#xkcd No. 3204
Date: 2026-2-6
Title: Dinosaurs And Non-Dinosaurs
Alt text: Staplers are actually in Pseudosuchia, making them more closely related to crocodiles than to dinosaurs.
Checkmate science!
this post was submitted on 07 Feb 2026
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That is amazing!
What are those in the 'seem like dinosaur - are not' group?
Two pterosauri ("fyling dinosaurs"), plesiosaurus, dimetrodon, and I don't know the name of that other swimming dino, maybe mosasaurus.
Flying dinosaurs, swimming dinosaurs, but not dinosaurs?
That's why I put the quotation marks ;)
The pterodactyl is one
Yes, but if those aren't Dinosaurs, what are they?
Pterosauria is a branch of archosauria, together with dinos and crocodiles. Idk about those in the sea.
Are birds dinosaurs?
I thought that they descended from dinosaurs. And - that doesn’t make them dinosaurs, right?
You can not evolve out of a clade. Any way to group dinosaurs must include all of their descendants.
Taxonomically speaking, birds are dinosaurs.
There isn't a place to put a line between them - all the things that make birds "birds" also apply to dinosaurs.
A super fun fact is that of the two main types of dinosaur, Saurischia ("lizard-hipped") and Ornithischia ("bird-hipped"), birds actually evolved from the lizard-hipped group.
That’s pretty hip.
Isn't that the same logic that technically describes all vertibrates as fish?
I'm sure I can think of vertebrates that have things that make them "them" that don't also apply to fish. For example do any fish have hips of any type? If not i can use "hip or not" to group vertebrates distinctly.
It's similar to the process that lets me differentiate vertebrates from invertebrates in the first place. squishy worm, worm with teeth, worm with jaws, worm with backbone etc.
Bony fish specifically but I'd argue that the common name for the clade bony fish is misleading and that bony fish aren't a subtype of fish but rather a clade of animals descending from a subset of the non-clade category of things we call fish. Not all fish belong to a single clade we can call fish, bony fish descend from one of these unrelated things we collectively refer to as fish.
Basically, I would say the term fish is more like our term for tree (representing a niche rather than clade) unless you would argue all vertebrates are fish. We are a member of the clade bony fish so we are bony fish but we do not fill the same niche as fish so aren't a fish. So "Bony Fish" is a noun distinct from bony (adjective) fish (noun).
*bony fish
We are closer to your average fish (I don't know any specific ones) with bones than they are with sharks (non-bony, cartilage!)
Herrings, salmon/trout, cod/haddock are all bony fish.
The vast majority of extant fish are members of Osteichthyes (bony fish).
In particular, ray-finned fish are bony fish:
Actinopterygii, members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that constitutes nearly 99% of the over 30,000 living species of fish. The vast majority of extant actinopterygian species are teleosts, and by species count they dominate the subphylum Vertebrata, comprising over 50% of all living vertebrates.
Yes. Also humans are chimps, dogs are wolves and wheat and most citrus fruits don't even exist.
Or we could accept that the whole idea of a purely genetic phylogeny with each clade bifurcating into two and later bifurcations always having to be grouped together with no regard for ecological pressures or mutation rates or hybridisation as the unhinged ravings of a geneticist (derogative) who has never touched grass, and move on.