| Pneumodesmus newmani Temporal range: Late Silurian |
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|---|---|
| Photomicrograph of the type specimen | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Myriapoda |
| Class: | Diplopoda |
| Order: | Cowiedesmida |
| Family: | Cowiedesmidae |
| Genus: | Pneumodesmus |
| Species: | P. newmani |
| Binomial name | |
| Pneumodesmus newmani Wilson & Anderson, 2004 [1] |
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Pneumodesmus newmani is a species of millipede that lived 428 million years ago, in the Late Silurian.[1][2] It is the first myriapod, and the oldest known creature to have lived on land.[3] It was discovered in 2004, and is known from a single specimen from Stonehaven, Aberdeenshire, Scotland.[2]
The single, 1 cm-long fragment of P. newmani was found by Mike Newman, a bus driver and amateur palaeontologist from Aberdeen, in a layer of sandstone rocks on the foreshore of Cowie, near Stonehaven.[4] The species was later given the specific epithet "newmani" in honour of Newman. The holotype is kept in National Museum of Scotland, Edinburgh.[5]
The fossil is important because its cuticle contains openings which are interpreted as spiracles, part of a gas exchange system that would only work in air. This makes P. newmani the earliest arthropod with a tracheal system, and indeed the first oxygen-breathing animal on land.[3][6]
Ichnofossils of myriapods are known dating back to the late Ordovician, but P. newmani is the earliest body fossil of a millipede, and has been dated to 428 million years ago (late Wenlock epoch to early Ludlow epoch). The earliest centipedes follow some 10 million years later,[6] and the first vertebrate on land, Tiktaalik, is 50 million years younger than Pneumodesmus.[7] During the Silurian, the rocks that would later be part of Scotland were being laid down on the continent of Laurentia, in a tropical part of the Southern Hemisphere.[8]