wally-217 t1_iusli1g wrote
Not a paleontologist but Comparative anatomy gives a lot of insight into fossils - e.g. Proportionally long legs (specifically lower legs) correspond to animals adapted for speed or sprinting. Robust bones are indicative of heavy set animals with lots of muscle of fat. Unusually dense bones can be indicative of aquatic animals.
The texture of the bones themselves can reveal even more information - deeper scarring on muscle attachment sites means beefier muscles in that area; rugosities and landmarks on the bones can reveal places where keratin sheathes would anchor to or where blood vessels flow. Quill knobs are seen where feathers anchor on some dinosaurs.
Some fossils are preserved well enough to preserve scales, skin and feathers. A handful of fossils even preserve melanosomes which determines colour. Evolution also leaves lots of remnants of a species' ancestry behind - for example: pliosaur, crocodile and spinosaur teeth are extremely similar but theropod (the group of Dinosaurs spinosaurus belongs to) teeth are flat with serrated edges, so even though spinosaurus teeth are evolved convergently to other fish-eating animals, they have subtle remnants of traits only seen on theropod teeth, in this case being slightly less circular and having faint ridges where the serrated edge used to be. Teeth themselves are hugely informative of diet and environment too to the point that microscopic wear marks can tell you how a herbivore moves its mouth! In mammals, the patterns in teeth is even more unique (compare the pattern on an elephant molar to a cow to a human).
All these things offer different pieces of the puzzle. Phylogenetic bracketing takes all these clues, adaptions and identifying features and models the most likely relationships, this can then reveal where along the chain certain traits pop up (for example, feather-like filaments have been found across a range of distantly related dinosaur and even pterosaurs, indicating that all dinosaurs probably evolved from an animal with some level of proto-feathers). All of this can also be compared with chemical isotope analyses of fossils and the formations they are found in, to build up an even better picture.
Akitiki t1_iut4j60 wrote
This here! Also simply looking at modern relatives; things like deinosuchus probably looked really similar if not basically identical (outside of being much bigger) to modern crocodilians.
Still some interpretation to be had, sure, but we can apply what current birds look like to smaller raptors (microraptor, velociraptor, etc) given they were getting close to modern avians along with cues from the fossils as mentioned above.
I see a picture floating around sometimes of a swan shrink wrapped with no feathers and using its featherless wing as a stabbing implement and people believe it. And some other animals given similar treatment. No. Just, no. We aren't as off as we were, where we had tons of dinos standing upright...
atomfullerene t1_iuwhnm8 wrote
> a swan shrink wrapped
This is from the excellent book All Yesterdays, a book of paleoart. The point of those images wasn't to represent issues with well done reconstructions, but instead to reimagine modern animals if we shrink wrapped them the same way that is (and especially was) done with dinosaur reconstructions in the past...trim muscles, no body fat, no feathers or fur of any sort, no fleshy bits. And then monsterize them a bit because they are dinosaurs after all. A Jurassic Park raptor probably isn't much closer to true life appearance than that swan. And there are plenty of older reconstructions that are further off.
Firm_Brother_7124 OP t1_iuuoy4u wrote
Interesting! How accurate is this estimation?
wally-217 t1_iuv3689 wrote
It very much depends on the species. For something well studied like a T. rex, we have a very complete picture of it's general shape, how it hunted and even how it grew (Adults were incredibly stocky but sub-adults were built for speed - in a loose sense, a bit like a cheetah that morphs into a giant Hyena as it grows!) but how social it was, the skin texture, colour and feather coverage is still speculative. For animals like sinosauropterx, anchiornis and psittacosaurus we have complete pictures of their colours and patterning. Some species are often fossilised in groups or mass burials, which is a strong indicator they were social or partially social animals.
Something like spinosaurus is a good example of something we don't have a huge amount of fossils for (well, we actually had no remaining fossils until the 2014 specimen) and you can see just how much it changed as new fossils were discovered and studied. Fossils of large sauropods are usually only a handful of bones so so we're a long way off the species level resolution that we can reconstruct smaller dinosaurs with. Which is arguably why most sauropod species are reconstructed very very similarly. Many fossils are only known from teeth, which are probably more likely to see the biggest changes as new discoveries are made. Especially for some fossil mammals. And then you have some things like Dunkleosteus which only has a few known relatives, and limited fossils - so we have a good picture of how the head would look! But not much else. And finally we have animals like the Tully Monster, which we didn't really know if it was related to us, insects or mollusks until recently due to how basal (and then derived in its own way) it is, and how there aren't really any known modern analogues.
Generally speaking, we have a pretty solid understanding of most fossil groups as a whole, but lesser known species are ones that will be reconstructed as more generic. The general proportions and posture of many groups as a whole will probably not change much, but we will likely see much more variation between individuals as science progresses (although some groups are inherently more diverse than others) - Deinocheirus and spinosaurus are good examples of this.
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