Here is our response to the Limusaurus paper. It was recently rejected by nature, not for any technical reason but because it was considered not to be of sufficient interest/importance.

We have uploaded it at the nature precedings citable archive, because we think it is important there is a quick and citable reply that unlike Xu’s proposal, is consistent with the view of the larger community of theropod paleontologists, namely, that tetanuran digits still are I, II, III. We are preparing a longer paper on this topic.

Keep up the great work!

Peter from Gansu, China

Thanks for stopping by. I remember Feduccia was claiming that the evo-devo research he had cited showed a 2-3-4 digit arrangement, and for him, that clearly disproved dinosaurian ancestry (In the interest of full disclosure, I am a former invertebrate paleobiologist, so it’s not really clear to me why Feduccia thought this was relevant.).

Appreciatively yours,

John

In a typical phylogenetic analysis one simply identifies characters that differ among species, more or less assuming that you know what it is you should be comparing. But here, obviously, the question was where to start in making comparisons. We couldn’t simply have a character, “Manus digit I, with no phalanges (0) one phalange (1) or two phalanges (2)” without being sure we knew which digit is the first one in each tetanuran.

This is a problem that is largely ignored by morphologists, with a few exceptions such as Martin Ramirez, Olivier Rieppel, and my former student Maureen Kearney. The approach we took is one that is more common in molecular sequence analysis, such as the program POY by Ward Wheeler, where alternative primary homology statements are compared against one another, to see how congruent different primary homology hypotheses are with other characters. We therefore coded ceratosaurs and each major group of tetanurans as either 1-2-3 or 2-3-4 and compared the results. If birds are indeed 2-3-4 then it is far simpler for all tetanurans to be 2-3-4 than the alternative.

Now to bring it around to missing links – at the level of character analysis there are certain taxa, such as Limusaurus, that change primary homology statements by showing some kind of intermediate condition. In some sense these forms can be considered to provide missing links between homologies.

In closing I need to add that Xu Xing was the primary author and the person who realized first what was going on with this animal, but because he is in the field right now he isn’t available for interviews, so I have been the spokesman for the paper this week.

Beg your pardon? I’ve dropped by here before, and with good reason. Consistently Carl has had the best entries I have seen with regards to evolutionary biology. His latest on Limusaurus is a classic example for two reasons:

1) It is quite succinct and therefore gets to the point.

2) Carl does a much better job than, for example, a certain “evo-devo” biologist blogger in explaining why this discovery is important to the average, interested layperson.

As for my previous comment, Alan Feduccia is an ornithologist at, if I’m not mistaken, University of North Carolina, Chapel Hill. He is also among the very few who still doubt the dinosaurian ancestry of birds. A few years ago I heard Feduccia give a talk in which he claimed he had “evo – devo” evidence refuting the now robust hypothesis first proposed by the late John Ostrom (although, to be historically correct, the very first one was none other than Thomas Henry Huxley) that birds are living descendants of small theropod dinosaurs.