Specimens of Poecilosclerida taxa, collected from an insular coral community on the Pacific coast of Mexico, were identified as members of the family Crambeidae Lévi, 1963. They were associated with larvae and rhagon phases by using morphological characters, the nucleotide relationship and genetic divergence of three independent loci, two mitochondrial (COI and 16S rDNA) and one ribosomal (28S rDNA C3–C5). Crambe insularis sp. nov. differs from the general skeletal architecture in the genus Crambe Vosmaer, 1880, by its reduced spiculation defined by the presence of ectosomal and choanosomal monactinal megascleres, and the absence of microscleres. Bayesian and Maximum–Likelihood analyses of three loci supported the clustering of larvae, rhagon and adult sponge, all closely related to Mediterranean Crambe crambe (type species of the genus Crambe), and with South American Crambe species (C. chilensis, C. maldonadoi and C. amarilla) as sister species. The larva of C. insularis sp. nov. corresponded to the typical parenchymella larvae poecilosclerid species but with the presence of subtylostyles and styles. Ontogenetic process about the larval and rhagon of this new crambeid are provided. The morphological characters and molecular affinities of Crambe insularis sp. nov. are similar to Monanchora genus, and the implications are further discussed. This is the first taxonomic and molecular study with an integrative approach that includes other diagnostic features such as larval and rhagon development for the description of new species in Porifera.