Nephropidae vs Palinuridae
Although they superficially resemble each other in terms of overall shape and having a hard carapace and exoskeleton, the two groups are not closely related. Spiny lobsters (Palinuridae family) can be easily distinguished from true lobsters by their very long, thick, spiny antennae and by the lack of claws. True lobsters (Nephropidae family) have much thinner antennae, and claws on the first three pairs of legs, with the first being particularly enlarged.
Spiny lobsters are found in almost all warm seas, including the Caribbean and the Mediterranean Sea, but are particularly common in Australasia (where they are usually referred to as crayfish or sea crayfish) and in South Africa.
On the other hand, the American lobster (Homarus americanus)—also known as Atlantic lobster, Canadian lobster, northern lobster or Maine lobster—thrives in cold, shallow waters. I wonder if the claw growth is an adaptation more useful in colder oceans.