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Type species: Jaffaia jaffaensis (Blochmann, 1910).
Diagnosis: Moderately large, ovoid to circular in outline; lateral commissure near straight, anterior commissure rectimarginate to lightly sulcate. Beak suberect; deltidial plates conjunct as symphytium, mostly exposed; foramen small, subapical, submesothyridid (or mesothyridid), attrite (beak ridges indistinct); hinge teeth large relative to symphytium, with swollen bases, dental plates absent; pedicle collar very short. Cardinalia lamellar, excavate inner and outer hinge plates separated by relatively thick crural bases, inner hinge plates form V-shaped septalium supported by median septum, inner socket ridges lightly inclined; cardinal process well-developed, supported anteriorly by a triangular ridge between the hinge plates, posteriorly facing myophore rounded to sub-pentagonal; median septum not reaching mid-valve, highest at junction with lateral connecting bands; crura short, subparallel, crural processes short and pointed. Adult brachial loop trabecular; lophophore plectolophous.
Genus description: As per diagnosis.
Remarks: Monotypic genus. Possibly synonymous with genus Nipponithyris Yabe & Hatai, 1934, per discussion section.