Pterynotus (Pterymarchia) gaasensis 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
Pterynotus
Pterynotus gaasensis

description: Pterynotus (Pterymarchia) gaasensis n. sp.
(Figs 18 A-D; 27E, F)
urn:lsid:zoobank.org:act: B1E15CF2-7B4F-4D02-8F34-1D5848D596F5
Murex quadrifrons – Grateloup 1845: pl. 3 [pl. 31], fig. 10 [non Murex quadrifrons Lamarck, 1822].
Pterynotus (Pterymarchia) cf. subquadrifrons – Merle et al. 2011 (partim): pl. 90, figs 3-74 only.
Pterynotus cf. subquadrifrons – Lozouet 2023: 21, pl. 17, figs 1-9, text-fig. 10E.
TYPE MATERIAL. — Holotype. France • Aquitaine Basin, Landes, Gaas (Espibos); Gaas Formation (biozone NP23); early Oligocene (Rupelian); MNHN.F.A32492 (Merle coll.), figured specimen in Merle et al. (2011: pl. 90, fig. 3), H: 27 mm (Figs 18A, B; 27E). Paratypes. France • 6 spm; same as for the holotype; MNHN.F.A77749 (Merle coll.) • 1 spm; idem; MNHN.F.A90554 (Merle coll.) (Figs 18C, D; 27F) • 1 spm; idem; MNHN.F.A86913 (Lozouet coll.), figured in Lozouet (2023: text-fig. 10a, b).
ADDITIONAL MATERIAL. — France • 1 spm; Aquitaine Basin, Landes, Gaas (La Gouarde); same as for the holotype; Aucoin coll., figured in Merle et al. (2011: pl. 90, fig. 4a, b).
ETYMOLOGY. — From the type locality, Gaas (Landes), France.
TYPE HORIZON. — Gaas Formation (biozone NP23), see Sztrákos & Steurbaut (2017: 752), early Oligocene (Rupelian).
TYPE LOCALITY. — France, Aquitaine Basin, Landes, Gaas (Espibos), see Sztrákos & Steurbaut (2017: 752).
DISTRIBUTION. — Aquitaine Basin (France), early Oligocene (Rupelian).
DESCRIPTION
Paucispiral protoconch (fide Lozouet 2023: text-fig. 10e). Teleoconch up to 27 mm in height, up to 12 mm in width, biconic in profile, composed of six whorls. Moderately high spire, first two whorls subcarinate; next whorls rounded. Last whorl up to 75% of total length. Apical angle 56°. Spiral sculpture with marked primary cords. First whorl: appearance of primary cords P1 and P2; second whorl: P1 and P2; third whorl: appearance of s1. Fourth whorl: appearance of abis, adis and s2. Fifth whorl: no change or appearance of threads. Sixth whorl: IP, adis and abis, P1 to P6, s1 to s6; s2 and s3 well developed; P6 on base on convex part of whorl; ADP, MP and ABP slightly more developed than ads and ms. Surface of shell with numerous threads appearing on fourth whorl. Axial sculpture with thick varices. On first whorl: nine lamellose varices. From the second to fifth whorl: 9-10 thick varices. On sixth: appearance of three or four varices and one intervarices intercalated. Varices and intervarices thick. From the third to last whorl, numerous, fine microlamellae covering entire surface forming scabrous microsculpture. Ovate aperture up to 25% of diameter and up to 66% of length of last whorl (including siphonal canal). Columellar lip, adherent posteriorly, becoming progressively more erect anteriorly. One or two small columellar tubercles. Parietal lip adherent. Outer lip bearing strong internal denticles: ID, D2 to D6 present, D1 missing. Pseudoumbilicus moderately large. Siphonal canal open, up to 48% of apertural length, slightly dorsally recurved.
COMPARISONS
Merle et al. (2011: pl. 90, figs 3-4) attributed with hesitation two specimens from Gaas to Murex subquadrifrons d’Orbigny, 1852, originally described as Murex quadrifrons by Grateloup (1845) from this same Rupelian locality. The Grateloup’s collection is housed in the University of Talence, but the type material of M. quadrifrons was not found and is likely lost (personal observation of the first author). Therefore, only the drawing of Grateloup (1845: pl. 3 [pl. 31], fig. 10, refigured in Merle et al. 2011: pl. 90, fig. 2) can be used to identify the species. According to Merle et al. (2011), the drawing shows a shell with a textiliose surface and a biconic shape, as in the Gaas material at hand. Moreover, to our knowledge, no other muricid from Gaas except P. (Pterymarchia) is comparable to the specimen illustrated by Grateloup (1845). However, the shell illustrated by Grateloup (1845) lacks internal denticles within the outer lip, lacks columellar denticles, shows more numerous varices (six on the ventral face vs four in the specimens at hand), has a narrower siphonal canal, and is more likely to represent a specimen of Favartia. These numerous differences between Grateloup’s (1845) figure and the studied material suggest that it obviously corresponds to a species other than M. subquadrifrons. Murex subquadrifrons is therefore not recognizable using the figure of Grateloup, lacks type material and it should be considered a nomen dubium.
Eocene Pterynotus (Pterymarchia), such as P. (P.) antiquus (Merle 1990), P. (P.) denudatus (Deshayes, 1835) and P. (P.) defensus (Fuchs, 1870) strongly differ from the P. (P.) gaasensis n. sp. in having trivaricate sculpture. Pterynotus (P.) fascistria (von Koenen, 1889) from the Priabonian of North Germany is more similar shape, as it lacks trivaricate sculpture and because their primary cords are poorly distinguishable from the secondary cords on the last whorls. Pterynotus (P.) fascistria is distinguished from P. (P.) gaasensis n. sp. in having a lower spire and by lacking intervarices, D1 and ID denticles. Pterynotus (P.) gaasensis n. sp. can be compared to two other Neogene species: P. (P.) pelouatensis n. sp. from the Burdigalian of Aquitaine Basin (Figs 18 EH; 27G, H) and P. (P.) sandbergeri (Hörnes, 1856) from the Langhian of the Paratethys. Both species differs from P. (P.) gaasensis n. sp. in having more angular whorls with a shoulder delimited by a subspiny P1 and by other primary cords more distinguishable from the secondary cords on the last whorl. Lozouet (2023) followed Merle et al. (2011) and adopted the name Pterynotus cf. subquadrifrons for the Rupelian material from Gaas, but he did not include Chattian and Aquitanian specimens figured in Merle et al. (2011: pl. 90, figs 5, 6), because Rupelian shells have a paucispiral protoconch, whereas the Chattian/Aquitanian species has a multispiral protoconch, and is therefore a separate species. Thus, we consider for instance that P. (P.) gaasensis n. sp. to be present only in the Rupelian.
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 522-526, DOI: 10.5252/geodiversitas2024v46a15, http://zenodo.org/record/13985760