UPDATE: In light of new data and criticism of this paper, it has been retracted. The “dinosaur” is in all likelihood a lizard or other non-dinosaurian reptile . For more information see the Nature report here.
_____________
Yes, we have a novel fossil, just described in Nature, that’s neither fowl nor reptile. And it’s TINY—roughly two grams. How small is it? Well, it’s about the size of the world’s smallest bird: the bee hummingbird of Cuba (Mellisuga helenae), which is this size:
The intermediacy of this fossil, which is part of the radiation that led to the evolution of modern birds from dinosaurs, is instantiated by the title and content of the paper below (it’s not free, but judicious inquiry will get you a copy).
The fossil, found in 99-million-year-old amber from Myanmar (Burma), is called a dinosaur above, but in the fourth paragraph of the paper it says (my emphasis), “Diagnosis: Very small bird with the following autapomorphies [a derived trait found only in one species or group]”. Is it a bird or is it a dinosaur?
Well, it’s both: it’s a transitional form: both the smallest dinosaur ever found as well as the smallest extinct bird. (As I said, it’s about the size of the smallest living bird: the bee hummingbird. Both weigh about 2 grams, or 1/15th of an ounce!) The transitional nature of the creature is shown by its reptilian features, including teeth, as well as birdlike features including a well-defined eye socket and a dome-shaped skull (see below). But it also has unique features, like a massive “scleral ring” (a circle of heavy bones around the eye); many teeth (over 100 in total) that extend the length of the jaw; the fact that the teeth are not, like those of dinosaurs, embedded in sockets but attached to the jaw by their sides; and the shape of the eyes, which suggests that they may have bulged out of its head like a lizard’s. These features are not known in either dinosaurs or early or modern birds.
Because the creature was found in amber, it was well preserved compared to early birds, which have fragile bones that are easily crushed. (The Chinese specimens that gave us much insight into bird evolution come from very fine sediments that preserved and mineralized the bones, but nothing this small has been found—only one-sixth the size of the next largest early bird.) The species has been named Oculudentavis khaungraa (“Eye-tooth-bird” with the name khaungraae coming from the donor, Khaun Ra).
Here are some photos and drawings from the paper; I’ve put below the CT scan of the skull as well as a larger picture of the amber. Note that the scale bar at the top, to the right of “b”, is only 5 mm, or about 1/5 of an inch.
The CT scan is below. Look at that bony ring (“sclerites”) around the eye! The fact that the eye opening is small suggested to the authors that this creature was diurnal (active during the day).
Further, the numerous teeth, which, as you can see from above, go all the way from the tip of the jaw to behind the eye, as well as the shape of the tongue, suggested to the authors that this was a predator. Unlike the smallest birds like hummingbirds, which sip nectar, this thing probably ate small arthropods and other invertebrates.
Here’s an enlargement of the amber in which it was found:
Because of the many unusual and unique features of Oculudentavis khaungraa, it’s hard to place it in a phylogeny of birds and dino-birds. The authors have tentatively placed it where the red arrow is in the phylogeny below, near the famous Archaeopteryx. But the authors also suggest that “the taxon falls outside Ornithuromorpha” (also called Euornithes), the group that includes all modern birds. The fact is that it’s such a weird creature means that they can’t really place it anywhere with any accuracy.
The authors suggest that the weird features of the creature are a byproduct of its miniaturization, which can, they say, cause the reappearance of ancestral traits. And while they and the media—which has covered this widely—say that O. khaungraa can shed light on early bird evolution, it’s hard to see what light that is.
Since there’s only one specimen, and only the head, it’s hard to tell what it means. It may be a one-off group, a weird branch in the early radiation of avian-like theropod dinosaurs that went extinct. It may show us that the ecology of early feathered dinos, which probably now includes diurnal predators on invertebrates, is wider than previously thought. The interest in this creature probably stems mostly from its intermediacy, its size, its excellent preservation, and its combination of features hitherto unknown in the radiation of feathered theropods. (We don’t know if O. khaungraa had feathers, as the paper gives no information, but it seems likely).
Here’s a very good 3.5-minute Nature video that summarizes the discovery in detail.
_________________
Xing, L., O’Connor, J.K., Schmitz, L. et al. Hummingbird-sized dinosaur from the Cretaceous period of Myanmar. Nature 579, 245–249 (2020).
Fascinating. If nothing else this example shows how much we have missed in the fossil record. Even though tiny, those teeth look fearsome.
This line from the paper brings Randy Newman to mind; “Miniaturization is strongly associated with extreme homoplasy, which obfuscates phylogeny.”
Sorry. Couldn’t resist.
This is extremely interesting.
Dr O’Conner says at the end of that Nature video that lots more interesting amber fossils are coming!
Yes, I hope they hurry up and publish!
Very interesting find. Of course on creationist “logic” there are now even more gaps in the fossil record because instead of one larger gap there are now two smaller gaps on each side of this creature!
You Dropped A Bomb On Me
Awesome- I saw that in the news and said to myself that I’ll wait to hear what PCC(E) has to say first.
Absolutely fascinating. I’d love to discover a piece of amber with something stunning in it like this.
200 of these wouldn’t weigh a pound.
It would take 250 birds!
A spectacular find.
“Unlike the smallest birds like hummingbirds, which sip nectar, this thing probably ate small arthropods and other invertebrates”
Modern hummingbirds get much of their protean form small insects and are not restricted to a nectar diet. Anna’s hummingbird for example doesn’t migrate in winter in some areas, but survives when flowers are not in bloom. I can see why ancient birds lost their teeth – they add weight which impedes flight.
Plus brushing them in flight is really hard to do.
Seriously though, I wonder how true that is. After all, many reptiles, large and small (like this one) with teeth were flying about for many millions of years. Maybe it’s just coincidence that birds today have no teeth because by chance only toothless birds survived?
Disclaimer – though the field fascinates me, there is not one paleontologist bone in my body.
That’s a good question. Teeth must have been adaptive for early flyers. Claimer – I’m sure you do have a few paeontological bones in you – perhaps in a dusty drawer in your mental attic. 😎
Hmmm. I doesn’t seem to me that they are adaptive just for early flyers; bats have teeth.
I know that people have done energy budget calculations and that teeth are expensive things to have. But if they are expensive for birds they were/are expensive for pterosaurs, other flying reptiles, early birds and bats. So why did/do they have them but modern birds don’t?
It could be that the cost of maintaining them could have been useful for mating rights, defence and dealing with its prefered prey. Perhaps in the end, helped it to go extinct… as in, a dead end line.
Good point(s).
Hmmm. This is not a very satisfying answer to me. Not having expertise in this I can’t put a finger on why but I have a hard time believing that teeth were problem for all flying tetrapods except bats. It seems to me more parsimonious to think that modern birds descended from a few toothless ancestors who managed to survive the cataclysm that wiped out the pterosaurs*, flying reptiles and most birds, toothed or not. Bats arose later.
*some of them were toothless, I believe, but they died too, though I don’t know if any were extant at the Cretaceous–Paleogene boundary.
One last comment from me on a topic I know so little about (why would that stop anyone from commenting?) Bats are extraordinarily successful, coming behind only rodents as the most abundant mammal species. I don’t think that has much to do with their teeth (probably due to the fact that most bats fly when birds can’t) but their teeth don’t seem to have harmed their survival.
I dunno. Looks like I need to do some reading.
I’m saying teeth weren’t a problem to this creature, its how it survived but there could may well be no decendents from this animal.
NS however on some other species, did work it out, that is, eliminate energy cost of producing teeth, with no cost being toothless as to fecundity. Resulting with birds as we see them today. It’s a guess no more than that.
Just last month here in wintry Washington I saw my first Anna’s. I keep hummingbird feeders year ’round to keep non-migrating hummers sustained. Seeing that bright pink head against the grey background was a sight to see. Haven’t seen him since, hope he’s still ok.
Looked out the window and there is an Anna perching in the top of my persimmon tree. One or two there just about every day for past five years [since the persimmon got to proper tree size]. With occasional 10-degree F frosts and a few snow events, they’ve persisted. Quite a tribute to feather insulation. Probably a tribute as well to the hardiness of our local gnats.
Lucky you! Both for your Anna’s and persimmon tree. I love persimmons.
Congratulations on the Anna’s. I have not seen one, but they are occasionally reported here. It seems a risky lifestyle, yet somehow they manage.
I would expect this to have feathers, and there are to me hints of them next to the specimen in various places.
I don’t know why the tongue suggests it’s a predator.
I googled Ocludentavis khaungraa and got one result haha. (This page.)
That’s because I left out a “u”: It’s Oculudentavis. I’ve changed it now; thanks for the heads-up.
“Neither fowl nor reptile”? For shame, PCC(E)! 🙂
-Ryan
This is truly a spectacular fossil, but there are good reasons to think that it is not a dinosaur at all (more probably some kind of lizard or lizard-like reptile): http://theropoddatabase.blogspot.com/2020/03/oculudentavis-is-not-theropod.html
At first I thought that had to be wrong, then I read it and think she really could be on to something. The beak-like jaws are very different from any lizard-like thing, but that’s less important than the positive reasons for why it could be a lizard-like thing. Interesting!
Astonishing!
An amber treasure…if g*d wanted us to accept Creation, it would have never allowed the creation of plant resin!
Thanks for this post, truly remarkable.
A small niggle – the fossil’s from Myanmar, not the Baltic deposits.
Did I say Baltic. OY! No, it’s from Myanmar (the former Burma). I’ll fix that, too. Thanks.
How do we know this isn’t a baby or fetus fossil? I haven’t seen anything to distinguish it as a full-grown, yet small, adult from a baby of a species.