On a small hill overlooking a salt marsh in Madison CT, there is a species specific example of a stone representation of a Malaclemys Terrapin, also known as the Diamondback Terrapin.
Below, the turtle seemingly basks on the top of a stone row.
Ornate Group Baskingfrom: http://www.diamondbackterrapin.com/index/index.php/picture/turtle-setup/
Notice the nuchal notch in the carapace or upper shell, the large head below it...
The forelegs might possibly be a single split humanly enhanced stone. Note the black minerals in the stones that resemble the markings of the terrapin.
(This Diamondback Terrapin appears in this post:
The artistic incorporation of this species specific petroform into a stone row strongly suggests a Native American origin of this "stone concentration."
Other examples of artistic testudinate incorporation: