Isaac Asimov, “Hostess” (1951):

There were four fingers but no thumb. Each finger had five independent ball-and-socket joints. In this way, the flexibility lost with the absence of the thumb was made up for by the almost tentacular properties of the fingers. What was even more interesting to her biologist’s eyes was the fact that each Hawkinsite finger ended in a vestigial hoof, very small and, to the layman, unidentifiable as such, but clearly adapted at one time to running, just as man’s had been to climbing.

[…]

“[…] Look, there are five intelligent races in the Galaxy. These have all developed independently, yet have managed to converge in remarkable fashion. It is as though, in the long run, intelligence requires a certain physical makeup to flourish. […]”

[…]

“Now when the differences among the intelligences are closely investigated, it is found over and over again that it is you Earthmen, more than any of the others, who are unique. For instance, it is only on Earth that life depends upon metal enzymes for respiration. Your people are the only ones which find hydrogen cyanide poisonous. Yours is the only form of intelligent life which is carnivorous. Yours is the only form of life which has not developed from a grazing animal. And, most interesting of all, yours is the only form of intelligent life known which stops growing upon reaching maturity.”

Adrian Tchaikovsky would like a word.

Rocky from Hail Mary is sort of crab-like, and I think they're making a film adaptation...

Yeah, I hate that so much. Often times, it's clearly just easier/cheaper to put makeup on a human actor, or at least for the aliens to be able to use the same equipment. But it's so boring. If I want to see a humanoid with different skin color, I'll visit my neighbor.

iirc, in Star Trek the Klingons descend from a crab-like ancestor. I mean, yes, I understand what you’re getting at but I still think it’s kinda cool that Klingons are sort of humanoid crabs

Prador Moon literally has giant space crabs as the antagonists.