Haustator incrassata (Sowerby, 1814)

Haustator incrassata (Sowerby, 1814)

( Fig. 5H View FIG 1-H View FIG 3 View FIG , I 1-I View FIG 3 View FIG )

Turritella incrassata Sowerby, 1814: 111 View in CoL , pl. 51, fig. 6.

Turritella (Haustator) incrassata View in CoL – Harmer 1925: 446, pl. 42, figs 1-3, 5-7, pl. 43 fig. 16.

Haustator incrassata – Van Dingenen et al. 2016: 117, pl. 3, fig. 1.

Turritella incrassata View in CoL – Moerdijk et al. 2018: 27, figs 6-8.

For more, see synonymy list in Van Dingenen et al. (2016).

MATERIAL AND DIMENSIONS. — Maximum height 42.4 mm, width 11.5 mm. — RGM.1365074 (700+) leg. AWJ ; RGM.1365285 (1), leg AWJ , RGM.1310833 (1), leg. AWJ ; RGM.1364908 (140+) leg. WG ; RGM.1364974 (200+) leg. ACJ ; RGM.1365085 (4), leg WG .

SPECIES CHARACTERISATION. — Medium sized Turritella species; protoconch paucispiral of about 1.5 smooth whorls; teleoconch of about 12 whorls with tricostate sculpture, primaries starting in order C-B-A (terminology following Harzhauser & Landau 2019), B and C stronger resulting in bicarinate early whorl profile. Numerous fine and irregular threads appear from fifth whorl onwards. Abapically primary cords flatten and broaden giving whorls a flattened appearance. Base moderately convex, with about five irregular, widely spaced spiral cords, with secondary cords of variable strength intercalated. Lateral sinus on adapical half whorl, steep around ~38° angle and simple abapical inflection. Basal sinus shallow, almost absent, opisthocyrt. Aperture subquadrate, higher than wider.

DISTRIBUTION. — Lower Pliocene: NSB, Coralline Crag Formation, England ( Wood 1848; Harmer 1918); Atlantic, NW France ( Van Dingenen et al. 2016). — Upper Pliocene: NSB, Red Crag Formation, England ( Wood 1848; Harmer 1918); Oorderen and Kruisschans Members, Belgium ( Marquet 1997, 1998), Oosterhout Formation, The Netherlands ( Moerdijk et al. 2018). — Upper Pliocene: Atlantic, St Erth, England (Harmer 1918), Selsoif, NW France (this paper).

REMARKS

Marwick (1957) highlighted the importance in the order of appearance of the cords on the neanic whorls and used a lettering system for the spiral cords in which B was the medial primary, D the peribasal primary generally involved with the suture, A was the first to appear adapical to B and C the first to appear abapical to B, between B and d ( Marwick 1957: 148), and the shape of the lateral and basal sinuses. Subsequently, this work has been neglected by almost all European workers. More recently, Harzhauser & Landau (2019) applied Marwick’s model and proposed generic attributions for European fossil turritellids from the Paratethys. Following the diagnostic generic characters proposed in that work, the Selsoif specimens are readily attributed to Haustator de Montfort, 1810 . These characters are order of appearance of primary spiral cords C-B-A, and lateral sinus with inflection points.

Based on the whorl profile and adult sculpture we attribute these specimens to H. incrassata (Sowerby, 1814) . This species is highly variable in the development and strength of the spiral sculpture, which has led to the creation of many synonyms. Compared to specimens from other Pliocene sites such as Le Pigeon Blanc (NW France) ( Van Dingenen et al. 2016) or from the Pliocene Coralline and Red Crag Formations of eastern England, and Pliocene units from Belgium and the Netherlands (Harmer 1925; Marquet 1998; Moerdijk et al. 2018), the Selsoif specimens tend to be straight-ided to slightly concave with fine slightly irregular spiral cordlets. The relative smoothness of the later whorls is reminiscent of the endemic Early Pliocene NSB Haustator vanderfeeni (Brakman, 1937) . The order of appearance of the primary cords places that species also in Haustator , however, it has even flatter whorls separated by a more superficial suture, and the whorl profile between the primary cords is concave. Pleistocene records for the Netherlands (e.g., Van Regteren Altena et al. 1955) are not supported by in situ findings (FW pers. observation) and are not included in the distribution.