A robust build and a length of 16-17 inches (including the long tail) is a typical size for an adult giant ameiva.
For well over a half century Ameivas, the large, economy size of the whiptail/racerunner clan if you prefer, have been prominent in the hobbyist reptile trade. Of the 3 dozen or so species in the genus, 2 are by far the most commonly encountered. These are the giant and the dusky ameivas. For decades the two were considered diverse color phases of the giant ameiva, Ameiva ameiva, but they are now known to be 2 entirely separate species (but more on this later). Firstly, let’s take a look at the big, very pretty, and quite common “green phase” of the giant ameiva. In fact, although the amount of green may vary, the green phase is currently the only phase of this 15 to 20 inch long teiid lizard. Despite the color reference in its name, this neotropical lizard is not entirely green. It is olive-tan anteriorly, olive-lime posteriorly, sky blue in the groin, pale blue to sky blue on the lower sides fading to bluish white ventrally. Trying to describe the positioning of the black flecks and off-white ocelli would be an exercise in futility. It is far better (and much easier) if I simply refer you to the photos.

Like most teiids, ameivas (please note that when used as a common name the word is not italicized) are sun worshippers and can often be seen basking in full sunshine during the hottest part of the day. The examples on which the Miami population is based originated (or at least were shipped) from Barranquilla, Colombia in the 1950s. They are wary lizards and if startled will quickly retire to areas of ground vegetation or a home burrow. Omnivores, in the wild this lizard actively forages during the heat of the day, often scratching insects from beneath the surface of the ground. Besides insects this ameiva consumes all manner of small invertebrates as well as berries and other vegetation. Captives will accept pinky mice, and there is no reason to believe that those in the wild would not eat nestling mice or nestlings of ground nesting songbirds.

I have noticed that some care sheets mention a hot spot of 90F for these lizards. I submit that a brightly lit hot spot of 110-120F would be more appropriate, with the terrarium providing a a thermal gradient to a temperature of 75F on the cool end.