Saturday 29 September 2018

Napakimyrma paskapooensis: A new species of Relict Ant from the Palaeocene of Alberta, Canada.

Ants are a dominant group in almost all Insect communities today, but this does not appear to have been the case. Stem-group Ants (Ants not descended from the last common ancestor of all living Ants) are known in the fossil record from the Middle Cretaceous onwards, but Cretaceous Ants were rarer and less dominant members of the communities where they were found. Crown-group Ants (Ants descended from the last common ancestor of all living Ants) first appear in the Eocene, and rapidly rose to the ecological dominance we see today. Strangely there is a 23 million year gap between the last fossil Stem-group Ants, in amber from the 78-million-year-old Medicine Hat Formation of North America, and the appearance of the first Crown-group Ants in the 55-million-year-old Fur Formation of Denmark, a gap which encompasses the End Cretaceous Extinction and the entire Palaeocene Epoch. During this entire period only a single possible Ant fossil is known, a specimen from the Palaeocene of Menat in France, which might be an Ant or might be a Potter Wasp.

In a paper published in the journal Acta Palaeontologica Polonica on 27 July 2018, John Lapolla of the Department of Biological Sciences at Towson University and Phillip Barden of the Department of Biological Sciences at the New Jersey Institute of Technology, describe a new species of Relict Ant from the Palaeocene Paskapoo Formation in Alberta.

Relict Ants, Aneuretinae, are known only from a single species today, the Critically Endangered Sri Lankan Relict Ant, Aneuretus simoni, though nine fossil species have previously been described, leading entomologists to conclude that they were the last survivors of a group only distantly related to other Crown-group Ants, though modern DNA-based phylogenetic methods have shown them to be closely related to the much more widespread and diverse Dolichoderine Ants.

The Paskapoo Formation comprises a series of Middle-Late Palaeocene sandstones, gravels, mudstones and conglomerates, thought to have been laid down in a meandering river valley, with occasional palaeosols (fossil soils) and coal beds thought to have been laid down in wooded swamps on the river, which have produced numerous Insect and Plant fossils.

The new species is named Napakimyrma paskapooensis, where 'Napakimyrma' is a combination of the Cree 'Napaki', meaning 'flat' and the Greek 'Myrma', meaning 'Ant', to make 'Flat Ant', and 'paskapooensis' means 'from Paskapoo'. The species is described from a single worker Ant 6.8 mm in length, preserved as part and counterpart on a piece of split limestone. 

Relict Ant Napakimyrma paskapooensis from the Paleocene Paskapoo Formation at Dennis Wighton site 1 of Blackfalds Insect and Plant Site. Automontage generated photographs (A, B), line drawing (C). Lapolla & Barden (2018).

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