Protocypraea simiensis (Nelson, 1925) Groves & Squires, 2023

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 : 16-17

PROTOCYPRAEA? SIMIENSIS ( NELSON 1925) N. COMB.

FIGS. 5M–O

Cypraea simiensis Nelson, 1925 . p. 397, chart opposite p. 402, 425; pl. 57, figs.3a–3c. Ingram, 1942. pp. 105, 106; pl. 9, fig. 18. Keen and Bentson, 1944. p. 152. Ingram, 1947a. p. 101; pl. 6, figs. 18, 19. Ingram 1947b:149.

Propustularia simiensis (Nelson) . Schilder, 1932. p. 159 [as P. simiensis ]. Schilder, 1941. p. 89. Weaver MS [1959]. p. 483, pl. 21, figs. 5, 6. Schilder and Schilder, 1971. pp. 59, 155. Groves, 1992. p. 106. Groves, 1993. p. 11. Groves, 1997. p. 7 [as P. simiensis ]. Lorenz, 2017. p. 211. Groves and Squires, 2021. p. 227 [as Cypraea ].

Propustularia simiensis (Nelson) . Zinsmeister, 1974. pp. 130, 131, pl. 13, figs. 10, 11. Zinsmeister, 1983. p. 64, pl. 2, figs. 25, 26. Not Protocypraea? simiensis (Nelson) .

Siphocypraea (Muracypraea) koninckii ( Rouault, 1850) . Dolin and Dolin, 1983. p. 46 (table). Not Protocypraea? simiensis (Nelson) .

Propustularia cf. P. simiensis (Nelson) . Paredes-Mejia, 1989. p. 198–200, pl. 4, figs. 17–19. Not Protocypraea? simiensis ( Nelson, 1925) .

Propustularia sp. cf. P. simiensis (Nelson) . Perrilliat, 2013. p. 133, 134, fig.4.1, 4.2. Not Protocypraea? simiensis ( Nelson, 1925) .

Holotype and Type Locality— UCMP 30498 (Figs. 5M–O), length 33.1 mm, width 24.5 mm, height 17.4 mm. UCMP Locality 3818, upper Santa Susana Formation , Runkle Canyon , Simi Hills , Ventura County, southern California.

Occurrence— Upper Paleocene (Thanetian Stage), Santa Susana Formation, north side of Simi Hills, Ventura County, southern California ( Nelson 1925). Protocypraea? simiensis is known only with certainty from high in the stratigraphic section of the Santa Susana Formation in Runkle Canyon located on the north side of the Simi Hills, Ventura County, southern California. The type locality of Protocypraea? simiensis yielded just this species, and no other mollusks, Both of the other cypraoideans, Propustularia kemperae and Eocypraea novasumma , known from the Santa Susana Formation, occur much lower in the Paleocene stratigraphic section. Zinsmeister (1974: pp. 130, 131; pl. 13, figs. 10, 11, Zinsmeister, 1983: p. 64, pl. 2, figs. 25, 26. Zinsmeister and Paredes-Mejia, 1988: p. 13) reported Propustularia simiensis in the Santa Susana Formation from his so-called “Martinez marine member,” but poor preservation prevents the identification of this specimen. Squires (1997: p. 851) noted that it was based predominantly on float material. In summary, based on its stratigraphic position, the Santa Susana Formation occurrence of P.? simiensis is reported here as of Thane- tian Stage age.

Etymology— Originally named for Simi Valley, Ventura County, southern California.

Description— Shell of medium size. Smooth. Ovate, moderately inflated, dorsum can be elevated, especially posteriorly. Posterior end of shell wide, somewhat flat- tened, and projecting. Anterior end of shell missing (on holotype). Right-lateral margin, near base, with raised border (beveled basally). Dorsal posterior end if shell wide, flattened and projected (right side more than left side). Spire area (halfway between top of dorsal surface and posterior terminus of shell) covered with small but prominent protuberance (bump). Aperture narrow, moderately curved abaxially posteriorly, fairly straight medially, curved and widening anteriorly. Outer lip swollen with teeth numerous, small, and evenly spaced to at least mid-point of basal surface but becoming un- detectable posterior of mid-point. Inner lip teeth few (approximately five near anterior end) to numerous, strong to moderately strong (strongest near anterior end), and can be restricted to anterior end of shell or present along most of aperture.

Remarks— Nelson’s Cypraea simiensis , which does not fit into Schilder’s (1927) description of Propustularia , is known only from the holotype. It has good preservation, but, unfortunately, its anterior end is missing, thereby only allowing questionable identification as to genus. Therefore, it is herein provisionally assigned to Protocypraea based on the partially exposed spire and weakly developed dentition.

Paredes - Mejia (1989: pp. 198–200, pl. 4, figs. 17–19) and Perrilliat (2013: p. 133, figs. 4.1, 4.2) illustrated the same specimen, with different hypotype numbers, of the so-called Propustularia cf. P. simiensis (Nelson) from the same locality in the Sepultura Formation in Baja California, México. Paredes-Mejia (1989) referred to this specimen as hypotype IGM 4390, PU Locality 1300-2, Sepultura Formation, San Carlos Mesa, northern Baja California. Perrilliat (2013) referred confusingly to this specimen as hypotype IGM 4366 [=hypotype 4390 of Paredes-Mejia (1989)], PU Locality 1300-2, Sepultura Formation, San Carlos Mesa, northern Baja California. This worn cypraeoidean specimen is too poorly preserved to positively identify as to genus and species.