Sirenids are endemic North America salamanders, with two genera and four species currently recognized. These are highly aquatic, nocturnal amphibians and they are predator and scavengers in aquatic environments. They lack a pelvis and the front legs are greatly reduced. They survive droughts by cocooning in the mud, using their skin to produced mucus for protection and stored body fat for a reserve energy supply. Gas exchange occurs by way of the gills but is minimal (only about 3% of their oxygen is obtained this way), they also exchange gas through their skin and lungs. Sirens make noises, although they lack vocal chords, some of these sounds may be involved in communication between individuals. The fossil record extends back to the Upper Cretaceous of Wyoming and Montana. It has been suggested that sirens be placed in an order separate from other salamanders. Fertilization is most likely external, but little is known about courtship. This lack of knowledge was recognized by George K. Noble in his 1931 book Biology of the Amphibia, he wrote:

"Very little is known about the breeding habits of Siren and Pseudobranchus, except that the eggs of both are large, pigmented, and laid singly or in smal groups. The larvae of both, soon after hatching, have elongated bodies approaching the form of the adult. This in itself would suggest that the Sirenidae is an isolated group. The larvae of both genera, as they mature, have the ability of reducing their gills to mere stumps if respiratory conditions in the aquatic medium are not suitable to them. This is not a metamorphosis but merely a temporary loss of the gills. The larvae never undergo a complete metamorphosis...."

Lesser Siren, Siren intermedia Barnes, 1826. This species occurs on the the coastal plain from southeastern Virginia to central Florida, southern Georgia and Alabama, then northward in the Mississippi drainage to Missouri, central Illinois, Indiana, Kentucky, and Tennessee. It occurs in Oklahoma and east Texas and extends into Tamaulipas (Mexico). Isolated populations occur in southwestern Michigan and north-central Veracruz, Mexico. Sherman Bishop wrote about these in his 1943 book, Handbook of Salamanders, Comstock Publishing.

"Common in cypress and pinewoods ponds and ditches, where they hide by day beneath bottom vegetation and stranded logs and bark."

A Dwarf Siren, Pseudobranchus striatus ssp. of unknown origin. These small salamanders are restricted to the southeastern USA and inhabit freshwater habitats with muddy or soft substrates.