Thursday, July 22, 2010

Amazing Jehol Art and Microraptor Tailfins


Just a quick note on something I stumbled upon while checking out the new google image search. These paintings by Zhang Zong Da (click here!) are seriously cool, some of the most effective art I've seen portraying the Jehol and Dauhugou biota. My favorite is the third image down depicting pollinating insects. Reminds me of Microcosmos or something, an aesthetic I've tried for with some of my own digipaintings but not nearly at the same level of skill or effectiveness.

One idea I particularly like (and wonder why I haven't seen more often) is the Microraptor with "tailfins" like a '57 Chevy. As we all know, microraptorians had long pennaceous feathers not only on the metatarsus but the tibia (and the thigh in some cases, known as "butt fans"). All gliding micro restorations I've seen have the tibiae fully extended, creating a wide gap between the sticky-out biplane feathers of the metatarsals and the front wings of the arms. The restoration above shows the legs in a 'kneeling' posture, so that the tibia feathers stick more or less straight up behind the front wings, presumably creating a stabilizing effect. I don't know how aerodynamically sound this configuration would be, but it sure is a cool idea!

Monday, July 19, 2010

The Primaries and Secondaries of Caudipterids

Above: Classic Caudipteryx model, from National Geographic.

There's a lot going wrong with the Caudipteryx model pictured above, once prominently featured on the cover of a 1997 National Geographic. But maybe not as many things as you'd think.

Ever since I started drawing prehistoric animals for serious, I've been on a crusade to see that it's done right. Too many people draw feathered dinosaurs with zero background knowledge of how wings and feathers are put together or appear in life. One of my biggest pet peeves has been drawings of Caudipteryx which give it secondary feathers. That is, remiges that stem from the ulna. You see, Caudipteryx was one weird dinobird. It had fairly puny wings compared to its body size, with primary feathers only a little longer than the length of the hand. And, apparently, no secondaries. This gives the effect of small, narrow wings good only for flicking out in possibly short displays of small color flashes. All this is based on the holotype specimen of the type species, C. zoui. See my recent reconstruction above right.

However, I recently (finally) got my hands on the descriptions of the referred C. zoui specimen, C. sp., and C. dongi. The referred specimen of C. zoui (BMP 0001) shows the exact same arrangement of feathers as the type. C. dongi, on the other hand, aside from some subtle differences in postcranial proportions that may or may not allow it to be placed in a separate species, has something else: secondary feathers. Check it out:

Above: Portion of plate 1 from Zhou & Wang, 2000.

The photo is pretty poor quality, but you can clearly make out feathers coming from an area inboard of the wrist. The accompanying line drawing makes it more clear:

Above: Portion of figure 1 from Zhou & Wang, 2000.

Notice that in the photo, you can make out possible remains of a tightly banded color pattern also evident in the tail of the C. zoui holotype, but only on the secondaries.

So could C. dongi merely be a growth stage of C. zoui with extra wing feathers? Thanks to two specimens of Similicaudipteryx yixianensis (which are nearly identical to C. sp. in size, proportions, skull shape and even feathering), we know that at least some caudipterids possessed only primaries when they were juveniles and grew secondaries as they matured (the C. sp. specimen also has secondaries in the same proportional size). However, C. zoui is larger than the C. dongi specimen (and the secondary-possessing Similicaudipteryx/C. sp. specimens), so even if it is immature, it must be an immature specimen of an even larger species.

Keep in mind this is all based on published figures and rather poor photographs, so at the risk of sounding like Dave Peters, it would be great for someone with access to the physical specimens to confirm or deny this stuff. Sadly, very little about the actual feathers of the various specimens has been described in the lit, except for the holotype specimen, and even there, seemingly important things like the color bands are only mentioned in a figure caption. At any rate, feather coloration, length, and extent should be kept in mind when trying to determine which of these things, if any, represent distinct species.

Thursday, July 15, 2010

Chicken vs. Egg


Above: Whichever came first, they're equally delicious. Egg photo by Fir0002/Flagstaffotos, licensed. Chicken photo by 3268zauber, licensed.

Today I read possibly one of the dumbest science news articles of all time, or at least the most condescending. Somewhere in here is news of an interesting study. English scientists have isolated the protein responsible for the formation of hard-shelled eggs in chickens, a step forward in developmental science that could potentially yield applications for materials science. So, how to make sure this mildly interesting study grabs the attention of Joe Six-pack? Put out a press release to every major media outlet claiming to have solved the "age old problem" (really?) of which came first, the chicken or the egg?

The Chicken and the egg: Ancient mystery solved?

Not only is this silly eyeball-grabbing headline a blatant attempt to pander to the lowest common denominator and point out what a complete joke science reporting has become, it assumes the absolute worst about the reader's level of science comprehension and interest. And it's obviously completely wrong!

The articles in question "argue" that because a protein for forming eggshells is found inside chickens, this proves that the chicken came before the egg.

Not only is this severely flawed logic, you don't need a discovery to prove the answer one way or the other: If you really want an answer to this rhetorical philosophical conundrum, it's obvious using simple logic and knowledge of how evolution works.

Let's define some terms first. I think implicit in this old riddle is the fact that we're talking about chickens Gallus gallus and chicken eggs here, specifically.

Nothing in the report suggests that proteins for hard shells originated with modern chickens. In fact, we know from observation that all other bird species, including those more primitive than chickens, lay hard-shelled eggs (though as PZ Myers points out in the link below, they often use a different protein). We know based on fossil evidence that hard-shelled eggs were laid by not only non-avian theropods but also sauropods and ornithischians. In contrast, softer shelled eggs are found in crocodilians and pterosaurs. So we know that the hard-shelled egg this protein (or the genes coding for it or similar proteins) allows evolved among ornithodirans sometime after pterosaurs diverged but before ornithischian and saurischian dinosaurs split. So, let's ballpark it to the early-mid Triassic period for the appearance of hard-shelled eggs. Even allowing for the broadest possible definition of "chicken" (Galliformes), the earliest you can say chicken-like creatures walked he earth is the late Cretaceous, when the stem-anseriform Vegavis lived (so we know that the chicken line must have split from the duck line by that time).

That covers the hard shelled egg in general, which clearly came long before the chicken. What about modern chickens specifically and their eggs? This gets down to the biological species concept, of which there are many and they all overlap. Is a chicken anything that can successfully breed with any random clucker down at the farm? If so, we're getting into some sticky concepts of ring species and sub-species here, which just muddy the waters, especially when ancestral species are taken into account. Let's just say for our purposes, a "chicken" means the type specimen of Gallus gallus domesticus, and its specific genome. The species this bird belongs to, however you define it, diverged from an ancestral population that we can say was non-chicken. The relevant mutations or changes in allele frequency that define the line between chicken and non-chicken almost certainly did not occur inside the living adult non-chicken and were then passed on to its offspring in some kind of Lamarckian evolutionary event. Rather, they would have taken place in the cell divisions leading to the formation of the first true chicken egg.

Put more simply, a non-chicken did not spontaneously transform into a chicken via some kind of Fantastic Four style cosmic wave, and it did not spring spontaneously with all its essential chickenness in place from the head of Zeus. Rather, a non-chicken had to have laid an egg containing a chicken embryo. Can this be said to be a chicken egg, if it was laid by a non-chicken? I'd day yes, as it contains a chicken. Though ultimately, maybe this classic paradox is better left to philosophers after all.

PZ Myers of Pharyngula has done his own write-up on this travesty of science reporting and goes into more detail on the protein angle, well worth a read here. PZ says that "you simply can't make the conclusion the reporter was making here" but, given the prevalence of this exact conclusion in other articles from other news sources, everybody is simply copying one idiot science writer or, more likely, this conclusion was actively promoted by a press release. I can't decide which would be worse.

EDIT: This is getting hilarious. No, not the plethora of tragically inevitable comments from creationists, but watching the American media slowly realize that every single one of their science writers who allowed this nonsense to be repeated on their pages are being laughed at by people who took middle school biology, even in their own comments. Case in point: A single editor's note has been made on the CNN Article headline: "Maybe." Not, "Sorry, our so-called journalists are too stupid to recognize an obvious load of crap when they see it, or at the very least point out the crap being served to them in press release form. The people responsible have been fired and we're hiring a literate this time."

Just, "Maybe. Maybe not. Reality: you decide!"

*head-desk*

Wednesday, July 14, 2010

Reign of the Dinosaurs

Above: Promo image via Slashfilm.

Man, I picked the wrong time to move out of San Diego.

At Comic Con this Friday, Discovery Channel is hosting a panel consisting of artists who are working on a new show called Reign of the Dinosaurs, a Walking With Dinosaurs style drama/documentary being produced by a company called Creative Differences, including several former Pixar animators (some initial reports erroneously said Pixar itself was producing the show). It's currently scheduled to debut in 2011. Scott Hartman announced this on the DML today, and I'm assuming this is the project he's been waxing mysterious about on the message boards lately. Along with Scott, the project is working closely with several notable artists including paleoart/sculpture god David Krentz (and it sounds like he's even getting his mosasaur sequence so heinously excised from the aborted, naturalistic version of Disney's Dinosaur).

In my opinion these kind of top grade dinosaur shows need to happen at least once per decade, for the good of humanity (or just my personal sanity). WWD was hugely influential, but it's now 11 years old so it's also hugely outdated. Many casual paleo fans may not be aware of this, and a good high-profile TV special like this can help inject some new discoveries into the public consciousness the way press releases on the AP via Google News just can't. Looking at the talent involved, it would take some MAJOR intentional meddling to screw up the accuracy of this show. Just reading the press release, found here, is getting me amped for this thing, especially assuming it follows the WWD pattern of featuring one ecological community per episode. You've got the old standbys like T. rex and Therizinosaurus (though it is kind of amazing Therizinosaurus can be considered an old standby these days), but it also promises to feature a "giant, dinosaur eating frog" (i.e. Beelzebufo, and presumably the rest of the LK Malagasy fauna like Rahonavis and Masiakasaurs, all of which have never appeared in animated form as far as I know, except maybe on Dinosaur Train), and, get this:

A "Jurassic flying squirrel."

Hear that? That's Volaticotherium. We're getting the bloody Daohugou Biota on TV. Castorocauda, Scansoriopteryx, Tianyulong, Darwinopterus, Anchiornis, and Daohugocorixa (though maybe I'm the only one excited about that last one). Eat it, Yixian. Though there does appear to be a Caudipteryx on the promo poster, so maybe we're getting both? A man can dream...

Oh, and given the Allosaurus featured on the poster and the involvement of Scott Hartman, could this be the first television appearance of a certain Morrison formation troodontid?

I'm hoping the ComiCon panel will show up on YouTube, and I'll report any further details that may get leaked.

Monday, July 5, 2010

Tall Tail


This may be old news for those who attended last years SVP meeting, but news of this is (to my knowledge) breaking for the first time online. Matthew Herne has finished a complete osteology of the Australian ornithischian Leaellynasaura, abstract here: http://www.vertpaleo.org/meetings/SVPProgramAbstracts09WEB.pdf.pdf

A few surprising things here. First, Leaellynasaura is traditionally called a hypsilophodontid, or at least basal ornithopod. This study finds that it's even more basal among ornithischians, even sharing some characters with thyreophorans, so it's best placed as a basal genasaurian. Next, the tail lacks the distinctive lattice of ossified, stiffening tendons found in members of many ornithischian clades. Instead, the postzygapophyses of the tail are greatly expanded relative to other members of this order, which may have helped stiffen the back half of the tail.

Most surprisingly, the tail itself is apparently ridonkulously (technical term) long. Leaellynasaurua has over 70 tail vertebrae, more than any other ornithischians save some hadrosaurs, but more astounding is the total length of the tail, which made up 75% the total body length, being three times longer than the torso, head and neck combined. Why such a long tail? One idea floated by Dann Pigdon on the DML today is that if Leaellynasaura had a covering of filamentous feather or fur-like integument (as seen in Psittacosaurus and Tianyulong), it may have been able to use its tail for warmth during cold antarctic nights, wrapping the tail around the body like an arctic fox. It may have also been useful for territorial signaling or mating displays, especially if (as in most animals with filamentous or feathery coats) it could puff the tail up to an apparently larger size by raising its hackles.

I couldn't help taking a break from my Yixian field guide series to try restoring this hypothesis, and the results are above. Can't wait to see this paper officially in print!