Gisortia, Jousseaume, 1884

Groves, Lindsey & Squires, Richard L., 2023, Revision of northeast Pacific Paleogene cypraeoidean gastropods, including recognition of three new species: implications for paleobiogeographic distribution and faunal turnover, PaleoBios 40 (10), pp. 1-52 : 20-22

GISORTIA SP.

FIGS. 6K–M

Gisortia clarki Ingram, 1940 . Squires, 1987. p. 35, figs. 39–41 [as Gisortia new species? in caption]. Not Gisortia clarki Ingram, 1940 .

Referred Specimen—Hypotype (of Squires, 1987) LACMIP 16243.1 , LACMIP Type 7466 ( Figs. 6K–M ), LAC- MIP Locality 16243 [= Locality 40848 [ex CSUN Locality 848]), Juncal Formation, Canton Canyon, Ventura County, California.

Occurrence— Juncal Formation. “Capay Stage,” Turritella uvasana infera fauna, LACMIP Localities 16156 [= LACMIP Locality 40837; ex CSUN Locality 837] and 16243 [= LACMIP Locality 40848; ex CSUN Locality 837], in an area just east of Sharps Canyon and southeastward toward Canton Canyon, Whitaker Peak area, Los Angeles County, southern California.

Description— Shell large, length 122 mm, width 75 mm, height 51 mm. Shell ovate. Anterior and posterior ends flattened somewhat and projecting. Aperture narrow, curving left posteriorly but becoming less curved anteriorly. Outer lip (anterior half) with several small teeth; presence of any dentition on rest of aperture is not known.

Remarks— A large complete specimen is known,but it is poorly preserved as a partial internal mold (steinkern). In addition, a large fragment (length 90 mm) was found in same-age rocks of the Juncal Formation approximately 0.5 km to the west in Sharps Canyon of the Whitaker Peak area ( Squires 1987), LACMIP 40837.1, LACMIP Locality 16156 [= LACMIP Locality 40837; ex CSUN Locality 837]. Most of the dorsal shell convexity of the complete specimen is represented by an internal mold (steinkern), and its spire is obscured by matrix. The Juncal Formation specimen of Gisortia sp. differs from Gisortia clarki by having an ovate shell, a narrower shell, a narrower inner lip, and the presence of wide, flattened anterior and posterior margins.

The Juncal Formation specimens of Gisortia sp. are somewhat similar to a specimen of Gisortia gigantea Münster in Keferstein, 1828, from India as illustrated by Vredenburg (1927: p. 59, 60, pl. 13, fig. 2). Gisortia gigantea , which is of middle Eocene (Lutetian age) and known from France, England, and India, can have a wide range of variation in its posterior canal region owning to the absence or presence of elaborately shaped phlanges and/or wide spines. These variants usually have been assigned to subspecies of Gisortia gigantea or assigned a different species name. See Pacaud (2008) for clarifications. The Juncal Formation species of Gisortia differs from G. gigantea by having a more elongate shell shape with a posterior flattening of the shell and no evidence of any posterior phlanges.

Figures

Figure 6 (previous page) A–C. Protocypraea? sp. 1, Oyster Bay Formation, Paleocene, Appian Way, Central Is- land District, Vancouver Island, British Columbia, Canada. Dorsal (A) and (B) left (columellar) views, 1.8x, length 45.5 mm, width 29 mm, height 22 mm, of CDM 997.91.3, informal locality AP3. (C) Oblique view posterior in- complete end of shell showing sunken area encircling base of spire, width of field of vision 28.7 mm. D–G. Protocypraea? sp. 2, Lodo Formation (Paleocene, Thanetian Stage), Tumey Hills, Fresno County, central California, LACMIP Locality 26456 [ex UCLA Locality 6456]. Basal (D) view, 1.6x, length 42.2 mm, width 28.6 mm, height 18.5 mm, of hypotype LACMIP 26456.6, LACMIP Type 14925, Basal (E), dorsal (F), right (labral) (G) views, 1.44x, length 50 mm, width 28 mm, height 27 mm, of hypotype UCMP 14208, UCMP Locality A9717. H–J. Gisortia clarki Ingram, 1940, Llajas Formation (Eocene, “Capay Stage”), north side Simi Valley, Ventura County, southern Cali- fornia. Basal (H), dorsal (I), and right (labral) side (J) views, 0.5x, length 121.4 mm, width 96.4 mm, height 65.9 mm, of holotype UCMP 14844, UCMP Locality 4052. K–M. Gisortia sp., Juncal Formation (Eocene, “Capay Stage”), Whitaker Peak, Ventura County, southern California. Basal (J), dorsal (K), and right (labral) side (M) views, 0.5x, length 122 mm, width 75 mm, height 51 mm, of hypotype LACMIP 16243.1, LACMIP Type 7466, LACMIP Locality 40848 [ex CSUN Locality 848].