Morphogenesis of the secondary palate in the Mongolian gerbil (Meriones unguiculatus).

This report describes the prenatal development and closure of the secondary palate in the Mongolian gerbil. Palatal shelves can be regularly observed on day 16, at which time they are directed vertically. On day 17, the shelves show an overall increase in size and length but remain vertically directed. During day 18, palatal shelves are usually in a state of transition from the vertical to the horizontal position. The process of palatal closure (fusion) occurs on the 19th day and is complete by day 20. The process of palatal formation and closure in the gerbil more closely resembles that of the rat and rabbit than that of the mouse.