The earliest known animal?

September 21, 2018 • 10:45 am

The Ediacaran fauna, a group of extinct species that lived between 571 and 541 million years ago, has been an evolutionary anomaly. Its fossil record contains multicellular organisms, but they are just plain weird, bearing little resemblance to present-day metazoan (multicellular) animals.

The two species of “dickinsoniids” shown below, for example, lack a mouth or gut (possibly having external digestion instead), are bilaterally asymmetrical, and bear a pattern of body “quilting” that isn’t seen in present-day animals or definite early metazoans like worms:

Here’s Dickinsonia, studied in the paper we’re discussing today. It’s about 7.5 cm long, or three inches, so it’s fairly large:

Here’s a dickinsoniid in the genus Andiva, also studied in the present paper:

What are these things? Controversy has centered on whether they were a whole kingdom of life different from any that we know today (a group that went wholly extinct), or, in contrast, perhaps the ancestors of modern day animals—or at least the relatives of modern day animals. Scientists have guessed that they might be either lichens or giant protozoans. (Yes, protozoans can get this large; some are nearly ten inches long!) This is important to resolve because the “Cambrian explosion” that gave rise to many modern groups of animals began about 541 million years ago, and we want to know if there were animal precursors before that, and what they were. We also want to know whether the Ediacaran fauna really does represent an entire group of creatures that disappeared without issue.

A new paper in Science by Ilya Bobrovskiy et al. (reference at bottom with free Unpaywall link, free pdf here) establishes fairly securely that Dickinsonia and related anomalous species do indeed seem to be metazoan animals rather than members of a separate large group that went extinct entirely. The telling data involves biochemical analysis of the thin films of organic matter that cover the fossils and was presumably produced by the fossils. These fossils were 558 million years old, which, if they were animals, would make them the oldest known metazoans.

To make a long story short, Bobrovskiy and colleagues collected specimens of dickinsoniids from sandstones of the White Sea region of Russia and removed the small (three micron thick) organic mat covering the fossils. Great care was taken to avoid contamination, and they also analyzed the sandstone around, above, and below the fossil to see if the peculiar organic profile they found was associated with the fossil itself. It was, and it also suggested that the fossils were animals, not lichens or giant protozoans.

The telling chemicals were 27 carbon steroids—cholesteroids—which were present as 93% of chemicals in the mat atop the fossils, but only 11-12% of the surrounding sandstone (probably coming from algae or other plants). The fossils, moreover, were almost entirely missing a class of chemicals, ergosteroids, that characterize lichens. And the chemical signature of these fossils didn’t much resemble that of the modern giant protists, either.

There was, however, one twist to the findings: the “isomers” (chemically identical molecules of different handedness or arrangement) of the cholesteroids in these fossils were mostly of a single handedness (the “5β” form), while that of more recent and genuine animal fossils have a more even mixture of right- and left-handedness. This is puzzling, and the authors have no real explanation. This may suggest that even if these fossils were related to modern animals, they were distantly related, having a unique metabolism. They may, then, have branched off from modern animals, with the dickinsoniids and other Ediacaran fauna having gone extinct without descendants. Further, analysis of Andiva doesn’t show the same elevation of cholesteroids, though it does show a preponderance of 5β forms.

So this isn’t as compelling a demonstration as I had wished, but it still shows that these things were probably metazoans and not creatures related to modern lichens or protozoans. The authors conclude this:

Molecular fossils firmly place dickinsoniids within the animal kingdom, establishing Dickinsonia as the oldest confirmed macroscopic animals in the fossil record (558 million years ago) next to marginally younger Kimberella from Zimnie Gory (555 million years ago). However alien they looked, the presence of large dickinsoniid animals, reaching 1.4 m in size, reveals that the appearance of the Ediacara biota in the fossil record is not an independent experiment in large body size but indeed a prelude to the Cambrian explosion of animal life.

“Prelude” is a bit ambiguous, but I’ll grant that these are animals. I asked my friend Latha Menon, who has a Ph.D. from Oxford in early life studies, whether this paper was important, and I give her answer (with permission):

I do think it is an important paper. I’ve recently seen a lovely Dickinsonia specimen in a collection. You can really see how it’s like a very thin flatworm like form (or like a giant Trichoplax?) draped over the uneven ground below. Much has been written about its morphology but to find a specimen with associated organic matter and demonstrate that it is an animal from the biomarkers is very solid evidence. We have indications of simple animals earlier, from the traces found by Alex Liu and myself, and the remarkable squished Haootia specimen Martin Brasier discovered, which seems to show muscle bands. This specimen is younger and part of a more complex assemblage, but it is good to have solid evidence of animals well before the Cambrian boundary and some 40 Ma before the Cambrian explosion. Animals did not burst on the scene then; there was, as most of us have suspected, a long fuse.

Of course this does not mean that all the large forms of the Ediacaran were animals; there were probably several kinds of forms. But it does show that one ‘quilted’ form was animal and that suggests a number of other enigmatic forms in the biota were too.

Just for grins, here’s a photo, courtesy of Australian National University, showing Bobrovskiy collecting fossils in Russia. It ain’t easy!

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Bobrovskiy, I., J. M. Hope, A. Ivantsov, B. J. Nettersheim, C. Hallmann, and J. J. Brocks. 2018. Ancient steroids establish the Ediacaran fossil Dickinsonia as one of the earliest animals. Science 361:1246-1249.

A Science News and Views piece on the paper: Summons, R. E. and D. H. Erwin. 2018. Chemical clues to the earliest animal fossils. Science 361:1198-1199.

How pterosaurs flew

June 23, 2018 • 11:30 am

Matthew Cobb called this video to my attention, and I thought it was worth putting up. Anhanguera is a genus of flying reptile that contains three described species. They were about 1.2 meters tall (four feet) with a 4.5-meter (15-foot) wingspan, and were heavy—weighing about 23 kg (50 pounds). They lived roughly 120 million years ago. Although Wikipedia describes them as fish-eaters, the New Dinosaurs site says this:

This is one flying reptile that you may not recognize from Anhanguera pictures. That’s because this pterosaur was discovered relatively recently – as compared to other flying reptiles – and doesn’t get the media attention that pterodactyls do. Which is quite a shame because this was one remarkable creature.

. . . its wingspan was about 3 times larger than a Crowned Eagle and its weight was about 12 times heavier than a Red-tailed Hawk. It had crests not only on top of its beak but also on the bottom.

One of the most interesting facts about Anhanguera is that it had relatively weak legs. Which means that it probably spent the majority of its time flying. If it did spend any time whatsoever on the ground, then it most likely walked with a very unusual gait and probably was a little wobbly.

Most paleontologists believe that this pterosaur used its beak to scoop up fish, but it is also possible that it hunted for carrion from dead animals that it discovered on land as well. It may have also eaten a variety of different insects as well. Which means that it may have had one of the most diverse diets of any flying reptiles of its time.

We have much of the skeleton, and reconstructions vary in external appearance, because of course we don’t have feathers. Here are two:

Here are some bones used in the reconstruction of a specimen’s skeleton (species not clear), and below that is the holotype (original specimen) skull from A. blittersdorffi:

Skull: (lower jaw missing); note the crest near the tip of the beak:

The cool part is the video below, which was made by London’s Natural History Museum. It doesn’t name the narrator, but it sure sounds like David Attenborough to me. The single-leap takeoff is amazing:

This animal is Anhanguera, one of the flying reptiles that lived alongside the dinosaurs. Pterosaurs lived alongside dinosaurs, but they formed a group of their own. Pterosaurs were evolutionary cousins of dinosaurs, and shared many features of their skeletons with them. But unlike their land-dwelling cousins, they took to the air. For the first time ever, we can watch how it might have flown. This animation was made for Hold the World, a virtual reality experience set behind-the-scenes at the Museum.

Notice that what supports the wing membrane is a single digit: the elongated fourth digit, shown below. The other digits were present, as they are in the reconstruction above, but are tiny. They may have helped the creature clamber about on the ground, as shown above, or they may have been relatively useless vestiges of ancestral fingers.

Possible life found in sediments between 3.8 and 4.3 billion years old

March 3, 2017 • 11:15 am

The Earth is about 4.54 billion years old, and the oldest undisputed life on our planet appears as bacterial “microfossils” 3.5 billion years ago. But because bacteria are already quite complicated organisms, it’s a good bet that life (however you define it), began well before that. But how long? The seas weren’t around much before about 4 billion years (the Earth was too hot), and there was no oxygen. Life, if it existed about then, was probably adapted to extreme temperatures and was anaerobic (not requiring oxygen).

A new paper in Nature by Matthew Dodd et al. (free access, reference below) has reported what may be traces of life (iron-containing filaments and tiny tubes) that resemble the kind of life found in modern hydrothermal vents, as well as in undisputed microfossils. The age of the sediments, which are from Hudson Bay in Quebec, Canada, spans a range between 3.77 and 4.28 billion years. They can’t narrow it down much more than this large range, and of course the press is concentrating on the 4.28-billion-year date, because that’s about the earliest life could have formed given the state of the Earth then.

I won’t go into detail about the paper: it’s a hard slog even for an evolutionary biologist, for it’s largely geology and paleobiology. But one expert I asked said that the results are very interesting but not conclusive, and that the age range of course is quite large. Here are a few photographs of what may be the remnants of ancient bacteria. First are the filaments (click to enlarge pictures):

nature21377-f1 — (From paper): a, Filaments from the NSB attached to a terminal knob (arrow) coated with nanoscopic haematite. b, Filaments from the Løkken jaspers coated with nanoscopic haematite and attached to terminal knobs (red arrows) and branching (orange arrows). Inset, multiple filaments attached to a terminal knob. c, Filaments from the NSB in quartz band with haematite rosettes (green arrow). Inset, branching filament (orange arrow). Green box defines d. d, Filament from the NSB enveloped in haematite (inset, same image in cross polars).

And the tubes:

nature21377-f2 — (From the paper): a–f, Tubes from the NSB. a, Tubes associated with iron oxide band. b, Depth reconstruction of tubes with haematite filament (arrow). Inset, image of tubes at the surface. c, Tube showing a twisted filament (red arrow) and walls (black arrow). d, Strongly deformed tubes. e, Depth reconstruction of tubes. f, Two tubes attached to terminal knob (arrows); lower image taken in false colour. g, h, Tubes from the Løkken jaspers. g, Tube showing filament (red arrow) and walls (black arrow). h, Aligned tubes (green arrows).

These of course are not microfossils themselves, which are the fossilized remains of ancient bacteria, but simply traces of what may be ancient bacteria.

Carl Zimmer’s article about the find in Tuesday’s New York Times also shows that some experts are dubious. Several seem to think the find represents real organisms, while others think they’re artifacts. Here’s a bit of Zimmer’s piece:

But many experts in the field were skeptical of the new study — or downright unconvinced.

Martin J. Van Kranendonk, a geologist at the University of New South Wales, called the patterns in the rocks “dubiofossils” — fossil-like structures, perhaps, but without clear proof that they started out as something alive.

. . . And if these are fossils 4.2 billion years old, then scientists will have evidence that life began quickly on Earth, not long after the oceans formed.

Yet Frances Westall, the director of research at the CNRS-Centre de Biophysique Moléculaire in Orléans, France, isn’t convinced these are fossils at all. “I am frankly dubious,” she said.

For one thing, she has argued, the filaments in the Nuvvuagittuq rocks are too big. She and her colleagues have found filaments formed by bacteria in rock dating back 3.3 billion years, and these are far smaller.

On the early Earth, bacteria were forced to stay small, Dr. Westall said, because the atmosphere did not yet have enough oxygen to fuel their growth.

From someone more enthusiastic:

“I think the authors have done a good job,” said David Wacey, who researches the origins and evolution of life at the University of Western Australia. With the new evidence, he said, “One comes up with a pretty convincing biological scenario” for the origins of the mysterious rock features.

Dr. Wacey was not surprised that the new work had drawn criticism. “It may be many years before a consensus is reached,” he said. “But this is how science progresses.”

I think the last sentence is the operative one. This is by no means evidence for early life, or even for its age, but it was certainly worth publishing and will doubtlessly lead to more work. If life really did exist 4.3 billion years ago, then it means that it didn’t take long after Earth’s conditions were “right” for carbon-based and water-requiring life to begin proliferating.

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Dodd, M. S., D. Papineau, T. Grenne, J. F. Slack, M. Rittner, F. Pirajno, J. O’Neil, and C. T. S. Little. 2017. Evidence for early life in Earth’s oldest hydrothermal vent precipitates. Nature 543:60-64.

The ancestor of deuterostomes? A new report.

February 1, 2017 • 10:30 am

A new paper in Nature by Jian Han et al. (reference and free link below; one of the coauthors is Simon Conway Morris, of Burgess Shale fame) describes the earliest known deuterostome: that superphylum of animals in which the blastopore (the first opening into the central part of the embryo) becomes the anus, and the second the mouth. (“Deuterostome” means “mouth second”). This is in contrast to the group of protostomes, in nearly all of which (there are exceptions) the first opening becomes the mouth, and the anus develops later at the other end.

Deuterostomes include all chordates (including vertebrates like us), echinoderms, and “hemichordates” (acorn worms and graptolites). Protostomes include everything else, including segmented and unsegmented worms, molluscs, insects, rotifers, and so on. Here’s a diagram showing the developmental difference, and a second diagram showing the big divisions of life.

The first deuterostomes, previously dated at 510-520 million years ago, have now been supplanted by Han et al.’s finding of a tiny creature (about 1.2 mm across) in central China, with the sediments dated to 540 million years ago. Although it has a huge mouth and no anus, it still shows features suggesting it was an early deuterostome, one that lived among the sand grains of the sea floor. The authors named it Saccorhytus coronarius, part of a new group called the Saccorhytida.

But first, some journalistic errors. If this creature was an early deuterostome, it would be one of the first creatures from the lineage that led to humans (and other chordates as well as echinoderms) after that lineage split from the lineage leading to protostomes. But that does not make it “humans’ oldest known ancestor,” as is blatantly (and erroneously) indicated by the title below.

That title is bogus! For all living and extinct species, including humans, had an ancestor that was much older than 540 million years—the “last universal common ancestor” (LUCA) of all creatures, which probably lived a bit over 4 billion years ago. The title above (click screenshot to go to link) was in fact from a press release by St John’s College in Cambridge, where Conway Morris works. How could they get it so wrong?

At any rate, that error seems to have been picked up by several other journalists. Here are two examples:

and this:

I like this one from LiveScience; it’s not only a bit more accurate, but funny. Actually, it’s not completely true, for this species didn’t have to be a human ancestor itself, for it could have gone extinct without descendants, like some of the early robust hominins. All its deuterostome ancestry shows is that it evolved after the split between the protostomes and the deuterostomes.

But on the paper, which I’ll summarize briefly. Han et al. report finding 45 of these creatures, with the reconstruction in color a couple of photos down. Here’s a scan of the anterior (front) part of the fossil itself, showing its big gob:

The most prominent feature of these fossils is the large mouth opening, clearly seen above, which is surrounded by several rows of papillae that may represent sensory organs. Each side of the body also bears four cones (8 total; you can see four above the mouth in the photo above). Han et al. suppose that the cones could have been used to expel water and waste, though they’re not sure.

These creatures were tiny, as I said, and were examined by both electron microscopy and CT scanning. Here are some photos; note the scale bars (a μm, or one micron, is one millionth of a meter, or one one-thousandth of a millimeter):

nature21072-f1 — (from paper): a–c, Holotype XX45-20. a, Right side. The mouth (M) arched dorsally along the anterior–posterior axis. b, Chevron pattern (Ch) on the inner surface of the integument. c, A spine (Sp) close to the mouth. d–f, XX45-56. d, Left side. e, Detail of the dorsally arched and folded mouth with radial folds (Rf) and oral protrusions (Op) in d. f, Circular pores (Cp) on the dorsal, right side. g–i, XX48-64 with limited compression. g, Ventral view, showing body cones (Bc) bilaterally arranged around the anterior, including the mouth. Two circular pores are adjacent to the first body cones (Bc1) and a small circular pore is on the mid-ventral line of the body. h, Oral protrusions lacking distal ends and appearing as a circle of pores. i, Left view reconstructed by microcomputerized tomography data. Lbc1–Lbc4, left body cones; Nr, nodular rugae; Rbc1–Rbc4, right body cones; Rf, radial folds; Sc, sub-layer of cuticle; arrowed AP, anterior–posterior axis.

But if these are deuterostomes, with the mouth forming after the anus, where’s the anus on these things? They don’t have one! The authors explain its absence this way:

Early deuterostomes have a through gut, so the apparent absence of an anus in Saccorhytus could be secondary, as in brachiopods and ophiuroids. [That is, its ancestors could have had an anus but lost it.] It remains possible, however, that this feature was inherited from more primitive bilaterians, possibly linked to the acoels and xenoturbellids.

But if there’s no anus, how can they call this an early deuterostome? It turns out that the small creature has other features that link it with the deuterostomes, as shown in the phylogeny below derived from several characters (the bootstrap support isn’t all that high). In particular, they show that Saccorhytus bears resemblances to “vestulocystids,” or early echinoderms, which are clearly deuterostomes. These features, also studied by Conway Morris and his colleagues, include truncated cones on the body, a convoluted anterior part of the body, and “well developed radial ribs.”

Here’s the phylogeny showing the new species (in red) falling out with the deuterostomes:

nature21072-f3 — (from paper): a, Lateral, hind and ventral views. b, The most parsimonious tree (tree length, 96; consistency index, 0.6771; retention index, 0.8394; rescaled consistency index, 0.5683) arising from a matrix of 25 taxa and 61 characteristics. The values at nodes indicate bootstrap support greater than 50% (see Supplementary Information for details).

Here’s a figure from a 2004 Nature paper showing the truncated cones (A and C) in some vestulocystids:

Finally, where the fossil was found and the appearance of the sediments (it must have been hard to spot these!):

nature21072-sf1 — Caption from paper: Geographical location of horizon and its petrography. (836 KB) a, Locality map of the Zhangjiagou section, Xixiang, Shaanxi Province, China. In addition to Saccorhytus, the phosphatic limestone of Bed 2 of the Kuanchuanpu Formation in the Zhangjiagou section (see ref. 16) contains numerous small shelly fossils. b, c, Petrographic sections (plane-polarized light) of Bed 2 showing the phosphatic bioclastic grains, carbonate matrix and cements.

The authors conclude that our earliest deuterostome ancestosr might well have been tiny and lived among sand grains of the sea floor; they were “meiofaunal”, meaning small bottom-dwelling animals that inhabit the sediments. They also conclude that since these species could have been very tiny, we may have missed even earlier appearances of deuterostomes in the fossil record. Finally, they conclude that respiration occurred through the body surface, and the presence of pharyngeal arches (structures bearing gill slits), which are present in all modern deuterostomes at some developmental stage, could have evolved later.

h/t: Gregory
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Han, J., S. C. Morris, Q. Ou, D. Shu, and H. Huang. 2017. Meiofaunal deuterostomes from the basal Cambrian of Shaanxi (China). Nature advance online publication. doi:10.1038/nature21072

A new order of insect found in Cretaceous amber

January 29, 2017 • 10:15 am

There are about 30 orders of insects (see here), usually ending with the letters “-ptera”. You should know some of these, including Lepidoptera, Coleoptera, Orthoptera, Hemiptera (“true bugs”), Diptera (FLIES!), Hymenoptera (ants, bees, and wasps), and as many of the others as your brain can hold. Rarely do we find a new one, as most of these are large, well-studied groups. But of course there are many extinct insects to be found, and the 1 million or so living species already described must be but a small fraction of all species still with us.

However, a new paper by Georger Poinar Jr. and Alex Brown in Cretaceous Research (reference below, access free), identifies a bizarre insect that doesn’t fit into any existing or extinct order, and thus has been placed in an order of its own. (See also the Oregon State University writeup, which is where first author Poinar works).

The insect, named Aesthiocarenus burmanicus, and assigned to the new order Aethiocarenodea, was found in amber excavated in Burma, and has been dated at about 99 million years ago, in the mid-Cretaceous. Here’s a picture of the thing, and what is unusual is its “triangular head with bulging eyes,” described in the paper as an isoceles triangle with the hypotenuse being the front of the head. This kind of head is absolutely unique in all known insects.

The creature is small (3-4 mm long) and wingless, but it’s a female, and we have no idea what the male looks like. But the degree of preservation in amber (remember, the bug got trapped in tree resin that then became amber) is remarkable.

The shape of the head, and narrow neck, lead the authors to speculate that this organism could move each eye through 180°, giving it really good vision. Notice the dorsoventral flattening:

Microsoft Word - ycres_3501_Revision unmarked Poinar-Brown_V2 — (from paper): Holotype of Aethiocarenus burmanicus gen. et sp. nov. in Myanmar amber. A. Dorsal view of entire specimen. Scale bar = 1.5 mm. B. Dorsal view of head, neck and anterior portion of pronotum. Scale bar = 0.4 mm. C. Lateral view of entire specimen. Scale bar = 1.1 mm.

Because of its shape and winglessness, the authors suggest its lifestyle:

Based on the non-specialized mouthparts, A. burmanicus gen. et sp. nov. was probably omnivorous. The narrow, flattened body suggests it could have explored bark fissures and epiphytes on tree surfaces. Wings would have been a hindrance in such a habitat. The long slender polymerous antennae were probably used to explore the surroundings and the long, slender legs indicated that it could move quickly if threatened.

This figure shows two interesting features: a weird pattern of bristles on the thorax (arrows in vertical panel to the left, A), whose function is unknown, and some kind of secretory glands at the base of head shown in lower left panel (C). These glands apparently produced an exudate (globules indicated by arrows at bottom) when the insect found itself trapped in the resin. As the paper notes:

The dorsal neck glands presumably were used for defense. Evidence that these glands were secretory is the presence of two spherical bodies with irregular borders adjacent to the paired glands (Fig. 2C). These spherical bodies are considered to represent secretions released when the fossil entered the resin.

This specimen is a female, as shown by the “gonopore” on the bottom of the abdomen (below). The authors note that it’s not clear whether a male, of which there are as yet no specimens, would have a head of the same shape, or might even have wings. (As we learned yesterday, sexual selection can sometimes cause big differences between the sexes in head shape).

screen-shot-2017-01-27-at-1-16-10-pm — F. Gonopore (arrow) on ventral sternite. (Female genitalia). Scale bar is 130 microns (0.13 mm)

Finally, is this related to any insects we know? The authors point out that the specimen has some features of one suborder of dermapterans (earwigs), but don’t share other features, so for now this order stands alone—with unknown genealogical affinities.

h/t: Dom

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Poinar Jr, G. and A. E. Brown. 2016. An exotic insect Aethiocarenus burmanicus gen. et sp. nov. (Aethiocarenodea ord. nov., Aethiocarenidae fam. nov.) from mid-Cretaceous Myanmar amber. Cretaceous Research 72: 100-104

Some evidence that life may have originated at least 4.1 billion years ago

April 29, 2016 • 10:30 am

For some reason I missed this paper published last November in Proc. Nat. Acad. Sci. USA by Elizabeth Bell et al. , and it doesn’t seem to have been given a lot of attention by the press. That may be because its conclusions are questionable, and based on a very small sample. But if they’re right, it’s a pretty amazing result, for the authors report the presence of what may be biogenic carbon—that is, carbon derived from living organisms—from the Jack Hills of western Australia, and that carbon was dated at 4.1 billion years old. Since the Earth is about 4.54 billion years old, and the zircons of the Jack Hills are the oldest known material of terrestrial origin on our planet (4.4 billion years is the oldest sample), the finding of biogenic life in zircons dated at 4.1 billion years means that life may have originated very, very soon after the Earth formed. But these findings are preliminary.

The oldest widely accepted evidence of life on Earth are 3.4 billion year old microfossils from the cratons of the Strelley Pool formation, also from Western Australia. (Old, stable parts of the Earth are called “cratons.”) To get older evidence than that, you have to date and do isotopic analysis of flecks of graphite that may be derived from organisms. The oldest carbon generally accepted as being of biological origin is about 3.8 billion years old.

The dating is done by radiometrically dating the minerals containing graphite (carbon) flecks (usually zircon derived from melting earlier “mud rocks” that presumably contained organismal remains), and the biogenic origin is studied by looking at the amounts of carbon 13 versus carbon 12 in the flecks. Non-organismal carbon has a relatively higher amount of carbon 13 than does biogenic carbon.(The different ratios come from the fact that organisms absorb atmospheric carbon into their bodies, which is higher in carbon-12 than inorganic carbon). The values of these isotopes are transformed into a statistic called δ¹³C; δ¹³C values of 24 or lower are generally assumed to be signatures of carbon derived from organisms.

At any rate, Bell et al. dated zircons found in the Jack Hills. One of them contained carbon flecks (and was crack-free, so the graphite didn’t insinuate itself after the zircon was formed); and for that sample they determined the average δ¹³C of the flecks using spectral analysis.

Here’s the prepared zircon with the flecks inside. The bar is 30 microns long, or about a thousandth of an inch.

F1.medium — Fig. 1. (from paper) Transmission X-ray image of RSES 61-18.8 with graphite indicated. (Inset) Raman spectra for the top inclusion and for an epoxy “inclusion” from another investigated zircon. The broadened “D-band” at ∼1,400 cm−1 indicates disordered graphite (39); C–H stretch bands at ∼2,800–3,100 cm−1 (39) are observed in epoxy but not graphite.

And here’s the average value of δ¹³C (triangle) for the Jack Hills sample, compared with the ratios for 3.8-billion-year old graphite that is widely accepted as being organic in origin. The average value of the Jack Hills carbon was -24, so it’s within the range of organic carbon; i.e. life might have been around by 4.1 billon years ago. That would extend the origin of life back another 300 million years beyond what we know, so that life may have originated no more than 500 million years after the Earth formed.

Screen Shot 2016-04-29 at 9.54.26 AM — Fig. 2 (from paper) δ13C for Eoarchean–Hadean carbon samples measured via SIMS vs. host mineral age compared with inorganic and organic carbon (organic carbon values from ref. 13; inorganic from ref. 14).

Now the authors note that there are other processes that could produce low values of δ¹³C, including the Fischer-Tropsch chemical process, carbon derived from meteorites, isotope fractionation by diffusion, and so on, but they claim that a biogenic origin is “at least as plausible” as these (not a strong statement!).

I won’t go write further, as I only wanted to call your attention to some tantalizing evidence that life may have been around a lot earlier than we thought. Whether this becomes widely accepted will take a while—and much more work. After all, this paper is based on just a single sliver of zircon. If you want to see the entire paper, and can’t get it from the link below, just ask.

h/t: Latha Menon

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Bell, E. A., P. Boehnke, T. M. Harrison, and W. L. Mao. 2015. Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon. Proceedings of the National Academy of Sciences 112:14518-14521.

Readers’ wildlife photographs

April 27, 2016 • 7:30 am

As I mentioned when in Portland, I encountered reader Bruce Thiel at my free will talk; Bruce’s avocation is preparing fantastic fossils that he finds locally. I’ve featured some of his preparations before; have a look, as I’ve never seen anything like them. Using a dental drill and working slowly and meticulously, he produces fossils like the ones below, whose photos just arrived in my email. (Go here to see how a preparation proceeds.) He doesn’t sell them, though preparations like this fetch high prices; instead, Bruce gives them to museums and scientists to study. So let’s have a paleontological “readers’ wildlife” today. Bruce’s notes are indented:

Here are some other interesting crabs I’ve prepared. Background information about the fossils and the discovery and preparation procedure can be found here [JAC: the second link above].

All the crabs shown are about 30 million years old and are Pulalius vulgaris, except for the last picture. This crab in the next two pictures was mashed and not particularly well-preserved—until I got to the eyestalks and claws, so I went as close as I could between the claws. The eyestalks are 1.5cm apart–slightly over 1/2 inch—so there was not a lot of working area.

The next crab was one of three given to the Smithsonian. What looks like googly-eyes are two attached barnacles.

The next two crabs host tube worms, and are at Kent State being studied for epibionts. The chip in the middle of the carapace is what fossils preparers call “the mark of discovery.” Most of the round or oval-shaped concretions are blank or contain bits of wood, shell or decomposed organic material. In working down into the middle of the rock with the pneumatic jackhammer to see what they contain, if one is too aggressive or not paying close attention, one can “nick” the shell with the pneumatic tool as I did in this case. Both crabs have interesting snake-shaped worms lurking on their shell. One of the questions experts would like to answr is if the worms attach while the crab was alive or after death and during decomposition.

This is one of the smaller crabs I’ve worked on. I held my breath when uncovering the tiny claw. My thumbnail is shown for comparison.

These are two Macroacaena schencki crabs from the Keasey Formation, Oregon (33 – 35 MYO). We think the larger and wider of the two is female but determination awaits further research.

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