Neodrillia Bartsch, 1943

Fallon, Phillip J., 2016, Taxonomic review of tropical western Atlantic shallow water Drilliidae (Mollusca: Gastropoda: Conoidea) including descriptions of 100 new species, Zootaxa 4090 (1), pp. 1-363 : 261

Genus Neodrillia Bartsch, 1943

Type species: Neodrillia cydia Bartsch, 1943 by original designation (Recent, off Fowey Light, Miami-Dade County, E Florida).

Diagnosis. According to Bartsch (1943: 83–84), broadly conic shell, protoconch 2½ whorls, the last with closely spaced hair-like axial threads, teleoconch with strong axial ribs, weak in the anal sinus, evanescent on the shell base. Ribs are overridden by axial striae and crossed by strong spiral threads, about the same distance apart as their interspaces, imparting a screen-like texture to the shell surface. The anterior fasciole has stronger spiral than axial threads. The outer lip has a weak stromboid notch and a strongly channeled anal notch; the anterior canal strongly channeled. A heavy varix lies about ⅓-turn behind the edge of the outer lip. The inner lip is appressed to the columella and forms a knob on the parietal wall at the junction with the outer lip.

Key characteristics. The combined presence of all the following characteristics is diagnostic of Neodrillia and separates the genus from other TWA drilliid genera:

1. Shell surface microsculpture of raised spiral threads, spaced two or more times their width, made coarse by

microscopic growth striae.

2. Anal sinus deep, slightly constricted at its entrance, and offset from the shell’s axis by the parietal lobe and

outward curve of outer lip, such that it appears spout-like;

3. Ribs narrow to broad, run from suture-to-suture on spire whorls, reduced in the sulcus in later whorls, and

evanescent on shell base; and

4. Varix heavy, wider and higher than adjacent ribs, positioned about ⅛–⅓-turn from the edge of the outer lip.

Because Neodrillia is a relatively small genus, generalizations are necessarily tentative. Species fall into two separate and distinctly different morphological “ types ” that are linked to their habitat (although expressed differently) as is possibly the case in Fenimorea . The shallow water species, Neodrillia cydia Bartsch, 1943 , has a shorter spire and broad ribs, while the deep water species (> 50 m), such as Neodrillia princeps , new species, have tall spires and narrow ribs.

Nomenclatural notes. Although the genus Drillia Gray, 1838 ( Drillia umbilicata Gray, 1838 type species by subsequent designation, Gray, 1847) was well known to Bartsch, he did not believe the genus Drillia was applicable to species he put in Neodrillia because they did not conform to the type of the genus (Bartsch, 1943: 82). (Tippett, 2006 later demonstrated that Bartsch’s specimen of D. umbilicata was actually D. dunkeri Knudsen, 1952 [= D. knudseni Tippett, 2006 ], which is a typical Drillia , so Bartsch’s analysis of the genus remains unchanged.) Instead, he erected Neodrillia (Bartsch, 1943: 82–90) for a group of very similar species (later all synonymized under Neodrillia cydia Bartsch, 1943 by Abbott, 1958: 96) that differ from Drillia in possessing a more complex shell microsculpture of fine axial growth striae and stronger spiral threads, giving the surface a “cloth-like” or “screen-like texture”, not the spiral threads of Drillia , by the absence of a false umbilicus, and by the presence of a 2-whorl protoconch. Drillia , on the other hand, as exemplified by D. knudseni Tippett, 2006 from West Africa (the species mistakenly identified as D. umbilicata Gray by Bartsch), is described by Bartsch (1943: 82) as having a protoconch of 3 smooth whorls, strong axial ribs not diminished in the region of the sulcus of the early postnuclear whorls, only from the 5th whorl on, aligned from whorl-to-whorl, and with numerous heavy growth striae and well defined spiral threads, and the presence of a narrow open umbilicus on the anterior half of the columella. These characteristics are sufficient to separate the African Drillia from the W Atlantic species at the genus level.

Similar genera. Fenimorea and Clathrodrillia are similar in some respects to Neodrillia . Fenimorea has a different microsculpture; spiral threads are much finer, sub-equal to growth striae. The shell surface appears and feels smooth, and may be glossy in species with even finer microsculpture, not dull with a sandpaper-like feel as in Neodrillia . Clathrodrillia also has a different shell microsculpture. It consists of spiral incised grooves that may be close, creating the appearance of heavy spiral threads, or of overlapping bands when further apart. Whorls are usually turreted in Clathrodrillia , but not so in Neodrillia .

Distribution. Neodrillia cydia is the most abundant member of the genus and distributed throughout the TWA, although rarely appearing in the Gulf of Mexico. It is a very successful component of the molluscan shallow reefal communities and the most widespread of the Drilliidae in the TWA region. Its congeners, which inhabit deeper water (mostly> 100 m), have so far been taken from more restricted ranges.