Why do some non-'ideal' traits exist in organisms?

Amale bird-of-paradise uses a dance to attract mates in which it flaps its tail feathers on the ground and jumps around a potential female mate. a different male bird-of-paradise does a similar dance but it jumps around the female in the opposite direction. the female bird is only attracted to one style of dance, in one direction. this is an example of speciation.

Based on anatomical similarities, to which modern animal is dr. digger’s creature most closely related?

Has regulatory areas for thirst, hunger, body temperature, water balance, and blood pressure