March 3, 2016 | David F. Coppedge

Weird Animals You Never Heard Of

Welcome to a menagerie of believe-it-or-not creatures that once inhabited our planet (or still do).

Saber-tooth swimming otter-bear (Live Science, PhysOrg): “A mysterious, carnivorous marine mammal that lived 23 million years ago clamped down on its mussel dinner similar to the way a saber-toothed tiger grasped its larger prey, scientists have found.” The big sea-otter-like mammal had the bite of Smilodon without the saber teeth, but is only known from a few fossils. Lack of post-cranial fossils didn’t stop artists from drawing pictures of humpbacked, clawed hunters resembling grizzly bears.

Humvee armadillo (Current Biology, Science Daily). The mysterious glyptodonts of the Ice Age have been reclassified as a subgroup of armadillos, but these armed mammals would dwarf any alive today. With spiked tails and armor reminiscent of ankylosaurs, they were as big as a car and roamed the world alongside saber-tooth cats and giant ground sloths in South America. See the BBC News for a short video about them.

Barrel-chested giant globetrotting turtle (Live Science): This article describes pareiasaurs, large “turtle relatives” with round abdomens, stubby legs and ugly faces (if inferred correctly from bones). Despite their rotund appearance on short legs, they apparently found their way to China, Russia, South Africa, South America and Europe. Found in Permian strata, pareiasaurs enjoyed a global success in what is claimed an evolutionary short period of 10 million years. The article doesn’t mention ancestors, and doesn’t elaborate on the alleged relationship to turtles.

Baby dragons (Live Science): That’s what Live Science calls them: baby dragons, ready to hatch in a Slovenian cave. But are they “human fish” instead? No, neither: they are cave salamanders with a fleshy pink appearance and frills that look downright dragonian. People in the 1600s thought they were baby dragons when some washed out of a cave. Strangely, they are born with functioning eyes, but the eyes degenerate in the cave environment. Called olms, they hatch from eggs, taking 14 years to reach maturity. Some can live 70 years.

Frozen Survivor (PhysOrg): A water bear (tardigrade) has survived 30 years frozen in ice, this article says. Despite their small size, they are remarkably complex and durable (see Evolution News & Views for discussion of the challenge tardigrades present to arthropod phylogeny).

Amazing FactsThe approximately 0.2 mm long tardigrades were retrieved from a frozen moss sample collected in Antarctica in November 1983. In May 2014, the moss was defrosted (at 3 °C for 24 h) and soaked in water (for an additional 24 h). Two individuals and one egg were collected from the sample and reared on agar plates with algae provided as food. One of the revived tardigrades and the juvenile that hatched from the revived egg went on to continuous reproduction successfully.

Underwater butterflies (Live Science, New Scientist): They are mollusks of the snail variety, but they “fly” underwater in a manner similar to butterflies. Endowed with “wing-like appendages that allow them to swim,” these shy, fragile “sea butterflies” use the same mechanical principles as their aerial analogues to propel themselves, scientists have found using 3-D cameras. How could such different animals use the same flight mechanisms? You guessed it: “convergent evolution.”

Even though gastropods and insects diverged from a common ancestor 550 million years ago, sea snails use the same clap-and-fling mechanism flies use, which involves bringing their wings together then quickly pushing them apart.

This shows evolutionary convergence on a similar locomotion technique to move through a similar environment. Due to their tiny size, the balance of inertial and viscous forces sea snails come across in water is similar to that experienced by flies in air.

Empty sock without a tree house (Science Daily): Nature reported that weird flatworm-like creatures without brains, eyes or guts have finally been assigned an evolutionary place in the tree of life. Called Xenoturbella, these “acoel” (“no cavity”) marine flatworms, just an inch or more long, have confused scientists for years. “Sometimes it is the most unassuming animals that cause the most consternation,” the article begins. A new classification announced in Nature places them at the base of bilateria (animals with bilateral symmetry), but scientists will undoubtedly puzzle more about them. Live Science says, “They have no digestive system, no excretory system, no reproductive organs, but they probably don’t worry about that too much because they don’t have brains, either — just a neural network.” Leave it to a Darwinian to smirk, “‘These features means that we humans also crawled the ocean floor next to mud and grains of sand 560 million years ago,’ Hejnol explains with a smile on his face.”

Hejnol should reflect upon the fact that a smile on his face requires the coordinated action of many muscles, nerves, and thousands of irreducibly complex molecular machines. You can’t get there from an empty sock. Each of these creatures, even the flatworm, is (or was) matched to its environment with similar complexities at the cellular level. You can learn about them without having to tell stories about how they morphed into each other over millions of years, diverging and converging in mysterious ways.






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