Timbellus calciacus Merle, Pacaud, Ledon & Goret, 2024, n. sp.
Creators: name: Merle, Didier
name: Pacaud, Jean-Michel
name: Ledon, Daniel
name: Goret, Bernard
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Neogastropoda
Muricidae
Timbellus
Timbellus calciacus

description: Timbellus calciacus n. sp.
(Figs 10 A-D; 26C, D)
urn:lsid:zoobank.org:act: E83D9D22-2B5E-4B2A-9693-8568559FA8D4
Pterynotus tripteroides – Merle 1990: 185, pl. 4, fig. 3 only [non Lamarck, 1822].
TYPE MATERIAL. — Holotype. France • Paris Basin, Val d’Oise, Chaussy (Les Garennes); Falun de Chaussy (biozone NP15); middle Eocene (middle Lutetian); MNHN.F.A90536 (Merle coll.), H: 8 mm (Figs 10A, B; 26C).
Paratypes. France • 3 spm; same as for the holotype; MNHN.F.A90537 (Figs 10C, D; 26D, H: 12 mm), MNHN.F.A90538, MNHN.F.A90539 (Merle coll.) • 1 spm; idem; MNHN.F.R61443 (Merle coll.), figured specimen of Merle (1990: pl. 4, fig. 3) • 1 spm; Paris Basin, Yvelines, Beynes (Ferme de l’Orme); middle Lutetian; MNHN.F.A90535 (Merle coll.).
ETYMOLOGY. — Calciacus (Latin adjective): from the ancient name of the village of Chaussy given in 690. Name given in apposition.
TYPE HORIZON. — Falun de Chaussy (biozone NP15), see Gély & Lorenz (1991: pl. 1), middle Eocene (middle Lutetian).
TYPE LOCALITY. — France, Paris Basin, Val d’Oise, Chaussy (Les Garennes), see Fritel (1910: 88).
DISTRIBUTION. — Faluns de Chaussy and Calcaire à Orbitolites at La Ferme de l’Orme (biozone NP15), Paris Basin (France), middle Eocene (middle Lutetian only).
DESCRIPTION
Bulbous protoconch of 1.2 whorls.Teleoconch up to 12 mm in height, up to 5.5 mm in width, biconic in profile, composed of four whorls. Moderately high spire. Last whorl up to 76% of total length. Apical angle 71° including winged varices, up to 55° excluding them. Spiral sculpture with poorly marked primary cords. First whorl: appearance of very weak P1, P2 and P3. Second whorl: weak P1 to P3. Third whorl: appearance of weak s1, s2 and threads covering base of whorl. Fourth whorl: P1 to P6 weak, ADP on siphonal canal, secondary cords undistinguishable from threads; threads covering entire surface of shell. On first whorl, axial sculpture with 8-9 lamellose protovarices. On second whorl: appearance of varices (three varices and one low intervarix between two varices). From third to last whorl, numerous growing microlamellae covering surface of shell and forming delicate, reticulate sculpture covering surface of shell. Intervarical relief very low, but slightly higher on P1-P2. Varices well winged on last two whorls. Appearance of short P1 spine on second whorl. On last whorls, axial ornamentation forming winged varices, rounded in outline, without evidence of spines, even on P1. Subtriangular aperture up to 33% of diameter and up to 74% of length of last whorl (including siphonal canal). Columellar lip smooth, narrow, slightly erect anteriorly and forming a curved inductura at base. Parietal lip slightly adherent. Outer lip with very weak denticles including D1 to D5. Siphonal canal open, up to 45% of apertural length. Pseudo-umbilicus narrow.
COMPARISONS
This small species was never distinguished from its congeners in the Paris Basin, probably mistaken for juveniles of T. tripteroides (Lamarck, 1822), with which it co-occurs at two localities: Chaussy and La Ferme de l’Orme. With a maximum height of 12 mm, T. calciacus n. sp. is a very small Timbellus. Timbellus calciacus n. sp. differs from juveniles of T. tripteroides in having the aperture completely formed and by having a peculiar reticulate microsculpture (see Fig. 6C, D). This last character lacks in specimens of T. tripteroides at any growth stage. Specimens of T. occidentalis n. sp. from the upper Lutetian of Normandy and the early Bartonian of Loire-Atlantique share with T. calciacus n. sp. a small size, but T. occidentalis n. sp. is double the size (H: 26.6 mm vs 12 mm). As with T. tripteroides, T. occidentalis n. sp. lacks the peculiar microsculpture found in T. calciacus n. sp.
description: Published as part of Merle, Didier, Pacaud, Jean-Michel, Ledon, Daniel & Goret, Bernard, 2024, New Cenozoic Muricidae (Mollusca: Gastropoda) from Europe, pp. 495-551 in Geodiversitas 46 (15) on pages 513-514, DOI: 10.5252/geodiversitas2024v46a15, http://zenodo.org/record/13985760