Cyclolituites Remelé, 1886

Aubrechtová, Martina & Korn, Dieter, 2022, Taxonomy and ontogeny of the Lituitida (Cephalopoda) from Orthoceratite Limestone erratics (Middle Ordovician), European Journal of Taxonomy 799 (1), pp. 1-108 : 96

Genus Cyclolituites Remelé, 1886

Type species

Lituites applanatus Remelé, 1880 ; by original designation.

Species included

Cyclolituites americanus Hyatt, 1894 ; Cyclolituites anhuiensis Qi, 1980 ; Lituites applanatus Remelé, 1880 ; Cyclolituites dazhubaensis Chen in Gao et al., 1982; Cyclolituites hubeiensis Xu & Liu, 1977 ; Cyclolituites kjerulfi Sweet, 1958 ; Cyclolituites Lynceus Holm, 1891 ; Lituites Lynnensis Kjerulf, 1865 ; Cyclolituites trilobatus Lai & Wang in Wang, 1981.

Diagnosis

Genus of the family Lituitidae with discoidally coiled conch, uncoiled conch part lacking. Inner whorls tightly coiled, last volution or only its apertural end detached from the preceding; umbilical window large, 2–5 mm wide; whorl expansion rate ca 3.10; increasingly prominent ventral ridge developed in apertural end of the conch. Shell surface faintly annulated or lirated. Siphuncle position subdorsal to subcentral. Aperture of mature conch five-lobed, characterised by a deep ventral sinus, a pair of asymmetric ventrolateral lappets, lateral sinuses and less pronounced dorsolateral and dorsal projections (after Sweet 1958 and Furnish & Glenister 1964; modified).

Remarks

Cyclolituites americanus , from the early or middle Darriwilian strata of Newfoundland, differs from all other species of the genus in a significantly larger coiled conch (over 40 mm diameter) and in the pronounced paired grooves flanking the ventral sinus of the ornament. In both characters, C. americanus is similar to Angelinoceras latum ( Dzik 1984) . However, C. americanus is known so far only from a single, fragmentary specimen ( Flower 1975), in which adoral part of the conch are missing, and the species is thus tentatively retained in the genus Cyclolituites .

Dzik (1984) stated that Cyclolituites applanatus , C. lynceus and C. lynnensis cannot be recognised as separate species. In fact, however, the data presented herein show that the three species can be distinguished rather easily based on their maximum conch diameters, whorl expansion rates and shell ornament (see below). Dzik (1984) stated that C. kjerulfi appears to represent apical parts belonging to some species of the genus Ancistroceras . This interpretation is not possible to validate here without the study of the type specimens of C. kjerulfi , but from descriptions of the species by Sweet (1958), it is clear that the coiled conch has an umbilical window and a ventral keel. Both features are characteristic for species of the genus Cyclolituites .

Geographic and stratigraphic occurrence

Newfoundland ( Canada), Norway, Sweden, northern Germany, Anhui and Hunan ( China); Middle to Late Ordovician.