This species reproduced by budding, with a term of at least a month. Their equivalent of Human birth was apparently individuation, and after that the offspring was referred to as hatchlings. The number of hatchlings hatched in a singe individuation could range at least from two and eighteen. During the budding process, it was advised for the parent not to come in contact with hazardous materials.
The number of possible hatchlings in a given litter appears to range anywhere from two to twelve, as described by Julian Bashir in DS9: "Apocalypse Rising". Upon being told that Vilix'pran was budding again, Kira Nerys asked how many that would make now, to which Doctor Bashir recounts his first litter as twins, his second as quadruplets and that therefore, his third could bring the total anywhere between eight and eighteen (adding between two and twelve to his previous six).
A specific concern with young members of their children was that their little wings might get tangled. Because of this oversight was considered necessary.
This also implies that Vilix'pran's species cared for their offspring.
This species was never named and never linked to a species seen on screen, though because of this it also remains possible that it is a species we are already familiar with. In the end its existence is only extrapolated from Vilix'pran obviously alien characteristics.
Given the wings they may be an avian species, but the existence of hatchling ponds also seems to suggest a desire or need for aquatic environments in at least in the early stages of life. Though Vilix'pran was consistently referred to as he, budding in Earth species is generally linked to asexual reproduction, and thus it is conceivable that this race may only have one gender.