Parioscorpio

Parioscorpio; Temporal range: Silurian, (Telychian) 437.5–436.5 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Chelicerata
Class:	Arachnida
Order:	Scorpiones
Genus:	†Parioscorpio; Wendruff et al, 2020
Type species
	†Parioscorpio venator; Wendruff et al, 2020

Parioscorpio is an extinct genus of scorpion containing the species P. venator known from the Silurian aged Waukesha Biota of the Brandon Bridge Formation near Waukesha, Wisconsin. It is currently the world's oldest and basalmost known scorpion, older than Dolichophonus from Scotland by several million years. The fossils were originally discovered in 1985 but were neglected for decades. It is known from two specimens which preserve parts of the pulmonary, cardiovascular and digestive systems.

Closeup of the pulmonary-cardiovascular system in Parioscorpio (left) with that of contemporary scorpions (centre,right)

Description

Reconstruction, showing internal pulmonary-cardiovascular system

The animal is around 2.5 centimetres long, It is characterized by a trapezoidal prosoma with large eyes located antero-laterally, and large pedipalps. Its mesosoma is much longer than the metasoma, it shows a record 7 tergites and 7 sternites. The 7 tergites is the highest known being progressively reduced in number in later stem-scorpions.

Paleoenvironment

How terrestrial the organism was is uncertain, as it was found in a shallow marine deposit, but it could have been transported into the environment from terrestrial sources.[1]

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References

Wendruff, Andrew J.; Babcock, Loren E.; Wirkner, Christian S.; Kluessendorf, Joanne; Mikulic, Donald G. (December 2020). "A Silurian ancestral scorpion with fossilised internal anatomy illustrating a pathway to arachnid terrestrialisation". Scientific Reports. 10 (1): 14. doi:10.1038/s41598-019-56010-z. ISSN 2045-2322. PMID 31949185.

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[1] Wendruff, Andrew J.; Babcock, Loren E.; Wirkner, Christian S.; Kluessendorf, Joanne; Mikulic, Donald G. (December 2020). "A Silurian ancestral scorpion with fossilised internal anatomy illustrating a pathway to arachnid terrestrialisation". Scientific Reports. 10 (1): 14. doi:10.1038/s41598-019-56010-z. ISSN 2045-2322. PMID 31949185.