Pseudaganides crechensis, Branger, 2024

Branger, Patrick, 2024, Antaganides n. gen., a new genus of Middle Jurassic nautiloid, ancestor of Pseudaganides Spath, 1927, with discussion on the phyletic origin of the family Pseudonautilidae, Geodiversitas 46 (14), pp. 471-493 : 483-484

Pseudaganides crechensis n. sp.

(Figs 12C1-C3; 13C)

urn:lsid:zoobank.org:act:9DEFECCC-BA77-49A1-BA95-AEAB23E26268

DIAGNOSIS. — Small nautilus, maximum diameter 75 mm, shell rather compressed with a subrectangular section except on the body-chamber where the sides are a little more rounded. Umbilicus clearly open. Suture lines with a wide and rather deep lateral lobe.

TYPE MATERIAL. — Holotype. France • 1 specimen (adult); Nouvelle-Aquitaine , La Crèche , Champs-Albert ; [46°21’08”N, 0°17’58”W]; base of the Gracilis Zone, Prahecquense Subzone ; Lower Callovian; Patrick Branger leg.; MBAN; 2023.PB.N107 (Fig. 12C1-C3).

OTHER SPECIMENS EXAMINED. — France • 1 specimen (adult); same data as holotype; 2023.PB.N132 • 2 specimens (young shells almost newly hatched); same data as holotype; 2023.PB.N142, 2023.PB.N143 • 1 specimen; Nouvelle-Aquitaine, Niort, Buffevent quarry ( POC0009 ); [46°20’28”N, 0°30’21”W]; base of the Gracilis Zone, Prahecquense Subzone ; Lower Callovian ; Patrick Branger leg.; MBAN; 2023.PB.N75.

TYPE LOCALITY AND STRATUM TYPICUM. — The holotype of Pseudaganides crechensis n. sp. (Fig. 12C1-C3) has been sampled from the base of the Gracilis Zone, Prahecquense Subzone , Lower Callovian, in La Crèche.

MEASUREMENTS. — See Table 7.

ETYMOLOGY. — The species is named based on La Crèche (Deux-Sèvres), the city where four of the five known specimens were collected.

DESCRIPTION

Pseudaganides crechensis n. sp. is a small sized and compressed nautilus, maximum diameter observed is 75 mm on the biggest specimen (2023.PB.N75). The section is oval on the embryonic shell, then subrectangular until the end of the phragmocone where it widens. The body-chamber looks more rectangular at the adult stage because of the presence of angular but not sharp ventral shoulders. Flanks are slightly rounded with a maximum width at one third of the height. At the beginning of the body-chamber, the outer part of the flank is a little depressed. The venter, rounded at first, flattens from the end of the phragmocone to the aperture. The umbilicus is clearly open (u> 0.10), funnel like, with rounded sides. The lateral lobe of the suture line ( Fig. 4F ) is well marked, (P/L = 0.43 to 0.47). The ventral lobe is shallow, P/L = 0.23 on the type specimen. The two young shells show some ontogenetic elements. The hatching size, indicated by the existence of the nepionic constriction ( Landman 1988), corresponds to 1 cm in diameter. At that size the shell shows a cross-hatched ornament of fine growth lines and perpendicular lirae ( Fig. 13C ). The aperture, very well-preserved on the type specimen (Fig. 12C1-C3), is typical of Pseudaganides with straight lateral borders and a well-marked ventral sinus.

REMARKS

Pseudaganides crechensis n. sp. presents the same size than Pseudaganides buffeventi n. sp. The two species differs mainly from their umbilicus that is open on Pseudaganides crechensis n. sp. whereas it is closed on Pseudaganides buffeventi n. sp.

Figures

FIG. 4. — Suture lines of Antaganides n. gen. and Pseudaganides Spath, 1927: A, Antaganides cf. erycinus (Tagliarini,1901), n. comb., 2023.PB.N117; B, Antaganides sauvageti n. gen., n. sp. 2023.PB.N64; C, Antaganides fournieri n. gen., n. sp., 2023.PB.N105; D, Pseudaganides aquitanense n. sp., 2023.PB.N96; E, Pseudaganides buffeventin. sp.,2023.PB.N76; F, Pseudaganides crechensisn. sp., 2023.PB.N107; G, Pseudaganides subbiangulatus (d’Orbigny,1850),2023. PB.N73, Patina Zone; H, Pseudaganides subbiangulatus, 2023.PB.N112, Anceps Zone.

FIG. 13. — A, Antaganides cf. erycinus (Tagliarini, 1901), n. comb., specimen 2023.PB.N129, with its preserved muscle scar, Niort, Upper Bajocian, Niortense Zone; B, Antaganides cf.erycinus (Tagliarini,1901),n.comb.,specimen 2023.PB.N148, with its siphuncle,viaduc de l’Égray,Upper Bajocian,Niortense Zone;C, Pseudaganides crechensis n. sp.,specimen 2023.PB.N143, newly hatched shell showing its reticulate ornamentation on the phragmocon;D1-D3, Pseudaganides subbiangulatus (d’Orbigny,1850),specimen 2023.PB.N110, full grown shell with itswell preserved aperture,Bougon,Lower Callovian,Gracilis Zone,Patina Subzone,Boginense Horizon; E1-E3, Pseudaganides subbiangulatus, specimen 2023.PB.N112, Niort,Middle Callovian,Anceps Zone,Stuebeli Subzone.*, end of the phragmocone.Scale bars:1 cm.