One of the pair of mesenchymal swellings (folds) located on either side of the cloacal membrane during the indifferent stage of embryonic development; cranial to the cloacal membrane the folds unite to form the genital tubercle; caudally the folds are subdivided into urogenital folds anteriorly and anal folds posteriorly.
Comment:
We presume this is distinct from AAO:0001003, an external integumentary structure - check with amphibian anatomy ontology developers. AO notes: the text def states mesenchymal swelling, EHDAA2 splits into mesenchymal and epithelial parts