United States of America

Mammals living nowhere else include the Red Wolf (ARKive WM), the Island Fox (iNaturalist), the Seminole Bat (Ky.gov), the Indiana Myotis (iNaturalist), the New England Cottontail (NE Cottontail), the Olympic Marmot (iNaturalist), the Utah Prairie Dog (iNaturalist), Nelson’s Antelope Squirrel (iNaturalist), the Hopi Chipmunk (ASM WM), and the Giant Kangaroo Rat (ARKive WM). Endemic genera include the Hawaiian Monk Seal (NOAA), the Pygmy Rabbit (mt.gov), the Pallid Kangaroo Mouse (ARKive WM), the Round-tailed Muskrat (flickr), the Red Tree Vole (ARKive WM), the Florida Deer Mouse (flickr), and the Golden Mouse (ARKive WM).

Birds unique to the United States include the Gunnison Grouse (eBird), the Greater Prairie-chicken (eBird), the Red-cockaded Woodpecker (eBird), the Florida Scrub-jay (eBird), the Carolina Chickadee (eBird), the Brown-headed Nuthatch (eBird), the Boat-tailed Grackle (eBird), the Hawaiian Goose (eBird), and the Hawaiian Hawk (eBird). Breeding endemics include the Black Turnstone (eBird), the Hawaiian Petrel (eBird), Swainson's Warbler (Neotropical Birds WM), Allen's Hummingbird (eBird), McKay's Bunting (eBird), and the Mississippi Kite (eBird).

Hawaii is exceptionally rich in endemic genera of birds including the Palila (eBird), the Oahu Amakihi (eBird), the Akikiki (eBird), the Iiwi (ABC), the Hawaii Akepa (eBird), the Maui Alauahio (Maui Forest Birds), the Akohekohe (eBird), the Elepaio (eBird), and the Nihoa Finch (eBird). The Kauai Oo (birdfinding.info) (eBird), which became extinct about 1987, was the last surviving member of an endemic family, the Mohoidae.

Reptiles restricted to the United States include the American Alligator (iNaturalist), the Flattened Musk Turtle (TFTSG), the Gopher Tortoise (iNaturalist), the Panamint Alligator Lizard (CA Herps), the Blunt-nosed Leopard Lizard (CA Herps), the unisexual Plateau Striped Whiptail (CA Herps), the Island Night Lizard (nps.gov), the Florida Sand Skink (iNaturalist), the Southern Rubber Boa (CA Herps), the Eastern Coral Snake (SREL), the Pygmy Rattlesnake (SREL), and the Eastern Diamondback Rattlesnake (FLMNH). Endemic genera include the Alligator Snapping Turtle (ARKive WM), the Chicken Turtle (SREL), the Rainbow Snake (SREL), and the Scarlet Snake (SREL WM). The Florida Worm Lizard (Wormlizard.org WM) (iNaturalist) is the sole member of the family Rhineuridae.

Amphibians exclusive to the U.S. include the Black Warrior Waterdog (Outdoor Alabama), the Houston Toad (TPWD), the Southern Cricket Frog (SREL), the Southern Mountain Yellow-legged Frog (CA Herps), and the Eastern Spadefoot (iNaturalist). Endemic genera include the Hellbender (SREL), the Southern Dwarf Siren (AmphibiaWeb), the Georgia Blind Salamander (SREL), the Red Salamander (SREL), the Red Hills Salamander (Forever Wild), and the Idaho Giant Salamander (mt.gov). The torrent salamanders (iNaturalist) and the amphiumas (iNaturalist) represent endemic amphibian families.

An impressve endemic freshwater fish fauna includes the Apache Trout (CBD), the Guadalupe Bass (Texas State Univ. WM), the Shortnose Gar (MDC), the Shovelnose Sturgeon (FishBase), the Redband Darter (Conservation Fisheries), the Devil’s Hole Pupfish (IUCN), the Colorado Pikeminnow (Joel Sartore), the Piebald Madtom (Conservation Fisheries), the Pahrump Poolfish (GWG), the Delta Smelt (IUCN), and the Southern Brook Lamprey (FishBase). Representing endemic families are the cavefish (iNaturalist), the Pirate Perch (NANFA), and the pygmy sunfishes (iNaturalist). The American Paddlefish (ARKive WM) also likely represents an endemic family as the Chinese Paddlefish is almost certainly extinct.

Hawaii is especially rich in endemic marine fish including Potter’s Angelfish (Keoki & Yuko Stender), the Orangemargin Butterflyfish (ZooKeys), the Psychedelic Wrasse (Keoki & Yuko Stender), the Hawaiian Turkeyfish (iNaturalist), Randall's Puffer (FishBase), the Fantail Tilefish (iNaturalist), the Goldring Surgeonfish (Keoki & Yuko Stender), the Yellowbar Parrotfish (IUCN), the Hawaiian Longfin Anthias (iNaturalist), the Hawaiian Grouper (Keoki & Yuko Stender), Fisher's Seahorse (ResearchGate), and the Hawaiian Garden Eel (Keoki & Yuko Stender).

Mainland endemic marine fish include the Sixspot Prickleback (metridium.com WM), the Bull Sculpin (BAUE WM), the Seaboard Goby (gobiidae.com WM), the Swallowtail Basslet (IUCN), the Gulf Batfish (STRI WM), the Striped Blenny (FishBase), the Northern Stargazer (STRI WM), the Florida Hamlet (STRI WM), the Florida Blenny (STRI WM), the Oyster Toadfish (STRI WM), and the Butterfly Skate (Wikipedia).

Butterflies limited to the United States include the Diana Fritillary (iNaturalist), the Kamehameha Butterfly (iNaturalist), the Zebra Swallowtail (Univ. Florida), Bauer's Blue (iNaturalist), the California Dogface (iNaturalist), the Chisos Metalmark (iNaturalist), and the Poweshiek Skipperling (iNaturalist). Endemic moths include the Mendocino Silk Moth (iNaturalist), the Kern Primrose Sphinx Moth (MPG), a Hawaiian species with a carnivorous caterpillar Eupithecia orichloris (iNaturalist), and the Oso Flaco Flightless Moth (iNaturalist).

Other endemic insects include the Pacific Clubtail (Creagrus WM), the San Francisco Forktail (IUCN), the Mysterious Lantern Firefly (IUCN), the Coral Pink Sand Dunes Tiger Beetle (iNaturalist), the Delta Green Ground Beetle (iNaturalist), the Eastern Hercules Beetle (BugGuide), Franklin's Bumblebee (IUCN), the Hairy-headed Acrobat Ant (iNaturalist), the Michigan Bog Grasshopper (iNaturalist), the Santa Monica Shieldback (iNaturalist), Riley's 13-Year Cicada (iNaturalist), a Hawaiian leafhopper Dictyophorodelphax mirabilis (iNaturalist), and over 500 species of Hawaiian fruit flies (flickr).

A rich endemic cave fauna includes the Texas Cave Shrimp (ARKive WM), the Woodville Karst Cave Crayfish (iNaturalist), the Madison Cave Isopod (iNaturalist), a springtail Pseudosinella hirsuta (iNaturalist), the Kaumana Cave Cricket (iNaturalist), the Idaho Ice Cave Beetle (Wikipedia), the Kretschmarr Cave Mold Beetle and the Bone Cave Harvestman (both at austintex.gov), Barr's Cave Spider (fig. 2B at ResearchGate), a pseudoscorpion Parobisium yosemite (BHL), a millipede Scoterpes copei (fig. 2a at MDPI), the Manitou Cavesnail (iNaturalist), the Glass Coil Snail (figs. 7-9 at BHL), and a planarian Macrocotyla glandulosa (p. 20 of MSS pdf).

Other endemic invertebrates include the Happy Face Spider (HBS WM), the Santa Catalina Mountain Tarantula (iNaturalist), Workman's Jumping Spider (BugGuide), the Southern Unstriped Scorpion (BugGuide), a harvestman Ortholasma colossus (iNaturalist), a solifuge Hemerotrecha vetteri (iNaturalist), the Socorro Isopod (iNaturalist), the Mono Lake Brine Shrimp (iNaturalist), the Oregon Giant Earthworm (iNaturalist), the Oahu Tree Snail (ARKive WM), the Black Hills Mountainsnail (Xerces Soc.), the California Banana Slug (iNaturalist), and a freshwater sponge Ephydatia cooperensis (mt.gov). The U.S. is first in the world in endemic species of several freshwater groups: stoneflies (Xerces Soc.), mayflies (Discover Life), caddisflies (mt.gov), crayfish (MDC), mussels (MN DNR), and freshwater snails (IUCN).

Endemic Hawaiian marine invertebrates include a coral Porites pukoensis (EDGE), the Banded Ribbon Worm (Keoki & Yuko Stender), the Painted Hermit Crab (iNaturalist), the Banded Spiny Lobster (IUCN), the Hawaiian Hinge-beak Shrimp (Keoki & Yuko Stender), a nudibranch Hypselodoris paulinae (Sea Slugs of Hawaii WM), the Bristled Chiton (Keoki & Yuko Stender), the Hawaiian Limpet (Keoki & Yuko Stender), and a cone snail Conus leviteni (Keoki & Yuko Stender).

Representatives of endemic invertebrate families include a false stag beetle Diphyllostoma (CalPhotos), a true bug Curalium (NAL WM pdf), the Relict Silverfish Tricholepidion (BugGuide), the scale insects Pityococcus (BugGuide), the spiders Trogloraptor (Wikipedia) and Megahexura (iNaturalist), a harvestman Cryptomaster (ZooKeys), the mites Elliptochthonius (GBIF) and Crotalomorpha (p. 4 of Valparaiso Univ. pdf), the hairy water flea Dumontia (Univ. Wisconsin), Hubricht's Long-tailed Amphipod (p. 23 of MSS pdf), the amphipods Parabogidiellidae (iNaturalist), a land snail Amastra (ARKive WM), the earthworms Lutodrilus (BHL) and Komarekiona (IUCN), a rotifer Coronistomus (GBIF), an arrow worm Bathybelos (p. 2 of Ingenta pdf), a siphonophore Tottonophyes (GBIF), a flatworm Crassicollum (WoRMS), and a plethora of millipedes including Floridobolus (Joel Sartore), Choctella (iNaturalist), Apterous (iNaturalist), Chelojulus (CalPhotos), Branneria (iNaturalist), Urochordeuma (iNaturalist), and the Paeromopodidae (iNaturalist).

Endemic carnivorous plants include the Venus Flytrap (ARKive WM), the Cobra Plant (Carnivorous Plants WM), Tracy's Sundew (iNaturalist), the Yellow Butterwort (iNaturalist), and the Swollen Bladderwort (iNaturalist). Other endemic vascular plants include the Golden Glade Cress (iNaturalist), the Flame Azalea (iNaturalist), the Florida Blazing Star (iNaturalist), the Aztec Gilia (NM Rare Plants), the Pallid Manzanita (CBD), the Canelo Hills Ladies’ Tresses (CBD), the Winkler Pincushion Cactus (Llifle), the Tonto Basin Agave (iNaturalist), the Joshua Tree (Jepson), the Giant Blue Iris (iNaturalist), the Carolina Lily (iNaturalist), the Tennessee Purple Coneflower (iNaturalist), the Sego Lily (iNaturalist), the Wyoming Paintbrush (iNaturalist), and the Blue Columbine (iNaturalist).

Trees found only in the mainland U.S. include the Giant Sequoia (iNaturalist), the Coast Redwood (GTC WM), the Great Basin Bristlecone Pine (iNaturalist), the Baldcypress (Gymnosperm Database), the Fraser Fir (GTC WM), the Florida Torreya (iNaturalist), the Chalk Maple (iNaturalist), the Red Buckeye (MBG), the Virginia Roundleaf Birch (iNaturalist), the Pyramid Magnolia (wildflower.org), the Florida Willow (GPT WM), the Water Tupelo (iNaturalist), the Golden Chinquapin (iNaturalist), the Tanoak (OSU), the Sourwood (iNaturalist), the Island Ironwood (USDA pdf), the Fevertree (In Defense of Plants), the Franklin Tree (Harvard), the American Persimmon (iNaturalist), the Winged Elm (iNaturalist), the Water Elm (iNaturalist), and the Georgia Oak (GTC WM). Corkwood (iNaturalist) is sometimes placed in an endemic family, the Leitneriaceae.

Endemic Hawaiian vascular plants include the Hawaiian Silversword (iNaturalist), the Olulu (iNaturalist), the Oha Wai (UH Botany WM), the 'Ohi'a Lehua (hawaii.gov), the Aku (CalPhotos), the Honohono (UH Botany WM), Hesperomannia (UH Botany WM), the Hau Kuahiwi (iNaturalist), Hillebrandia (iNaturalist), Kokia (UH Botany WM), Nototrichium (UH Botany WM), Schiedia (iNaturalist), the Koli'i (iNaturalist), the Koki‘o Ke‘oke‘o (iNaturalist), the Hawaiian Caper (iNaturalist), and Dubautia (iNaturalist).

Endemic fungi include Leptonia carnea (IUCN WM), Hygrocybe lamalama (IUCN WM), and Morchella kaibensis (Mushroom Observer WM). Endemic fungal families include Protogastraceae (BHL), Atractogloeaceae (Cybertruffle WM), and Gasterellaceae (GBIF). Endemic lichens include Peltigera aquatica (IUCN WM) and Hypotrachyna virginica (IUCN WM). Endemic non-vascular plants include the liverworts Cheilolejeunea evansii (UNA) and Drepanolejeunea appalachiana (USFS WM), a hornwort Paraphymatoceros proskaueri (iNaturalist), and the mosses Fissidens appalachensis (UNA) and Leptohymenium sharpii (UNA). Kahakuloaceae (BDE) is an endemic Hawaiian family of liverworts. Endemic seaweeds include Gracilaria coronopifolia (Univ. Hawaii) and Sargassum polyphyllum (Univ. Hawaii). Blinksiaceae (macroalgae.org) (Google Books) is an endemic red algae family.

A number of microorganisms are known only from hot springs in Yellowstone National Park (MDPI pdf) (NPS History WM pdf).

The U.S. includes parts of four biodiversity hotspots: the Madrean Pine-Oak Woodlands (Biodiversity Hotspots WM), the Polynesia-Micronesia (Biodiversity Hotspots WM), the North American Coastal Plain (CEPF), and the California Floristic Region (Biodiversity Hotspots WM). Other important areas for endemic species include the Appalachian Mixed Mesophytic Forests (EoE), the freshwaters of the southeastern U.S. (southeastfreshwater.org pdf), and the Hawaiian Marine (Google Books).

See also American Samoa, Baker Island, Guam, Howland Island, Johnston Atoll, Midway Islands, Navassa Island, Northern Mariana Islands, Puerto Rico, United States Virgin Islands, and Wake Island.