Archierato rhondae Fehse & Simone 2020, nov. sp.

Archierato rhondae nov. sp.

(Figs. 13–15, 43)

urn:lsid:zoobank.org:act: 524F88FD-A7E3-4137-A038-12ADF628B041

Hespererato columbella: Cate, 1977: 362 (figs. 44a, 44b, 44e) (non Menke, 1847).

Types. (L, W, D, CT, LT respectivelly). Holotype: LACM 3646: 3.9 by 2.9 by 2.4, –, 11. Paratypes. 1: MSF MAM tv13-1 [subadult]: 4.4 by 2.5 by 2.2, –, 14; 2: MSF MAM tv13-2: 4 by 2.5 by 2.2, –, 16; 3: ZSM Mol 20171202: 4.0 by 2.7 by 2.2, –, 14; MSF (MAM tv13) 13 shells from type locality; DFB (5842) 4 shells from type locality.

Type locality. Encinitas, California, U.S.A. (33°02’04”N 117°17’38”W) [on beach at low tide, 3/1962].

Etymology. Named for Rhonda Mont, the wife of Dr. Michael A. Mont and contributor of the Molluscan Science Foundation.

Diagnosis. Shell small, 2.5 to 4.5 mm long, robust, pyriform, with slightly distant, irregular, coarse labral and obscured columellar dentition; ventral fold thickened, 11 labral teeth; maximum globosity at posterior third.

Description. Shell small, pyriform, spire elevated, blunt. Protoconch and subsequent whorls covered by thin callus. Suture slightly indistinct. Body whorl almost 80% of total height, maximum diameter at posterior third, convexly tapered anteriorly. Anterior ventral margin slightly indented. Dorsum rounded. Dorsal sulcus absent. Whole shell surface covered by very thin, sub-glossy callus. Aperture comprises ~75% of total height, straight and narrow. Labrum narrow, thickened, smooth, flattened ventrally, anteriorly declivous. Outer labral margin almost straight, rounded, callused, edged at inner margin. Labral teeth coarse, less developed, slightly distant, 11 in number, restricted to labral edge. Siphonal canal short, narrowed, rounded and slightly protruded. Anal canal simple, slightly protruded. Columella straight, flattened without inner carinal ridge, roundly callused parietal lip. Columellar denticles obscured at mid-portion, anterior most forming slightly thickened terminal ridge, posterior most somewhat enlarged, projecting. Fossula obscured, not delimited from columella. Callosities and suture white; dorsum, siphonal canal and whorls olive; protoconch of somewhat darker color.

Variability. The strength of labral denticles varies, some shells are light beige, the elevation of the spire varies slightly, and none of the fully matured shells show countable columellar teeth even at higher magnification. The shell outline is quite uniform although the shells are more or less inflated. The inflation, however, varies in slightly.

Distribution. Besides the type locality, also found at ‘Bahía Adair, Guaymas; Santa Rosalia, Loreto, E. Baja California’, W. Mexico (Cate, 1977: 362).

Remarks. Archierato rhondae is easily distinguishable from Archierato michaelmonti nov. sp., A. columbella, A. galapagensis and A. panamaensis by its small size alone in contrast to Cate’s (1977: 362) statement. The pyriform shell outline separates A. rhondae from A. michaelmonti with its sub-triangular shape. Archierato rhondae is also distinguishable from the latter by the elevated spire, the more distant labral and the obscured columellar denticles, the almost straight profile of the labrum, the straighter aperture, the lack of a dorsal dimple on anterior terminal collar and the less indented ventral margin. Distinguishing features—the shell outline and the labral profile—are already visible in subadult specimens (compare the paratypes of both taxa).

Archierato rhondae is separated from A. columbella by its simple coloration and from A. panamaensis by the green instead of pale brown coloration. Nevertheless, A. rhondae is also distinguishable by the obscured and posterior projected columellar dentition, the straight aperture, the blunt apex, the shorter siphonal canal, the narrower shell outline, the straight and flattened columella and the straight outer labral margin.

A. rhondae is readily distinguishable from A. galapagensis by the shell outline alone so a further discussion is not necessary.

A. rhondae is readily distinguishable from A. galapagensis by the shell outline alone. The outline of A. galapagensis is oblong ovate with maximum width at mid-portion whereas the shell of A. rhondae is pyriform with maximum width at posterior third. The columellar denticles are always obscured at mid-portion in A. rhondae but developed in A. galapagensis. The labral denticles are fine, close-set and restricted to the inner labral edge in A. galapagensis but coarse, spaced and slightly elongated as short folds onto the labrum in A. rhondae. The new species possesses a colored anterior terminal tip whereas it is colourless in the A. galapagensis.