Three New Species of Extinct Marsupials Identified
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Dr. Laura Chornogubsky, a paleontologist in the Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’ and CONICET, has described one new genus and three new species in the marsupial family Polydolopidae.

Kramadolops maximus, the youngest known species of polydolopid marsupial. Image credit: Gabriel Lío.

Polydolopidae is a family of extinct marsupials that lived in the Antarctic Peninsula and South America, including Chile, Argentine, Brazil, and Bolivia, during the Paleogene period.

First described by Florentino Ameghino in 1897, these animals appeared at the beginning of the Paleocene epoch, about 66 million years ago, and disappeared during the Oligocene epoch, about 23 million years ago.

They likely went extinct due to climatic deterioration in the Early Oligocene, when temperature and the humidity dropped, provoking desertification in the region where polydolopids evolved.

“In the past, South American marsupials were much more abundant than they are today, with hundreds of species of widely varying shapes and sizes,” Dr. Chornogubsky said.

“Despite the fact that the debate is still open, some of the hypotheses focus on the relationship of polydolopids with Australian marsupials.”

“The polydolopids could have evolved on a large continental mass without major barriers that isolated them. For this reason, the current records of Antarctica show us remains of these groups.”

Dr. Chornogubsky carried out a new taxonomic and systematic revision and the first extensive phylogenetic analysis of the Polydolopidae family.

She examined the fossilized remains of almost every polydolopid species and five related marsupials: Bonapartherium hinakusijum, Epidolops ameghinoi, Microbiotherium tehuelchum, Prepidolops didelphoides, and Roberthoffstetteria nationalgeographica.

“The Polydolopidae was recovered as a monophyletic group, even though no resolution about its sister-group can be found,” she said.

Dr. Chornogubsky redescribed seven previously known genera of polydolopids: Antarctodolops, Amphidolops, Archaeodolops, Eudolops, Kramadolops, Pliodolops, and Pseudolops.

She also described one new genus, Hypodolops, two yet-to-be-named genera, and three new species: Hypodolops sapoensis, Amphidolops intermedius, and Amphidolops minimus.

“This research piece shows advances in the understanding of the evolutionary history of marsupials,” Dr. Chornogubsky said.

The study was published in the Zoological Journal of the Linnean Society.

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Laura Chornogubsky. Interrelationships of Polydolopidae (Mammalia: Marsupialia) from South America and Antarctica. Zoological Journal of the Linnean Society, published online November 26, 2020; doi: 10.1093/zoolinnean/zlaa143

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