Answer:
They both had a tail as an embryo.
Their arm and leg structure is similar but may have a different function.
Step-by-step explanation:
They both had a tail as an embryo.
Vestigial structures are those body parts that have lost or reduced their original function during the evolution of a species. These vestigial structures might be found in many animals, including human beings. Vestigial structures were plenty functional for common ancestors. But with evolution, they degenerated, stunted, and became rudimentary for some of the new species.
During the first 4 months of embryogenesis, all mammals have a tail at some point in their development. Dogs develop this structure and keep it during their whole lives, but humans lose it with time during embryogenesis. The tail disappears, and its forming vertebras get fussed with each other composing the coccyx, which represents a vestigial structure. This tailbone is the remnant of a missing tail.
In many animals, the function of the tail is to stabilize, equilibrate and mobilize. But in humans, the coccyx, located at the end of the vertebral column, has lost this original function.
Their arm and leg structure is similar but may have a different function.
The fact that whales, humans, and dogs all have the same bones in the same order, but they matured differently in later embryological development, is an example of homologous characters.
Homologous characters have the same fundamental structures. They also share the same relations with adjacent structures, and they have the same embryological development.
These structures might show variations between organisms exhibiting them, according to their function and to the environment in which the organism lives.
These homologous characters are common in organisms related and that share a common ancestor.