Monday, October 27, 2008

Opinions on Les

Okay, thanks to Chris Taylor, I now have that Epidexipteryx paper in my meaty paws. I am working on a restoration (well, not right now), but I need some help. I need some opinions. Here is what I've decided I am going to do:

1) It's gonna have a long third finger. The one hand that is preserved in the fossil is not preserved well, but there's a good rationale for a long third finger based on the measurements of the first two bones of Digit III (read this on Tet. Zoo).

2) It's gonna have "fuzzy" feathers in the manner of Sinosauropteryx and Caudipteryx. I still have no idea what the authors mean when they say "membraneous structure." Does that mean that a whole bunch of feather filliments are arising from a single point, but held together at their base by some kind of membrane? That doesn't make any sense, and doesn't really jive with what we know about how feathers grow.

3) The elongated tail feathers are not going to be terribly rigid, but flowing and flexible, as I imagine they were in confuciusornids.

4) It will have a fully-reversed hallux, as Scansoriopteryx does.

Now, here are my questions. I encourage discussion here.

1) What should I do about the tail? Scansoriopteryx has a very long tail, but Epidexipteryx seems to have a really short one. As I learned on the DML, a break is possible where the "middle section" of the tail was lost. However, I just don't see that. The fact that the "snapped off" section of tail is so very close to the articulated section seems (to me, anyway) to imply that there's not a whole lot missing, there. On the other hand, it would also be strange that Scansoriopteryx and Epidexipteryx, which are sister taxa, have such wildly different tail lengths.

2) Should I give Epidexipteryx "flight feathers" along its arms? I know they weren't preserved in the fossil, but absence of evidence is not neccesarily evidence of absence. The animals directly below (deinonychosaurs) and above (birds) Epidexipteryx have contours along the arm, so why would this new animal lack them?

3) How do you think that long third finger would be carried when not in use?

Thanks for the help!


Christopher said...

First of all absolutely do not give it a fully reversed Hallux. Despite what you may have read, like everywhere, Scans does not have one and neither would LES. And for the same reason no other non avian dinosaur has one. Metatarsal I needs to be twisted.


Theres a lot more about this subject on the DML but I got tired trying to find the best explanations. Jaime's is good enough and its topical!

On to the feathers. Scans does preserve feathers of some sort along the wing, they're just not pennaceous remiges. Rather they look like the same sort of shaggy primitive feathers the rest of it was covered in but longer. And I wouldnt write Epidexipteryx off from having the same sort of wing. I dont even think we can say that "they werent preserved" given that the manus was preserved over the center of the body they could be hiding in the body feathers, or prepped away. As for rigidity of the tail feathers, IDK but the ones of Confuciusornis appear to have been quite rigid.

As for the presence of an elongate third finger, I was initially unsure but I eventually came to the same conclusion as Mickey. I really doubt it was as flexible as the finger of an Aye-aye, but there would need to be some serious bio mechanical work done first to say any thing definitive. I would imagine its held just like any other finger. its just there hanging off the rest of the hand not doing anything special.

Christopher said...

Zach, you should join up at A lot of your questions would easily be answered.

Christopher Taylor said...

A couple of thoughts that occur to me:

As I tried somewhat clumsily to say in an earlier comment, the different selective pressures on feather form in flighted vs. flightless taxa mean that there is more potential for variation in the latter, so it would be unusual but I suspect not impossible for Scansoriopteryx and Epidexipteryx to have different feather forms. Consider the differences between ostriches and emus, for instance.

As regards the elongate third finger, I would have thought (in my non-expert way) that this would have been less of an issue for maniraptorans than mammals, because the tight bird-style arm-folding mechanism would mean that when the arm is folded back the fingers could be safely held flat against the body.

And as for difference in tail lengths, just look at the variation between various Macaca (macaque) species, in which there is the full range of variation from long-tailed to almost tailless species, even between quite closely related species.