Gisortia clarki, INGRAM, 1940

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 : 19-20

GISORTIA CLARKI INGRAM, 1940

FIGS. 6H–J

Gisortia n. sp. Clark and Vokes, 1936. pp. 861, 877, pl. 2, figs. 1, 3. Keen and Bentson, 1944. p. 164.

Gisortia clarki Ingram, 1940 . p. 376, 377, fig. 1. Ingram, 1942. p. 109, pl. 11, fig. 1. Keen and Bentson, 1944. p. 164. Ingram, 1947a. p. 105, pl. 7, fig. 1. Ingram, 1947b. p. 150. Groves and Squires, 2021. p. 241, 242.

Gisortia (Megalocypraea) californica Schilder, 1941 . p. 78 [nomen nudum].

Gisortia (Megalocypraea) clarki Ingram. Schilder and Schilder, 1971 . p. 30, 105. Groves, 1992. p. 101, 102, 106, figs. 3a, 3b. Groves, 1993. p. 11. Groves, 1997. p. 7. Groves and Squires, 2021. p. 242.

Gisortia sp. cf. G. clarki Ingram. Smith, 1975 . p. 469, 479, pl. 2, figs. 9, 13. Not Gisortia clarki Ingram, 1940 .

Megalocypraea aff. M. clarki (Ingram) . Woodring, 1982. p. 725, pl. 85, fig. 3, pl. 86, fig. 3. Not Gisortia clarki Ingram, 1940 .

Gisortia (Megalocypraea) cf. G. (M.) clarki Ingram. Squires and Demetrion, 1994 . pp. 129, 130, fig. 8. Not Gisortia clarki Ingram, 1940 .

Holotype and Type Locality— UCMP 14844 (Figs. H–J), length 121.4 mm, width 96.4 mm, height 65.9 mm. UCMP Locality 4052, “Capay Stage,” Llajas Formation , north side of Simi Valley , Ventura County, California.

Referred Specimens—Hypotype (of Squires and Demetrion, 1994: pp. 129–130) IGM 5953 from LACMIP Locality 401544a (ex CSUN Locality 1544a (internal mold)), lower Eocene (“Capay Stage”), Mesa La Salina and area just to the south, Baja California Sur, México. This specimen, which is significantly smaller than both the holotype of Gisortia clarki and the figured specimen of Gisortia sp. of Perrilliat (1996) (see below), is too poorly preserved to identify with certainty. Additional internal molds of this gastropod are also known from the Bateque Formation, Baja California Sur, México: two from LACMIP Locality 401544a (ex CSUN Locality 1544a), and one from LACMIP Locality 401220 (ex CSUN Locality 1220).

Occurrence— Lower to middle Eocene, California. “Capay Stage,” Llajas Formation, north side of Simi Valley, Ventura County, southern California, and provisionally from the Bateque Formation, Baja California Sur, México.

Etymology— Originally named for the late Bruce L. Clark [1880-1945] ( UCMP)

Description— Shell globose, heavy. Very wide medially. Spire almost totally submerged beneath shell, spire peak projecting (approximately 3.5 mm) above shell. Aperture curves to the left anteriorly and posteriorly. Labrum (outer) and columellar lips broadly rounded. Columella side of the anterior canal apparently compressed dorso-basally at its outermost extremity.

Remarks— Gisortia clarki is known with certainty only from the moderately well preserved holotype. The shell surface of the holotype is well preserved on the base, on the extreme posterior region, on the columellar lateral shell boundary, and on the posterior three-fourths of the outer lip. It is moderately eroded, however, on the dorsal surface, and the greater part of the dorsal convexity is represented by an intact internal mold. The aperture is filled with a matrix, which prohibits a description of the internal surfaces of the columellar and outer lips.

Smith (1975: pl. 2, figs. 9, 13) referred to a late Paleocene cypraeoidean specimen as Gisortia sp. cf. G. clarki from the basal Lodo Formation in the Tumey Hills of central California. This specimen, which has a very inflated dorsum, was mentioned by Squires (1987: p. 35) in his discussion on the distribution of Gisortia in the NEP region. This specimen, however, is recognized and described in this present paper as Cypraeidae , genus and species indeterminate.

Clark and Vokes (1936: p. 877) noted the morphologic similarities of their Gisortia n. sp. and Gisortia tuberculosa ( Duclos, 1825) of Ypresian age in the Paris Basin, France. Gisortia tuberculosa has been reported as early Lutetian age in southern England ( Pacaud and Canevet 2019).

Perrilliat (1996) reported a poorly preserved internal mold identified as Gisortia sp. (hypotype IGM 6761) from the late early Eocene Tepetate Formation near San Hilario, Baja California Sur, México ( IGM Locality 2620). She noted that Gisortia sp. is larger than G. clarki and the spire displays five whorls, which are covered in G. clarki . Because of poor preservation it is difficult to make any positive comparison with G. clarki . The figured specimen of Woodring (1982) ( USNM 647808) from the late Eocene Gatuncillo Formation of Panama is a large internal mold that is indeed a Gisortia but unlikely G. clarki .

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].