A newt with conspicuous black spots distributed over the entire body. Dorsally olive green with small yellow or gold flecks, sometimes forming larger spots. A broken, wavy yellow dorsolateral line which runs from the base of the head and onto the tail is seen in some northern populations. Ventral coloration is yellow to orange. Adults are 3.5-5.7 cm snout to vent length (7-11 cm total length). Breeding males develop a tail fin and cornified toe tips. This species apparently does not have the well defined 'eft' stage seen in other eastern North American newts. Two subspecies are currently recognized. The Mexican newt (N. m. kallerti) is relatively dark dorsally and the black dorsal spots are sometimes indistinct against the ground color. The Texas black-spotted newt (N. m. meridionalis) is somewhat stockier in build. The larvae are greyish brown dorsally and pale buff ventrally. Larvae have lateral and ventrolateral rows of light dots on the sides, and also faintly visible bars on the sides of the head. Diffuse dark pigment on the venter sometimes forms a light midventral band. As larvae age, this darker ventral pigment becomes concentrated in small spots; larger spots appear on the sides. (Mecham 1968a; 1968b; Petranka 1998).
Genetically, N. meridionalis is more closely related to N. peristriatus than to N. viridescens (Reilly 1990).
- Mecham, J. S. (1968). "On the relationship between Notopthalmus meridionalis and Notophthalmus kallerti." Journal of Herpetology, 2, 121-127.
- Mecham, J. S. (1968). ''Notophthalmus meridionalis (Cope). Southern Newt.'' Catalogue of American Amphibians and Reptiles. American Society of Ichthyologists and Herpetologists, 74.1-74.2.
- Petranka, J. W. (1998). Salamanders of the United States and Canada. Smithsonian Institution Press, Washington and London.
- Reilly, S. M. (1990). "Biochemical systematics and evolution of the eastern North American newts, genus Notophthalmus (Caudata: Salamandridae)." Herpetologica, 46, 51-59.