Pseudaganides aquitanense, 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 : 482

Pseudaganides aquitanense n. sp.

(Fig. 11C-E)

urn:lsid:zoobank.org:act:5A8D33FE-BD65-41CC-BF14-5DE1E26B3B19

ETYMOLOGY. — From the name of the region Nouvelle Aquitaine where all the specimens of this new species have been collected

TYPE MATERIAL. — Holotype. France • 1 specimen (adult); Nouvelle-Aquitaine , Aiffres ; [46°18’07”N, 0°26’07”W]; Retrocostatum Zone; Upper Bathonian; Patrick Branger leg.; MBAN; 2023. PB.N96 ( Fig. 10C ).

Paratype. France • 1 specimen; Nouvelle-Aquitaine , Niort , Buffevent quarry ( POC0009 ); [46°20’28”N, 0°30’21”W]; Retrocostatum Zone; bed 8b; Upper Bathonian; Patrick Branger leg.; MBAN; 2023. PB.N124 (Fig. 11E).

OTHER SPECIMENS EXAMINED. — France • 2 specimens; Nouvelle-Aquitaine, La Crèche, Champs-Albert; [46°21’08”N, 0°17’58”W]; Retrocostatum Zone; Upper Bathonian ; Patrick Branger leg.; MBAN; 2023.PB.N106, 2023.PB.N125.

TYPE LOCALITY AND STRATUM TYPICUM. — Until now, Pseudaganides aquitanense n. sp. has only been collected from the Upper Bathonian, Retrocostatum Zone, where it seems restricted. The holotype is from Aiffres.

MEASUREMENTS. — See Table 5.

DESCRIPTION

Small Pseudaganides , the smallest among Bathonian and Callovian species ( Fig. 10 ), 58 to 61 mm diameter for full grown shells. Inner whorl section is oval, the venter flattens, just slightly rounded before the end of the phragmocone where it is limited by well-marked angulated shoulders that disappear close to the aperture as the shell widens. The umbilicus is closed, boarded by a rounded edge. Maximum width is situated on the dorsal part, close to the umbilicus. Suture line ( Fig. 4E ) draws a true S, the lateral lobe is wide but not very deep with P/L around 30%. The latero-dorsal saddle is visible for the first time in this lineage on the whole shell. On the holotype (Fig. 11C), the two last septa of the phragmocone are approximated indicating the adult stage.

REMARKS

Pseudaganides aquitanense n. sp. is the only Pseudaganides that have been found within Upper Bathonian strata with certainty. Presently, the only cited Pseudaganides of this age was Pseudaganides subbiangulatus . This Bathonian placement should be now revised because of several major differences with Pseudaganides aquitanense n. sp., the size and shape of the suture lines that is more folded on Pseudaganides subbiangulatus shells and, above all, because of the age attributed to the P. subbiangulatus collected in our study area (see below). Pseudaganides aquitanense n. sp. differs mostly from Antaganides fournieri n. gen., n. sp. by its suture lines that shows a sigmoidal profile at any growth stage. The sizes of the two species are similar, about 60 millimeters at adult stage. Antaganides fournieri n. gen., n. sp. can be interpreted as the probable ancestor of Pseudaganides aquitanense n. sp. and Pseudaganides buffeventi n. sp. The latter is a larger and younger species with a clearly open umbilicus.

Figures

FIG. 10. — Evolution of the size of the adult shell and phragmocone among the different species of Antaganides n. gen. and Pseudaganides Spath, 1927 for full grown shells.

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.