''Acestrus'' is an extinct genus of marine

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

that lived during the lower

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

in Europe. It contains one species, ''A. ornatus'' from the

London Clay The London Clay Formation is a Sediment#Shores and shallow seas, marine formation (geology), geological formation of Ypresian (early Eocene Epoch, c. 54-50 million years ago) age which outcrop, crops out in the southeast of England. The London C ...

, known from a single braincase. It is thought to possibly be closely allied with

billfish The billfish are a group (Xiphioidea) of saltwater fish, saltwater predatory fish characterised by prominent pointed beak, bills (rostrum (anatomy), rostra), and by their large size; some are longer than . Extant billfish include sailfish and m ...

based on the braincase morphology, although it remains uncertain whether it had the rostrum characteristic of billfishes. Some authorities have suggested blochiid affinities. The former species "''A. elongatus''" Casier, 1966 is now thought to be remains assigned to '' Duplexdens''.

References

† A dagger, obelisk, or obelus is a typographical mark that usually indicates a footnote if an asterisk has already been used. The symbol is also used to indicate death (of people) or extinction (of species or languages). It is one of the mo ...

Prehistoric percomorph genera Monotypic prehistoric ray-finned fish genera Eocene fish of Europe Ypresian genera Fossils of England Fossil taxa described in 1901 Taxa named by Arthur Smith Woodward {{Carangiformes-stub