Pneumodesmus

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Pneumodesmus
Temporal range: Late Silurian
Pneumodesmus newmani.jpg
Photomicrograph of the type specimen
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Myriapoda
Class: Diplopoda
Subclass: Archipolypoda
Order: Incertae sedis
Family: Incertae sedis
Genus: Pneumodesmus
Species: P. newmani
Binomial name
Pneumodesmus newmani
Wilson & Anderson, 2004 [1]

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]

Discovery[edit]

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 genus name derives from the Greek pneumato ("air" or "breath") and desmus ("band", a common millipede root word) in reference to the inferred air-breathing habit.[1]

Description[edit]

The fossil of P. newmani depicts small paranota (keels) high on the body, long, slender legs. The dorsal portion of each body segment is ornamented with a horizontal bar and three rows of roughly hexagonal bosses (bumps).[1]

Significance[edit]

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 indeed the first known oxygen-breathing animal on land.[3][6]

Ichnofossils of myriapods are known dating back to the late Ordovician,[1] 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]

References[edit]

  1. ^ a b c d e Heather M. Wilson & Lyall I. Anderson (2004). "Morphology and taxonomy of Paleozoic millipedes (Diplopoda: Chilognatha: Archipolypoda) from Scotland". Journal of Paleontology 78 (1): 169–184. doi:10.1666/0022-3360(2004)078<0169:MATOPM>2.0.CO;2. 
  2. ^ a b "Fossil find 'oldest land animal'". BBC News. January 25, 2004. 
  3. ^ a b "Fossil millipede found to be oldest land creature". CNN (from Reuters). January 27, 2004. 
  4. ^ "Pneumodesmus newmani Exhibition". Stonehaven Guide. Retrieved Oct 22, 2013. 
  5. ^ Paul Selden & Helen Read (2008). "The oldest land animals: Silurian millipedes from Scotland". Bulletin of the British Myriapod & Isopod Group 23: 36–37. 
  6. ^ a b Rowland Shelley & Paul Marek (March 1, 2005). "Millipede Fossils". East Carolina University. Archived from the original on May 27, 2011. 
  7. ^ David Winter (April 9, 2006). "When animals first conquered the land". Science and sensibility. 
  8. ^ "Cowie". BBC Scotland. Retrieved May 6, 2007.