Echinophoria trituberculata, (WEAVER, 1912)

Squires, Richard L., 2019, Revision of Eocene warm-water cassid gastropods from coastal southwestern North America: implications for paleobiogeographic distribution and faunal-turnover, PaleoBios 36, pp. 1-22 : 12-14

ECHINOPHORIA TRITUBERCULATA ( WEAVER, 1912)

FIG. 4I–P

Morio tuberculatus var. trituberculatus Weaver, 1912 . p. 39; pl. 3, fig. 35.

Galeodea tuberculata (Gabb) . Dickerson, 1915. pl. 6, figs. 3a, 3b.

Galeodea trituberculata (Weaver) . Weaver and Palmer, 1922. p. 37; pl. 11, figs. 23, 27. Tegland, 1931; p. 408; pl. 59, fig. 1; pl. 60, figs. 1–4. Weaver, 1942. p. 404; pl. 78, figs. 10–15; pl. 79, figs. 1–4, 8. McWilliams, 1971. pl. 2, fig. 8. Moore, 1984. figs. A, D, E, G, H. Nesbitt, 1998. pl. 1, fig. 5.

Galeodea petrosa ( Conrad, 1855) . Schenck, 1926. p. 82; pl. 14, figs. 5–11.

Galeodea pretrosa [sic] (Conrad). Clark, 1929. pl. 14, figs. 1, 6.

Echinophoria trituberculata (Weaver) . Durham, 1942. p. 184; pl. 29, fig. 10. Moore, 1984. figs. 4-A, D, E, G. H. Nesbitt, 1995. table 1.

“ Galeodea ” tritubreculata [sic] (Weaver). Durham, 1944. p. 166.

Phalium (Echinophoria) trituberculatum (Weaver) . Abbott, 1968. p. 109; pl. 93 (three views).

Echinophoria cf. E. trituberculata (Weaver) . Givens, 1974. p. 79.

Primary Type Material— Holotype CASG 7612 , UWBM Locality 232, north bank of Cowlitz River 2.4 km east of Vader , Cowlitz Formation , Lewis County, southwestern Washington.

Material examined— The twenty-eight specimens include: Hypotypes ( LACMIP 14836–14838 ) and 25 unfigured specimens: 15 from LACMIP Locality 22430 ( Tejon Formation , Grapevine Canyon , Kern County, southern California, nine from LACMIP Locality 5654 ( Cowlitz Formation , near Vader , Lewis County , southwestern Washington), one from LACMIP Locality 2777 ( Llajas Formation , north side Simi Valley , Ventura County , southern California).

Emended description— Shell small to medium size (up to 60 mm height); transition at approximately 22 mm height from immature specimens (fusiform with apertural sculpture abundant) to mature specimens (globose quadrate shape with apertural sculpture absent). Spire medium high. Sutural cord can be present. Sutural ramp low. Last whorl with three carinae (anteriormost carina slightly weaker), all with nodes, which become progres- sively stronger toward outer lip. Carina on shoulder with 11 widely spaced spinose tubercles; second carina with 11 nodes; third carina with nine nodes, but nodes can be essentially obsolete toward aperture. Shell surface mostly covered with minute spiral threads generally all same size, but finer threads can be irregularly and randomly present (i.e., not in a repeating pattern); base of last whorl with spiral ribs, becoming stronger anteriorly. Columellar callus moderately thick on immature specimens and bearing lirae in parietal area and bearing granules on posterior part of columella; columellar callus without sculpture and thin on mature specimens, with nodes showing through. Columella on mature specimens bearing faint spiral lines beneath callus. Columella long and overall straight, except at twisted anterior end. Peristome with moderate notch. Anterior siphonal canal with deep groove adajacent to twisted columellar end; fasciole well developed, especially over angulate adaxial side of canal. False umbilicus present. Outer lip on immature specimens thickened, with interior bearing numerous elongate denticles separated by deep grooves on immature specimens. Outer lip on mature specimens narrow, reflected, and with interior denticles or grooves becoming much less apparent with growth. Episodic varices rare. Terminal varix present.

Stratigraphic occurrence— Middle Eocene to low- ermost upper Eocene, southwestern Washington to southern California. Lower part of “ Tejon Stage ”: Matilija Sandstone, Pine Mountain area, Ventura County ( Givens 1974). Tejon Formation ( Anderson and Hanna 1925), probably Liveoak Member, Kern County, southern California. Uppermost part of “Tejon Stage,” Cowlitz Formation, Lewis County, southwestern Washington; Tukwila Formation, King County, southwestern Washington (Mc- Williams 1971, Nesbitt 1998).

Remarks— Specimens from the Cowlitz Formation show the best preservation. Specimens from the Tejon Formation are commonly well preserved fragments, which are missing the anterior canal because of improper removal of the well-indurated rock matrix. Early workers assigned this species to genus Galeodea , and starting with Durham (1942), workers assigned it to genus Echinophoria . Well preserved specimens of Echinophoria are characterized by the presence of a longitudinal spiral cord on the anterior canal ( Beu 2008: p. 287), as well as the development of a sutural cord. Development of both of these features on the CSWNA specimens of E. trituberculata can be absent, extremely faint (Tejon Formation specimens), or prominent (Cowlitz Formation specimens). These differences are probably the function of preservation.

Some specimens of Echinophoria trituberculata can resemble Galeodea tuberculiformis , but E. trituberculata differs by having a shell with a larger maximum size (up to 60 mm vs. 34 mm), its spire can be less submerged, ramp flatter, sutural cord present on all whorls, spirals stronger on the last whorl and with more spinose tubercles, spirals coarser on neck, fine sculpture not beaded and rarely cancellate or not at all, parietal shield commonly not present or weaker. In addition, E. trituberculata has its anterior siphon more twisted, left side of fasciole angulate (keeled) rather than rounded and with deeper channel, anterior canal notched, longer and also wider with a slight longitudinal indentation, and episodic varices not as common.

Echinophoria tritubercula differs from the late Eocene to early Oligocene E. dalli ( Dickerson, 1917) , found predominantly in the Keasey Formation in the Veronia area of northwest Oregon ( Hickman 1980), in having weaker spiral sculpture between carinae, thicker parietal callus, and a thicker outer lip.

Echinophoria trituberculata differs from the latest Eocene to early Oligocene Echinophoria fax ( Tegland, 1931) , found predominantly in the Lincoln Creek Formation in western Washington, by having no fourth carina, fewer (10 versus 14) nodes on shoulder of last whorl, noticeably finer less spiral sculpture between the carinae on the last whorl, and weaker spiral ribs on base of last whorl.

Weaver and Kleinpell (1963: p. 190, pl. 25, fig. 11) reported Echinophoria trituberculata (Weaver) from the Matilija Sandstone [“Tejon Stage”] in the Pine Mountain area, Santa Barbara County, southern California. Their report is based on a poorly preserved single specimen whose anterior canal is missing, thus identification as to genus and/or species is not possible.

Figures

Figure 4. See caption on the bottom of page 11.