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 : 529-530

Genus Anagaudryceras Shimizu, 1934

Type species: Ammonites sacya Forbes, 1846 , by original designation of Shimizu (1934: 67), subjective synonym of Ammonites buddha Forbes (1846:112 , pl. 14: 9), Albian of Southern India.

Remarks.—For synonymy and diagnosis see Hoffmann 2015: 17 and references therein.

The original type material, Ammonites sacya Forbes 1846 , designated by Shimizu (1934) is a poorly preserved juvenile specimen that put on display nomenclatural problems and the validity of Anagaudryceras as genus. Wright and Matsumoto (1954) conducted a comprehensive review of the genus, with subsequent interpretations by several authors ( Matsumoto 1959; Wiedmann 1962; Howarth 1965; Haggart 1989; Kennedy and Klinger 1979; and Hoffman 2010). Stoliczka (1865) synonimized Ammonites buddha with Ammonites sacya . Afterward, Whiteaves (1884) and Kossmat (1895) treated Ammonites buddha as subjective junior synonym. Subsequent authors (eg., Matsumoto 1959, 1995; Henderson and McNamara 1985; Hoffman 2010) accepted the synonymy and treated Ammonites buddha as the adult stage of Ammonites sacya . However, we follow Matsumoto (1995) who according to the ICZN Article 24 (precedence of the names or acts is fixed by the First Reviser, in this case Stoliczka 1865) proposed to call this species A. sacya .

Arkell et al. (1957), Luppov and Drushchits (1958) and Wright et al. (1996) treated Anagaudryceras as an independent genus. Wiedmann (1962) placed the genus Anagaudryceras with Gaudryceras in synonymy. Although, Gaudryceras and Anagaudryceras present a similar type of suture ( Schindewolf 1961), Anagaudryceras has finer and weaker ornamentation compared to Gaudryceras what is sufficient to a generic distinction ( Howarth 1965). Kennedy and Klinger (1979) argued that if the synonymy between Ammonites sacya and Ammonites buddha is valid, Anagaudryceras is different enough from other gaudryceratids to be treated as separate genus. We concur with this statement and disagree with the taxonomic interpretation of Wiedmann (1962).

Kennedy and Klinger (1979) grouped the species of Anagaudryceras in two main groups: the group of Anagaudryceras buddha (= A. sacya ) with strong ribs in the body chamber; and the group of Anagaudryceras involvulum ( Stoliczka, 1865) , with a weak ornamentation throughout ontogeny, weak constrictions and without ribs in the body chamber. However, Matsumoto (1995) does not accept this grouping, neglecting particularly the group of A. involvulum on the basis that many of the included species bear narrow and strong ribs separated by wide interspaces in the body chamber. He concluded that the succession of Albian–Turonian species with band-like ribs separated by narrow grooves (e.g., A. sacya ) followed by Coniacian to Maastrichtian species with narrow and strong ribs separated by wide interspaces suggests an evolutionary change ( Matsumoto 1995). However, the macroconch of Anagaudryceras calabozoi Raffi and Olivero sp. nov., from the mid-Campanian of the Rabot Formation, has band-like ribs at the adult body chamber gainsaying Matsumoto’s 1995) concept.

Stratigraphic and geographic range.—The genus is known from middle Albian to Maastrichtian. The geographic distribution includes Antarctica, New Zealand, Zululand, Madagascar, Angola, north Africa, France, Germany, Austria, Romania, southern India, Japan, Sakhalin, Kamchatka, Alaska, British Columbia, and California