Microraptor: not a ‘raptor’??

Earlier
the large reptile tree nested two putative dromaeosaurs with composgnathid/tyrannosaurs, Tianyuraptor and Zhenyuanlong. Today the famous four-wiinged dinosaur/bird Microraptor (Figs. 1, 2) is added to that list, nesting between Compsognathus and Tianyuraptor, all three basal to T-rex.

Figure 1. Microraptor gui (IVPP V 13352) shown in two photos and with DGS tracing of bones and feathers.

Figure 1. Microraptor gui (IVPP V 13352) shown in two photos and with DGS tracing of bones and feathers. Click to enlarge.

This is the specimen
that inspired a PBS Nova special and a race between competing teams of paleontologists to figure out the best usage for the odd foot feathers. The Kansas team led by Dr. Larry Martin produced a sprawling model that went against everything we know di dinosaur hind limbs.

Figure 2. Microraptor gui (IVPP V 13352) reconstructed from tracings in figure 1. There are no surprises here, except a provisional closer relationship with Compsognathus than with Velociraptor. Microraptor has a large pedal claw two, but it is not quite the killing claw seen in droamaeosaurs.

Figure 2. Microraptor gui (IVPP V 13352) reconstructed from tracings in figure 1. There are no surprises here, except a provisional closer relationship with Compsognathus than with Velociraptor. Microraptor has a large pedal claw two, but it is not quite the killing claw seen in droamaeosaurs.

So this makes three former dromaeosaurs
now nesting with long-legged Compsognathus and Tyrannosaurus. Among them, only Microraptor has long arms/wings. Zhenyuanlong has equally substantial feathers. So this adds credulity to the idea that Compsognathus was well feathered. Only Microraptor has a posteriorly directed pubic foot, but see Compsognathus (Fig. 4) for its derivation. This is not a posteriorly directed pubis.

Figure 4. Compsognathus was not preserved with feathers, but with a sister taxon like Microraptor, it might have had substantial feathers.

Figure 4. Compsognathus was not preserved with feathers, but with a sister taxon like Microraptor, it might have had substantial feathers.

Is Microraptor a bird (clade Aves)?
Wikipedia (Evolution of Birds) defined Aves as “all descendants of the most recent common ancestor of a specific modern bird species (such as the house sparrow, Passer domesticus), and either Archaeopteryx, or some prehistoric species closer to Neornithes (to avoid the problems caused by the unclear relationships of Archaeopteryx to other theropods).[ If the latter classification is used then the larger group is termed Avialae. Currently, the relationship between dinosaurs, Archaeopteryx, and modern birds is still under debate.”

Is Microraptor a member of the clade Avialae?
Wikipedia defines the clade Avialae “a clade of dinosaurs containing their only living representatives, the birds. It is usually defined as all theropod dinosaurs more closely related to modern birds (Aves) than to deinonychosaurs, though alternate definitions are occasionally used (see below).” 

So, Microraptor is not a bird. 
In the same light, not all Archaeopteryx specimens are birds, but Wellnhoferia (aka The Solnhofen specimen, Archaeopteryx grandis) apparently is a bird as it nests closest to living birds of all Solnhofen specimens.

Yes
I don’t have a complete list of theropods in the large reptile tree. But this is what the tree recovers at present. If valid, theropods with long feathers on their forelimbs appear earlier than some workers think. And maybe I’m just catching up to the rest of them.

There are other specimens out there referred to Microraptor
and I have not tested them yet. Perhaps one or more are more closely related to Velociraptor. 

Addendum
Here is the skull of the QM V 1002 specimen of Microraptor (Fig. 5, Xing et al. 2013). The two nest together in the large reptile tree, but differ in several traits. They are not conspecific.

Figure 5. The skull of another Microraptor, QM V1002. The two nest together in the large reptile tree.

Figure 5. The skull of another Microraptor, QM V1002, the fish eater. The two nest together in the large reptile tree. I’m a little confused by the occiput. I’ll get back to that later.

References
Xing L, Persons WS, Bell PR, Xu X, Zhang J-P, Miyashita T, Wang F-P and Currie P 2013. Piscivery iin the feathered dinosaur Microraptor. Evolution 67(8):2441-2445.
Xu X, Zhou Z, Wang X, Kuang X, Zhang F, and Du X 2003. Four-winged dinosaurs from China. Nature, 421: 335–340.

wiki/Microraptor

 

 

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