Strange bedfellows

There's a Senegalese expression that goes, "There are forty kinds of lunacy, but only one kind of common sense."

The outcome of this general principle is that trying to support pseudoscientific claims sometimes forces alliances between groups you'd never think would have anything in common -- such as the cryptozoologists and the young-Earth creationists teaming up to find evidence of the "Mokèlé-Mbèmbé," a water-dwelling beastie that supposedly lives in the Congo River Basin.

The first written account of the Mokèlé-Mbèmbé seems to be from science writer (and cryptozoology buff) Willy Ley in his 1941 book The Lungfish and the Unicorn, but his description was (he said) taken from an unpublished report written by German military officer and explorer Ludwig Freiherr von Stein zu Lausnitz, who was summarizing sightings by natives he'd spoken to in Cameroon.  Here's what Ley had to say:

The animal is said to be of a brownish-gray color with a smooth skin, its size is approximately that of an elephant; at least that of a hippopotamus.  It is said to have a long and very flexible neck and only one tooth but a very long one; some say it is a horn.  A few spoke about a long, muscular tail like that of an alligator.  Canoes coming near it are said to be doomed; the animal is said to attack the vessels at once and to kill the crews but without eating the bodies.  The creature is said to live in the caves that have been washed out by the river in the clay of its shores at sharp bends.  It is said to climb the shores even at daytime in search of food; its diet is said to be entirely vegetable.  This feature disagrees with a possible explanation as a myth.  The preferred plant was shown to me, it is a kind of liana with large white blossoms, with a milky sap and apple-like fruits.  At the Ssombo River I was shown a path said to have been made by this animal in order to get at its food.  The path was fresh and there were plants of the described type nearby.  But since there were too many tracks of elephants, hippos, and other large mammals it was impossible to make out a particular spoor with any amount of certainty.

So already we're talking about a third-hand account; Ley recounting what he'd read that von Stein had written about what natives told him.  Ley also quotes one Lieutenant Paul Gratz, who is not a lot more convincing:

The crocodile is found only in very isolated specimens in Lake Bangweulu, except in the mouths of the large rivers at the north.  In the swamp lives the Nsanga, much feared by the natives, a degenerate saurian which one might well confuse with the crocodile were it not that its skin has no scales and its toes are armed with claws.  I did not succeed in shooting a Nsanga, but on the island of Mbawala I came by some strips of its skin.

Ley says that the Mokèlé-Mbèmbé and the Nsanga are the same, which I guess is true because it's very likely that neither one is real.  Skeptic Donald Prothero dismisses alleged sightings of the Mokèlé-Mbèmbé as being either crocodiles, black rhinos, or simply overactive imaginations, and I'm inclined to agree with him.  The only alleged photograph of the beast, taken by explorer Rory Nugent in 1985, is almost certainly a distant snapshot of a floating log.

A sketch of a Mokèlé-Mbèmbé, which I have to admit looks nothing like either a crocodile or a rhino, but does appear to have been heavily influenced by watching The Land Before Time [Image is in the Public Domain]

So the whole thing would be in the same category as Bigfoot and Nessie and Mothman et al. -- but then the creationists got involved.

Scottish explorer and young-Earth creationist William Gibson funded and led two expeditions into the Congo River Basin to try to prove the Mokèlé-Mbèmbé exists, although how this would support creationism is beyond me.  Maybe it's because the creationists have asserted for years that humans coexisted with dinosaurs, and that the dinosaurs went extinct because they all missed getting on the Ark or something, so having one around today would mean we still coexist.  Q.E.D.

Hey, don't yell at me.  I'm not claiming it makes sense, I'm just telling you about it.

A highly scientific artist's conception of prehistory, as per the Creation Museum

In general, it's hard to see how the existence of "living fossils," organisms long thought to be extinct that have proven to be very much alive -- the coelacanth inevitably comes to mind -- is any kind of cogent argument against evolution, but the sad fact is that your average creationist wouldn't know a logical train of thought if it came up and bit them on the ass.  Be that as it may, the creationists are all in on the Mokèlé-Mbèmbé, with the general consensus being if one is discovered, all the evolutionary biologists will retreat in disarray and immediately join evangelical Christian churches.

So we have here a case of strange bedfellows -- the cryptozoologists, who are generally well-meaning even if they have a different standard for what constitutes reliable evidence than I do, are on the same team as the young-Earth creationists, who by and large want to turn the entire world into an autocratic Christian theocracy.

Me, I think it'd be cool if Mokèlé-Mbèmbé existed, but purely because it'd be a fascinating new area of biological study.  Sadly, the fact that there's exactly zero evidence other than hearsay (which, after all, isn't really evidence at all) argues against it.  For those of you who were hoping for confirmation of a Brachiosaurus lumbering around in the Congo Basin, I'm afraid it's kind of a non-starter.

And that goes double for those of you who think Adam and Eve had a pet velociraptor.

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Footprints in the sand

What comes to mind when you think about the Isle of Skye?

Chances are, it's one of three things.

The first is the stunningly beautiful scenery.  It's the largest of the Inner Hebrides, and is noted for its rugged, rocky hills, craggy coastline, and emerald-green meadows.

Sidney Richard Percy, Loch Coruisk (1874) [Image is in the Public Domain]

Second, history buffs will remember Skye as the place where "Bonnie Prince Charlie" (Charles Edward Stuart) fled, with the help of Flora MacDonald, after Scotland's devastating loss at the Battle of Culloden.  Stuart's repeated attempts afterward to claim the thrones of England and Scotland never came to much.  He died in exile in Rome in 1788 at the age of 67, depressed and miserable -- but even today, he remains a symbol to many Scots of "what might have been."

Third, if you're someone who likes to indulge in a wee dram on occasion, you probably know that it's home to the famous Talisker and Torabhaig distilleries, which produce absolutely fantastic single-malt whiskies.

I doubt, somehow, that many people would come up with a fourth thing that Skye should be famous for, and which was the subject of a paper in PLOS-One this week: it is one of the best sites for middle-Jurassic age fossils in the world.

167 million years ago, Scotland was about at the latitude of the Tropic of Cancer, and was a hot, lush swampy rainforest.  Prince Charles's Point -- the place where Bonnie Prince Charlie supposedly landed after making it safely "over the sea to Skye," in the words of the Skye Boat Song -- was a shallow, sandy-bottomed lagoon.

And it was home to some big dinosaurs.

The paper describes tracks by huge, long-necked sauropods like Cetiosaurus -- and those of the carnivorous theropods that hunted them, such as Megalosaurus.

A complete Cetiosaurus skeleton found near Rutland, England  [Image licensed under the Creative Commons Paul Stainthorp from United Kingdom, Cetiosaurus mount, CC BY-SA 2.0]

The Cetiosaurus tracks are as big around as car tires, and the study found individual trackways twelve meters long -- made, the researchers said, by dinosaurs ambling about, probably in search of the huge amounts of food it took to keep an animal that size going.

It's hard to imagine the rugged, windswept islands of the Hebrides like they were then -- something more like today's Florida Keys, and the home to the whole assemblage of mid-Mesozoic fauna.  Not only the big theropods and sauropods, such as the ones that left the footprints on the Isle of Skye, but pterodactyls flying overhead, and in the seas, the superficially dolphin-like icthyosaurs -- and the long-necked plesiosaurs that still come up in conversations about Loch Ness, only a hundred miles east as the Rhamphorhynchus flies.

"O Earth, what changes hast thou seen?" Tennyson mused -- "There, where the long road roars, has been the stillness of the central sea."  And those changes are still occurring.  The Atlantic Ocean is still progressively widening; a complex series of faults is making all of the Anatolian region twist counterclockwise; the "Horn of Africa" is rifting away from the rest of the continent and eventually will drift off into the Indian Ocean; Australia is on a collision course with Southeast Asia.  We humans leave our own footprints in the sand, but how ephemeral are they?  Will paleontologists 167 million years from now know of our presence, from traces left behind on whatever configuration the continents will then have?

It recalls the haunting lines from another poet, Percy Bysshe Shelley, which seems a fitting place to end:

I met a traveller from an antique land
Who said: Two vast and trunkless legs of stone
Stand in the desert.  Near them, on the sand,
Half sunk, a shattered visage lies, whose frown,
And wrinkled lip, and sneer of cold command,
Tell that its sculptor well those passions read
Which yet survive, stamped on these lifeless things,
The hand that mocked them, and the heart that fed.
And on the pedestal these words appear:
"My name is Ozymandias, King of Kings:
Look on my works, ye Mighty, and despair!"
Nothing beside remains.  Round the decay
Of that colossal wreck, boundless and bare
The lone and level sands stretch far away.

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Taking flight

One of the many things I find fascinating about the evolutionary model is how different lineages can happen on the same "solution" to the problems of surviving and reproducing, leading to similarities cropping up that don't result from common ancestry.  This is a phenomenon called convergent evolution, and explains why the North American flying squirrel and Australian sugar glider look a lot alike, even though they are only distantly related.  (The flying squirrel is a rodent, and the sugar glider a marsupial more closely related to kangaroos.)

I put the word "solution" in quotes and use it with caution, because this makes it sound like evolution is forward-looking, which it is not.  As Richard Dawkins explains brilliantly in his book The Blind Watchmaker, to trigger evolution, all you have to have is an imperfect replicator (in this case, DNA) and a selecting agent.  To phrase it more like Darwin would have put it: variation coupled with differences in survival rate.

I recall how surprised I was to learn that the eye has actually evolved multiple times.  Starting with light-sensitive spots, such as you still find today in many microorganisms, variations on different lineages came up with a variety of different "solutions" -- the pinhole-camera eye of a chambered nautilus, the cup-shaped eye of a flatworm, the compound eye of a fly, and our own eye with a transparent lens like that of a refracting telescope.  All these adaptations work just fine for the animal that has them.  (Eye formation in a number of species is controlled by the paired-box 6 [PAX6] gene, without which eyes won't form at all.  It's such a critical gene that it is conserved across thousands of species -- in fact, your PAX6 gene and a mouse's are identical, base-pair-for-base-pair.)

The reason this subject comes up is because of some research published in the journal Current Biology that showed another trait -- flight -- not only evolved separately in groups like insects and birds, but even in the dinosaurian ancestors of today's birds, it evolved more than once.

A team led by paleontologist Rui Pei of the Chinese Academy of Sciences analyzed bone and feather structure of various dinosaur groups to see if they flew, glided, or were using their feathers for a different purpose (such as keeping warm).  To their surprise, it was found that multiple lineages were capable of flying, or nearly so.  The authors write:

We [used] an ancestral state reconstruction analysis calculating maximum and minimum estimates of two proxies of powered flight potential—wing loading and specific lift.  These results confirm powered flight potential in early birds but its rarity among the ancestors of the closest avialan relatives (select unenlagiine and microraptorine dromaeosaurids).  For the first time, we find a broad range of these ancestors neared the wing loading and specific lift thresholds indicative of powered flight potential.  This suggests there was greater experimentation with wing-assisted locomotion before theropod flight evolved than previously appreciated.  This study adds invaluable support for multiple origins of powered flight potential in theropods (≥3 times), which we now know was from ancestors already nearing associated thresholds, and provides a framework for its further study.

Here are their results, in graphical form:

As you can see, actual birds -- labeled "Later-diverging avialans" near the bottom of the tree -- were far from the only ones to have flight capability.  Rahonavis, Microraptor, and several of the anchiornithines were probably fliers, and only the last mentioned is on the same clade as today's birds.

Flying is pretty useful, so it's no wonder that when feathers evolved from scales -- probably, as I mentioned earlier, in the context of warmth and insulation -- it was only a small step remaining toward lengthening those feathers to the point that their owners could catch a breeze and glide.  After that, the same kind of refinement took over that happened with the eye, and eventually, you have true flight.

So that's yet another cool bit of research about prehistory.  Wouldn't you like to know what those prehistoric fliers looked like?  I'd love to see them.  From a distance, because a lot of them were predators.  For example, Microraptor is Greek for "tiny hunter," and were a little like miniature velociraptors with wings.

If you wanted an image to haunt your dreams.

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The titan

One thing science teaches us is that just about everything is interesting if you look at it carefully enough.  Still, there's an ingrained human tendency to be overawed by superlatives -- the biggest, the heaviest, the brightest, the strongest, the most powerful.

It's why a recent fossil discovery from Somerset, England has made the headlines.  The rocks in Somerset, in the southwest of England, are mostly of Triassic age; it's not far from the famous "Jurassic Coast," which begins around Exmouth with Triassic sedimentary rocks that gradually become younger as you head west.  It's the site that the brilliant nineteenth century paleontologist Mary Anning studied -- becoming one of a very long list of talented women scientists who struggled for recognition by their male peers with tragically little success.

Somerset, which is a bit north from there, is also a great site for Mesozoic fossils, and some amateur fossil hunters recently found a doozy.  Father-and-daughter team Justin and Ruby Reynolds were searching along the north Somerset coast and saw what turned out to be a fossilized jawbone...

... of a creature which is estimated to have been twenty-five meters long.  (For my fellow Americans, twenty-five meters is about 130 bananas long.)

The animal was a type of ichthyosaur, a group that reached their height of diversity in the late Triassic Period.  We've known for a long time that ichthyosaurs were bizarre animals.  They were streamlined predators that look remarkably like dolphins, although they are only distantly related (making the two groups a great example of convergent evolution).  A number of them had an even stranger feature, which is the largest eye-diameter-to-body-size ratio of any animal known -- the well-named Ophthalmosaurus (Greek for "eye lizard") was six meters long and had eyes the size of basketballs.

But this new species could have eaten an Ophthalmosaurus as an appetizer and still had plenty of room for the entrée.  It's been dubbed Ichthyotitan severnensis -- more or less, "gigantic fish-thing from the Severn."  The fossil dates to about 202 million years ago.

[Image credit: artist Sergey Krasovskiy]

"I was highly impressed that Ruby and Justin correctly identified the discovery as another enormous jawbone from an ichthyosaur," said Dean Lomax, paleontologist at the University of Manchester, who verified the find and helped to classify it, in an interview with Science Daily.  "They recognized that it matched the one we described in 2018. I asked them whether they would like to join my team to study and describe this fossil, including naming it.  They jumped at the chance.  For Ruby, especially, she is now a published scientist who not only found but also helped to name a type of gigantic prehistoric reptile.  There are probably not many fifteen-year-olds who can say that!  A Mary Anning in the making, perhaps."

The Ichthyotitan, though, was one of the last of its kind; it, and a great many other species, were victims of the Late Triassic Mass Extinction, a poorly-understood extinction event that occurred around 201 million years ago and was only slightly smaller than the much better-known Cretaceous-Tertiary Extinction that would happen 135 million years later.  The most likely explanation of the Late Triassic event is volcanism and outgassing from the Central Atlantic Magmatic Province, the mantle upwelling from which would ultimately split up Pangaea and open the Atlantic Ocean, but that point is still being argued over by geologists and paleontologists.

Whether this particular Ichthyotitan was killed during the extinction event itself is, of course, impossible to tell, but the fossil dates to almost exactly the right time.  Its discovery also ramps up the search for more fossils along the north Somerset coast.  "It is quite remarkable to think that gigantic, blue whale-sized ichthyosaurs were swimming in the oceans around what was the UK during the Triassic Period," Lomax said.  "These jawbones provide tantalizing evidence that perhaps one day a complete skull or skeleton of one of these giants might be found.  You never know."

It's a hell of a find -- a bone from a creature in contention for the largest animal known.  I don't know about you, but it's hard even to imagine a predator that big.  The late Triassic must have been an impressive-looking place...

... observed, of course, from a safe distance.

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Wings over Skye

I know it seems like I keep ringing the changes on this topic over and over, but... it never fails to astonish me how much the Earth has changed over geologic history.

Part of my fascination, I think, comes from the fact that this knowledge is so at odds with how it feels to be an actual inhabitant of the planet.  When you look around, it seems like things are pretty static.  Oh, there are changes -- volcanoes and earthquakes come to mind -- but however catastrophic those can be for local residents, the fact remains that they are, on a planetary scale, tiny effects.  To see the big shifts requires a much longer time axis, but if you have the perspective of one...

... wow.

Take, for example, the discovery of new species of pterosaur in one of the last places I can picture a pterosaur flying -- the Isle of Skye, Scotland.  Now a cool, windswept, rocky island chain with few trees and lots of grass and heather, the Hebrides (and the rest of the British Isles) were, during the Jurassic Period, a lush subtropical land only separated from what would become North America and Greenland by a shallow strait of ocean.

The configuration of the continents at the mid-Jurassic [Image credit: Ron Blakey, NAU Geology]

And flying over the forests of Jurassic Scotland were some of the coolest prehistoric beasts ever, the pterosaurs.

Dubbed Ceoptera evansae -- the genus name means "mist flyer," from the Gaelic word ceò, mist, which also gives the Isle of Skye its Gaelic name of Eilean a'Cheò, "misty island" -- the newly-discovered fossil was found in the Kilmaluag Formation and dated to about 167 million years of age.  Ceoptera was a smallish pterosaur, measuring about sixty centimeters from beak to tail tip:

[Image credit: Elizabeth Martin-Silverstone et al., Journal of Vertebrate Paleontology]

The era when Ceoptera was flying over the Isle of Skye was a point of great diversification amongst the pterosaurs, a process which would accelerate during the rest of the Jurassic and into the Cretaceous, ultimately resulting in species from fifty-centimeter-long Sordes pilosus to the six-meter-wingspan Quetzalcoatlus northropi.  Eventually, however, the entire taxon would be wiped out in the Cretaceous-Tertiary Extinction of sixty-six million years ago.

"The time period that Ceoptera is from is one of the most important periods of pterosaur evolution, and is also one in which we have some of the fewest specimens, indicating its significance," said Elizabeth Martin-Silverstone of the University of Bristol, who led the study, in an interview with Science Daily.  "To find that there were more bones embedded within the rock, some of which were integral in identifying what kind of pterosaur Ceoptera is, made this an even better find than initially thought.  It brings us one step closer to understanding where and when the more advanced pterosaurs evolved."

For me, the coolest part is trying to picture what the world looked like back then.  Even with our knowledge of plate tectonics and the fossils we have available for study, we still have only the shadowiest image of the Jurassic world.  Consider what doesn't fossilize -- colors, sounds, smells, behavior.  We can make some guesses about what those were like based upon modern organisms, but guesses they will always be, and many of them significantly off the mark.  (If you want a good laugh some time, look into "prehistoric animals that were reconstructed wrong" and find out how wildly inaccurate even the experts can be.  Fortunately, science self-corrects, and the fact that we now know they were wrong comes from better fossils and more sophisticated analysis -- but even so, we still have a vague and incomplete picture of what things were really like back then.  Oh, for a time machine...)

So that's our flight of fancy for today.  Prehistoric wings over the Isle of Skye.  Makes you wonder what things will look like in another 160 million years or so.  We'll have a whole new set of "endless forms most beautiful and most wonderful," to use Darwin's trenchant words -- ones we could not even begin to predict.

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Lords of the air

Ever since I was a kid, my favorite group of dinosaurs has been the pterosaurs.

These are one of the six groups of animals that independently evolved flight, or at least significant capacity for gliding (the others are insects, birds, bats, flying squirrels, sugar gliders, and colugos).  They had incredible diversity at their height, during the Jurassic and Cretaceous Periods, from the pint-sized Sordes pilosus (with a sixty-centimeter wingspan) to the almost unimaginably huge Quetzalcoatlus northropi (with a ten-meter wingspan, as big as a light plane).

Most of them were probably clumsy on the ground -- it's hard to imagine how Quetzalcoatlus got off the ground -- but in the air, they were nimble, maneuverable, and fast.  The smaller ones were probably insect-eaters; the larger ones likely fed on fish, although a terrestrial diet of small reptiles and mammals is also possible. 

What brings all this up is the discovery of a new species of pterosaur, one of dozens that have been identified from the Jehol Biota, a stupendous fossil deposit in northeastern China near Huludao.  This fossil bed has produced not only pterosaurs but incredibly well-preserved species of prehistoric birds and other vertebrates -- it's like a tapestry of late Cretaceous animal life.

"Pterosaurs comprise an important and enigmatic group of Mesozoic flying reptiles that first evolved active flight among vertebrates, and have filled all aerial environmental niches for almost 160 million years," said Xiaolin Wang, of the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences, who co-authored the paper describing the discovery.  "Despite being a totally extinct group, they have achieved a wide diversity of forms in a window of time spanning from the Late Triassic to the end of the Cretaceous period.  Notwithstanding being found on every continent, China stands out by furnishing several new specimens that revealed not only different species, but also entire new clades."

This includes the newly-discovered Meilifeilong youhao, belonging to the family Chaoyangopteridae, which is represented at the site by two other species that have been found nowhere else.

Meilifeilong looked like something out of a nightmare, if the artist's reconstruction is accurate (and probably even if it isn't):

[Image courtesy of artist Maurilio Oliveira]

The name means "beautiful flying dragon," which I doubt is what I'd say if I saw one, but what I'd say is borderline unprintable so we'll leave it at that.

It's astonishing to think of how long these creatures ruled the skies -- from the late Triassic until the very end of the Cretaceous, a time span of around 160 million years.  Had change not come in the form of the Chicxulub Meteorite collision, they might well still be here, soaring on thermals above our forests and lakes and oceans, the undisputed lords of the air.  And even if we now know them only from fossils, they still can't help but impress.

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A new view of the "eye lizard"

I am forever astonished at the level of detail we can infer from fossils that are hundreds of millions of years old.

The most recent example of this came from analysis of a fossil of Stenopterygius, an ichthyosaur that lived during the Jurassic Period (this particular fossil has been dated to about 180 million years ago).  We usually think of fossils as preserving bones and teeth, and occasionally impressions of scales or skin or feathers -- but this one was so finely preserved that researchers have been able to make some shrewd inferences about color, metabolism, and the structure of soft tissues.

Artist's conception of Stenopterygius [Image licensed under the Creative Commons Nobu Tamura (http://spinops.blogspot.com), Stenopterygius BW, CC BY-SA 3.0]

We've known for a long time that ichthyosaurs are bizarre animals. They were streamlined predators that look remarkably like dolphins, although they are only distantly related (making the two groups a great example of convergent evolution).  A number of them had an even stranger feature, which is the largest eye-diameter-to-body-size ratio of any animal known -- the well-named Ophthalmosaurus (Greek for "eye lizard") was six meters long and had eyes the size of basketballs.

Stenopterygius was a bit smaller, with an average adult size of four meters.  But up until recently, all we've been able to do is speculate on what it might have looked like, and how it behaved.  A discovery in Germany, described in a paper in Nature called "Soft-Tissue Evidence for Homeothermy and Crypsis in a Jurassic Ichthyosaur" and authored by no fewer than 23 scientists, has given us incredibly detailed information on these oddball dinosaurs.

The authors write:

Ichthyosaurs are extinct marine reptiles that display a notable external similarity to modern toothed whales.  Here we show that this resemblance is more than skin deep.  We apply a multidisciplinary experimental approach to characterize the cellular and molecular composition of integumental tissues in an exceptionally preserved specimen of the Early Jurassic ichthyosaur Stenopterygius.  Our analyses recovered still-flexible remnants of the original scaleless skin, which comprises morphologically distinct epidermal and dermal layers.  These are underlain by insulating blubber that would have augmented streamlining, buoyancy and homeothermy.  Additionally, we identify endogenous proteinaceous and lipid constituents, together with keratinocytes and branched melanophores that contain eumelanin pigment.  Distributional variation of melanophores across the body suggests countershading, possibly enhanced by physiological adjustments of colour to enable photoprotection, concealment and/or thermoregulation.  Convergence of ichthyosaurs with extant marine amniotes thus extends to the ultrastructural and molecular levels, reflecting the omnipresent constraints of their shared adaptation to pelagic life.

So from a 180-million-year-old fossil, we now know that Stenopterygius (1) was a homeotherm (colloquially called "warm-blooded"), (2) had a blubber layer much like modern dolphins and whales, and (3) were countershaded -- dark on top and light underneath, to aid camouflage -- similar to dozens of species of modern fish.

This level of preservation is extremely unusual.  "Both the contour of the body and the remains of internal organs are clearly visible," said paleontologist Johan Lindgren of the University of Lund, who co-authored the paper.  "Surprisingly, the fossil is so well preserved that it is possible to observe individual cell layers inside the skin."

"This is the first direct chemical evidence of warm blood in an ichthyosaur, because a subcutaneous fat layer is a characteristic of warm-blooded animals," said Mary Schweitzer of North Carolina State University, also a co-author.  "Ichthyosaurs are interesting because they have many features in common with dolphins, but they are not related at all to these mammals that inhabit the sea.  But the enigma does not stop there...  They have many characteristics in common with living marine reptiles, such as sea turtles; but we know from the fossil record that they gave live birth to their young...  This study reveals some of those biological mysteries."

Which is pretty astonishing.  I've always had a fascination for the prehistoric world, and have spent more time than I like to admit wondering what it might have been like to live in the Jurassic world. This research gives us one more piece of information -- about a fierce prehistoric predator that shared some amazing similarities to creatures that still swim in our oceans.

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Parallel problem solving

One of the many fascinating aspects of evolution is how nature happens upon the same solutions to environmental problems, over and over.

Two of the best examples of this are eyes and wings.  True eyes evolved from simple photoreceptive spots at least four times: the vertebrate eye, with its complex system of lenses and retinas; the pinhole-camera eyes of the chambered nautilus and other cephalopods; the compound eyes of insects; and the rows of separate spherical eyes in clams and scallops.  Wings, on the other hand, evolved independently no fewer than six times: bats, birds, insects, pterosaurs, flying squirrels, and colugos (the last two count if you include gliding along with true powered flight).

The reason is simple.  There are a handful of problems animals have to overcome (perception/sensation, nutrition, reproduction, locomotion, avoiding environmental dangers, and avoiding predation) and a limited number of ways to accomplish them.  Once (for example) photoreceptive eyespots develop in an animal, natural selection for improving the sensitivity of those spots takes over, but how exactly you do that can differ.  The result is you end up with vision evolving over and over, and each time, the organ is structured differently, but accomplishes the same thing.

Evolution, it seems, is the law of whatever works.

This has interesting implications about what extraterrestrial life might look like.  I very much believe that certain features will turn out to be constrained in any conceivable species -- the presence of locomotor organs, organs sensitive to sound, light, heat, and touch, and so on -- but also, that the way those organs are arranged and configured could be very differently from anything we have on Earth.

This "multiple solutions to the same problems" idea is what immediately came to mind when my friend and fellow writer Gil Miller, whose inquisitive mind and insatiable curiosity have provided me with many a topic here at Skeptophilia, sent me a link from Phys.org about hollow bones in dinosaurs.  Endoskeletons such as our own exist in an interesting tension.  They have to be solid enough to support our weight, but the better they are at weight-bearing, the heavier they themselves are.  The mass of an animal in general increases much faster than its linear dimensions do; double a mouse's height, keeping its other proportions the same, and it will weigh about eight times as much.  This is why in order for the whole system to work, the proportions have to change as species increase in size.  A mouse's little matchstick legs would never work if you scaled it up to be as big as a dog; at the extreme end, consider the diameter of an elephant's legs in relation to its size.  Anything narrower simply wouldn't support its weight.

[Nota bene: this is why if you were traumatized when young by bad black-and-white horror movies about enormous insects wreaking havoc, you have nothing to worry about.  If you took, for example, an ant, and made it three meters long, its proportionally tiny little legs would never be able to lift it.  The worst it could wreak would be to lie there on the ground, helpless, rather than eating Tokyo, which is what the horror movie monsters always did.  One got the impression the inhabitants of Tokyo spent ten percent of their time working, relaxing, and raising families, and the other ninety percent being messily devoured by giant radioactive bugs.]

But back to the Phys.org article.  A detailed analysis of the bone structure of three different dinosaur lineages -- ornithischians, sauropodomorphs, and herrerasaurids -- found that while all three had landed on the idea of internal air sacs as a way of reducing the mass of their large bones, the structures of each are different enough to suggest all three evolved the feature independently.  Once again, we have an analogous situation to eyes and wings; identical problem, parallel solutions.  The problem here is that large body size requires heavy bones that require a lot of energy to move around, and the solution is to lighten those bones by hollowing them out (while leaving the interstices connected enough that they're still structurally sound).  And three different clades of dinosaurs each happened upon slightly different ways to do this.

Herrerasaurus ischigualastensis [Image licensed under the Creative Commons Eva Kröcher, CC-BY-SA]

It's fascinating to see how many ways living things happen upon similar solutions to the problems of survival.  Evolution is both constrained and also infinitely creative; it's no wonder we are so often in awe when we look around us at the natural world.  The "endless forms most beautiful and most wonderful" Darwin spoke of in the moving final words of The Origin of Species never fail to astonish -- especially since the brains we use to comprehend them are just one of the end products of those very same processes.

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Jurassic rainbow

Regular readers of Skeptophilia might recall that about a year ago, paleontologists announced the discovery of a bird fossil from northeastern China that had a long, pennant-like tail -- and that from the extraordinary state of preservation, they were able to determine that the outer tail feathers had been gray, and the inner ones jet black.

Determining feather, hair, and skin color of prehistoric animals is remarkably tricky; the pigments in those structures break down rapidly when the animal's body decomposes, and the structures themselves are fragile and rarely fossilize.  The result is that when artists do reconstructions of what these animals may have looked like, they base those features on analogies to modern animals.  This is why in old books on dinosaurs, they were always pictured as having greenish or brownish scaly skin, like the lizards they were thought to resemble, even though dinosaurs are way more closely related to modern birds than they are to modern lizards.  (To be fair, even the paleontologists didn't know that until fairly recently, so the artists were doing their best with what was known at the time.)

But it does mean that if we were to get in the TARDIS and go back to the Mesozoic Era, we'd be in for a lot of surprises about what the wildlife looked like back then.  Take, for example, the late Jurassic Period fossil found by a farmer in China that contained the nearly-complete skeleton of a birdlike dinosaur.  Here's the fossil itself:

What's remarkable about this fossil is that the feathers were so well-preserved that paleontologists were able to get a close look at the melanocytes -- the pigment-containing cells -- and from the arrangement and layering of those cells, they determined that the dinosaur's head feathers were arrayed like a rainbow, similar to modern hummingbirds, sunbirds, and trogons.

So here's the current reconstruction of what this species looked like:

[Reconstruction by artist Velizar Simeonovski, of The Field Museum]

Kind of different from the drab-colored overgrown iguanas from Land of the Lost, isn't it?

The species, christened Caihong juji from the Mandarin words meaning "big rainbow crest," adds another ornate member to the late Jurassic and early Cretaceous fauna of what is now northern China.  And keep in mind that we only know about the ones that left behind good fossils -- probably less than one percent of the total species around at the time.  As wonderful as it is, our knowledge of the biodiversity of prehistory is analogous to a future zoologist trying to reconstruct our modern ecosystems from the remains of a sparrow, a cat, a raccoon, a deer, a grass snake, and a handful of leaves from random plants.

I think my comment about being "in for a lot of surprises" if we went back then is a significant understatement.

Even so, this is a pretty amazing achievement.  Astonishing that we can figure out what Caihong juji looked like from some impressions in a rock.  And it gives us a fresh look at a long-lost world -- but one that was undoubtedly as rainbow-hued and iridescent as our own.

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The climatic teeter-totter

Want a take on something familiar that will (probably) turn your mental image of it on its head?

Picture dinosaurs.  Not just the dinosaurs themselves, but where they are -- the terrain, plant life, and so on.  I'm guessing you probably came up with something like this:

[Image licensed under the Creative Commons ABelov2014 (https://abelov2014.deviantart.com/), Wessex Formation dinosaurs, CC BY-SA 3.0]

Lush, steamy, wet, sort of like today's Amazon rainforests.  It's no surprise Jurassic Park was set on a (fictional) island, Isla Nublar, off the coast of Costa Rica.

And we know for certain that part of the "Age of the Dinosaurs" had a lot of these characteristics.  The global climate from the mid-Jurassic to the end of the Cretaceous was largely warm and moist.  But a new study, published last week in Science Advances, suggests that the dinosaurs may have come to prominence not because of their adaptation to warm climates, but because of their resistance to cold ones.

Just about everyone knows about the KT (Cretaceous-Tertiary) Extinction, that wiped out all the non-avian dinosaurs, and is now attributed with near certainty to the impact of the Chicxulub Meteorite sixty-six million years ago.  Most people also have heard about the biggest mass extinction ever, the Permian-Triassic Extinction, that by some estimates wiped out between eighty and ninety percent of life on Earth, 252 million years ago.  Surprisingly few people have heard about the End-Triassic Extinction -- surprising because it caused nearly as much decrease in biodiversity as the Cretaceous-Tertiary Extinction would 135 million years later.

One of the reasons that this event doesn't get much attention is that the wipeout seems to have been gradual rather than sudden and dramatic, as both the Cretaceous-Tertiary and Permian-Triassic Extinction were.  "Gradual," of course, is in human terms; in geological or paleontological terms, it happened pretty damn quickly, over a period of about eight hundred thousand years or so.  The cause isn't as well understood as either of the other aforementioned extinction events, but seems to have been because of a climatic rollercoaster that first cooled the climate dramatically, and then warmed it up even more.  The cause is thought to have been the opening up of the Central Atlantic Magmatic Province, a line of enormous volcanoes that split what had been the supercontinent of Pangaea in half and opened up the Atlantic Ocean.  Eventually the province became the modern Mid-Atlantic Ridge (which is still driving North and South America away from Europe and Africa at a rate of about 2.5 centimeters a year).

The climate had already been cooling during the late Triassic, and sea levels fell as seawater got locked up into polar ice caps and glaciers.  The eruptions of the CAMP initially dropped the temperature even more, favoring cold-adapted animals and plants.  But just as we've seen from modern volcanic eruptions, the "volcanic cold snaps" we get from sunlight-blocking effects of the ash and debris being launched aloft eventually rebound into a warming event because of the pulse of carbon dioxide injected into the atmosphere.

That's what happened here, only on a huge scale.  The climatic teeter-totter tilted first toward significant cold and then into a warm, wet period, and the big winners in both scenarios were the dinosaurs.  We know about their ability to tolerate heat; like I said, mostly that's the kind of environment we picture them living in.  But their ability to weather a cold period seems to have been due to an adaptation their amphibian cousins didn't have: feathers.

We always tend to associate feathers with flight, for the very good reason that birds use them for that purpose.  But what we have here is a great example of preadaptation (sometimes shortened to preaptation), in which a trait evolved in one context gains another, unrelated, function and experiences a whole bunch of different selective pressures.  Feathers, which are modified reptilian scales (look at a snake scale under a microscope and you'll see the similarity), started out as heat-trapping devices; cold-adapted birds like penguins still use them that way.  Once small arboreal dinosaurs began to use feathered limbs as aids to gliding when they jumped from branch to branch, all of a sudden they became seriously well-adapted for something else, and opened the road to modern birds.

The more well-preserved dinosaur fossils we find, the more species we find that had feathers -- including the ones that didn't fly.  Even pterosaurs, which we usually picture as having leathery wings, were apparently covered with something very much like fur or fine down feathers.  (In fact, one of the small pterosaurs of the late Jurassic is called Sordes pilosus, which roughly translates as "hairy devil.")

So the initial temperature drop at the end of the Triassic Period favored dinosaurs with insulation -- then when the temperature rebounded into jungle conditions in the early Jurassic, the competition (in the form of large amphibian species) were mostly extinct, and the dinosaurs really took off, one branch of them using their feathery innovations for something entirely different.  

I always find it wryly funny when people think of dinosaurs as being some kind of "failed experiment" or "evolutionary dead end," when they were actually the dominant life form for 185 million years, which is almost six hundred times longer than modern humans have existed.  In fact, most studies have flatly contradicted the notion that "dinosaurs were already declining and then the meteorite impact finished them off" -- all indications are that they were doing just fine when Chicxulub hit.  Odd to think of it, but if it hadn't been for that catastrophic impact and horrifying extinction, our own ancestors would very likely never have thrived and spread -- and dinosaurs of some form might still be the dominant animal life on Earth.

But as far as the end-Triassic climate yo-yo goes, it just shows that when the external conditions change, what was a disadvantage can suddenly become an advantage, and what was an advantage can become a disadvantage -- or an advantage of another sort.  If things change fast, so can the winners and losers.

In this case, favoring a group that would go on to rule the planet for another 135 million years.

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A snapshot in amber

A few days ago I finished reading the wonderful new book by paleontologist Riley Black, The Last Days of the Dinosaurs: An Asteroid, Extinction, and the Beginning of Our World.  I can't say enough positive things about it -- it tells the gripping story of the impact of the seven-kilometer-wide Chicxulub Meteorite, which hit a spot just north of the Yucatán Peninsula so hard that most of the giant rock vaporized, what was left punched twenty kilometers into the Earth's crust, and it left an impact crater 180 kilometers across.

Artist's impression of the moment of impact [Image is in the Public Domain courtesy of artist Donald E. Davis and NASA/JPL]

Black gives us a vivid description of the event and its aftermath, each chapter from the point of view of one individual animal who experienced it (not necessarily lived through it, of course).  The day before the impact; the impact itself; the first hour; the first day; the first year; and so on, up until a hundred thousand years after the strike, at which point the Earth's ecosystems had largely recovered -- albeit with a completely different assemblage of species than it had before.

Black's contention, which is generally accepted by researchers, is that there's little truth to the old trope of the dinosaurs being a moribund group anyhow and the asteroid just finished them off.  The dinosaurs were doing just fine.  While some species were headed toward extinction, that had been happening during the group's 190 million year hegemony (and has happened in every single group of life forms ever evolved).  Dinosaurs as a group were still widespread and diverse -- and if it hadn't been for the impact, it's pretty likely that they would have remained in charge (as it were) for millions of years afterward.

Which means that it's probable that mammals would never have taken off the way they did.  (More accurately, "the way we did.")  It's also an incorrect understanding that mammals only launched after the dinosaurs were "out of the way."  Mammals had been around for a very long time themselves (the first ones, the morganucodontids and multituberculates, overlapped the dinosaurs by over a hundred million years).  What seems to be true, though, is that the dinosaurs occupied most of the large-apex-predator and giant-herbivore niches, so mammal groups were mostly small, and a lot of them were burrowers -- something that was an adaptation to there being a lot of carnivores around, but turned into a key to their survival during the searing infrared surge that swept across the world the day the asteroid hit.

What brings this up, besides my wanting to promote Riley Black's awesome book, is a link sent to me by a friend and loyal reader of Skeptophilia about a series of recent discoveries by paleontologist Robert DePalma at a dig site in Tanis, North Dakota.  What's stunning about these finds is that DePalma believes -- and the evidence seems strong -- that they represent the remains of organisms that died on the day of the Chicxulub Impact.

In other words, we're looking at a snapshot of the event that killed every non-avian dinosaur species, and changed the face of the world permanently.

Hard as it is to imagine, in the late Cretaceous, what is now North Dakota was a tropical wetland bordering the Western Interior Seaway -- an inlet of the ocean that has since vanished from a combination of uplift, the Rocky Mountain Orogeny, and simple evaporation.  Picture southern Louisiana, and you have an idea of what North Dakota looked like.

Then the meteorite struck.

Despite the fact that the distance between the impact site and the Tanis wetland is around four thousand kilometers, it only took an hour before there was a blast of heat, a rain of red-hot debris, and a series of earthquakes.  The first-mentioned is probably what did the most immediate damage; large animals that were too big to shelter were probably all dead within minutes after the the infrared surge started, as were just about all the terrestrial plants.  Even aquatic organisms weren't safe, though.  One of the more horrifying fossil finds was a turtle -- that had a stick driven all the way through its body.  The earthquakes triggered a series of seiche waves, which occur when an enclosed body of water is shaken laterally.  (Picture the sloshing of water in a metal tub if you jostle it back and forth.)  The seiche in the Western Interior Seaway and nearby lakes flung aquatic animals onto shore and then buried them under tons of debris -- DePalma and his team found layers of fish fossils right at the K-T Boundary Layer that were also victims of that awful day the impact occurred.

I've written about this event before, of course; I've always had a fascination with things that are big and powerful and can kill you.  But what made me decide to revisit it was a new discovery at Tanis of amber that contains glass spherules.  Amber, you probably know, is fossilized tree sap; it can contain other fossils, including pollen and animals that were trapped in the sap before it hardened (made famous by Jurassic Park, although it must be added that there's never been any found with intact DNA).  But these glass spherules were altogether different.  Silicate rocks turn to glass when they're melted and then cooled quickly; that's where the rock obsidian comes from.  But an analysis of the spherules showed something fascinating.  There were inclusions in the glass of tiny chips of two different kinds of rock; one type was high in calcium, while the other was largely metallic, with high content of chromium, nickel, and other heavy elements.

The first, DePalma says, are the remnants of the limestone bedrock from the spot in the Yucatán where Chicxulub hit, blasted into the air and landing four thousand kilometers away.

The other are the (thus far) only actual pieces of the meteorite itself which have ever been found.

It's absolutely astonishing that we can identify rocks and fossils that formed on a specific day 66 million years ago, and doubly so that it was a day when an event occurred that quite literally changed the course of life on Earth.  As horrifying as the Chicxulub Impact was -- Riley Black calls it "the worst day the Earth ever experienced," and it seems an apt description -- in a real sense, we owe our existence to it.

Without Chicxulub, it's pretty likely it'd still be a dinosaur-dominated world -- and one in which mammals were still small, furtive furballs that never had a chance to control their own destiny.

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