Gulf ghost crab

Gulf ghost crabs are medium-sized ghost crabs with deep bodies, reaching a maximum overall body diameter of 6 in (15 cm). The upper surface of the body is generally dark gray with lighter colored marbling. The underside of the body, the tips of the walking legs, and the claws are creamy white. Their coloration varies, usually matching the color of the sand surrounding them, but they are easier to see on black volcanic sand and on light-colored dry sand. The carapace is squarish in shape and wider than it is long, with a length around 43 mm (1.7 in) and a width of 50 mm (2.0 in). It is thickly covered with rough, small bumps (tubercles). Their eyestalks are large and elongated, but do not possess "horns" as in some other ghost crab species. The outer half of margins of the eye sockets curve distinctly inwards, with the outer edges (exorbital angles) triangular in shape with a sharp, forward-facing, pointed end. Like other ghost crabs, one of the claw appendages (chelipeds, the first pereiopod pair) of gulf ghost crabs is much bigger than the other. The palm of the larger cheliped is elongated with a serrated lower edge and covered with tubercles on the upper surface. It features stridulating (sound-producing) ridges on the inner surface of the palm, which is important for identifying different species within the subfamily Ocypodinae. In gulf ghost crabs, the stridulating ridge is short and composed of a row of 21 to 22 tubercles. The smaller cheliped tapers towards a pointed end. The second pair of walking legs are not more than two and a half times the length of the carapace. The fourth pair is relatively smaller and weaker in comparison to the other three pairs, reaching only to the middle of the propodus of the third pair. The mera and carpi of all the legs are naked, but the propodi possess fur-like bristles (setae) on for the first three walking leg pairs varying by sex. In males, the propodi of the first and second pair of walking legs have their upper forward surfaces covered with setae. The propodi of the third pair of walking legs only have setae on the upper margin of the propodi. In females, the propodi of the third and last pair of walking legs do not possess bristles on the upper surfaces of their propodi. The first gonopods (modified copulatory organs) of males are also distinctively complex in shape, with a triangular cross-section at the base and becoming hoof-like towards the end. This characteristic is one of the diagnostic criteria for the genus. The covering (operculum) of the genital duct of the females has four sides and is membranous and slightly calcified. The genital slit is narrow and aligned along the middle of the operculum.