Pneumodesmus
{{Short description|Genus of millipedes}}
{{Use dmy dates|date=April 2022}}
{{Speciesbox
| image = Pneumodesmus newmani - MUSE.JPG
| image_caption = Reconstruction of P. newmani
| image2 = Pneumodesmus_newmani.jpg
| image2_caption = Photomicrograph of the type specimen
| fossil_range = {{Fossil range|428|414|Wenlock/Lochkovian}}
| genus = Pneumodesmus
| species = newmani
| authority = Wilson & Anderson, 2004 {{cite journal |journal=Journal of Paleontology |year=2004 |volume=78 |issue=1 |pages=169–184 |title=Morphology and taxonomy of Paleozoic millipedes (Diplopoda: Chilognatha: Archipolypoda) from Scotland |author=Heather M. Wilson & Lyall I. Anderson |url=https://www.researchgate.net/publication/250070300 |doi=10.1666/0022-3360(2004)078<0169:MATOPM>2.0.CO;2}}
}}
Pneumodesmus newmani is a species of myriapod. It is originally considered that it lived during the late Wenlock epoch of the Silurian period around {{Ma|428}}.{{cite news |publisher=BBC News |date=January 25, 2004 |url=http://news.bbc.co.uk/2/hi/uk_news/scotland/3427499.stm |title=Fossil find 'oldest land animal' |archive-url=https://web.archive.org/web/20230818174604/http://news.bbc.co.uk/2/hi/uk_news/scotland/3427499.stm |archive-date=2023-08-18 |url-status=live}} However, a 2017 study dates its occurrence based on zircon data analysis as the Early Devonian (Lochkovian).{{Cite journal|author1=Stephanie E. Suarez |author2=Michael E. Brookfield |author3=Elizabeth J. Catlos |author4=Daniel F. Stöckli |year=2017 |title=A U-Pb zircon age constraint on the oldest-recorded air-breathing land animal |journal=PLOS ONE |volume=12 |issue=6 |pages=e0179262 |doi=10.1371/journal.pone.0179262 |pmc=5489152 |pmid=28658320 |bibcode=2017PLoSO..1279262S |doi-access=free }} Although the 2023 study confirmed the age identification of the 2004 study through palynological, palaeobotanical and zircon analyses incorporating newly discovered additional data,{{cite journal|first1=C.H.|last1=Wellman|first2=G.|last2=Lopes|first3=Z.|last3=McKellar|first4=A.|last4=Hartley|year=2023|title=Age of the basal ‘Lower Old Red Sandstone’ Stonehaven Group of Scotland: The oldest reported air-breathing land animal is Silurian (late Wenlock) in age|journal=Journal of the Geological Society|publisher=The Geological Society of London|doi=10.1144/jgs2023-138|issn=0016-7649|doi-access=free|hdl=2164/22754|hdl-access=free}} this is based on adjacent structurally separated block with different stratigraphy and sedimentology to the block with fossil site it was discovered, and it is confirmed as unsustainable.{{Cite journal |last=Brookfield |first=M. E. |last2=Catlos |first2=E. J. |last3=Garza |first3=H. |date=2024-07-07 |title=The oldest ‘millipede’-plant association? Age, paleoenvironments and sources of the Silurian lake sediments at Kerrera, Argyll and Bute, Scotland |url=https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2367554 |journal=Historical Biology |language=en |pages=1–13 |doi=10.1080/08912963.2024.2367554 |issn=0891-2963|url-access=subscription }} It is one of the first myriapods, and among the oldest creatures to have lived on land.{{cite news |url=http://edition.cnn.com/2004/TECH/science/01/27/environment.britain.fossil.reut/index.html |title=Fossil millipede found to be oldest land creature |publisher=CNN (from Reuters) |date=January 27, 2004}} It was discovered in 2004, and is known from a single specimen from Stonehaven, Aberdeenshire, 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 (Cowie Formation).{{cite web |title=Pneumodesmus newmani Exhibition |url=http://www.stonehavenguide.net/prods/fossil-over-420-million-years-old.html |publisher=Stonehaven Guide |accessdate=Oct 22, 2013 |archive-url=https://web.archive.org/web/20161224094410/http://www.stonehavenguide.net/prods/fossil-over-420-million-years-old.html |archive-date=December 24, 2016 |url-status=dead }} The species was later given the specific epithet "newmani" in honour of Newman. The holotype is kept in National Museum of Scotland, Edinburgh.{{cite journal |url=http://www.paulselden.net/uploads/7/5/3/2/7532217/seldenread2008.pdf |journal=Bulletin of the British Myriapod & Isopod Group |volume=23 |year=2008 |title=The oldest land animals: Silurian millipedes from Scotland |author=Paul Selden & Helen Read |pages=36–37 |archive-url=https://web.archive.org/web/20240306033234/http://www.paulselden.net/uploads/7/5/3/2/7532217/seldenread2008.pdf |archive-date=2024-03-06 |url-status=dead}} The genus name is said to be 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).Liddell, H.G. & Scott, R. (1940). A Greek-English Lexicon. Revised and augmented throughout by Sir Henry Stuart Jones. With the assistance of Roderick McKenzie. Oxford: Clarendon Press.
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 spiracles, 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.{{cite web |url=http://www.myriapoda.org/diplopoda/millipede_fossils.html |title=Millipede Fossils |publisher=East Carolina University |date=March 1, 2005 |author=Rowland Shelley & Paul Marek |archiveurl=https://web.archive.org/web/20110527071726/http://www.myriapoda.org/diplopoda/millipede_fossils.html |archivedate=May 27, 2011 |url-status=usurped}}
Trace fossils of myriapods are known dating back to the late Ordovician (the geologic period preceding the Silurian), but P. newmani may be the earliest body fossil of a myriapod, if it had been dated at {{Ma|428}} (Silurian, late Wenlock epoch to early Ludlow epoch). However, if based on {{Ma|414}} (Early Devonian (Lochkovian)) estimated from Zircon age estimate, it cannot be called as the oldest myriapod, or the oldest of air-breathing terrestrial arthropods, because records from Kerrera (425 millions years ago) and Ludlow (420 millions years ago) become older than that.{{Cite journal |last=Brookfield |first=M. E. |last2=Catlos |first2=E. J. |last3=Suarez |first3=S. E. |date=2021-10-03 |title=Myriapod divergence times differ between molecular clock and fossil evidence: U/Pb zircon ages of the earliest fossil millipede-bearing sediments and their significance |url=https://www.tandfonline.com/doi/full/10.1080/08912963.2020.1762593 |journal=Historical Biology |language=en |volume=33 |issue=10 |pages=2014–2018 |doi=10.1080/08912963.2020.1762593 |issn=0891-2963|url-access=subscription }} In spite of the recent competing arguments, the 2023 study suggests that this taxon is still most likely the earliest body fossil of a myriapod, with its age reconfirmed as the late Wenlock epoch (around {{Ma|430}}) through various analyses. 2024 study doubts that conclusion however, because this analyses are not based on fossil-bearing sediment itself.
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.{{cite web |url=http://www.bbc.co.uk/scotland/whereilive/coast/stages.shtml?walk=northeast&stage=2 |publisher=BBC Scotland |title=Cowie |accessdate=2024-03-23 |archive-url=https://web.archive.org/web/20220929120239/https://www.bbc.co.uk/scotland/whereilive/coast/stages.shtml?walk=northeast&stage=2 |archive-date=2022-09-29 |url-status=dead}}
References
{{Reflist|32em}}
{{Taxonbar|from1=Q24521381|from2=Q14302552}}
Category:Prehistoric myriapod genera
Category:Paleozoic arthropods of Europe
Category:Fossil taxa described in 2004