales and the fish itself (Fig. 24B). Semionotus with these exaggerated dorsal scales are known from the Feltville Formation in the Newark Basin (Olsen and others 1982) and the Tur- ner's Falls Sandstone in the Deerfield Basin, but not from the Towaco Formation of the Newark Basin. Thus, no descriptions of species with hypermorphic scales are included here. In a third version of the S. tenuiceps-iy^iG: dorsal ridge scale series, the globular form, enlarged scales do not begin until about the 6th scale posterior to the extrascapulars (Fig. 24C). Fish with this moderate scale pattern seem to be missing the several most exaggerated scales (3rd to 6th) in the robust series. From about the 6th to 12th scales, the scale bases are large and bulbous and the spines point. Please note that these imag
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