# Eognathacantha

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Extinct genus of arrow worm

Eognathacantha Temporal range: Cambrian Stage 3 PreꞒ Ꞓ O S D C P T J K Pg N Scientific classification Kingdom: Animalia Clade: Spiralia Clade: Gnathifera Clade: Cucullophora Phylum: Chaetognatha Genus: †Eognathacantha Chen & Huang, 2002 Species: †E. ercainella Binomial name †Eognathacantha ercainella Chen & Huang, 2002

***Eognathacantha*** is an extinct genus of [chaetognath](/source/Chaetognath) from the [Maotianshan Shales](/source/Maotianshan_Shales) in southern [China](/source/China). It lived around 520 Ma, during the Cambrian [stage 3](/source/Stage_3). It is the oldest known chaetognath.[1] 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](/source/Maotianshan_Shales) [Lagerstätte](/source/Lagerst%C3%A4tte) near Ercain village, near [Kunming](/source/Kunming) in southern [China](/source/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.[1]

## Description

The specimen measures 25 mm (1.0 in) in length. The head is 2.8 mm (0.11 in) wide. The head carries about 12 slightly curved grasping spines, 6 on each side,[2] 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 2.5 mm (0.10 in) wide, an 8 mm (0.3 in) 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.[1]

A biomechanical study comparing *Eognathacantha* with modern chaetognaths has confirmed that *Eognathacantha* was pelagic.[3]

## References

1. ^ [***a***](#cite_ref-Chen2002_1-0) [***b***](#cite_ref-Chen2002_1-1) [***c***](#cite_ref-Chen2002_1-2) Chen, Jun-Yuan; Huang, Di-Ying (4 October 2002). ["A Possible Lower Cambrian Chaetognath (Arrow Worm)"](https://www.science.org/doi/abs/10.1126/science.1075059). *Science*. **298** (5591): 187. [doi](/source/Doi_(identifier)):[10.1126/science.1075059](https://doi.org/10.1126%2Fscience.1075059). [ISSN](/source/ISSN_(identifier)) [0036-8075](https://search.worldcat.org/issn/0036-8075).

1. **[^](#cite_ref-2)** Briggs, Derek E.G.; Caron, Jean-Bernard (21 August 2017). ["A Large Cambrian Chaetognath with Supernumerary Grasping Spines"](https://www.cell.com/current-biology/fulltext/S0960-9822(17)30860-6). *Current Biology*. **27** (16): 2536-2543.e1. [doi](/source/Doi_(identifier)):[10.1016/j.cub.2017.07.003](https://doi.org/10.1016%2Fj.cub.2017.07.003). [ISSN](/source/ISSN_(identifier)) [0960-9822](https://search.worldcat.org/issn/0960-9822).

1. **[^](#cite_ref-3)** Casenove, David; Goto, Taichiro; Vannier, Jean (8 April 2016). ["Relation between anatomy and lifestyles in Recent and Early Cambrian chaetognaths"](https://www.cambridge.org/core/journals/paleobiology/article/abs/relation-between-anatomy-and-lifestyles-in-recent-and-early-cambrian-chaetognaths/C9EB2AF699C0D9363F551501BAE6D995). *Paleobiology*. **37** (4): 563–576. [doi](/source/Doi_(identifier)):[10.1666/10030.1](https://doi.org/10.1666%2F10030.1). [ISSN](/source/ISSN_(identifier)) [1938-5331](https://search.worldcat.org/issn/1938-5331).

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Adapted from the Wikipedia article [Eognathacantha](https://en.wikipedia.org/wiki/Eognathacantha) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Eognathacantha?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.