Antarctic flies

A newly classified fossil provides evidence that higher flies also lived in Antarctica.

By | May 8, 2003

It has been assumed that the Antarctic has never been colonized by the higher fly species — the Diptera or "true" flies. In a Brief Communication in the May 8 Nature, Allan C. Ashworth and F. Christian Thompson from North Dakota State University in Fargo describe a fossilized pupa that shows classical dipteran morphology and is derived from rock deposited during the Neogene epoch (3–17 million years ago) (Nature, 423:135-136, May 8, 2003).

Ashworth and Thompson extracted the fossil from a Neogene siltstone outcrop at the Beardmore Glacier, approximately 500 km from the South Pole. Using scanning electron microscopy, they estimated the fossil length to be 5 to 7.5 mm and discovered that it bore structures consistent with it being a cyclorapphan dipteran. These structures include a single pair of round spiracles, an integument with circular patterning (reflecting the chitin secretion pattern), spines on the ventral welt, and the ecdysial scar from the second-instar stage of development. On the basis of these observations, they assigned the fossil to the Cyclorrhapha but were unable to assign it a family.

They suggest that the flies must have colonized Antarctica during a warm period in the Neogene or that they belonged to the fauna of the ancient continent of Gondwanaland, surviving for millions of years before becoming extinct. "If better preserved fossils are found in Antarctica, a radical revision of the age and place of origin of the Cyclorrhapha might one day be necessary," conclude the authors.

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