Siberian unicorns lived alongside humans

A reconstruction of what a Siberian unicorn might look like, by Heinrich Harder in 1908Heinrich Harder/Wikimedia Commons

Ancient rhinos were basically magic.

By Sara Chodosh

All rhinos are unicorns, really—they just aren't pearly white and magical the way our myths say they should be. These powerful beasts get their strength from stocky muscles and keratinized body armor instead of rainbows and magic, but they're the only unicorns we've got. And one extinct species is named accordingly: the Siberian unicorn.

Elasmotherium sibericum was the last remaining survivor of the Elasmotherium genus, which was once a large, diverse group of giant rhinos. Siberian unicorns were once thought to have gone extinct during a broad "background extinction" that occurred during the early and middle Pleistocene, which covers a period from around 126,000 to 2.5 million years ago. The species hadn't been studied much, but it was previously thought that E. sibericum died out roughly 100,000 to 200,000 years ago.

But new research dating the fossilized molars of these ancient unicorns shows that they lasted all the way to the late Quaternary megafaunal extinction. That's the scientific name for the event you know as the end of the last ice age when many retroactively beloved animals—saber-toothed tigers and woolly mammoths, for instance—died out as the climate changed. The paper, published this week in the journal Nature Ecology & Evolution, dates the most recent fossils to around 35,000 to 39,000 years old. Humans started widely dispersing just before the megafaunal extinction, so there's been a lot of debate in the past about whether the widespread deaths of various species are due to overhunting or to climate change.

First published restoration of Elasmotherium sibiricumRashevsky, under supervision of A.F. Brant

In this case, though, it looks like the increase in temperature is what killed off these giant beasts. The researchers note in this recent paper that Siberian unicorns had some extreme adaptations that limited their diet, so when vegetation began to change E. sibericum simply couldn't change fast enough to survive. The lineages that begat modern antelopes and rhinos survived this extinction by evolving to eat a different diet, which they could do because they browsed and grazed on a variety of plants. Siberian unicorns couldn't. Based on the angle between the back of their head and their palate (the bone on the roof of your mouth), researchers think Siberian unicorns held their heads even lower than modern rhinos. This allowed them to eat vegetation very close to the ground. But when their ecological niche disappeared, so did they.

The authors point out that extinction was especially likely because E. sibericum had a highly restricted geographic range, a small population size, and a low reproductive rate. Rhinocerotinae, the group that includes modern rhinos, survived while their Elasmotherium cousins died out. This paper also shows that the two groups had split long before, somewhere around 43 million years. Though they looked superficially similar, ancient rhinos were mostly part of a highly specialized group that simply couldn't survive a massive shift in climate.

We know all of this now because this group of researchers decided to actually look at the evidence they already had in front of them. The 25 specimens they performed radiocarbon dating on were in various museum collections, but as they wrote in the study, no dating or genetic analysis had been done for the species. At last, these real-life unicorns are getting their day in the sun.

Did Dakotaraptor Really Face Off Against Tyrannosaurus?

Dakotaraptor pulls feathers from Ornithomimus it killed. Art by Emily Willoughby.

by Brian Switek

By now you’ve probably heard about the giant “raptor” uncovered in South Dakota. The dinosaur’s discovery came as quite a shock. For the past centuryTyrannosaurus rex has dominated our imaginations as the sole apex predator of the Hell Creek Formation, but Dakotaraptor steini, as Robert DePalma and coauthors dubbed the dinosaurs, was large enough to compete for flesh with young tyrannosaurs.

With scenes from the Jurassic Park franchise still stomping through our imaginations, it’s tempting to pit packs of 18-foot-long Dakotaraptor against the heavyweight champion T. rex, mobbing the bulky carnivore off its kills. DePalma has suggested as much, calling Dakotaraptor “the most lethal thing you can possibly throw into the Hell Creek ecosystem.”

But before we get too carried away and start commissioning murals of giant raptors slashing the flesh of Tyrannosaurus Age of Reptiles style, it’s worth thinking about what the world of dinosaurs was really like.

The known elements of Dakotaraptor and a reconstructed skeleton. From DePalma et al., 2015.

 

Dakotaraptor ups the diversity of dinosaurs known from the Hell Creek Formation. It’s an increase of one new species. And finding a new species means that there must have been a population of these big dromaeosaurids running around that paleontologists have missed up until now. (Although the idea of cooperative raptor packs rests on only the barest sliver of evidence right now.) But this doesn’t mean that where there was Tyrannosaurus, Dakotaraptorfollowed. What I’m getting at is a concept ecologists call species evenness.

Let’s take an avian dinosaur’s-eye view of the big Hell Creek Formation carnivores. We’ll cover Tyrannosaurus first. This dinosaur is known from about 50 partial-to-nearly-complete skeletons found in rocks between 68 and 66 million years old spanning Saskatchewan to New Mexico, at the very least.Dakotaraptor, on the other hand, is only known from a partial adult individual found near the top of the Hell Creek Formation in South Dakota and a smattering of other isolated elements from that area.

The fossil record is biased, of course. What’s preserved in the rocks is not a perfect record of life as it once was, and there are various other reasons whyDakotaraptor is so rare. Perhaps the dinosaur was the wrong size to be preserved as often as Tyrannosaurus. Maybe teeth and other pieces of this dinosaur were found before but could not be recognized as belonging to a giant raptor until now. Or the commercial fossil market could have snaffled up some of the relevant bones, making them inaccessible to paleontologists.

Future finds will inform what we know about the abundance and distribution ofDakotaraptor. But what if it took so long to find this predator because it truly was a rare animal with a relatively limited range? In terms of species evenness, in other words, the current spread of what we know is heavily imbalanced.Tyrannosaurus was extremely abundant and widespread while Dakotaraptorseems elusive, even by mid-size dinosaur standards.

This isn’t a knock against Dakotaraptor. Quite the opposite. If the dinosaur’s rarity isn’t stemming from a biased fossil record or a problem with sampling, then Dakotaraptor might eventually yield some new information about Hell Creek Formation ecology.

“Jane” is our best look at a juvenile T. rex. Photo by Brian Switek.

 

Up until now, Hell Creek Formation carnivores seemed to be widely split. There wasn’t a gradient from the small to the gargantuan as there was in the Late Jurassic Morrison Formation, but a wide gap between little nippers likeAcheroraptor and the lone giant, Tyrannosaurus. What was in the middle, then, were juvenile Tyrannosaurus – lithe, leggy youngsters that had jaws better-suited to stripping flesh than to delivering crushing bites.

Dakotaraptor changes that picture. At least one other mid-sized predator was able to evolve and survive within the domain of Tyrannosaurus. YetDakotaraptor may have been so elusive because Tyrannosaurus still maintained a disproportionate presence on the landscape, or perhaps becauseDakotaraptor typically lived in upland environments that weren’t preserved as often as the wet lowlands Tyrannosaurus frequented. So even though it’s possible, even probable, that Dakotaraptor and young Tyrannosaurus faced off over carcasses from time to time, it’s not as if Hell Creek Formation time was an era of constant shrieks, roars, and ruffled feathers.

Ceratosaurus was rare compared to Allosaurus. Photo by Brian Switek.

 

This wouldn’t be the first time carnivorous dinosaur tallies have come out uneven. At the Late Jurassic Cleveland-Lloyd Dinosaur Quarry, for example, the remains of at least 48 Allosaurus have been uncovered while the same site has yielded only a single Ceratosaurus, a few Torvosaurus bones, and single-digit counts of the medium-sized carnivores Marshosaurus and Stokesosaurus. This pattern holds at a wider, rougher view, as well. Allosaurus was the most common large carnivore of the Morrison Formation with Ceratosaurus trailing behind in count and range, followed by even rarer and more restrictedTorvosaurus, Stokesosaurus, and Marshosaurus. So, with a count of at least five, we can say that the upper part of the Morrison Formation had a diversearray of mid- to large-sized carnivorous dinosaurs, but that their numbers were not at all even.

Why different dinosaurs were unevenly spread in a given habitat or formation isn’t something that’s well-understood. It’s difficult to study an ecosystem that’s been dead for at least 66 million years. Answers could range from how we sample the fossil record to instances of niche partitioning like habitat preference or seeking particular food sources. There’s still plenty of rock to shift and dinosaurs to count. But if we’re ever going to fully understand dinosaurs, we need to step back from the carnivore vs. carnivore fights we used to imagine in the sandbox and try to understand them as animals that were each part of ever-shifting ecosystems. Dinosaurs weren’t monsters stalking around on unimportant backdrops. The endpoint of raising their bones in the first place is to envision how they fit into lost worlds.

Reference:

DePalma, R., Burnham, D, Martin, L., Larson, P., Bakker, R. 2015. The first giant raptor (Theropoda: Dromaeosauridae) from the Hell Creek Formation.Paleontological Contributions. doi: 10.17161/paleo.1808.18764

Meet Pentecopterus, a new predator from the prehistoric seas

By Jim Shelton

(Illustration by Patrick Lynch)

You don’t name a sea creature after an ancient Greek warship unless it’s built like a predator.

That’s certainly true of the recently discovered Pentecopterus, a giant sea scorpion with the sleek features of a penteconter, one of the first Greek galley ships. A Yale University research team says Pentecopteruslived 467 million years ago and could grow to nearly six feet, with a long head shield, a narrow body, and large, grasping limbs for trapping prey. It is the oldest described eurypterid — a group of aquatic arthropods that are ancestors of modern spiders, lobsters, and ticks.

A detailed description of the animal appears in the Sept. 1 online edition of the journal BMC Evolutionary Biology.

“This shows that eurypterids evolved some 10 million years earlier than we thought, and the relationship of the new animal to other eurypterids shows that they must have been very diverse during this early time of their evolution, even though they are very rare in the fossil record,” said James Lamsdell, a postdoctoral associate at Yale University and lead author of the study.

“Pentecopterus is large and predatory, and eurypterids must have been important predators in these early Palaeozoic ecosystems,” Lamsdell said.

Geologists with the Iowa Geological Survey at the University of Iowa discovered the fossil bed in a meteorite crater by the Upper Iowa River in northeastern Iowa. Fossils were then unearthed and collected by temporarily damming the river in 2010. Researchers from Yale and the University of Iowa have led the analysis.

The fossil-rich site yielded both adult and juvenile Pentecopterus specimens, giving the researchers a wealth of data about the animal’s development. In addition, the researchers said, the specimens were exceptionally well preserved.

“The Winneshiek site is an extraordinary discovery,” said Yale paleontologist Derek Briggs, co-author of the study. “The fossils are preserved in fine deposits of sediments where the sea flooded a meteorite impact crater just over 5 km in diameter.” Briggs is the G. Evelyn Hutchinson Professor of Geology and Geophysics at Yale and curator of invertebrate paleontology at the Yale Peabody Museum of Natural History.

“What’s amazing is the Winneshiek fauna comprise many new taxa, including Pentecopterus, which lived in a shallow marine environment, likely in brakish water with low salinity that was inhospitable to typical marine taxa,” said Huaibao Liu of the Iowa Geological Survey and the University of Iowa, who led the fossil dig and is a co-author of the paper. “The undisturbed, oxygen-poor bottom waters within the meteorite crater led to the fossils’ remarkable preservation. So this discovery opens a new picture of the Ordovician community that is significantly different from normal marine faunas.”

The National Science Foundation supported the research. Additional co-authors of the study were Robert M. McKay and Brian Witzke of the Iowa Geological Survey and the University of Iowa.

15 Terrifying Prehistoric Animals We’re Glad We Never Had to Encounter

1. Jaekelopterus

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They were top predators in the Middle Devonian period, around 390 millions years ago. Three words, Giant Sea Scorpion. That’s right, this 8 foot long arthropod lived in the water and had pincher claws. Frankly, all of the eurypterids are scary as hell and this entire post could be exclusively about how terrifying these things look. Many of them look eerily similar to the face huggers from the Alien movie franchise; they are nightmare fuel. Jaekelopterus had segmented bodies with multiple specialized limbs, some with spikes. They had spring loaded claws to snatch up fish as they passed by, with the largest having an 18 inch spiked claw. Smaller sea scorpions are known to have crawled ashore to mate and even shed their outer skin. Imagine finding the molt of one of these monsters on the shore just before going swimming. Already with a sense of dread and paranoia, you distance yourself from the shore…and then you see a shadow in the murky waters.

2. Helicoprion

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The mystery of this bizarre fish starts with a weird fossil and numerous attempts to figure out what it was and how to classify it. Helicoprion puzzled paleontologists and ichthyologists for over a century. The only remains of this creature, up until 2013, were from a fossilized whorl of teeth. While most scientists agreed that the teeth belonged to the lower jaw, that didn’t prevent the presumed location of the teeth from migrating around the body in sometimes fanciful arrangements that can be seen in numerous illustrations and reconstructions. With the later discovery of some portions of a jaw, the location of its buzzsaw-like teeth were finally determined to fill the lower jaw. Strangely, there were no upper teeth; so this creature could disgustingly gum and bite you at the same time. The jaw would close, rotating the teeth backwards, much like a circular saw blade. It probably fed on the soft bodies of squid and other cephalopods. The whorl of teeth was formed as they continuously grew outwards, creating a spiral as it aged; the teeth at the beginning of the whorl being small and gradually increasing in size toward the end. Another fish with an equally odd and terrifying face, Edestus, had offset scissor like jaws that protrude out of its face.This isn’t actually a member of the shark family – sharks have pretty much remained the same for the past 400 million years. The helicoprion was a survivor – having lived through the Carboniferous period, the Permian period, and even the largest extinction event in history (where 90% of life was wiped out), and went extinct in the early Triassic period.

3. Fasolasuchus

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This monstrous 33 ft cousin of crocodiles is one of the largest non-dinosaur carnivores to have ever lived. It’s hard to imagine anything hunting a dinosaur, but these were the fellas to do it. Fasolasuchus is t-rex Triassic, it can reach 10 meters of long.Il can attack large prey like the giant prosaupode lessemsaurus. Not being quick it hunts its prey by ambush. It is the tyrant of the Triassic!

4. Kelenken

The Kelenken was a species of giant flightless predatory birds of the extinct family phorusrhacid, or "terror birds" that lived in the Middle Miocene, some 15 million years ago, in Argentina. It is closely related to the Cariamids. Kelenken was the top predator of its area and hunted other predators too. Kelenken, rather than flying, it ran fast, running up to 35 mph (56.3 kph). With a skull 71.6 cm (28.2 inches) long, it had the largest head of any known bird. It is the largest species of phorusrhacid. Phorosrachids ruled South America some 15 million years ago. Dinosaurs had all died out, and these guys were the new thing about town. They moved on two legs, they were extremely agile, and they could have beaks as long as 18 inches.

5. Therizinosaurus

The killer claws of raptors are nothing compared to those of the therizinosaurus. The 33 ft animals had claws as long as 3 ft. Despite this, the animal was actually mostly herbivorous, so those claws were used for weeding more than anything. Still badass. Therizinosaurus is a genus of very large therizinosaurid dinosaurs that lived during the Late Cretaceous period in what is now Asia. It contains a single species, Therizinosaurus cheloniformis, known from the fossiliferous Nemegt Formation. The first remains of Therizinosaurus were found in 1948 by a Mongolian field expedition in the Gobi Desert and later described by Evgeny Maleev in 1954. The genus is only known from a few bones, including gigantic manual unguals (claw bones), from which it gets its name, and additional findings comprising fore and hindlimb elements that were discovered from the 1960s through the 1980s.

Therizinosaurus was a colossal therizinosaurid that could grow up to 9–10 m (30–33 ft) long and 4–5 m (13–16 ft) tall, and weigh possibly over 5 t (5.5 short tons). Like other therizinosaurids, it would have been a slow-moving, long-necked, high browser equipped with a rhamphotheca (horny beak) and a wide torso for food processing. Its forelimbs were particularly robust and had three fingers that bore unguals which, unlike other relatives, were very stiffened, elongated, and only had significant curvatures at the tips. Therizinosaurus had the longest known manual unguals of any land animal, reaching above 50 cm (20 in) in length. Its hindlimbs ended in four functionally weight-bearing toes differing from other theropod groups in which the first toe was reduced to a dewclaw and also resembling the very distantly related sauropodomorphs.

6. Sauroniops

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These giants stood tall at a whopping 42 ft. They lived in Morocco around 100 million years ago, and they’re absolutely terrifying!

7. Deinosuchus

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Like its cousin the fasolasuchus, the deinosuchus were crocodiles who hunted dinosaurs. What a world. 42 ft long and always ready to strike, the Texas natives were around, kicking ass, around 80 million years ago.

8. Dunkleosteus

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 This 33 foot long armored fish from the Devonian era lacked teeth, but its jaw contained razor sharp protrusions of bone that it could use to pierce and cut through its prey. These bones grew continuously and as they did, the edges rubbed together with those of the opposing jaw, acting like self sharpening shears. This would ensure the “fangs” were always ready to chomp into armored prey like arthropods, ammonites and other fish. This four ton monster fish patrolled inshore waters and could snatch prey up by opening and closing its jaws within 50-60 milliseconds.The dunkleosteus, with its guillotine-like mouth actually had no teeth. Those blades you see were actually a part of their skull. They were over 30 ft, and hunted sharks for about 20 million years.

9. Livyatan

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This extinct whale was named both for the monstrous sea creature Leviathan from the old-testament that “…when he rises up, the mighty are terrified; they retreat before his thrashing” and for Herman Melville, the author of the novel Moby Dick, a tale of an accursed white whale that terrorized Captain Ahab and eventually brought about his death and the destruction of his ship and crew. This is an amazing namesake to live up to. Livyatan melvillei is related to modern sperm whales like Moby Dick and lived during the Miocene epoch. It was 44-57 feet long and had a 10 foot long skull that housed forty 14.5" long teeth. These are the longest teeth used for feeding known from any animal, extinct or alive. They fed on large prey at the surface of the water including other whales. This whale likely became so large because it was competing directly with megalodon for food. Named after Leviathan, these enormous whales were fearsome shark hunters. With teeth up to 1 ft long they were ruthless, unstoppable beasts. They were an outrageous 57 ft long. They conquered the megalodons, who ruled the sea for millions of years. They were badass.

10. Mosasaurus

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Mosasaurus is a species of large marine reptile from the Late Cretaceous period, around 83-66 million years ago. One of the largest of its genus, measuring nearly 18 meters long and weighing 10 tons, Mosasaurus gave its name to a group of carnivorous marine lizards - the Mosasaurs. The Late Cretaceous period may very well have been the most dangerous for ocean dwellers, and its precisely because of these guys. Mosasaurus was one of the largest aquatic predators that had ever evolved, at over 60 ft long. They didn’t just hunt sharks, they hunted pretty much anything they could lock their jaws on (and they could pretty much lock their jaws on anything)

11. Deinotherium

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These are the largest prehistoric relative of modern-day elephants. They arrived in the Middle Miocene and survived until the Early Pleistocene, changing very little along the way. Their remains were discovered at major hominid excavation sites near Lake Turkana, Kenya. They’re also known as “hoe tuskers”.

12. Epidexipteryx

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These are the earliest known representation of ornamental feathers in the fossil record. They were a genus of small paravian dinosaurs.

13. Hallucigenia

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These were less than 3 millimeters long, and had bulbous round heads connected to their cylindrical trunk. It was initially thought to walk on its spines, but it was later discovered that its tentacles were feet.

14. Tanystropheus

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Tanystropheus is the Greek word for “long necked one”. They were 20 feet long, with a narrow neck that was often longer than its body and neck combined. They emerged in the Middle Triassic period.

15. Opabinia

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These are one of the most bizarre creatures to have ever existed. They had 30 legs, 30 flippers, a nose like an elephant’s trunk, and a lobster-like claw. There were no signs that they had jaws, so they presumably fed on small, soft creatures.