Samrukia nessovi, the prehistoric giant bird from Kazakhstan

Fig 1.- Very hypothetical reconstruction of Samrukia nessovi.

In a recent article published in Biology Letters, Darren Naish and colleagues named a new genus and species of Mesozoic bird, Samrukia nessovi, based on two pieces of lower jaw. The remains, hosted at the Wyoming Dinosaur Center in Thermopolis (Wyoming, USA), have been collected in the Bostobynskaya Formation of Late Cretaceous (Santonian-Campanian) age in Southern Kazakhstan.

Due to the fragmentary nature of the fossils, there isn’t much that can be said about the animal, save one remarkable fact: Samrukia was a giant bird. Even a crude extrapolation given by the size of the fragment of the lower jaw places the total dimension of the animal somewhere around 2 meters in length. The bird might have been a large flightless animal mimicking the bipedal non-avian theropods or a giant of the airs, mimicking the huge pterosaurs of that time, who knows? One thing is sure: Mesozoic birds were more diverse than previously thought, reaching sizes rivaling those of the non avialian dinosaurs living alongside them.

Fig 2.- Phylogenetic tree of birds closest dinosaurian relatives. Adapted from D. Naish et al., 2011. Compare with Xu et al., 2011.

There is however an interesting detail in the new phylogenetical analysis that was published alongside the paper in the supplementary electronic document. As in the Xu et al. paper mentioned in my previous post, the former “archetypal” ancestral bird, Archaeopteryx is knocked out of its perch as an Avialian but this time, it appears as a basal Paravian outside both the Avialae and the Deinonychosauria, alongside the Scansoriopterygids. As for Samrukia, the phylogenetic analysis shows that it was not quite a modern bird (Neornithes) but pretty close.

More about Samrukia on Tetrapod Zoology by the lead author of the paper himself.

References:

Darren Naish, Gareth Dyke, Andrea Cau, François Escuillié and Pascal Godefroit. 2011. A gigantic bird from the Upper Cretaceous of Central Asia. Biology Letters,  in press.

X. Xu, H. You, K. Du and F. Han. 2011. An Archaeopteryx-like theropod from China and the origin of Avialae. Nature 475:465-470.


Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission.

Xiaotingia zhengi or is Archaeopteryx still a bird?

Fig 1.- A reconstruction of Xiaotingia zhengi.

Xiaotingia zhengi is a new small carnivorous theropod dinosaur discovered in the Late Jurassic Tiaojishan Formation of the western Liaoning province of China. It is known from a single articulated skeleton missing the tail and part of the left leg, and preserved in a slab that also contains some feather impressions.

Fig 2.- Anchiornis huxleyi, a taxon previously described as a troodont, is closely related to Xiaotingia and Archaeopteryx.

The intriguing part of the story published last month in the journal Nature is less the description of the new fossil itself than the resulting cladistic analysis that followed. Xiaotingia was found to be closely related to the famous dinosaur-bird transitional fossil Archaeopteryx lithographica from Bavaria, Germany, and to another taxon described in 2009, Anchiornis huxleyi. Anchiornis had its share of fame last year when it became the first dinosaur to reveal its true colors from the examination of fossilized pigments found in the feather impressions. But Anchiornis was at that time classified as a flying dinosaur belonging to the troodontid family.

Fig 3.- Archaeopteryx lithographica, the "ancestral" bird, was actually a deinonychosaurian dinosaur related to Velociraptor. Note, the position of the wings is too high in this reconstruction.

The new cladistic tree proposed by Xing Xu and colleagues places Archaeopteryx, Anchiornis and the novel taxon Xiaotingia within the same family, the Archaeopterygidae and nests them at the base of the Deinonychosaurians, the group that contains such celebrities as Velociraptor, Deinonychus, Troodon and Utahraptor, and away from the ‘sister” branch (the Avialae) that lead to the modern birds. Archaeopterygidae is then a third and the most basal family that constitutes the Deinonychosaurians, along with the more derived Troodontids (Troodon and friends) and Dromaeosaurs (Velociraptor and friends). The real story behind the discovery of Xiaotingia is therefore that it knocks Archaeopteryx out of the genealogical tree that lead to the modern birds, a position that it held for a century and half! The true ancestors of birds, were more closely related to such oddities as the strange Scansoriopteryids and perhaps other dinosaurs such as the beaked Oviraptosaurs. This leads to the interesting possibility that an herbivorous rather than a carnivorous diet was an ancestral trait for birds.

Fig 4.- Phylogenetic tree of the ancestor of birds and their closest relatives (After Xu et al., 2011). Archaeopteryx does no longer belongs to Aves (Birds in the traditional sense).

As a matter of fact, the position of Archaeopteryx as the ancestor of all birds was precarious for some times now. The close relationship of Archaeopteryx with the Deinonychosaurians has been suspected for quite a while, with such discoveries as the four-winged flying sensation called Microraptor and other small “dromies”. The new cladistic analysis is just confirming a trend that started some two decades ago. Overall the new analysis by Xu and colleagues is making perfect sense: a number of traits that Archaeopteryx possesses are more akin to Deinonychosaurians than to Avialians. Archaeopteryx for instance has a slender shallow snout like the Deinonychosaurians and quite unlike basal avialians such as Epidexipteryx and Sapeornis and Oviraptosaurs who tend to have short and blunt snouts. Many details of the skeletal anatomy, such as the dimension and shape of the different openings in the skull (antorbital fenestra, premaxillary fenestra, …) shape and proportions of different bones (such as the lacrimal in the skull, the pubis, metatarsals, etc…) all point to Deinonychosaurian affinities for the Archaeopterygids.

Now to the vexed question as whether Archaeopteryx could still be considered a bird or not, the most we can say is that it all depends on how you define “bird”. In the traditional sense (as “birds”=Aves), Archaeopteryx is not a bird anymore. But using a broader definition (for instance, “birds”= Paraves (Avialae+ Deinonychosauria)), Archaeopteryx would still be considered a bird, but so should be all Archaeopteryx closest relatives, Velociraptor, Microraptor, Deinonychus and co. Anyway, the fact that a small feathered dinosaur related to Velociraptor could have been mistaken for the  “Urvogel”, the ancestral bird for well more than a century, tellingly shows how intimate the connection between the two groups is. Birds really are the last surviving group of dinosaurs, so get over it and move on, folks!


References:
Xing Xu, Hailu You, Kai Du and Fenglu Han. 2011. An Archaeopteryx-like theropod from China and the origin of Avialae. Nature 475: 465–470.

Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission.