''Pachythrissops'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus of ray-finned fish. It contains two species, ''P. laevis'' from the

Purbeckian The Purbeck Group is an Upper Jurassic to Lower Cretaceous lithostratigraphic group (a sequence of rock strata) in south-east England. The name is derived from the district known as the Isle of Purbeck in Dorset where the strata are exposed in the ...

of England and ''P. propterus'' from the

Tithonian In the geological timescale, the Tithonian is the latest age of the Late Jurassic Epoch and the uppermost stage of the Upper Jurassic Series. It spans the time between 152.1 ± 4 Ma and 145.0 ± 4 Ma (million years ago). It is preceded by the K ...

of Germany. A third species, ''P. vectensis'', has been reassigned to the elopiform genus '' Arratiaelops''. ''Pachythrissops'' is often regarded as one of the most primitive members of the order

Ichthyodectiformes Ichthyodectiformes is an extinct order of marine stem-teleost ray-finned fish. The order is named after the genus '' Ichthyodectes'', established by Edward Drinker Cope in 1870. Ichthyodectiforms are usually considered to be some of the closest ...

; however, a phylogenetic analysis by Cavin ''et al.'' (2013) placed it and the related genus '' Ascalabothrissops'' outside the group.

Sources

* ''Fossils'' (Smithsonian Handbooks) by David Ward (Page 215) Ichthyodectiformes Prehistoric ray-finned fish genera Tithonian genera Berriasian genera Jurassic bony fish Late Jurassic fish of Europe Jurassic England Cretaceous England Fossils of England Jurassic Germany Fossils of Germany Fossil taxa described in 1919 Taxa named by Arthur Smith Woodward {{Jurassic-fish-stub