Eognathacantha

{{Speciesbox | fossil_range = {{fossilrange|Cambrian Stage 3}} | genus = Eognathacantha | parent_authority = Chen & Huang, 2002 | species = ercainella | display_parents = 5 | authority = Chen & Huang, 2002 }}

'''''Eognathacantha''''' is an extinct genus of [[chaetognath]] from the [[Maotianshan Shales]] in southern [[China]]. It lived around 520 Ma, during the Cambrian [[stage 3]]. It is the oldest known chaetognath.<ref name="Chen2002">{{Cite journal |last1=Chen |first1=Jun-Yuan |last2=Huang |first2=Di-Ying |date=4 October 2002 |title=A Possible Lower Cambrian Chaetognath (Arrow Worm) |url=https://www.science.org/doi/abs/10.1126/science.1075059 |journal=Science |volume=298 |issue=5591 |pages=187 |doi=10.1126/science.1075059 |issn=0036-8075|url-access=subscription }}</ref> The only known species is '''''Eognathacantha ercainella'''''.

== Discovery and naming == It is only known from the holotype specimen ECO2001a and its counterpart ECO1001b found in the [[Maotianshan Shales]] [[Lagerstätte]] near Ercain village, near [[Kunming]] in southern [[China]]. The specimen is complete. It was named by Chen & Huang. The genus name probably comes from the Greek ''ēōs'', meaning "dawn", ''gnathos'', meaning "jaw" and ''akantha'', meaning "spine". The species name might be derived from Ercai village near the site of the discovery. However, the etymology is not explicitly explained by the authors.<ref name="Chen2002"/>

== Description == The specimen measures {{cvt|25|mm|1}} in length. The head is {{cvt|2.8|mm}} wide. The head carries about 12 slightly curved grasping spines, 6 on each side,<ref>{{Cite journal |last1=Briggs |first1=Derek E.G. |last2=Caron |first2=Jean-Bernard |date=21 August 2017 |title=A Large Cambrian Chaetognath with Supernumerary Grasping Spines |url=https://www.cell.com/current-biology/fulltext/S0960-9822(17)30860-6 |journal=Current Biology |volume=27 |issue=16 |pages=2536-2543.e1 |doi=10.1016/j.cub.2017.07.003 |issn=0960-9822}}</ref> each about 900 µm long. In the anterior part of the head, there are numerous spines which might be teeth ranging from 200 µm to 250 µm long. Possible muscle marks are found on the head. The body is {{cvt|2.5|mm|2}} wide, an {{cvt|8|mm|1}} long tail is distinguishable from the rest of the body. The trunk and the tail carry a pair of fins. The body appears to show the pharynx, the intestine and possibly the anus.<ref name="Chen2002"/>

A biomechanical study comparing ''Eognathacantha'' with modern chaetognaths has confirmed that ''Eognathacantha'' was pelagic.<ref>{{Cite journal |last1=Casenove |first1=David |last2=Goto |first2=Taichiro |last3=Vannier |first3=Jean |date=8 April 2016 |title=Relation between anatomy and lifestyles in Recent and Early Cambrian chaetognaths |url=https://www.cambridge.org/core/journals/paleobiology/article/abs/relation-between-anatomy-and-lifestyles-in-recent-and-early-cambrian-chaetognaths/C9EB2AF699C0D9363F551501BAE6D995 |journal=Paleobiology |volume=37 |issue=4 |pages=563-576 |doi=10.1666/10030.1 |issn=1938-5331|url-access=subscription }}</ref>

== References == {{reflist}}

[[Category:Chaetognatha]] [[Category:Fossil taxa described in 2002]] [[Category:Cambrian invertebrates]] [[Category:Maotianshan shales fossils]]