Biology:Eognathacantha
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.[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 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.[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
- ↑ 1.0 1.1 1.2 Chen, Jun-Yuan; Huang, Di-Ying (4 October 2002). "A Possible Lower Cambrian Chaetognath (Arrow Worm)". Science 298 (5591): 187. doi:10.1126/science.1075059. ISSN 0036-8075. https://www.science.org/doi/abs/10.1126/science.1075059.
- ↑ Briggs, Derek E.G.; Caron, Jean-Bernard (21 August 2017). "A Large Cambrian Chaetognath with Supernumerary Grasping Spines". Current Biology 27 (16): 2536-2543.e1. doi:10.1016/j.cub.2017.07.003. ISSN 0960-9822. https://www.cell.com/current-biology/fulltext/S0960-9822(17)30860-6.
- ↑ Casenove, David; Goto, Taichiro; Vannier, Jean (8 April 2016). "Relation between anatomy and lifestyles in Recent and Early Cambrian chaetognaths". Paleobiology 37 (4): 563-576. doi:10.1666/10030.1. ISSN 1938-5331. https://www.cambridge.org/core/journals/paleobiology/article/abs/relation-between-anatomy-and-lifestyles-in-recent-and-early-cambrian-chaetognaths/C9EB2AF699C0D9363F551501BAE6D995.
Wikidata ☰ Q138413163 entry
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