Sous-embranchement (subphylum) des Rhynchonelliformea
Classe des Rhynchonellata
Ordre des Terebratulida
Sous-Ordre des Terebratellidina
Super-famille des Megathyridoidea
Famille des Megathyrididae



Genus Joania Alvarez, Brunton & Long, 2008

[Type-species = Terebratula cordata Risso, 1826 p. 389]

Megathiridid genus with relatively small adult size, outline varying from elongate heart-shaped to rounded subrectangular, with narrow hinge, profile biconvex to ventribiconvex; externally two to four rounded and weakly defined ribs; dorsal interior with strong trifid, short-shafted cardinal process; median septum with tuberculate antero-ventral edge; radial ridges with well defined tubercles submarginally, anterior to weakly defined descending lamellae of brachidium, raised only posteriorly and at edges of median septum.

Eocene - Recent

Diagnosis from Alvarez et al. (2008)

Species of Joania
  • J. cordata (Risso, 1826)
  • J. arguta Grant, 1983

  • Argyrotheca mayi Blochmann, 1914 - perhaps belonging to Joania
  • Argyrotheca anomala Cooper, 1983: Late Eocene - perhaps belonging to Joania

  • Diagnosis

    Joania cordata (Risso, 1826)

    Type locality: off Nizza, Mediterranean coast.
    Depth range: 3 - 600 m

    Terebratula neapolitana Scacchi, 1833
    Orthis neapolitana (Scacchi) : Philippi (1844)
    Argiope neapolitana (Scacchi) : Davidson, 1852)
    Argiope Forbesii (Scacchi) : Davidson (1852)
    Terabratula (Argiope) neapolitana (Scacchi) : Reeve (1861)
    Argiope biplicata Seguenza, 1876
    Argiope kowalevskii Schulgin, 1885
    Cistella neapolitana (Scacchi) : Davidson (1887)
    Argyrotheca cordata (Risso) : Dall (1920)
    Joania cordata (Risso) : Alvarez, Brunton & Long (2008)

    Diagnosis - Risso (1826)

    T. Testa glaberrima, cordata, lucida ; valvis ambabus punctulis albis impressis sculptis ; epidermide fulvescente pellucida.

    Coq. très lisse, cordée, luisante; à valves sculptées de très petits points blancs; l'épiderme est d'un brunâtre translucide. Long. 0,005. Séj. Régions coralligènes. App. Printemps, été.

    Joania arguta (Grant, 1983)

    Type locality: "underside of coral frond from USNM loc. 32014 on the lagoon side of Igurin Island, Enewetak Atoll, depth 14 m".
    Depth range: 14 - 100 m.

    Argyrotheca arguta Grant, 1983, p. 178
    Argyrotheca sp. Cooper, 1954
    Argyrotheca arguta: Alvarez, Brunton & Long (2008)
    ? Argyrotheca sp. Bitner, 2008

    Diagnosis from Simon (2010)

    Shell dorsibiconvex, small, known width less than three mm; white or translucent or light tan most lacking costae; outline variable from subquadrate to heart-shaped, subpentagonal with emarginated anterior margin. Hinge line straight, nanower than the shell. Ventral valve with a microtuberculate external shell surface. Ventral valve with apical angle around 124°-131°; large pedicle collar; robust teeth given offdorsally; low blade-like ventral median septum; valve floor with radial ridges terminating in tubercles near the anterior margin. Dorsal valve with median sulcus producing a slightly sulcate anterior commissure; strong, deep sockets with elevated inner socket ridges; complex strong cardinal process; strong triangular senate dorsal septum; valve floor with radial ridges terminating in marginal tubercles; loop circling laterally with short pointed crural processes, descending branches weakly defined fused rapidly with valve floor and attached to lateral sides of dorsal septum. Shell coarsely punctate with 250/280 punctae/mm2.