The “Microraptor also ate fish” thread on the dinosaur mailing list started a few days ago because the small highly-feathered four-winged Velociraptor-relative had been found with fish inside it. (In fact, I think now we’ve had a pretty representative sample of suitably-sized animals of the time found inside them, including a two-winged bird). It is good to have a fascinating channel through which to investigate theorising, even though as usual it was endless repeats of inexpert musing, but maybe it’s also good to repeat it again and again because if you throw enough mud at a wall for long enough, eventually some will stick!
Some say you can only decide if an animal, say Microraptor, could climb, if it had features like other climbing animals. The discussion this time revealed the endless search for crucial clues to be used as pegs on which to hang confident beliefs. Is that sound?
Well, though you kind of end up doing that, you mustn’t build the picture up brick by brick, piece of evidence by piece of fact – hoping to base a sound judgment on each crucial piece of evidence. First, don’t get hung up on individual bits. Experts in Go, a kind of ‘Chinese chess’, recommend players sit up straight and look at the whole board, rather than bending down and concentrating on a small area.
Second, try to use overall theories as your units of operation – be Theory Driven rather than Evidence Driven, i.e., see what happens when the theory hits the evidence, rather than trying to generate theories from evidence. That helps avoid getting hung up on whether something could live in trees if it had or didn’t have a certain feature. Also, thinking from the point of view of an overall theory will help you see more easily where an animal doesn’t have to do something (like getting up into a tree) in any particular way. If animals were only ever allowed to do things in a way some human had imagined, ducks would never be born in trees.
Also, remember: science is a two-step: Generate, and Test. You must allow your mind to run wild in the first phase. This is where a lot of people go wrong, because even their subconscious is hide-bound. It may even be a result of your culture, so beware. Extreme creativity requires an open mind, and some cultures just don’t do Open Mind. The only rule in the Generate phase is: There Are No Rules In The Generate Phase! If you forget that, you’ll never compete with evolution in creation because there are no real rules in Mutation and Recombination; strictures only arrive at the Selection stage, and whether an animal survives or not has as little to do with the process of its design and construction as the generate phase of science has to do with the test phase.
As usual, in the event of doubt, fall back on the basis of all theorising:- does a theory explain observations adequately, better than alternatives, (that is, ALL alternatives!), and in particular, better than its opposite?
In this case, is what we know of Microraptor’s body consistent with living, to some extent, in trees?
Living? Well, let’s pick some actions its tree life might entail. First, perching. Microraptor has very curved foot claws. Excellent for perching – certainly better than in ducks which sometimes perch, and at least as suitable as the feet of herons, frigate birds etc which nest in trees. (We note here that its feet are in fact unsuitable for extensive locomotion on the ground, according to Greg Paul who assures us in the thread that he’s checked out modern birds thoroughly, so we’ll remember to consider eliminating “living on the ground” soon.)
OK. So Microraptor could perch in trees absolutely fine. Note, we don’t have to compare its feet with anything else, so long as its feet could perch, even if they if did so in a completely new. In fact the long bony tail would be different from modern birds, but if pointed down when perching, it would keep the centre of gravity lower. This would make perching even easier in that sense, and perhaps making firm grasping unnecessary. This would be an example of an animal doing an old thing in a new way. But what else might its arboreal lifestyle entail? Well, what else do herons have that makes them arboreal?
Nothing. But they still nest in trees. One thing people seldom ask is whether Microraptor etc nested in trees. I suspect a good way to get at this is via the eggs, when we get them. “Theropod” eggs tend to be long and thin. Troodont and oviraptor-types eggs are. They were laid on the ground, perhaps in litter, with the more pointed end up. That’s not the case with modern birds, and apart from the very few birds that deposit the eggs under the surface in mounds, modern bird eggs have to be rolled. I suggest that’s an adaptation for tree-nesting, so if that’s true, it would be a good pointer. (Do ostrich fathers really turn all the eggs in their communal nests??) Do remember though, the ancestors of oviraptors and probably some troodonts had powered flight, and were certainly arboreal.
Let’s step back a bit. Why does everyone keep wanting to know if Microraptor was arboreal? “Why do they want to know?” is a good question, but a better question is “Could it fly?”. An even better question is why do they never want to believe it could, despite most of those who doubt it having no more understanding of flight than the average man in the street! Or worse still, the average bloke in the pub. If you refuse a priori even to consider that vodroms might have flown, you would not only insist on a climbing ability before accepting they could be arboreal, but you wouldn’t realise that the question of flying ability made the question of arboreality almost irrelevant.
Back we go to the basics again: Would powered flight explain stuff better than non-powered-flight alternatives? The “stuff” that needs explaining includes huge flight feathers on their hands and indeed feet, which in modern birds are ALWAYS used not just for lift but for generating thrust. Those “primary” feathers are not the only asymmetrical feathers on modern birds, which do have non-thrust generating asymmetrical feathers in the tail and away from the ends of the wing, but Microraptor’s primaries are not just asymmetrical, they’re PROPER primaries, and no messing.
No theory explains those primaries on Microraptor except the powered flight theory. Even the theories that purport to explain feathers as devices for brooding the young, or display, fail to explain the degree of asymmetry and also the very well bound together plate-like form of those primaries. They don’t just preserve well, they hardly ever dissociate into separate fibres even during fossilisation. They’re also pointed like buzzard (Buteo buteo) feathers, which unlike the round-tipped feathers of falcons, might be presumed to be avoiding damage from contact with the ground, by letting the pointed tip take the wear. (Falcons don’t wrestle as much on the ground, being specialised neck-biters. Presumably their prey, more often birds, are in any case less likely than a largish quadruped to keep running once grabbed. Owls have round-tipped feathers too, and tend to catch small prey that don’t require wrestling.)
Next bit of stuff to be explained: The strong arm bones, and in particular, the big area for attachment of the down-flap muscles on the humerus. It was said in the thread that there is no way to sufficiently understand the flight performance of Microraptors, and we can never know what their specific flight performance was because we can never know the actual size and cellular configuration of the flight muscles. But yup, we can know enough from those down-flap attachment areas. We can get the force on the wing bone in kilograms from it (and the moment – leverage – in kilogram metres). Open your copy of Dinosaurs of the Air and compare the puny forelimbs of the roadrunner with the forelimbs of a vodrom like Microraptor. If the roadrunner can fly, then see how much better Microraptor could. See if you can find a modern flightless bird with a humerus length half the distance between the shoulder and hip joint or longer: there ain’t one (and remember vodroms had a second set of wings too). If the biggest force applied to the humerus is for that down-flap, then the best explanation, i.e., the best theory, is that Microraptor had powered flight (because no other theory explains the arm features). (Do bear in mind that most conventional dromaeosaurs will also be able to pull very strongly with their arms to oppose their foot stab, so the down-flap might not be the only strong movement with the forelimbs.) Check out the sequence showing vodroms’ special vertical take-off ability I asked Greg to do in my book. Incidentally, many ducks, the dabblers – the ones people usually meet – can take off vertically from water; just as a gentleman is someone who can play the bagpipes but chooses not to, a dabbling duck is a bird that can take off vertically but often chooses not to.
But isn’t the powered flight theory refuted by their inability to raise their arms high above the shoulder? Some people, perhaps many, will tell you they are certain that a high up-flap was impossible for Microraptor, but they really don’t know. Check out Bambiraptor: some say it couldn’t manage a high up-flap either, but that’s not what the reconstructors of this thought:
Note how the arm bones seem designed to bend up and round the body, apparently in order to raise the forewings high despite the low shoulder. The low shoulder was needed because the predatory action, the toe stab, needed good forward (i.e. low) reach.
There is a widespread fallacy that a scientist doesn’t need to pay attention to a new idea until its supporters have made it impossible to ignore. How does it go? “The burden of proof is the responsibility of…” those with the new idea, or some such. That’s crap. How could making it their responsibility be derived from the basic essence of science?? The word “proof” hints at the problem – there’s no proof in natural science anyway; but obligations in science arise from issues of refutation, which puts the ball in the disputants’ court. In fact it’s the responsibility of all scientists to be aware of and value appropriately every interesting idea, or even every reasonable possibility, in their field. If there’s an obvious new idea that no-one has thought of, it’s even the responsibility of a scientist to come up with it themselves… but if someone’s nice enough to present you with a good new theory, then a good scientist must indeed investigate it. And although it’s good to challenge it properly by throwing every valid piece of evidence at it to be explained, it must not be assaulted with lies and pseudoscientific drivel. It must also not be ignored by anyone who claims to be a scientist. It is much worse to reject a good idea wrongly than not to reject a bad idea – because bad ideas will have plenty of opportunities to be refuted later, but good new ideas might well be pushed out of the picture for years if wrongly rejected the moment they appear.
You cannot claim to understand the rear wings of vodroms until you have tried to consider all the conceivable configurations for deploying the foot feathers. 90% of the images on the net of Microraptor in flight show the feathers pointing backwards. This tells us that 90% of the illustrators know nothing about flight because if the feathers pointed backwards they would not have been as asymmetric as they actually were. This configuration has been copied from the frankly moronic 2003 illustration in Nature. I don’t know anyone apart from myself who has even tried to consider more than one or two configurations. In the book I looked at six. Five of them would not allow powered flapping of the foot primary feathers. But. The. Sixth. DOES. Anyway, the nature of Microraptor’s foot primaries cannot be realistically explained as anything but a thrust generator, so I should have realised myself that it was always inevitable that there had to be a way for the rear primaries to be flapped, at least in vodroms (but probably not in any other types, even those with big leg feathers like Pedopenna, Anchiornis and Eosinopteryx). No illustration of Microraptor on the net shows its legs in that configuration – but a photo of a living bird does, and since that configuration is supposed to be even more impossible for living birds, we know what to think of its supposed impossibility in vodroms.
Kevin Padian said the other day that nobody was suggesting the rear wings of vodroms such as Microraptor, could be flapped. Who’s “nobody” Kevin? Never mind that Padian’s never said anything about the evolution of flight that was significant, new and right, he’s never said anything that even hinted at significant aerodynamic appreciation. If you don’t generate valid novelty, you’re the nobody in scientific research. Remember how he poo-poo’d the idea of feathers on “dinosaurs”? Maybe he made a few interesting observations on the microstructure of Cretaceous bird bones, but not understanding that all obligate bipeds, particularly well insulated ones, have to be warm-blooded (otherwise they’d lose balance when cold) minimised the value of his conclusions. I predicted, or chose to favour, the surprising but vindicated ideas that dinosaurs were basically feathered, that all dromaeosaurs had flying ancestors, and many, many more just as good. That makes me a somebody, and somebody better than Padian at theorising. It would be closer to the truth to say that if Padian made a judgement, you’d better bet on the opposite!
In the “Microraptor also ate fish” thread it was doubted that Microraptor could climb well in flight. I suspect that with thrust from two sets of wings it could climb like nothing on earth today. It was said that we’ll never know. Well, there’s lots we can understand well without certainty, and a rough but decent understanding of the flight of vodroms is going to be one of them. It was mentioned that its Jehol habitat largely consisted of dense forests; if so, short broad wings, particularly with the wing area in a tandem arrangement, would suit such birds. It’s pretty indisputable that with such a foot structure, and big foot feathers to boot, Microraptor could not chase prey on the ground. This leads to two important points:
* Are we being asked to believe that Microraptor was a specialist scavenger? Was there something else that actually killed the prey it ate? You could say the grounded forms like Sinosauropteryx were true predators, but we would certainly need something to fill the niche, and nothing that flew at the time seems more predatory than the vodroms. It may well be true that birds are much better at being specialist scavengers than mammals, but on the African savannah for example, there would also normally be reasonable densities of genuine specialist predators like lions and hyaenas, so we would expect a flying scavenger to be present where there was a flying predator. Perhaps even more tellingly, scavenged material is of relatively large animals, not small ones killed by other animals but which the “scavenger” can swallow whole. Bear in mind that specialist land scavengers that cannot locomote well on foot cannot be poor fliers. But if vodroms like Microraptor were specialist scavengers, why would true predators not have evolved from them?! This leads to the second point:
* Whatever its niche, why in the name of all that’s holy would Microraptor, if a weak flier, get stuck for tens of millions of years flying weakly?!! What could restrict it’s perfection of flight?! Vodroms probably lived for the full 80 million years of the Cretaceous. If long tail and rear wings restricted their flying ability, why did they NEVER dwindle?! Why did modern birds of prey never evolve during the Cretaceous with short tails and no rear wings?! The theory that Microraptor was a weak flier needs an awful lot of weird implications to be upheld, but with no apparent means of support.