Heteronectes

• Bolca, Northern Italy

Heteronectes chaneti is a 47- million year old fossil species from the order of flatfish, which was designated the occasion of their first description as "the most primitive known flatfish ." That one eye of the animal is at the usual for fish lateral position, the other eye, however, on the opposite side of the head more than the usual in fish position, immediately adjacent to the Dorsallinie ( center back ) as a mosaic form takes this type -. together with comparable ancient representatives of the genus Amphistium - an intermediate position between the bilaterally symmetrical fish and flatfish one.

Description of the findings

Heteronectes chaneti had a very narrow body with a high in proportion to the length of body and disc on the abdomen and back quite a long Flossensaum. The most prominent anatomical feature of about 11 cm long Fossils the pronounced asymmetry of the head was in the original description emerged, particularly in the area of the bony orbits, is the natural origin and not a consequence of deformation during fossilization. Thus corresponds to the positional relationship of the front face to the back of the head of the fish - apart from the position of the one eye - and the head to the rest of the body in the usual proportions fish. Also be inferred from the degree of ossification of the skull, the position of the eyes of an adult fish of its kind correspond. At the same time the fins are different - especially the dorsal and anal fins - the type specimen for the genus and species in strength and number and arrangement of the beams from the two known fossil species of the genus Amphistium.

The generic name is derived from the Greek words heteros ( = different) and Netri ( = float ), the type - epithet was chosen in honor of Bruno Chanet, who has made ​​outstanding contributions to the study of fossil flatfish. The type specimen is kept 1974.1639.25 ( plate and counter plate ) at the Natural History Museum of Vienna under the archive numbers NHMW 1974.1639.24 and NHMW.

Significance of the find

Heteronectes chaneti fills a comment in According to New Scientist, " a gap in the sequence documented fossil record, which has since Darwin's day beset the theory of evolution. " This has been repeatedly argued by critics of the theory of evolution, both an upright swimming fish with both sides symmetrically arranged eyes as also a fluke was purpose-built as a variant of the advantages of swimming in clear water, the other on the other hand brings benefits when staying on the ground with it. An intermediate form, however, do not have a discernible advantage, which is why natural selection is unlikely that could continue to develop a "normal" fish a fluke. Only the fossils described in 2008 definitively disproved this objection. The journal Nature commented that the discovery of the fossil "shows that the evolution of flatfish actually took place gradually, and it helps that a popular among creationists example to rest can be laid. "

According Erstbeschreiber Matt Friedman of the University of Chicago to Heteronectes has chaneti probably - having regard to the pectoral fin of the side of the body towards the back with the offset eye - obliquely placed on the seabed and there waylaid potential prey.