Miocene Ground Beetle Fossils Found in Antarctica

Fossilized forewings (elytra) from two individuals, discovered at the Oliver Bluffs on the Beardmore Glacier, revealed the first ground beetle species known from Antarctica. Research describing the new species is published online in the journal ZooKeys.

Fossils of the left and right elytra of the Ball’s Antarctic tundra beetle (Antarctotrechus balli): the left elytron, 2.36 mm in length, is designated as the paratype. A small part of the right elytron of the same individual is attached along the suture near the apex. The siltstone matrix is visible along the outer margin near the apex. The small rhomb-shaped crystals on the surface are authigenic calcite; the right elytron is designated as the holotype; the elytron is 2.40 mm in length; the base is deformed by a crack and concealed by sediment grains; a small part of the left elytron of the same individual is still attached along the suture near the base. Image credit: A.C. Ashworth / T.L. Erwin.

Fossils of the left and right elytra of the Ball’s Antarctic tundra beetle (Antarctotrechus balli): the left elytron, 2.36 mm in length, is designated as the paratype. A small part of the right elytron of the same individual is attached along the suture near the apex. The siltstone matrix is visible along the outer margin near the apex. The small rhomb-shaped crystals on the surface are authigenic calcite; the right elytron is designated as the holotype; the elytron is 2.40 mm in length; the base is deformed by a crack and concealed by sediment grains; a small part of the left elytron of the same individual is still attached along the suture near the base. Image credit: A.C. Ashworth / T.L. Erwin.

“The fossils come from the Oliver Bluffs on the Beardmore Glacier which is a major outlet glacier of the East Antarctic Ice Sheet,” said the authors, Dr. Allan Ashworth of North Dakota State University and Dr. Terry Erwin of Smithsonian Institution.

“The site is within the Transantarctic Mountains about 342 miles (550 km) from the South Pole.”

The scientists named the new species Antarctotrechus balli and gave it the common name Ball’s Antarctic tundra beetle.

“The insect fauna in Antarctica is so poor that today it consists of only three species of flightless midges, with one of them having been probably introduced from the subantarctic island of South Georgia,” they said.

“The absence of biodiversity is considered to be a result of lack of moisture, vegetation and low temperatures.”

Antarctotrechus balli must have inhabited the sparsely-vegetated sand and gravel banks of a meltwater-fed stream that was once part of an outwash plain at the head of a fjord in the Transantarctic Mountains.

Plants associated with this species include southern beech, buttercup, moss mats, and cushion plants, all typical for a tundra ecosystem.

The extinct beetle may or may not have been able to fly.

“The age of the fossils is probably Early to Mid-Miocene (14-20 million years ago),” Dr. Ashworth and Dr. Erwin said.

“The tundra biome, including Antarctotrechus balli, became extinct in the interior of Antarctica about 14 million years ago and on the margins of the continent by 10-13 million years ago.”

Top: the type locality for the Ball’s Antarctic tundra beetle (Antarctotrechus balli) is shown by the red star. Bottom: ancient glacial deposits of the Meyer Desert Formation exposed in the Oliver Bluffs on the flanks of the Beardmore Glacier; the deposits are downthrown along the Koski fault which is marked by the prominent escarpment towards the north end of the bluffs (left on image). The type locality for the species is at the north end of the bluffs marked by a red star. Image credit: A.C. Ashworth / T.L. Erwin.

Top: the type locality for the Ball’s Antarctic tundra beetle (Antarctotrechus balli) is shown by the red star. Bottom: ancient glacial deposits of the Meyer Desert Formation exposed in the Oliver Bluffs on the flanks of the Beardmore Glacier; the deposits are downthrown along the Koski fault which is marked by the prominent escarpment towards the north end of the bluffs (left on image). The type locality for the species is at the north end of the bluffs marked by a red star. Image credit: A.C. Ashworth / T.L. Erwin.

According to the team, Antarctotrechus balli is the second beetle for the Antarctic insect fauna with living descendants.

The closest modern relatives to the species live in South America, the Falkland Islands, South Georgia, Tasmania and Australia.

Tracking the ancient lineage of this group of beetles, known as the carabid beetle tribe Trechini, confirms that they were once widely distributed in Gondwana, the supercontinent that used to unite what today we recognize as Antarctica, South America, Africa, Madagascar, Australia, the Arabian Peninsula and the Indian Subcontinent.

Antarctotrechus balli is also evidence that even after Gondwana broke apart, the tundra ecosystem persevered in Antarctica for millions of years.

_____

A.C. Ashworth T.L. Erwin. 2016. Antarctotrechus balli sp. n. (Carabidae, Trechini): the first ground beetle from Antarctica. ZooKeys 635: 109-122; doi: 10.3897/zookeys.635.10535

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