Distinguishing Characteristics |
Body round, flat with an upward slope towards the center, rigid; no arms; color usually green but can be tan, brown or gray; body covered with short spines; bottom side flat with mouth in the center and anus to the side; mouth with 5 jaws with teeth arranged in a circle (called Aristotle's lantern); bottom with tube feet; top with specialized tube feet, called petalloids, each with 2 rows of pores arranged in the shape of a 5-petal flower; 5 oval-shaped holes (lunules) through skeleton, 1 pair near the top, 1 pair near the bottom and 1 large hole between bottom pair (young may not have 5 holes yet, notches mark where lunules will eventually develop). |
Similar Species |
This is the only species of sand dollar found off Texas.. Another species, M. tenuis, occurs in the Gulf of Mexico but is limited to east of the Mississippi River. It has much smaller spines than our sand dollar. |
Habitat |
Gulf, shallow waters, bury in sandy bottoms |
Maximum Size |
15 cm (6 in) diameter, common to 7.5 cm (3 in) |
Other Common Names |
keyhole urchin |
Previous Scientific Names |
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