Eocarcinus praecursor is a Jurassic species of Decapoda crustacean, sufficiently distinct from its relatives to be placed in its own family ( Eocarcinidae).
Distribution
It lived during the early
Pliensbachian age (
Lower Jurassic),
and has been found in rocks at two sites in the
United Kingdom –
Mickelton Tunnel (near
Aston Magna),
Gloucestershire and
Runswick Bay,
Yorkshire.
Description
In many of its characters, it represents a transitional stage between the
Glypheoidea and the
Middle Jurassic crabs in the
Prosopidae.
Since its ancestors were long-tailed
decapoda, and its successors were short-tailed crabs,
Eocarcinus has been described as "the lobster who decided to become a crab".
[ JSTOR: 1st page, 2nd page] Previously considered to be the oldest known true
crab, a 2010 revision concluded that
Eocarcinus could not be accommodated among the Brachyura, and was instead transferred to the
Anomura.
However, a 2020 reanalysis found that it was again the earliest known stem-group crab, but that it had not undergone the process of
carcinisation.
