“ In meroblastic cleavage, the ovum does not
break up wholly. Molecular clock and fossil relationship recommend platypuses split
from echidnas all around 19-48 million several years ago.
Monotrematum sudamericanum, an additional fossil relative of the platypus, has been located in Argentina,
indicating monotremes were current in the supercontinent of Gondwana when the continents of South America and Australia had been joined by using
Antarctica (right until about 167 million decades back).
In 1947, William King Gregory theorised that placental mammals and
marsupials may well have diverged earlier, and a subsequent branching divided the monotremes and marsupials, but later on analysis and fossil discoveries have proposed this is
incorrect. Cultural depictions of lions have been popular in Ancient Egypt, and depictions have occurred in just about all historic and
medieval cultures in the lion's historic and current range.
In reality, fashionable monotremes are the survivors of an early branching of the mammal tree,
and a later on branching is thought to have led to the marsupial and placental
teams. ”