Nucella demouthae, 2023

Powell, II, Charles L., Roth, Barry & Garcia, Christine N., 2023, Nucella demouthae, A New Species of Late Miocene Muricid Gastropod From Northern California, U. S. A., PaleoBios 40 (12), pp. 1-11 : 3-4

NUCELLA DEMOUTHAE POWELL, ROTH, AND GARCIA , N. SP.

FIGURES 2 -15

Nucella sp. aff. N. lamellosa ( Gmelin, 1791) , Powell et al. 2004:61, not Gmelin, 1791.

Nucella n. sp.? aff. N. etchegoinensis ( Arnold, 1908) , ribbed variety, Powell et al. 2019, not Woodring et al. 1940[1941], not Arnold 1909.

Zoobank LSID — urn:lsid:zoobank.org:act:351C9DCC-6BB0-4E5B-BF1A-AA0BB9C61F00

Diagnosis —Distinguished from similar eastern Pacific Nucella by its moderate size, thickened and recurved outer lip, and faint to prominent spiral cords that are most prominent on the body whorl. Where observable, two strong denticles appear on the inside of the outer lip. This latter feature may also be found in N. lamellosa , which displays none, or two to six denticles on the interior, of the apertural lip.

Holotype — CASG 73156 , height 33. 4 mm, maximum width 19.5 mm.

Paratype — CASG 78594 , height 43.6 mm, width 24.5 mm (incomplete specimen) ; CASG 78595 , height 36.0 mm, width 25.2 mm ; CASG 78596 , height 32.1 mm, width 18.9 mm ; CASG 78597 , height 29.8 mm, 17.5 mm ; CASG 78598 , height 19.2 mm, width 11.8 mm . CASG 78599 , height 13.1 mm, width 8.8 mm .

Referred Specimens — CASG localities 54135 (20[66]) and 54136 (2[3]); most specimens are poorly preserved.

Occurrence — Known only from basal Wilson Grove Formation (late Miocene; “Jacalitos” CPMS) exposed at Bloomfield Quarry , north of Bloomfield, Sonoma County, California, U.S.A.

Etymology —Named for Dr. Jean Frances DeMouthe, Senior Collection Manager of Geology at CAS for many years and longtime friend.

Description — Shell of small to moderate size for the genus (8.1 to 43.6 mm height), fusiform with an elevated spire forming an apical angle of about 20°. As many as six postembryonic whorls may be present, although the apex is generally broken off in most specimens. Early whorls are smooth, with two strong, unornamented spiral ribs, the first approximately midway between the sutures, the second slightly stronger, just posterior to the first; third to seventh progressively weaker spiral ribs sometimes present posterior of the main rib on the lower whorls. In larger mature specimens the spiral ribs become wider and widely spaced. Between these spiral ribs are faint, narrow, radial ribs with wide interspaces about twice as wide as the ribs. The outer lip is sharply expanded and thickened into an oblique flange, with a smooth inner margin and two teeth moderately deep in the aperture. Siphonal fasciole prominent, and siphonal canal relatively short (23% of the total length of the shell), narrow, and obliquely recurved. The columella is smooth with a rounded posterior end, which appears to extend up the adjacent exterior of the shell forming a small pseudoumbilicus. Given that these shells commonly have the aperture broken off, the following percentages are estimates. The siphon is about 23% the total length of the shell, while the aperture is about 35% of the entire shell length. Immature shells have a shorter spire than adults and do not have a recurved outer lip, but, instead, a sharp vertical lip. In addition, juvenile shells have more prominent and closely spaced spiral ribs than adult specimens.

Figures

Figure 2-3. Nucella demouthae Powell, Roth, and Garcia n. sp. CASG holotype 73156. CASG locality 54136. Bloomfield Quarry, north of Bloomfield, Sonoma County, CA. Height 33.5 mm, width 19.2 mm. 2. Adapertural view, 3. Apertural view.