Drawn together

Convergent evolution occurs when only distantly-related species are under the same selective pressures, and evolve to look alike.  A particularly good example of this is the North American flying squirrel (a rodent) and the Australian sugar glider (a marsupial).  Put them side-by-side, and they're hard to tell apart, and both have the distinctive kite-like flap of skin between the forelegs and hind legs, allowing them to catch a breeze and glide from tree to tree.

It's important to emphasize that while convergent evolution can result in organisms being similar in appearance or habits, it doesn't ever cause them to fuse into a single species.  Flying squirrels and sugar gliders maintain major differences in their genetic make-up, skeleton, dentition, and so on -- so however close the resemblance, they're still two separate species.

Convergence is actually fairly common in the natural world, which is why appearance is such a poor guide to determining who is related to whom.  There are only so many solutions to the problems posed by living in a particular environment, so it's inevitable that different lineages will happen on the same ones.  Flying, for example, has evolved independently at least four times -- birds, bats, pterodactyloids, and insects.  The structure and mechanics is different in each, which is indicative that they were independent innovations.

I was thinking about convergent evolution this morning as I read a paper in the journal Geodiversitas about the discovery of a remarkable fossil in Colombia.  It's the best-preserved and most complete skeleton ever found of Anachlysictis gracilis, a Miocene apex predator that belonged to a group called the sparassodontids.  (The name comes from the Greek σπαράσσειν, to tear to pieces, and ὀδόντος, tooth -- an indicator of how scary these animals were.)

Here's a photograph of the skeleton:

[Image courtesy of Daniella Carvalho and Aldo Benites-Palomino]

My guess is that looking at this, you're immediately reminded of the saber-toothed cats such as the famous Smilodon, which also were around during the Miocene Epoch but reached their pinnacle a few million years later, during the Pleistocene.  Surprisingly, this parallels my earlier example of the flying squirrel and sugar glider -- the saber-toothed cats were true felids, and thus placental mammals, while Anachlysictus and the other sparassodonts were marsupials.  The two species were drawn together by the forces of convergent evolution.  If you're a predator, having big nasty pointy teeth is a pretty good adaptation regardless what taxonomic group you belong to.

These striking carnivores were present in South America during what is called the "splendid isolation," prior to the tectonic shift that formed the Isthmus of Panama and allowed for the Pliocene Great Biotic Interchange.  South America had developed a unique biota, including not only the sparassodonts but a variety of other marsupial groups, most of which are now extinct.  Even the South American placentals didn't do so well, and were outcompeted (or hunted to death) by North American migrants.  Not long after the formation of Central America, a great many of the South American groups -- not only the sparassodonts, but the glyptodonts, litopterns, astrapotheres, pyrotheres, and xenungulates -- were gone forever.

The new fossil discovery will allow paleontologists to make some deductions about not only its anatomy, but its behavior. "In a future study we will address all the other bones in its body, which include various sections of the spine, ribs, hip, scapulae -- what we call 'shoulder blades' for humans -- and bones in its legs," said Catalina Suarez, of the Argentine Institute of Nivology, Glaciology and Environmental Sciences, who led the research team.  "This will allow us to explore aspects of how it moved, the position in which its neck held its head, whether it was a runner, whether it could climb, whether its hands could hold objects more easily, as many marsupials do when feeding, or whether it was a bit more difficult, as it is for example for a dog or a cat."

It's fascinating to learn more about these long-extinct animals, whose ecological role would be taken over by predatory placental mammals like wolves and the various big cats.  Even if they're extinct, their bones still have a story to tell -- of a saber-toothed marsupial who hunted in the forests of Colombia thirteen million years ago.

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Walkabout

I'm always amazed at the depth of information paleontologists can glean from fossils.

And I'm not even including the ones that show exceptional preservation, like the ichthyosaur fossils I mentioned in a post a couple of days ago, that were so well preserved that they could even determine features like countershading.  Ordinary fossils contain a wealth of information about the organisms they came from -- if you know where to look, and how to interpret it.

Take, for example, the paper by a team from the University of Bristol and the University of Uppsala that appeared last week in the journal Alcheringa: An Australasian Journal of Paleontology.  Conducted by Christine Janis, Adrian O'Driscoll, and Benjamin Kear, the study analyzed the bones of prehistoric kangaroos, and reached a rather startling conclusion: a good many ancient kangaroo species didn't have the group's signature hop.

The determination came from looking at the strength and articulation of the leg bones, as well as the animal's overall size.  In particular, the short-faced kangaroos, or sthenurines, may have preferred to walk on all fours -- or might even have had a bipedal stride like a human.

The skeleton of Simosthenurus occidentalis, which I find vaguely terrifying. [Image licensed under the Creative Commons Ghedoghedo, Simosthenurus occidentalis, CC BY-SA 3.0]

You can see why they're called short-faced kangaroos in the artist's recreation of Procoptodon goliah below, in which I notice two things:

1. These creatures looked like a cross between a bunny rabbit and Godzilla.
2. The woman posing next to it has a stance like a Glamour magazine model, which is an odd thing to do if you're confronted with an eight-foot-tall kangaroo with giant claws.  Me, I'd be running like hell, if I didn't just wet my pants and then faint.

[Image licensed under the Creative Commons Nobu Tamura, Procoptodon goliah NT, CC BY-SA 4.0]

The striding kangaroos seem to have split off from the hopping kind about fifteen million years ago, during the Miocene Epoch, when Australia was a lot wetter than it currently is.  The climate back then would have favored large herbivores like the sthenurines (thank heaven these things weren't carnivorous), and they simply became too heavy to jump efficiently.  Even smaller sthenurines, though, had a different leg articulation -- they all appear to have been walkers rather than hoppers.

The last of the striding kangaroos went extinct during the last Ice Age, when the climate took a turn toward more arid conditions.  Aridity meant fewer plants, and slower growth for the ones that survived, and the largest marsupials in Australia died out.

Just as well.  Even the kangaroos that are left can kick you into the middle of next week; every year people, mostly stupid tourists, are injured by kangaroos.  Australians also have to contend with the various venomous snakes, spiders, and jellyfish, a relative of the nettle (the gympie-gympie) whose spines inject a neurotoxin that causes intense pain for years, and a highly-aggressive bird called the cassowary that looks like the bastard child of a turkey and a velociraptor.  The last thing those poor people need is giant kangaroo-bunnies striding around like they own the place.

Because the kangaroo-bunnies probably were vicious.  Down there, it's kind of an inevitability.

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Redefining the primitive

One of the most interesting, and persistent, misconceptions about evolutionary biology revolves around the use of the word "primitive" to describe certain life forms.

The misunderstanding goes back to Aristotle, really.  The great philosopher proposed a concept usually known by its Latin name of scala naturae, the "scale of nature."  Often called "the great chain of being."  The idea is that life has progressed up some sort of ladder of complexity, starting with something like bacteria, then upwards through jellyfish and worms and bugs and fish and amphibians and reptiles and "lower" mammals, finally arriving at us, who (of course) being the pinnacle of creation, stand proudly at the top of the ladder.

The problem with this, as with many misconceptions, is that in some ways it's kinda sorta almost true.  Something like today's bacteria were the first life forms, and the progression of fish > amphibian > reptile > mammal is pretty well established.  The problems start when you look at life forms earlier than fish; during the famous Cambrian Explosion, most of the phyla of animals branched off and diversified in a relative flash, not only including the ones we have around today but a number of oddball groups that didn't survive.  So with respect to most modern groups of species, that smooth progression up the ladder didn't actually happen.

The problem gets worse when you try to apply the word "primitive" to current life forms.  Is a bug more primitive than a human?  Both are alive right now; each of them has exactly the same length of ancestral history.  It doesn't even work if you link "primitiveness" with "complexity."  Humans and bugs are both complex organisms, they're just complex in different ways.  Certainly, there's a difference in intelligence; most humans are smarter than most bugs.  But intelligence doesn't equal evolutionary success.  By just about any measure, insects are by far the most successful animals on the Earth.

It recalls the famous anecdote about the illustrious biologist J. B. S. Haldane.  Haldane was a zoologist but also rather notorious as an outspoken atheist, and religious people used to go to his talks to heckle him about it.  At one, during the question-and-answer period, a woman asked, "Professor Haldane, what have your studies in biology told you about the nature of God?"

Haldane thought for a moment, and finally said, "All I can say, ma'am, is that he must have an inordinate fondness for beetles."

In any case, you have to be extraordinarily careful how you apply the word "primitive."  In biology it's now used to describe traits (not entire organisms), with a very specific, restricted meaning, defined as "a trait that is shared with the ancestral form."  An example is the vascular tissue -- the internal plumbing -- in plants, which is "advanced" as compared to the trait of "lacking vascular tissue."  Vascular plants evolved from non-vascular ones, so apropos of that trait, mosses (which lack vascular tissue) are primitive as compared to ferns (which have vascular tissue). 

But it still requires caution, because it's all too easy to assume that "primitive traits are less complex" or (worse) that "if an organism is like humans, that means it's advanced," neither of which are true.  For example, take a look at the paper last week in The American Naturalist written by a team from the University of Washington that questions the notion of primitiveness with respect to something most of us take for granted -- reproduction in mammals.

There are three basic modes of reproduction in Class Mammalia.  A couple of modern species are oviparous -- egg-laying (the monotremes, namely the echidna and the platypus).  Another group are marsupials, which give birth to extremely altricial (undeveloped) young, because the mothers have no placentas to interface between themselves and their babies.  Once the offspring are too big (which isn't very big at all; kangaroos are about two centimeters long at birth) they are born, and develop the rest of the way in the mother's pouch.  The third are the placentals such as ourselves (and every mammal you've ever heard of other than the monotremes and marsupials).

Egg-laying certainly is a primitive trait; it's pretty clear that the reptilian ancestors of the earliest mammals were oviparous.  But what about the presence of a placenta?  Once again, the danger is in assuming that it's the "advanced trait" because (1) humans are placentals, (2) there are currently more placentals than marsupials, and (3) somehow the placental method "seems more complicated."  These are all more like smug self-congratulation than they are science, and none are reliable indicators of the primitiveness of a trait.

The current study, in fact, suggests that the placental mode of reproduction may predate the marsupial method -- by a lot.  The researchers studied the odd multituberculates, a group of mammals that were amongst the first to diversify significantly, way back in the Jurassic Period around 170 million years ago.  They were some of the most common mammals for a very long time, finally going extinct about 35 million years ago (for reasons unknown). 

The multituberculate Sunnyodon notleyi [Image licensed under the Creative Commons FunkMonk (Michael B. H.), Sunnyodon, CC BY-SA 3.0]

The salient point here is that the marsupial mammals, including the extinct ones that have been studied, have a very distinctive pattern of bone growth that is connected to their being born so incredibly undeveloped.  A careful analysis of multituberculate bones shows they're a great deal more similar to today's placentals -- despite the fact that they branched off from the rest of Class Mammalia way earlier than the marsupials did.

So it looks like the little multituberculates had placentas and long gestation periods, and our mode of reproduction is actually the primitive one.  Meaning the marsupial lineage lost the ability to form a placenta, rather than our lineage gaining it.  Why that happened isn't known; but as we've seen, a trait doesn't need to be complex to give its owner a selective advantage.  Perhaps in marsupials, the draw on the mother's resources is lowered enough by giving birth early that it allows her a better shot at surviving -- but that's pure speculation.

Whatever it is, both modes function perfectly well.  "Evolution," as biologist Richard Dawkins put it, "is the law of 'whatever works.'"

And it all reinforces the notion that there is no "great chain of being," there's just an enormous tangled web of which we are just a single strand. 

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Danger down under

Following hard on the heels of Saturday's post, which started with a description of the cassowary -- Australia's killer bird -- today we follow up with a paper in Nature Communications just yesterday that falls under the "You think things are bad now?" department.

It's not like modern Australian wildlife is anything to trifle with.  The country is where you can find some of the world's most dangerous snakes, including the taipan, the brown snake, and the tiger snake.  The north coast is home to the enormous and aggressive saltwater crocodile, while the south coast has a sizable population of great white sharks.  The eastern coast, not to be outdone, is where you can run into the harmless-looking box jellyfish, which is in contention for winner of the most-potent venom contest; it injects its victim with a substance that has an LD-50 of 0.04 milligrams per kilogram of body weight, and can kill in under five minutes if an antidote isn't administered.  Even the plants bear watching.  The north coast has the beach spinifex grass, which reinforces the pointed tips of its leaves with silica drawn from the soil, essentially turning the plant into a cluster of tiny glass shards.  Worst of all is the gympie-gympie, which is like the humongous nettle from hell, inflicting an excruciating sting that can last for years.

(The Wikipedia article I linked says that the fruit of the gympie-gympie is "edible if the stinging hairs are removed first."  To which I respond, "Do I look like a fucking lunatic to you?"  I'll stick with fruit that's not attempting to murder me, thanks.)

But the paper "Extinction of Eastern Sahul Megafauna Coincides with Sustained Environmental Deterioration," by a team led by Scott Hocknull of the University of Melbourne, gives you a good feeling for how much worse it could be.  It describes a treasure-trove of fossils from Walker Creek in northeastern Australia that had the remains of hitherto-unknown species of fauna, including:

• a thus-far unclassified kangaroo that was four meters tall and weighed just shy of three hundred kilograms
• a new species of the genus Diprotodon, which was basically a wombat on steroids -- it's estimated to have been two meters tall at the shoulder and had a mass of 2,500 kilograms
• a new species of the horrific carnivorous marsupial Thylacoleo, which was slightly smaller than your average African lion, but is estimated to have had the most powerful bite of any known mammal, living or extinct
• a six-meter-long goanna and two never-before-seen species of monitor lizards
• a land-dwelling crocodile, because apparently the water-dwelling ones weren't bad enough

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

The kicker is that these things were around after the colonization of Australia by humans, and in fact, by some estimates there was a fifteen thousand year overlap where the ancestors of today's Native Australians had to contend with a nightmarish megafauna.  Me, I wonder why they stuck around, you know?  If I was one of them, and landed in my boat on the shores of Australia, and saw land crocodiles and six-meter-long lizards and a lion-sized Tasmanian devil, I would have used the words of the inimitable Eric Cartman: "Screw you guys, I'm goin' home."

Of course, home was Papua-New Guinea, which honestly wasn't all that much better.

It's an interesting question as to what finally did in these formidable critters.  Hocknull et al. write the following, in an article in The Conversation:

Why did these megafauna become extinct?  It has been argued that the extinctions were due to over-hunting by humans, and occurred shortly after people arrived in Australia. 

However, this theory is not supported by our finding that a diverse collection of these ancient giants still survived 40,000 years ago, after humans had spread around the continent. 

The extinctions of these tropical megafauna occurred sometime after our youngest fossil site formed, around 40,000 years ago.  The timeframe of their disappearance coincided with sustained regional changes in available water and vegetation, as well as increased fire frequency.  This combination of factors may have proven fatal to the giant land and aquatic species.

As magnificent as these creatures undoubtedly were, it's probably better that they're gone.  I've heard Australia is a pretty cool place, even considering its dangerous flora and fauna, but if the animals of Walker Creek were still around, it'd be hard to understand how anyone could manage to live there.  Just taking a short walk to the grocery store would be risking getting dismembered by enormous carnivorous marsupials.

Makes today's snakes and crocodiles and whatnot seem tame by comparison, doesn't it?

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This week's Skeptophilia book of the week is six years old, but more important today than it was when it was written; Richard Alley's The Two-Mile Time Machine: Ice Cores, Abrupt Climate Change, and Our Future.  Alley tackles the subject of proxy records -- indirect ways we can understand things we weren't around to see, such as the climate thousands of years ago.

The one he focuses on is the characteristics of glacial ice, deposited as snow one winter at a time, leaving behind layers much like the rings in tree trunks.  The chemistry of the ice gives us a clear picture of the global average temperature; the presence (or absence) of contaminants like pollen, windblown dust, volcanic ash, and so on tell us what else might have contributed to the climate at the time.  From that, we can develop a remarkably consistent picture of what the Earth was like, year by year, for the past ten thousand years.

What it tells us as well, though, is a little terrifying; that the climate is not immune to sudden changes.  In recent memory things have been relatively benevolent, at least on a planet-wide view, but that hasn't always been the case.  And the effect of our frantic burning of fossil fuels is leading us toward a climate precipice that there may be no way to turn back from.

The Two-Mile Time Machine should be mandatory reading for the people who are setting our climate policy -- but because that's probably a forlorn hope, it should be mandatory reading for voters.  Because the long-term habitability of the planet is what is at stake here, and we cannot afford to make a mistake.

As Richard Branson put it, "There is no Planet B."

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

Searching for a lost hope

As a biologist, I know that extinction is the way of the world.  Well above 99% of the species that have ever existed on Earth have gone extinct, and in fact (given the sparseness of the fossil record) chances are most of those we don't know about and will never know about.  Extinction is simply a fact of existence.

The soft-hearted side of me, though, finds it terribly sad.

As a dedicated birder, it's heartbreaking that I will never see a Great Auk, a Carolina Parakeet, a Passenger Pigeon, or a Dodo, all of which were driven to extinction in the past three hundred years by humans.  Even the pretty little Labrador Duck, which was already in decline before humans began overhunting them and destroying their habitat -- and so was probably doomed anyhow -- looks at me with its glass-bead eyes from the museum shelves with what I can only interpret as reproach.

"Extinction is forever" has gotten to be a cliché, but there's no denying its truth.  I'm not the only one who finds it tragic, which explains the ends people will go to in order to prove particular species live on.  My wife used to work for the Cornell University Laboratory of Ornithology as a sound archivist, and she was involved (in a tangential way, she'd tell you, but enough to merit a free t-shirt) with the efforts to relocate the Ivory-billed Woodpecker, widely thought to have been extinct since the mid-1940s.  The only evidence of its continued existence was a blurry ten-second bit of video that even the wishful thinkers couldn't swear was conclusive, but it was enough to mount an expedition to the swamps of Arkansas to look for it.  And several expert birders -- who are far too knowledgeable to mistake it for the related, but much smaller (and differently-patterned) Pileated Woodpecker -- swear they got good looks at what was known as "the Lord God bird" because that's what people would shout when what looked like a black, white, and red pterodactyl flew overhead.

So hope still exists, at least for some of the species currently considered extinct.  One of the most controversial -- the thylacine, also known as the Tasmanian tiger or Tasmanian wolf -- is currently the subject of a one-man relocation effort that hit the news just this week.

Australian Neil Waters is so invested in re-finding the thylacine that he purchased a huge tract of land in northern Tasmania, and plans on devoting the next two years to the search.  Waters claims to have seen thylacines himself twice before, and points out that there's not a lot you could mistake for them:

[Image is in the Public Domain]

Known for their amazing "scissor" gape, the thylacine -- which, despite its two common names, is neither a wolf nor a tiger, but a marsupial like the kangaroo and the koala -- were persecuted for an alleged affinity for eating sheep, and the last known individual died in a zoo in Hobart in 1936.  Since then there has been no hard evidence of its continued existence, although if you compare the sightings reports, the thylacine beats the Ivory-billed Woodpecker hands down.  The number of alleged sightings of thylacines number in the hundreds, with dozens more coming in every year.

[Image is in the Public Domain]

"[T]he hundreds of people who have reported sightings cannot all be wrong," Waters said.  "This is a long-term project and I am prepared to give it a couple of years – or until my finances run out.  My dream is to prove the thylacine is alive and well and have a management plan put in place to ensure their continued survival."

Another argument in favor of optimism is that it's not like seeing them was an everyday occurrence even when there was still a sizable number of them -- they were known for being shy and nocturnal.  So if there's a small population still out there, Waters reasons, it's no wonder they're seldom seen.

He adds that he's not interested in hand-waving, my-brother's-best-friend-saw-it-for-sure kind of arguments, but wants hard evidence that the experts will find unassailable.  "I have nothing to gain from faking anything," he said.  "I don't want to prove a fallacy."

The "nothing to gain" part isn't really all that accurate -- after all, he's already been featured in news media worldwide, and there are probably reality-TV shows that would love to do an episode or two on his hunt.  Not meaning to cast aspersions against him, because he certainly sounds sincere, and I really want to think that the second part -- that he doesn't want to fake evidence for a falsehood -- is the truth.

So for now I'm 100% in Waters's camp, and wish him the best of luck.  He certainly seems to be going about it the right way.  If they're still out there, there's hard evidence somewhere, and he's determined enough to have a real shot at finding it.

But part of it is wishful thinking on my part, because I really want the thylacine to still be alive.  They're cool, weird, and unique as the largest recent carnivorous marsupial.  Plus, finding it alive would mean one fewer irreversible assaults on the natural world to lay at humanity's feet -- and heaven knows, we have enough of those.

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This week's Skeptophilia book recommendation is pure fun, and a perfect holiday gift for anyone you know who (1) is a science buff, and (2) has a sense of humor.  What If?, by Randall Munroe (creator of the brilliant comic strip xkcd) gives scientifically-sound answers to some very interesting hypothetical questions.  What if everyone aimed a laser pointer simultaneously at the same spot on the Moon?  Could you make a jetpack using a bunch of downward-pointing machine guns?  What would happen if everyone on the Earth jumped simultaneously?

Munroe's answers make for fascinating, and often hilarious, reading.  His scientific acumen, which shines through in xkcd, is on full display here, as is his sharp-edged and absurd sense of humor.  It's great reading for anyone who has sat up at night wondering... "what if?"

[Note:  if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

Marsupial menagerie

One of the most biologically unique spots on Earth is Australia.

Besides the fairly familiar suite of marsupial mammals, there are a lot of curious life forms.  Australia's coastal waters are the home of one of the most venomous animals in the world, the innocuous-looking box jellyfish, which has an LD-50 (dosage that is lethal to 50% of the lab animals tested) of 40 millionths of a gram per kilogram of body weight, making it one of the most toxic naturally-occurring substances known.  On a happier note, in the western parts of the country there are lyrebirds, which not only have weird threadlike tail-feathers (giving them their name, as they look like the strings of a lyre), but are some of the most accomplished avian mimics -- able to imitate cellphones, chainsaws, camera shutters, and car alarms.

Even the plants are bizarre.  One you may not have heard of is the gympie-gympie (Dendrocnide moroides), common in the rain forests of the northeast, which is covered with hairs made of silica.  Yes, that's glass.  Each of the hairs is tipped with a rather horrifying toxin, making contact with the plant excruciating.  One guy who got smacked in the face by the plant still had searing pain when he'd take a cold shower two years later.

Oh, but the Wikipedia page says the fruits are edible "if the stinging hairs that cover it are removed."

Nope.  No thanks.  I can't imagine how hungry I'd have to be even to give that a try.

The main reason for the strange flora and fauna is that the island has been geologically separated from everywhere else since it separated from Antarctica a hundred million years ago -- a point in Earth's history during which the dinosaurs were still stomping around.  This is a hell of a long time for a community of organisms to evolve along their own pathways, so it's no great wonder that many of the creatures found there exist nowhere else on Earth.  (Australia is currently heading toward Asia, but the plate is moving at a barely-perceptible seven centimeters a year -- about the speed with which your fingernails grow.  Collision is expected in, oh, about a hundred million years or so -- at which point Australia's life forms will have to contend with an influx of new species from southeast Asia.  But so it goes.  At least they have a while to prepare.)

This all comes up because of two bizarre recent discoveries in the Australian fossil record, both of very large marsupial mammals that went extinct in the Pleistocene Epoch, on the order of 1.5 million years ago.  Australia doesn't have any marsupial mammals that are very large -- the current record holder is the red kangaroo, at 1.5 meters and eighty or so kilograms.  (Even some of the smaller ones, though, were pretty scary.  If you want something to haunt your nightmares, consider the flesh-eating kangaroo Ekaltadeta ima, which lived during the Miocene Epoch and weighed on the order of thirty kilograms.  The hopping jaws of death, those were.)

In any case, the two discoveries that were the subjects of papers released last week weren't so scary, but were just as strange.  First, we have fossils of a paleorchestid -- a bizarre, superficially tapir-like marsupial only distantly related to the familiar kangaroo and koala -- which topped out at a thousand kilograms.  If its size isn't striking enough, what the current paper looks at is its bizarre bone structure, which included forelimbs locked in place at about a hundred-degree bend at the elbow.  So they couldn't flex their arms -- giving them stability, and (the authors surmise) a better ability to lever out chunks of the plants that formed their diet, but severely limiting their ability to play tennis.

A reconstruction of a paleorchestid, whose expression suggests he's up to something [Image licensed under the Creative Commons Nobu Tamura, Palorchestes BW, CC BY 3.0]

The second discovery is of a giant kangaroo relative with a "crushing bite" -- not, apparently, for eating meat, but chewing up tough plants.  The species, Simosthenurus occidentalis, was one of a group called "short-faced kangaroos" which are all extinct now and some of which approached two meters tall.  

"Compared to the kangaroos of today, the extinct, short-faced kangaroos of ice age Australia would be a strange sight to behold," said Rex Mitchell of the University of Arkansas, leader of the team that analyzed the skulls, in an interview with Science Daily.  "The skull of the extinct kangaroo studied here differs from those of today's kangaroos in many of the ways a giant panda's skull differs from other bears. S o, it seems that the strange skull of this kangaroo was, in a functional sense, less like a modern-day kangaroo's and more like a giant panda's...  All this bone would have taken a lot of energy to produce and maintain, so it makes sense that such robust skulls wouldn't have evolved unless they really needed to bite hard into at least some more resistant foods that were important in their diets."

Sthenurus sterlingii, one of the short-faced kangaroos (not the one studied in the paper cited) [Image licensed under the Creative Commons Nobu Tamura (http://spinops.blogspot.com), Sthenurus stirlingi, CC BY 3.0]

So the odd life forms in Australia are the descendants and/or cousins of equally odd life forms that aren't around any more.  Which is probably a good thing.  The box jellyfish and the gympie-gympie plant are enough to worry about, along with the myriad other venomous snakes and spiders and whatnot.  If you added the Scary Nightmare Kangaroo of Doom to the mix, I'd just avoid the place altogether.

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This week's Skeptophilia book recommendation made the cut more because I'd like to see what others think of it than because it bowled me over: Jacques Vallée's Passport to Magonia.

Vallée is an interesting fellow, and certainly comes with credentials; he has an M.S. in astrophysics from the University of Lille and a Ph.D. in computer science from Northwestern University.  He's at various times been an astronomer, a computer scientist, and a venture capitalist, and apparently was quite successful at all three.  But if you know his name, it's probably because of his connection to something else -- UFOs.

Vallée became interested in UFOs early, when he was 16 and saw one in his home town of Pontoise, France.  After earning his degree in astrophysics, he veered off into the study of the paranormal, especially allegations of alien visitation, associating himself with some pretty reputable folks (J. Allen Hynek, for example) and some seriously questionable ones (like the fraudulent Israeli spoon-bender, Uri Geller).

Vallée didn't really get the proof he was looking for (of course, because if he had we'd probably all know about it), but his decades of research compiles literally hundreds -- perhaps thousands -- of alleged sightings and abductions.  And that's what Passport to Magonia is about.  To Vallée's credit, he doesn't try to explain them -- he doesn't have a favorite hypothesis he's trying to convince you of -- he simply says that there are two things that are significant: (1) the number of claims from otherwise reliable and sane folks is too high for there not to be something to it; and (2) the similarity between the claims, going all the way back to medieval claims of abductions by spirits and "elementals," is great enough to be significant.

I'm not saying I necessarily agree with him, but his book is lucid and fascinating, and the case studies he cites make for pretty interesting reading.  I'd be curious to see what other Skeptophiles think of his work.

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