You're Doing It Wrong: Microraptor Tails and Mini-Wings

Type specimen of Zhenyuanlong, doing its best Archaeopteryx impression.

Just a short PSA today, and once again, it's about a paleoart meme that has outstayed its welcome.

Microraptor was the first time we got a good look at the feather pattern of dromaeosaurids. This is a big problem for two reasons. One, microraptors were small. That means that artists who were looking at them to extrapolate for bigger, more famous "raptors" could easily and somewhat justifiably write off their huge wings as a product of their size. Sure, we thought, microraptors had big wings, but they're tiny animals. Surely the bigger, more terrestrial dromaeosaurids didn't need such big wings. They probably still had wings, but they'd be smaller. Why would Velociraptor need such proportionately huge wings if it couldn't fly or glide?

Meme number two: that tail. I admit to being one of the first to go overboard when I fell, head over heels, for the "puff tailed dromeosaur" fossil (now the holotype of Cryptovolans, a synonym or close relative of the Microraptor) back around 2000. This was the first evidence we had of the tail feather style in dromeosaurids (or evidence that they even had remixes and rectrices at all. Remember When Dinosaurs Ruled America? That was plausible at the time it was being made). Naturally, having Microraptor plus Caudipteryx showed that the ancestral condition of pennaraptorans was a fan of feathers at the tip of the tail, not a fuzzy Sinosauropteryx like tail or a fully-vaned Archaeopteryx like tail. So artists ever since have been drawing dromeosaurids and troodontids and oviraptorosaurs with microraptor tails.

But that turned out to be wrong! It's an accident of history. We're now learning that Microraptor and Caudipteryx are weirdos.

It shouldn't be a surprise, either. "Dave" (NGMC 91), a famous early feathered dromaeosaurid specimen, clearly has a long, lozenge-shaped, sort of Archaeopteryx-like tail. People draw it with a microraptor-tail anyway, because that's how dromaeosaurids are supposed to look.

Jinfengopteryx showed again an Archaeopteryx-like tail in troodontids and/or early eumaniraptorans. It was treated as the weirdo among microraptor-tailed relatives.

Similicaudipteryx showed a big, luxurious tail fan extending right to the hip, despite having a pygostyle which is often (incorrectly) associated with a fan restricted to the tail tip. It sometimes gets shown with a Caudipteryx-tail anyway.

Anchiornis has an archaeopteryx-tail too, as shown by numerous well preserved specimens.

Even Jeholornis, a classic example of a fan-tipped tail adapted for display, might be tricking us due to preservation. Among early pennaraptorans, archaeopteryx-tails seem to be the norm, while microraptor-tails are the exception.

Zhenyuanlong fossil and reconstruction by Zhao Chuang.

Zhenyuanlong is newer, but puts the final nail in the coffin of both feather memes. It's beautifully preserved in a pose very similar to the classic archaeopteryges, and it has almost the same feather proportions. That means not only an archaeopteryx-tail, but big giant wings comparable in proportion to Archaeopteryx despite its puny forelimbs. To their credit, the artists who produced early press images of this animal showed the right feather distribution and proportions.

Zhenyuanlong is about the same size as your average Velociraptor. Like Velociraptor, it was probably a terrestrial predator rather than an arboreal glider. And yet it has big, archaeopteryx-wings and an archaeopteryx-tail, just like almost all known pennaraptorans.

What reason is there to think Velociraptor would be different? None.

Which specimens show the kind of mini-wings usually given to large dromaeosaurids? "Dave" comes close, but it's a juvenile, so it's hard to count that one. Once again, the idea of mini-wings likely comes from the mini-winged Caudipteryx. Our first look at remiges in a non-avialan dinosaur unfortunately came from that weirdo, and the idea has been carried forth as a meme ever since. Even Similicaudipteryx has big archaeopteryx-wings. Protarchaeopteryx probably did too, though it is often restored looking like Caudipteryx because they were described together. There's been evidence presented for the idea that the short, stout-forelimbed ingeniine oviraptorids probably had even bigger wings, and that their short, sound limbs correlate with support for a bigger complex of wing feathers.

And, as many will know by now, Velociraptor had something extra: Quill knobs. Not all feathered animals have these, and they are most prominent in species with large feathers that need to be especially strongly anchored. Archaeopteryx lacks quill knobs, as does Zhenyuanlong and most of the species mentioned above. It is reasonable to speculate that the presence of quill knobs in Velociraptor means it had even bigger wing feathers, proportionately, than Zhenyuanlong or Archaeopteryx!

Despite all this, the most prevalent paleoart memes of the early 21st century are going strong. My favorite Kickstarter right now besides Saurian (unsolicited plug, let's hit those stretch goals and see if we can get a playable Avisaurus!) is David Silva's "Beasts of the Mesozoic" dinosaur action figures. I don't want to take away from the fact hat these suckers are some of the best looking, most accurate dinosaur toys out there today (we all know how much I've complained about poorly designed dino toys in the past). I'm planning to buy one or two myself. But despite how awesome they are, I can't help but notice that the meme is strong with them.

The micro-tail mini-wing crew. I'm buying the Tsaagan.

Please note that I'm not saying these sorts of microraptor-tails are impossible or even unlikely in large dromaeosaurids. Given the diversity of feather styles we currently know about, some of these species certainly had something like this. But to give them all the exact same style tail which is a minority among known species is a misrepresentation. An honest, based on something not everyone knows is simply an old meme, but still, it's likely wrong to show the majority with microraptor-tails instead of archaeopteryx-tails.

The real kicker is that, according to the concept art (the final sculpt hasn't been produced yet), even Zhenyuanlong itself had a microraptor-tail! Luckily, it seems like this will be fixed, since the package art has the correct tail, and the figures are usually sculpted based on that. But just the fact that the microraptor-tail is so ingrained in the paleoart unconscious that it managed to sneak halfway through the design process for a species which definitively lacks it is a testament to the power these kinds of memes have over us, and how important it is to always second guess them.

It's too bad the artists involved in the BotM project didn't second guess why Zhenyuanlong is the only one with big wings. The description on the package says that Zhenyuanlong is "noteworthy for its long arm and tail feathers", but what it's really noteworthy for is being our only evidence regarding what the arm and tail feathers of medium-sized dromaeosaurids were actually like. It should be taken as the new standard, not the exception.