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However, recently this paper was retracted.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

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

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.