Contributions to Zoology, 72 (2-3) 165-168 (2003) SPB Academic Publishing bv, The Hague New Late Cretaceous and Early Cenozoic decapod crustaceans from California, USA: implications for the origination of taxa in the eastern North Pacific Torrey+G. Nyborg¹, Francisco+J. Vega² & Harry+F. Filkorn³ 2 1Department of Natural Sciences, Loma Linda University, Loma Linda, CA 92350, USA; Instituto de 3 Geologia, UNAM, Ciudad Universitaria, Coyoacdn, Mexico D. F. 04510, Mexico; Department of Inverte- brate Paleontology, Natural History Museum ofLos Angeles County, 900 Exposition Boulevard, Los Ange- les, CA 90007, USA Keywords:: Brachyura, Paleocene, Cretaceous, Costacopluma, Coeloma Abstract and worldwide. The of the dorsal shape carapace, including the placement and lengths of the frontal revision of and Paleocene in Recent Cretaceous brachyurans spines, clearly justifies assignment to Raninoides. the collections of the Natural History Museum of Los Angeles Well-preserved fossil material will allow a com- has revealed the ofseveral Based County presence new species. plete description of this new species and provide and their it is evident that upon these fossils ages, they played a further insight into the evolution of the family pivotal role in the originationand subsequent dispersal ofdecapod crustaceans within the eastern North Pacific. Raninidae; The second is the second Archaeopus n. sp., report of the from Cretaceous rocks of Cali- genus Upper Introduction fornia. The downturned subquadrate carapace, long and overall front, relatively large orbits, carapace Prior to this report, diverse occurrences of fossil shape allow confident assignment of this species decapod crustaceans had been reported from Cali- to Archaeopus. Another species, A. antennatus, has fornia (Rathbun, 1926, 1932; Squires, 1980, 2001; unnamed been previously reported from an forma- Bishop, 1988; Tucker et al., 1994; Schweitzer & tion in the Upper Cretaceous of California (Rathbun, Feldmann, 2002). Furthermore, decapod crustaceans in 1926). The new taxon differs having a less of Late Cretaceous and Cenozoic were Early ages subquadrate carapace and better defined regions than believed to be quite rare in California (Schweitzer, A. antennatus. 2001; Schweitzer & Feldmann, 2002). However, The third taxon is Icriocarcinus xestos, a spe- the species describedherein and the known Eocene the cies first reported from late Campanian or early decapod faunas from California (Rathbun, 1926; Maastrichtian Point Loma Formation of California Squires, 2001; Schweitzer & Feldmann, 2002) in- This (Bishop, 1988). genus was originally placed dicate that California is indeed a well-represented in the Carcineretidae and subsequently reassigned region for fossil decapod crustaceans. to the Goneplacidae (Schweitzer et al., 2002). New material extends the of the geographic range genus Mesozoic crustaceans northwards into central California. Currently, based broad upon very morphological characteristics, the The is within the decapod fauna from the Maastrichtian Moreno genus Icriocarcinus placed Gonepla- of cidae et With the well- Formation Merced County, California, includes (Schweitzer al., 2002). many three species of brachyurans; preserved and complete specimens available for The first is Raninoides the it is that the can be confi- n. sp., representing study now, hoped genus earliest the level. occurrence of the genus both in California dently placed at family 166 T. G. Nyborg et al. — Cretaceous and Paleocene decapods from California and Cenozoic crustaceans in having a more distinct projected front, more triangular anterolateral spines, and a less distinct The Cenozoic medial frontal Early occurrences of decapod crus- groove; taceans in California also The third is is the first are very significant. species Archaeopus n. sp. from the of the in Decapod crustaceans middle to late Pale- report genus Paleocene rocks. The oldest ocene Coal Canyon Formation are the only speci- occurrence is in Cretaceous strata of the west coast of this known from the of of North America Schweitzer mens age West Coast (Rathbun, 1908; & North America. These specimens also are important Feldmann, 2001; Schweitzer et ah, 2002, submit- because they indicate that certain Late Cretaceous ted). The youngest occurrence is in the late Eocene decapod taxa persisted through the Cretaceous- of British Columbia, Canada (Schweitzer et ah, extinction and survived least The is endemic the North Tertiary (K/T) event at submitted). genus to Pa- into the Paleocene. Five have been cific with all but one of the fossil species recog- occurrences along nized: the west coast of North America; Nagao (1941) The first is described species Costacopluma n. sp. within Archaeopus ezoensis from Cretaceous Paleocene rocks of Californiaconfirms that the rocks of genus Japan. was after the K/T extinction The fourth of is from widespread event taxon note Zanthopsis n. sp. (Rimy, 1960; Collins & Rasmussen, 1992; Collins the Paleocene of California clearly has the four- et al., 1994; Feldmann & Martins-Neto, 1995; Feld- lobed front, vaulted carapace, and tubercles on the mann et al., 1995, 1997). A subrectangular cara- branchial region which justify placement of the new and cardiac within the With the pace, narrow front, angular region clearly species genus Zanthopsis. re- allow within the placement of this species genus assignment of previous taxa referred to Zanthopsis Costacopluma. Records of Costacopluma from the (Beurlen, 1958; Bishop, 1988; Schweitzer et ah, Mexcala the Formation ofthe State of Guerrero, Mexico, 2000), present species is the earliest represen- that this in America since tative of the Another suggest genuswas present genus. species, Zanthopsis Coniacian times (Vega & Feldmann, 1992) and is sternbergi, was reported from the Cretaceous of as old (or possibly older) than the purported first California (Rathbun, 1926), but it is only known record of the & Mor- from the genus from Africa (Collins a questionable claw fragment and thus These indicate that of the ris, 1975). findings the genus occurrence species cannot be confirmed; in was well established the eastern North Pacific Finally, Cyclocorystes aldersoni also occurs in region during its evolutionary span; the Coal Canyon Formation, the species having been The second is Coeloma described ba- taxon n. sp., represent- originally by Squires (1980) on the the earliest of the both in sis of ing occurrence genus seventeen specimens collected from this for- California and worldwide. The referred mation. The other specimens only species referred to this genus here have with four- is the a flat, trapezoidal carapace a type species, Cyclocorystes pulchellus Bell, toothed front and four teeth along the anterolateral 1858, from the Eocene London Clay of England. margin. These morphological characteristics clearly the of this within the permit placement species genus Coeloma. the believed to Previously, genus was Discussion have dispersed to North America from Europe af- the ter early Eocene (Schweitzer et ah, 2002). The latest Cretaceous-earliest Cenozoic strata along However, with more than a dozen the California of North America well-preserved coast preserve a available for the specimens currently study, genus fairly robust record of the origination and evolu- now have had its first in appears to appearance tion of fossil decapod crustaceans. Previously it had California and subsequently dispersed to Europe been postulated that southern latitude and Tethyan the Eocene. Another Coeloma of by early species, regions had a higher number decapod taxa origi- martinensis, was described from the late Eocene nations, with subsequent dispersals to the eastern Martinez Formation of California by Rathbun North Pacific (Schweitzer, 2001; Schweitzer et ah, The new differs from (1926). species C. martinensis 2002). Flowever, with continued study of the deca- to 72 - Contributions Zoology >, (2-3) 2003 167 from this pod faunas region as exemplified by the Collins JSH, Rasmussen HW. 1992. Upper Cretaceous-Lower above it is clear that Tertiary decapod crustaceans from West Greenland. Gronl. descriptions, becoming many geol. Unders. Bull. 162: 1-46. of the taxa described from rocks of the West Coast Collins JUS, Higgs R, Cortitula B. 1994. A new crab, of North America actually originated within the Costacopluma bifida (Crustacea, Decapoda) from the eastern North Pacific. Palaeocene of Venezuela. Bull. Mizunami Fossil Mus. 21: It has been that Ceno- reported (Schweitzer, 2001) 29-34, pis 8, 9. zoic decapods from lower latitude regions, such as Fcklmann RM, Martins-Neto RG. 1995. Costacopluma California, exhibit significant differences at the nordestiana n. sp. (Decapoda: Retroplumidae) from the Maria FarinhaFormation (Paleocene) of Brazil. Jour. Paleo. generic level from those occurring at higher lati- 69: 610, 611. tude localities in Oregon, Washington, and British Feldmann RM, Fernanda Rodriguez M, Martinez GA, Columbia. there are a few Although only genera M. 1997. Aguirre-Urreta Costacopluma salamanca new that can be found in and state from every country species (Decapoda, Retroplumidae) from the Salamanca British Columbia there Formation of Jour. Paleo. to Mexico, are actually many (Danian) Patagonia, Argentina. 71: 125-130. geographic overlaps along the margin of the con- Fcldmann RF, Casadio S, Chirino-Galvez tinent. The L, Aguirre- genus Costacopluma, which is very Urreta M. 1995. Fossil decapod crustaceans from the common in the Upper Cretaceous of the eastern Jagiiel and Roca Formations