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

Hummingbird and Swift Ancestor Reconstructed

Eocypselus rowei (Figs. 1-3, Eocene, 50 mya) has been found to be close to the common ancestor of both hovering hummingbirds and speedy swifts  (Ksepka et al. 2013). The modern taxa have evolved distinct wing shapes for their distinct flight styles. The new fossil with soft tissue feather impressions demonstrates the more generalized (plesiomorphic) wing shape that preceded that divergence.

Plate for Eocyupselus with soft tissue preservation.

Figure 1. Plate for Eocypselus rowei with soft tissue preservation.

Both swifts and hummingbirds have smaller feet and legs than those of Eocypselus rowei. Because of this, along with their extraordinary flying abillities, swifts and hummingbirds forego walking for the most part. In contrast, Eocypselus rowei appears to have been a good walker with longer metatarsals and legs.

Eocipselus counterplate distorted to match plate. Evidently the plate and counter plate were not taken from the exact same viewpoint.

Figure 2. Eocipselus rowei counterplate distorted to match plate. Evidently the plate and counter plate were not taken from the exact same viewpoint.

Eocypselus rowei had a stout humerus (Fig. 6) but not so stout as either a swift or hummingbird, both of which were relatively 2/3 the length and 1/3 deeper (Fig. 6). Likewise in the swift and hummingbird the radius/ulna is about 2/3 of the length in Eocypselus rowei. The manus of the swift and hummingbird is much longer than the combined length of the ulna and humerus (Fig. 4), but not so in the more generalized and primitive Eocypselus rowei.

Figure 3. Tracing of Eocypselus, identifying bones by color.

Figure 3. Tracing of Eocypselus, identifying bones by color. DGS used here to trace elements.

Lead author Daniel Ksepka reported, “This fossil bird represents the closest we’ve gotten to the point where swifts and hummingbirds went their separate ways.”

Figure 4. Reconstruction of Eocypselus. The pelvis is preserved in ventral view, so is difficult to ascertain in lateral view, but it probably looked very much like that of most other similar birds.

Figure 4. Reconstruction of Eocypselus rowei. The pelvis is preserved in ventral view, so is difficult to ascertain in lateral view, but it probably looked very much like that of most other similar birds. Also shown is Apus (illustration from Eyton 1867), the modern common swift, in which the hand bones exceed the humerus + ulna in length.

Eocypselus vincenti (Harrison 1984, Mayr 2010, Fig. 5) is a congeneric specimen from the Early Eocene of Europe.

Eocypselus vincenti, a related species from Europe. Apparently the manus is larger here than in E. rowei.

Figure 5. Eocypselus vincenti, a related species from Europe from Mayr (2010). Apparently the manus is slightly larger and the tibia is slightly smaller here than in E. rowei. Note the lack of scapulocoracoid fusion here. 

Mayr (2010) also found Eocypselus vincenti to be related to swifts and hummingbirds. Harrison (1984) originally named Eocypelus. Others have also found and described this genus.

The evolution of the humerus in Eocypselus, swifts and hummingbirds.

Figure 6. The evolution of the humerus in Eocypselus, swifts and hummingbirds, rearranged and colored from Mayr 2003. In both swifts and hummingbirds the humerus becomes increasingly robust and in both a new process develops (1, 3) that originates in Eocypselus.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

Reference
Eyton TC 1867. Osteologia avium; Or, a Sketch of the Osteology of Birds / II. : Wellington, London.
Harrison CJO 1984. A revision of the fossil swifts (Vertebrata, Aves, suborder Apodi), with descriptions of three new genera and two new species. Mededelingen van de Werkgroep voor Tertiaire en Kwartaire Geologie 21:157–177.
Ksepka DT, Clarke JA, Nesbitt SJ, Kulp FB and Grande L. 2013. Fossil evidence of wing shape in a stem relative of swifts and hummingbirds (Aves, Pan-Apodiformes). Proceedings of the Royal Society B: Biological Sciences 280 (1761): 20130580. doi:10.1098/rspb.2013.0580. Supplementary materials here.
Mayr G 2003. Phylogeny of early Tertiary swifts and hummingbirds (Aves: Apodiformes). The Auk 120(1):145–151, 2003. online
Mayr G 2009. Paleogene Fossil Birds (online) Springer.
Mayr G 2010. Reappraisal of Eocypselus—a stem group apodiform from the early Eocene of Northern Europe. Palaeobiodiversity and Palaeoenvironments 90(4): 395-403.

Discover Magazine online

wiki/Eocypselus
Fossil hummingbirds online pdf

Donald Duck Dinosaur Skeleton

Just had to share this one (old news (2008) for most, new for me).

Donald Duck skeleton

Donald Duck skeleton. Note the long sacral series and very birdy hips. Pedal digit 1 has never been seen in cartoons, but is appears here. Contrast those with the very human (but lacking one digit) forelimbs and hands. All tongue in cheek, of course.

Follow these links to see the skeletons of other cartoon characters, Tom & Jerry, Roadrunner, Wile E. Coyote and Bugs Bunny.

Link 1 - Link 2 - Link 3

Here are the nephews, Huey, Dewey and Louie (not sure which is which). This caught my eye and brought a big smile.

Huey, Dewey and Louie skeletons

Huey, Dewey and Louie skeletons

South Korean artist, Hyungkoo Lee, created this ‘Animatus’ series with the “intention to analyze anatomical structures and physical forms of animation characters, within the hypothesis to visualize their possible anatomical foundation.” Skeletons are a hybrid mix of animal bones and synthetic materials.

They are also a hybrid mix of avian (dinosaur feet) and human (mammal hands), but note the wishbone, long coracoids and sternum!

Disney (1929) had his own take on animated skeletons here.

Earlier Roadrunner was transformed into Pterorunner here. 

Eosinopteryx – part 3 – to scale

Sometimes it just helps
to see taxa to scale with possible sisters (Eosinopteryx in this case, Fig. 1). Smaller than Anchiornis, Eosinopteryx also had a shorter snout, deeper mandible, more robust postorbital, longer torso, shorter tail, larger chevrons, more robust clavicle, coracoid and scapula, shorter forelimb, smaller deltopectoral crest and shorter pubis.

Eosinopteryx and kin to two scales.

Figure 1. Eosinopteryx and kin to two scales.

Huaxiangnathus shared with Eosinopteryx a short coracoid, but little else is a closer match than the similarly built Anchiornis. Godefroit et al. (2013) reported, “The straight and closely aligned ulna-radius of Eosinopteryx also means that pronation/supination of the manus with respect to the upper arm would have been limited; combined with the absence of a bony sternum and weakly developed proximal humerus, these attributes suggest that Eosinopteryx had little or no ability to oscillate the arms to produce a wing beat.”

Funny that they didn’t even mention the short coracoid.
The locked down elongate coracoid is a hallmark of flapping tetrapods (pterosaurs and birds) and an elongate clavicle does the same thing in bats.

According to the Sinkkonen illustration (Fig. 1), the radius and ulna are likewise essentially straight in Anchiornis, which is the plesiomorphic condition, as shown by Huaxiagnathus and other theropods. The ulna is barely bowed in Archaeopteryx and more greatly bowed in subsequent flapping taxa, including oviraptorids (by convergence?). Xiaotingia (Fig. 2), the outgroup to Anchiornis + Eosinopteryx, also has a short rostrum, but also a greatly bowed anterbrachium and a locked-down coracoid. I suspect a change in tree topology may be warranted or else we’ll learn something here about reversals.

I have asked for the matrix.

Figure 2. Xiaotingia the outgroup to Achiornis + Eosinopteryx + other Troodontidae. Red arrow points to bowed antebrachium. DGS enabled identification of the coracoids, which are elongated here.

Figure 2. Xiaotingia the outgroup to Anchiornis + Eosinopteryx + other Troodontidae. Red arrow points to bowed antebrachium. DGS enabled identification of the coracoids, which are elongated here. This is a flapping theropod. Inset shows previous tracing that did not identify two coracoids.

The bowed antebrachium
produces a parallelogram in living birds that serves to automatically extend and fold the manus bearing the outer flight feathers with flexion/extension of the elbow. Prior to this, muscle power would have to extend and bend the wrist, independent of the flexion/extension of the elbow.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Godefroit P, Demuynck H, Dyke G, Hu D, Escuillié FO and Claeys P. 2013. Reduced plumage and flight ability of a new Jurassic paravian theropod from China. Nature Communications 4: 1394. doi:10.1038/ncomms2389

wiki/Eosinopteryx

Eosinopteryx – part 2 – Better Resolution = Better Reconstruction

Yesterday we looked at Eosinopteryx (Godefroit et al. 2013, Middle-Late Jurassic, Tiaojishan Formation) and discussed a possible new nesting site (Fig. 1) based on a lack of included short-coracoid taxa preceding Archaeopteryx to compare it with. By comparison, Cosesaurus has a “flapping”-type coracoid and it has much less wing tissue trailing its front limbs. So the long, locked-down coracoid in bird predecessors was among the last traits to evolve, post-dating the appearance of elongated forelimb feathers.

Supplementary information

Figure 1. Supplementary information from Godefroit et al. (2013) showing their nesting of Eosinopteryx with Anchiornis, but the tree lacks several short-coracoid taxa that might provide more parsimonious nesting sites.

Addendum: The analysis of Godefroit et al. (2013) was based on and provided only a segment of an earlier analysis that DID include these more primitive taxa. Thus my doubt is reduced considerably as all pertinent taxa were included. The skull on DGS

Not sure if a skull reconstruction was provided by Godefroit et al. (2013) or not. (not) I’d still like to see the paper. (I have the paper now. ) Even so, in order to create yesterday’s reconstruction I applied DGS (digital graphic segregation) to the skull (Fig. 2). I don’t know birds as well as dinosaurs and did not attempt a palate reconstruction. If I made any mistakes, please send me an email. (Figure 2 is an update based on higher resolution images of an earlier posted figure.)

Figure 2. The skull of Eosinopteryx in situ (above), traced using DGS (middle), and as presented by G et al. 2013). The red bone is the quadrate sticking through the mandibular fenestra, which was purportedly missing.

Figure 2. The skull of Eosinopteryx in situ (above), traced using DGS (middle), and as presented by Godefroit et al. 2013). The red bone is the quadrate sticking through the mandibular fenestra, which was purportedly missing. See Figure 3 for reconstruction and bone identification. While my tracing appears to be chaotic, every bone was traced on a separate and segregated layer.

Above
The skull of Eosinopteryx traced using Photoshop, a process known as DGS or Digital Graphic Segregation. For followers of this blog, these updated images reflect the importance of high resolution data in using DGS. Much like the Hale telescope, greater resolution enables the identification of finer lines and bones. This demonstrates that its not the mechanics of the technique so much, as the intimate knowledge long months of study provides when employed, and higher resolution really helps. (Higher resolution image did provide improved data.)

Figure 3. The skull of Eosinopteryx after tracing in higher resolution (1200 dpi). Here more bones and teeth were correctly traced and identified. A mandibular fenestra is present (contra Godefroit et al. 2013). It just had a quadrate stuck through it. Frontals overlap due to convexity. Even with these improvements, any errors should be brought to my attention for repair.

Figure 3. The skull of Eosinopteryx after tracing in higher resolution (1200 dpi). Here more bones and teeth were correctly traced and identified. A mandibular fenestra is present (contra Godefroit et al. 2013). It just had a quadrate stuck through it. Frontals overlap due to convexity. Even with these improvements, any errors should be brought to my attention for repair.

The premaxilla includes at least three elongated teeth (here seen from the inside). The saddle-shaped nasal was broken into at least four pieces during crushing. The maxilla is decayed beyond the normal fenestration. Here (Fig. 3) I reconstruct it conventionally. There is no elongated posterior lacrimal process and vestigial anterior process as Godefroit et al. (2013) reported. Rather the lacrimal is similar to that of other theropods. They did not provide a reconstruction. An earlier reconstruction of mine misplaced the quadrate articulation, which is repaired here. It also did not recognize the posterior mandible, which in situ is separated from the articular area. But here (Fig. 3) this has been repaired, thanks to theropod expert, M. Mortimer, for pointing this out. It was also overlooked by Godefroit et al. (2013, Fig. 2).

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Godefroit P, Demuynck H, Dyke G, Hu D, Escuillié FO and Claeys P. 2013. Reduced plumage and flight ability of a new Jurassic paravian theropod from China. Nature Communications 4: 1394. doi:10.1038/ncomms2389
Paul GS 2010. The Princeton Field Guide to Dinosaurs. Princeton University Press 320 pp.

wiki/Eosinopteryx

Eosinopteryx – part 1 – Feathers, but no flapping

Eosinopteryx brevipenna (Godefroit et al. 2013, Middle-Late Jurassic, Tiaojishan Formation) is represented by a new complete skeleton. It was a feathered theropod dinosaur about 30 cm long. The forelimb feathers were quite long (Fig. 1), but the tail feathers were not.

Paravian? or Preavian?
We’ve been looking for a feathered theropod without elongated coracoids to precede Archaeopteryx. We also need this taxon to be not pre-oviraptorid or pre-alvarezsaurid. The authors argue, with a very extensive phylogenetic analysis, that this is a troodontid resembling Anchiornis, with less extensive feathers on the hind limbs and tail. Anchiornis greatly resembled Archaeopteryx and is, therefore, closely related. Of that, there is no doubt.

Why There is Doubt
I have not created a competing analysis. Checking out Greg Paul’s figure of Anchiornis (Paul 2010), I note his Anchiornis has the short torso and elongated coracoid also seen in Archaeopteryx, troodontids and deinonychosaurs.

Figure 1. Click to enlarge. Eosinopteryx reconstructed in lateral view. Soft tissue impressions preserved on the fossil are represented here in gray. Note the small size of the coracoid (yellow) and its curved lower rim, which indicates this specimen was a pre-flapping dinosaur. Pedal digit 2 was not modified as a "killing" claw. Elements figured with DGS.

Figure 1. Click to enlarge. Eosinopteryx reconstructed in lateral view. Soft tissue impressions preserved on the fossil are represented here in gray. Note the small size of the coracoid (yellow) and its curved lower rim, which indicates this specimen was a pre-flapping dinosaur. Pedal digit 2 was not modified as a “killing” claw. Elements figured with DGS.

What sets Eosinopteryx apart from these?
A short coracoid with a broad curved ventral rim - Therefore Eosinopteryx did not flap and was not descended from flappers. We haven’t seen a terrestrial descendant of Archaeopteryx yet without elongated coracoids. For more on this, compare Huaxiagnathus (with its short coracoid) to Velociraptor, (with its long, tall coracoid). Otherwise these two greatly resemble one another, with the former lacking sternal plates, a retroverted pubis and caudal rods. These traits are also lacking in Eosinopteryx.

A relatively smaller skull – Much smaller than in Anchiornis.

A relatively longer torso – Much longer than in Anchiornis.

A relatively shorter pubis – Much shorter than in Anchiornis.

All these traits are primitive for theropods.

Unfortunately, 
Huaxiagnathus
 was not included in the analysis of Godefroit et al. (2013). Neither were oviraptorids or alvarezsaurids. Eosinopteryx
needs to be compared to these missing basal taxa along with the other taxa they previously tested. Once that’s done, let’s see if the topology of the tree doesn’t shift Eosinopteryx down below (more primitive than) Archaeopteryx. 

Addendum: The analysis of Godefroit et al. (2013) was based on and provided only a segment of an earlier analysis that DID include these more primitive taxa. Thus my doubt is reduced somewhat as all pertinent taxa were included.  Even so, I wonder why these two “sisters” don’t look more alike.

If anyone has details on why Godefroit et al. 2013 said the “bone structure would have limited its ability to flap its wings,” I’d like to see it.

Interesting that this birdy topic just came up a few days ago with Mahakala. Reminds me to be careful what I wish for.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Godefroit P, Demuynck H, Dyke G, Hu D, Escuillié FO and Claeys P. 2013. Reduced plumage and flight ability of a new Jurassic paravian theropod from China. Nature Communications 4: 1394. doi:10.1038/ncomms2389
Paul GS 2010. The Princeton Field Guide to Dinosaurs. Princeton University Press 320 pp.

wiki/Eosinopteryx

Mahakala – Size Evolution Preceding??? Avian Flight

Today we’ll look at a flightless bird/dromaeosaurid: Mahakala.
While the paper by Turner et al. (2007), “A basal dromaeosaurid and size evolution preceding avian flight” (pdf). was ostensibly about the origin of flight in birds, it actually says nothing about taxa preceding Archaeopteryx and neither does their included cladogram. Mahakala (Fig. 1, the new basal dromaeosaurid, as everyone knows, is Late Cretaceous and demonstrates the reduction of the wings FOLLOWING Archaeopteryx, its Late Jurassic predecessor. Lots of birds reduce the wings when they are no longer necessary for flight. Makhala is only one more. If you want to read more about the taxa preceding Archaeopteryx, look here.

Mahakala dromaeosaurFig. 1. Artist’s reconstruction of Mahakala omnogovae, a two-foot-long dinosaur unearthed in the Gobi Desert. © Frank Ippolito This is a good-looking representation of an incomplete fossil.
Some thoughts from Xu Xing in NatGeo 
Xu said a combination of birds’ ability to fly and to evolve quickly might have helped them survive.

“Birds mature within one year, and that gives them the means to adapt very rapidly to big changes in the environment,” he said.

My research indicates some birds take more than one year to mature (ostrich = 3-4 years, crow=2 years). Others take less. Reporters may have reported what they wanted to, perhaps misquoting Xu.

Some thoughts from Alan Turner in NatGeo|

“Paleontologists have long thought that miniaturization occurred in the earliest birds, which then facilitated the origin of flight,” said Alan Turner, lead author on the study and a graduate student at the American Museum of Natural History and Columbia University in New York. “Now, the evidence shows that this decrease in body size occurred well before the origin of birds and that the dinosaurian ancestors of birds were, in a sense, pre-adapted for flight.” Not so. Where’s the logic here? Large wings in the Jurassic clearly preceded the small wings of Mahakala of the Late Cretaceous. And, at least some of the more birdy taxa that followed Archaeopteryx were much, much smaller, as we looked at here.

Although paleontologists have shown that birds evolved from bipedal carnivorous dinosaurs known as theropods, fossil evidence of miniaturization and other characteristics leading to flight have been sparse. Not really… just not studied much. As in pterosaur precursors, everyone is looking for what they think they should find and ignoring what evidence is already out there.

Now Mahakala is providing the first signs of some of these early evolutionary steps. In particular, while other dinosaurs of the Cretaceous Period were evolving in favor of increased body size, Mahakala represented a progressive step towards miniaturization of body forms that would be necessary for feathered dinosaurs to eventually take flight. Not really. Mahakala is about the same size as Archaeopteryx.

“Flight isn’t an easy thing, because you are, in effect, countering the force of gravity,” said Turner. “Being really small appears to be a necessary first step. Other groups that evolved flight, such as pterosaurs and bats, all evolved from small ancestors.” Really? And those ancestors are…????? (Really, I know pterosaurs and bats evolved from small ancestors, see bats here and pterosaurs here. But those specimens are not acknowledged by traditional paleontologists. So, I’m wondering which taxa Turner was referring to? Or hoping for?)

Traditionally it’s been thought that the earliest birds were the first theropods to become really small. With the discovery of Mahakala we were able to show that this miniaturization occurred much earlier.” Ahem. You mean extended much later to the Late Cretaceous. Who was editing/proofing this copy??

 Mahakala shows that dinosaur size decreased progressively as they evolved toward birds. While this is something that has long been expected, Mahakala provides the first empirical evidence of this phenomenon. Again, the charts included in the article say otherwise, both chronologically and phylogenetically.

But what about….?
Now, I realize the Early Cretaceous tritosaur lizard, Huehuecuetzpalli, chronologically succeeded Triassic fenestrasaurs and pterosaurs. However, phylogenetically a sister of Huehuecuetzpalli preceded Triassic fenestrasaurs and pterosaurs. Makhala does not phylogenetically precede Archaeopteryx, according to the published charts, which show  no pre-Archaeopteryx taxa. That’s just not right when other studies have found a series of taxa with a gradually accumulating list of bird traits.

What we know

The origin of birds cladogram.

Figure 2. Click to enlarge. The origin of birds cladogram. Large clades are colorized. Red arrow points to the place on the chart where we will someday place the closest known ancestors of Archaeopteryx.

At least this cladogram (Fig. 2) shows some Triassic and Jurassic taxa (not that that’s required). In any case, we’re still looking for the precursor to Archaeopteryx that is not a closer precursor to oviraptorids, alvarezsaurids, etc. One of the keys to figuring out flightless or flapless taxa that came before or after is the design of the coracoid, as we looked at earlier with the precursors to pterosaurs that were flapping long before they were flying. With a locked down coracoid flapping can progress. With a sliding coracoid (the plesiomorphic condition), not so much.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Turner AH, Pol D, Clarke, JA, Erickson GM and Norell M 2007. “A basal dromaeosaurid and size evolution preceding avian flight” (pdf). Science 317 (5843): 1378–1381. doi:10.1126/science.1144066PMID 17823350.

Piksi: Look! It’s a bird! No it’s a pterosaur!

Varricchio (2002) described a new Cretaceous bird from the western US based on a lower humerus and upper radius and ulna, basically an elbow, plus a piece identified as a distal ulna (Figs. 1, 2). Just recently Agnolin and Varricchio (2012) reinterpreted the material as pterosaurian, most likely ornithocheirid and excluded from the Azhdarchidae.

Unfortunately
Except for the images of Piksi itself, the comparable evidence presented by Agnolin and Varricchio (2012, Fig. 1) was not of a high caliber. While Piksi was shown in high detail, the comparables were not (see comments in Fig. 1 caption).

Upper segment: Piksi compared to various pterosaurs and birds

Figure 1. Click to enlarge. Upper two rows: Piksi compared to various pterosaurs and birds as interpreted by Agnolin and Varricchio (2012). Lower two rows and then some: the same only rearranged with rotations to distal humerus view added (why were some inverted?). The capitulum is homologous with the dorsal condyle. Note the three condyles in Piksi, but only two were labeled. Lines were used for both bumps and foramina (not good). Did all of the pterosaur humeri have large distal foramina? Apparently so. Like birds, Piksi did not.

Guilt by association
Agnolin and Varricchio (2012) considered Piksi a type of ornithocheirid. They illustrated the humerus (Fig. 1) in a lineup with other pterosaurs, but it’s really not a good match for any of them with those three large condyles, the lack of distal foramina and those shorter distal, longer ventral dimensions. Unfortunately a lateral view was not presented. That might have shown larger trochlear joints that Piksi had, but ornithocheiroids don’t have, but Dimorphodon and Titanopteryx did. An olecranal fossa was present on Piksi (Fig. 2). A comparable deep depression is not seen in Anhanguera (Fig. 1).

As an experiment, I moved all the example pterosaur humeri together in one line and moved Piksi down to the birds line (Fig. 1) to see if part of the problem was “guilt by association.” What do you think?

Comparing the elbow of Piksi with the same bones in Anhanguera.

Figure 2. Comparing the elbow of Piksi with the same bones in Anhanguera. It’s not a good match. However, a better match among pterosaurs appears in Titanopteryx, an azhdarchid, but not a large one. These photos don’t closely match what is portrayed in the Agnolin and Varricchio (2012) illustrations. 

Confession time
Agnolin and Varricchio (2012) report that the Piksi bones are not like those of other contemporary pterosaurs, from the outline shape to the shape of the trochlea. They considered the distal view of the humerus “sub-triangular” as in Anhanguera (Fig. 1), but the two are quite distinct from each other in shape (so, perhaps this is wishful thinking?).

Is it really a bird?
As an experiment I restored bird-like elements and rearranged the bones of Piksi to a bird-like configuration (Fig. 3). The results are not too far off those of other birds. I’m no bird expert, but it looks like there is some variation in the olecranon process of the ulna and elsewhere on the skeleton.

Piksi as a bird.

Figure 3. Piksi as a bird. Some birds have an extended olecranon, others do not (pink arrows). The ulna appears to have a distinct curve, which pterosaurs never have. The distal ulna identified by Agnolin and Varracchio (2012) is a flattened circular disk, not the expected deeper shape. Who knows how long the actual bones were…

So, what is Piksi?
I suppose the final answer depends on who is interpreting the bones and what comparables are available. None of the above reconstructions are so close to pterosaurian or avian patterns to call it a walk-off home run. No wonder there was confusion. It didn’t help that Agnolin and Varracchio (2012) had some inverted illustrations and that the holes and hills could not be segregated.

I wonder if Piksi was flightless, which might have affected its morphology.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Agnolin FL and Varricchio D 2012. Systematic reinterpretation of Piksi barbarulna Varricchio, 2002 from the Two Medicine Formation (Upper Cretaceous) of Western USA (Montana) as a pterosaur rather than a bird. Geodiversitas 34 (4): 883-894. http://dx.doi.org/10.5252/g2012n4a10.

Varricchio DJ 2002. A new bird from the Upper Cretaceous Two Medicine Formation of Montana. Canadian Journal of Earth Science 39: 19-26.

Tiny Prehistoric Birds and Pterosaurs

Just a quick note. 
This blog is all about putting taxa together that don’t usually — or never — get together. Here I’ll just present a few birds and pterosaurs at the small end of the scale.

Small prehistoric birds and pterosaurs.

Figure 1. Small prehistoric birds and pterosaurs. From left to right, Sinornis, Cathayornis, No. 6 and No. 12 from the Wellnhofer (1970) catalog of “pterodactyloids.”

Both tiny birds and tiny pterosaurs dispensed with their long stiff tail. In birds it became a pygostyle. In pterosaurs the long stiff tail became a reduced, string-like tail with bead-like verts. Note the similarities in the pectoral girdles. Both could stand with their toes beneath their shoulder glenoids. Both had retroverted pedal digits but of two distinct designs. The anterior ilium of both taxa supported large thigh muscles. A large deltopectoral crest supported large flight adductors anchored to the sternum.

Size-wise, the tiny birds were not considered juveniles, but the pterosaurs were. Phylogenetic analysis illustrates the uniqueness of the two small pterosaurs. They cannot be matched to any larger adults that are phylogenetically close. Rather they are parts of a phylogenetic sequence of other tiny pterosaurs descending from larger forms and leading toward larger forms.

With regard to the tiny pterosaurs, I sense prejudice here. Just like tiny birds, let’s give them full adult rights and add them to a few new analyses to test the large pterosaur tree topology.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.

 

Little Early Birds – The Tiny Descendants of Archaeopteryx

Archaeopteryx, one of the most primitive birds, was among the smallest of all adult dinosaurs. But what followed Archaeopteryx was even smaller (Fig. 1).

Archaeopteryx and several other basal birds.

Figure 1. Archaeopteryx and several other basal birds. Here Archaeopteryx is a relative giant. This is an older illustration, predating all of the recent and now, not so recent, finds from China. The wings, sternum and tail are derived in the smaller birds. That’s the smallest Archaeopteryx, the Eichstätt specimen. 

Size reduction in early birds
Early maturation produces smaller adult birds. They cycle through life and reproduce quickly, before reaching the size of their parents and grandparents. And if their chicks mature even more quickly they will have smaller hips to produce smaller eggs. Smaller eggs produce smaller chicks that reproduce quickly. On and on, well, you get the idea.

The wings lost their individual fingers in these early birds. The tail shortened, developing a pygostyle (fused tail bones). The rostrum was shorter. The orbit was relatively larger. The sternum deepened, developing toward its modern shape. These little guys were smaller, lighter and stronger flyers. They were probably very hard for a predator to catch. They could lay eggs in otherwise inaccessible places. They may have had a higher, more bird-like metabolism, with greater needs for food, and more rapid reactions. They weighed only a fraction of Archaeopteryx, so the little birds could jump and fly easier.

Evolution happens more quickly in small taxa because they grow and reproduce at a faster rate. More generations appear in less time. By flying, birds can access more environments, from trees to seashores, which also has selective effects.

Parallels in pterosaurs
Earlier we talked about various pterosaur lines that shrank and evolved into new forms prior to ultimately producing larger forms. However, pterosaur ancestors, like Cosesaurus, were not larger than early pterosaurs. They did not develop wings through serial size reduction.

Parallels in bats
Today there are megabats and microbats. The most primitive bats were small. Bat ancestors, within the single genus Protictis, demonstrate the size reduction seen in birds during the development of wings.

Juveniles vs. Adults
Gobipteryx was considered an embryo. If so, it would have grown to the size of Archaeopteryx. Not sure about the possible juvenile status of the others. Since birds grew up so quickly and are all about the same size, the odds are the rest represent adults.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Dames W 1884. Ueber Archaeopteryx. Palaeontologische Abhandlungen, 2 (3):119-198.
Heller F 1959. Ein dritter Archaeopteryx Fund aus den Solnhofener Plattenkalken von Langenaltheim/Mfr. Erlanger Geologische Abhandlungen, 31: 1-25; Erlangen
von Meyer H 1861. Archaeopteryx litographica (Vogel-Feder) und Pterodactylus von Solenhofen. Neues Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefakten-Kunde. 1861: 678–679.
Owen R 1863. On the Archaeopteryx von Meyer, with a description of the fossil remains of a long-tailed species from the lithographic stone of Solnhofen. Philosophical Transactions of the Royal Society, London 153: 33-47.
Paul G 2002. Dinosaurs of the Air: The Evolution and Loss of Flight in Dinosaurs and Birds. Johns Hopkins University Press. 460 pp.
Wellnhofer P 1974. Das fünfte Skelettexemplar von Archaeopteryx. Palaeontographica Abt. A Vol. 147 S: 168-216.

wiki/Archaeopteryx