Woo-hoo I’m on a new dinosaur paper. I have got plenty of papers done (I think) but I have yet to be on one naming a new dinosaur so I’m really quite pleased about this, even if I didn’t actually do too much on the paper. This one is coming out in the Chinese Science Bulletin but the paper is already up online so I’m happy to shout about it now before the thing is formally published in the January issue.
As you can see from the picture there is a fair bit of this guy (arms, legs and a partial vertebral column) and with a few feather impressions too, oh and it’s a juvenile, or at least not quite an adult, too. (a) is the main plate, and b) the ‘negative’ counterplate.
Onto the beastie itself and what it means for dinosaur evolution. The full name is Anchiornis huxleyi which roughly means ‘near bird’ or ‘close to birds’ of Huxley (by the way it’s pronounced ‘an-key-ornis’, not ‘anch-ee-ornis’). The fossil is another from the Liaoning beds and thus is the latest in a very long line of important Chinese fossils that relate to the origin of birds (though we don’t know exactly how old this one is). In this case analysis shows that Anchiornis is a basal avialian, that is to say it is on the lineage that leads up to birds, but not actually a bird itself. Fortunately there is a really good reference point for this: Anchiornis comes out in the phylogenetic tree immediately basal to Archaeopteryx, so you can see why it is potentially very interesting and important despite its relative incompleteness as it further narrows the gap between birds and dinosaurs (as if that was not narrow enough already).
The phylogenetic analysis that produced this result is itself quite a big step from previous ones that dealt with this part of the dinosaurian tree. (Unfortunately I have yet to get to my posts on cladistics, so my apologies if I lose a few people at this point). We have included a bunch of new characters and especially those with very fine distinctions in the character states (i.e. small differences applied to continuous characters). This of course risks the problem of character atomisation (over-splitting characters until they are no longer independent and thus cause problems with pseudoreplication of data in the analysis) but the results of the analysis suggest that this has not happened here (at least not yet) since the results are fairly well resolved all things considered. However, it is a reasonable approach with such a group where the number of taxa is building up rapidly with only fine distinctions available between them, and more reversions and convergences appearing.
The presence of Anchiornis (and other new taxa added to the analysis and the new characters) somewhat inevitably narrow the gap between birds and other theropods quite literally by having a number of characters in intermediate states between the two. Importantly it has a highly derived wrist that allows great flexion (or more accurately abduction) allowing the hand to be folded against the lower arm, which is thought to be an important precursor to flight. This is, of course, to be expected from something which is clearly closely related to Archaeopteryx, but the wrist is such an important feature in bird evolution this is an important discovery.
Although this specimen might appear to be a little disappointing, I can tell you that already new material has been recovered that is far better preserved and far more complete and there are several of them. Work is actually at a pretty advanced stage on this so expect a lot more on Anchiornis in 2009 or 2010. I really should add that I did very little on this paper, having been brought onto the project quite late in its development, but I am delighted to have been involved though I have just noticed that my middle initials are missing from the reference even though I did point this out twice. Oh well. Feel free to fill them back in if you wish.
Xu, X., Zhao, Q., Norell., M., Sullivan, C., Hone, D., Erickson, G., Wang, X., Han, F., & Guo, Y. A new feathered maniraptoran dinosaur fossil that fills a morphological gap in avian origin. Chinese Science Bulletin (in press).