Cerodrillia brunnea, Fallon, Phillip J., 2016

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 : 62-63

Cerodrillia brunnea , new species

( Plate 24 )

Type material. Holotype 5.7 x 2.3 mm (USNM 1291329); 4 paratypes from the type locality: 3 spec., 6.6 x 2.4, 6.4 x 2.5 & 6.1 x 2.4 mm (P. Stahlschmidt coll.); 1 spec., 4.5 x 1.9 mm (author’s coll.).

Type locality. Off Escudo de Verguas I., Bocas del Toro Province, Panama, in 250 m. Range and habitat. Known only from the type locality.

Description. Shell very small (to 6.6 mm in total length), glossy, fusiform with a truncated anterior; whorls convex, peripheries approximately mid-whorl, last whorl large, (approximately 59% of total length), asymmetrical, right side (when viewed ventrally) swollen by varix; sculpture of broad ribs. Protoconch of 1¾–2 smooth whorls, the first partially immersed in the second. Axial sculpture of broad ribs that extend from suture-to-suture, and to anterior fasciole on last whorl; little changed in sulcus, just slightly curved and excavated on ventral side. Ribs about as wide as intercostal space; number 11–14 on the penultimate and 10–11 on the last whorl to the varix; rib crests are ridged, not round. Light growth striae present on teleoconch, heaviest on last whorl. Sulcus obscure, but with ribs slightly recurved and excavated on their ventral side, and with growth striae that are recurved to reflect outline of anal sinus. Varix is cup handle-like, located behind the anal sinus, about ¼-turn from the outer lip. Spiral sculpture absent except for 7 weak spiral threads on base anterior to whorl periphery and 7 ridges on anterior fasciole. Outer lip thin, projects outward from varix; with 3 irregular strengthening axial folds between the varix and edge of outer lip. Edge of lip forms a flattened arc from anal sinus to anterior canal. Stromboid notch shallow. Anal sinus on whorl’s shoulder, deeply notched, apex round, sides parallel; sinus angled away from shell axis by the parietal lobe on one side and the slight outward bend of the outer lip on the other. Inner lip narrow; margined, thicker anteriorly, thin on the parietal wall, developed into a weak lobe on one side of anal sinus. Anterior canal straight, short and open; without a notch. Anterior fasciole not swollen. Color a uniform light golden brown.

Remarks. Taxonomy. Cerodrillia brunnea has all of the diagnostic traits of Cerodrillia : ribs from suture-tosuture, a cup-handle-like varix just behind the anal sinus, and spiral sculpture limited to the shell base and anterior fasciole. Variability. The 5 examined shells are fairly uniform; their average total length is 5.86 mm (4.5–6.6 mm) and average W/ L ratio 0.391. Identification. Cerodrillia brunnea is not easily confused with its known congeners. It is one of the smallest among its congeners, although Cerodrillia minima , new species is even smaller, but has a longer anterior canal, ribs that have round crests, not ridged, and is similarly colored but translucent. Because of its small size it may be mistaken for some Syntomodrillia with ribs that run little changed from suture-to-suture that are ridged, and with spiral threads in intercostal space. The difference is that the threads run over the axials, not just between them, and the clearly distinguishing characteristic of a cup-handle-like varix behind the anal sinus is present and a strong indicator of the species’ affinity with genus. The varix of the genus Syntomodrillia is positioned further back from the edge of the outer lip, at ⅓-turn.

Etymology. The Brown Cerodrillia from the Neo-Latin adjective brunneus, feminine brunnea , meaning brown. Named for the uniform color of known specimens.

Figures

PLATE 24. Cerodrillia brunnea, new species. Figs. 1 – 3: holotype, off Escudo de Veraguas I., Panama (USNM 1291329). Fig. 1: ventral, lateral & dorsal views; Fig. 2: enlarged view of protoconch (not to scale); Fig. 3: apical view, V = varix, L = edge of outer lip. Figs. 4 – 6: paratypes from the type locality (P. Stahlschmidt coll.).