Heteronectes
| Heteronectes Temporal range: Middle Eocene | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Pleuronectiformes |
| Genus: | †Heteronectes Friedman, 2008 |
| Species: | †H. chaneti |
| Binomial name | |
| Heteronectes chaneti Friedman, 2008 | |
Heteronectes chaneti is a fossil fish which has been identified as an early relative of the flatfish, and as a transitional fossil. In a typical modern flatfish, the head is asymmetric with both eyes on one side of the head. In Heteronectes, the transition from the typical symmetric head of a vertebrate is incomplete, with one eye positioned near the top of the head, very similar, but less so than its Italian relative, Amphistium.[1][2]
The evolutionary transition from a symmetric position of eyes in many fish to the position of both eyes on the same side of the head in flatfish was cited as a transition difficult to imagine by St. George Jackson Mivart. This was presented as a difficulty for gradual evolution. The discovery, in 2008, of Heteronectes and Amphistium was considered a vindication of the viability of such a transition.[3]
Heteronectes is found in the early to middle Eocene of France.
References
- ↑ Matt Friedman (2008-07-10). "The evolutionary origin of flatfish asymmetry". Nature. 454 (7201): 209–212. PMID 18615083. doi:10.1038/nature07108.
- ↑ Matt Friedman (2012). "Osteology of Heteronectes chantey (Acanthomorpha, Pleuronectiformes), an Eocene stem flatfish, with a discussion of flatfish sister-group relationships". Journal of Vertebrate Paleontology. 21 (4): 735–756. doi:10.1080/02724634.2012.661352.
- ↑ Zimmer, Carl (2008). "The Evolution of Extraordinary Eyes: The Cases of Flatfishes and Stalk-eyed Flies". Evolution Education Outreach. 1: 487. doi:10.1007/s12052-008-0089-9.