Calliovarica, Vokes, 1939

Hickman, Carole S., 2018, A new Calliovarica species (Seguenzioidea: Chilodontidae) from the Eocene of Oregon, USA: Persistence of a relict Mesozoic gastropod group in a unique forearc tectonic setting, PaleoBios 35, pp. 1-10 : 2-3

CALLIOVARICA Vokes, 1939

Type species — By monotypy. Calliovarica eocensis Vokes, 1939 . Early Eocene (“Capay stage”), Central California, Cerros Shale member of the Lodo Formation .

Stratigraphic occurrence —Restricted to the Paleocene and Eocene.

Differential diagnosis —Distinguished from all seguenzioid vetigastropods by axial varices at regular intervals of 180°on body whorl and spire whorls; terminal flaring of adult outer lip immediately following final varix; lacking reflected inner lip, expanded inductural

callus and apertural dentition in inner and outer lips.

Remarks —Three chilodontid genera that show some of the diagnostic features of Calliovarica are Agathodonta Cossmann, 1918 , Danilia Brusina, 1865 , and Onkospira Zittel, 1873 .

Features of poorly known type species of Agathodonta [ Trochus dentigerus d’Orbigny, 1843 , from the Early Cretaceous (Neocomian) of France] have been clarified through designation of a lectotype ( Kollmann 2005) and careful re-evaluation and illustration ( Herbert 2012). Axial thickenings are clearly present on spire whorls of the lectotype. However, the outer lip is not reflected or thickened, there is no inductural callus, and there are well-developed apertural denticles. Clarification of the features of fossil Agathodonta ledHerbert (2012) to consider it extinct and inappropriate to living taxa formerly allocated to the genus. He proposed Clypeostoma for a group of living Indo-Pacific species with strong induc- tural callus that is even farther removed morphologically from Calliovarica .

Danilia is similar to Calliovarica in developing a prominent subterminal thickening of the final aperture, but there are no varices on the spire whorls. Danilia also differs in the presence of a strong tooth and deep notch on the inner lip, and a prominent inductural callus. Danilia shares a Cretaceous origin with Agathodonta . It occurs throughout the Cenozoic, but never in large numbers and predominantly in deep water where it is often associated with hard substrate in sponge and coral thickets. For detailed nomenclatural history of Danilia , see Herbert (2012).

Onkospira is a Mesozoic high-spired genus that is similar to Calliovarica in having multiple synchronous varices that are closely aligned on successive whorls, with the final varix located immediately behind the outer lip. The outer, basal and inner lips are continuous, flared, relatively thin, and lack denticles. The type species is from the Late Jurassic (Oxfordian) of Germany, but species are also recognized as early as the Middle Jurassic (Bathonian) of India (Das et al. 1999) and the Late Cretaceous (Maastrichtian) of Siberia ( Kaim et al. 2004).

This leaves Calliovarica as the least well-understood chilodontid genus with single or multiple variciform thickenings. Although Vokes (1939, p. 183) clearly stated that “no species similar to this has been previously described” and that it was distinguished by “numerous varices,” these features are not visible in the four inadequate photographs of the holotype and two paratypes (Pl. 22, figs. 20, 23, 25, 28). Stacked digital photographs of the types ( Fig. 1A–F) illustrate characters in the new differential diagnosis.

Two additional species, both from the late Paleocene– early Eocene have been described under Calliovarica . The species described as C. pacifica Squires and Goedert, 1994 , is from the middle lower Eocene Crescent Formation in Washington. The assignment was based on thickening of the outer lip of the holotype, described as a “resting stage,” but there are no varices on the spire whorls. Although the shell has other clearly chilodontid features, notably prominent apertural denticles,it cannot be allocated to Calliovarica s.s. A second species of particular interest is from the Early Paleogene greenhouse interval in the Chatham Islands, eastern New Zealand. It was identified initially as Bathybembix (?) sp. nov. (Beu and Maxwell 1990) and subsequently as Calliovarica n. sp. (Beu and Raine 2009) prior to formal description as C. rangiaotea Stillwell, 2014 .