Dasornis emuinus
Described September 26 in the journal Palaeontology, the skull belongs to Dasornis emuinus, a bony-toothed bird, or pelagornithid, and was discovered in the London Clay, which lies under much of London, Essex and northern Kent in SE England. The occurrence of bony-toothed birds in these deposits has been known for a long time, but the new fossil is one the best skulls ever found, and preserves previously unknown details of the anatomy of these strange birds.
With a five metre wingspan, these huge birds were similar to albatross in their way of life. Albatross have the largest wingspan of any living bird, but that of Dasornis was over a meter and half greater. Despite these similarities, the latest research suggests that the closest living relatives of Dasornis and its fossil kin are ducks and geese.
“Imagine a bird like an ocean-going goose, almost the size of a small plane! By today’s standards these were pretty bizarre animals, but perhaps the strangest thing about them is that they had sharp, tooth-like projections along the cutting edges of the beak” explains Gerald Mayr, expert palaeornithologist at the German Senckenberg Research Institute and author of the report.
These were not true teeth but bony projections of the beak, functioning as teeth, probably to catch fish.
Skull of Dasornis emuinus with projected beak
Birds no longer produce teeth: they have the genes to do so but teeth do not develop in the absence of bone. So Dasornis developed a functional substitute. The Dasornis’ tooth is like the panda’s thumb.
Journal reference:
- Mayr et al. A skull of the giant bony-toothed bird Dasornis (Aves: Pelagornithidae) from the Lower Eocene of the Isle of Sheppey. Palaeontology, 2008; 51 (5): 1107 DOI: 10.1111/j.1475-4983.2008.00798.x
Tuesday, 30 September 2008 at 11:07
Amazing! In our introductionary Zoology class, we learnt that birds don’t produce teeth anymore as part of their adaptation to agility and the need to balance powered flight. I wonder if these bony projections are hampering their abilities to fly as much as ordinary teeth do. In that case, it begs the question: how come these birds could even evolve them?
Tuesday, 30 September 2008 at 11:21
A couple of things. The summary article said “bony,” but I think that was used to mean “hard and rigid” not “made of bone.” And we know that dinosaurs had the capacity to make beaks, e.g. Triceratops. So I think that these “bony” bumps are actually horny bumps. But even little bumps of bone wouldn’t be as heavy as rooted teeth. The Science Daily article links to the original paper so you can check out hte details.
One other little thing. It raises the question. Unfortunately, “to beg the question” is a special term from rhetoric for a bad argument. It actually means to assume your conclusion, e.g. calling a fertilized egg a baby.
Tuesday, 30 September 2008 at 11:42
Well, you can’t blame me for confusing “bony” with “made of bones”. At any rate, it’s just the same if it’s a rigid apparatus used to grinding and chewing – it’s heavy and not particularly aerodynamic – which is why birds “devolved them” in the first place. If it’s “okay” for them to have “lighter teeth”, I’m not sure why they wouldn’t simply devolve teeth to “vestigial teeth”. But they didn’t.
Sorry about the English blort, I’m Israeli and sometimes my English goes a bit fickle.
Tuesday, 30 September 2008 at 11:59
I puzzled over “bony” myself but decided it couldn’t mean real bone. Now I have to go read the paper to make sure.
Believe me, 90% of the time when I hear “begs the question,” it’s used in exactly the way you used it.
Tuesday, 30 September 2008 at 12:31
Oh. I got English just fine and dandy even though I’m Israeli, but I sometimes use saying and idioms wrong. I never do such embarrassing mistakes twice, though :-)
BTW, I think it’s probably not regular bones, definitely not teeth, but if it’s not, then I’m a bit puzzled: If birds devolved teeth to get lighter, could they have “re-evolved” horn-like “teeth”? If these teeth are used for predation, it means they were used for smashing and chewing, right?
At first, when I saw the huge wingspan, I figured that maybe these birds could afford “re-evolving” teeth (panda’s thumb or not) if their huge wingspan allows them powered flight anyway, with the encumbrance of teeth-like apparatus or not, with the added bonus of having a much more varied diet.
It’s probably more likely than backmutating every mutation that’s occurred to cause them their loss of their original teeth.
Tuesday, 30 September 2008 at 12:41
You’re probably right that a big bird like that could carry a few teeth without plunging into the ocean. I sure hope so, because I cringe every time I see eager researchers strapping onto some poor animal or bird a radio beacon that probably adds 5 or 10% to its body weight. Don’t they know how slim the margins of survival are?
Teeth are much denser than bone, so they’d add more weight. Many, many fish-catching species have small, sharp teeth or serrated beaks for grabbing the fish, which they then swallow whole.
However, I wonder how the researchers came to their conclusion when I see that they’ve simply drawn in a beak. The bone beds must contain fragments of beaks at least to let them know the beak shape.
And you’re right again. The point of the panda’s thumb is that once something is gone we are not likely to re-evolve it.
Thursday, 2 October 2008 at 02:46
Hmm, so there ARE fish-eating birds? Whole-fish? How are they able to eat the fish without cutting and crushing their prey? Do they have to use external digestion prior to the internal digestion?
Your examples of fish-eating birds pretty much clarified the issue for me. Also, considering the fact that birds have evolved hollow (or should I say, hollow-er) bones, I’m assuming that it’s possible for birds to evolve “hollow bony teeth” – which would do well to mitigate the weight problem I brought up before.