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Researchers from the American Museum of Natural History and Louisiana State University have discovered that two groups of blind cave fishes now separated by about 6,000 miles of open ocean are each other’s closest relatives. These eyeless fishes, one group from Madagascar and the other from Australia, descended from a common ancestor before being separated by continental drift nearly 100 million years ago, the scientists say. Their study, which was published this week in the journal PLOS ONE, also identifies new species that add to existing biological proof for the existence of Gondwana, a prehistoric supercontinent that was part of Pangaea and contained all of today’s southern continents.
The cave fishes, of the genus Typhleotris in Madagascar and Milyeringa in Australia, are small—less than 100 millimeters long—and usually lack pigment, a substance that gives an organism its color and also provides protection from the sun’s ultraviolet radiation. These characteristics, coupled with a lack of eyes and enhanced sensory capabilities, are common in many cave organisms.
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Preserved for 230 million years in droplets of amber just millimeters long, two newly named species of mites and a fly have set a record. They are the oldest arthropods – invertebrate animals that include insects, arachnids, and crustaceans – ever found in amber, the name typically given to globules of fossilized resin. The results, published by an international team of researchers in theProceedings of the National Academy of Sciencestoday, pave the way for a better evolutionary understanding of the most diverse group of organisms in the world.
“Amber is an extremely valuable tool for paleontologists because it preserves specimens with microscopic fidelity, allowing uniquely accurate estimates of the amount of evolutionary change over millions of years,” said corresponding author David Grimaldi, a curator in the Museum’s Division of Invertebrate Zoology and a world authority on amber and fossil arthropods.
Even though arthropods are more than 400 million years old, until now, the oldest record of the animals in amber only dates to about 130 million years. The newly discovered specimens are about 100 million years older, the first amber arthropods ever found from the Triassic Period.
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Several years ago, Dr. Nikos Solounias, a visiting researcher specializing in the fossil record of animals from Samos discovered lizard bones mixed in with mammalian fossils that Museum paleontologist Barnum Brown had collected from Greece in 1924. Solounias showed the lizard bones to Jack Conrad, a research associate in the Museum’s Division of Paleontology, who recognized them as those of a varanid, a giant lizard typified by the Komodo dragon. In a new paper in PLOS ONE published last week, Conrad and colleagues Ana Balcarel and Carl Mehling have identified the 30-odd bone fragments, which fit in a box 8 inches long, as the remains of the oldest giant lizard ever to walk the Earth. If proportioned like its relatives, the new species—Varanus amnhophilis, or the Samos dragon—was 6 feet long.
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Hominid fossils recently unearthed in Kenya provide evidence that the evolutionary line from Homo habilis—the earliest known species of the genus Homo—to Homo sapiens is not as direct as once believed, according to a feature story published August 8 in The New York Times. The fossils may confirm the simultaneous existence of at least three Homo species in East Africa some 2 million years ago.
The New York Times story about the discovery quotes Ian Tattersall, who studies the human fossil record as curator emeritus in the Museum’s Division of Anthropology. While Tattersall was not involved in the fossils’ discovery, his work similarly seeks to help unravel the mysteries of human evolution.