Fenimorea Bartsch 1934
Creators: name: Fallon, Phillip J.
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Neogastropoda
Drilliidae
Fenimorea

description: Genus Fenimorea Bartsch, 1934
Type species: Fenimorea janetae Bartsch, 1934 by original designation (Recent, off the north coast of Puerto Rico).
Diagnosis. According to Bartsch, shell tall-spired, fusiform, truncated anteriorly with a large body whorl and short, wide anterior canal. Protoconch has approximately two smooth, rounded whorls. Sculpture is dominated by axial ribs that may be few or numerous, extending from suture-to-suture but reduced and crescent-shaped in the shoulder sulcus; by a hump-like varix approximately ⅓-turn behind the outer lip; by spiral sculpture of ridges anteriorly, spiral threads in the sulcus, and by microscopic wavy or jagged lines and incremental growth lines that form a microscopic shingle-like pattern over most of the shell surface. The anal sinus is deep, rounded at its apex, and offset from the suture at its entrance by a parietal callus. Usually a colorful shell with bands and/or patches of brown or reddish brown set on a whitish base.
Key characteristics. The presence of all of the following characteristics is diagnostic of Fenimorea and separates it from other TWA drilliid genera:
1. Shell surface microsculpture of very fine spiral grooves or ridges spaced greater than their width and intersected by more closely spaced axial growth striae that give grooves or ridges a jagged appearance, and between the striae are “pits” or axially aligned depressions (see Plate 65). In some species this pattern is overlain with stronger, irregularly-spaced growth striae and widely spaced shallow but broader spiral grooves that end in dimples or “teeth” at the edge of the outer lip;
2. Ribs usually numerous, run from suture-to-suture, abruptly reduced in the sulcus, becoming lower, narrower, and recurved, reminiscent of the outline of the anal sinus.
3. Varix variable, hump-like (in apical view, low and broad) in shallow water species, and usually higher and narrower in deep water species, positioned between ¼- to ⅓-turn from the edge of the outer lip, frequently with a dark color blotch in species that have colored bands; and
4. Anal sinus a deep U-shaped notch located close to the suture and often offset laterally by a parietal lobe, with flared edge such that the sinus appears spout-like in some species.
Species in this genus appear to fall into two separate morphological types that are linked to their habitat. Those from shallow water (0–50 m) are smaller (<30 mm), have low, broad, hump-like varices, lower ribs, wider, more distinct sulci, and shorter anterior canals. Fenimorea fucata (Reeve, 1845) is an example this shallow water type, as all that are depicted in Plate 102. Deep water species, those commonly found at greater than 50 m depth, are among the largest of the genus (> 30 mm), and sometimes (not consistently) have higher, narrower varices, bolder ribs, narrower sulci, and longer anterior canals with a tapering last whorl. An example of a large species of this type is Fenimorea janetae, and of smaller ones are Fenimorea pagodula (Dall, 1889), Fenimorea petiti Tippett, 1995, and Fenimorea moseri (Dall, 1889).
Nomenclatural notes. The nomenclatural status of Fenimorea has been unsettled (as exemplified by the synonymy list under F. f u c at a below). Some modern workers treat Fenimorea as a genus, others as a junior synonym of Splendrillia. This latter group includes Turgeon et al. (1998: 257) who list F. fucata, F. halodorema Schwengel, 1940, F. kathyae Tippett, 1995, F. moseri (Dall, 1889), F. pagodula (Dall, 1889), F. sunderlandi (Petuch, 1987), and F. petiti Tippett, 1995 in Splendrillia on the basis of Petuch's placement of F. janetae Bartsch, 1934, the type of the genus, in Splendrillia (Petuch, 1987: 18, 19). Fenimorea is treated as a subgenus of Splendrillia by Espinosa et al. (1995). Fenimorea is treated as a separate genus in this work, as explained below.
Gibson (1962: 235) states that Fenimorea is mainly distinguished by its scale-like ornamentation but feels that this character may not be of generic value. The microsculpture of Fenimorea is unique to the genus as defined herein however, and this and other characteristics easily distinguish it from Splendrillia. In addition to possessing a unique microsculpture, Fenimorea is generally larger and stockier, has a deep anal sinus, usually set off from the suture by a parietal callus, has ribs that extend from suture-to-suture, although usually transition in shape and size in the sulcus, and ribs that are straight or only slightly oblique. Splendrillia on the other hand, has ribs that terminate at the sulcus and are short and oblique in most species of the group. The anal sinus lies closer to the suture, is usually not offset by a large parietal callus, but rather there is a low callus in front of the sinus; i.e., the outer lip joins the suture behind the callus. Fenimorea usually has more colorful shells with blotches or bands of deep color that contrast markedly against the shell’s whitish base color. Splendrillia has a glossier shell, is smaller, slimmer, and of a more subdued color, but sometimes with darker blotches, especially on the varix. These differences are significant enough to separate the two at the genus level.
Similar genera. Fenimorea is most similar to Decoradrillia, new genus. It differs in possessing a distinct sulcus, lower and more numerous ribs, and a hump-like varix, although these characteristics are not all present in deep water species. Shell surface microsculpture is an important distinguishing characteristic. The difference is explained under genera difference in the introduction to Decoradrillia. Compare the SEM images of the microsculptures of the two genera in Plates 51 and 65 for illustration of their differences.
Clathrodrillia differs principally in possessing much stronger spiral grooves without overriding growth striae that produces the “pits” seen in Fenimorea. Its growth striae are finer than the spiral grooves. The shell of Fenimorea is generally not as high-spired and without turreted whorls.
Neodrillia differs in possessing stronger, coarser, raised spiral threads, not fine grooves (such that the surface of the shell has the feel of sandpaper); growth striae are much finer than the spiral threads.
Distribution. Members of the genus are found throughout the TWA in both near shore and offshore habitats. At least one species, Fenimorea fucata (Reeve, 1845), is widespread. Others, Fenimorea moseri (Dall, 1889) and Fenimorea petiti Tippett, 1995, are distributed on both sides of the Florida peninsula, but most species are more limited in their geographic range. See Plates 101–103 for graphical presentations of the known occurrences of species. Although widespread, more species rich and abundant than other drilliid genera, the genus Fenimorea appears to be found nowhere else except in the TWA.
description: Published as part of Fallon, Phillip J., 2016, Taxonomic review of tropical western Atlantic shallow water Drilliidae (Mollusca: Gastropoda: Conoidea) including descriptions of 100 new species, pp. 1-363 in Zootaxa 4090 (1) on pages 144-146, DOI: 10.11646/zootaxa.4090.1.1, http://zenodo.org/record/263299