Mexican Spinytail Iguanas (Ctenosaura pectinata) have distinctive keeled scales on their long tails which gives them their common name. They are one of the larger members of the genus Ctenosaura, capable of growing to 140 cm (4.6 feet) in length, with females being slightly smaller than males at 100 centimetres (3.3 ft), and are typically brown or grey-brown in coloration with a yellowish ventral surface. They have a crest of long spines which extend down the center of their back. Hatchlings are often a bright green color with no pattern and darken as they age.
The Mexican Spinytail Iguana is native to Western Mexico from Sinaloa to Oaxaca.
This iguana has been introduced to Brownsville, Texas and South Florida and reproduces in the wild in several feral populations. On the south-eastern Florida coast, these iguanas have been found on Key Biscayne, Hialeah, and in Broward County. On the south-western Florida coast, it has been reported on Gasparilla Island. It is currently estimated as of December 2007 that there are 12,000 iguanas on this island, descended from a trio of pet lizards released by a resident in the 1970s.
They are regarded as a "nuisance animal" on Gasparilla island because the iguanas eat ornamental flowers and shrubs and prey on nesting birds and sea turtleeggs. They have been known to chew through electrical and telephone cables. They may also carry salmonella and their prehistoric appearance has been known to scare residents. As the iguanas like to burrow in the sand it is feared that their tunnels could cause dunes and even seawalls to collapse and deprive the island of crucial protection from landfalling hurricanes.