Jurassic birds took off from the ground – SVP abstracts 2016

Everyone knows:
Ground up hypothesis – 

implies and includes flapping, always has. Birds flap, always have, at least since the elongation and locking down of the coracoid in ancestral troodontids.

Trees down hypothesis –
has always implied gliding. Gliders don’t flap, never have.

But
baby birds dropping out of trees always flap. It’s what they do. But that fact is often ignored in bird origin videos.

And, as everyone knows by now…
young birds with pre-violant wings flap them like crazy when climbing bipedally — even vertical tree trunks… also something several animated bird origin videos ignore, perhaps because of one glaring opposite extant example: the young wet hoatzin that struggles to climb with all four limbs.

With that preamble…Habib et al. 2016 provide us
a hypothesis on the origin of bird flight that appears to ignore trees and experimental work with pre-volant birds and goes straight to take-off from flat ground. Is that okay?

From the abstract:
“Many small non-avian theropods possessed well-developed feathered forelimbs, but questions remain of when powered flight evolved and whether it occured more than once within Maniraptora. Here, using a first principles modeling approach, we explore these questions and attempt to determine in which taxa takeoff and powered flight was possible. Takeoff is here defined as a combination of both the hindlimb driving the ballistic launch phase, and the wing-based propulsion (climb out). [1]

“Microraptor, Rahonavis, [2] and all avian specimens generated sufficient velocity during leaping or running for takeoff. We re-ran our analysis factoring in life history changes that can alter the flight capability in extant avians, such as egg retention and molting, to examine how these would influence take off capacity. Of the two, molting shows the most significant effects.

“When these results are coupled with work detailing the lack of arboreal features among non-avian maniraptorans and early birds, they support the hypothesis that birds achieved flight without a gliding intermediary step, something perhaps unique among volant tetrapod clades.” [3] [4] [5]

Figure 2. Cosesaurus running and flapping - slow.

Figure 1. Cosesaurus running and flapping – slow.

Notes

  1. Interesting that Habib et al. ignore the presence of trees, which are key to Dial’s hypothesis (updated in Heers et al. 2016)  and opts to go straight from ground to air. That kind of ignores key work, doesn’t it? You might recall that Dr. Habib became famous as the author of the infamous but popular forelimb quad launch hypothesis for pterosaurs.
  2.  Microraptor and Rahonavis are NOT in the lineage of birds in the LRT, but both show how widespread long feathered wings were in Theropoda. The former has elongate coracoids by convergence. The latter does not preserve coracoids, fingers or feathers, but does have the long forearm that might imply bird-like proportions for missing bones… or not.
  3. Apparently Habib et al. assume that pterosaurs and bats originated as gliders when present largely ignored evidence indicates exactly the opposite. Cosesaurus (Fig. 1) was a pterosaur precursor with elongate coracoids, unable to fly, but able to flap. Bats rarely glide, so it is unlikely that they did so primitively. Lacking coracoids, bats employ elongate clavicles to anchor flight muscles.
  4. Okay, so remember the preamble (above) about gliding and trees. When Habib et al. bring up ‘a gliding intermediary step‘, they are implying the presence of trees (high places) in competing and validated-by-experiment hypotheses for the origin of bird flight  — which they are ignoring. They also ignore the fact that baby birds don’t glide when they fall out of trees. They flap like their lives depend upon it. I find those omissions odd, but its not the first time pertinent work has been ignored in paleontology.
  5. In the LRT Xiaotingia (Fig. 2) is the most primitive bird-like troodontid to have elongate coracoids and so may have been the first flapper in the lineage.
Figure 1. Xiaotingia with new pectoral interpretation. See figure 3 for new tracing.

Figure 2. Xiaotingia with new pectoral interpretation.

References
Habib M, Dececchi A, Dufaault D and Larsson HC 2016. Up, up and away: terrestrial launching in theropods. Abstract from the 2016 meeting of the Society of Vertebrate Paleontology.
Heers AM, Baier DB, Jackson BE & Dial  KP 2016. 
Flapping before Flight: High Resolution, Three-Dimensional Skeletal Kinematics of Wings and Legs during Avian Development. PLoS ONE 11(4): e0153446. doi:10.1371/journal.pone.0153446
http: // journals.plos.org/plosone/article?id=10.1371/journal.pone.0153446

YouTube video showing birds running up tree trunks while flapping with nonviolent wings

ScienceNews online promo.

Paravian phylogeny revisited – SVP abstracts 2016

Pei et al. 2016
reveal the origin of birds in a new phylogenetic analysis. Some aspects confirm earlier recoveries in the large reptile tree (LRT) made about a year ago. Not sure about other aspects given the brevity of the abstract and lack of cladogram imagery.

From the Pei et al. 2016 abstract
“Paraves are theropod dinosaurs comprising of living and fossil birds and their closest fossil relatives, the dromaeosaurid and troodontid dinosaurs. Traditionally, birds have been recovered as the sister group to Deinonychosauria, the clade made up of the two
subclades Dromaeosauridae and Troodontidae. However, spectacular Late Jurassic paravian fossils discovered from northeastern China – including Anchiornis and Xiaotingiapreserve anatomy that seemingly challenges the status quo. (1) To resolve this debate we performed an up-to-date phylogenetic analysis for paravians using the latest Theropod Working Group (TWiG) coelurosaur data matrix which we supplemented with new data from recently described Mesozoic paravians from Asia and North America (e.g., Zhenyuanlong and Acheroraptor). This includes data from the unnamed dromaeosaurid IVPP V22530 and Luanchuanraptor, which are included in a phylogenetic analysis for the first time. We also incorporate new data from iconic paravians such as Archaeopteryx and Velociraptor based on firsthand study. (2) The analysis adopted the maximum parsimony criterion and was performed in the phylogenetic software TNT. Our preliminary results support the monophyly of each of the traditionally recognized paravian clades. (3) The Late Jurassic paravians from northeastern China (e.g., Anchiornis and Xiaotingia) are recovered as avialans rather than deinonychosaurians, at a position more basal than Archaeopteryx and other derived avialans (4). The traditional sister group status of Troodontidae and Dromaeosauridae is reaffirmed (5) and is supported by a laterally exposed splenial and a characteristic raptorial pedal digit II. Recently reported Early Cretaceous dromaeosaurids from northern and northeastern China, including Zhenyuanlong, Changyuraptor and IVPP V22530, are closely related to other microraptorines as expected. (6) Luanchuanraptor, a dromaeosaurid from the Late Cretaceous of central China is recovered as a more advanced eudromaeosaurian. By tracing character evolution on the current tree topology we report on the latest insights into the adaptive radiation amongst early paravians, including the origin of flight and changes in body size and diet. (7)

Notes

  1. In the LRT Xiaotinigia and Anchiornis have nested as derived troodontids, basal to birds since their insertion into the LRT more than 3 years ago. So that’s confirmation that troodontids are basal to Archaeopteryx and other birds with Xiaotinigia and Anchiornis as proximal outgroup taxa.
  2. But did they include five or more Archaeopteryx specimens, as in the LRT? They don’t say so…
  3. In the LRT there is a clade that includes Velociraptor, but the Troodontidae does not produce a clade that does not include birds. Rather birds are derived troodontids in a monophyletic clade.
  4. If avialans are usually defined as all theropod dinosaurs more closely related to modern birds (Aves) than to deinonychosaurs, all troodontids are avialans in the LRT. Since Troodontidae was named by Gilmore in 1924, the term Avialae (Gauthier 1986) is a junior synonym.
  5. Troodontidae and Dromaeosauridae are also sisters in the LRT.
  6. This confirms the topology recovered in the LRT from about a year ago. Microraptorines, like Microraptor and basal tyrannosauroids like Zhenyuanlong are not related to troodontids or birds, but to tyrannosaurs and compsognathids.
  7. I’d like to see their tree whenever it is published to compare the two.
Figure 7. Bird cladogram with the latest additions. Here the referred specimen of Yanornis nests with enantiornithes while Archaeovolans nests within the Scansoriopterygidae, not with Yanornis.

Figure 1. Bird cladogram from several months ago. Here Avialae is a junior synonym for Troodontidae.

References
Pei R, Pittman M, Norell M and Xu X 2016. A review of par avian phylogeny with new data. Abstract from the 2016 meeting of the Society of Vertebrate Paleontology.

The first Jurassic feather – SVP abstract 2016

Pittman et al. 2016
describe a new way of looking at fossils, with laser stimulated fluorescence. I can’t show you what attendees saw at SVP as it is awaiting publication, but other examples can be seen here online. This image from Tom Kaye (Fig. 1) was bumped by me with Photoshop to increase contrast and perhaps reveal a wee bit more detail.

Figure 1. Archaeopteryx feather from T. Kaye. Second image is Photoshop contrast bump created here.

Figure 1. Archaeopteryx feather from T. Kaye. Second image is Photoshop contrast bump created here. Pittman et al. laser stimulated fluorescence imagery was shown at SVP and is awaiting publication. 

From the Pittman et al. 2016 abstract
“The single feather initial holotype of Archaeopteryx lithographica is one of the world’s most iconic fossils, but contains a 150 year old mystery. The specimen’s 1862 description by Hermann von Meyer shows that the calamus is 15 mm long and 1 mm wide. However, the calamus is no longer visible on the fossil, and there is no record of when or how it disappeared. The specimen is a rare example of a lone Archaeopteryx feather, giving access to its entire morphology, as opposed to only parts of it in the overlapping feathers of articulated specimens. This makes it an important addition to the anatomical record of Archaeopteryx and basal birds more generally. After 150 years, laser stimulated fluorescence has recovered the calamus as a chemical signature in the matrix and reveals preparation marks where the original surface details have been obliterated. The feather has recently been imaged by others under UV light as well as with X-rays at the Stanford Linear Accelerator Center, with no reports of the existence of the calamus. This demonstrates the capability of laser stimulated fluorescence to visualize important data outside the range of current methodologies. The feather has at different times, been cited as a primary, secondary and covert, and has even been suggested to belong to another taxon. With the new calamus data in hand, the morphology of the feather was examined within the framework of modern feather anatomy. The percentage of calamus length to overall feather length, when plotted against a histogram of 30 phylogenetically and ecologically diverse modern birds, comes out in the middle of the range, placing it in the flight feather regime. The most recent identification of the feather as a primary dorsal covert can be discounted because the rachis is in line with the calamus rather than curving upwind of the calamus centre line. The curvature of the rachis is also too pronounced to function as a primary or tail feather. If the feather is scaled as a secondary in the wing of Archaeopteryx, only five feathers fit the reconstruction along the ulna, rather than the 9-13 that have been estimated for this taxon and the 7-14 that are found in modern birds. These inferences suggest that the isolated feather is fundamentally inconsistent with those of Archaeopteryx and is instead a secondary of another early bird taxon or potentially even a feather of a non-avialan pennaraptoran theropod.”

Kaye’s work with fossil imaging
has revealed many interesting and otherwise invisible traits. Let’s call this one more ‘feather in his cap.’

References
Pittman M, Kaye TG, Schwarz D, Pei R and Xu X 2016. 150 year old Archaeopteryx mystery solved. Abstract from the 2016 meeting of the Society of Vertebrate Paleontology.

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0125923

2015 SVPCA abstract supports troodontid-bird clade

Nice to get confirmation
for a subset of the large reptile tree in a SVPCA poster (Brougham 2015).

From the Brougham results:
“The modified matrix strongly supports a Troodontidae + Avialae clade rather than a monophyletic Deinonychosauria, a topology remarkably convergent on that seen in modified Godefroit phylogeny, in which Aurornis, Eosinopteryx and the Tiaojishan paravians form a sister clade to Anchiornis and more derived avialans, the two of which in turn form a sister clade to Troodontidae.”

Figure 1. Basal theropod subset of the large reptile tree showing troodontids basal to birds and separate from dromaeosaurs.

Figure 1. Basal theropod subset of the large reptile tree showing troodontids (light red) basal to birds (red) and separate from dromaeosaurs (white).

References
Brougham T 2015. Multi-matrix analysis of new Chinese feathered dinosaurs supports troodontid-bird clade. researchgate.net/publication/280728942

Flapping before flight

This is a long overdue and very welcome paper
Many paleontologists of the past thought flight appeared after gliding. This is the so-called trees down theory seen in this PBS video on Microraptor. Others thought the flight stroke appeared while clutching bugs in the air. This is the so-called ground up theory. Through experimentation Ken Dial found out that baby birds armed with only protowings flapped them vigorously to help them climb trees, no matter the angle of incline. Now the kinematics of this wing/leg cooperation are presented in Heers et al. 2016, students of Ken Dial.

Key thoughts from the abstract:
“Juvenile birds, like the first winged dinosaurs, lack many hallmarks of advanced flight capacity. Instead of large wings they have small “protowings”, and instead of robust, interlocking forelimb skeletons their limbs are more gracile and their joints less constrained. Such traits are often thought to preclude extinct theropods from powered flight, yet young birds with similarly rudimentary anatomies flap-run up slopes and even briefly fly, thereby challenging longstanding ideas on skeletal and feather function in the theropod-avian lineage.
For the first time, we use X-ray Reconstruction of Moving Morphology to visualize skeletal movement in developing birds. Our findings reveal that developing chukars (Alectoris chukar) with rudimentary flight apparatuses acquire an “avian” flight stroke early in ontogeny, initially by using their wings and legs cooperatively and, as they acquire flight capacity, counteracting ontogenetic increases in aerodynamic output with greater skeletal channelization.Juvenile birds thereby demonstrate that the initial function of developing wings is to enhance leg performance, and that aerodynamically active, flapping wings might better be viewed as adaptations or exaptations for enhancing leg performance.”
Figure 2. Cosesaurus running and flapping - slow.

Figure 1. Cosesaurus running and flapping – slow.

The same theory
can be applied to the development of wings in fenestrasaurs (Fig. 1) evolving into pterosaurs (Fig 2), as shown several years ago, but does not play a part in the development of flapping wings in bats, which do not walk upright and bipedally.
Quetzalcoatlus running like a lizard prior to takeoff.

Figure 2 Quetzalcoatlus running like a lizard prior to takeoff. Click to animate.

It should be obvious
that competing take-off theories for pterosaurs (Fig. 3) do not take into account this theory on the origin of flapping. Just one more reason not to support the forelimb wing launch hypothesis that has become so popular with ptero-artists recently.

Unsuccessul Pteranodon wing launch based on Habib (2008).

Figure 3. Unsuccessul Pteranodon wing launch based on Habib (2008) in which the initial propulsion was not enough to permit wing unfolding and the first downstroke.

Remember,
getting into the air is difficult if you’ve never done it before. Using both your arms AND your legs to get up speed is a good idea that has worked in the past and in present day laboratories.

References
Heers AM, Baier DB, Jackson BE & Dial  KP 2016. 
Flapping before Flight: High Resolution, Three-Dimensional Skeletal Kinematics of Wings and Legs during Avian Development. PLoS ONE 11(4): e0153446. doi:10.1371/journal.pone.0153446
http: // journals.plos.org/plosone/article?id=10.1371/journal.pone.0153446

The first flightless birds

Yesterday we looked at several early birds (Fig. 1). Earlier we considered the phylogenetic nesting of Balaur (Fig. 2; Csiki Z et al. 2010), which some workers (Cau et al. 2015) considered an early flightless bird.

Figure 7. Bird cladogram with the latest additions. Here the referred specimen of Yanornis nests with enantiornithes while Archaeovolans nests within the Scansoriopterygidae, not with Yanornis.

Figure 7. Bird cladogram with the latest additions. Here the referred specimen of Yanornis nests with enantiornithes while Archaeovolans nests within the Scansoriopterygidae, not with Yanornis.

When determining
the first flightless birds, one must first decide which taxon represents the first or basal bird. In the large reptile tree (subset Fig. 1) the last common ancestor of Enantiornithes and Euornithes is Archaeopteryx siemensi, represented by the Berlin and the Thermopolis specimens. Thus they represent, in this cladogram, the first or basal birds. Both the Enantiornithes and Euornithes produced specimens with a locked down coracoid and expanded sternum, anchors for powerful flight muscles attached to long feathered forelimbs.

Thus the purported first flightless bird,
Balaur, nests outside the bird clade (Fig. 1) established by the large reptile tree.

Figure 1. Balaur compared to various dromaeosaurids and to Sapeornis, both to scale and enlarged for detail. Cau, Brougham and Naish wondered if Balaur was the first neoflightless bird, a sort of dodo of the Cretaceous.

Figure 1. Balaur compared to various dromaeosaurids and to Sapeornis, both to scale and enlarged for detail. Cau, Brougham and Naish wondered if Balaur was the first neoflightless bird, a sort of dodo of the Cretaceous.

Instead
the Scansoriopterygidae produced the first taxa in the Eurornithes with more of a dinosaur/theropod look, with Mei (Early Cretaceous) having the smallest forelimbs relative to the rest of the body in that clade. No doubt it was flightless — and with shorter coracoids and a tiny sternum, reduced its flapping. By contrast, its current sister, Archaeovolans (Fig. 3), retained a robust pectoral girdle and long forelimbs.

Figure 9. Sister taxa at the base of the scansoriopterygidae include Jeholornis, Mei and Archaeovolans, here shown to scale.

Figure 2. Sister taxa at the base of the scansoriopterygidae include Jeholornis, Mei and Archaeovolans, here shown to scale.

As everyone knows,
flightless birds have arisen several times since the Early Cretaceous with Hesperornis and Struthio as examples in the large reptile tree. In evolution everything is gradual and often enough, reversible. And behavior is best determined at the extremes of morphology. More generalized taxa probably had more generalized behavior.

In Dinosaurs of the Air
author Greg Paul Paul “argues provocatively for the idea that the ancestor-descendant relationship between the dinosaurs and birds can on occasion be reversed, and that many dinosaurs were secondarily flightless descendants of creatures we would regard as birds.” According to the large reptile tree, dromaeosaurids and basal troodontids were not birds. But birds are derived troodontids. And troodontids arise from basal dromaeosaurids.

Along these same lines Kavanau 2010 reported
“Varricchio et al. propose that troodontids and oviraptorids were pre-avian and that paternal egg care preceded the origin of birds. On the contrary, unmentioned by them is that abundant paleontological evidence has led several workers to conclude that troodontids and oviraptorids were secondary flightless birds. This evidence ranges from bird-like bodies and bone designs, adapted for climbing, perching, gliding, and ultimately flight, to relatively large, highly developed brains, poor sense of smell, and their feeding habits.” Not so, according to the large reptile tree. But, to their point, bird-like theropods have arisen about 8 times by convergence, as we looked at earlier here.

References
Cau A, Brougham T and Naish D. 2015. The Phylogenetic Affinities of the Bizarre Late Cretaceous Romanian Theropod Balaur bondoc (Dinosauria, Maniraptora): Dromaeosaurid or Flightless Bird? PeerJ. 3: E1032. DOI: dx.doi.org/10.7717/peerj.1032
Csiki Z, Vremir M, Brusatte SL, Norell MA 2010. An aberrant island-dwelling theropod dinosaur from the Late Cretaceous of Romania. Proceedings of the National Academy of Sciences of the United States of America 107 (35): 15357–15361.
Kavanau JL 2010. Secondarily flightless birds or Cretaceous non-avian theropods? Med Hypotheses 74(2):275-6.
Paul G 2002. Dinosaurs of the Air: The Evolution and Loss of Flight in Dinosaurs and Birds. Johns Hopkins University Press, Baltimore, 472 pp.

wiki/Balaur_bondoc

newslink on secondarily flightless bird Epidexoptryx.

A fresh look back at the ‘Archaeoraptor’ scandal

Earlier we looked at the ‘Archaeoraptor’ scandal under the heading “chimaeras and fakes.” Here we’ll start with a short history, then consider new discoveries and cladograms.

Figure 1. 'Archaeoraptor' in UV light from a page spread in National Geographic. When this was published it was big news.

Figure 1. ‘Archaeoraptor’ in UV light from a page spread in National Geographic. When this was published it was big news. Now such specimens have become more commonplace.


In July 1997
an unidentified Chinese farmer uncovered a rare (at that time) Early Cretaceous dinosaur with feathers (Fig. 1). During collection the plate on which the dinosaur was preserved cracked apart into a dozen or so pieces (Fig. 2). These were cemented together, but lacked feet and a tail. Nearby, from the same locality, a ‘suitable’ set of feet and tail were cemented to the plate to create a complete presentation. A year later the fossil was sold to an unidentified dealer and smuggled into the United States.

In February 1999
the feathered fossil was on display at the Tucson Gem and Mineral Show where it was purchased by The Dinosaur Museum in Blanding, Utah, USA. Artists, Stephen and Sylvia Czerkas ran the museum. A board member provided the $80,000 purchase price. Paleontologists Phil Currie and Xu Xing agreed to study the fossil.

In March 1999
Currie noticed the left and right feet (pedes) were identical: part and counterpart. ‘Improvements’ like this happen more often than one would wish with fossils that are purchased from dealers rather than extricated from a site by museum led expeditions.

Figure 1. Archaeoraptor from Rowe et al. 2000. Colored areas indicate different sources for matrix and fossils there in.

Figure 2. Archaeoraptor from Rowe et al. 2000. Colored areas indicate different sources for matrix and fossils there in.

In July 1999
CT scans were made of the fossil (Rowe et al. 2001, Fig. 2). These indicated that the bottom fragments were not part of the upper fossil, but that news did not get out until later.

In August 1999
authors Czerkas, Currie, Rowe and Xu submitted a paper to Nature on the fossil, noting that the legs and tail were composited into the slab. Nature rejected the paper. Shortly thereafter Science rejected the paper, with referees noting the illegal purchase and doctoring of the fossil.

In September 1999
Currie’s preparator concluded the fossil was a composite of 3 to 5 specimens. Again that news did not get out until later.

In October 1999
National Geographic Magazine held a press conference at which they unveiled the fossil  informally named, “Archaeoraptor,” and announced it as a transitional fossil between birds and non-bird theropod dinosaurs (which it is not, see below). Plans were also announced to return the illegally exported fossil to China.

The November 1999 issue of Nat Geo
featured the fossil in an article about dinosaur feathers (Sloan 1999, Fig. 1). Bird expert Storrs Olson criticized the pre-naming of any fossil in a popular publication without proper peer review in an academic publication. Nobody was able to ‘stop the presses’ at Nat Geo.

In December 1999 Xu Xing
sent emails to Sloan and others announcing he had found the counterpart for the tail of ‘Archaeoraptor’, but it belonged to another genus, a microraptor. Perhaps a bit to harshly, Xu Xing labeled the Nat Geo specimen a ‘fake.’

In February 2000 Nat Geo issued a press release
stating an investigation had begun and indicating the fossil may be a chimaera or a composite, something museums create. or at least used to create, on a regular basis.

In March 2000 Nat Geo published 
the forum letter from paleontologists Xu Xing suggesting that the tail did not match the rest of the body. The word ‘fake’ was replaced with ‘composite’ by the editors. And that seems  appropriate.

In April 2000 Stephen Czerkas
admitted his mistake. Others involved also expressed regret.

In October 2000 Nat Geo published 
the results of their investigation (Simmons 2000), concluding that the fossil was a composite and that most of the pertinent parties had made some mistakes.

In March 2001 Nature published
a short paper by Rowe et al. (2001) who reported on the evidence from the CT scans. They concluded that the top part was a single specimen. A second part provided the left femur, a third both tibiae, a fourth both feet and a fifth separate specimen provided the tail.

Now, here’s where it gets interesting…

In August 2002
Czerkas and Xu (2002) published an anonymously reviewed description of the fossil, renaming it Archaeovolans (Fig. 3), but it was in a self-published book, not an academic journal.

Figure 3. Archaeoraptor from Czerkas and Xu 2002 along with the original line art tracing and a new color tracing.

Figure 3. Photo of Archaeoraptor from Czerkas and Xu 2002 along with the original line art tracing and a new color tracing. Click to enlarge.

In November 2002
Zhou et al. (2002) reported the majority of the fossil belonged to the established genus Yanornis (Zhou and Zhang 2001, Fig. 4) an euornithine bird nesting basal to Ichthyornis and Hesperornis in the large reptile tree (subset in Fig. 8). Wikipedia likewise reports that Yanornis is an ornithuromorph, the clade that includes all living birds. Similarly, Zhou and Zhang considered Yanornis a member of the Ornithurae.

Figure 4. Yanornis martini holotype (IVPP V12558, Zhou and Zhang 2001) as originally traced and reconstructed by moving those traced lines back to in vivo positions.

Figure 4. Yanornis martini holotype (IVPP V12558, Zhou and Zhang 2001) as originally traced and reconstructed by moving those traced lines back to in vivo positions. This is a euornithine bird with several traits retained by living birds not shared with the STM9-52 specimen (Fig. 6).

I traced
the IVPP V12444 specimen of Archaeoraptor/Archaeovolans/Yanornis (Fig. 3) and created a reconstruction (Fig. 5). I did the same with the STM9-52 specimen assigned (by Zheng et al. 2014) to Yanornis (Fig. 6). The holotype of Yanornis was restored to an in vivo configuration from published tracings in Zhou and Zhang 2001 (Fig. 4). Data from all three were added to the large reptile tree (subset in Fig. 7) for phylogenetic analysis.

Figure 5. Archaevolans reconstruction. Take a look at the in situ hands. In one the metacarpals increase in length laterally. In the other metacarpals and digits 2 and 3 have changed places during taphonomy. The rest of the skeleton is scansoriotpterigid, so I went with the compact metacarpals configuration. Note the procumbent premaxilla teeth, as in Epidexipteryx.

Figure 5. Archaevolans reconstruction. Take a look at the in situ hands. In one the metacarpals increase in length laterally. In the other metacarpals and digits 2 and 3 have changed places during taphonomy. The rest of the skeleton is scansoriotpterigid, so I went with the compact metacarpals configuration. Note the procumbent premaxilla teeth, as in Epidexipteryx.

Rather than lumping all three taxa together
the cladogram split them far apart. So Archaeovolans is not a junior synonym for Yanornis nor is it closely related. Moreover, the STM9-52 specimen referred to Yanornis by Zheng et al. 2014 is not congeneric with it, but nests elsewhere on the tree based on a long list of differences.

Figure 6. Specimen STM9-52 assigned to Yanornis by O'Connor et al. but in the large reptile tree nests instead with Mei in the clade enantiornithes.

Figure 6. Specimen STM9-52 assigned to Yanornis by Zheng et al. 2014, but in the large reptile tree nests instead with the basal enantiornithine, Protopteryx. Note the enormous unfused hands, elongate sternum. lack of a pygostyle and clavicle with a stem.

Perhaps even more interesting
Archaeovolans is phylogenetically bracketed by taxa that have a long bony tail. So the farmer was right — but that didn’t make it right to just pull another one off the shelf.

Figure 7. Bird cladogram with the latest additions. Here the referred specimen of Yanornis nests with enantiornithes while Archaeovolans nests within the Scansoriopterygidae, not with Yanornis.

Figure 7. Bird cladogram subset of the large reptile tree with the latest additions. Here the referred specimen of Yanornis nests with enantiornithes while Archaeovolans nests within the Scansoriopterygidae, not with Yanornis. 

 

The added foot and counter foot
are the right size, but phylogenetically wrong (Fig. 8). The foot and counter foot provided to Archaeovolans have traits found in ornithurine birds, like Yanornis. The correct feet would have had a shorter digit 2, with pedal 2.1 shorter than p2.2, and probably a shorter digit 4.

Figure 8. The foot and counter foot provided to Archaeovolans do not match those of sister taxa but more closely match those of ornithurine birds, like Yanornis.

Figure 8. The foot and counter foot provided to Archaeovolans do not match those of sister taxa but more closely match those of ornithurine birds, like Yanornis. Archaeovolans probably followed the pattern set by its sisters and would have had a relatively shorter digit 2 and digit 4.

According to the large reptile tree
(subset in Fig. 7) the Scansorioterygidae includes at its base the Munich specimen of Archaeopteryx bavarica. Earlier we looked at the need to include several specimens of Archaeopteryx (aka Solnhofen birds) in phylogenetic analysis, because most are distinct from one another and (to my eye) not congeneric. Furthermore, several nest at the bases of the earliest bird clades.

Figure 9. Sister taxa at the base of the scansoriopterygidae include Jeholornis, Mei and Archaeovolans, here shown to scale.

Figure 9. Sister taxa at the base of the scansoriopterygidae include Jeholornis, Mei and Archaeovolans, here shown to scale.Click to enlarge. The tail was reduced in more derived scansoriopterygids, like Epidexipteryx. A relatively small pelvis is shared by all three. 

With these results
Archaeovolans can apparently keep the name that Czerkas and Xu (2002) gave it. The distinction from Yanornis seems pretty obvious. I am surprised that that old paradigm has not been busted yet.

References
Czerkas SA and Xu X 2002. A new toothed bird from China. Pp. 43-60 in Czerkas SJ. ed. 2002. Feathered Dinosaurs and the Origin of Flight. The Dinosaur Museum Journal 1. Blanding, Utah, USA.
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 Archaeoraptor Fossil Trail. National Geographic 198 (4): 128–132.
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