Atheism is unreasonable

[Anomalocaris]

however an early mammal very closely related to birds and reptiles and sharing a number a characteristics with them including egg laying.

Minor quibble, Shared primitive trait, such as egg laying, does not denote close evolutionary relationship. Only shared derived trait can be an indication of closeness in relationships.

Birds and earliest mammals clearly share few true common derived traits, and those which they might superficially appear to share, like endothermy and insulating body coverings, are clearly derived separately through convergent evolution, and do not share the same derivation.

So early mammals are not closely related to birds at all. The earliest mammals are already separated from birds by 150-200 million years of independent evolution from carboniferous era (or earlier) onwards, along two widely separated evolutionary lineages. So Platypus, only ~150 million years separated from humans, is already as different from any birds as humans are from platypus.