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Do all sea creatures that have scales have to have fins?

Do we know of any sea creatures that have only scales without fins?

I'm especially interested in fish that have scales but no fins.

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  • $\begingroup$ The 'fish' part of this question may be circular, since fishes are a paraphyletic group. From wiki: "A fish is any member of a paraphyletic group of organisms that consist of all gill-bearing aquatic craniate animals that lack limbs with digits". In that definition, 'lacks limbs with digits' is a near-synonym of 'has fins' (the alternative being 'has lost all limbs'). If the group 'fish' were defined in the normal way (i.e., by phylogeny), then all of the groups mentioned in @Alan Boyd 's answer would count as fishes! $\endgroup$
    – bshane
    Oct 24, 2015 at 2:03
  • $\begingroup$ Very interesting question. It is stated in the Mishna (Ancient Jewish Texts) [Chullin 3:7] that there are no fish that have scales and not fins. Of course the definition of fish they were referring to was the swimming variety (not slithering or crawling). Later commentaries say that it was thought that the scincus marinus actually had scales and not fins. But it was redacted, due to the "skink" having legs, making it more of a lizard than a fish. So to answer the question, currently there is no fish (using the commonplace definition) that has scales and not fins. Plus a bunch of Rabbis put the $\endgroup$
    – AquaNUT
    Aug 4, 2020 at 2:40

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How about marine reptiles? Sea snakes have a paddle-like tail, so perhaps you would claim that as a fin, but maybe marine iguanas would qualify? And, of course, sea turtles.

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  • $\begingroup$ Thanks Alan. Maybe you know of fish that answer the criterion? $\endgroup$
    – MichaelS
    Oct 28, 2012 at 16:07
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    $\begingroup$ Definitely not. Since the tail is the caudal fin, this hypothetical finless fish would have no means of locomotion. $\endgroup$
    – Alan Boyd
    Oct 28, 2012 at 16:44
  • $\begingroup$ Eels, but they have caudal fins... Would you consider rays to be finless?... Just checked, a ray's wings are considered fins... $\endgroup$
    – AMR
    Oct 23, 2015 at 21:34
  • $\begingroup$ Chitons have scales,but not like fish. $\endgroup$
    – peter
    Mar 20, 2018 at 18:36

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