From ScienceDaily:
Mammalian perineal structure derived from septation of the cloaca is an important evolutionary innovation that allows myriad anatomical configurations, diverse reproductive strategies, and precise excretory control available only to mammals. The researchers were surprised to discover that, despite the perineum’s structural complexity, the muscles of the mammalian perineum show a reemergence of a simple pattern of body wall layering that dates back more than 360 million years ago — during the origin of tetrapods, the first vertebrates to move out of the water onto land. [color emphasis added]
Basal vertebrates, such as fish, organize their body wall into two muscular layers that are important for swimming. However, with the transition from water to land, the body wall of most tetrapods expanded to four muscles layers in order to stabilize their trunks against gravity and facilitate the more complex movements of the limbs during terrestrial locomotion. Amniotes, vertebrates who can reproduce on land and away from water, have four muscle layers in the thorax and the abdomen, but still retain the original two muscle layers in the pelvis and perineum. Mammals, like other amniotes, have four muscle layers in the thoracic and abdominal body wall. Unlike other amniotes, mammals extended the four muscle layers to the perineum. This allows mammals to control their newly derived structures associated with the external genitalia and the anus. Paper. (paywall) – Margaret I. Hall, José R. Rodriguez-Sosa, Jeffrey H. Plochocki. Reorganization of mammalian body wall patterning with cloacal septation. Scientific Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-09359-y More.
“Reemergence”? Was it there all along, hidden in supposed junk? Developed again from scratch? Neither answer is good news for Darwinism. Not that it matters, maybe, in the age of Fixing doubters.
See also: Stasis: When life goes on but evolution does not happen