The first Mesozoic mammal from California """ "

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Apr 15, 2003 - 2003 University of California Museum of Paleontology. The first ... 2Geology Department and Natural History Museum, Sierra College, Rocklin,.
PaleoBios 23( 1):20-23, April 15, 2003 © 2003 University of California Mu seum of Paleontology

The first Mesozoic mammal from California

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GRE GORY P. WILSON!, RI CHARD P. HILTON 2, and ERIC S. GO H RE 3 IDepartment of Integrative Biology and Museum of Paleontology, University of Californ ia, Berkeley, Californ ia 94720; [email protected] u. 2Geology Departme nt and N atural History Museum, Sierra Co llege, Rocklin , California 95 677 ; rhilton@sierra college.edu. 3field paleontologist, O roville, Californ ia 95 966 A new specim en from the U pper Cretaceo us (Cam panian) ma rine dep osits of the C hico Formatio n represents the first Mesozoic mam mal from Califo rn ia. T he specime n adds to the fau na, whi ch inclu des din osaurs, t urtles, pterosaurs , and birds, known fro m t his nearshore terrestr ial environment . T he speci men, a met acarp al, cannot be confidently iden tified beyond t he level o f Ma mmalia . However, the size o f th e spec ime n suggests t hat the an imal was a medium to large-sized Mesozoic mammal, larger tha n t he Late Cret aceo us eut herian Ba ru nlestes butleri an d co m para ble to t he modern day E uras ian hedgehog ( Er in aceus europaeus).

INTRODUCTION Nort h America's record of Cretaceous mammals suffers from a clear geographic bias-few localities are known o utside t hose from the fluvial de posits of the Western Interi or. As a result, our view of early mammalian history is skewed toward th e faunas from these ancient coastal lowlands along the western margin ofthe Western Interior Seaway. Mammalian faunas from other environm ent s and areas west of th e present day Rocky Mountains are sparse. Localities have only been reported from Baja Californ ia del Norte (LiUegraven 1976) and Eureka Coun ty, Nevada (Clemens et al. 1979 ). Thus far, non e have been reported from California. UIUS car, nom: nave oeen repo rted rrorn Cailtor rua. Most of Californ ia's Me sozoic sedimentary ro cks are marine deposits, and consequ entl y, Mesozoic terrestrial verteb rates from th e state are relatively rare. T he only verte brate fossils known from terrestrial deposits are dinosa ur tra cks from the Aztec Sandstone (Lower Jur assic) in the M ojave D esert (Reynolds 1989) and dinosaur bone and to oth fragm ents fro m th e Trail Fo rmation (Jurassic) of the northern Sierra Nevada (Christe and Hilton 2001 , Hil ton

of Natural History, Rocklin , CA vertebrate locality; V M, vert ebrate mammal fossil specimen prefix for Sierra College Museum of Natural History. GEOLOGY During the Late Cre taceo us (99- 65 million years ago) the shoreline of Californ ia was generally just inland from t he present western base of the Sierra and Klamath Mountain Prov inces (Ni lsen , 1986). The present day Sacramento and San Joa quin Valleys were t hen an ocean shelf and slope area receiving sedime nt from rivers along the mo untainous shore (Fig . 1). shore (Fig . 1).

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All other evidence of California's Mesozoic terrestrial life has come from marine deposits. Besides fossils of fish, plesiosaurs, mosasaurs, and sea turtles (Dupras 198 8, Welles 1943, Parham and Stidham 1999 ), the m arine Grea t Valley Group has yielded information regarding the nearshore terrestri al fauna . Thi s includes fossils fro m th e occasional dino saur carcass th at floated out to sea and sank (D erriere 1985 , D eCourten 1997, Hilton and Antuzzi 199 7 ), as well as fossils ofterrestrial turtles, flying reptiles, and birds (Downs 1968, Hilton et al. 1999, H ilton in p ress). U nt il now, the oldest mammali an remains report ed from th e state were from the Paleocene Go ler For matio n of sout hern California (Mc Kenna 1960) . H ere, we report a metacarpal from th e Cam panian mar ine rocks of the Grea t Valley Group in Butte Co unty, Californ ia. T he specimen rep resents the first mammal reported from th e Mes ozoic of Californi a. Abbreviations: UCMP, University of Californ ia Museum of Paleontology, Berkeley, CA; SC , Sierra Co llege Museum

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