Alpine Swifts and Pterosaurs

Alpine Swift (Tachymarptis melba) on the wing for 7 months at a time! Check out that wing shape. Remind you of anything prehistoric?

Alpine Swift (Tachymarptis melba) on the wing for 7 months at a time! Check out that wing shape. Remind you of anything prehistoric?

An interesting NatGeo post on the Alpine Swift (Tachymarptis melba) and its incredible but true 7 months (200 days) on the wing (Liechti et al. 2013) raised my curiosity about what sort of wing must such a bird have?

Turns out to have a very pterosaurian wing (short chord version) in ventral view. Nat Geo reports, Their long wings make them fast and manoeuvrable, allowing them to scythe through the air in search of small insects and other “aerial plankton”.

And why do they fly continuously? Again, Liechti has speculations rather than answers. They may exploit food sources that other birds can’t touch, avoid predators by flying through the night, or stay beyond the reach of parasites like malarial mosquitoes. “These aren’t very convincing,” he admits, “but for sure, there’s a cost to staying in the air, so there must be a benefit.”

Swifts are apodids, famous for their tiny feet (they don’t perch that often). That takes us to the pterosaurs with tiny feet and spindly legs, the ornithocheirids (Fig. 2, 3).

Worth comparing for wing shape and foot size.
Evidently these large pterosaurs were likewise rarely grounded, based on their tiny feet and giant wings, especially compared to other pterosaurs.

Figure 2. The ornithocheirid pterosaur, Arthurdactylus. Note the tiny size of its feet.

Figure 2. The ornithocheirid pterosaur, Arthurdactylus. Note the tiny size of its feet and the huge wings. Like a swift, this pterosaur could have slept while on the wing. The spindly fingers were no good for grappling tree trunks.

Awkward on the ground.
Graceful in the air. This is the reason why the ornithocheirid humerus is so much larger than the femur – not the forelimb launch hypothesis! They put everything into their wings, which transport them to food. Their legs simply enable them to walk out of their eggs.

Figure 2. Arthurdactylus in dorsal view while flying. Note the knife-like wing shape,  that could be maneuvered, like that of a sail plane or swift.

Figure 2. Arthurdactylus in dorsal view while flying. Note the knife-like wing shape, that could be maneuvered, like that of a sail plane or swift. Wings back = less drag, greater speed.

Basically the pterosaur wing in ornithocheirds is a tapering cone, with a large diameter proximally and a tiny diameter distally. This has proved to be a very strong structure from outstretched traffic lights to fishing rods.

Outstretched to swept back
As in swifts, the wings of pterosaurs could have maneuvered in flight from strictly lateral to backswept. Each configuration has their own use, advantage and disadvantage.

References
Liechti, Witvliet, Weber & Bachler 2013. First evidence of a 200-day non-stop flight in a bird. Nature Communications.http://dx.doi.org/10.1038/ncomms3554

The unexpected bipedal/marine connection

Several times in the evolution of reptiles bipedal forms have phylogenetically preceded marine forms. Yes, marine forms. It’s bizarre, but true.

Here’s the list, more or less. Did I miss any?

Huehuecuetzpalli (bipedal capable) > Dinocephalosaurus (marine)
Huehuecuetzpalli, a small speedy lizard with short fore limbs and long hind limbs evolves to become Dinocephalosaurus, a giant long-necked sit-and-wait predator via Macrocnemus, something in between.

Langobardisaurus (biped) > Tanystropheus (marine)
Langobardisaurus, a small long-necked strider evolves to become Tanystropheus, a giant stand-and-wait marine predator.

Eudibamus (biped) > Claudiosaurus (marine)
Eudibamus, a small lizard-like diapsid with a long neck and long hind limbs evolves to become Claudiosaurus, a long-necked marine undulating marine predator of tiny prey. Thereafter descendants evolve to become ichthyosaurs and plesiosaurs.

Varanus (biped while fighting) > Mosasaurus (marine)
Okay, so only certain varanids only go bipedal when fighting, even so mosasaurs are giant and marine.

Scleromochlus & Terrestrisuchus (bipeds) > Metriorhynchus (marine)
Scerlomochlus, and Terrestrisuchus, tiny long-legged basal crocs evolve to become large short-paddled marine crocs, like

Storks (biped) > Penguins (marine)
Flying bipeds evolve to fly underwater.

Australopithecines (biped) > Humans (Homo, marine capable)
(grassland roamers evolve to become able to swim)

Evidently it all comes down to 
Conscious control of breathing — if you want to become a marine animal you have to hold your breath.

Not sure what the bipedal connection is with reptiles, because lots of marine reptiles never had a bipedal phase. I just wanted to throw the idea out there.

More on Humans:
Anthropologist Elaine Morgan on TED talks about the origin of bipedal humans from aquatic apes here. Step-by-step: Apes all walk bipedally when they cross streams. For insulation humans have fat migration to a subdermal position, that’s why obesity is possible for humans, not for apes. The nostrils open ventrally, keeping water out by air pressue in humans. Ape nostrils don’t keep out water, except for the proboscis monkey (the most aquatic of primates).  Ability to speak comes by way of the conscious control of their breath, according to Morgan.

Late Cretaceous pterosaurs, penguins, storks and falcons

A 2006 paper (Slack et al.) on earliest Paleocene penguin (Waimanu manneringi) fossils finds sheds light on early bird diversification and possible decline of the pterosaurs (reduction to only large taxa).

Penguins and storks
According to Slack et al., penguins and storks nest together closer than loons and albatross + petrel. And they must have diversified at 67.1 mya, prior to the K/T extinction.

Falcons and pterosaurs
An earlier diversification, 77.2 mya marked the splitting of the falconiformes from the sea birds (including the above listed taxa). That means falcons or protofalcons were soaring over Late Cretaceous skies. Noting trends for ever larger pterosaurs and the absence  smaller pterosaurs in the Late Cretaceous, the authors report, “Kim et al. (2003) offer the interpretation that pterosaurs might have fed on small birds—equally plausible to us, however, is that the raptors (Falconiformes) could have preyed on young pterosaurs.”

Never heard that one before. Of course, if a predator eats all of its prey, the predator also dies. So, improbable, but interesting.

References
Kim CB, Huh M, Cheong CS, Lockley MG and Chang HW 2003. Age of the pterosaur and web-footed bird tracks associated with dinosaur footprints from South Korea. Island Arc 12:125–131.
Slack KE, Jones CM, Ando T Harrison GL, Fordyce RE Arnason U and  Penny D 2006. Early Penguin Fossils, Plus Mitochondrial Genomes, Calibrate Avian Evolution. Mol. Biol. Evol. 23(6):1144–1155.

How Birds Got Their Wings

A recent article, “How Birds Got Their Wings,” also here, here and here describe work by Dececchi and Larsson (2013) that noted scaling of forelimb vs hind limb took a big turn with Archaeopteryx and kin (Fig. 1). They note, as forelimbs lengthened, they became long enough to serve as an airfoil, allowing for the evolution of powered flight. Shorter legs would have aided in reducing drag during flight — the reason modern birds tuck their legs as they fly — and also in perching and moving about on small branches in trees.

That’s all well and good, but its not the key. It’s one step following the key.
The key is flapping. That’s a behavior that definitely leads to flight. Having long forelimbs vs. hind limbs is also found in primates, chalicotheres and sloths. They don’t fly. Even the “flying lemur” Cynocephalus had long arms. All it can do is glide because it doesn’t flap.

Figure 2. Cosesaurus running and flapping - slow.

Figure 1. Click to animate. Cosesaurus running and flapping – slow.

The key to flapping is a locked down coracoid.
As we learned earlier with Cosesaurus (Fig. 1), a locked down coracoid is one thing pterosaurs and birds share. Cosesaurus had fibers trailing its forelimbs (Ellenberger 1993, Peters 2011) but its forelimbs were too short to fly. Nevertheless, it could flap because it had a locked down coracoid. And that was a secondary sexual trait (behavior) that led to more of the same in three distinct directions in Sharovipteryx, Longisquama and basal pterosaurs.

Taxa in the lineage of birds.

Figure 2. Taxa in the lineage of birds. From top to bottom: Tawa, Juravenator, Sinocalliopteryx, Archaeopteryx, Cathayornis, Sinornithes plus enlarged skulls. Note the coracoid becomes taller and fixed in Archaeopteryx.

Other dinosaurs
with long forelimbs and a tall, narrow, locked down coracoid include oviraptorids, dromaeosaurids, alvarezaurs and birds all taxa that phylogenetically follow Archaeopteryx.

And bats?
They have a locked down tall clavicle that serves the same function. We don’t know when they started flapping because the closest known fossils of prebats are all skull material only.

Reference
Dececchi TA and,  Larsson HCE 2013. Body and Limb Size Dissociation at the Origin of Birds: Uncoupling Allometric Constraints Across a Macroevolutionary Transition. Evolution 67(9):2741 DOI:10.1111/evo.12150

What?? No feathers on velociraptors?

Figure 1. Inside cover illustration spread for "Raptors, the Nastiest Dinosaurs" by Don Lessem, illustrated by David Peters. Don asked for a "no feathers dinosaur" so that's what he got. Don't blame the artist. I tried to persuade. Utahraptor is the big dromaeosaur here.

Figure 1. Inside cover illustration spread for “Raptors, the Nastiest Dinosaurs” by Don Lessem (1996), illustrated by yours truly, David Peters. Don asked for a “no feathers dinosaur” so that’s what he got. Don’t blame the artist. I tried to dissuade. Utahraptor is the big dromaeosaur here.

This post was inspired
by a blog and Flickerstream I ran across here and here that bemoaned the fact that my 1996 dromaeosaurids / velociraptors (Fig. 1) in “Raptors – The Nastiest Dinosaurs” did not have feathers, but did have propatagia.

Guys, I tried to add feathers, as I had done several years earlier (1989) to my own velociraptors in Gallery of Dinosaurs (Fig. 2). However, author Don Lessem insisted that no feathers appear in his book. I tried to dissuade, but was vetoed. After all, he is the author. And that was then. I’m sure Dino Don has come around to new thinking since then.

See how difficult it is to promote a new idea supported by data? Even an expert like Don Lessem balked back in 1995-6.

Figure 2. Feathered Deinonychus from A Gallery of Dinosaurs by David Peters.

Figure 2. Feathered Deinonychus from A Gallery of Dinosaurs by yours truly, David Peters. (1989). Click to enlarge.

So, there is a backstory,
as there is with other controversial aspects of my work. At present the backstory and trashed ideas are not as important as the current work. Science marches on and new data keeps coming in. So let’s stay with the current wave. If you see any other problems with my  tracings or identifications, please let me know of those issues.

References
These are kids books, not academic journals!
“A Gallery of Dinosaurs” is online here.

Jason Brougham Deinonychus skeleton model

This is excellent!

Figure 1. Deinonychus skeleton model by Jason Brougham. Click to learn more.

Figure 1. Deinonychus skeleton model by Jason Brougham. Click to learn more.

And if you haven’t become acquainted with artist/scientist, Jason Brougham, I hope you do so now. Incredible and accurate detail, dynamic pose and very birdy.

Lateral view of Deinonychus by Jason Brougham.

Figure 2. Lateral view of Deinonychus by Jason Brougham.

It’s not very often that a skeleton seems this alive.

See more at jasonbrougham.com

Aurornis xui – A New Bird-like Dinosaur with Feathers

“A birdlike fossil that dates to roughly 155 million years ago is ruffling the feathers of some paleontologists. At issue is whether the fossil is a dinosaur, an early bird or something in between,” Rachel Ehrenberg of Science News wrote. “This new animal is the most primitive bird in the world,” says paleontologist Pascal Godefroit of the Royal Belgian Institute of Natural Sciences.

And further down, Ehrenberg writes, “Not everyone agrees with Godefroit’s interpretation. ‘This is very birdlike, but it is not yet a bird,’ says paleontologist Luis Chiappe of the Natural History Museum of Los Angeles County.”

The name of the new dinosaur with feathers is Aurornis xui. Twice as tall as Archaeopteryx (Fig. 1) and three times as long, Aurornis preceded Archaeopteryx by 10 million years and lived in China.  Lacking large feathers, Aurornis did not fly, but would have been a speedy runner. Aurornis phylogenetically precedes Archaeopteryx and all other birds. So is it a bird? Or pre-bird?

Who is right? 
Here is the traced specimen. The fossil appears here online. The coracoids are hard to see as they overlap one another in situ, but they appear to be strut-like. If so, Aurornis flapped, not that that matters…but if Archaeopteryx was a poor flyer, than Aurornis didn’t have a chance.

Aurornis xui in situ and reconstructed alongside Archaeopteryx to the same scale. Click to enlarge.

Figure 1. Aurornis xui in situ and reconstructed alongside Archaeopteryx to the same scale. Click to enlarge. Aurornis is a larger animal, but with a skull and pelvis not much larger than in Archaeopteryx.

Bird Ancestor? 
Earlier we looked at taxa that phylogenetically preceded Archaeopteryx (all larger) and several taxa that phylogenetically succeeded Archaeopteryx (all smaller, but later forms grew larger). Aurornis was too large to fly. It did not have flight feathers or tail tip feathers. Archaeopteryx was able to fly feebly with large flight feathers and tail tip feathers on a smaller body.

Everyone wants to find the first, the biggest, the best, etc. 
It comes down to how paleontologists and ornithologists define what a bird is. According to Luis Chiappe of the Natural History Museum of Los Angeles County quoted in LiveScience“Traditionally, we have defined birds as things like Archaeopteryx and closer to things like modern birds. If you stick to the definition, this thing is not the earliest known bird.” Even so, it is a very interesting animal that “still helps us understand better the origin of birds,” Chiappe said.

Indeed
Aurornis is a wonderful new taxon that gives greater insight into the origin of birds, but it is not one by definition.

References
Godefroit P, Cau A, Hu D-Y, Escuillié  F, Wu W-H and Dyke G 2013. A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds. Nature .doi:10.1038/nature12168.

wiki/Aurornis