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Amphithyris

Sous-embranchement (subphylum) des Rhynchonelliformea
Classe des Rhynchonellata
Ordre des Terebratulida
Sous-Ordre des Terebratellidina
Super-famille des Platidioidea

 
 
 
 
 


Genus Amphithyris Thomson, 1918


[Type species= Amphithyris buckmani Thomson, 1918 (p. 20)]

Small shell (up to 5mm), planoconvex to biconvex, punctate, round to oval; shell outline variable depending on substrate of attachment. Ventral valve convex; dorsal valve slightly convex to almost flat; short pedicle; beak apicate; foramen amphithyrid; schizolophous lophophore. Hinge line nearly straight; triangular delthyrium; dental plates absent.

Present

Diagnosis from Nauendorf et al. (2014)

Extant Species of Amphithyris
  • A. buckmanni Thomson, 1918
  • A. seminula (Philippi, 1836)
  • A. hallettensis Foster, 1974
  • A. richardsonae Campbell & Fleming, 1981
  • A. parva Mackinnon, Hiller, Long & Marshall, 2008
  • A. comitodentis Nauendorf, Wörheide & Lüter, 2014
  • A. cavernicola Nauendorf, Wörheide & Lüter, 2014
  • Diagnosis
    Diagnosis
    Diagnosis
    Diagnosis
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    Diagnosis



    Amphithyris buckmani   Thomson, 1918

    Type locality: Cook Strait, off Wellington, New Zealand.
    Depth range: 91 - 963 m

    Diagnosis



    Amphithyris seminula   (Philippi, 1836)

    Type locality: Trapani, Sicily, Mediterranean Sea
    Depth range: -

    Terebratula seminulum Philippi, 1836 : p. 97
    Orthis neapolitana : Philippi (1844)
    Orthis anomioides : Philippi (1844)
    Orthis neapolitana : Costa(1852)
    Morrisia seminulum : Davidson (1852)
    Platydia anomioides : Davidson (1887)
    Platidia seminulum : de Monterosato (1879), Fischer & Œhlert (1891), Dall (1920)
    Amphithyris seminula: Thomson (1927), MacKinnon et al. (2008), Nauendorf et al. (2014).

    Diagnosis (Nauendorf et al., 2014)

    Shell planoconvex, flat dorsal valve with low median septum. Capillae absent.
    The occurrence of Amphithyris needs to be confirmed.

    Amphithyris is a South Pacific genus which had never been recorded in the Mediterranean Sea (considered as type locality of A. seminula). That is really surprising because this sea is probably the best known in brachiopod distribution, at least the Western Mediterranean Basin.

    As the specimens represented by various authors appear to be Amphithyris, the question is where the seminula specimens have been really sampled - thus confirmation with samples of alive specimens is need in the Mediterranean Sea.


    Amphithyris hallettensis Foster, 1974

    Type locality: “Deep Freeze III, USS Atka station 23, near Cape Hallet (72°05.8'S, 172°15.2'E), 392 m; January 8, 1958.”
    Depth range: 348 - 891 m

    Diagnosis (Nauendorf et al., 2014)

    Shell ventribiconvex, small dorsal septum, imprints of capillae visible in ventral valve interior.

    Amphithyris richardsonae   Campbell & Fleming, 1981

    Type locality: upper end of the Narrows, Long Sound (Preservation Inlet, New Zealand)
    Depth range: 74 - 385 m

    Diagnosis (Nauendorf et al., 2014)

    Wide, oval shell, with correspondingly wide foramen. Dorsal valve flat and closely adherent over its whole area to the substrate (Campbell & Fleming 1981). Foramen amphithyrid, with an obtusely triangular delthyrium, no deltidial plates visible.

    Amphithyris parva MacKinnon, Hiller, Long & Marshall, 2008

    Type locality: Cook Strait, near Wellington (New Zealand) - 220 m
    Depth range: 220 m

    Diagnosis (Nauendorf et al., 2014)

    Dorsibiconvex shell, weak capillae on dorsal valve exterior and ventral valve exterior. Dorsal median septum absent.

    Amphithyris comitodentis   Nauendorf, Wörheide & Lüter, 2014

    Type locality: Hikurangi Plateau : st. 105, Cruise SO168 Zealandia (R/V Sonne) - 44º36.21'S, 174°14.77'E, 719m to 44º36.32'S, 174º14.80'E, 597m - [from personal comm. of C. Lüter, sept. 2014]
    Depth range: 252 - 1865 m

    Diagnosis (Nauendorf et al., 2014)

    Shell planoconvex, flat dorsal valve, prints of capillae on ventral valve interior. Hinge teeth flat, narrow, parallel to hinge line. Small dorsal septum.

    Amphithyris cavernicola   Nauendorf, Wörheide & Lüter, 2014

    Type locality: Holmes Reefs, Queensland (Australia) - from cave ceiling, at -8m
    Depth range: 8 m

    Diagnosis (Nauendorf et al., 2014)

    Dorsal septum absent. Ventral valve with low median septum and muscle impressions visible on each side, exterior surface with tubercles and capillae.