Chicken skull colorized

Figure 1. Chicken skull (Gallus gallus) with fused and semi-fused skull bones colorized. Postorbital = orange. Squamosal = lavender. Lacrimal = brown. Prefrontal = purple. Note mid portion of jugal (light blue) is unossified.

Figure 1. Chicken skull (Gallus gallus) with fused and semi-fused skull bones colorized. Postorbital = orange. Squamosal = lavender. Lacrimal = brown. Prefrontal = purple. Quadrate = red. Note mid portion of jugal (light blue) is unossified.

The chicken (Gallus gallus) was recently added to the large reptile tree (still not updated). Like most birds several skull bones fuse in adults. Other bones are greatly reduced, losing their old dinosaurian looks. The antorbital fenestra is confluent with the orbit. The middle of the ascending process of the jugal is unossified. Like mammals, birds have a greatly enlarged brain and cranium and that shifts those bones about a bit.

This is an example of how DGS (digital graphic segregation) can help illustrate a very common taxon.

 

 

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

 

Archaeopteryx vs pterosaurs: speciation? or variation? Plus an interclavicle question.

I read this today on Wiki/Archaeopteryx: “Recently, it has been argued that all the specimens belong to the same species, however, significant differences exist among the specimens. In particular, the Munich, Eichstätt, Solnhofen, and Thermopolis specimens differ from the London, Berlin, and Haarlem specimens in being smaller or much larger, having different finger proportions, having more slender snouts lined with forward-pointing teeth, and possible presence of a sternum. These differences are as large as or larger than the differences seen today between adults of different bird species, however, it also is possible that these differences could be explained by different ages of the living birds.”

Figure 1. Archaeopteryx size graphic from Wikipedia.

Figure 1. Archaeopteryx size graphic from Wikipedia created by Matt Martyniuk. Very informative. Size matters!

If that is all that separates one Archaeopteryx from another, it really is time to take another look at pterosaurs.
There are so many Pterodactylus, Pteranodon, Rhamphorhynchus, Germanodactylus, Darwinopterus, etc. etc. etc. that given the same splitting/lumping parameters someone is going to have to come up with a slew of new names.

The problem is, who has the authority?
And if anyone does have the authority, who will recognize, follow and support that authority? That time may have already passed when there were fewer workers setting standards in paleontology. Back in the 1970s the work by Wellnhofer on Solnhofen pterodactyloids (1970) and non-pterodactlyloids (1975) is encyclopedic and widely cited. I’m not sure that someone else in the present day such authority because the professional vacuum that existed then is not present today.

The answer is:
A grad student for his/her PhD dissertation might have no authority, but that doesn’t matter. These least likely candidates are incredibly talented, but largely lacking in experience, which sometimes works to their advantage. And they are always looking for large projects to tackle. This task is enormous and will involve a lifetime of study and restudy. So, maybe the parameters are not narrow enough for a decent thesis.

I suppose lumpers will always fight splitters, and vice versa, like two parents trying to name one child.

>>>>>>>>>

On a side note:
Did early amniotes and their outgroups fuse the coracoid and interclavicle? I am having a difficult time locating coracoids, at the same time that the interclavicle appears to be “amply endowed,” if you know what I mean. Here’s an example in Brouffia: (Fig. 2) and Gephyrostegus (Fig. 3). Please send literature refs if you have them.

Figure 2. Brouffia. Is the coracoid fused to the over robust interclavicle, as it would seem? Lit refs please!

Figure 2. Brouffia. Is the coracoid fused to the over robust interclavicle, as it would seem? Lit refs please!

Figure 3. This Gephyrostegus interclavicle looks suspiciously tripartite. Are coracoids fused here?

Figure 3. This Gephyrostegus interclavicle looks suspiciously tripartite. Are coracoids fused here?

Tracing fossil photos goes mainstream in 2014

DGS is going mainstream
A new paper by Chiappe et al. 2014, forsakes time honored and inaccurate pencil tracings with a camera lucida (basically a prism) and goes straight to the camera, scanner and mouse in their portrayal of the new Hongshanornis specimen. This is a great example of DGS or digital graphic segregation.

Figure 1. From Chiappe et al. 2014 showing the fossil (at right) and the digital tracing (at left).

Figure 1. From Chiappe et al. 2014 showing the fossil (at right) and the digital tracing (at left). Here’s a professional paleontologist using a technique for which I was once and continue to be derided.

There is value in this technique, even when the bones are mere impressions, and the soft tissue is ephemeral, as they appear here. (Figs. 1, 2). The technique is especially helpful in two-dimensional crushed fossils, like Hongshanornis.

Figure 2. The two images of Hongshanornis superimposed to show the exactness this tracing technique produces, plus color, plus enlargements, etc. etc.

Figure 2. The two images of Hongshanornis superimposed to show the exactness this tracing technique produces, plus color, plus enlargements, etc. etc.

Many were the times
when I tried to match a published drawing with a published photo and found I had to warp or distort one or the other to make them match. A long lens from a distance at right angles to the plane of the specimen minimizes distortion and key-stoning (perspective problems). This photography technique combined with scanning such a photo and tracing it on screen with a mouse makes that problem go away.

The next step, of course, is to use the digital tracings to create a very accurate reconstruction.

References
Chiappe L, Bo Z, O’Connor J, Chunling G, Xuri W, Habib M, Marguan-Lobon J, Qingjin M and  Xiaodong C 2014. A new specimen of the Early Cretaceous birdHongshanornis longicresta: insights into the aerodynamics and diet of a basal ornithuromorphPeerJ. 2:e234; DOI 10.7717/peerj.234

wiki/Hongshanornis

Triassic? No, Eocene Bird Tracks: How to Fix a Mistake in “Nature”

The whole point of this post is to show that sometimes scientists AND referees make mistakes. This one (see below) the authors corrected themselves, likely after catching hell from colleagues for the last 11 years. The referees are probably glad to retain their anonymity.

Figure 1. Bird tracks originally considered Latest Triassic, now considered Eocene, from Argentina.

Figure 1. Bird tracks originally considered Latest Triassic, now considered Eocene, from Argentina.

It all started a decade ago
when Melchor, De Valais and Genise (2002) reported very bird-like tracks in Latest Triassic sediments in Argentina. This was deemed worthy of the academic journal Nature because, if valid, this would have pushed the origin of birds, or bird-like dinosaurs, back from the Latest Jurassic to the Latest Triassic. A very hot topic! Respected paleontologist referees gave this the green light and it was published.

However, recently this paper was retracted.

Here’s the apologetic abstract
from Melchor, De Valais and Genise (2013) 

“Bird-like tracks from northwest Argentina have been reported as being of Late Triassic age. They were attributed to an unknown group of theropods showing some avian characters. However, we believe that these tracks are of Late Eocene age on the basis of a new weighted mean 206Pb/238U date (isotope dilution–thermal ionization mass spectrometry method) on zircons from a tuff bed in the sedimentary succession containing the fossil tracks. In consequence, the mentioned tracks are assigned to birds and its occurrence matches the known fossil record of Aves.”

Hopefully apologies have been accepted worldwide.
These three “came clean” and made their mistake known and I’m sure all three will continue to make important contributions to paleontology.

Unfortunately
Some scientists do not accept apologies or corrections. Some rifle through trash for rejected ideas so they can pillory others. Some scientist can not accept their own mistakes. Some scientists reject solutions to problems by labeling them, “highly idiosyncratic (= a mode of behavior or way of thought peculiar to an individual)” just because they have new ideas not preciously considered by others. These are the scientists who are gumming up the works.

There are several papers that have been rejected by referees clinging to the status quo that solve several enigmas and clear up several mysteries using established scientific methods. Several of those rejections from referees who are “gumming up the works” provided the reason for this blog and reptileevolution.com.

References
Melchor RN, De Valais S and Genise JF 2002. Bird-like fossil footprints from the Late Triassic. Nature 417, 936–938 (2002)
Melchor RN, De Valais S and Genise JF 2013. A late Eocene date for Late Triassic bird tracks. Nature 495, E1–E2 (21 March 2013) doi:10.1038/nature11931

Something about Turkeys on Thanksgiving

Happy Thanksgiving (America).
I encourage my readers, if they have not already done so, to check out My Life as a Turkey online at PBS (Fig. 1, click here). They’re curious, affectionate, loyal and when they hit puberty all hell can break loose. They’re beset by enemies and they learn to control their enemies. They are hit with disease and they mourn their losses. Some are independent. Others, from the same brood, seek touch. Watch them learn to fly, loose their cuteness, play with the mammals and, in the end, go out on their own.

Click to go to online video at PBS/Nature. My Life as a Turkey explores the ontogeny of these little dinosaurs as thoroughly as I've ever seen.

Click to go to online video at PBS/Nature. My Life as a Turkey explores the ontogeny of these little dinosaurs as thoroughly as I’ve ever seen.