{{Short description|Cambrian genus of chaetognath}} {{Speciesbox | fossil_range = [[Moscovian age|Moscovian]], <br>~{{fossil_range|311|307|ref=<ref name=Allison1987>{{cite journal |author=P. A. Allison |year=1987 |title=A new cephalopod with soft parts from the Upper Carboniferous Francis Creek Shale of Illinois, USA |journal=[[Lethaia]] |volume=20 |issue=78 |pages=117–121 |doi=10.1111/j.1502-3931.1987.tb02028.x}}</ref> }} | image = Paucijaculum samamithion Mazon Creek Pit 11.webp | image_caption = ''Paucijaculum samamithion'' specimen from Mazon Creek Pit 11 | genus = Paucijaculum | parent_authority = Schram, 1973 | species = samamithion | authority = [[Frederick Schram|Schram]], 1973 }}
'''''Paucijaculum''''' is an extinct genus of [[chaetognath]] from the [[Carboniferous]] age [[Mazon Creek fossil beds|Francis Creek Shale]] and [[Carbondale Group]] of [[Illinois]], United States.<ref>{{Cite web |title=''Paucijaculum'' Schram, 1973 |url=https://www.gbif.org/species/4632577 |access-date=9 February 2026 |website=GBIF}}</ref> It contains one species, '''''Paucijaculum samamithion'''''.
== Discovery and naming == The holotype is '''FMNH PE116''' and it was discovered no later than 1972 inside an [[ironstone]] concretion at Pit 11 at Mazon Creek.<ref name=":0">F. R. Schram. (1973). Pseudocoelomates and a nemertine from the Illinois Pennsylvanian. ''Journal of Paleontology'' 47:985-989</ref> [[Frederick Schram|Schram]] (1973) named and described ''Paucijaculum samamithion'' as the oldest known and first known fossil chaetognath;<ref name=":0" /> this was accepted until ''[[Eognathacantha]]'' was identified from the [[Cambrian Stage 3]] in [[China]].<ref>{{Cite journal |last=Chen |first=Jun-Yuan |last2=Huang |first2=Di-Ying |date=2002-10-04 |title=A Possible Lower Cambrian Chaetognath (Arrow Worm) |url=https://doi.org/10.1126/science.1075059 |journal=Science |volume=298 |issue=5591 |pages=187–187 |doi=10.1126/science.1075059 |issn=0036-8075|url-access=subscription }}</ref>
Additional specimens have been found in the [[Carbondale Group]] near [[Essex, Illinois]].<ref>{{Cite web |title=1" Fossil Arrow Worm (''Paucijaculum'') Pos/Neg- Illinois |url=https://www.fossilera.com/fossils/1-0-fossil-arrow-worms-paucijaculum-pos-neg-illinois?srsltid=AfmBOop8lubm__iJ42v63zvqBAk03WtqwRphStQ0W1FZXtlyomeUMZsv |access-date=11 February 2026 |website=FossilEra}}</ref>
== Description == [[File:Paucijaculum_samamithion_tail_fin.png|left|thumb|200x200px|Closeup of the rounded tail fin of ''Paucijaculum samamithion'']] ''Paucijaculum'' grew up to {{Convert|3|cm|in}} long and had incipiently developed fins alongside a circular tail fin.<ref name=":0" />
Most specimens are poorly preserved and lack detail.<ref name=":0" />
== References == {{reflist}}
{{Taxonbar|from=Q138108412}}
[[Category:Carboniferous invertebrates]] [[Category:Fossils of the United States]] [[Category:Pennsylvanian animals of North America]] [[Category:Chaetognatha]] [[Category:Fossil taxa described in 1973]] [[Category:Carboniferous genus extinctions]] [[Category:Prehistoric animal genera]]