Timbellus submicropterus 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 submicropterus

description: Timbellus submicropterus n. sp.
(Figs 16 A-H, K; 27A-D)
urn:lsid:zoobank.org:act: 77B79E49-DDB1-413B-983A-A19753441F55
Murex (Pterymurex) tricarinatus – Cossmann & Pissarro 1901: 128, pl. 14, fig. 1 [non Lamarck, 1803].
Timbellus micropterus – Merle et al. 2011: 448, pl. 102, fig. 4a, b only [non Deshayes, 1865].
TYPE MATERIAL. — Holotype. France • Normandy, Manche, Fresville; Calcaire de Fresville; middle Eocene (uppermost Lutetian); MNHN.F.A24111 (MNHN coll.), H: 23.6 mm (Figs 16A, B; 27A).
Paratypes. France • 1 spm; same as for the holotype; UCBL-EM 33438 (Bourdot coll., figured specimen of Cossmann & Pissarro 1901)(Figs 16E, F; 27C) • 1 spm; idem; MNHN.F.A90556 (MNHN coll.) (Fig. 16K) • 1 spm; idem; MNHN.F.B63700 (de Morgan coll.) • 1 spm; Normandy, Manche, Gourbesville; Calcaire de Fresville; upper Lutetian; MNHN.F.A24126 (Munier-Chalmas coll.), figured specimen of Merle et al. (2011: 135, pl. 102, fig. 4a, b) (Figs 16C, D; 27B).
ADDITIONAL MATERIAL (material referring to Timbellus cf. submicropterus n. sp.). — France • 3 spm; Loire-Atlantique, Loire Basin, Saffré (Bois Gouët); middle Eocene (lower Bartonian); MNHN.F.A29660 (Pacaud coll.) • 2 spm; Saint-Aignan-GrandLieu (Pierre-Aiguë), Loire-Atlantique; idem; MNHN.F.A29662, (Brébion coll.),MNHN.F.A90557 (Brébion coll. (Figs 16G, H; 27D).
ETYMOLOGY. — Name formed by the prefix sub- and micropterus for this species older than Bartonian Timbellus micropterus (Deshayes, 1835).
TYPE HORIZON. — Calcaire de Fresville, middle Eocene (uppermost Lutetian), see Bignot et al. (1968).
TYPE LOCALITY. — France, Normandy, Manche, Fresville, see APGN (2024).
DISTRIBUTION. — Normandy (Calcaire de Fresville) middle Eocene (uppermost Lutetian) and? Loire Basin (Sables du Bois-Gouët), lowermost Bartonian, see Mathelin & Bignot (1989).
DESCRIPTION
Bulbous protoconch of one whorl (Fig. 16K). Teleoconch up to 23.6 mm in height, up to 11.6 mm in width, biconic in profile, composed of six whorls. Moderately high spire. Last whorl up to 70% of total length. Apical angle 59°. Spiral sculpture with coarse primary cords. First to third whorl: no cord. Fourth whorl: appearance of weak P1, s1 and P2. Fifth whorl: P1, s2 and P2 coarser. Sixth whorl: P1 to P6, s1; P6 not atrophied on convex part of whorl; ADP, MP and ABP on siphonal canal. From first whorl to second whorl: 6-7 protovarices. On third whorl: appearance of varices; three varices and one intervarix intercalated. From third to sixth whorl: no change. Higher relief of intervarices on P2. Varices rather thick. Appearance of short P1 spine on third whorl. Ovate aperture up to 27% of diameter and up to 71% of length of last whorl (including siphonal canal). Columellar lip smooth, narrow, poorly erect anteriorly, forming curved inductura at base. Parietal lip slightly adherent. Outer lip with developed denticles including ID, D1 to D6. D 6 in some specimens. Outer lip not crenulate. Siphonal canal open, straight, up to 40% of apertural length. Pseudoumbilicus narrow.
COMPARISONS
A specimen of this species (Figs 16E, F; 27C) was identified as Murex (Pterymurex) tricarinatus Lamarck, 1803 (synonym of Timbellus crenulatus tricarinatus) by Cossmann & Pissarro (1901). Timbellus crenulatus tricarinatus differs greatly by apertural (with weak internal denticles within the outer lip), sculptural and shape characters, and belongs to another group species (see above Fig. 14). In fact, this specimen illustrated by Cossmann & Pissarro (1901) more closely resembles T. micropterus from the Bartonian Paris Basin. Merle et al. (2011) attributed another Norman specimen (pl. 102, fig. 4a, b) to T. micropterus (Figs 16C, D; 27B). It is true that these two specimens are superficially similar to T. micropterus, but further comparison reveals some differences, such as only one intervarice (instead two in typical T. micropterus) and finer secondary cords on the last whorl. The bivariate plot of total length against width (Fig. 17) does not suggest strong differences Normandy and Paris Basin populations. Finally, it is tempting to conclude that the observed teleoconch differences in T. submicropterus n. sp. fall within the intraspecific variation of T. micropterus. However, T. submicropterus n. sp. has a paucispiral protoconch, whereas T. micropterus has a multispiral (Fig. 16K, L), suggesting two separate species with different modes of larval development. In the Bartonian from Loire-Atlantique, there are specimens showing coarse spiral cords like those of typical T. submicropterus n. sp., but they bear a more pronounced shoulder (Fig. 16G, H). Their protoconch is not preserved. We therefore attribute these specimens to T. submicropterus n. sp. with hesitation.
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 521-522, DOI: 10.5252/geodiversitas2024v46a15, http://zenodo.org/record/13985760