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 Author Branger, Patrick 4 rue Franche F- 79410 Cherveux (France) patrick.branger@wanadoo.fr text Geodiversitas 2024 2024-10-03 46 14 471 493 https://sciencepress.mnhn.fr/sites/default/files/articles/pdf/g2024v46a14.pdf journal article 304151 10.5252/geodiversitas2024v46a14 a6dcf4e3-2ba8-4c57-a797-1e57727505c5 1638-9395 13884433 urn:lsid:zoobank.org:pub:2C97C1BD-2DAA-485A-8AE0-2E3DD501D5F2 Antaganides sauvageti n. gen., n. sp. (Fig. 3B1-B3) urn:lsid:zoobank.org:act:8F011053-8B4F-412E-83AB-BF8FF028EA81 DIAGNOSIS . — Small nautilus, maximum diameter about 60 mm , shell compressed with an oval section on inner whorls. On the adult body-chamber, the venter flattens. The umbilicus is open on the juvenile but very small. Suture lines with a wide but shallow lateral lobe. ETYMOLOGY. — After the name of Henri Sauvaget, teacher in Niort, involved in the Museum of Natural History of this town at the beginning of the XXth century and donator of his paleontological collection to this Museum. TYPE MATERIAL . — Holotype . France • 1 specimen ; Nouvelle-Aquitaine , Parthenay , Sainte-Ouenne , Viaduc de l’Égray ; [ 46°25’25”N , 0°27’28”W ]; Zigzag Zone, layer “Banc Pourri”; Lower Bathonian ; Patrick Branger leg.; MBAN ; 2023.PB.N64 (Fig. 3B1-B3). OTHER SPECIMENS EXAMINED . — France • 1 specimen ; Nouvelle-Aquitaine, Aigondigné, Mougon, “Trotte-Buie” ( POC0102 ); [ 46°25’37”N , 0°12’28”W ]; Zigzag Zone, layer “Banc Pourri”; Lower Bathonian ; Patrick Branger leg.; MBAN ; 2023.PB.N93 • 1 specimen ; Nouvelle-Aquitaine, Niort; [ 46°18’25”N , 0°27’42”W ]; Zigzag Zone, layer “Banc Pourri”; Lower Bathonian ; Patrick Branger leg.; MBAN ; 2023.PB.N127 • 1 specimen ; Nouvelle-Aquitaine, Échiré; [ 46°21’30”N , 0°25’37”W ]; Zigzag Zone, layer “Banc Pourri”; Lower Bathonian ; Patrick Branger leg.; MBAN; 2023. PB.N128 . TYPE LOCALITY AND STRATUM TYPICUM . — All the specimens come from a layer called regionally “Banc Pourri” that corresponds to the Zigzag Zone of the Lower Bathonian, especially at the Viaduc de l’Égray where the holotype is coming from. MEASUREMENTS . — See Table 2. DESCRIPTION Small shells, around 60 mm in diameter, very involute with a closed or slightly open umbilicus. The type specimen is an adult form displaying approximation of the last two septa. The shell is compressed in the inner whorls and widens on the body-chamber that is always higher than wide. The section of the whorls is trapezoidal and flanks are slightly rounded. The maximum width is close to the umbilicus, at about 1/3 of the height of the whorl. Umbilical area is rounded with a perpendicular coiling to the proceeding whorl. The ventral part is limited by rounded shoulders that become more angular but never sharp on the body-chamber. Venter is rounded, flattened on the body-chamber where it can become slightly concave. Suture line ( Fig. 4B ) shows a wide, shallow lateral lobe and a ventral lobe too. The aperture is partly broken but the dorsal part seems to be similar to these of Pseudaganides . FIG . 5. — Ratio “h” of the height of the whorl compared with the diameter of the shell (H/D) among the different species of Antaganides n. gen. and Pseudaganides Spath, 1927 . FIG . 6. — Ratio “w” of the width of the whorl compared with the diameter of the shell (W/D) among the different species of Antaganides n. gen. and Pseudaganides Spath, 1927 . REMARKS In Western Europe, Lower Bathonian beds are usually very fossiliferous but no similar species has ever been described.Compared with Antaganides cf. erycinus n. comb. , the shell of A. sauvageti n. gen., n. sp. is a little larger and thicker at adult age.