Category: paleontology

New report: Bacteria can remain alive for over 100 million years!

July 30, 2020 • 10:00 am

Well cut off my legs and call me Shorty (is that ableist?). A new report in the journal Nature Communications shows that some bacteria can remain dormant for over 100 million years in marine sediments—an unbelievable amount of time for an organism to remain “alive”—if you call it “alive.” I do: after all, the bacteria collected and revived by the researchers retained their ability to metabolize, take up labeled organic substances, and reproduce.  Dormancy, to me, at least, is not the same thing as “death”.

Click the screenshot to read the paper (the pdf is here and the full reference is at the bottom).

The experiment was laborious yet the results are simple. If you want to know the gory details, the paper is there for your reading.

In short, the authors sampled clay sediments of different ages from the South Pacific Gyre, and did so in a way that, they aver, precluded contamination with modern bacteria. Supporting their claim that the bacteria they found in the inside of sea-floor cores were really bacteria in situ, they argue that the clays are almost impermeable to bacteria, with very low pore size, and there are thick impermeable layer above the sampled sediments. And there were strict precautions to prevent contamination.

To see if any bacteria in the sediments were capable of biological activity including reproduction, they tested for “anabolism” (the synthesis of molecules) by incubating the bacteria with oxygen (controls lacked oxygen) as well as radioactively labeled molecules that could be taken up and made into proteins and other molecules. The added molecules included 13C6-glucose, 13C2-acetate, 13C3-pyruvate, 13C-bicarbonate, 13C-15N-amino acids mix [mixture of 20 Amino Acids], and 15N-ammonium. Another control involved killing any bacteria with formaldehyde.  The researchers could then visualize the bacteria and see, through fluorescence microscopy and radioactive visualization, if the precursor molecules had been taken up by bacteria.

Finally, the researchers could isolate bacteria at various times (the samples for activity, growth, and bacterial presence were taken at 3 weeks, 6 weeks, and 18 months) to see if the bacterial titer was increasing, i.e., they were dividing. Finally the authors isolated RNA (16S rRNA) from individual bacteria, amplified it, sequenced slow-evolving RNA, and saw what groups of living bacteria the ancient bacteria belonged to. (This assumes that we can still recognize the groups from modern sequences, but these molecules evolve very slowly).

The upshot:

1.) The aerobic bacteria (bacteria that require oxygen) were still viable, initiating metabolism and reproduction even in sediments as old as 101.5 million years. Anaerobic bacteria, which don’t require oxygen, didn’t do nearly as well, and the authors suggest that even low oxygen concentrations in the sediments over geological time simply kills anaerobic bacteria.

Here’s a figure from the paper showing photos of the bacteria, with the same bacteria then examined for uptake of added molecules. The caption is complicated, but you can see that, especially with added amino acids (and oxygen), the cells glow furiously (d and h are electron-microscope images of the same bacteria shown fluorescing in the rows).

(from paper): Cells from incubations of U1365 9H-3 with 13C-bicarbonate and 15N ammonium (a–d) and 13C,15N-Amino acid mix (e–h). (a, e) SYBR Green I-stained cells under fluorescence microscopy. b, c, f, g Ratio images of 13C/12C (b, f) and 12C15N/12C14N ratios (c, g) of the same regions imaged in a, e, demonstrating locations of 13C and 15N incorporation. Color-scale ranges of the ratios are shown as numbers appearing at top and bottom of the color bar. The background membrane region, which is identified by fluorescence images, is excluded from the ratio calculation and shown as black background. d, h. Secondary electron (NanoSIMS) images of the same regions in a, e. Bars represent 5 µm. Similar images were processed for obtaining the dataset (Supplementary Data 1) of substrate incorporations for 6986 individual cells.

2.) The bacteria divided, as measured by the increase in numbers over time in the samples.

3.)  Anaerobic bacteria were much harder to find metabolizing than aerobic bacteria. The former were effectively defunct.

4.) The lineages of bacteria identified as persisting in the sediments, judged from sequencing them and comparing the 16S rRNA to modern samples, include Actinobacteria,  Bacteroidetes,  Firmicutes,  Alphaproteobacteria,  Betaproteobacteria,  Gammaproteobacteria, and Deltaproteobacteria, and cyanobacteria (“blue-green algae”). It would be interesting to compare the sequences of these early species with their modern relatives to see exactly how much and what kind of evolution has gone on.

5.) How did they survive? One thought was that they formed dormant spores, which can last a long time in bacteria. But this suggestion is ruled out because none of the bacteria identified were from spore-forming lineages. It seems the bacteria simply became dormant, surviving without any—or hardly any—detectable metabolism, and without reproduction.

This raises the question: were these things really alive for 101.5 million years? I can’t see why not, unless you think that something that becomes dormant is dead, and then, Lazarus-like, revives when the dormancy is broken. If you take the authors’ word that sufficient precautions were taken to prevent contamination with modern bacteria, then what we have here are the oldest living organisms on Earth.

h/t: Jeremy

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Morono, Y., Ito, M., Hoshino, T. et al. Aerobic microbial life persists in oxic marine sediment as old as 101.5 million years. Nat Commun 11, 3626 (2020). https://doi.org/10.1038/s41467-020-17330-1

A tiny 10-cm dinosaur that ate bugs

July 29, 2020 • 9:00 am

Note: The classification of “dinosaur” above isn’t totally accurate, for the creature discussed below is an archosaur, a member of the group that gave rise to dinosaurs, pterosaurs, and crocodilians. But we might as well call it a dinosaur, as few people know what an “archosaur” is.

The ancestors of the dinosaurs could not have been big, for they evolved from amphibians, and amphibians, for a number of reasons, are limited in size.  But this new paper in PNAS shows that some of the earliest ancestors of dinos were very small—not just small, but tiny. The new species described below, which falls into a group that later diverged into pterosaurs (flying reptiles) and the dinosaurs, was only 10 cm tall, the distance between my index fingers in the photo below:

Click on screenshot to read the paper; the pdf is here, and reference at bottom of post.

The partial skeleton of this tiny creature, whose dentition suggests it ate insects, was discovered in 1998 in Southwestern Madagascar. Although the age of the specimen is a bit uncertain, a good estimate is about 237 million years.

Here are some drawings of the parts of the skeleton they recovered, including leg bones, a forearm bone, and the jaws (interpreted as coming from single individual), and a figure showing where they fit into the body (figure F). The size, estimated from the bones, which clearly put the species in the ancestral group Ornithodira (also known as Avemetatarsalia), show that the creature was only about 10 cm tall. It must have been really cute: a pet-sized reptile. Note that the length of the scale bar on the left, showing the femurs, is one centimeter (about 4/10 of an inch), while on the right the scale bar for the jaws is only about 40 mm (1.6 inches):

(from paper): Anatomy of the femur and maxilla of Kongonaphon kely gen. et sp. nov. (UA 10618). (A) Right femur in anterolateral, (B) posteromedial, and (C) proximal views. (D) Right maxilla in right lateral and (E) palatal views. (F) Preserved elements in the holotype, UA 10618, presented in a silhouette of Kongonaphon. aof, antorbital fenestra; at, anterior trochanter; fht, tip of femoral head; fp mx, facial process of maxilla; ft, fourth trochanter; mx f, maxillary foramen; pf, palatine fossa; pmt, posterior medial tubercle; t, maxillary tooth. Illustrations credit: American Museum of Natural History/Frank Ippolito.

The authors named the fossil Kongonaphon kely, meaning “tiny bug slayer”. They explain the etymology:

. . . derived from kongona (Malagasy, “bug”) and φον (variant of ancient Greek φονεύς, “slayer”), referring to the probable diet of this animal; kely (Malagasy, “small”), referring to the diminutive size of this specimen.

The teeth, as you can see in the drawing above, were simple ones: conical and without serrations. That suggests that the creature lived on insects (I used “bug” in the title as a generic word for insects, though technically, bugs are in the order Hemiptera). The estimated size of 10 cm comes from the size of the preserved femur, which is only about 1.6 inches long. The specimen wasn’t a juvenile, as the authors saw signs of arrested growth in the fossil bones. The bones also indicate strongly that K. kely was bipedal, like T. rex and the theropods.

To place this individual in the phylogeny of dinosaurs and their ancestors, the authors did a computer analysis of 422 characters derived from these bones, and K. kely fell out in group B of the phylogeny below, which includes the dinosaurs and the pterosaurs (the relative size of this tiny species is shown to the right). I’ve put a box around K. kely.

B is the base of the Ornithodira, the group that gave rise to all dinosaurs and pterosaurs, and you see that K. kely is an early (“basal”) member of this group

(from paper): Body size of early avemetatarsalian (bird line) archosaurs mapped onto a consensus supertree, based on the current phylogenetic analysis (SI Appendix) and recent analyses (22). Silhouettes are scaled to estimated femoral lengths for the labeled nodes (SI Appendix, Table S1): A, base of Avemetatarsalia (represented by Teleocrater); B, base of Ornithodira (represented by Ixalerpeton); C, base of Dracohors (Silesauridae + Dinosauria) (represented by Silesaurus); and D, base of Saurischia (represented by Herrerasaurus). Silhouettes credit: Phylopic/Scott Hartman/Mathew Wedel, which is licensed under CC BY 3.0. Silhouette of Kongonaphon to the right of the taxon label is to scale.

Here’s a reconstruction of K. kely, eyeing a beetle, from Science Alert;  (artist’s impression by Alex Boersma):

Now the diminutive size of this creature doesn’t mean that the common ancestor of all dinos and peterosaurs was this small. But it does imply that the ancestor of those groups, which falls out in a “reconstruct-the-size” analysis, was smaller than we thought. K. kely itself could have been the result of a “miniaturization event” in which a somewhat larger ancestor produced some tiny descendants. The estimated size of ancestral Ornithodiran  is estimated fo be about 13.3 cm, or about 5.3 inches tall, and the ancestral species of the Dinosauromorphs, which includes dinos and birds but not pterosaurs, is even smaller, about 6.5 cm (2.5 inches)!

What are the implications of this beyond showing that the ancestral dino and ancestral dino/pterosaur were likely a lot smaller than we thought? Well, first of all, we have no idea why these early creatures were so small. My own guess is that since insects had already evolved, there was an “open niche” to specialize in eating them, and if you want to make a living as a terrestrial reptile eating insects, you can’t be the size of a T. rex.

The authors note that the small size of this species (and probably its close relatives) accounts for the absence of ornithodirans in Early and Middle Triassic faunas, for small creatures have tiny, fragile bones that aren’t easily preserved. In fact, our best knowledge of early Ornithodirans previously came from sediments in Argentina whose nature allowed for the preservation of small animals.

Finally, the authors speculate that these small species would have a problem with heat retention, since they were ectothermic (“cold blooded”). Small creatures have a higher surface area/volume ratio than larger ones, which means more heat lost by radiation. Thus, suggest the authors, the filaments covering the bodies of some dinos and pterosaurs—which might have been homologous to feathers that eventually covered the theropods—would have been useful as insulation. This sounds good, but of course there are plenty of extant small insect-eating reptiles, like geckos and anoles, that make a fine living without feathers. But it would still be useful to look at these early, small species to see if there is any evidence for filamentous body cover.

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Kammerer, C. F., S. J. Nesbitt, J. J. Flynn, L. Ranivoharimanana, and A. R. Wyss. 2020. A tiny ornithodiran archosaur from the Triassic of Madagascar and the role of miniaturization in dinosaur and pterosaur ancestry. Proceedings of the National Academy of Sciences 117:17932-17936.

 

Photographs of readers

June 7, 2020 • 2:30 pm

Today’s reader photos come from Bruce Thiel, whom I met at a talk I gave in Portland, Oregon. And there he gave me one of his fantastic preparations of fossil crabs, which I cherish and keep on my mantelpiece. You can see his preparations in his “reader’s photos” here. They are fantastic.  Bruce’s words are indented.

Here I am removing matrix from a Cretaceous Avitelmessus crab from North Carolina, using a pneumatic air chisel.  After 120 hours of work, the crab is still unfinished –including 40 hours work by two previous owners.  The two crabs on the right (#13) were given to the Smithsonian Natural History Museum and on display in the “Deep Time” Exhibit which reopened last summer after a five-year remodel.  A third crab also on display is not pictured.

What started out as a retirement hobby turned into an obsession to search for crab-bearing concretions in the 30-50 million year old ocean sediments in the Pacific NW.  Refining my technique led to the challenge of seeing if I could free the claws from the rock to create more sculptural poses.  However crabs are prepared exactly as they fossilize with no “rearrangement” of claws for aesthetics.

The top second-to-the-left crab in the second picture is noteworthy in that it hosts several 33-35 MYO tube worms. Two other tube-worm infested crabs were sent to Kent State where they were studied, published and donated to the Rice NW Museum of Rocks & Minerals here in Oregon.

While hunting for fossil crabs, I stumbled upon three concretions containing bones of a large penguin-like flightless bird, a Plotopterid, that turned out to be a new genus and species, published and named Olympidytes thieli, given to the Senckenberg Museum, in Frankfort, Germany.
See more crabs and info about the prep process at: https://whyevolutionistrue.com/2014/09/21/readers-wildlife-photos-100/

Readers’ wildlife photos

April 28, 2020 • 10:45 am

Do send in your wildlife photos, as the tank continues to empty. Today’s batch, from Robie Mason-Gamer, is unusual because it comprises fossils. Robie’s notes are indented:

This message stretches the definition of “wildlife” somewhat, back to a swampy Carboniferous community that existed over 300 million years ago. I hope the text is not overly long.

The Mazon Creek Formation in northeastern Illinois is a special place: a Carboniferous fossil site with unusual abundance and preservation, known as a lagerstätte. The fossils, estimated to be about 309 million years old, are extraordinarily well-preserved inside ironstone nodules called concretions.

I visited Mazon Creek in 2007, on a field trip associated with a botanical conference in Chicago. I recovered about 10 nodules of varying sizes and shapes, but none that I cracked open had anything interesting inside. It was disappointing, like opening a present and finding it empty. I still have a few unopened nodules; I guess I get more enjoyment from what might be in them than what is probably actually there.

However, I did end up with a few decent fossils. Field trip participants each received some de-accessioned Field Museum specimens, complete with ID labels. My other source was more unexpected. I used to hang out in a little local bar (since closed) with a group of friends. There was a semi-regular customer whom I came to recognize by sight, but did not otherwise know. One day, from across the bar, I saw him pull a Mazon Creek fossil out of his pocket and examine it. This startled me out of my usual reticence: “Hey! That looks like a Mazon Creek fossil!” He was interested in talking about it, and after a conversation, he went out to his car and came back with a box of 10 opened nodules, and gave them to me.

All of my Mazon Creek fossils are plants, but a diverse ancient fauna is represented there as well, including the Illinois State Fossil, the enigmatic Tully Monster (Tullimonstrum gregarium). The site represents an entire ecosystem, preserved in incredible detail. Here is a recent review of the site.

There are many seed ferns (Pteridospermatophyta) at Mazon Creek. Seed ferns comprise multiple extinct lineages of plants with fern-like leaves, but they reproduce through seeds (rather than spores, like true ferns). Many of them were large trees. This one is labeled as Alethopteris serli; here are the positive and negative halves of the nodule, and a closer look at the leaf surface. (Length 3 in/8 cm):
This fossil, labeled Macroneuropteris scheuchzeri, is a single leaflet from the large frond of an arborescent seed fern. (Length 4.25 in/10.75 cm)

Fossil horsetails are also common at Mazon Creek. All extant horsetails are herbaceous, but some extinct lineages included large trees. The top specimen is labeled Annularia stellata; the bottom one (unlabeled) is either that or some other Annularia. (One confusing thing about plant fossils is that—because different plant parts are often separated during fossilization—paleobotanists apply different taxonomic names to fossils of different plant parts, none of which need be the name of the actual organism. Annularia is an example of a “form genus”—it’s the name of this particular form of fossil leaf whorl, which likely came from a tree-horsetail in the genus Calamites.) (Width 1.5 in/3.25 cm)

Last, here is a true fern. The top left specimen (with closeup on the right) is labeled as Pecopteris unita. Again, this is the “form” name of the leaf fossil; the organism itself was likely a large tree fern of the extinct genus Psaronius. The lower left specimen (unlabeled) might or might not be the same thing; there are lots of Mazon Creek fern and seed-fern leaves that look alike to me. (Length 4.5 in/11 cm):

 

Oldest “bilaterian” found: wormlike creature discovered along with its tracks

March 26, 2020 • 9:45 am

One of the big mysteries of paleobiology is where complex life (i.e., animals) came from, and what the earliest animals looked like. The first traces of life that we have go back about 3.7 billion years ago, but those are cyanobacteria (the so-called “blue green algae”). The first “true cells”—unicellular eukaryotes, go back to about 1.8 billion years. But then there’s a huge gap of 1.2 billion years before we have the first traces of more complex multicellular life (putative sponges, jellyfish, and ctenophores) near the beginning of the Ediacaran period (571-541 million years ago). That fauna contained a number of bizarre and enigmatic forms.

Many of those forms went extinct without issue at the beginning of the Cambrian (about 545 million years ago). But since there was not a separate and later creation that led to modern animals (we know this from molecular data), some of the earlier fauna alive during the Edicarcan period must surely have been the ancestors of modern animals. Today’s paper involves a search for the earliest representatives of the Bilateria, a group that includes all but the simplest animals. I’ll let Wikipedia tell you what the Bilateria are:

The bilateria /ˌbaɪləˈtɪəriə/ or bilaterians are animals with bilateral symmetry as an embryo, i.e. having a left and a right side that are mirror images of each other. This also means they have a head and a tail (anterior-posterior axis) as well as a belly and a back (ventral-dorsal axis). Nearly all are bilaterally symmetrical as adults as well; the most notable exception is the echinoderms, which achieve secondary pentaradial symmetry as adults, but are bilaterally symmetrical during embryonic development.

Most animals are bilaterians, excluding sponges, ctenophores, placozoans and cnidarians. For the most part, bilateral embryos are triploblastic, having three germ layers: endoderm, mesoderm, and ectoderm. Except for a few phyla (i.e. flatworms and gnathostomulids), bilaterians have complete digestive tracts with a separate mouth and anus. Some bilaterians lack body cavities (acoelomates, i.e. Platyhelminthes, Gastrotricha and Gnathostomulida), while others display primary body cavities (deriving from the blastocoel, as pseudocoeloms) or secondary cavities (that appear de novo, for example the coelom).

So, in the fossil record, paleobiologists have been looking for animals that are bilaterally rather than radially symmetrical, with a front and back (ergo a head and anus with a gut between them), and with evidence of a coelom (body cavity). Kimberella, found in both Russia and Australia (see fossil below), is a putative bilaterian, but people still argue about whether it may be a coelenterate (jellyfish relative), animals that aren’t bilaterians. (There are also “scratch marks” associated with it, suggesting that it had a radula and may have been a kind of mollusc, which are bilaterians:

Kimberalla quadrata. Arkhangelsk Regional Museum Author: Aleksey Nagovitsyn (User:Alnagov)

Now, however, in a new paper in the Proceedings of the National Academy of Sciences (USA), four researchers have found what seems to be an unambigous fossil of a bilaterian, as well as the burrow that it was probably making as it tunneled underneath the shallow-sea sand, feasting on microbial mats of bacteria. You can access the paper free by clicking on the screenshot below, or get the pdf here (reference at bottom).

Several of these creatures, named Ikaria wariootia, are found near “trace fossils”: tracks or burrows that were given the name Helminthoidichnites (traces of animals, like their paths, were given scientific names in the absence of the animal who made them). They are dated—using igneous material like ash, near the sedimentary layer)—to about 560-551 million years ago (dating done by correlating strata with dated similar strata in Russia).

The fossils, both animal and its tracks, are in fine sandstone from the Nilpena beds in South Australia, where fantastic Ediacaran forms have been found. And what they show are small bilaterian-looking animals ranging in size from 2-7 mm (0.1-0.3 inches): about the size of a grain of rice.  Moreover, at least one of them was associated with a trace burrow of about the size that would be made by such a creature. That one’s in the photo below. (The animal shown below was probably displaced from the burrow by movement of the substrate.) The scale bar to the right is 1 mm. Note that the burrow shows lateral “zig zags”, as if some animal was humping itself along right beneath the sand.

(from PNAS): Photograph. . . (of I. wariootia. (A) Specimen (white arrow) associated with Helminthoidchnites [JAC: the burrow]
And there are many specimens of the creature visualized by laser scanning. They show a creature with a broad end (presumably the front) and a narrower end (presumably the rear), with all of them showing relatively similar ratios of length/width, suggesting this is not some geological artifact but a real animal. Note the broad front end (burrowers are larger in front than the rear when there’s asymmetry), as well as the bilateral symmetry:

(from PNAS): Type specimen of I. wariootia from Nilpena, including (A) photograph; and (B–D) 3D laser scans. Notice distinct bilateral symmetry (wider end identified by white star in C and deeper end by black star in D). P57685. (Scale bars, 1 mm.)

I’m not a paleontologist, but these data and photos are pretty convincing that here we do indeed have a very early bilaterian, perhaps one close to the “common ancestor” of all animals save the few taxa listed above. (We cannot know, of course, whether this is the “common ancestor” of bilateral animals, even though the hyperventilating media suggests otherwise. But it’s certainly something that is close to what that common ancestor might have looked like.)

The evidence of bilateral symmetry is manifest in the fossils. The nature of the furrows in the sediment probably made by this creatures suggest to the authors that it has a coelom (body cavity) and musculature, while the “V-shaped transverse ridges” in the burrows suggest that it had “peristaltic locomotion” like earthworms:

Peristaltic locomotion is a common locomotor pattern in elongated, soft-bodied invertebrates, particularly in segmented worms, such as earthworms. It involves the alternation of circular- and longitudinal-muscle-contraction waves. Forward movement is produced by contraction of the circular muscles, which extends or elongates the body; contraction of the longitudinal muscles shortens and anchors the body.

That is, the movement isn’t smooth but is jerky, which would produce the ridges. To the authors, this implies a “potentially modular body construction” with the necessary muscles. The authors also suggest that “sediment displacement and scavenging reveal that Ikaria likely had a coelom, mouth, anus, and through-gut” (all traits of Bilateria).

I’ve checked with one early-life paleontologist, who says that yes, this is pretty good evidence for an early bilaterian, and the only good evidence in which a putative early bilaterian is associated with its tracks in the sediments. The authors of the paper provide a reconstruction of Ikaria and its track in the paper, which, with the color added, makes it look a bit penis-like:

(From paper): Reconstruction of Ikaria in life position forming a Helminthoidichnites-type trail.

This is a pretty important discovery, I think, as it gives us a glimpse of what may be the ancestor of all bilaterally symmetrical animals, including, of course, us.

Sadly, as I noted above, some news organizations say it is the common ancestor, and we have no way of knowing that. Here’s one of the miscreant organizations (Phys.org), which gets most of the stuff right but has a very misleading headline (click on screenshot). And you can blame the news site of the University of California at Riverside, which provided the article that Phys.org copied word for word.

 

Always be wary when you see in the news that a “common ancestor” or “missing link” has been identified. In this case, the very university that was home to the first author Scott Evans badly screwed up the significance of the finding. We have no fricking idea whether I. wariootia is the “ancestor of all animals”, a claim that is flat wrong in two senses. First, sponges, coelenterates, and other radially symmetrical fauna are “animals”, but not descendants of this wormy creature. Second, we have no idea whether I. wariootia is even the ancestor of “all bilaterians.”

Now the authors themselves don’t make this claim; the blame rests on the media and on the UCR publicists, but one would think that the UC Riverside publicity department would run the headline past the researchers.

Well, never mind; it’s still an important finding and a really lovely one.

h/t: Hos, Latha Menon

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Evans, S. D. J. V. Hughes, J. G. Gehling, and M. L. Droser. 2020. Discovery of the oldest bilaterian from the Ediacaran of South Australia. Proceedings of the National Academy of Sciences Mar early edition,; DOI: 10.1073/pnas.2001045117

Another biologist disputes the nature of the tiny “bird/dino” fossil

March 15, 2020 • 9:00 am

On March 12, I wrote about the new Nature paper describing the fossil of Oculudentavis khaungraa, identified as a tiny (2-gram) dinosaur/bird found in Burmese amber. But the very next day I had to hedge the results after reading Darren Naish’s Tetrapod Zoology post, not only on humanitarian grounds (the amber used in the study may be “blood amber”, used to fund the military), but, most important for the science, because other paleontologists started doubting that this fossil was indeed that of a theropod. As Darren notes,

“. . .  a number of experts whose opinions I respect have expressed doubts about the claimed theropod status of the fossil discussed below and have argued that it is more likely a non-dinosaurian reptile, perhaps a drepanosaur or lepidosaur (and maybe even a lizard).”

The article below, translated from the Italian by Google (click on screenshot), was called by my attention by reader Gerdian de Jong who wrote this to me:, “The respected paleontologist Andrea Cau writes in his blog Theropoda.blogspot why Oculudentavis is not a bird or theropod and that wider analysis points to stem-Gekkota.”

First, though, here are two reconstructions of O. khaungraa by Darren, who kindly gave me permission to reproduce them here (© Darren Naish/Tetrapod Zoology). The captions are his.

Speculative life reconstruction of Oculudentavis, its feathering and other details inspired by Jeholornis and other archaic members of Avialae. I’ve depicted it on the forest floor but am not necessarily saying that this is where it spent all of its time. Image: Darren Naish.

A to-scale reconstruction by Darren. Note that the ruler is in centimeters, not inches (2.54 cm/inch, so the 10-cm ruler is only about four inches long.

A very rough, semi-schematic skeletal reconstruction of Oculudentavis which I produced in order to gain a rough idea of possible size. As you can see, it would have been tiny. The overall form of the skeleton is based on that of jeholornithiform birds; read on. Image: Darren Naish.

I’ll call attention to other articles/critiques about this specimen as they come to my attention. At any rate, right now it’s unwise to regard this as a theropod dinosaur that was also avian.

Click on the screenshot to read in Italian or get a translation. I’ll provide a summary of the translation (indented) below.

After reading the study, and observing in detail the navigable 3D model of the skull, produced by the authors, I believe that the interpretation proposed by Xing et al. (2020) is very problematic. Oculudentavis in fact has numerous anomalous characteristics for a bird and even for a dinosaur. And this makes me doubt that it is classifiable within Dinosauria (and Avialae).

Absence of anti-orbital fenestra.

Quadrate [bones] with large lateral concavity.

The maxillary and posterior teeth of the maxillary extend extensively below the orbit.

Dentition with pleurodon or acrodont implant.

Very large post-temporal fenestra.

Spoon-shaped sclerotic plaques.

Coronoid process that describes a posterodorsal concavity of the jaw.

Very small size.

Oculudentavis is much smaller than any other Mesozoic avian discovered so far. Its dimensions are comparable to those of the skulls of many small squamata found in Burmese amber.

In conclusion, there are too many “lizard” characters in Oculudentavis not to raise the suspicion that this fossil is not a bird at all, let alone a dinosaur, but another type of diapsid, perhaps a scaled lepidosaur, if not possibly a specimen very immature than some other Mesozoic group (for example, a coristodero). 

If I had to bet money between the hypothesis that it is a very small bird with unusual “lizard” convergences and the hypothesis that it is a very immature skull of a non-dinosaurian reptile, I will point the second.

To read more about why the traits in bold are more indicative of a lepidosaur than a dinosaur, read the original article.

But what are lepidosaurs? They are a monophyletic group of reptiles that contains the extant snakes, lizards, tuataras and worm lizards (“legless” lizards). “Monophyletic” means that the group contains all descendants, living or extinct, from a common ancestor. Lepidosaurs do not include dinosaurs. Here’s a family tree from Quora, which shows that dinos aren’t within the Lepidoauria, as the latter group is over on the right.

 

Now the fact that this fossil may not have been a theropod dinosaur but a lepidosaur, like a lizard, doesn’t make the original results uninteresting. In fact, to me it makes them more interesting. First, it shows that there could have been convergent (independent) evolution to birdlike forms in both dinosaurs and lepidosaurs (perhaps from a lizard-like ancestor). That would be stunning.

Further, it shows that regardless of whether the species in amber was a theropod or a lepidosaur, there may have been a whole radiation of miniature, bird-like creatures from an entirely different group of reptiles. Whether that was true depends on finding more specimens. Since these are small and fragile, it’s unlikely that they’d be found in anything other than amber. We shall see.

In the meantime, I hope the mainstream press, which touted this specimen as a form of dinosaur, at least gives a clarification.  While the messy details of anatomy are unlikely to interest the public, at least they’ll know that science is an ongoing process, and what is regarded as “true” is provisional, only becoming less provisional when more data are gathered. Right now we have but a single specimen of this type.

 

An update on the tiny dino-bird I described yesterday

March 13, 2020 • 10:15 am

Yesterday I wrote about the discovery, published in Nature, of a very small theropod dinosaur that appeared to be part of the radiation of early birdlike dinos. It was tiny and had features so unusual that it couldn’t really be placed in a phylogeny. The creature was named Oculudentavis khaungraae and was remarkably well preserved (well, just the head) in Burmese amber dated at 99 million years ago.

I’d like to issue an addendum after reading Daren Naish‘s post on his well -known website Tetrapod Zoology (h/t Dom). As Naish is a vertebrate paleontologist, he knows a ton more than I about this stuff, and in fact is able to evaluate its phylogenetic position. You can read his post by clicking on the screenshot below:

There are two issues raised by Daren. The first is whether this really is a feathered, avian-like theropod. The second is the ethicality of using specimens from Burmese amber. We’ll take the science first, with quotes from Naish’s piece indented.

After consulting with various experts in the field, Naish says this:

. . . . a number of experts whose opinions I respect have expressed doubts about the claimed theropod status of the fossil discussed below and have argued that it is more likely a non-dinosaurian reptile, perhaps a drepanosaur or lepidosaur (and maybe even a lizard).

That might explain why some of the fossil’s features, like the bulging of the eyes from the head, are more lizard-like than theropod like.  Here’s one reconstruction of the creature by Mette Aumala, reproduced by Nash (I’ve also obtained permission to use it):

The Tetrapod Zoology piece has several drawings and reconstructions of the creature by Naish, and you can see them there.

Naish adds this:

At the time of writing, this proposed non-dinosaurian status looks likely and a team of Chinese authors, led by Wang Wei, have just released an article arguing for non-dinosaurian status. I don’t know what’s going to happen next, but let’s see.

If it’s not a theropod, and not a feathered relative of early birds, this would markedly change its evolutionary significance. It wouldn’t make the fossil insignificant, but would divert us onto a track about the possibility of a bunch of miniature reptiles (and maybe amphibians) that we don’t know about because they’re too small and fragile to be preserved.

If it is a theropod, Naish is excited by the possibility that many early birds may have been as tiny as this creature (Naish estimates it as about 9 cm long, or about 3.5 inches).  Finally, if it was a theropod/bird, Naish speculates, following the authors, that it could have foraged for invertebrates on the forest floor, or even on “tiny vertebrates, like a dinosaurian shrew.”

At any rate, after reading Naish’s article we need to step back and not decide, prematurely, that this was an early avian creature or even a descendant of theropod dinosaurs. The mainstream press, unwilling to investigate as deeply as Naish, missed the possibility that this may be not a theropod but possibly even a non-dinosaurian reptile.

Second, there’s the issue of the amber. Naish gives three links to articles about why studying specimens from Burmese amber might be illegal (one of the links goes to a paywalled New Scientist article, but the other two are below).  The issues are these:

1.) Much of the recent informative, specimen-containing amber has been smuggled out of Myanmar illegally into China, depriving Myanmar of its paleontological heritage.

2.) The Burmese military and paramilitary could derive funds from these sales, so the money could be use to fund their wars against ethnic minorities like the Rohingya or Kachin.

3.) The workers aren’t treated particularly well (for example, if there’s an accident, they have to pay for their own healthcare).

4.) The fossils may remain in private hands, like those of Chinese collectors, and thus aren’t available for other scientists to study. Some journals won’t public analyses of specimens that aren’t available to other scientists (see video below).

5.) Finally, not an ethical issue but a scientific one. Many of these specimens simply can’t be accurately dated because they’re dug out of the ground in areas off limits to those who could provide dates.  The specimen used in the Nature paper was dated at 99 million years old, but that’s based on locality information, not on dating the amber itself or the surrounding strata. And the locality information may be dubious as well. Accurate dating is of course essential to place the fossil in its evolutionary context.

Here are two links about the ethicality of describing specimens from Burmese amber; they are given by Daren, and I give two short extracts and the links:

From the New York Times:

But much of the fossil-rich amber is mined in Myanmar, a country recently ordered by the United Nations International Court of Justice to protect its Rohingya Muslim minority against genocidal acts. The mining and sale of the amber may also be a source of profit for the country’s military. A report published last year in Science Magazine detailed how the amber is mined in a state where Myanmar’s military has long fought another ethnic minority, the Kachin, and how amber gets smuggled into China, where it can fetch high prices, potentially fueling that conflict.

These concerns are leading more scientists, especially in Western countries, to shun the use of this amber in paleontological research.

“Ever since the Rohingya crisis, I’ve boycotted the purchase of Burmese amber, and have urged amber colleagues to do the same,” said David Grimaldi, a paleontologist and the curator of amber specimens at the American Museum of Natural History in New York.

From Science:(article noted above; long and worth reading):

But as much as Burmese amber is a scientist’s dream, it’s also an ethical minefield. The fossils come from conflict-ridden Kachin state in Myanmar, where scientists can’t inspect the geology for clues to the fossils’ age and environment. In Kachin, rival political factions compete for the profit yielded by amber and other natural resources. “These commodities are fueling the conflict,” says Paul Donowitz, the Washington, D.C.–based campaign leader for Myanmar at Global Witness, a nongovernmental organization. “They are providing revenue for arms and conflict actors, and the government is launching attacks and killing people and committing human rights abuses to cut off those resources.”

Here’s a really nice Science video from last May on the general issue of specimens in amber, what knowledge we’ve derived from them, and the ethical problems of studying Burmese amber.