Ctenosaura similis, commonly known as the black iguana or black spiny-tailed iguana

 

According to Wikipedia, https://en.wikipedia.org/wiki/Ctenosaura_similis ia found in Mexico and Central America which is probably why I saw this one in Mexico. Here is a quote from Wikipedia,

Ctenosaura similis, commonly known as the black iguana or black spiny-tailed iguana, is a lizard native to Mexico and Central America. It has been reported in some Colombian islands in the Caribbean Sea and Pacific Ocean, and has been introduced to the United States in the state of Florida. It is the largest species in the genus Ctenosaura. They are typically found in areas such as grasslands and forests.

The Guinness Book of World Records lists this as the world's fastest lizard, with a maximal sprint speed of 34.6 kilometres per hour (21.5 mph) also from Wikipedia.