Conasprella trianginodus (Harzhauser et. al., 2018)

Diagnosis:

Small Conasprella species with slender biconical shell, tall, coeloconoid, scalariform spire, striate sutural ramp and triangular, rounded beads along shoulder, last whorl elongate conical, strongly beaded at shoulder, with numerous broad spiral cords separated by narrow grooves, axial growth lines in interspaces. Subsutural flexure moderately shallow, slightly asymmetrically curved.

Description:

Shell small, elongate biconical, with tall, coeloconoid, scalariform spire. Protoconch partly missing. Teleoconch consisting of seven whorls, with broad, flat to weakly concave subsutural ramp, periphery placed a short distance above suture below whorl tapering in towards abapical suture, resulting in scalariform spire, strongly beaded along shoulder, beads triangular in side view, rounded in apical view. Spire whorls with four narrow spiral cords, interrupted and finely beaded by densely spaced opisthocyrt growth lines. Subsutural flexure moderately deep, asymmetrically curved. Last whorl strongly angular at shoulder, elongate conical, bearing 25 – 30 broad flattened spiral cords of irregular width, separated by interspaces widening abapically. Axial sculpture consisting of densely spaced growth lines, most prominent in interspaces, rarely interrupting and beading spiral cords. Weakly constricted at base with long, weakly recurved siphonal fasciole hardly delimited from base. Aperture narrow with parallel margins, outer lip incomplete. Spiral cords slightly lighter than interspaces under UV light, especially beaded cord along shoulder.

Remarks:

This species is reminiscent of Conasprella sondeiana (Martin, 1895), but differs in the less numerous, much coarser and triangular beads on carina and shoulder and the broader interspaces between the spiral cords of the last whorl. Moreover, it has delicate beads on the sutural ramp.

The extant Conasprella insculpta (Kiener, 1847), which occurs already during the late Miocene and Pliocene in the IWP (Tesch 1915, Shuto 1969), differs in its higher spire, the much more elongate last whorl and the regular spiral sculpture.

The late Miocene species from Brunei Darussalam belongs to the Conasprella orbignyi complex as defined by Puillandre et al.(2011). Conasprella orbignyi (Audouin, 1831), from the Plio-Pleistocene of the Philippines (Helwerda 2017) has a higher and straighter spire, with a larger distance between periphery and suture, less (13 vs. 15 on last whorl) and sharper beads on the shoulder, broader spaced growth lines and broader interspaces between the spiral cords of the last whorl.

Distribution:

Only known from the late Miocene of Brunei Darussalam.

Holotype: height: 19.6 mm, diameter: 7.4 mm, NHMW 2016/0313/0001 (Plate 10, Figs 9 –11), height: 19.6 mm, diameter: 7.4 mm.

Paratype: height: 15.9 mm, diameter: 7.0 mm, RGM.1309422 (Plate 10, Figs 19 – 21), leg. R.

Additional material: height: 13.5 mm, diameter: 6.0 mm, NHMW 2016/0313/0002, 2 specimens (GUBD), 2 juvenile specimens (R F5275).

Stratum typicum: Seria Fm.

Type locality: Ambug Hill, Brunei Darussalam.

Age: Late Miocene, Tortonian.

Name: Referring to the triangular nodes along the periphery