Giant, shelled reptiles hold a special place in our hearts, whether you prefer something as highbrow as the classical myth of the World Turtle or the wanton, city-stomping destruction of Gamera. Turtles and tortoises already have an ancient look to them, even when they’ve just hatched, and so the giant ones seem like the must be even more ancient and wise, as if they carry secrets from the days when the Earth was young.
In 1844, the French paleontologist Auguste Bravard described the shell of one such chelonian found in the Oligocene-age rock of southern France. Very little was known about even living tortoises at the time, so it made sense to attribute the two-and-a-half-foot-long shell to the same genus that encompassed many modern species, Testudo. And from there, the shell was almost entirely forgotten.
But now paleontologist Adán Pérez-García has gone back to that old shell and found it not only represents the largest tortoise of its time, but belonged to a distinct genus. From the shell excavated so long ago, Pérez-García has named the tortoise Taraschelon in reference to a shelled creature in French lore known as Tarasque. That’s the nice thing about turtles and tortoises – there are so many stories and legends about them that when you find a previously-unseen species, there’s always the opportunity to make something old new again. Now if we could only get one named for the Great A’Tuin.
Name: Taraschelon gigas
Meaning: Taras is short for Tarasque, a legendary creature with a turtle-like shell, while chelon means turtle or tortoise and gigas means “giant.”
Age: Around 30 million years old.
Where in the world?: Southern France.
What sort of critter?: A tortoise.
Size: The shell measures about two and a half feet long.
How much of the creature’s body is known?: A nearly-complete shell.
Do a Google Image search for the word “Triassic” and you’re going to see variations of the same scene over and over again. Svelte little dinosaurs snap and squawk around an ancient lake or river, with the also-rans of their era – such as the armored aetosaurs and superficially-crocodile-like phytosaurs – shuffling through the undergrowth and basking at the water’s edge. Such vignettes are classic Triassic imagery, and yet they’re only a narrow view of one part of the opening chapter in the Age of Reptiles triology. There’s far more to the Triassic story than Coelophysis and its neighbors, with the latest wrinkle to the tale arriving in the form of a beautiful skull found in Brazil.
The fossil, described by paleontologist Felipe Pinheiro and colleagues, was that of an archosauromorph. This was a line of reptiles that first evolved back in the Permian, when the protomammals held sway, and underwent explosive diversification during the Triassic, eventually sprouting branches that would include dinosaurs, pterosaurs, and crocodiles.
Named Teyujagua paradoxa by the researchers, the 251 million year old animal lived just before the great reptilian radiation really took off. So while not necessarily the ancestor of the various lineages that would come later, Pinheiro and coauthors point out that the skull of Teyujagua is a significant part of the story given that it exhibits some characteristics of older forms of reptiles as well as novelties that would come to mark the “ruling reptiles” such as serrated teeth and an opening in the sidewall of the lower jaw. When you look at the skull of Teyujagua, you’re looking at a face that helped set evolutionary trends from the dawn of the Triassic until today.
Meaning: The genus was named after Teyú Yaguá, a dog-headed lizard in Guarani mythology, while paradoxa underscored the “unusual” combination of characteristics.
Age: Around 251 million years ago.
Where in the world?: Southern Brazil.
What sort of critter?: An archosauromorph, or an ancient member of the lineage that includes dinosaurs, pterosaurs, crocodiles, and their relatives.
Size: The skull is about four and a half inches long.
How much of the creature’s body is known?: A nearly-complete skull and several neck vertebrae.
[Note: In a previous version of this post I wrote that the amber specimens were donated to the American Museum of Natural History. That was a mistake. These lizards, like many other important amber-bound fossils, are still held in a private collection and could be sold off tomorrow if the owner so chose.
The wording concerning where the fossils are reposited – or in this case, not – confused me, and I feel especially frustrated by this because I didn’t want to highlight fossils kept out of the public trust. Paleontology, like all science, relies on reproducibility, and that can only happen if significant fossils are held at accredited institutions in perpetuity. That’s the standard, and it’s past time for scientific journals to step up their requirements to match the ethics of the field.]
If you want to follow Earth’s constant and exuberant evolutionary dance, you’ve got to get in touch with the fossil beat. The stacked remains of creatures long extinct provide the essential backstory for every species alive today, marking who emerged onto the stage when and how drastically, or not, their routine has changed through the ages. A single discovery can quickly change the program, however, as a tiny lizard just did for chameleons.
The small squamate, encased in amber, was not a new find from a scientific expedition. The lizard was one of many sold in the private fossil trade out of the amber-rich deposits of Myanmar, winding up in the private collection of James Zigras now made available through cooperation with the American Museum of Natural History. It was one of eight cut-and-polished pieces containing lizards so spectacular that their little scales can be seen, now shown off in high-resolution CT scan detail in a paper by herpetologist Juan Daza and colleagues. Out of this handful of fossils, though, it’s the chameleon that has made headlines.
At less than an inch long, the 99 million-year-old lizard looks like a little scribble in the rock. But thanks to high-tech imaging, Daza and coauthors were able to identify the reptile as a very close relative of chameleons. It didn’t belong to the strictly-defined group that contains modern chameleons, in other words, but is the closest known relative to the group or what paleontologists call a stem chameleon. This must have come as something of a shock. Up until now, the oldest fossil chameleon came from Miocene deposits much closer to us in time. This new lizard stretches the lineage of these charismatic lizards back about 78 million years earlier, meaning that there are a hell of a lot of fossil chameleons waiting to be found in the new gap.
Name: There isn’t an official name yet, but the specimen is known as JCZ Bu 154.
Age: About 99 million years old.
Where in the world?: Myanmar.
What sort of critter?: The closest known relative of all chameleons.
Size: Less than an inch long.
How much of the creature’s body is known?: A single, nearly-complete body encased in amber.
It’s difficult to resist calling pliosaurs sea monsters. Their long, toothy jaws and strange, streamlined shapes make them dead ringers for what we fear waiting for us in the deep and, for my own part, I’m a little less hesitant to plunge into the ocean knowing that the last of them went extinct over 66 million years ago.
Many pliosaurs are cast in the same role – as big apex predators capable of munching on prey as large, if not larger than, themselves. But not all pliosaurs accomplished these gustatory feats in the same fashion. A new fossil pliosaur described by paleontologist Valentin Fischer and colleagues late last year hints that one carnivore, at least, was accomplishing the same task in a slightly different way.
There was only just enough of the animal, named Makhaira, for Fischer and coauthors to identify it as something new. The reptile’s preservation in 130 million-year-old limestone nodules was not kind to its bones. But the teeth and jaws from the tip of the predator’s snout make it stand out from its relatives. Each tooth of Makhaira had three serrated cutting edges, and the teeth were not as closely-spaced as those of other big-game-hunting pliosaurs. The overall picture is that Makhaira slammed this distinctive dental armory into big prey even though it wasn’t as massive as some of its larger relatives, indicating that pliosaurs were still capable of big bites even at smaller size.
Meaning:Makhaira is a Latinized version of the Greek word for “curved blade” and rossica denotes the animal’s discovery in Russia.
Age: Around 130 million years ago.
Where in the world?: Slantsevy Rudnik, western Russia.
What sort of critter?: A marine reptile known as a pliosaur.
Size: Estimated around 15 feet long.
How much of the creature’s body is known?: A fragmentary skeleton including parts of the jaws, teeth, several vertebrae, and pieces of the hips.
One of the stumbling blocks in writing about prehistory is the lack of familiar names for many of the strange creatures that came before us. Or, at least, there’s a lack of patience in sounding out anything that’s not a dinosaur. To totally bastardize a quote from Mayor Vaughn in JAWS, “You yell ‘pseudosuchian’, everybody says ‘Huh? What?’ You yell ‘dinosaur’, we’ve got schoolchildren swarming the exhibit hall.”
But not every obscure group suffers from getting lost in translation. One family of ancient oddities has gained a title that playfully sums up what they were by mashing up two more familiar critters. I’m talking about the armadillodiles.
Paleontologists know these reptiles as aetosaurs. They were herbivores and omnivores that thrived during the Triassic, between 252 and 200 million years ago, and while they share an ancient kinship with crocodiles they looked and possibly behaved something like armadillos. Hence the popular name. These bizarre animals are also favorites among Triassic experts. Case in point, Petrified Forest National Park paleontologist Bill Parker has just published a major revision of aetosaur relationships in which he describes a brand new armadillodile that was masquerading as a different species.
While it’d be wonderful if every vertebrate fossil were a complete and easily-identifiable skeleton, the fact of the matter is that paleontologists are often working with bits and pieces. Sometimes those parts get referred to already-existing species as a working hypothesis, as happened with Triassic bones found in Arizona that experts suspected belonged to an aetosaur named Calyptosuchus wellesi which had been found in other spots through the southwest. When Parker took another look at these bones, however, he found that the fossils from Arizona had a raised triangular knob on the scutes running along the animal’s side that are not present in the holotype – or name-bearing specimen – of Calyptosuchus. The different ornamentation meant that the material from Arizona, as well as some pieces from Texas with identical decorations, must belong to something new. Parker named this new armadillodile Scutarx deltatylus, the latest creature to shuffle into the Triassic spotlight.
Meaning:Scutarx means “shield fortress”, while deltatylus translates to “triangular protuberance.”
Age: Around 230 million years ago.
Where in the world?: The Late Triassic rock of Arizona and Texas.
What sort of critter?: An aetosaur, or a heavily-armored and more herbivorous cousin of crocodiles.
Size: Cited as a “medium-sized aetosaurian.”
How much of the creature’s body is known?: A partial skull, osteoderms, and several postcranial skeletons.
Alligators are pretty tough. I’m not just referring to the fact that they faced down extinction in the 20th century and thrived. They’re also physically hardened, a set of ridged bones beneath their skin called osteoderms giving them a built-in coat of armor. But those skin bones aren’t just for protection. They’re also a handy source of calcium for egg-laying female gators.
Alligators, like all their other crocodylian relatives, lay eggs. In any given season a female alligator can lay up to 40 eggs in a clutch adding up to a total of 90 to 200 grams of calcium. That puts a pretty big demand on mother alligators to come up with enough material to create all the shelly capsules for their embryos. In a new paper, University of Portsmouth biologist Chris Dacke and colleagues considered the options.
Frogs and some lizards can ossify their skeletons thanks to the calcium-rich contents of a special sac next to the skull. Perhaps pregnant alligators drew on a similar pathway for their eggs. Yet when Dacke and coauthors looked at these sacs in female alligators before and after laying eggs, they didn’t spot any significant differences. And given that alligators can’t lay down and then utilize an ephemeral tissue called medullary bone like birds and non-avian dinosaurs, the calcium has to come from somewhere else. X-rays and tissue samples suggest that the answer is in the armor.
The osteoderms of nesting females used in the study weren’t as dense as in other alligators. They were lighter, and the degree to which the bone had been “mobilized” led Dacke and coauthors to estimate that a nesting mother alligator may use at least 10% of the calcium in her own armor to form her eggs. How this happens isn’t yet known. But should you ever see a nesting alligator (hopefully at a respectful distance!), have a look at the bumps on her back. Some of that armor was sacrificed to cradle the next generation.
Paleontology is still pretty new as sciences go. It’s only been around in any kind of organized form for less than 200 years, and while today’s explorers and researchers can trace their pedigrees through multiple generations, paleo practitioners have really only just begun to literally scratch the surface of what’s out there. This is true even on continents that have been considered well-sampled and studied. Case in point, the Lo Hueco fossil site in central Spain.
The Late Cretaceous boneyard, located in the village of Fuentes, was only discovered in 2007. Since that time paleontologists have found fish, amphibians, turtles, lizards, crocodiles, and various dinosaurs from this one spot, and they’ve just named a new species from the assemblage. Described by Iván Narváez, Christopher Brochu, and colleagues, the large-toothed crocodile has been dubbed Lohuecosuchus megadontos.
Back when Lohuecosuchus was alive, around 72 million years ago, much of Europe was an archipelago. Tongues of ocean separated islands where dinosaurs roamed, and the separation of once-connected landmasses led new species to evolve among the scattered islands. Lohuecosuchus megadontos was one of these evolutionary spinoffs, and even had a close – but distinct – relative in Cretaceous France named Lohuecosuchus mechinorum by Narváez and coauthors. Along with the other European crocs of the time, these two new species show what evolution can do with a little isolation.
Meaning:Lohuecosuchus means “crocodile from Lo Hueco”, while megadontos is a reference to the reptile’s large teeth.
Age: Around 72 million years old.
Where in the world?: Lo Hueco, central Spain.
What sort of critter?: An ancient crocodile belonging to a group called allodaposuchids.
Size: The skull measures about 15 inches long and 11 inches wide.
How much of the creature’s body is known?: Three skulls – ranging from complete to fragmentary – and three lower jaws.
Crocodiles look ancient. Maybe it’s something to do with the eyes, the armor, and the teeth that remind us of the Age of Reptiles. Or maybe it’s simply because crocs are often used as window dressing to set Mesozoic scenes that gives us the impression that they’ve always been watching from just beneath the surface of the water. Whatever the reason for these alligator impressions, though, paleontology has undeniably shown that these archosaurs are far from the “living fossils” we love to portray them as.
Paleontologist Julia Molnar and her coauthors set the record straight in the very first line of their latest paper. “The lineage leading to modern Crocodylia has undergone dramatic evolutionary changes in morphology, ecology, and locomotion over the past 200+ Myr.” While it’s true that crocs in the flavor of “semi-aquatic ambush predator” of one lineage or another have been around since the Jurassic, focusing on these amphibious carnivores blinds us to the wider variety of crocodylomorphs that have come and gone over the past 245 million years. There were terrestrial pipsqueaks that ran on their tippy-toes, crocs that spent almost their entire lives at sea, and, of course, the 40-foot monsters that snatched dinosaurs from the water’s edge, among others. And as Molnar and colleagues demonstrate, one way to see this diversity is in the spine.
Today’s alligators, crocodiles, and gharials get around in a surprising variety of ways. They’re accomplished swimmers, they can drag their bellies along the ground or push up into a “high walk”, and little crocodiles can even gallop. But are these recent specializations, or are some of their capabilities ancient holdovers from the long, long history of their greater family? To investigate this question Molnar and colleagues created virtual models of five extinct crocs to see how their trunk flexibility matched up with their mode of life, checked against a model of a Nile crocodile spine verified by trunk-bending experiments on a carcass from the living species.
The spread of crocs in the new study bridged land and water. Two of the earliest, Terrestrisuchus and Protosuchus, were little terrestrial predators, while Pelagosuchus, Steneosaurus, and Metriorhychus document the change from semi-aquatic crocs to ones that propelled themselves around the seas with paddle-shaped limbs and fluke-tipped tails. From these reconstructed lifestyles Molnar and colleagues predicted that the land-dwelling crocs that moved more like mammals would have had spines that were more flexible up-and-down than from side-to-side and that the marine species would show increasing stiffness of the trunk to cope with moving through the water at speed, but their results yielded some surprises.
Millions and millions of years before the first whales took the plunge, the thalattosuchian crocs transitioned from nearshore life to one out in the open ocean. And, much like the whales, the prehistoric crocodiles went through a similar process of increasing flexibility in the spine in amphibious forms followed by greater trunk stiffness among the species that were full-time swimmers. Compared to Pelagosaurus, Molnar and coauthors found, the increasingly aquatic Steneosaurus and Metriorhychus had spines that were stiffer from side-to-side as their tails took one more of the propulsive work. These crocs swam in a variation of what dolphins do today, keeping the body rigid to plow through the water while all that power comes from swishes of the tail.
Based on the similar biomechanical lines of logic, Molnar and coauthors predicted that the early, land-dwelling crocs Terrestrisuchus and Protosuchus would have trouble bending side-to-side but would be flexible in the up-and-down plane. This would fit with the way they moved, with vertical movements of the spine as they pumped their legs forward-and-back beneath their bodies. But this isn’t what the researchers found. Terrestrisuchus, which would have more of a mammal-like walk than any of its relatives in the study, had a spine that was more flexible from side-to-side than in the vertical plane, and, in fact, would have been even stiffer along that axis because of a set of osteoderms – bony armor – that ran down the vertebral column. Trackways have confirmed that crocs like Terrestrisuchus really did walk with more upright limbs, but, Molnar and colleagues point out, the way the spine and legs worked together must have been different than we see in mammals.
Paleontologists have found plenty of other prehistoric crocs that could be thrown into the mix. But even from these five, it’s clear that crocs have not been in stasis since they first trotted out onto the evolutionary scene in the Triassic. The species we see around us today are really just a sliver of what once existed, and are specialized creatures in their own right rather than being stagnant holdovers from the depths of the Mesozoic. And given how much they’ve changed since their origin, I can’t help but wonder what might happen in the future. Should today’s crocodylians survive us, might any of them reprise the roles their predecessors took on land and in the seas?
Molnar, J., Pierce, S., Bhullar, B., Turner, A., Hutchinson, J. 2015. Morphological and functional changes in the vertebral column with increasing aquatic adaptation in crocodylomorphs. Royal Society Open Science. doi: 10.1098/rsos.150439
Shortly after I moved to the beehive state and started doing fieldwork with the Natural History Museum of Utah, I started hearing snippets of a new turtle found in the vast desert of Grand Staircase-Escalante National Monument. The 76 million year old reptile, being studied by graduate student Josh Lively (now at the University of Texas at Austin), was unlike any other turtle ever found. You can see it right in the snout.
In addition to features like a shell, every other turtle ever known has a single bony opening for the nose. The two separate nostrils you can see on the outside are soft tissues. But this new fossil turtle, named Arvinachelys by Lively and colleagues, is different. This turtle has two bony openings in the snout, giving it a pig-like appearance. So before the turtle had an official name, when we’d be in the same camp searching for more fossils, I’d often hear Lively affectionately refer to the subject of his research as “Miss Piggy.”
There’s more to Arvinachelys than its peculiar nose, though. The turtle lived in the same environment as unique dinosaurs such as the horned Nasutoceratops, the tyrannosaur Teratophoneus, and the crested hadrosaur Parasaurolophus. Most of these dinosaurs were different genera or species from those found elsewhere at the same time, suggesting that southern Utah was a hotspot for animal diversity. But why? Some researchers have suggested a physical barrier – like a river system or mountain range – that kept animals from dispersing. Others have proposed that dinosaurs and other organisms were sensitive to environmental changes around them and were closely tied to limited swaths of habitat. Perhaps, with the context of other finds elsewhere around North America, Arvinachelys and its dinosaur neighbors will eventually give up the secret of what made prehistoric Utah so weird.
Where in the world?: The Goio-Erê Formation of Brazil.
What sort of critter?: An acrodontan lizard related to today’s agamas.
Size: Not estimated.
How much of the creature’s body is known?: A lower jaw as well as possible parts of the upper jaw and teeth.
Claim to fame: “Nothing in biology makes sense except in the light of evolution”, the biologist Theodosius Dobzhansky famously wrote, and – to bastardize that oft-repeated quote for this post’s sake – nothing in biogeography makes sense except in the light of the fossil record.
The distribution of different groups of organisms over the planet is rife with puzzles and contradictions. One of these longstanding head-scratchers concerns the major group of lizards called iguanians. There’s a major split among these reptiles. Forms with teeth fused at the top of their jaws – called acrodonts – are scattered throughout the Old World, but their closest relatives dominate the Americas, Madagascar, and a smattering of Pacific Islands. If lizards such anoles and agamas are close relatives, in other words, why are they so far away from each other?
Gueragama sulamericana, a fossil lizard described by Tiago Simões and colleagues, has begun to offer an answer. This 80 million year old lizard scurried through the deserts of prehistoric Brazil, yet it belonged to the acrodont lineage found only in the Old World today. It’s the first of its kind found in the Americas, and, Simões and coauthors write, the critter brings up a new scenario for the spread of iguanian lizards seen today.
Tens of millions of years before Gueragama, while the continents were still knit together to make the supercontinent Pangaea, the acrodont and non-acrodont lizards diverged from their common ancestor. The tall-toothed ones – the ancestors of Gueragama – spread all over the world. But, as the continents became isolated, the acrodonts began to be replaced by their close relatives in the Americas. Why this happened is a mystery. The mass extinction at the end of the Cretaceous could have wiped out the kin of Gueragama, Simões and coauthors speculate, or maybe the non-acrodonts out-competed their relatives. Now that paleontologists know that Old World lizards once had a toe hold in the New, though, fossil hunters will know to keep an eye out for the reptiles in places they were never expected to be.
Today, Phenomena gets a little spookier as we welcome Erika Engelhaupt to the salon. The name of her blog says it all: In Gory Details, she’ll be bringing you tales from the darker side of science — creepy thrills, macabre reality checks, and stuff for which the term “morbid fascination” aptly applies.
Maybe it has something to do with all the time she spent tromping around in swamps while studying environmental science, earning a couple of master’s degrees and – in her words – publishing “boring science papers.” After that, Erika ditched the science papers and began writing for newspapers, triggering a metamorphosis from scientist to science journalist. Now, in addition to being our newest Pheno-type, Erika is also the online science editor for National Geographic, and will help manage the Phenomena blog network.
I’ve known Erika for a while now (she was one of my editors at Science News), and she’s always seemed so…normal? To celebrate the launch of Gory Details, I asked Erika some questions about where she’s headed.
So what’s this obsession with gory stuff?
I suspect I may have read too many Stephen King novels at a young age. My mom and I would tear them in half down the spine so we could each read half at the same time. I’ve always enjoyed reading about creepy stuff (but no scary movies—I prefer my imagined horrors over Hollywood’s versions). Combine that with a love of science, and I guess you get Gory Details.
How did Gory Details come about?
I was an editor at Science News, and one day I was sitting in my office and looked at a shelf filled with books I had reviewed for the magazine. There were titles like Blood Work, The Killer of Little Shepherds (a fantastic forensic history), and That’s Disgusting. It had never really dawned on me until that point that maybe I had a morbid fascination. Suddenly it just popped into my head—I should write a column on the dark side of science and call it Gory Details.
At the time the magazine was soliciting ideas for news columns, but mine was initially considered too gross for a column. So I had to bide my time for two years until we were launching new blogs, and I got my chance. And it turned out that other people shared my curiosity.
What do you want this blog to be about?
So many things! First, I want to really delve into forensic science, because there’s so much going on right now. We’re at this strange point where there are really amazing high-tech methods being developed to analyze crime, but mostly what police have to work with is very old-school, and actually a lot of basic forensic analyses, like hair analysis, are being questioned — is this stuff even really science?
I’m fascinated by all manner of dead things, too. That includes archaeology, and pretty much anything involving old bones. I’m a sucker for a Neanderthal story, because I love to think about how close we are to our beetle-browed cousins.
Then there is, of course, the gross beat. I ended up writing a lot of stories about pee and poop in the blog previously, and every now and then I would announce a hiatus on bodily functions stories. But then someone would come along with some fascinating thing about fecal transplants or something, and I’d be off to the races with that.
I’d also like to branch out into some other areas that people might not immediately think of as gory, but that fall into the “huh, weird” category. So robots and artificial intelligence, perception (which, trust me, is full of really strange stuff), and the dark side of human nature. And I’m an environmental scientist by training, so I’m going to claim that environmental nasties are something we need to examine in gory detail too.
So…sort of the “eww” beat?
I’m happy to claim the “Eww” beat! When Maryn McKenna joined Phenomena recently with her scare-tastic blog Germination, someone on Twitter pointed out that she was claiming the “oops” beat (since she often covers how we humans have messed up the good thing we had going with antibiotics). And they noted that Ed’s on the “Wow” beat, and Nadia, I think we decided you were the “Boom” beat, right? Or maybe “Oooh”? And if Brian’s “Rock” and Carl’s “Life,” I guess that leaves me with “Eww”!
What are some of the spookier stories you’ve uncovered so far?
Some of my favorites have been ones that pose a “scary thought” kind of question. I really delved into what would happen if a nuclear bomb went off in Washington, D.C., where I live and where sometimes the threat of an attack feels quite real. I wrote about my own odds of survival less than a mile from the White House (not terrible, actually) and how to do the math on whether to seek better shelter or stay put.
I also love finding really weird stuff in out-of-the-way corners of science. I had great fun with the story of a researcher who set up a re-enactment of da Vinci’s painting of the Mona Lisa using toy figures and posited that the original and a studio copy may have been made as the world’s first experiment in 3-D imaging. No one knew about this guy’s work, and after I broke the story it went nuts.
I imagine you’ve got a pretty thick skin since you’re used to diving into the world of weird. Is there anything that’s too creepy, scary or gross for you to deal with?
You know, it’s funny—there’s a psychology test for how easily disgusted a person is, and I tested out dead average. I’m not especially hard to gross out. Maybe that’s part of the fun; that I have a very normal response to this stuff.
But to answer your question, I have tried to be careful about writing about gory medical conditions, because I don’t want to come across as making light of people’s very real problems. And as for what I’m personally freaked out by, it’s gotta be crocodiles. They populate my nightmares.
It started when Jolanta Watson put a frozen box-patterned gecko on a glass slide. The lizard’s skin is adorned with beautiful auburn and tan blotches, and Watson wanted to study it under a microscope. But as she reached for a scalpel, she noticed that tiny water droplets had formed on the slide. The longer she looked, the more droplets there were. Where were they coming from?
The microscope revealed the answer. Through its lens, Watson saw that droplets would condense on the gecko’s skin, roll into each other, and jump off under their own power. That’s why the slide was wet. The box-patterned gecko’s skin can actively repel water even if it’s dead and immobile. And when it’s alive, it can use this phenomenon, which Watson calls “geckovescence”, to clean itself with no effort.
High-speed footage slowed down 13x shows dewdrops being propelled off a gecko’s skin, a phenomenon that may help keep bacteria and fungi at bay. Credit: Dr. Gregory Watson
There are some 1,500 species of geckos, which are best known for their sticky feet. Their toes are covered in thousands of microscopic hairs that allow them to cling to seemingly flat surfaces—including the walls of Watson’s Australian home. As she and her husband Gregory watched these lizards, they realised that scientists had largely ignored the rest of the gecko’s body. Their toes were cool, but what about the rest of their skin? In particular, how does it deal with water?
The box-patterned gecko lives in the Australian desert, where rainfall is rare and water is scarce. Still, chilly nights and humid mornings can produce a lot of dew, some of which condenses on the gecko’s skin. That’s a problem: water-logged skin is a breeding ground for microbes and fungi, which could potentially cause diseases.
Fortunately, as the Watsons found, the gecko can automatically dry itself. When they looked at the lizard’s skin under the microscope, they saw that its scales are like rounded domes. Each of these is covered in miniscule hairs, just a few millionths of a metre long, about the size of a small bacterium. They’re densely packed too: thousands of them would fit in the cross-section of a single human hair.
Many natural structures, including springtails, leafhoppers, lotus leaves, and guillemot eggs, use similar microscopic textures to waterproof themselves. The principles are always the same: there are raised sections, like the gecko’s hairs, that trap pockets of air and stop water from seeping into the spaces between them. When droplets form, they sit on top of the raised bits as nigh-perfect spheres, rather than flattening out as they would do on a tabletop or on your skin.
The Watsons saw exactly this when they cooled gecko skin to the point when dew started to condense. Spherical droplets appeared, and grew. When they touched each other, they merged. And when they merged, they would occasionally fly off. Why? Because when two droplets unite, their volume stays the same but their combined surface area—and thus, their surface energy—goes down. They convert some of that surface energy into kinetic energy, and if the trade-off is substantial enough, they can launch themselves into the air.
All of this happens without help from any external forces, but external forces can help. In fog, water droplets in the air collide with those on the gecko’s skin, increasing the odds that they will jump off. Here’s a series of images showing one such jump. Wind helps too; it blows droplets into each other, and carries the airborne drops away from the lizard.
All of this makes for effortless auto-cleaning skin. As the droplets form and merge, they carry dirt, spores, and other foreign material with them. When they leap away, they remove those contaminants from the gecko. Other animals probably use a similar trick, including a type of cicada that the Watsons studied a few years ago.
“There are a number of potential practical applications,” says Watson. “Keeping surfaces clean and free from dew or other small droplets may reduce the growth of bacteria and fungi. We are currently investigating a number of properties on replicated gecko skin architecture.”
Reference: Watson, Schwarzkopf, Cribb, Myhra, Gellender & Watson. 2015. Removal mechanisms of dew via
The “Age of Reptiles” was supposed to have ended long ago. The 170 million year reign of dinosaurs, pterosaurs, plesiosaurs, and their ilk was brought to an close 66 million years ago by an unfortunate combination of earthly and extraterrestrial causes, opening the way for beasts to take over.
But it’s not as if reptiles entirely disappeared or were relegated to being bit players in the new “Age of Mammals”. Scaly survivors thrived in the new world, spinning off strange and superlative species. Titanoboa, for example, earned its title as “Largest Snake of All Time” about 60 million years ago – a reminder that Cenozoic reptiles need not be looked at with a pitying eye. The 13 million year old rock of Peru has now offered another such reminder. There, paleontologists have found a super-rich collection of crocodylians more diverse than anything seen today.
Called the Iquitos bonebeds, and studied by Universidad Nacional Mayor de San Marco paleontologist Rodolfo Salas-Gismondi and colleagues, the two sites have yielded seven different species of prehistoric crocodylians. The crocs range from stout-snouted monsters to long-jawed fish snatchers and blunt-toothed caimans, and five of the species drawn from the bonebeds have never been seen before. The question facing the paleontologists is why so many different species were present in the same place at the same time.
An abundance of hard-shelled prey might hold part of the answer. There were at least 85 species of clams in the same habitats, not to mention other hard-shelled invertebrates like ostracods, and at least three of the new species described by Salas-Gismondi and colleagues had short, reinforced jaws with low, blunt teeth. Paleontologists often follow such anatomical signposts to the conclusion that these animals relied on a diet of hard-shelled prey, or a diet known as durophagy.
Of these crushing caimans, Gnatusuchus was the most extreme. The caiman’s snout was wider than long, and its mouth had a gap between the front and rear teeth. While it’s 13 million years too late to watch the caiman in action, the researchers suspect that Gnatusuchus dug into the Miocene mud with its strong snout to shovel out freshwater clams that the predator busted open with strong snaps of its back teeth.
That paleontologists have found damaged bivalve shells and shed crocodylian teeth worn down to nubs supports the notion that these caimains really were dedicated shell-crushers. And given that many of the delectable invertebrates dug into sediment below oxygen-depleted waters, the air-breathing caimains were able to reach dining spots that shell-busting fish could not access. For the caimans, at least, this glut of food might explain why so many species have turned up at the same sites.
But the crocodylian heyday couldn’t last forever. Around 12 million years ago the proto-Andes started to rise from the land and break up the great South American swamps, replacing lakes and embayments with rivers. For the clam-crushing caimans, feeding grounds became fewer and further between. The new landscape favored sharp-toothed, generalist caimans of the form that inhabit the Amazon today, shadows of an ancient crocodylian paradise.
American alligators are chatty reptiles. They start out their lives chirping for their mother’s help as they push themselves out of their eggs, and, as they grow up, the knobbly archosaurs communicate with a suite of hisses, rumbles, and bellows.
But how do alligators make such sounds? Anatomists have known that alligators and other crocodylians vocalize through their larynx for over a century and a half, but the acoustic abilities of the reptiles have not been as extensively-studied as those of birds and mammals. A new study by Tobias Riede and colleagues is helping to remedy that, including the discovery that a hitherto-unappreciated muscle helps create the crocodylian chorus.
The alligator vocal apparatus isn’t all that different from ours. The reptiles have a larynx and multilayered membranes called vocal folds – better known as vocal chords – that alter airflow as they dilate and vibrate. But to get those parts into the right positions to make sound, alligators rely on muscles.
A muscle called the glottal adductor does some of the work. Depending on which part of the muscle contracts, either the top or the bottom of the vocal folds close. Anatomists have known about this for quite a while. But Riede and coauthors also found that alligators have another important muscle involved in the way other reptiles vocalize, but was thought to be unimportant to crocodylians.
The muscle’s name is a bit of a tongue-twister – cricoarytenoideus. It originates on the first ring of cartilage in the larynx and extends to two other cartilaginous anchors – called the basihyoid and arytenoid, respectively – and the vocal folds. What the muscle does depends on how it contracts. When the rear of the muscle contracts, the whole larynx is pulled back and the vocal folds are held tenser. When front of the muscle contracts, the vocal folds open wide.
How retracting the larynx contributes to an alligator’s vocal repetoire isn’t entirely clear yet. Studying soft tissues while in-use by a toothy owner is quite difficult. All the same, the cricoarytenoideus and other aspects of the alligator’s larynx shows that they have a great deal of vocal control that’s comparable to what’s seen in mammals and birds. And through such comparisons, biologists may be able to give paleontologists a better idea of what the vocal anatomy of long-extinct creatures was like. We may never be able to reconstruct a tyrannosaur’s roar, but, thanks to its living avian and crocodylian relatives, we may be able to narrow down the range of sounds such charismatic, prehistoric creatures were capable of creating.
Dinosaurs are Mesozoic superstars. The largest literally overshadowed other forms of life during their prehistoric heyday, and even now they attract far more attention than any other group of ancient organisms. It’s easy to forget the diverse and disparate species that wove together the ecology that helped support the dinosaurs we are so enchanted by.
This is especially true of the Late Jurassic Morrison Formation. These rocks yielded some of the first dinosaurian superstars – Diplodocus, Stegosaurus, Allosaurus, Ceratosaurus, and more – but in 1987 paleontologist George Callison wanted to remind his colleagues that there was an entire array of “wee fossils” that were often forgotten about. In a paper published by the Museum of Western Colorado in Fruita, Callison highlighted the mammals, smaller crocodiles, pterosaurs, lizards, and other diminutive players that inhabited the same floodplains among the likes of Apatosaurus. Among the lot were a few bones that seemed to mark the early days of a lineage still around us today – fossils that looked as if they belonged to an archaic snake.
The serpent wasn’t published when Callison wrote his paper. And other experts weren’t so sure the bones belonged to a snake. Utah state paleontologist Jim Kirkland, who helped fill in some of the background for this post, remembers that the fossils were too ambiguous to definitively assign to a snake. A lizard seemed a better fit, and this made sense given that snakes and lizards are close evolutionary cousins of each other in the reptile group called squamates.
Almost three decades later, though, Callison has been vindicated. The specimen he alluded to has just been confirmed as among the earliest known snakes. Together with three other species, the Jurassic reptile helps draw back the origin of snakes much further back in time.
From previous finds in Africa, North America, Europe, and South America, paleontologists knew that snakes had evolved by about 100 million years ago and could be found around the globe. They weren’t quite like serpents alive today – some still had hind limbs sticking out from their bodies – but they were undergoing a rapid radiation. From this diversity, paleontologists suspected that they weren’t looking at the origin of snakes so much as an evolutionary bloom already in progress. There were probably older, more archaic snakes. The trick was finding them.
The dawn snakes had been hiding in plain sight for years. A problematic block of 140 million year old fossils from England had helped conceal them. The Jurassic slab contains a variety of small reptile bones, most of which seemed to be from lizards. Some of these bones were given the name Parviraptor and were interpreted as those as a lizard, and they became the standard for interpreting similar fossils found elsewhere. Little bones from Colorado and Portugal, for example, were interpreted as lizards because of their similarity to the bones from England. But University of Alberta paleontologist Michael Caldwell and colleagues have now recognized these fossils as the earliest snakes.
Caldwell and coauthors have named four new snake species spanning 167-143 million years ago, drawing the origin of snakes back over 67 million years into the heart of the Jurassic. The oldest – Eophis underwoodi – is represented by parts of 167 million year old jaws, while Portugalophis lignites lived 155 million years ago in Portugal and the reinterpreted Parviraptor estesi inhabited England about 140 million years ago. And Callison’s fossils have finally been confirmed as falling in the ophidian ranks – the bones he alluded to have been named Diablophis gilmorei, a snake that slithered over fern-covered floodplains about 155 million years ago.
All of these snakes were small, but their exact size is uncertain. Too little is left of them to tell; just pieces of jaw and vertebrae from the front half of their bodies. But these seemingly sparse remains are still enough to tell that Diablophis and kin really are snakes. Even though snakes are modified lizards, they can be distinguished by features of their skulls and teeth. For example, snakes both ancient and modern have short, strongly-recurved teeth with shallow roots and three-sided tooth sockets.
Even though these ancient snakes probably looked different than those sliding along their bellies today – they likely still had hind legs, for starters – Caldwell and colleagues argue that the fossils show the typical snake skull evolved very early in the group’s history. A snake is not defined by a long, legless body, but rather by shared features that show up in the skull. (The same is true of other groups of animals – whales are not united by blowholes or blubber, but by a thickening of part of their ear bones.) This means that the very first snakes were probably almost indistinguishable from their lizard ancestors, identifiable primarily by subtle skull features. As paleontologists continue to search for early serpents, Caldwell and coauthors write, “the fossil record of snake evolution will likely reveal four legged, short bodied ‘stem snakes’ that possess ‘snake’ skull anatomies.” The hunt for the four-legged snakes is on.