Bird stem evolved faster than other theropods

Figure 1. The evolution of birds as a consequence of miniaturization. Artist: Davide-Bonnadonna

Figure 1. The evolution of birds as a consequence of miniaturization. Artist: Davide-Bonnadonna. I think the last taxon on the right has been enlarged somewhat for clarity. See Figure 2. 

A new paper by Lee et al. (2014)
reported on their phylogenetic analysis of theropods employing 1549 characters. They found two drivers underlying the dinosaur-bird transition: 1) sustained miniaturization; and 2) the evolution of skeletal adaptations 4x faster than other dinosaurs.

They found that miniaturization facilitated the evolution of morphological novelties associated with small size: reorientation of the body mass; 2) increased aerial ability; and 3) paedomorphic skulls with enlarged eyes and brains along with a reduced snout and smaller teeth without serrations.

I heartily endorse this work.
It supports a paradigm that miniaturization that produces new clades. Cope’s Rule generally does not. We see similar miniaturization at the genesis of reptiles, amphibians, therapsids, mammals, dinosaurs, crocodylomorphs (together the archosaurs), pterosaurs, diapsids and several clades within each of these, like bats and pterodactyloid-grade pterosaurs. We knew for a long time that sustained miniaturization also produced birds. So that’s not news. It just has never been so well laid out before.

Figure 2. Sinocalliopteryx along with Aurornis and Archaeopteryx to scale. This illustration produced over a year ago, tells the same tale as the new Lee et al. paper, but without the great supporting details.

Figure 2. Sinocalliopteryx along with Aurornis and Archaeopteryx to scale. This illustration produced over a year ago, tells the same tale as the new Lee et al. paper, but without the great supporting details.

Lee et al. conclude: 
“Because size reduction, feather elaboration, paedomorphism, and other anatomical novelties permitted by small size all evolved in concert along the bird stem, identifying the primary driver of this sustained trend is probably impossible. It is likely that all traits influenced and provided the context for the evolution of others.” 

Actually not so impossible.
The authors make no mention of the fact that smaller taxa generally mature more quickly, breed more often and die sooner. In other words, generational turnover happens more quickly in smaller taxa, as everyone know. The rate of evolution over time is accelerated by the rate of reproduction over time (all other things being equal). That’s the primary driver. 

In the family tree of amniotes,
you see this all the time, not just in bird origins. Good to see this get the press it deserves.

References
Lee MSY, Cau A, Naish D and Dyke GJ 2014. Sustained miniaturization and anatomical innovation in the dinosaurian ancestors of birds.

 

Czerkas and Feduccia disconnect birds and dinos

Figure 1. Reconstruction of Scansoriopteryx with possible feather extent by Stephen Czerkas. Good thing that second branch or telephone wire is available for balance!

Figure 1. Reconstruction of Scansoriopteryx with possible feather extent by Stephen Czerkas. Good thing that second branch or telephone wire is available for balance!

A new paper by Czerkas and Feduccia
attempts to unlink birds with dinosaurs and to link birds with some unspecified archosaur by their reexamination of Scansoriopteryx, a tiny Chinese fossil of the Jurassic. Much has already been said about this paper — all negative.

Czerkas and Feduccia report the “absence of fundamental dinosaurian characteristics,” but do not do so with phylogenetic analysis, which would have nested their study subject somewhere else that they could support, but can’t. They seem stuck in a trees-down vs. ground up battle when plenty of ground-dwelling dinosaurs seem fully capable of climbing a tree by grappling or simply by running up a vertical trunk bipedally, as some modern birds do (any Dial reference below). Their illustration (Fig. 1) seems to say that whether bird or dinosaur or non-dinosaur, Scansoriopteryx was not capable of standing balanced on its (apparently splayed?) hind limbs, despite the fact that it’s forelimbs appear poorly designed for walking. They’ve been accused of LarryMartinizing and it seems they have indeed been doing so. For those interested, Larry Martin preferred to discuss individual characters rather than suites of characters of a sort used in phylogenetic analysis.

I can’t buy into their particular heresy.
There’s no support for it. We need to see details and analyses. And they need to present their best alternative candidate among the non-dinosaurian archosaurs out there as a sister to Scansoriopteryx. 

The irony here
is that the same sort and style of argumentation is being used to support a pterosaur/archosaur connection by the same set of paleontologists who support the dino/bird connection. By that I mean, they present no archosaurian candidates that more closely match pterosaurs than our own favorites: the lepidosaur, tritosaur, fenestrasaurs.

So, if you’re a finger pointing paleontologist, be careful. Don’t fall into  that same trap.

References
Czerkas SA and Feduccia A 2014. Jurassic archosaur is a non-dinosaurian bird, Journal of OrnithologyDOI: 10.1007/s10336-014-1098-9
Dial KP, Jackson BE and Segre P 2008.  A fundamental avian wing-stroke provides a new perspective on the evolution of flight. Nature (online 23 Jan 08)
Padian K and Dial KP 2005. Could the “Four Winged” Dinosaurs Fly?  Nature: 438:E3-5.
Dial KP, Randall R and Dial TR 2006. What use is half a wing in the evolution of flapping flight? BioScience 56: 437-445.
Tobalske BW and Dial KP 2007. Aerodynamics of wing-assisted incline running. J. Exp. Biol. 210:1742-1751.
Bundle MW and Dial KP  2003. Mechanics of wing-assisted incline running.  J. Exp. Biol., 206:4553-4564.
Dial KP 2003.  Evolution of avian locomotion: Correlates of body size, reproductive biology, flight style, development and the origin of flapping flight. Auk 120:941-952.
Dial KP 2003. Wing-assisted incline running and the evolution of flight.  Science 299:402-404.
Read more at: http://phys.org/news/2014-07-declassify-dinosaurs-great-great-grandparents-birds.html#jCp

 

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

A protobird lesson from Spitfire exhaust ports

Just a minor rant…

Figure 1. Sinornithosaurus running in pursuit of Microraptor. Click to see video. Neither of this animated creatures is using its forelimbs to generate thrust. What are they waiting for??

Figure 1. Click to see video. Sinornithosaurus running in pursuit of Microraptor. Neither of these animated creatures is using its forelimbs to generate thrust. What are they waiting for??

I notice in animated protobirds and dromaeosaurids that they keep the arms nearly motionless while running (here), even though feathered (Fig. 1). Basically only the legs are providing thrust. The wings are only providing drag via decoration.

Figure 2. Click to see video. Microraptor gliding without so much as even a little flapping. What is it waiting for??

Figure 2. Click to see video. Microraptor gliding without so much as even a little flapping. What is it waiting for??

Figure 2. Click to see video. Microraptor gliding without so much as even a little flapping. What is it waiting for??

Same goes for animated climbing and gliding, like this animation of Microraptor. Very little to no flapping is shown in some sort of attempt at showing a primitive form of flying = weak gliding. What would happen if these hot little dinosaurs did a little flapping? Or a lot of frantic flapping whether on the ground or in the air? So what if they don’t have big sterna!

Start with a behavior, the skeleton will follow.
At this point we all are thinking about WAIR (wing-assisted incline running) discovered by Kenneth Dial (2003). All you have to do is take away the incline. Keep those birdy’s flapping!

And you don’t even need a wing to start with
Earlier we noted that, like birds, protopterosaurs (like Cosesaurus, Fig. 3) also developed a stem-like, locked-down coracoid which enabled flapping and discouraged traditional quadrupedal locomotion. And Cosesaurus was a long way off from developing wings and flying. However, starting with this odd secondary sexual behavior bigger, thrust and lift producing forelimbs came quickly in pterosaurs and Longisquama once flapping commenced in earnest.

Figure 1. Cosesaurus flapping - fast. There should be a difference in the two speeds. If not, apologies. Also, there should be some bounce in the tail and neck, but that would involve more effort and physics.

Figure 3. Click to enlarge and animate. Cosesaurus flapping – generating feeble thrust with its frilled forelimbs held off the ground. Even a little extra thrust, as it turns out, can prove to be the winning edge in survival.

So why don’t dino animators add a little thrust 
to their running protobirds by adding a little frantic flapping of the forelimbs? After all, that’s how many (not all!) flying birds run (think chickens, sparrows and robins). And flapping wings still develop lift. So there’s no trade-off.

Well, modern bipedal lizards don’t flap. But then they all have a traditional coracoid and no arm frills. Many modern running birds, like the roadrunner and ostrich, don’t flap while they run. But chickens, ducks and songbirds do. So, the analog only goes so far.

What can the WWII Supermarine Spitfire tell us about thrust?

Figure 2. Hot gases firing out of exhaust ports on a Supermarine Spitfire add 70 hp at 300 mph

Figure 2. Hot gases firing out of exhaust ports on a Supermarine Spitfire added 70 hp at 300 mph. This concept ultimately became the modern jet engine producing all the thrust.

From Wikipedia: “In1938 the Spitfire was flown for the first time with ejector exhausts, developed for the Merlin by Rolls-Royce. With these it was found that the exhaust [gase]s [produced] 70 pounds of thrust, equivalent to about 70 hp at 300 mph.”

The takeaway
Even a little added thrust = added horsepower and added speed. And flapping had to start somewhere. Why not when feathers and a locked-down coracoid showed up? Start with a little, then move up to a lot. That’s the way evolution works.

References
Dial KP 2003. Wing-Assisted Incline Running and the Evolution of Flight (abstract). Science 299 (5605): 402–404. Bibcode:2003Sci…299..402D.doi:10.1126/science.1078237. PMID 12532020.

Wiki/origin of avian flight

Archaeoraptor – Chimaeras and Fakes – Part 3

It has been called a scandal, a hoax, an embarrassment and a fraud. If you’re already familiar with the story of Archaeoraptor, I’m not adding anything new here. Everyone already knows Archaeoraptor was a chimaera, another “complete” fossil put together from bits and pieces of several specimens. The references below, especially Wiki, tell the story.

Figure 1. At left Archaeoraptor as it appeared. At right Archaeraptor as it was assembled into a chimaera, from Rowe et al. 2001.

Figure 1. At left Archaeoraptor as it appeared. At right Archaeraptor as it was assembled into a chimaera, from Rowe et al. 2001.

Let’s not forget that the individual pieces still hold scientific value when separated.

This music video from the Offspring should be the final word.

References
Knevitt O. 2011. The 5 Greatest Palaeontology Hoaxes of all Time #3. Archaeoraptoronline here.
Rowe T, Ketcham RA, Denison C, Colbert M, Xu X, and Currie PJ 2001.
 Forensic palaeontology: The Archaeoraptor forgery. Nature 410 (6828) (March 29): 539-540. doi:10.1038/35069145. abstract here.
Online BBC video documentary here.

A paper written on fossil fakes is online here.

Wiki/Archaeoraptor

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