''Pneumodesmus newmani'' is a species of myriapod that lived in the Paleozoic. Its exact age is uncertain; it was originally interpreted as living , in the

Late Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

; however, subsequent research dates it to around 414 million years old, in the Early

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

( Lochkovian). It is one of the first myriapods, and among the oldest creatures to have lived on land. It was discovered in 2004, and is known from a single specimen from Stonehaven,

Aberdeenshire Aberdeenshire ( sco, Aiberdeenshire; gd, Siorrachd Obar Dheathain) is one of the 32 Subdivisions of Scotland#council areas of Scotland, council areas of Scotland. It takes its name from the County of Aberdeen which has substantially differe ...

, Scotland.

Discovery and naming

The fossil 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. The species was later given the

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

"''newmani''" in honour of Newman. The holotype is kept in

National Museum of Scotland The National Museum of Scotland in Edinburgh, Scotland, was formed in 2006 with the merger of the new Museum of Scotland, with collections relating to Scottish antiquities, culture and history, and the adjacent Royal Scottish Museum (opened in ...

, Edinburgh. The genus name is said to derived from the Greek ''pneumato'', meaning "air" or "breath", in reference to the inferred air-breathing habit. The proper word in ancient Greek for "air" or "breath" is however ''pneuma'' (πνεῦμα).

Description

The single, 1 cm-long fragment of ''P. newmani ''depicts small paranota (keels) high on the body, long, slender legs. There are six body segments preserved, and the dorsal portion of each segment is ornamented with a horizontal bar and three rows of roughly hexagonal bosses (bumps). Myriapods are the group that include millipedes and centipedes, and ''Pneumodesmus newmani'' would have resembled a millipede in appearance. However it did not belong to the same branch of myriapods as modern millipedes.

Significance

The fossil is important because its cuticle contains openings which are interpreted as

spiracle Spiracle or spiraculum may refer to: * Spiracle (arthropods), opening in the exoskeletons of some arthropods * Spiracle (vertebrates), openings on the surface of some vertebrates * Spiraculum, a genus of land snails in family Cyclophoridae Cycl ...

s, part of a gas exchange system that would only work in air. This makes ''P. newmani'' the earliest documented arthropod with a tracheal system, and among the first known oxygen-breathing animal on land. Trace fossils of myriapods are known dating back to the late Ordovician (the geologic period preceding the Silurian), but ''P. newmani'' is the earliest body fossil of a myriapod, and has been dated to between (Silurian, late Wenlock epoch to early Ludlow epoch) and (Early

( Lochkovian)). There are also trigonotarbid and arachnid fossils dating to around this time known from Lludlow in Shropshire, and together these comprise the oldest known air-breathing terrestrial animals. The earliest

centipede Centipedes (from New Latin , "hundred", and Latin , " foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', lip, and New Latin suffix , "foot", describing the forcipules) of the subphylum Myriapoda, an ...

s follow some 10 million years later, and the first known vertebrate on land, '' Tiktaalik'', dates from 50 million years later than ''Pneumodesmus''. During the

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

, 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.

References

{{Taxonbar, from1=Q24521381, from2=Q14302552 Silurian myriapods Prehistoric myriapod genera †Pneumodesmus Paleozoic arthropods of Europe Fossil taxa described in 2004 Fossils of Scotland Stonehaven History of Aberdeenshire Collections of the National Museums of Scotland