Late Quaternary Chorus Frog (Pseudacris) from the Channel Islands, California
Jim I. Mead
Mammoth Site of Hot Springs South Dakota, jmead@mammothsite.org
Justin Wilkins
Mammoth Site of Hot Springs South Dakota, justinw@mammothsite.org
Paul W. Collins
Santa Barbara Museum of Natural History, Paul@sbnature2.org

Abstract

Fossil and subfossil remains of the vertebrate faunas from the northern Channel Islands, southern California, have been studied for many decades. Contin-ued interest has focused on skeletal remains of birds, rodents, and mammoths from archaeological and paleontological localities, but considerably less attention has been placed on the detailed description of the herpetofauna (salamanders, anurans [frogs and toads], lizards, and snakes) on the Channel Islands. We present descriptions of an ilium of an anuran from Santa Rosa Island (Larramendy North; radiocarbon dating at least 13,393 calibrated years ago) and two tibiofibulae San Miguel Island (Daisy Cave) dating from earliest and middle late Holocene layers. We identify the fossil il-ium as Pseudacris sp. (chorus frog): 1) it is the lowest level that skeletal morphology permits us to attempt, 2) realizing that it appears morphologically closest to P. regilla, and 3) yet realizing that not all species of Pseudacris and Hyla have been directly com-pared or are understood. The extant amphibian fauna on these islands is depauperate. The remains presented here represent the first description of a fossil anuran from the northern Channel Islands. It is now understood that a chorus frog lived on glacial-age Santarosae Island, yet it is not understood when its distribution was reduced to just the present two largest islands, Santa Rosa and Santa Cruz.

Investigation of the Holocene and late Pleistocene terrestrial vertebrate faunas from the northern Channel Islands (NCI) off the coast of Santa Barbara California has received attention for many decades (see discussions in Damiani and Garcelon 2009)(Fig. 1). Of sustained interest has been the analysis of cultural artifacts along with skeletal remains of birds, rodents, and mammoths from archaeological and paleontological localities (e.g., Erlandson et al. 1996; Guthrie 1980, 1998, 2005; Johnson et al. 2002; Ainis and Vel-lanoweth 2012; Allen 2013; Muhs et al. 2015). What has received considerably less attention other than cursory listings is the detailed assessment of the herpetofauna (salamanders, anurans [frogs and toads], lizards, and snakes). The first and only insular Pleistocene-age salamander (Batrachoseps) from the Channel Islands was recovered in association with a late Pleistocene pygmy mammoth (Mammuthus exilis; 12,840 ± 140 yr B.P., CAMS-24429, AMS analysis; Agenbroad 1998, 2002; Mead et al. 2004). Here we report on the skeletal re-mains of the first fossil frog from localities on the NCI: one ilium from Laramendy North, Santa Rosa Island and two leg elements from Daisy Cave A, San Miguel Island.

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