Paleochicoreus bicostatus ( Deshayes, 1835 ) Merle & Pacaud & Ledon & Goret, 2024

Merle, Didier, Pacaud, Jean-Michel, Ledon, Daniel & Goret, Bernard, 2024, New Cenozoic Muricidae (Mollusca: Gastropoda) from Europe, Geodiversitas 46 (15), pp. 495-551 : 502

Paleochicoreus bicostatus ( Deshayes, 1835) , n. comb. ( Fig. 2D, E )

Murex bicostatus Deshayes,1835: 602 , 603, no. 17, pl. 81, figs 28-30.

Pterynotus bicostatus – Vokes 1971: 23.

? Chicoreus bicostatus – Merle et al. 2011: 107, text-fig. 41a, b.

TYPE MATERIAL. — Holotype (by monotypy). France • Paris Basin , Val d’Oise , Valmondois ; Sables d’Auvers (biozone NP16); middle Eocene (lower Bartonian); UCBL-EM 33437 (Deshayes coll.); H: 21.5 mm (apex incomplete) ( Fig. 2D, E ).

TYPE HORIZON. — Sables d’Auvers (biozone NP16), see Gély & Lorenz (1991: pl. 1), middle Eocene (lower Bartonian).

TYPE LOCALITY. — France, Paris Basin, Val d’Oise, Valmondois (see Fritel 1910: 315).

DISTRIBUTION. — Only known from the type locality.

DESCRIPTION

Teleoconch of 21.5 mm in height (apex incomplete), of 13.2 mm in width, biconic in profile, composed of 3.5 preserved whorls. Moderately high spire with convex whorls. Last whorl up to 79% of total length of teleoconch. Apical angle 63°. Spiral sculpture with well-marked primary cords. Spire with P1 and P2 cords. Last whorl: IP, P1 to P6 (P6 placed on top of siphonal canal), ADP, MP and ABP; secondary cords (adis, abis, s3-s6, ads and ms). Axial sculpture not known on early teleoconch whorls. On spire and last whorl, three varices and between them two intervarices.Intervarices strongly developed. Intersection between axial and spiral sculpture displaying small nodules on IP, P1 to P5, ADP and MP. Intervarical nodules, present and more developed on P1 and P2. Ovate aperture of 24% of diameter, up to 64% of length of last whorl. Parietal lip smooth, adherent. Columellar lip smooth, slightly erect. Anal notch deep. Parietal callus well developed. Outer lip showing internal denticles: ID stronger than D1, D2 and D3, D4, D5 and D6 stronger than D1 to D3, D6 split. Siphonal canal of 50% of apertural length. Pseudoumbilicus narrow.

COMPARISONS

No new specimens of this species have been found since its original description byDeshayes (1835). Cossmann & Pissarro (1911: pl. 36, fig. 170bis-1) attributed an eroded specimen (MNHN.F.J02588 refigured inMerle et al. 2022:pl. 147, fig.4a, b) to this species under the name Ocenebra (Ocinebrina) bicostata ( Deshayes,1835) .However,re-examination of this specimen ( Merle 1999) reveals that it represents Eofavartia subrudis (d’Orbigny, 1850) . Paleochicoreus bicostatus ( Deshayes,1835) , n. comb. shares with P. newtoni ( Eames, 1957) and P. initialis ( Vokes, 1990) , n. comb. an aperture with developed internal denticles, a strong parietal callus, and a deep anal notch. P.newtoni differs in having a slenderer shape and lower, less coarse intervarices. In P. initialis n. comb., the intervarices are also lower than in P. bicostatus ( Deshayes, 1835) , n. comb. Paleochicoreus packardi ( Dickerson, 1915) is poorly preserved (see Merle et al. 2011), but it bears slightly winged varices as do P. newtoni and P. initialis n. comb. Paleochicoreus diderrichi ( Vincent,1913) displays well developed denticulation within the outer lip(see Merle et al. 2011: fig.41.3). Paleochicoreus bicostatus ( Deshayes, 1835) , n. comb. differs from these species in lacking winged varices. However, the holotype is eroded and in the early Bartonian (Auversian) from the Paris Basin, many species tend to lose their delicate ornaments (wings, spines) and thicken their shell, as is the case in another muricid, Eofavartia subrudis ( Deshayes, 1835) .

Figures

FIG. 2. — Spiral cords and internal denticles of the outer lip in Paleochicoreus Merle, n. gen.: A, B, Paleoochicoreus initialis (Vokes, 1990), n. comb., holotype, USNM450376, Nacodoches, Texas (United States), middle Eocene (Lutetian); C, P. newtoni (Eames, 1957), holotype, BMNH G41982, Ombralla, Nigeria, middle Eocene;D, E, P. bicostatus (Deshayes,1835), n. comb., holotype, UCBL-EM 33437 (Deshayes coll.), Valmondois,Val d’Oise, Paris Basin, France, middle Eocene (Bartonian). Scale bars: 10 mm. Credits: A, B, Y. Villacampa and J. Jorstad (USNM); C, S. Tracey (NHM); D, E, P. Loubry (MNHN/CNRS).