Tet Zoo picture of the day # 24

i-6d15154570cfafcb773f07b5bb181e31-Dotternhousen May 2005 resize.jpg

Hello loyal readers: I know you're still there. Yet again I can't resist the lure of posting something new when I really shouldn't. Most of you, I'm sure, think that archaeopterygids - the archaic basal birds of Late Jurassic Germany (and Portugal too if Weigert's (1995) identification of isolated teeth is correct) - are long extinct, but here is evidence indicating otherwise. Ha ha ha. This is actually a monument at Dotternhausen in Bavaria; it's near a bridge that crosses the Altmühl, but I forget the exact location. If you want to see more of those archaeopterygid statues...

... below is a close-up. They aren't exactly the best likenesses of archaeopterygids in the world, but I've seen worse. Note that they have no propatagium, that only two of the three fingers are visible, and that the fingers are deeply immersed in the wing plumage. If I explain why the artist chose to depict the animals in this way, I'll be here for a while, and I regret that that just ain't possible. Some of you might also be wondering why I'm referring to 'archaeopterygids' and not to plain-old Archaeopteryx. Again - for reasons that I'm going to avoid discussing right now - the taxonomy of Archaeopterygidae is somewhat complex, and while it's true that Archaeopteryx lithographica remains the best known taxon, there are a couple of other taxa. The one that's least-familiar to non-specialists is the large Wellnhoferia grandis, named by Elzanowski (2001) for the relatively enormous Solnhofen specimen. While recently accepted as distinct in a revision that sunk all the other species into A. lithographica (Senter & Robbins 2003), Wellnhoferia has more recently been [provisionally] sunk back into A. lithographica by Mayr et al. (2007)... who, however, agreed with Elzanowski (2002) that A. siemensii should be regarded as distinct from A. lithographica. Err, didn't I say that I was going to avoid discussing this right now?

i-93d24e536ff63f460ace5be69b823381-Dotternhousen archaeopterygids.jpg

There are now ten skeletal archaeopterygid specimens, of course, with the newest being the awesome Thermopolis specimen (so named as it was purchased by the Wyoming Dinosaur Center). Described by Mayr et al. (2005, 2007), it demonstrates once and for all that Archaeopteryx had a hyper-extendible second toe and a hallux that was not fully reversed: it really was deinonychosaur-like as Greg Paul and others have been saying, and was not an 'archaic modern-style bird' as Martin and Feduccia have been trying to argue. Again, that's an area I'm going to have to avoid discussing right now. Anyway... back to work.

Refs - -

Elzanowski, A. 2001. A new genus and species for the largest specimen of Archaeopteryx. Acta Palaeontologica Polonica 46, 519-532.

- . 2002. Archaeopterygidae (Upper Jurassic of Germany). In Chiappe, L. M. & Witmer, L. M. (eds) Mesozoic Birds: Above the Heads of Dinosaurs. University of California Press (Berkeley), pp. 129-159.

Mayr, G., Pohl, B., Hartman, S. & Peters, D. S. 2007. The tenth skeletal specimen of Archaeopteryx. Zoological Journal of the Linnean Society 149, 97-116.

- ., Pohl, B. & Peters, D. S. 2005. A well-preserved Archaeopteryx specimen with theropod features. Science 310, 1483-1486.

Senter, P. & Robins, J. H. 2003. Taxonomic status of the specimens of Archaeopteryx. Journal of Vertebrate Paleontology 23, 961-965.

Weigert, A. 1995. Isolated teeth of cf. Archaeopteryx sp. from the Upper Jurassic of the coalmine Guimarota (Portugal). Neues Jahrbuch fur Geologie und Paläontologie, Monatshefte 1995, 562-576.

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I read Feduccas book several years ago (lady at the NHM reccomended it after I emailed asking about aves) it was a fastinating book (I as usual, only understood about half) and his argument about non dinosauran origins were very interesting but smacking somewhat of `already decided`

of course that was before the chinese discoveries....

As a complete aside, another birdie book I likes is Fullers coffee table job on the Great Auk. (every stuffed bird and egg catalogued in eyewatering detail.) did you know that each bird had an individualy patterned egg for easy identification, repeated year after year?? How did they do that??

Because they cant fly, Iceland air give them free seats.

Ten specimens, all from the same location and time. I'm doubting there's anything but a single species of Archaeopteryx gliding around the Solnhofen lagoons. Size differences could simply be explained as differences in the growth patterns between early birds and crown-ground birds. Perhaps Archaeopteryx, Jeholornis, and Confuciusornis had a more clasically reptilian growth rate, and "Wellnhoferia" is merely an old, large individual.
I know that one of the smallest specimens, and the only one with a preserved sternal plate, was named "A. bavarica" based on its miniscule size and present sternal plate, that to me, it's more likely that A. bavarica represents a young individual whose sternal plate was preserved. To say that Archaeopteryx lacked a sternal plate is to ignore its phylogenetic position. Archaeopteryx HAD a sternal plate, but that bone will not always fossilize given its size and the low density of the bones.

Certainly Wellnhoferia does not represent a genus-level distinction. At the very most, it's a subspecies separation, like the modern brown bear and Kodiak brown bear. Exact same animal, but the Kodiak bear is significantly larger. However, again, there's the issue of geographic isolation with the Kodiak bear--it is restricted to Kodiak and its neighboring islands (the bears can actually swim between them with ease). Archaeopteryx and "Wellnhoferia" lived in the same place and probably would have competed for the same living space.

A specimen that's a little bigger than the average specimen does not necessitate the coining of a new genus (or species). Taxonomic over-doing-it is a subject I feel quite strongly about...

Zach: the specimens aren't all exactly the same age. The 9th specimen (the 'Steinberg quarry' specimen) is older, for example (it wasn't assigned to a species in the most recent revision). The alleged sternal plate of A. bavarica turned out to be a misplaced coracoid, and this taxon has most recently been sunk into A. lithographica. And Wellnhoferia wasn't only named for its size, but also for a shorter tail and different pedal phalangeal formula... though how significant these differences were have since been challenged.

As for the idea of multiple species, don't forget that these animals were inhabitants of an island archipelago, exactly the sort of place where we get species radiations.

To add to Darren's comments - you also get cryptic species. Palaeo species are not the same as zoological ones for the simple reason that with rare exceptions we are dealing with bones alone. If you took a group of birds like tits in Europe and *just* examined the bones would you identify the dozen (ish) species without differences in colour, song, habitat etc.?

From a practical (palaeo) point of view there are probably only one or two Archaeopteryx species, but if they were alive today there may well have been several by the standards we use for birds.

I keep forgetting that western Europe was mostly underwater during the dinosaur days. But the brown/Kodiak bear analogy remains the same--the same animal on neighboring islands constitutes the same genus and species--it's a subspecies-level distinction. Of course, as my friend Scott keeps reminding me, all taxonomic distinctions are arbitrary. I didn't realie that "Wellnhoferia" had a different pedal formula, but that could be pathologic or simply an individual difference. Or, hey, it could be a separate species/subspecies.
Of course, a quick review of the current status of Darwin's finches, which exist along an archipelago (of sorts) informs me that the birds are actually split into two genuses and several species and subspecies.

Ah, who knows. We need more specimens. ;-)

Dr Naish, would you be willing to explain something to an entirely ignorant amateur?

When I was a kid many years ago, every popular discussion of Archaeopteryx stressed that if the original Solnhofen specimens hadn't retained the feathers, it would simply have been regarded as a rather unexciting little coelurosaur. But since those far off days, we've had feathered maniraptors coming out of our ears, so should it in the light of this really be regarded as in fact a rather unexciting little coelurosaur?

I suppose what I'm getting at is, what features of Archaeopteryx, other than sentimentality, keep it assigned to Aves rather than some other manoraptoriform clade? And is there any reason to suppose it could fly at all, as opposed to gliding, which is all that is ever conceded to Microraptor, or swimming under water with its forelimbs like a murr, as I've seen suggested?

Hi Chris - thanks for your question(s). I'll try and keep my answer brief. I can also recall reading that, were it not for its feathers, Archaeopteryx would have been identified as a Compsognathus [indeed this claim was key to the Hoyle & Wickramasinghe nonsense about Archaeopteryx being a fake]. But, with all due respect to the workers concerned, I think that the people saying this had only looked at the fossils in a very cursory/superficial manner (and such is demonstrated by the misidentification of the Eichstatt Archaeopteryx specimen).

Archaeopterygids are clearly not 'modern-style' birds - they're very similar to deinonychosaurs - but they still exhibit a number of detailed characters that aren't present in most other coelurosaurs and appear to be synapomorphies of birds: most studies that have good sampling across taxa and characters do find archaeopterygids to be stem-group birds, while the very bird-like feathered microraptorians and so on are deinonychosaurs and not part of Aves/Avialae. There is tons more than could be said about this, I'll have to leave it there for now. What are these avian synapomorphies? They include a tail of less than 25 caudal verts, a proportionally long humerus, and a reduced pubic apron.. certainly nothing 'special' or 'major' like 'presence of feathers'.

As for whether Archaeopteryx and kin could fly, there are indications from its reconstructed wing size and musculature that it could, and that it was reasonably good at it... but let's see if Scott Hartman is around :)

One last thing: there is no doubt that Archaeopteryx is highly over-rated: you're right, when it was alive it would have been just one of many highly similar feathered maniraptoran lineages, all of which were equally neat. We tend to think of Archaeopteryx as a really special and interesting animal, but only because it has living relatives, and that ain't so for troodontids, dromaeosaurids and so on. I wonder how different things would have been had a feathered Microraptor been discovered during the 1800s?

Thank you. That does clarify things for me. The avian synapomorphies you cite are the sort of data I like, because they're both measurable and individually unimpressive, which is what I'd expect in a beastie of that age.

Just me busting in again. I'm lucky enough to work in the BSPG in Munich and should you ever get the chance to come over you can compare Compsognathus to the Munich archaeopteryx and see just how little (relatively of course) they have in common.

While I agree with Darren to an extent that it is overrated, I would argue that its age, completeness and the fact that we have so many of them maintain it as an important taxon. If nothing else from a public perspective, the Berlin specimen is probably the single most recognisable fossil in the world.

I think that primitive deinonychosaurs are just as deserving of Archaeopteryx to be "basal Aves." I think Microraptor has a caudal count that's not for-surely known, but seems comparible to Archaeoptyerx. And although this could be an artifact of preservation, dromaeosauroids have ucinate processes while Archaeopteryx seems to lack them.
As for Archaeopteryx the flier, I just read a paper by Phil Senter in which he claimed that primitive birds like Archaeopteryx, Jeholornis, and Confuciusornis were unable to lift their arms above the horizontal, thus making a complete flight stroke impossible.
Finally, what are everyone's thoughts on Jeholornis? Toothy maw, long bony tail...it almost seems like a Chinese archaeopterygian.

The alleged sternal plate of A. bavarica turned out to be a misplaced coracoid

Part of a coracoid in fact -- a coracoid of normal maniraptoran proportions (large and square), not narrowed bird-style.

By David Marjanović (not verified) on 29 Jul 2007 #permalink

Don't those fossils found in China, coeval with Archaeopteryx but much more birdlike, mean that the latter can't reasonably be considered ancestral to anything?

By Nathan Myers (not verified) on 29 Jul 2007 #permalink

Nathan: I assume you're referring to the amazing fossils from the Jehol Group of Liaoning Province. They aren't coeval with Upper Jurassic Archaeopteryx [contra early claims from Chinese workers that they were], but date from the Lower Cretaceous. This has been fairly reliably established on the basis of radiometric dating.

The diversity of stem-group birds in the Jehol Group is astonishingly high, but all the taxa we know of seem to be closer to modern birds than were archaeopterygids. That goes even for long-tailed Shenzhouraptor and the other jeholornithids: they have several characters, including a reduced dentition and a fused dentary symphysis, that pull them up towards pygostylians (the short-tailed avian clade that includes confuciusornithids, enantiornithines, crown-group birds and so on). They don't exhibit shared derived characters that allow us to put them in a clade with Archaeopterygidae.

There is something that prevents us from considering Archaeopteryx ancestral to anything known: its autapomorphies = derived characters that its closest relatives all lack. Contrary to many early claims, it has a few of those. Unless it gained and then lost them all again, which would be a rather large set of ad hoc assumptions, it can't be an ancestor of anything known.

By David Marjanović (not verified) on 30 Jul 2007 #permalink

Dave Hone wrote:

If nothing else from a public perspective, the Berlin specimen is probably the single most recognisable fossil in the world.

You mean the Berlin specimen of Brachiosaurus, right?

Darren wrote:

Most studies that have good sampling across taxa and characters do find archaeopterygids to be stem-group birds, while the very bird-like feathered microraptorians and so on are deinonychosaurs and not part of Aves/Avialae.

Well ... since all dinosaurs are stem-group birds (i.e. more closely related to birds than to any other extant form) it's not particularly exciting that this is true of archaeopterygids.

For Chris Y., who first asked the question about Archaeopteryx's inclusion within Aves: this is a complicated issue because there are so many candidate definitions of Aves floating around. For a brief summary, see the two questions (really a single thread) at the Ask A Biologist site:

Yeah yeah... I should have said 'Most studies that have good sampling across taxa and characters do find archaeopterygids to be basal members of Aves/Avialae'.

And they are the coolest Dinosaura ever

Yes, except that the position and monophyly of the "jeholornithids" is unclear, and that there are plenty of clades that are closer to the crown than Enantiornithes is.

By David Marjanović (not verified) on 12 Aug 2007 #permalink