Couldn’t upload pictures for a few hours today, upload system down, thus the post is a bit late. Sorry!
Today, let’s have a short look at the diversity of extant dinosaurs. OK, admittedly all I can offer is theropods, and avialae, or more closely defined Aves at that. And that group has gone through a ridiculous miniaturization in the Jurassic, because of their adaptation to flight. The most obvious results are the loss of the bony tail, a huge central nervous system (they do have to process a huge lot of visual data very quickly, otherwise they’d fly right into things), the loss of the left aortic arch (us mammals retained it and lost the right one, and what a striking coincidence that mammals also underwent miniaturization during the Jurassic?), the loss of one ovary (in most families), and the development of a ridiculously large sternum with a keel on the midline and accordingly huge pectoral muscles.
Nah, that’s not bird inventions, that’s all stuff more basal dinosaurs already had.
*(Phil Manning pointed out at the Bonn conference, I should better say “archosaur-grade highly subdivided unidirectional lung”)
OK, enough text, here come the pics:
Andean condor (Vultur gryphus), telling us about the last llama (not lama!) carcass it found (or rather, imagined to have found). The condor has the largest wingspan among living land dinosaurs.
House Sparrows (Passer domesticus), using the condor aviary’s mesh fence as a resting place. Seeing the two next to each other is pretty impressive. Sparrows are far from being the smallest birds, even in Europe. Still, they are extremely common, and thus the smallest birds most people see regularly. The Bee Hummingbird (Mellisuga helenae) is the smallest bird, at a weight of 1.8 g. That’s a bit more than 0.01 per mill of the 154 kg for the largest ostriches (says wikipedia).
oh yeah, ostriches:
and thus we have three highly different main modes of locomotion in birds: terrestrial walking and running in ostriches, soaring in the condor, and flapping flight in the sparrow. Let’s add another one, surface swimming by paddling
A couple of Mandarin ducks (Aix galericulata) sleeping. Although I took this picture in the Berlin Zoo, this beautiful member of the dabbling ducks is pretty common in Berlin, with over 9,000 breeding pairs. That’s a higher number than in the wild in Japan and China! Dabbling ducks rest high in the water, and feed mainly on the surface or by dabbling. The other large behavioral group are the diving ducks, but the taxonomy of geese and ducks is something to have nightmares about, so I’ll not dive into it at all.
One thing that varies a lot in birds is overall proportions and neck length.
A Black swan (Cygnus atratus). Compare neck length to the sparrow. Many birds have fairly long necks, but hold them in a strong S-curve (see this budgie sketch in the epic “Necks lie!” post at SVPOW), but they are no match for many birds living on or in water, and quite a large number of other birds. As a general pattern, good maneuverable fliers have shorter necks, but neck length also correlates with leg length (you wanna get your beak to the ground without sitting down, maybe?).
Well, I could go on for days posting pictures of birds that are non-ordinary songbirds. I’ll stop now with one of the oddest groups: penguins!
Humboldt penguins (Spheniscus humboldti) about to enter the water.
All pictures taken at the Berlin zoos.
Well, no. That would be changing terminology to match a hypothesis. There’s reason to think that maybe something like an avian lung was in place at the base of Archosauria, but:
1. That’s hardly a slam-dunk
2. Even assuming basal archosaurs did have something recognisably different from a typical “reptile” lung, it probably had a long way to go to the full avian condition.
3. If it later turns out to have originated yet futher back, would we re-rename it as the archosauropmorph lung?
4. Only be naming this style of lung after something extant (i.e. something that we can dissect in soft tissue) can we know what, precisely, we mean by it.
So I think Phil’s idea is a misguided one.
I think Phil has a point: Steve Perry’s research and the recent paper on flow-through ventilation in crocs strongly suggest that a highly complex lung did evolve much earlier. “Avian” sounds like “as in extant birds” – but that’s not the important issue! We do not want so say “precisely like a bird lung”. The point is that the lungs were “in principle like bird lungs”.
So while I do see your points, there’s a bit more to it, including the issue of science communication.
“Strongly suggest” is not solid enough to merit a change in nomenclature. You’d think this lesson would have been learned with the constant flux of clade-names.
“Avian” does mean “as in extant birds”. Because that is the standard we are comparing with. If I say “sauropods had an avian lung”, I am telling you something specific. If I say “sauropds had an archosaur lung”, I am saying nothing.
And you may be telling me something wrong: sauropods may not have had an exactly avian lung.
Yes. But at least you know what I am trying to tell you, and can make an objective assessment of whether I am right or not. If I say “archosaur-style lung”, I could mean anything from what birds have, what crocs have, what alligators have (which may not be the same), to some hypothesized ancestral state … which by the way no-one has yet even tried to reconstruct.
Much better to base terminology on actual things.
And if you drop the strawman argument (“archosaur-style lung”) and address the real term: “archosaur-grade highly subdivided unidirectional lung”, then that’s all irrelevant, because the (too) long term Phil used is in fact a description of the key functional characters, with “archosaur” thrown in for clarification.
Although many extinct dinosaur clades had beaks, aren’t those homologous with modern birds essentially a neornithine (okay, probably ornithurine) invention?
I won’t stick my neck out on that – likely yes, but who knows for sure? Remember the very precarious position of Archaeopterxy – I do not believe any cladistic analysis at the bird base right now. Too much uncertainty, too many possible convergencies. And too many taxa showing up that have us all go “oooohhhh! Well I never…”
i’m interested about the loss of the left aortic arch, i didn’t knew it was specific to modern birds (aves) as opposed to being a general feature of avemetatarsalia… how do we know this?? is there a fossil heart of a non-avian theropod that i don’t know of? ( i’ve seen crazyer cases of soft tissue-fossilisation).
and in what respect is it an adaptation to flight? (i geuss it is because you quote it along with the big brain/big eyes, big sternal plate and pectorals, loss of bony tail, ect… wich are all flight adaptations).
PS: diomeda albatrosses have the biggest wingspan of extant birds, with verified valuse of up to 3.6m, and even (according to wikipedia) old reports of 4.3m and even 5m+ (WTF?!) for D.exulans although that does sounds to me like a fancy sailor’s exaggeration.
but then again i agree that Vultur Gryphus have probably the largest wing area; being a pasive soarer as opposed to a dynamic soarer. ALTHOUGH, some of the largest species of Pelecanus are absolutely humongous on their own (wingspan slightly over 3m just like the andean condor) AND have broad wings too so i don’t know…
indeed, forgot the LAND in land bird. thanx.
as for the aortic loss: it is all soft tissues, so I guess we will never know for sure. It is, however, logically connected to miniaturization, which itself is needed for flight, because it allows the use of a smaller volume of soft tissues to perform the same function – albeit at a loss of redundancy which carries its own risk.
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