Turtles are a broad group of reptiles that includes over 350 species. Biologists group turtles by their environment: freshwater turtles, sea turtles, and land-dwelling tortoises.
Turtles have existed since the Middle Jurassic period. They’ve been around longer than snakes and even crocodilians!
Turtles live in almost every U.S. state. Sometimes, sea turtles even visit chilly Alaska!
Today, you’ve come to the right place to learn how to identify the United States’ fascinating testudines.
In This Article
In-Short
- There are over 350 species of turtle in the world.
- The United States is home to at least 56 turtle species.
- Biologists categorize turtles as sea turtles, tortoises, or freshwater turtles.
- You can identify turtles by their size, foot shape, shell shape, pattern, and color.
- Even more exotic turtle species can be found in pet stores or running loose as released pets!
Vocabulary
- Scute – A scute is a bony plate on a turtle’s shell. Most turtles’ shells are divided into visible sections. Each segment is a scute.
- Marginal Scute – The scutes on the edge of the carapace. Count these scutes in pairs.
- Vertebral Scute – The scutes on the top of the carapace. There is only one row of vertebral scutes.
- Pleural Scute – The scutes between the vertebral scutes and the marginal scutes. Count these scutes in pairs.
- Nuchal Scute – The scute directly behind the turtle’s head
- Carapace – The upper (top) shell of a turtle.
- Plastron – The lower (bottom) shell of a turtle.
- Osteoderm – A protruding bony plate in the skin.
- Keel – A raised ridge down the center of the shell or scute.
- Chelonian or Testudine – Any animal in the scientific order Testudines, including turtles, tortoises, and terrapins.
- Hinged – Attached or joined with a movable mechanism. Turtles with hinged shells can partially or entirely seal their carapace and plastron together. They hide their fleshy body parts inside.
Quick Turtle Identification Guide
Quickly identifying a turtle allows you to determine your next steps if you are rescuing, relocating, or taking care of it.
Turtles and tortoises are related organisms that have vastly different needs (opens in new tab). Luckily, it’s easy to determine whether the testudine is a freshwater turtle, sea turtle, or tortoise. It takes a trained eye to differentiate similar species.
Once you know what type of turtle it is, you have much of the information you need to help it to safety or provide appropriate accommodations.
Freshwater Aquatic Turtles
Most North American turtles are considered freshwater aquatic turtles. This group includes many prevalent species, such as:
- Cooters
- Painted turtles
- Snapping turtles
- Red-eared sliders
- And many more!
Most freshwater turtles have feet with toes and claws. Sometimes, their toes are webbed to help them swim.
Fun Fact: Despite their webbed feet and aquatic habits, freshwater turtles aren’t considered amphibians.
Sea Turtles
Five species of sea turtles live along the coastal United States. They are:
- Green sea turtle
- Hawksbill sea turtle
- Loggerhead sea turtle
- Leatherback sea turtle
- Kemp’s ridley sea turtle
Sea turtles don’t have feet. Their flippers are a dead giveaway!. Sea turtles typically only come onto land to lay their eggs. Sea turtles may also be spotted while scuba diving or floating and bobbing at the ocean’s surface.
Tortoises
The United States is home to only four true tortoises:
- Desert tortoise
- Gopher tortoise
- Berlandier’s tortoise
- Morafka’s desert tortoise
Tortoises are land-dwelling herbivores. They enjoy munching on grass, leaves, and the occasional fruit. Tortoises are adapted to living on land. Most tortoises can’t swim.
The United States is also home to another terrestrial testudine: the box turtle. Box turtles share many physical characteristics with tortoises. These adaptations help them both thrive outside of the water. Despite their similarities, box turtles are genetically more closely related to aquatic freshwater turtles than tortoises.
For our identification guide, we include box turtles with tortoises. North America’s box turtle species are:
- Ornate box turtle
- Common box turtle
Check out Those Feet!
The easiest way to differentiate the three turtle types is to look at their feet!
Webbed Feet = Freshwater Turtle
If your turtle has fleshy, webbed feet with sharp claws, it’s likely a freshwater aquatic turtle. Proceed to “Identifying a Freshwater Aquatic Turtle” if you’d like to learn more about the specific species.
Flippers = Sea Turtle
Turtles with blunt, toeless flippers are sea turtles. Some sea turtles have claws on their flippers! Scroll down to “Identifying a Sea Turtle” if you’d like to determine which species it is.
Stumpy Feet = Tortoise or Box Turtle
Turtles with rough, stumpy, elephant-like feet are likely either a type of tortoise or box turtle. Tortoises have blunt nails, and box turtles have sharp claws. Continue to “Identifying a Tortoise” if you’d like to learn more.
Baby Turtle Identification
Baby turtles are harder to identify down to species level. You can’t use their size to identify them. Unfortunately, adult size is a crucial component for nailing down some turtle species. Some turtles are so small as adults that they can be mistaken for a baby!
Most baby turtles look like miniature versions of their adult relatives. Freshly-hatched baby turtles may have a sharp tooth, known as an egg tooth, on their nose. The egg tooth falls off by the time the hatchling is six weeks old.
Frequently, baby turtles will have brighter colors and patterns than adults. They also tend to have less scarring.
How to Identify a Turtle by its Shell
Did you know that a turtle wouldn’t survive without its shell?! A turtle’s shell is imperative for its survival and identification.
Aquatic turtles tend to have streamlined, flattened shells that help them expend less energy while swimming. This feature applies to both freshwater turtles and sea turtles.
Tortoises and box turtles have dome-shaped shells. Most tortoises have fixed shells that don’t move or close. Box turtles have hinged shells that they can hide inside.
The biologists at DiscoverLife.org have developed a handy visual quiz for identifying turtle species. This quiz is based mainly on shell characteristics.
Identifying a Freshwater Aquatic Turtle Species
Nailing down the species of a freshwater aquatic turtle is the most challenging. There are SO many potential prospects! Luckily, some types of turtles have unique identifying features.
Step One: Is the Carapace Hard?
Yes
Continue to step two.
No, It’s Soft With No Scutes
Softshell turtles are the only North American turtle species that lack scutes and have soft, leathery shells. There are three types of softshell turtles:
- Florida softshell turtle (Apalone ferox)
- Spiny softshell turtle (Apalone spinifera)
- Smooth softshell turtle (Apalone mutica)
Florida softshells prefer slow-moving or still water habitats. It has a dark-colored shell and an off-white underside. Florida softshells are the largest softshell species, reaching up to 30 inches long and 100 pounds. They only occur in the following states:
- Florida
- Georgia
- Alabama
- South Carolina
Smooth softshells are distinguishable by their plain white chin, circular nostrils, and lack of spiny protrusions along their carapace’s front edge. They’re native to most of the central and southcentral United States.
You can quickly identify spiny softshells by the row of spiny projections from the front edge of their carapace. They’re also native to most of the central United States.
Step Two: Does the Plastron Almost or Completely Cover the Turtle’s Body?
Yes
Continue to step three.
No, It’s Small and Strongly Cross-Shaped
Snapping turtles have unique T-shaped or cross-shaped plastrons. Their plastron is small and doesn’t cover the turtle’s entire underside. There are two snapping turtle species in the United States:
- Common snapping turtle (Chelydra serpentina)
- Alligator snapping turtle (Macrochelys temminckii)
Alligator snapping turtles have three distinct rows of bony, raised plates called osteoderms. Osteoderms give the alligator snapper its prehistoric appearance. They live in the southeastern United States.
Common snapping turtles have smooth carapaces with no spikes or raised plates. They’re native to most of the country, excluding the western-most states.
Step Three: Are There Lengthwise Ridges on the Carapace?
No
Continue to step four.
Yes, There Are One to Three Keels
Most North American freshwater turtles have a smooth carapace. Besides alligator snapping turtles, map turtles and musk turtles also have keeled shells.
Map turtles have one dorsal keel that runs down the middle of their shell. The keel sometimes forms spines. Map turtles are also known as sawback turtles because of the saw-like appearance of the spines. There are 14 species of map turtle in the United States:
- Texas map turtle (Graptemys versa)
- Cagle’s map turtle (Graptemys caglei)
- Escambia map turtle (Graptemys ernsti)
- Ringed map turtle (Graptemys oculifera)
- Alabama map turtle (Graptemys pulchra)
- Barbour’s map turtle (Graptemys barbouri)
- Sabine map turtle (Graptemys sabinensis)
- Pearl River map turtle (Graptemys pearlensis)
- Pascagoula map turtle (Graptemys gibbonsi)
- Common map turtle (Graptemys geographica)
- Ouachita map turtle (Graptemys ouachitensis)
- Black-knobbed map turtle (Graptemys nigrinoda)
- False map turtle (Graptemys pseudogeographica)
- Yellow-blotched map turtle (Graptemys flavimaculata)
Musk turtles look similar to map turtles, but they tend to have a more dome-shaped carapace. Musk turtles also have one dorsal keel running centrally down their carapace. North American musk turtle species include:
- Loggerhead musk turtle (Sternotherus minor)
- Common musk turtle (Sternotherus odoratus)
- Stripeneck musk turtle (Sternotherus peltifer)
- Razorback musk turtle (Sternotherus carinatus)
- Flattened musk turtle (Sternotherus depressus)
- Intermediate musk turtle (Sternotherus intermedius)
Step Four: Is the Carapace Spotted?
No
Continue to step five.
Yes
The spotted turtle (Clemmys guttata) is the only North American freshwater turtle with easily identifiable yellow spots on its dark skin and shell.
Spotted turtles typically grow to a mere one to four inches long. They prefer habitats with shallow, slow-moving water, muddy bottoms, and aquatic vegetation.
Step Five: Do the Scutes Have Ridged Rings?
No
Continue to step six.
Yes
Wood turtles (Glyptemys insculpta) and bog turtles (Glyptemys muhlenbergii) are two related turtle species with circular ridges on their scutes.
Wood turtles live in the northeastern United States. These semi-aquatic turtles grow to be 5 to 8 inches long. Their carapace is brown, gray, or tan. Their neck, chin, and inner legs tend to be pale yellow to bright orange.
Bog turtles are similar in size and appearance. They also have bright spots on each side of their neck.
The Diamondback terrapin also has circular ridges on each scute. They frequent brackish, coastal waters. It’s hard to miss-identify a diamondback terrapin. They have striking silvery-gray skin with black, wiggly markings.
Step Six: Further Identification
If you were unable to identify your turtle using the steps above, it likely falls into one of these groups:
Chicken Turtles (Deirochelys reticularia)
Size: <10”
Color: Olive green or dark brown carapace.
Pattern: Yellow stripes on the skin.
Scute Count: 37 Total: Marginals (12/12); Pleurals (4/4); Vertebrals (5)
Range: Most of the southeastern United States.
Painted Turtles (Chrysemys picta)
Size: <10”
Color: Olive green, brown, or black carapace.
Pattern: Red and yellow stripes on the skin.
Scute Count: 37 Total: Marginals (12/12); Pleurals (4/4); Vertebrals (5)
Range: All U.S. states except Nevada, California, Hawaii, Alaska, and Florida.
Cooters and Sliders (genus Pseudemys and Trachemys)
Cooters and sliders are the most prevalent turtles in the United States. They’re difficult to tell apart – even for biologists! To complicate matters, some of them hybridize in overlapping territories.
The easiest way to tell adult cooters and sliders apart from other aquatic turtles is their size. They’re the only North American pond turtles that can reach shell lengths over 12”.
Mud Turtles (genus Kinosternon)
There are several species of mud turtles in the United States. They all vary widely in size and appearance. The easiest way to differentiate mud turtles from other freshwater aquatic turtles is by counting their scutes:
Scute Count: 36 Total: Marginals (11/11); Pleurals (4/4); Vertebrals (5); Cervical(1)
Identifying a Sea Turtle
Sea turtles are far easier to identify at a species level. There are only a handful of sea turtle species living around America’s coasts.
Step One: Are There Scutes on the Carapace?
Yes
Continue to step two.
No
The leatherback sea turtle (Dermochelys coriacea) is the only species that doesn’t have scutes on its carapace.
Leatherbacks are dark gray. They have thick, leathery skin embedded with seven rows of osteoderms. Leatherbacks are the BIGGEST sea turtle, weighing up to 1,540 pounds!
Step Two: Is the First Top Scute Triangular?
No
Continue to step three.
Yes
If the first top scute, closest to the turtle’s head, is triangular, it is one of these species. To differentiate them, look at the turtle’s head from above.
Two Pairs of Scales in Front of Eyes
If there are two pairs of scales between the eyes and the nose, it is likely a hawksbill sea turtle (Eretmochelys imbricata). As its name suggests, hawksbill sea turtles have a sharply pronounced beak (mouth).
One Pair of Scales in Front of Eyes
If there’s only one pair of scales between the eyes and the nose, it’s likely a green sea turtle (Chelonia mydas). Unlike its close relative, green sea turtles don’t have hooked beaks.
Step Three: Further Identification
If none of the above features apply, then you’re looking at a loggerhead or Kemp’s ridley sea turtle. If you’re still having a hard time, try this sea turtle identification key from the National Oceanic and Atmospheric Administration biologists.
Loggerhead Sea Turtle
The loggerhead sea turtle (Caretta caretta) is the world’s LARGEST hard-shelled turtle. They weigh up to 1,202 pounds! Loggerheads have a keeled, dark brown carapace. Males have longer tails and claws than females.
Kemp’s Ridley Sea Turtle
The Kemp’s ridley sea turtle (Lepidochelys kempii) is the rarest and most endangered sea turtle. If you see one in the wild, consider it your lucky day! It’s also the smallest species, weighing in at a maximum of 110 pounds. Their skin and shell are grey-green.
Identifying a Tortoise
Finally, we’ve reached the land-dwelling turtles and tortoises. Most of these species don’t have any remarkably unique features. Instead, we’ll break them down by geographic range and overall appearance.
Tortoises
Agassiz’s Desert Tortoise (Gopherus agassizii)
Size: <15”
Color: Dark brown or gray.
Pattern: Little to none.
Scute Count: 35 Total: Marginals (11/11); Pleurals (4/4); Vertebrals (5)
Range: Mojave and Sonoran deserts of the southwestern United States. West of the Colorado River.
Gopher Tortoise (Gopherus polyphemus)
Size: <16”
Color: Brown, gray, or black
Pattern: Little to none
Scute Count: 36 Total: Marginals (11/11); Pleurals (4/4); Vertebrals (5); Cervical (1)
Range: Southeastern United States
Morafka’s Desert Tortoise (Gopherus morafkai)
Size: <15”
Color: Dark brown or gray.
Pattern: Little to none.
Scute Count: 35 Total: Marginals (11/11); Pleurals (4/4); Vertebrals (5)
Range: Mojave and Sonoran deserts of the southwestern United States. East of the Colorado River.
Texas Tortoise (Gopherus berlandieri)
Size: ~8.5”
Color: Gray or dark brown, fading to yellow in the center of each scute.
Pattern: Little to none.
Range: South-central Texas.
Box Turtles
Common Box Turtle (Terrapene carolina)
Size: <7”
Color: Brown carapace with orange and yellow markings. Red or yellow irises.
Pattern: Lines, bars, spots, and blotches.
Scute Count: 37 Total: Marginals (12/12); Pleurals (4/4); Vertebrals (5) (variable)
Range: Eastern United States
Ornate Box Turtle (Terrapene ornata)
Size: <7”
Color: Black or dark brown carapace with yellow markings.
Pattern: Lines, bars, spots, and blotches.
Scute Count: 37 Total: Marginals (12/12); Pleurals (4/4); Vertebrals (5) (variable)
Range: Central United States
Bonus Round: Identifying Exotic Pet Store Turtles
If your turtle looks nothing like any of the species we’ve discussed, it’s possibly an escaped pet. Here are some common pet store turtles that aren’t native to the U.S.A.
African Sideneck Turtle (family Pelomedusidae)
Sideneck turtles carry their name for their inability to withdraw their head into their shell. Instead, they fold their neck to the side and hide their head under the edge of their shell. Their upwards-turned mouth gives the impression that they’re perpetually smiling.
African sideneck turtles have smooth shells. They grow up to 17 inches in length. They’re a rather plain-looking, unpatterned turtle. Their undersides are off-white with a dark brown coloration up top. As their name suggests, African sideneck turtles are native to Africa.
Mata Mata Turtle (Chelus fimbriata)
Mata mata turtles are genuinely unique in their appearance. Their entire physical appearance evolved to blend in with dead leaves. A mata mata’s triangular head and wrinkly limbs have fleshy protrusions. They suggest the appearance of torn and tattered dead plant matter.
Mata matas are usually dark brown. Their neck and inner legs are sometimes bright pink, especially on younger specimens. Adult mata matas reach up to 18 inches long and weigh around 33 pounds. This species is native to South America.
Pancake Tortoise (Malacochersus tornieri)
Unlike most dome-shelled tortoises, pancake tortoises carry their name after their flattened shells. Their body shape helps them move quickly and squeeze into rocky crevices.
A pancake tortoise’s carapace is brown with radiating dark lines on each scute. They’re one of the reasonably sized tortoise species. Pancake tortoises usually stay under 7 inches long. Their body is perfectly adapted to living life in the scrub savannas of Africa.
Red-footed Tortoise (Chelonoidis carbonarius)
The red-footed tortoise is, arguably, the most prevalent pet tortoise. These tortoises grow up to 16 inches long.
Red-footed tortoises are reasonably easy to identify. They have a unique, bread loaf-shaped carapace. The middle of each scute has a patch of yellow.
Indian Star Tortoise
The Indian star tortoise is so prevalent in the pet trade that its wild populations are threatened. They usually grow around 10 inches long. Males are shorter than females.
They have pyramid-shaped keels on each scute. Indian star tortoises’ name follows the unique, star-shaped streaks on each of the keels. Their pattern helps them blend into the vegetation of Central and South America.
Additional Turtle and Tortoise Resources and Education
If you’d like to learn more about the turtles you might find in a pet store, check out this comprehensive guide for the BEST pet turtles. While you’re at it, here’s another guide for pet tortoises you might find in stores (or escaped)!
If you want to learn more about the native turtles we discussed today, check out the iNaturalist organization’s turtle guide. They offer helpful information about conserving our endemic species.
