A new Middle Jurassic (Bajocian) homolodromioid crab from northwest France; the earliest record of the Tanidromitidae

Resumen

A new homolodromioid,
Tanidromites maerteni, the earliest member of the genus and family,
is recorded from the lower upper Bajocian (Niortense Zone) of
Calvados, northwest France. It is noted that carapace morphologies
of other Jurassic brachyuran taxa within the family Prosopidae are
closely similar to those of tanidromitids, and that diagnoses of
recently erected Jurassic families and genera partially overlap or
have conflict among them. Thus, the taxonomy of the earliest
brachyuran groups appears to be less stable than currently thought.
In recent years, knowledge of primitive extinct brachyurans has
greatly benefitted from findings made by amateur collectors, the
present paper included.