Sunday, September 2, 2012

Amber arthropods

Wouldn't one of the objects above make a lovely teardrop pendant? No, they're not poop. They are drops of tree sap that oozed out of conifers in the extinct family Cheirolepidiaceae. It happened 230 million years ago in the Dolomite Alps of northeastern Italy, and when it did the resin enveloped the insects that were feeding on the trees at the time and fossilized into amber. Of the 70,000 droplets 2-6mm long (photo here) that were discovered and screened for animal and plant inclusions, these 3 contained the most ancient invertebrates ever found in amber. The specimens - a nematoceran fly and 2 different species of mites (photos here) - are known to have existed 400 million years ago, but the oldest record of the animals in amber dates to 130 million years, making the newly discovered specimens older by 100 million years. Yet they were remarkably similar to today's mites: "Antiquity of the gall mites in much their extant form was unexpected, particularly with the Triassic species already having many of their present-day features (such as only two pairs of legs); further, it establishes conifer feeding as an ancestral trait," write David Grimaldi and his co-authors in the Proceedings of the National Academy of Sciences. Because most of today’s gall mites feed on flowering plants, which didn't exist back then, the finding suggests that gall mites evolved with their hosts over time.
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