Phricodoceras Hyatt, 1900

Dommergues, Jean-Louis & Meister, Christian, 2013, Significance of intermediate forms in phyletic reconstruction of ammonites: Early Jurassic Phricodoceras case study, Acta Palaeontologica Polonica 58 (4), pp. 837-854 : 844

Genus Phricodoceras Hyatt in Zittel, 1900 = Hemiparinodiceras Géczy, 1959

Type species: Ammonites taylori Sowerby, 1826 ; Early Pliensbachian, from a boulder in glacial till at Happisburgh, Norfolk, England, by original designation .

Remarks.—21 nominal species can be attributed to the genus Phricodoceras . Nine of them are based on NW European specimens and 11 on Tethyan sensu lato forms. In a recent revision of the genus, Meister (2007) retains only 11 valid species, three of which are NW European while seven are Tethyan. These proportions are representative of the high diversity of the genus Phricodoceras in Tethyan and especially Mediterranean faunas. According to Meister (2007), three m–M pairings can be suspected while four small or tiny species (one NW European and three Mediterranean) cannot readily be considered microconchs despite their small size. In fact, despite its indisputable success in the palaeontological literature, the m–M model is often far from evidence. The possibility of small species without or at least without significant m–M dimorphism is rarely considered as a valuable alternative hypothesis for ammonites ( Davis et al. 1996). Such a pattern, however, is not rare among the extant cephalopods.

Geographic and stratigraphic range.—Chiefly NW Europe and Mediterranean Tethys including Pontides ( Turkey). The presence of Phricodoceras is also attested in Timor ( Indonesia) but is doubtfull in British Columbia ( Canada), Oregon ( USA), and Chile. Phricodoceras ranges from Late Sinemurien to Late Pliensbachian.