I was going to argue with you, but it looks like the sharks split from the boned fish and the tetrapods (including mammals) before those two evolutionary lines diverged.
I learned something new today.
1 Like
If you were right, I’d agree with you.
4 Likes
Also, could the giant shark Carcharodon megalodon still be alive today? (Almost certainly not but) maybe!
No, they very much are. Sharks are Chondrichthyes, which as that page notes are generally called the cartilaginous fish. For instance, look up “largest fish” and you can expect to find whale sharks mentioned.
It’s true as @nimelennar says that they are not as closely related to ray-finned fish, coelacanths, and lungfish as us tetrapods are. What that tells you is that fish are not a clade, but rather a grade or functional group – aquatic vertebrates with gills and fins. Whether such a term is useful depends if you are talking phylogeny and taxonomy, or anatomy and ecology.
But in any case it’s the prevailing use in English; to say “sharks are not fish” is as odd a redefinition as to say “jellyfish are not invertebrates” (they also split from us before most of the others did).
7 Likes
I’ll file this under Duh.
2 Likes
I guess there is no denying it, I am OLD. I was taught in high school (early 90’s), that sharks were not fish for a few reasons, the one I remember most being that they had skeletons of cartilage instead of bone. Maybe in the two decades since thinking has changed? Maybe I was stoned that day in biology? But that’s usually how I update my knowledge: the foot in mouth method. Thanks for the excellent explanation.
5 Likes
It’s tricky: had this argument with someone recently about people, monkeys and apes. You’re always told “people aren’t monkeys, they’re apes”, but apes are basically monkeys.
The problem with that our original attempts at taxonomy have all been functional: looks like this, behaves like this, etc. So, for instance, in school I learned that there were 9 phyla of animals (now there’s a horde of phyla, super phyla, sub phyla, infra phyla, whatever, can’t keep track). That was functional: sponges all had certain characteristics, as did nematodes, mollusks, etc. But the truth is that by necessity, all biological divisions are binary: something splits into two different things: not 9, or 12, or whatever. That, of course, would be impractical to model in textbooks, but in a very real sense, sharks are not fish: rather fish are sharks (bony fish descended from a jawed cartilaginous swimming vertebrates, and what’s the definition of shark anyway?).
And of course since we are monkeys as well as apes…we are sharks as well.
3 Likes
I’d argue that’s already a mistake (I think I might have been your someone, unless you mean more recent).
All phylogenetic divisions are binary except in some odd cases, and we tend to want our taxonomy to reflect them. But there are lots of other biological categories. There are ecological categories like herbivore or pollinator, and broad morphological ones like tree or worm. There are more particular ones like ungulate or raptor, both of which were thought to be phylogenetic groups but turn out to have evolved more than once.
And then there are descriptors like slug or fish, used only for those parts of a phylogenetic group that share a particular property. Is it necessary to insist they be treated like they were only about taxonomy and so extended to the whole clade – and thereby made both quite different and redundant, since we already have words like gastropod and vertebrate if you don’t care about the form of the organism?
I’d argue this sacrifices the main point of terminology, which is to make it easier to talk about different concepts, of which clades are only one type. Saying “bony fish are a group of cartilaginous fish”, or “really vertebrates are a type of invertebrate”, might make sense if you only look at the evolutionary tree, but it also means you really aren’t interested in what the animals are actually like.
In any case, I just wanted to point out that either way, not all fish are sharks either. The bony fish and their tetrapod descendants are a sister group to Chondrichthyes, and sharks are only one part of that group; there are also the rays, and the more unusual deep sea chimaeras.
4 Likes
I have already professed love to @anon36081309 in a different thread, and now I feel the need to do the same for @brainspore, @anon15383236, and @Modusoperandi.
4 Likes
Sharks, bears, and spiders: Probably not going to ever hurt you unless you’re doing something wrong.
The Sharkbeariders, on the other hand…
3 Likes
Sharks are a very broad category of fish, with wildly differing behaviors. I am lucky that i had already been diving a while when I first saw the film. Most of my experience with big sharks is dimly seeing them in the distance, as they had already seen me, and they were making themselves scarce. On the other hand, I have seen big hammerheads feeding in shallow water in the Seychelles, and an assortment of big sharks off of South Africa. You are not going to convince me to get into the water there. No matter what sort of background music you play.
1 Like
3 Likes
has anyone ever seen a republican video where Hillary Clinton walks in a room?!?
Well, there goes my late-summer plans…
1 Like
Fish is such a generic term that it ends up being meaningless. It tends to be more of a descriptor than a specific term. To your point, fish is not as specific as saying mammal or reptile.
This topic was automatically closed after 5 days. New replies are no longer allowed.
