DRILLIIDAE Olsson, 1964

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 : 13

DRILLIIDAE Olsson, 1964

Diagnosis. According to Kilburn (1988: 172): species with a claviform shell facies (tall spire, truncated base, and parietal lobe) that possess a drilliine radula, formula 1-1-R-1-1 with rachidians small to large, laterals broad arched and pectinate, marginals long, sharply pointed, with axial ribs as the dominant sculptural element, and operculum oblanceolate with a terminal nucleus. Taylor et al. (1993) included some additional morphological detail in their diagnosis: sculpture usually well developed, anal sinus deep, located on the shoulder, sometimes made sub-tubular by a parietal lobe; protoconch smooth, sometimes carinate.

Remarks. The most distinguishing characteristic of the Drilliidae is the structure of the radula. However, the radula has been examined for only a few of the TWA drilliid taxa (Taylor et al., 1993; Maes, 1984; and Tippett, 1995), so genera have been included in the family on a more convenient combination of shell morphology and anatomical examination in the most recent published works (Bouchet et al., 2011, and Puillandre et al., 2011). Shell characteristics common to all TWA Drilliidae are:

1. A fusiform shell, truncated anteriorly in most genera, usually glossy, with a tall spire, and a large last whorl usually 50% or more of the total shell length;

2. Smooth protoconch of 1½–3 whorls. A median carina present in some;

3. Sculpture primarily of axial ribs; some genera with spiral grooves, incised lines, or threads that may be between or override ribs; subsutural cord absent;

4. Surface microsculpture of spiral grooves or threads present on at least part of the shell surface in all but a single genus ( Lissodrillia ); incremental growth lines can be absent, microscopic or strong;

5. Anal sinus on whorl shoulder adjacent to suture, shallow to moderately deep, usually U-shaped;

6. Parietal callus or lobe at the posterior end of the aperture beside the anal sinus; and

7. Varix present in fully developed individuals.

Characters are identified that are diagnostic for each genus so that species may be properly placed. Most TWA genera have been fairly well defined by past workers; however, additional characteristics that distinguish one from another, such as shell surface microsculpture, have been added to their diagnoses.

Key to genera. The following key to shallow water western Atlantic drilliids is based on some aspects of shell form and detail of sculpture: axials, spirals, varix form and position, and microsculpture (growth increments or very fine striae and spirals, which may be grooves and/or threads). Some species may only marginally fit for the described character in this key. Confirmation of a species placement or clarification of characteristics of a genus can be made by reviewing the key characteristics paragraph in the introduction to that genus.

1. Sculpture includes strong spiral elements.................................................................. 2. - Shell mostly smooth with just axial ribs, or spirals, if present, much less prominent than ribs......................... 5. 2. Protoconch whorls smooth............................................................................. 3. - One or all protoconch whorls carinate.............................................................. Calliclava 3. Varix ½-turn from edge of outer lip, dorsum of last whorl lacking ribs.................................... Agladrillia - Varix about ⅓-turn from edge of outer lip................................................................. 4. 4. Shoulders tabulate or angular.................................................................. Clathrodrillia - Shoulders round, spirals usually very fine........................................................... Bellaspira 5. Fine spiral grooves present over most of the teleoconch surface................................................ 6. - Microscopic spirals mostly restricted to last whorl or anterior fasciole........................................... 8. 6. Spirals and striae subequal and closely spaced, but not packed.......................................... Fenimorea - Spirals larger than growth striae, either packed, or widely spread............................................... 7. 7. Spirals are widely spaced incised lines. Very shallow anal sinus.......................................... Bellaspira - Spirals packed together; anal sinus a deep notch................................................... Decoradrillia - Spirals of raised threads, coarse, shell feels sandpapery................................................. Neodrillia 8. Ribs run suture-to-suture with only a slight change in sulcal area............................................... 9. - Ribs end at sulcus, or evanesce near suture on later whorls................................................... 10. 9. Microscopic spirals between ribs of last whorl, may be very faint..................................... Syntomodrillia - Spirals on anterior fasciole only................................................................. Leptadrillia - Spirals absent altogether........................................................................ Lissodrillia 10. Varix ⅓-turn from edge of outer lip, not visible in ventral view......................................... Splendrillia - Varix prominent, visible when shell is viewed ventrally, ¼-turn or less.......................................... 11. 11. Ribs usually to suture of later whorls; protoconch 1¾–2 whorls......................................... Cerodrillia - Ribs usually absent in sulcus of later whorls; protoconch 2½–3 whorls................................... Douglassia