Absurd Creature of the Week: This Prehistoric Elephant Had a Huge Spork for a Mouth
Russian writer Anton Chekhov insisted that everything irrelevant to a work of fiction be removed — if you describe a rifle mounted on the wall, someone had better fire it off at some point. This dramatic principle is called Chekhov’s gun, and it actually applies quite well to the natural world: Animals don’t waste energy developing worthless characteristics. Traits that help a species survive get passed along through generations, while those that are no longer useful fade away (or in the stubbornly contrary case of the human appendix, abruptly explode).
Platybelodon’s remarkable modified tusks. Image: American Museum of Natural History, via the Biodiversity Heritage Library
If Chekhov had time-traveled back between 8 million and 20 million years and met Platybelodon — an ancestor of the modern elephant that looked like it got hit in the face with a shovel, then absorbed that shovel into its mouth — he would have demanded the creature explain itself. What possible purpose could such a ridiculous trait serve? “A good one, thank you very much,” Platybelodon would reply, probably in a really funny voice.
The spork-faced Platybelodon’s strange jutting jaw actually consists of a second pair of flattened, widened tusks (tusks themselves being modified incisors). When the genusPlatybelodon, which means “flat tooth,” and its species were first described in the 1920s, “their lower incisors were thought to function to shovel, scoop, dig and dredge soft vegetation in aquatic or swampy environments,” vertebrate paleontologist William Sanders of the University of Michigan wrote in an email to WIRED. “But recent analysis of tusk wear surfaces show that they were used more as scythes to cut tough vegetation.”
The paleontologist who proposed this slicing behavior in 1992, David Lambert, theorized that instead of roaming shorelines, Platybelodon fed on terrestrial plants, grasping branches with its trunk and cutting them away with its built-in scythe. Indeed, cross-sections of the tusks reveal a structure that provides extra strength and resistance to abrasion for such foraging, said Sanders.
Pegging the various appearances of such proboscideans, though, is difficult, because flesh-like schnozes don’t fossilize as easily as bone. We’re actually quite lucky to have Platybelodon preserved at all, considering that fossilization is a really hard thing to pull off. Even if you can avoid getting carted off in a dozen different directions by scavengers, you need to settle in the right spot. And Platybelodon just so happened to do us a solid by dying — sometimes en masse — next to or in rivers, the prime locales for fossilization.
Osborn’s reconstruction of Platybelodon from his 1936 book Proboscidea. Males sported larger scythes than females — an example of sexual dimorphism. Image: American Museum of Natural History, via the Biodiversity Heritage Library
Henry Fairfield Osborn, a paleontologist who described Platybelodon in a 1932 paper and quite extensively four years later in his book Proboscidea, accordingly assumed the creature to be a water-dredger (thanks to the work of Lambert and others we now believe that Platybelodon, like a lot of animals, was probably just partial to water and happened to sometimes die in it). In his book, Osborn quoted another paleontologist, Alexei Borissiak, who in 1929 wrote that Platybelodon was “deprived of a trunk” but would scoop through the water and “seize its food with its muscular upper lip, covering the mandible.” In fact, Borissiak reckoned Platybelodon’s snout looked a bit like that of the hippopotamus, “although much more lengthened out.” Osborn’s illustrations of Platybelodon certainly reflect this.
But “think about what an elephant looks like,” Sanders asks us. “The trunk is a very separate entity from the mouth. You have to be able to get food into your mouth, and if your front limbs are occupied in posture, and you have upper and lower tusks that would make it difficult to have a long projecting tongue or mobile lips, then you need a proboscis.”
A model of Platybelodon featuring a dexterous proboscis, in keeping with Lambert’s grab-and-slash theory. Image: Wikimedia
“[Osborn's] ego preceded his expertise,” he added, “and we are still digging out from the weight of his ‘authority’ on proboscideans.” Yet Osborn’s flat trunk/lip persists in most modern reconstructions — including an oh-so-close-to-actually-being-cute one in the Ice Age movies — conflicting with Lambert’s more widely accepted grab-and-scythe theory.
Trunks aside, could the bizarre mug ofPlatybelodon, so wonderfully adapted for feeding, have proved cumbersome when, say, fleeing from predators? Sanders doesn’t think so. And even ifPlatybelodon did face-plant here and there, its size would have proved quite the advantage as far as not getting eaten goes. It was somewhat smaller than the modern African elephant, which only rarelyfalls prey to that continent’s apex predator, the lion. But according to Sanders, Platybelodon might have had a counterpart predator in the ferocious wolf-like creodonts, meaning “flesh tooth,” meaning a slicing tooth designed to deprive you of flesh, meaning let’s be grateful it was Platybelodon worrying about them and not us.
So be they teeth like scissors or teeth like a shovel, evolution never creates a rifle it doesn’t intend to fire. Where fiction has Chekhov’s gun, nature has Platybelodon’s giant spork.
Read full here... http://www.wired.com/wiredscience/2013/10/satellites-map-sinking-venice/
