Antaganides fournieri, 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 : 478-480

Antaganides fournieri n. gen., n. sp.

(Fig. 3C1-C3)

urn:lsid:zoobank.org:act:48BF9FDC-A9CE-4E62-880D-A58A7C192254

DIAGNOSIS. — Small sized nautilus, maximum diameter about 60 mm, shell rather compressed on the last whorl with an oval section except on the body-chamber where the venter flattens, sometimes concave. Narrow umbilicus. Suture lines with a wide but shallow lateral lobe.

ETYMOLOGY. — After the name of Alphonse Fournier (1858-1911), surgeon and former preparator at the Museum of Natural History in Niort and, later, at the Faculté des Sciences in Poitiers.

TYPE MATERIAL. — Holotype. France • 1 specimen (complete); Nouvelle-Aquitaine , Sainte-Éanne , near la Mothe-Saint-Héray, les Hauts-de-Rochefort quarry ( NAQ0021 ); [46°23’30”N, 0°07’55”W]; Base of Progracilis Zone, Orbignyi Subzone; Middle Bathonian; Patrick Branger leg.; MBAN; 2023.PB.N105 (Fig. 3C1-C3).

OTHER SPECIMEN EXAMINED. — France • 1 specimen (phragmocone); Nouvelle-Aquitaine , La Crèche; [46°21’08”N, 0°17’58”W]; Middle Bathonian; Patrick Branger leg.; MBAN; 2023.PB.N109. TYPE LOCALITY AND STRATUM TYPICUM. — Antaganides fournieri n. gen., n. sp. has only been found within the Middle Bathonian of the Submediterranean Realm. The holotype has been found at the base of the Progracilis Zone , Orbignyi Subzone , at les Hauts-de-Rochefort quarry (Sainte-Eanne, France). The species persists until the Bremeri Zone, Fortecostatum Subzone.

MEASUREMENTS. — See Table 3.

DESCRIPTION

The type specimen is a complete shell, broken on the right side of the body-chamber. The two last septa are slightly approximated indicating an adult stage. The size of the shell is quite small as for other Antaganides n. gen. species, around 60 mm ( Fig. 10 ). The phragmocone is compressed (W/H = 0.84) with a subrectangular section. The flanks and the venter are slightly rounded. The body-chamber is more inflated (W/H = 0.92) with a maximum width close to the umbilicus at about 1/3 of the flank. The external part of the shell is rather depressed while the venter is flattening. The umbilical shoulder is rounded whereas the ventral shoulder becomes angular, but never sharp, on the body-chamber. On the first quarter of the last whorl, close to the umbilicus, suture line of Antaganides fournieri n. gen., n. sp. ( Fig. 4C ) shows a faint lateral saddle followed by a shallow but well-marked lateral lobe. Close to the umbilicus, last septa are backward projected and do not show any lateral saddle. A shallow ventral lobe is present at any stage.

REMARKS

Antaganides fournieri n. gen., n. sp. size and shape are very similar to Antaganides sauvageti n. gen., n. sp. that is a little older. The main difference can be observed on the suture lines, Antaganides fournieri n. gen., n. sp. shows a dorsal saddle on the inner whorls and the lateral lobe is deeper than on older Antaganides n. gen. species. Antaganides fournieri n. gen., n. sp. could also be confused with Antaganides grulkei n. gen., n. sp., a nautilus of the same size that seems to be a little more abundant at the same level. By this latter, the shape of the umbilicus shows a gentle slope whereas Antaganides fournieri n. gen., n. sp. owns a subvertical umbilical wall.

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.