Gaudryceras Grossouvre, 1894

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 : 527

Genus Gaudryceras Grossouvre, 1894

Type species: Ammonites mitis Hauer, 1866 , by the subsequent designation of Boule et al. (1906); Gosau Beds of Strobl, near Ischl, Austria, Coniacian.

Diagnosis.—See Kennedy and Klinger 1979: 128 emended by Hoffmann 2015: 16.

Remarks.—The genus has been discussed in our previous work ( Raffi and Olivero 2016), here we add the early Campanian species Gaudryceras submurdochi Raffi and Olivero sp. nov. to the Antarctic conspicuous Gaudryceras fauna. Gaudryceras submurdochi Raffi and Olivero sp. nov. is included within the group of Gaudryceras tenuiliratum Yabe, 1903 . We initially considered this species in the genus Vertebrites . However, in our new Antarctic Gaudryceras the Vertebrites -like ornamentation (sensu Matsumoto and Yoshida 1979) is accompanied by marked changes in whorl compression and evolution during ontogeny that clearly differs from the typically Vertebrites serpenticone whorl type.

According to Matsumoto and Yoshida (1979) and Hoffmann (2010), the Vertebrites- like ornamentation appears in many species of Gaudryceras . Besides, the extra lobe in the internal suture line of Vertebrites murdochi Marshall, 1926 , reported for the first time by Marshall (1926), was misinterpreted and its suture correspond to that of Gaudryceras (see Hoffman 2010: 73 and the bibliography therein). In the last complete review of the family Tetragonitidae, Hoffmann (2010) mentioned Vertebrites murdochi as an endemic paedomorphic member of Gaudryceras rejecting a generic or subgeneric identity of Vertebrites . In this oportunity we desist to give opinion on the validity of Vertebrites as an independent genus, but we concur with Henderson and McNamara (1985) that larger specimens of Vertebrites murdochi are needed to asses its present generic status.

Thus, in addition to the five Antarctic species of Gaudryceras described in Raffi and Olivero (2016), the new species Gaudryceras submurdochi Raffi and Olivero sp. nov. is described for the early Campanian (possible up to the earliest mid-Campanian) of the Santa Marta and Rabot formations. The new material consists of relatively small-sized shells, and many specimens less than 30–40 mm in diameter seem to be juveniles with partly preserved body chambers. Nonetheless, there are three small shells preserving the phragmocone and part of the body chamber with diameters up to 50 mm, which we interpret as adult shells.

Stratigraphic and geographic range.—The genus ranges from the Upper Albian to the Maastrichtian. Its geographical distribution includes Antarctica, New Zealand, Madagascar, South Africa, Angola, north Africa, the Middle East, central and southern Europe, southern India, Japan, Sakhalin, Kamchatka, Alaska, British Columbia, California, Mexico, Chile, and southern Patagonia.