Northern
Malaclemys terrapin terrapin (common name is Northern diamondback terrapin). Northerns can be found from Cape Cod, Massachusetts to Cape Hatteras, North Carolina.
Northerns have the most varied color patterns of all the subspecies. It can be impossible to positively identify some of them just by looking at them. Some people believe the reason for such a wide range in their patterns is because a large number of diamondback terrapin farms in the twenties dumped their stock into native waters (Between New York and Virginia) when the demand for turtle soup dropped during World War I. Many of the diamondback terrapins in these farms were caught down south and when they were released they started cross-breeding with the native Northerns.
With so much variation within this subspecies it is hard to say what a “normal” Northern looks like. First we will start by describing a dark phased Northern. They have completely black carapaces, with yellow to off-white plastrons. Their heads are gray to off-white with small black spots and their legs are normally dark gray to black.
Another phase is sometimes called light or normal phase. They normally have light brown carapaces and yellow plastrons. Their heads are normally gray with very small pepper like gray spots and their legs are normally gray.
Chesapeake phased Northern looks very similar to a Concentric phased Centrata. A large percentage of the Northerns found in the Chesapeake Bay of Maryland look like Concentrics or Blue Concentrics, hence the term Chesapeake phased. They normally have off-white to gray carapaces with black rings throughout the scutes. Their plastrons are off-white and can sometimes have black markings as well. Their heads are normally light gray and sometimes light purple with large gray or purple spots and sometimes stripes. Their legs are light gray and normally have medium size spots.
There are a few other variations within the Northern subspecies but they are not as common and are mostly a combination of the phases described above.
Centrata
Malaclemys terrapin centrata (common name is Carolina diamondback terrapin). Centratas can be found from Cape Hatteras, North Carolina to northern Florida.
Their carapaces are normally very smooth and they can range from brown to off-white in color with black rings. Their plastrons are normally orange to off-white, sometimes they can have black markings as well. The skin on their heads range from gray to bone white and they can have small pepper like spots to very large spots and strips. They normally never have black upper jaws. Centratas, like Northerns have a very wide range of color patterns within the subspecies.
Concentric is a term for a light phased centrata. They have off-white to light brown carapaces with black rings throughout the scutes. Their skin is normally bone white with large black spots and sometimes stripes. In a clutch of centrata eggs you might only receive one concentric phased hatchling and the rest will be normal. Many people have been able to breed two concentric phased captive born centratas to each other and produce a higher number of concentric phased hatchlings.
The Latin break down of Centrata: centrum meaning midpoint of a circle, referring to the configuration of growth annuli on each carapacial scute.
East Coast Florida
Malaclemys terrapin tequesta (common name is East Coast Florida diamondback terrapin). Tequestas live on the Atlantic coast of Florida and can be found from southern to northern Florida. Their carapaces have medium grooves throughout the scutes and they are normally black and sometimes dark brown. Their plastrons are normally black or brown. They tend to have medium knobs (dorsal keels) when they hatch but they normally are flat by the time they reach 3 inches.
The skin on their head is normally bone white and they have large black spots and strips. Their upper jaws are always black or dark brown, which makes them look like they have a mustache. They have a black diamond on top of their head. Their legs are normally completely black.
The break down of Tequesta: named after the Tequesta Native Americans of eastern Florida.
Mangrove
Malaclemys terrapin rhizophorarum (common name is Mangrove diamondback terrapin). Rhizophorarum live in the Florida Keys.
Their carapaces have medium grooves throughout the scutes. Their scutes are dark brown with a lighter center, normally a light yellow. They tend to have medium knobs (dorsal keels). The skin on their head is normally off-white to a purple-gray and they have large black spots and stripes, very similar to a Chesapeake Northern face and skin. Their legs are gray with large blacks and stripes as well. They are the rarest of all the subspecies and I have not seen any in the pet trade.
The break down of Rhizophorarum: they are named after the mangrove genus rhizophona, for the type locality.
Ornate
Malaclemys terrapin macrospilota (common name is Ornate diamondback terrapin). Macrospilotas can be found from the northern Keys to the panhandle of Florida.
Their carapaces have large grooves throughout their scutes. Their scutes are black with a lighter center, normally orange or yellow. Their plastrons can range from black with only small marks of orange or yellow to having completely orange colored plastrons. They tend to have large knobs (dorsal keels) as hatchlings and sub-adults. As they get older their knobs tend to go down, especially in females. Females also develop larger head as they age. They develop much larger heads than all of the east coast subspecies.
The skin on their head normally looks translucent with either a hint of pink, yellow, or purple. I have seen several with no spots whatsoever. They normally do not have bone white skin, like some Centratas or Northerns. Their legs are normally soft white to purple with very small pepper like spots.
The Latin break down of Macrospilotas: makros meaning long/large and spilotos meaning spotted, referring to the large yellow or orange spot on each carapacial scutes.
Mississippi
Malaclemys terrapin pileata (common name is Mississippi diamondback terrapin). Pileatas can be found from the extreme western part of the Florida panhandle to the middle of Louisiana.
Their carapaces have large grooves throughout their scutes. Both their carapaces and plastrons are typically completely black. They tend to have large knobs (dorsal keels) as hatchlings and sub-adults. As they get older their knobs tend to go down, especially with females. Females also develop larger heads as they age. Their heads normally have a gray to white base with medium to large black spots and they have black diamonds on top of their heads. Their upper jaws are normally black, which makes them look like they have a mustache and their legs are normally black as well. They are the darkest subspecies.
The Latin break down of Pileata: pileata meaning capped, covered with a cap, referring to the dark dorsal surface of the head.
Texan
Malaclemys terrapin littoralis (common name is Texas diamondback terrapin). Littoralis can be found from the middle of Louisiana to Corpus Christi, Texas.
Their carapaces have medium grooves throughout their scutes and they range from dark brown to light brown. Some can even have with concentric rings within the scutes and others that have darker scutes with light center scutes, not as pronounced as the macrospilota. Their plastrons are normally yellow to orange. They tend to have large knobs (dorsal keels) as hatchlings and sub-adults and as they get older their knobs tend to go down, especially true with females. The females develop the largest heads out of all the subspecies but this can take many years.
Their heads are normally white with a hint of gold, green or blue tints. They normally have black to gray spots with a yellow to gold diamond on top of their heads. Their legs are normally light gray.
The Latin break down of Littoralis: littoralis meaning of the seashore, referring to their habitat.