Calliovarica eocensis 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 : 3-6

Calliovarica eocensis Vokes, 1939

FIG. 1A–F

Calliovarica eocensis Vokes, 1939 . p. 183; pl. 22, figs. 20, 23, 25, 28.

Calliovarica eocensis (Vokes) . Squires 1988. p. 206.

Remarks —The holotype ( UCMP 15884) and one of the paratypes ( UCMP 15885) are refigured here to il- lustrate the diagnostic features that are not visible in the original published figures.

The type locality ( UCMP 1817-) in the Cerros Shale Member of the Lodo Formation has been known for more than 100 years, but the geographic location and stratigraphic position and geologic age have been reported differently in the literature, resulting in controversy that was resolved by rediscovery of the site and thorough documentation by Squires (1988). It is also the type locality of Turritella andersoni Dickerson, 1916 , which has served as an important index fossil for correlating early Eocene strata on the Pacific coast. Because Vokes is the only person to have collected the distinctive varicate basal gastropod, it is significant to note that the glauco- nitic sandstone also contained abundant T. anderson i. Vokes published trimmed photographs of the holotype, but the apertural ( Fig. 1A) and semiapertural views ( Fig. 1B) shown here include not only the glauconitic matrix but also an imbedded specimen of T. andersoni .

Calliovarica oregonensis n. sp.

FIG. 2A–C

Calliovarica (?) n. sp. Snavely and Vokes, 1949.

Holotype —Part and counterpart in matrix. UCMP 110715 a (positive) and 110715b (negative); height (incomplete) 30.0 mm; width (incomplete) 21 mm.

Figured paratype — UCMP 110716, in matrix; height (incomplete) 23 mm; width (estimated) 15 mm.

Unfigured paratypes — UCMP 110717 , 110718 , 110719 , 110720 , 110721 , 110722 , 10723 , 110724 .

Material examined — 10 specimens in the type lot.

Type locality — UCMP IP6496 (= USGS 16981). Cliffs on the south side of the mouth of the Nestucca River at Point Porter, Nestucca Bay Quad., Oregon, USA.

Stratigraphic occurrence —Nestucca Formation,

early late Eocene (late Narizian and early Refugian benthic foraminiferal stages and CP 15a-15b calcareous nannoplankton zones of Bukry and Snaveley (1988).

Etymology —Named to emphasize the Oregon occurrence of the species.

Diagnosis —Shell high spired (height exceeds width), larger than that of type species (ht= 28 mm); spiral angle greater (estimated 50–60O); spire whorls slightly biangulate, with three rows of distinct tubercles; varices deviating very slightly from 180O apart, forming successively later during growth; Outer lip prominently thickened immediately following final varix; outer shell layers well developed and thicker than interior nacre.

Description —Shell material is strongly altered and partially exfoliated on all specimens. Protoconchs are broken or worn. The suture appears to be slightly impressed where shell material on adjacent whorls is most intact. There is no evidence of denticulation of either the inner or outer lip. The shape of the peristome and apertural inclination cannot be determined. The varices are robust, but shell material is too degraded to determine thickness. The base of the shell has at least five spiral ribs with fine nodes, although the base is known from two incomplete fragments. Nodes on the spire are most prominent and least numerous on the adapical spiral cord and finer and more numerous on the two abapical cords.

Specimen preservation —Although specimens are incomplete two fortuitous aspects of preservation enhance the information. The coarsely-tuffaceous matrix of the Nestucca Formation does not record fine detail in exterior molds, but it has cleaved in the plane of bedding to produce negative and positive counterparts that have separated with shell material on each half. In the case of the holotype, nacre is present primarily on a portion of the body whorl of the internal mold ( Fig. 2B). The final varix and terminal apertural thickening are partially preserved on both part and counterpart (Fig, 2A, B). Reconstruction of other features of the shell also requires observation of both part and counterpart. Exfoliation of altered shell material clearly occurred during collecting, but fragments provide evidence of original shell structure that are not available in the more stable, but highly altered, shells of the type species of Calliovarica ( Fig. 1A–F). The type lot of the new species was not subjected to stabilizing coatings or excessive preparation. No further preparation was attempted during study, and specimens were not coated for photography in order to illustrate the state of preservation. Each fragmental specimen has been assigned a separate paratype number.

Remarks —The new Oregon species is distinguished from the type species, C. eocensis , by its larger size, and proportionately broader shell with a greater spiral angle and more rapidly expanding body whorl. In size and proportions, the shell is closer to the southern hemisphere species C. rangiaotea Stillwell, 2014 from the Red Bluff Tuff in the Chatham Islands Archipelago. Although the Chatham Islands species lacks multiple well-developed synchronized varices, Stillwell (2014) noted evidence of “indistinct” varices on spire whorls. For this reason, C. rangiaotea is here retained as a species of Calliovarica .

The species described as Calliovarica pacifica by Squires and Goedert (1994), from middle lower Eocene beds in the Crescent Formation in Washington, cannot be included in the genus because the shell lacks multiple varices, although it does have a thickened terminal lip. It is a low-spired turbiniform shell that is most remarkable in the interior elaboration of the outer lip, which is thickened within by strongly-developed denticles that are continuous with denticles on the basal and columellar lips. The apertural elaborations place it clearly in Chilodontidae , but it lacks the expanded parietal callus shield characteristic of Clypeostoma Herbert, 2012 and the subterminal varix behind the prominently expanded outer lip of Danilia Brusina, 1925 , a distinctive genus of smaller and more elevated shells that originated in the Mesozoic and persists in modern deep-water faunas associated with carbonate substrates.

It is noteworthy that the Crescent Formation chilodontid species also is part of an Early Paleogene incursion of taxa of Tethyan origin into the northeastern Pacific. As noted by Squires and Goedert (1994), the Crescent fauna has received little study. In this sense it is similar to the Nestucca fossils. Both faunas occur in volcanigenic sedimentary facies, although the Crescent taxa are indicative of a shallow bathymetric setting.