Bob Palmatier





Diamondback Terrapins - The Seven Subspecies

As one surveys Diamondback Terrapins south along the Atlantic Coast starting at Cape Cod, Massachusetts, there begin to be subtle, then more pronounced differences in the morphology of the terrapins. In any population of diamondbacks, however, there is a great deal of variety in shell and skin color, and in the type of speckling on their skins. The latter variations are par for the course among terrapins, but the subspecies differences are more pronounced.



Diamondback Terrapin Range Map



The first two subspecies, starting on the Atlantic Coast at Cape Cod, Massachusetts, and continuing to northern Florida, are the Northern Diamondback Terrapin, and the Carolina Diamondback Terrapin. As you look at the subspecies descriptions found here or in other reference material, and compare them to terrapins found along that range, you may become perplexed. Why? The terrapin in your hand may often seem to be a mix of both descriptions. There’s a reason for that!



Mixing Things Up!

In the late 1800’s and early 1900's, Diamondback Terrapins were collected from various points along the Mid-Atlantic Coast as well as Texas and transported to seafood markets in the Northeastern states to supply affluent homes and restaurants when terrapin soup was a high priced gourmet dish.

Also during the early 1900's, terrapins from these same areas were transported to research stations funded by the US Bureau of Fisheries in NC and MD. The purpose of the research was to see if terrapins could effectively be farm-raised for food.


Concrete Terrapin pens still visible at Old Research Station, Beaufort, NC

Historical accounts and recent genetic studies indicate that uncertain numbers of the transported subspecies escaped or were randomly released into Atlantic coast terrapin populations.

Furthermore, when the Beaufort, NC research station was closed in 1948, nearly 250,000 hybrid terrapins were released into the salt marshes of Virginia, North and South Carolina, and Georgia.

It is not uncommon, then, to find individual terrapins in Mid-Atlantic coast populations north of Florida that have characteristics of the Texas subspecies. Northern Diamondback Terrapins are often found with characteristics of The Carolina Terrapin, and vice versa.

Furthermore, a small population of Diamondback Terrapins has been studied on the island of Bermuda. This population appears from genetic studies to have been colonized by means of the Gulf Stream by terrapins from the Carolinas at least as far back as the 1600's.



The Northern Diamondback Terrapin, (Malaclemys terrapin terrapin), ranges from Cape Cod to Cape Hatteras, NC. The medial keel is ridged but w/o knobs. The sides of the shell should be slightly wider at the back than at front. The color of shell is variable from one turtle to another, from black to light brown. The carapace will have distinct concentric rings. The color of the head, neck and legs is variable from white to gray with black dots or flecks. Plastron colors will range from orange to greenish gray.


Northern Diamondback male from
NC near Cape Hatteras




The Carolina Diamondback Terrapin, (Malaclemys terrapin centrata), ranges from Cape Hatteras to northern Florida. The medial keel is ridged but w/o knobs. The sides of the shell should be parallel. In any population of Carolina terrapins, the color of the carapace will be variable, from black to light brown. The backmost scales should be curled upward. The skin color of the head, neck, and legs will be white or gray with black spots and flecks. Plastron colors will range from orange to black.


Carolina Diamondback Female,
from Hyde County, NC



Carolina Diamondback male,
Brunswick County, NC

Carolina Diamondback female,
Brunswick County, NC



"Keels" and "Knobs"…What’s it all about?

A turtle’s back shell is called the "carapace." Its bottom shell is called the "plastron." The midline of the carapace, if raised slightly, is called a "keel." "Knobs" are the rounded "bumps" you can see on the hatchling and juvenile terrapins pictured below. The knobs become less pronounced in adult males, and eventually disappear almost entirely in adult females. Northern and Carolina terrapins have keels, but no knobs, even as hatchlings.


Juvenile Texas Terrapins
showing "knobs"

Ornate Terrapin hatchling
showing "knobs"



The Florida East Coast Diamondback Terrapin, (Malaclemys terrapin tequesta), ranges from northern Florida southward along the Atlantic coast to the Keys. The medial keel has knobs facing backwards. The scales of the carapace can be a bit lighter in their center surrounded by dark or tan. On the other hand, the carapace of the male tequesta in the first photograph is entirely black. The skin color of the head and legs will be white or gray with small black dots and flecks. The color of the plastron ranges from yellow to orange.


Tequesta male in photograph
has a large barnacle
attached to its carapace

Tequesta female from
Brevard County, Florida

Tequesta Female Plastron,
Brevard County, Florida

Tequesta hatchling from
Brevard County, Florida


The Mangrove Diamondback Terrapin, (Malaclemys terrapin rhizophorarum), is restricted to the Florida Keys. The medial keel has bulbous knobs. The scales of the dark carapace often have orange centers. The shell itself is strongly oblong. The skin color of the head and legs is medium gray with large black spots and short thickened black stripes (Northern Keys) or medium gray with small black dots (Southernmost Keys). The “pants” (rear area) can be striped with black. The color of the plastron is yellow to orange with brown markings. Research indicates the two populations may deserve subspecies status.



Northern Keys


Mangrove Terrapin female

Mangrove female profile

Mangrove female road mortality

Same mangrove female road mortality



Southern Keys


Mangrove Terrapin female

Mangrove female profile

Mangrove Terrapins carapace and plastron

Staying warm in mud during winter months



The Ornate Diamondback Terrapin, (Malaclemys terrapin macrospilota), ranges from Florida Bay north along Florida’s Gulf Coast and west along the Florida Panhandle. The medial keel often has bulbous knobs. The scales of the dark carapace have orange or yellow centers. Carapaces of some individuals can be entirely black. The skin color of the head and legs is most often white to light gray with black spots. When white a pinkish tinge shows through. The color of the plastron ranges from yellow to orange.


Male and female Ornate Diamondbacks,
Citrus County, Florida

Female Ornate Diamondback,
Citrus County, Florida

Ornate Diamondback Hatchling.

Ornate female, dark phase male



The Mississippi Diamondback Terrapin, (Malaclemys terrapin pileata), ranges from the Florida Panhandle to western Louisiana. The medial keel has terminal knobs. The scales of the carapace are uniformly dark, often with deep concentric grooves. The shell viewed from above has an oval shape to it. The skin color of the head, neck, and the legs varies from gray to dark brown with small black dots. The color of the plastron ranges from yellow to orange with brown markings.


Mississippi Diamondback male

Mississippi Female Profile

Mississippi Diamondback, Plastron

Mississippi Diamondback, male

Mississippi Diamondback female



The Texas Diamondback Terrapin, (Malaclemys terrapin littoralis), ranges from western Louisiana to Corpus Christi, Texas. The medial keel has terminal knobs. The carapace is dark brown to black, often with concentric grooving. The skin color of the head is white to medium gray with small to medium black spots. Skin coloring on legs ranges from gray with dark spots to entirely black. Texas terrapins can be quite a bit larger than other subspecies. This explains their export to NE markets and to the Beaufort, NC research lab in the early 1900’s.


Texas Diamondback Female,
Galveston Bay,Texas

Juvenile Texas Terrapins,
Galveston Bay study area

Texas Diamondback Female Carapace,
Galveston Bay, Texas



Photo Credits:

Diamondback Terrapin Range Map: adapted from Archie Carr's Handbook of Turtles with permission of Cornell University Press.

Mixing Things Up!: photos of Beaufort, NC , terrapin pens, the author.

Northern Diamondback Terrapin & Carolina Diamondback Terrapins: photos by the author.

Keels and Knobs:
Juvenile Texas terrapins: courtesy of George Guillen, University of Houston, Clear Lake, Texas.
Hatchling Ornate Terrapin: courtesy of Christopher Scott Boykin, Florida Department of Environmental Protection.

Florida East Coast Diamondback Terrapins:
Tequesta male with barnacle: courtesy of Christopher Gillette.
Tequesta, other photos: courtesy of Edward Perry, Sebastian Inlet State Park, Vero Beach, Florida.


Mangrove Diamondback Terrapins:
   Northern Keys:
Mangrove Terrapin in hand, profile: courtesy of Christopher Gillete.
Mangrove road mortality shots: courtesy of Christopher Scott Boykin, Florida Department of Environmental Protection.

   Southern Keys:
Mangrove Terrapin in hand, carapace and plastron, in mud: courtesy of Christopher Scott Boykin, Florida Department of Environmental Protection.
Mangrove terrapin profile: courtesy of Dan McLaughlin, Wetlands Institute, Stone Harbor, New Jersey.

Ornate Diamondback Terrapins:
Male and female, Crystal River ; Ornate hatchling: courtesy of Christopher Scott Boykin, Florida Department of Environmental Protection.

Female Ornate with Yellow Markings, Ornate Female w/dark phase male, Crystal River: courtesy of Edward Perry, Sebastian Inlet State Park, Vero Beach, Florida.

Mississippi Diamondback Terrapins:
Mississippi Diamondbacks: courtesy of Christina Mohrman, Grand Bay National Estuarine Research Reserve, Moss Point, Mississippi.

Texas Diamondback Terrapins:
Texas Diamondback female and juveniles: courtesy of George Guillen, University of Houston-Clear Lake, Houston,Texas.

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© Bob Palmatier. Please do not use or reproduce without written permission.