Anagaudryceras, Shimizu, 1934

Raffi, María E., Olivero, Eduardo B. & Milanese, Florencia N., 2019, The gaudryceratid ammonoids from the Upper Cretaceous of the James Ross Basin, Antarctica, Acta Palaeontologica Polonica 64 (3), pp. 523-542 : 530

Anagaudryceras cf. A. politissimum ( Kossmat, 1895)

Figs. 5A, B , 6C .

Material. —Three internal molds preserving patches of the shell and including the phragmocone and part of the body chamber (CADIC PI 180, 454, 455). From early Campanian of the Rabot Formation, Ammonite Assemblage 6 Karapadite s– Natalites spp. Group 2, Redonda Point, Member II, James Ross Island, Antarctica.

Description. —The coiling is fairly evolute, the whorl section is fairly compressed (Wb/Wh ~0.71–0.74; Table 3). Wide umbilicus (U ~35%; Table 3) with a slightly gradual umbilical wall and rounded umbilical shoulder. The flanks converge to a well-defined ventrolateral shoulder and rounded and slightly arched venter. The ornamentation is almost imperceptible to the naked eye, but consists of fine lirae accompanied by sinuous constrictions preceded by flat collars.

Remarks.—The ornamentation style, compressed whorl section and slightly arched venter of the three specimens discussed here closely resemble Anagaudryceras politissimum ( Kossmat, 1895) from the Turonian–Santonian of India, Santonian of Zululand and Maastrichtian of Madagascar ( Kossmat 1895; Kennedy and Klinger 1979). Killian and Reboul (1909: 14, pl. 1: 7) refered A. politissimum from Snow Hill Island (Karlsen Cliffs Member), however, this material is less compressed and has a narrower venter. Ifrim et al. (2004: 1590–1592; text-figs. 3I, J, 6D, E, I) referred juveniles specimens from northeastern Mexico to A. politissimum , but they are too small (D ~ 8.6–25 mm) for proper identification. Anagaudryceras cf. A. politissimum closely resambles A. politissimum from Central Chile ( Salazar et al. 2010) in its style of ornamentation but is less compresed (SOM: fig. 3). Anagaudryceras yamashitai ( Yabe, 1903) , from the Coniacian–?early Campanian of Hokkaido, has similar whorl section and ornamentation style of thin and flexuous lirae to Anagaudryceras cf. A. politissimum . However, A. yamashitai presents neither collars nor constrictions, which are typical of A. politissimum ( Kennedy and Klinger 1979) . Thus, our specimens have consistent ornamentation similarities with A. politissimum , but they are more compressed than Kossmat’s holotype (SOM: fig. 3).

Figures

Fig. 5. The gaudryceratid ammonoid Anagaudryceras, early Campanian (Upper Cretaceous) of Antarctica, from Rabot Formation, Redonda Point locality (A, B) and from Santa Marta Formation, Brandy Bay locality (C, D). A, B. Anagaudryceras cf. A. politissimum (Kossmat, 1895). A. CADIC PI 455. B. CADIC PI 454. C, D. Anagaudryceras sp. juvenile 1. C. CADIC PI 533. D. CADIC PI 534. In lateral (A1–D1) and ventral (A2–D2) views. Arrows mark the beginning of the body chamber.

Fig. 6. The gaudryceratid ammonoid Anagaudryceras spp., from the Campanian (Cretaceous), Antarctica, Rabot Formation, Redonda Point locality (A–C), and from the late Campanian–early Maastrichtian (Cretaceous), Antarctica, Snow Hill Island Formation, Sanctuary Cliffs locality (D, E). A, B. Anagaudryceras calabozoi Raffi and Olivero sp. nov. A. CADIC PI 411, holotype, adult macroconch; suture line (A1), transversal section (A2). B. CADIC PI 472, adult microconch; suture line (B1), transversal section (B2). C. Anagaudryceras cf. A. politissimum (Kossmat, 1895), CADIC PI 455, transversal section. D. Anagaudryceras sanctuarium Raffi and Olivero sp. nov., CADIC PI 604, transversal section. E. Anagaudryceras subcompresum Raffi and Olivero sp. nov., CADIC PI 506, holotype, adult specimen; suture line (E1), transversal section (E2). Scale bars 10 mm. Abbreviations: E, external lobe; I, internal lobe; L, lateral lobe; U, umbilical lobe; Us, septal lobe.