Anagaudryceras sp.

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 : 538

Anagaudryceras sp. juvenile 2

Fig. 9K.

Material.—One internal mold of the phragmocone preserving patches of the shell ( CADIC PI 453). From Maastrichtian Cretaceous), López de Bertodano Formation, Ammonite Asemblage 11 Maorites tuberculatus, Seymour Island, Antarctica.

Description. —Small shell with evolute coiling, the whorl section is as high as broad (Wb/Wh ~1; Table 6). Wide umbilicus (U ~44 %; Table 6), with a gentle umbilical wall and rounded umbilical shoulder. The flanks converge to a rounded ventrolateral shoulder and rounded venter. The neanoconch is ornamented by four spaced ribs.The early-whorl ornamentation is almost imperceptible to the naked eye, but consists of strongly prorsiradiate hair-like striae. From the fourth whorl there are prorsiradiate constrictions and collars that are projected slightly aperturally on the venter.

Remarks.—Even though our specimen is a small juvenile, its style of ornamentation differs from the other species of Anagaudryceras described here. The inner whorls of A. seymouriense , from the upper part of the López de Bertonado Formation, differs in its smooth neanoconch and in the flexuous lirae with intercalate lirae that reach to mid flank. Otherwise, Anagaudryceras sp. juvenile 2 closely resambles A. subcompressum sp. nov. in the degree of involution but the ornamentation consists of prorsiradiate lirae with some constrictions and a more compressed whorl section.