''Leptaena'' is an
extinct genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...
of mid-sized
brachiopod
Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, ...
that existed from the
Dariwilian epoch to the
Emsian epoch,
though some specimens have been found in
strata
In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as e ...
as late in age as the
Tournasian epoch.
[epifaunal
Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is ''flora'', and for fungi, it is ''funga''. Flora, fauna, funga and other forms of life are collectively referred to as ''biota''. Zoolo ...]
.
''Leptaena'' usually have concentric wrinkling and concentric lines on the shell. ''Leptaena'' have a concavo-convex profile, and are sometimes Semiquadrate to semielliptical. The Cardinal Process is split in two and the hinge line is straight.
.