Megazostrodon likely fed her young milk produced from glands (milk lines) that ran from her arm pits to her groin. Newborns would have been underdeveloped and unable to feed themselves, as in other mammals.
Megazostrodon had genuine molars, teeth with multiple cusps and twin roots in which the uppers and lowers occlude and grind food between them. Such teeth are replaced only once during growth to maturity, which is a new pattern in this lineage. The first set to teeth typically do not appear until some time after birth. Until teeth do appear, the mother has to feed her young milk.
Megazostrodon was probably an endotherm and nocturnal. The body temperature would not have needed to be so high if active at night. As a nocturnal animal, senses other than sight became more acute. The skin became more sensitive by increasing the number of nerve receptors. The eyes became more sensitie to lower light levels at the expense of color vision with more rods and fewer cones. Hearing became more acute and able to hear higher frequencies. Odors became more important as the twin naris merged to become one at the tip of the snout. The portions of the brain devoted to receiving and interpreting signals became enlarged. The brain was several times larger than in Pachygenelus.
The cervicals were extremely short and the dorsal set was arched. The vertebral articulations allowed the backbone to twist, enabling Megazostrodon to lie on its side, something other reptiles never do. This enabled the young to feed on the mother's milk lines. The lumbar ribs were largely missing.
The scapula was proportionately larger. The forelimbs were more slender and all the limbs demonstrate a greater range of motion.
The ilium was reduced to only an anterior process, like that of a frog. The puboischium was largely behind the hind limb. Two new bones, the prepubes, appeared at the base of the pubis. Though similar to prepubes in fenestrasaurs, they appeared by convergence. The knees of Megazostrodon were tucked in close to the body, but the elbows remained sprawling. The femoral head was a sharply defined hemisphere. The hind limbs were held in a permanent crouch, ready to jump.
Hair covered the body, but the tail remained scaly, like that of an oppossum. Fleshy lips covered the teeth and could be drawn back in a snarl.
If you want to read the book, "From the Beginning - The Story of Human Evolution" by David Peters (Little, Brown 1991), which is where the above images were first published, click here for the PDF. |
