On today’s Wikipedia front page, there’s a drawing of a reconstructed dinosaur, what the dino-scientists think Diodorus scytobrachion looked like.
Thing is, they only have four bones: an upper front leg bone, an upper back leg bone, a lower back leg bone, and a piece of the jaw bone.
How can they make a prediction of what the dino looked like from only four bones?
( And no, Discourse, this topic has nothing to do with “Diners, Drive-Ins and Dives! How many have you been to?”)
Be nice to test a scientist the way you would in " Name that tune" I can name the dino with 2 bones"
Mostly, it’s based on similarities to other dinosaurs that they’ve found more of. Which, yes, can be very error-prone. But if you find one single bone, which looks a lot like a bone from an already-known species except 20% bigger, then your best guess to the animal it came from is something that looks, in total, like that known species, except 20% bigger. That “best guess” might not be very good, overall, and it’s likely that your new dino has several other differences, but there’s no better guess you can make, since you don’t know what those other differences are.
And I would imagine that even a partial jaw bone would be very helpful, if it has any teeth in it, because that would be a good indication of the critter’s diet: meat v plant?
Major differences in dinosaur shape manifest at the family level and at genus it comes down more to details to differentiate species.
Palaeontologists will know from the four bones (if they find usefully diagnostic pieces rather, say, than fairly generic pieces of rib, AND if they can reliably say they came from the same critter - but that’s another whole story) that they come from a particular family because of their size and overall shape.
Then within that its a matter of comparing against known specimens (of which there could be hundreds of well-described specimens in your own lab or, in other cases, a handful on the other side of the world, or destroyed in WW2 and only known from bad drawings) how closely they match existing specimens.
A specimen may be similar enough to be attributed to an already named species, but hopefully the bones extend the knowledge of the critter or are in better shape. If there is no direct match then the palaeontologist’s job is to describe it in a publication and ascribe it to either a new species with a name, which might also be different enough to be a new genus as well, or to say more cautiously that it is Tyrannosaurus sp, so a tyrannosaur based on their characteristics but not enough to either say new or known.
The line for new species is arbitrary and different from living species. For some dinosaurs there are gender differences and very different growth stages overall or in things like head armour, while others start in one shape and just zoom to larger overall size. If you have the same bone but its different in size is that a growth thing or enough to demarcate it? What if its different in the location of blood vessel openings and attachment points? I suspect my arm bones and Arnold Schwarzenegger’s would be seen as different enough to make palaeontologists start arguing.
The trend in palaeontology over time has been to reduce the number of species, by pulling differentiated species into one, because of better understanding of within-species variability, and it being much easier to see what’s already in the museum store in Berlin, Cape Town and Detroit. Some species were known by so few remains and were ascribed to different families - like the therizinosaur, while others mismatched skull and body [a ‘chimera’ - eg the history of brontosaurus].
Some animals are known from only a few teeth:
Dental Detectives Identify New Species From A Lone Tooth Fossil (forbes.com)
Speaking of a one-tooth dino, don’t forget the infamous one-tooth Nebraska Man. And can we ever forget the Dr. Matrix sidekick, One-Tooth Rhee?
There are plenty of specimens for which it’s debated whether it’s a new species, smaller than previously-known species, or if it’s just a juvenile of that species. Or the reverse: Taurosaurus is probably a larger species than, but related to, Triceratops, but I’ve seen it posited that all of the Triceratops specimens we’ve found have just been immature Taurosauri.
They absolutely need an intercostal clavicle.
Or so I’ve heard. Bringing Up Baby (1938) -- George absconds with David's bone. - YouTube Bringing Up Baby (9/9) Movie CLIP - The Dinosaur Falls (1938) HD - YouTube
(I hope it’s not too soon for a joke answer.)
Its only been 65 million years since the Chixculub meteor - its way too soon to joke of such things.
That reminds me of this meme:
Cute, but an actual paleontologist would be able to deduce the need for lips and cheeks to go with those sorts of teeth. They might well get the shape of those lips and cheeks wrong, but they’d at least be present.