are pycnofibers and feathers the same structure just diverged early on?
Short answer: Maybe, but really the question is kinda unanswerable currently
Long answer: The answer to this are built on not just one maybe, but multiple layers of maybes. To start with, in case anyone's unfamiliar, let's talk about analogous and homologous structures. In evolutionary biology, a physical feature is homologous if it is shared between two species, and the common ancestor of those two species also had that feature. A common example is that the arm of a human and the wing of a bird are homologous, because we share the same pattern of bones and our distant common ancestor had those same bones!
On the other hand, a physical feature is analogous if it has a shared function, and it may or may not share an evolutionary origin! So for example, a bat's wing and a bird's wing are both analogous (same function, powered flight) and homologous (same bone pattern shared with common ancestor). A bird's wing and a dragonfly's wing, however, are analogous, but are not homologous (they do not share an evolutionary origin).
This table sums it up in a way that I find helpful, comparing analogous structures in insects and mammals. Via Wikimedia Commons.
So, the fuzz on dinosaurs and pterosaurs are pretty evidently analogous structures. They provide the same functions: temperature regulation, probably display, possibly smoothing the body's silhouette in flight? But the key question is, are they homologous? Did the common ancestor of pterosaurs and dinosaurs also have fuzzy structures?
Now, let's get to those multiple layers of maybes, starting with the issue of whether even dinosaurs had a fluffy common ancestor. We see evidence of filamentous structures in both theropods and ornithischians. These structures maybe come from the same evolutionary origin, and if they do, then the common ancestor of all dinosaurs right at the base of the tree also had filaments. As far as I'm aware, whether or not this is likely is a fairly subjective matter, but as you can probably tell from my palaeoart I lean towards the idea that dinosaurs were ancestrally fluffy.
This little fellow, Lagerpeton, is one of the closest things to a dinosaur that isn't actually a dinosaur. If the ancestor of all dinosaurs was feathery, this guy probably was too!
If dinosaurs were ancestrally fluffy, then maybe the filaments of dinosaurs and pterosaurs come from the same evolutionary origin. If ancestral dinosaurs were fuzzy, that puts two very closely related lineages of fuzzy archosaurs very close together in time, some point in the Middle Triassic probably. If that's the case, then it makes sense that the common ancestor of these two groups was probably fuzzy.
However, you'll probably notice that this hypothetical scenario where ancestral fuzz is likely is constructed on top of the assumption that dinosaurs were ancestrally fuzzy, which is something that's still not fully proven. It's not even certain that all dinosaur fuzz is homologous, which makes pterosaurs tricky.
Even whether the earliest pterosaurs, like Peteinosaurus, had pycnofibres is currently only a matter of hypothesis!
The reality is the evidence which would most easily resolve the mystery currently does not exist. If, say, a Triassic dinosaur and Triassic pterosaur were discovered with fuzzy filaments then that would basically confirm that these two very close groups we both ancestrally fuzzy. Even better still would be some basal avemetatarsalian from the Middle Triassic with preserved fluff. That's basically like asking for the Holy Grail though, a genuine common ancestor of pterosaurs and dinosaurs.
Unfortunately, the oldest records we do have for feathered dinosaurs and pycnofibred pterosaurs stop at about the Middle Jurassic. Any older than that, and we lose the sites with immaculately fine silt grains that preserve soft tissue like feathers. That's not to say a future beautiful Middle Triassic silt bed couldn't show up, and oh boy I really hope one does eventually, but for now there's simply nothing out there to offer concrete proof.
Jeholopterus, an anurognathid pterosaur from the Middle to Late Jurassic of China, preserved with evidence of pycnofibres. Via Wikimedia Commons.
So in the absence of this proof, what do we do? I'd consider Occam's Razor a decent guiding principle here, although it's less reliable in some other areas of evolutionary biology. Occam's Razor basically states that the most reasonable explanation is one that doesn't unnecessarily multiply the entities of a problem.
To put it another way, it seems more reasonable, in an evolutionary sense, that three closely related groups (ornithischians, theropods, and pterosaurs) got their fuzziness from one fuzzy common ancestor. The alternate explanation is that two (or possibly three) very closely related groups all independently evolved remarkably similar feathery coats from being initially scaly.
Occam's Razor isn't foolproof, and there's a reason that we have the term convergent evolution, but in this case I think we should consider it a reasonable guess that the common ancestor of dinosaurs and pterosaurs had some sort of fluffy filaments, and that feathers and pycnofibres are indeed homologous.
But just to be clear, this is not the answer!! This is a best guess, a hypothesis based on available lines of evidence that disappear in the crucial stages of its evolutionary history, and the application of a logical rule of thumb to cap it off. Just because that's the side I lean towards, doesn't mean that the issue is settled or that I wouldn't change my perspective if new evidence came to light. That's the great thing about science after all!
So, I do hold to my original statement that right now, this question is not truly answerable (even though I've now spent almost 1000 words trying to answer it). We can guess and hypothesise, but for now the real answer remains out of reach.
I just saw a post on Facebook of a local taxidermist restoring a mount from the Field Museum. In the description of this mount, she said “Although I do not know its origin, based on how it was mounted originally id say its safe to say this animal died of natural causes.”
And that got me thinking, because it’s a leopard. It absolutely did not die of natural causes. The Field Museum, like literally every other big natural history museum, commissioned all kinds of hunts in the 1900s-1930s where animals from across the globe were hunted en-masse. That’s how we got scientific specimens. It’s barbaric by today’s standards, but it was a different era back then and we didn’t have the same standards. This isn’t an excuse, but it is an explanation.
And there’s no way in hell she doesn’t know this, because she used to be a scientific illustrator at the museum. The Field makes it very clear where these animals came from. They have public signage about it, and it’s even more clear down in collections.
It kinda got me thinking again about my feelings re: ethics in the natural history and vulture culture community. We seem to really like it when we can justify the death of an animal as “ethical.” “It was roadkill.” “It died of natural causes.” “Ethically collected.” “Ethically sourced.” Ethics has become SUCH a buzzword, and it’s... I dunno. It kinda feels like there’s a part of the community that doesn’t want taxidermy to be as conflicting as it is, like they want it to be a feel-good hobby that doesn’t center around the fact that something did have to die to make the art you’re collecting.
To me, that’s kind of the beauty of it, looking at death and repurposing what’s left over.
What does ethical taxidermy mean? Does it mean the animal didn’t experience pain? If that’s the case, then you can’t call roadkill ethical. Does it mean the animal’s death was inevitable, and that it would have died anyways and you’re just scavenging the parts? Does it mean that the animal suffered minimally throughout its life? Does it mean simply that taxidermy wasn’t the end goal of the animal’s death and that its death, whether that was at human hands or natural causes, had a different purpose in mind?
There’s a sister train of thought to this as well. Natural history museums- I’m talking the old ones established in the 1800s-1900s- were colonialist endeavours. In many ways they existed to show off the natural resources of a nation’s colonies and territories. There was a lot of resource extraction for these museums- white scientists would go places, shoot as much wildlife as they could, harvest as many native plants as they could, and then come home to exhibit the stuff. It wasn’t so outwardly egregious as museums that were essentially designed as colonial treasure houses (like the British Museum), but it presented a very... strange way of looking at environments, because a lot of these natural history museums ignored the people who were there. And that meant creating this idealized (primarily African) landscape that was just big game as far as the eye could see, a playground for rich white hunters. When people were involved, they were... basically treated like a different sort of animal, something to be gawked at rather than understood. It was wildly dehumanizing, and it’s a legacy that natural history museums are still grappling with today.
To say that a leopard- one of the African “Big 5” game animals- in a vintage museum collection died a natural death is disingenuous at best and intentionally misleading at worst. I really wonder what she was thinking when she made multiple posts (that nobody has commented on) about how she assumes this animal died naturally.
Soooo I have some exciting news!!!!
A couple months ago, I submitted an entry to the Waterhouse Natural Sciences Art Prize, a pretty fancy art contest hosted by the South Australian Museum. This was the piece I submitted, a papercraft lightbox entitled “An Outback of Ice and Sea”, and it’s taken a good month of my life getting it all together!
And I am very excited to announce that I have been selected as a finalist! Any of y’all who are in South Australia, you’ll be able to come and see my work (and a whole bunch of others’) on display at the SA Museum from the 4th of June to the 7th of August!
This piece is a scientific recreation of the Bulldog Shale formation, an opal-rich fossil locality in the desert of my home state of South Australia. 110 million years ago, this place wasn’t a desert, but an icy inland sea near the South Pole that was brimming with life! Every animal species in this artwork is based on fossil evidence from the region, down to the crinoids and brittle stars and bivalves!
The star of the piece is Umoonasaurus demoscyllus, a small plesiosaur with crests on its head that was local to this area. The Umoonasaurus is pursuing Ptyktoptychion eyrensis, a giant relative of modern-day ratfish while belemnites and ammonites bod in and out of the seaweed. And overhead amongst the icebergs, the giant pliosaur Kronosaurus queenslandicus looms.
I’m so proud of this piece as something that I’ve poured hours of love and research into, and I’m so thrilled to have been selected to be a part of this exhibition! The details on the museum website are here if anyone’s curious, please do let me know if you got a chance to see the exhibition in person!