Pronucellopsis Merle, 2024

Merle, Didier, Pacaud, Jean-Michel, Ledon, Daniel & Goret, Bernard, 2024, New Cenozoic Muricidae (Mollusca: Gastropoda) from Europe, Geodiversitas 46 (15), pp. 495-551 : 540

Genus Pronucellopsis Merle , n. gen.

urn:lsid:zoobank.org:act:57351378-2B58-4F05-8CC1-C8DE453B321B

TYPE SPECIES. — Pronucellopsis pacaudi Merle, Ledon & Goret , n. sp. by present designation.

INCLUDED SPECIES. — Pronucellopsis pacaudi Merle, Ledon & Goret , n. gen., n. sp., Paris Basin, France; Paleocene (Thanetian).

DIAGNOSIS. — Subfusiform teleoconch with rounded whorls. Poorly marked cords. No IP. P6 weak, not atrophied. ADP, MP weak. Secondary cords (s1, s2, s3, s4) appearing late in ontogeny. Primary cords P3 to P6 appearing after third whorl. Varices formed by one or two abaxial lamellae on early whorls, occasionally reinforced by several lamellae on succeeding whorls. Number of varices: between 13 and 15. Weak, rounded shoulder sinus. Posterior sinus on sutural ramp deep. Internal denticles usually weak: ID missing. D1 stronger than D2. D6 present. Columellar lip smooth. Siphonal canal narrow. Microstructure of three aragonite layers.

COMMENTS

Pronucellopsis Merle , n. gen. is the sister taxon of Nucellopsis (clade E, Fig. 1 ). Both taxa share a weak or missing shoulder sinus. Pronucellopsis Merle , n. gen. is easily differentiated in having a more elongated shape and poorly developed internal denticles. It also displays poor development of the spiral cords which always remain weak and appear late in ontogeny. This feature is present in early muricids from the Paleocene (e.g., Poirieria or Flexopteron ) and seems a plesiomorphic character.

Figures

FIG. 1. — Strict Consensus tree of 7 equally parsimonious trees (length 107, ci 0.53, ri 0.78) generated by Winclada and computed using the option Heuristic Analysis (mult* max*), all characters non additive.