Br@chNet
Dignomia

Sous-embranchement (subphylum) des Linguliformea
Classe des Lingulata
Ordre des Lingulida
Super-famille des Linguloidea
Famille des Lingulidae
 
 
 
 
 


Genus Dignomia Hall, 1871
 
[Type-species = Lingula alveata]

Shell thin, elongate oval in shape; externally, two diverging medio-lateral grooves (internally ridges) extend from the umbonal region to the anterior margin, and a narrow median groove (a septum internally) extends from the umbonal region to the anterior margin of the dorsal valve but in the ventral valve only over the anterior half of the shell.

Asymmetrical muscle system with three internal oblique muscles; unpaired posterior adductor muscle; no vascula media observed. (Note: these three characters are prerequisite to a diagnosis of the Family Lingulidae – see Emig 2003).

Middle Ordovician to Middle Devonian

Occurrences: North and South America.

Diagnosis from Emig & Herrera (2006)


Species of Dignomia

  • D. alveata  (Hall, 1863)

  • D. lepta  (Clarke, 1912)

  • D. munsterii  (d'Orbigny, 1842)

  • ? D. submarginata  (d'Orbigny, 1850)

  • ? D. lineata  (Steinman & Hoek, 1912)


  • The references for this page are:

    • Emig C. C., 2003. Proof that Lingula (Brachiopoda) is not a living-fossil, and emended diagnoses of the Family Lingulidae. Carnets de Géologie/Notebooks on Geology, Maintenon, Letter 2003/01, (CG2003_L01_CCE)    and    

    • Emig C. C. & Z. Herrera, 2006. Dignomia munsterii (Brachiopoda, Lingulata) from the Ordovician of Bolivia, with redescription of the genus. Geodiversitas, 28 (2), 227-237.   

     FIGURES : Dignomia



    Dignomia munsterii (d'Orbigny, 1842)

    Lingula submarginata d'Orbigny, 1850 (pro Lingula marginata d'Orbigny, 1842: p. 28, Pl. 2 fig.5; non Phillips, 1836): p. 14; Lingula lineata Hoek, 1912, in Steinman & Hoek, 1912: p. 232; Dignomia boliviana Emig, 1996, in Gagnier et al. (1996): p. 338, Fig. 6.

    Holotype: none. Syntypes a dorsal and a ventral valve from Zudáñez (= Tacopaya), Chuquisaca region (MNHN R06654).
    Other specimens: MNHN A24313 = Cerro San Pedro in Cochabamba (17°23’45”S, 66°07’40”W); MNHN A24314 = Cerro Chakeri, Puntata Province, north of Sacabambilla (17°30’00”S, 66°47’58”W).
    A large collection from Cerro San Pedro in Cochabamba Ciudad is also housed in the “Museo de la Universidad de Zaragoza”.
    Type horizon: Middle/Late Ordovician, Caradocian or Llanvirnian - Llandeilian.

    Diagnosis - (Emig & Herrera 2006)   including the figure in front

    The outline of the shell is an elongate oval. Two large medio-lateral grooves, longitudinally striated, extend from the umbonal region to the anterior margin of the valves; a median groove is narrow. On the outer surface of the dorsal valve is a median groove that occupies its whole length. On the ventral valve, the groove extends from the anterior margin to about the half to two-thirds of the length.
    Anterior margin straight, without indentation at the level of the grooves. Lateral margins subparallel; width of the shell largest at or above the middle; surface smooth with numerous weak, occasionally well-marked, growth lines. Umbonal region rounded on dorsal valve, pointed on ventral valve. Small proparea slightly curved with a weak pedicle groove, continuous with internal valve side. The ventral lophophoral cavity occupies approximately 36 % of the length of the valve. Mantle canals curved. A pair of narrow subparallel, V-shaped, grooves extend from the anterior adductor scars to the unpaired posterior adductor scars; three long oblique internal muscles; a V-shaped perimial line.
    No internal observation of dorsal valve.


    Dorsal & ventral valves

     


    Ventral valve