Here's what we have so far
Reptiles
Snakes
Western Yellow Belly Racer Coluber constrictor mormon
Sharp-tailed snake Contia tenuis (only 5 records)
California Kingsnake Lampropeltis getula californiae
Pacific Gopher Snake Pituophis catenifer catenifer
Aquatic Gartersnake Thamnophis atratus ssp. (only 1 record)
Giant Gartersnake Thamnophis gigas (only 5 records)
Valley Gartersnake Thamnophis sirtalis fitchi
Northern Pacific Rattlesnake Crotalus oreganus oreganus (only 2 records that appear to be the same individual)
Turtles
Western Pond Turtle Actinemys marmota
Red-eared Slider Trachemys scripta elegans
Lizards
California Whiptail Aspidoscelis tigris munda (only 2 records)
California Alligator Lizard Elgaria multicarinata multicarinata
Variegated Skink Plestiodon gilberti cancellosus (only 1 record)
Northern Brown Skink Plestiodon gilberti placerensis (only 2 records. Based on Californiaherps.com range maps these might be intergrades)
Western Skink Plestiodon skiltonianus skiltonianus (only 4 records)
Western Sagebrush Lizard Sceloporus graciousus gracilis (only 1 record)
Northwestern Fence Lizard Seloporus occidentalis occidentalis
Amphibians
Frogs
California Toad Anaxyrus boreas halophilus (only 2 records)
American Bullfrog Lithobates catesbeianus (only 5 records, 3 of which aren’t vouchered)
Sierran Treefrog Pseudacris sierrae (only 5 records)
Salamanders
California Slender Salamander Batrachoseps attentuatus (only 2 records)
And here are the species that are expected to, used to, or possibly occur in the county
Reptiles
Snakes
Saint Helena Mt. Kingsnake Lampropeltis zonata zonata- coast range on western edge of county. Should occur at higher elevations along the Napa County line
San Joaquin Coachwhip Coluber flagellum ruddocki- historic record in Colusa County near Yolo County line in foothills, though this population seems to be extinct
California Nightsnake Hypsinglena ochrorhyncha nuchalata- foothills and coast range on the western edge of the county
Long-nosed Snake Rinocheilus lecontei- historically occurred in foothills in the western part of the county
Lizards
Blainville's Horned Lizard Phyrnosoma blainvillii- unconfirmed historic record from Davis though very unlikely that even if this record is correct, this species is still present
Mediterranean Gecko Hemidactylus turcicus- records from Davis. A friend of mine has found multiple in her house, but I was never able to see one when I was there
Turtles
Possible introductions?
Amphibians
Frogs
California Red-Legged Frog Rana draytonii- historic record from nearby in northwestern Solano County and eastern Napa County but seems unlikely that they have held on anywhere in Yolo
Salamanders
California Giant Salamander Dicamptodon ensatus- Fish and Wildlife maps show them on the western edge of the county, but based on habitat and records, this is likely a mistake