Pseudaganides buffeventi, 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

Pseudaganides buffeventi n. sp.

(Fig. 12A, B)

DIAGNOSIS. — Small nautilus, maximum diameter about 70 mm, shell rather compressed with an oval section except on the body-chamber where the venter flattens, boarded by angular but not sharp shoulders. Umbilicus very narrow.Suture lines with a wide and quite deep lateral lobe.

ETYMOLOGY. — The species is named basing on Buffevent, the name of the locality where the type species has been discovered.

TYPE MATERIAL. — Holotype. France • 1 specimen; Nouvelle-Aquitaine , Niort , Buffevent quarry ( POC0009 ); [46°20’28”N, 0°30’21”W]; Bullatus Zone; bed 9; Lower Callovian; Patrick Branger leg.; MBAN; 2023.PB.N76 (Fig. 12A).

OTHER SPECIMEN EXAMINED. — France • 1 specimen (adult); Nouvelle-Aquitaine, Salles; [46°23’45”N, 0°06’19”W]; Bullatus Zone; Lower Callovian ; Patrick Branger leg.; MBAN; 2023.PB.N102 (Fig. 12B).

T YPE LOCALITY AND STRATUM TYPICUM. — Both specimens have been collected at the base of the Bullatus Zone, Lower Callovian where it appears to be restricted. The holotype (Fig. 12A) comes from Buffevent quarry.

MEASUREMENTS. — See Table 6.

DESCRIPTION

Small and compressed nautilus, about 70 mm diameter, the section is oval on the inner whorls, becoming rectangular at the adult stage because of the presence of angular but not sharp ventral shoulders on the body-chamber. The umbilicus is not fully closed but very narrow (u = 0.05), funnel like, with rounded sides. Flanks are slightly rounded with a maximum width at one third of the height. The venter, rounded at first, flattens from the end of the phragmocone to the aperture. The lateral lobe of the suture line (Figs 3-5) is well marked, (P/L> 50%), more rounded on the second specimen (Fig. 11 b) than on the holotype whereas the dorsal saddle seems to be more angular and narrower by 2023.PB.N102 than on the holotype. The ventral lobe is very shallow on 2023.PB.N102, nonexistent on the holotype. The aperture, well preserved on the type specimen, is typical of Pseudaganides with straight lateral borders and a well-marked ventral sinus.

REMARKS

The globose shape of Pseudaganides buffeventi n. sp. can be compared with Pseudaganides subbiangulatus (d’Orbigny, 1850) . The two main differences are the much smaller size for Pseudaganides buffeventi n. sp. ( Fig. 10 ) and the width of the umbilicus that is slightly more open on this new species than on d’Orbigny’s species ( Fig. 8 ). The suture line ( Figs 4 ; 12) of the two samples recognized as Pseudaganides buffeventi n.sp. shows little differences.

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. 8. — Ratio “W/H” of the shell among the different species of Antaganides n. gen. and Pseudaganides Spath, 1927.

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.