PaleoBios 36:1–7, December 26, 2019 PaleoBios OFFICIAL PUBLICATION OF THE UNIVERSITY OF CALIFORNIA MUSEUM OF PALEONTOLOGY CHARLES L. POWELL, II and DANIEL L. GEIGER (2019). Two new Miocene limpets (Fissurellidae) from southern California, with notes on other fossil occurrences of the family in northwestern North America. Cover: New limpet species, Scelidotoma aldersoni n. sp. (left) and Fissurella? stantoni n. sp. (right), from the Miocene of southern California. Citation: Powell, II, C.L. and D.L. Geiger. 2019. Two new Miocene limpets (Fissurellidae) from southern California, with notes on other fossil occurrences of the family in northwestern North America. PaleoBios, 36. ucmp_paleobios_46304. Two new Miocene limpets (Fissurellidae) from southern California, with notes on other fossil occurrences of the family in northwestern North America CHARLES L. POWELL, II1 and DANIEL L. GEIGER2 1U.S. Geological Survey, Menlo Park, CA 94025, USA; [email protected] 2Santa Barbara Museum of Natural History, 2559 Puesta del Sol, Santa Barbara, CA 93105, USA; [email protected] Fissurella? stantoni n. sp. and Sceli- dotoma aldersoni n. sp., are described from Miocene deposits in southern California. Fissurella? stantoni Twois described new fissurellid from a single limpets specimen (Mollusca: from Gastropoda: the middle Fissurellidae), Miocene Topanga Canyon Formation in the Santa Monica Mountains, Los Angeles County, California. Scelidotoma aldersoni is described from two speci- specimen of an internal mold from the middle Miocene “Vaqueros” Formation on Santa Cruz Island, Santa mens,Barbara one County, from the southern middle California.Miocene Topanga Other unreported Canyon Formation, fossil occurrences and another of provisionally Scelidotoma (cf.)are aidentified juvenile specimen attributed only to genus collected in the middle Eocene Crescent Formation in Washington state and S. bella from the Pliocene part of the San Diego Formation, San Diego County, California. The Scelidotoma occurrences extend the chronostratigraphic range of S. bella from the Holocene (living) to the middle Pliocene, and the range of the genus back to the middle Eocene. Keywords: Mollusca, Gastropoda, Fissurellidae, Scelidotoma, Fissurella, Paleogene, Neogene INTRODUCTION Here we describe Fissurella? stantoni n. sp. from a Fissurellidae Fleming (1822) are a common compo- single specimen collected from the Topanga Canyon nent of the lower intertidal to subtidal regions around the Formation in the Santa Monica Mountains. In addition, world (Kaicher 1988), including the west coast of North we describe a new species of Scelidotoma from two speci- America (McLean 1971, 1978). They are less common be- mens, one from the middle Miocene Topanga Canyon For- yond the continental shelf in deeper water (e.g., McLean and Geiger 1998, Suárez-Mozo and Geiger 2017). Their from the middle Miocene “Vaqueros” Formation on Santa fossilization potential should be good due to a robust, Cruzmation, Island, and anotherSanta Barbara steinkern County. provisionally An indeterminate identified entirely calcitic, limpet-shaped shell (Geiger et al. 2008). juvenile Scelidotoma from the middle Eocene Crescent However, the rocky habitat they predominantly live in Formation of western Washington is also mentioned. imposes a negative taphonomic bias through high-energy The Topanga Canyon Formation in the Santa Monica conditions and a typical erosive depositional setting Mountains of northern Los Angeles County contains the (Woodring 1931, Carter 1972, Kotaka and Ogasawara largest and best preserved middle Miocene molluscan 1974, Parsons and Brett 1991 fauna from a single formation in California. It exceeds in the California fossil record where Keen and Bentson those of the Kern County described from multiple forma- (1944) recognized only six taxa ).in This the familybias is during reflected the tions by Addicott (1970 Paleogene-Neogene: two Fissurella Bruguière (1789), fossils in rocks later referred to the Topanga Forma- one possible Fissurella, and three Diodora Gray (1821). tion (Kew 1923, 1924) is). Thethat firstof Arnold report ( 1907on molluscan). Yerkes There is also a report of a questionable Fissurella from and Campbell (1979) raised the Topanga Formation to the Mesozoic of California (Kiel et al. 2008). group status and included within it, from base to top, the Topanga Canyon Formation, the Conejo Volcanics, and the Calabasas Formation. Takeo Susuki (University *author for correspondence Citation: Powell, II, C.L. and D.L. Geiger. 2019. Two new Miocene limpets (Fissurellidae) from southern California, with notes on other fossil occurrences of the family in northwestern North America. PaleoBios, 36. ucmp_paleobios_46304. Permalink: https://escholarship.org/uc/item/8x89w4pb Copyright: Published under Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC-BY-NC-SA) license. LSID: urn:lsid:zoobank.org:pub:B0EA976F-85FF-40C6-A445-2984EAACC842 2 PALEOBIOS, VOLUME 36, 2019 of California-Los Angeles, deceased) worked on the To- U.S. Geological Survey specimens being curated at the panga Canyon Formation fauna for many years. How- University of California Museum of Paleontology (UCMP). ever, none of his work was formally published. Susuki’s height=greatest investigations have been resumed by John Alderson and distance between dorsal and ventral termini; Robert Stanton (Natural History Museum of Los Angeles lengthMeasurements=greatest distance are defined between as follows: anterior and poste- County, Invertebrate Paleontology [LACMIP]). However, rior termini; width=greatest distance between left and right termini. continuing work and are described here in their honor. Institutional abbreviations—CSUNR, California theMany fissurellids early California in this study geologists are not assigned included formation in their State University Northridge, Northridge, California; LAC- names on the basis of their enclosed fauna (biostrati- MIP, Invertebrate Paleontology Section, Natural History graphically) not by correlating the rocks composing the Museum of Los Angeles County, Los Angeles, California; formation (lithostratigraphically) as geologic formations LACMM, Malacology section, Natural History Museum should be correlated. Complicating this some formation of Los Angeles County, Los Angeles, California; SBMNH, names in California have been used in both a lithologic Santa Barbara Museum of Natural History, Santa Barbara, California; SDSNH, Paleontology section, San Diego Soci- in the literature. The “Vaqueros” Formation in the Chan- ety of Natural History, San Diego, California; UCMP, Mu- neland Islands biostratigraphic is one of these sense units. causing The significant type Vaqueros confusion For- seum of Paleontology, University of California at Berkeley, mation was named for outcrops from Vaqueros Canyon in Berkeley, California; UCSB, University of California, Santa the Santa Lucia Mountains, Monterey County, California Barbara, Goleta, California; USGS, U.S. Geological Survey, that are of late Oligocene age (Miles and Rigby 1990). Washington, D.C.; USGS M, U.S. Geological Survey, Menlo The rocks unit “Vaqueros” Formation on the California Park, California (now housed at UCMP). Channel Islands, where the second Scelidotoma specimen was collected, is lithologically different from the type SYSTEMATIC PALEONTOLOGY Vaqueros and should be given a new name, but that is GASTROPODA beyond the scope of this report. VETIGASTROPODA Fossils from the “Vaqueros” Formation on California’s FISSURELLIDAE Cuvier, 1795 Channel Island are also not biostratigraphically similar EMARGINULINAESalvinia-Plawen, 1980 to fauna reported from the type Vaqueros Formation FISSURELLA Fleming, 1822 (Loel and Corey 1932, United States Geological Survey Children, 1834 (USGS) collections now housed at University of California Diagnosis—Shells areBrugui conicalère, with 1789 an overall oval Museum of Paleontology), and based on unpublished outline, with or without inclined sides, topped by a cen- data on fossils from Santa Rosa Island (University of trally-placed apex wholly absorbed by an oval foramen Calfornia-Santa Barbara and USGS collections) and in mature specimens. The foramen is bordered inside by southern Orange County (LACMIP, San Diego Society a ring of callus that is not truncated or excavated poste- of Natural History collections) are middle Miocene in age correlating biostratigraphically with the younger Type species—Fissurella nimbosa Linnaeus (1758), riorly. Sculpture is chiefly radial. “Temblor” California provincial molluscan stage (CPMS) by monotypy. (19.5–12.0 Ma; Smith 1991) further supporting the need Remarks—The difference between Fissurella and for a new name for the “Vaqueros” Formation on Cali- the closely related genus Diodora is in the shape of the fornia’s Channel Islands (name used in quotes to signify foramen at the apex and from the interior. In Fissurella it does not correlate with the type Vaqueros Formation the foramen is oval, while in Diodora the posterior end and not to be confused with the 32.6–19.5 Ma “Vaqueros” of the foramen is truncated. The interior of the shell de- CPMS [Smith 1991]). scribed here is not available so the genus determination is questioned. MATERIALS AND METHODS FISSURELLA? STANTONI The specimens reported here from the Topanga Can- Powell and Geiger, n. sp. yon Formation were pointed out to the senior author Diagnosis—Fissurella?Figs. stantoni 2, 5 n. sp. differs from all by John Alderson (LACMIP research associate) who is - an expert