abnormal embryonic cloaca morphology abnormal primitive urogenital sinus morphology Note that the term "urogenital sinus" may refer to the primitive urogenital sinus present as a transient developmental structure in most mammals or it may refer to a condition in which an unseptated cloaca persists in animals longer than normal. abnormal UGS morphology any structural anomaly of the ventral part of the cloaca remaining after septation of the rectum, which further develops into part of the bladder, part of the prostatic part of the male urethra and the urethra and vestibule in females MPheno.ontology csmith 2010-04-12T12:33:14Z MP:0010116