Extinct genus of fishes
Coccocephalus is an extinct genus of prehistoric freshwater and marine basal ray-finned fish from the Carboniferous to the early Permian period. The type species, "C. wildi", lived during the Bashkirian age of the Pennsylvanian epoch in what is now Lancashire, United Kingdom. One specimen of "C. wildi" is notable for having the earliest known instance of fossilized brain tissue in a vertebrate.
Taxonomy.
The type species was first described as "Coccocephalus wildi" in 1925 by David Meredith Seares Watson, but because "Coccocephalus" was thought to be preoccupied (for an extant hemipteran insect), both Gilbert Percy Whitley and Errol White &amp; James Alan Moy-Thomas proposed a new genus name in 1940. Because the article introducing the name "Coccocephalichthys" was published before the article erecting the name "Cocconiscus" , the former became the valid new genus name for the Carboniferous fish for some time. However, reexamination of Fieber's 1861 insect publication in 1996 revealed that the insect in question is "Coccodocephalus", thus the original name "Coccocephalus wildi" stands as the correct name for this genus and both "Coccocephalichthys" and "Cocconiscus" are junior synonyms. 
"Coccocephalus" is suggested to belong to the stem-group of Actinopterygii, with all living ray-finned fish more closely related to each other than to "Coccocephalus".
Ecology &amp; evolution.
In 2023, the type specimen of "C. wildi" was found to preserve the earliest example of fossilized brain and nerve tissue. The fossil shows that the forebrain in this ray-finned fish was evaginated, a feature otherwise not known in actinopterygians. The results show that the everted forebrain of modern ray-fins evolved later than previously thought. The exceptional preservation of this specimen likely occurred due to the individual being rapidly buried in a low-oxygen environment after death, preventing decomposition of the brain tissue.
References.
 ;templatestyles src="Reflist/styles.css" / ;