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

Genus Credolingula Smirnova & Ushatinskaya, 2001
[Type-species = C. olferievi ]
Shell elongate oval, weakly biconvex, with subparallel lateral margins and rounded sublinear anterior margin. At each valve, two weak plications running from urabo to anterolateral corners detine low median fold. Pseudointerareas faint.
Ventral valve: visceral field rounded triangular, extending half valve length. Posterior adductor scar trapezoldal, set close to fused posterior oblique and anterior oblique muscle scars. Anterior adductor scars can join near visceral field anterior margin. Two narrow subparallel furrows run from posterior margin through posterior adductor scar to visceral field of anterior margin.
Dorsal valve: visceral field occupies about two-thirds of valve length. Posterior adductor scar horseshoe-shaped, joined with extemal and intemal oblique muscle scars into one structure. Anterior adductor scars adjoin anterior oblique muscle scar. Median slit developed to different degree.

Occurrences: Russia (Dagestan; Belgorod region; Saratov and Volgograd regions; northern Caucasus) - S America (Patagonia, Chile).

Diagnosis from Smirnova & Ushatinskaya (2001)

Species of Credolingula

  • C. olferievi  Smirnova & Ushatinskaya, 2001

  • C. subtruncata  Smirnova & Ushatinskaya, 2001

  • The references of this page are:

    • Holmer L.E. & Bengston P., 2009. The first occurrence of a lingulid brachiopod from the Cretaceous of Sergipe, Brazil, with a restudy of 'Lingula' bagualensis Wilckens, 1905 from Southern Patagonia. Paläontogische Zeitschrift, 83, 255-266.

    • Smirnova T. N. & G. T. Ushatinskaya, 2001. New lingulids (Brachiopoda) from the Lower Cretaceous of European Russia, with notes in the microstructure of their shells. Paleont. J., 35 (4), 387-395.

    • Wilckens O., 1905. Die Lamellibranchiaten, Gastropoden etc. der oberen Kreide Südpatagoniens. Berichte der Naturforschenden Gesellschaft zu Freiburg i. Br., 15, 1–66, [Pls. p. 91–156].

    Credolingula olferievi Smirnova & Ushatinskaya, 2001

    Holotype: PIN, no. 4796/1. Type locality: Stoilo Quarry 10 km W frorn the town of Staryi Oskol, Belgorod region (Russia). Type horizon: Lower Cretaceous, probably Lower Albian.


    Diagnosis - (Smirnova & Ushatinskaya, 2001)
    including the figure

    Shell elongate oval in outline or slightly pentagonal with sublinear to rounded sublinear short anterior margin. Lateral margins are subparallel. The shell tapers slightly anteriorly.
    Both valves bear weak median folds defined by two low plications. The valves appear one-third of the distance froin the umbo, run to the anterior margins, and form low sulci in their central parts. The exterior shell surface bears numerous growth microlines tens of microns to 0.2-0.3 mm thick and fine radial striation, which usually crosses several growth microlines at a 50-60° angle.
    The ventral valve is usually more convex than the dorsal valve. The umbo is rounded with narrow pseudointerarea. The apical angle is 85-92°. The pseudointerarea has a deep pedicle groove that tapers toward the umbo and is separated from the lateral pseudointerarea by sharp acute ridges.
    The dorsal valve attains the greatest convexity in the posterior half and sometimes slightly thickens anteriorly. Its beak is rounded, and the pseudointerarea is narrow and faint.

    Shell interior.

    In the ventral valve, the visceral field occupies about half of its length. It is triangular posteriorly and rounded anteriorly. The large posterior adductor scar is irregular-trapezoidal with a beveled anterior margin, so that its left side is more extended anteriorly. It is separated by a sharp plication from the intermediate and posterior oblique muscle scars, which run nearly parallel to the posterior and posterolateral valve margins for a fairly long distance. The right and left intermediate and posterior oblique muscle scars are slightly différent. The left intermediate oblique muscle scar is narrow, strongly prolate, and connected through the anterior constriction with the anterior oblique muscle scars. On the right side, there is a well-defined scar of an odd internal. oblique muscle. It parallels the posterior oblique muscle scar. These two muscle scars may join, or may be separated by a thin narrow ridge. The anterior oblique muscle scars continue anteriorly to the posterior ones. They vary in outline from semicircular with a straight posterior margin to oval prolate with extended inner margins and a concave posterior margin. The anterior adductor scars are set on a semicircular platforin near the visceral field anterior margin. They are transversely prolate with their long axes directed 45-55° to the plane of symmetry. A pair of thin subparallel grooves arises anteriorly to the pseudointerarea and run longitudinally through the entire visceral field. The rounded anterior end of the strip, which is bordered by grooves, may be separated by a constriction. The main mande canals are strongly curved inwards and bear a few bifurcated tips.
    In the dorsal valve interior, the visceral field occupies about two-thirds of the valve length. It is oval-rhomboidal in outline with concave posterolateral and rounded anterior margins. The posterior adductor scar is large, horseshoe-shaped, and asymmetrical, consisting of two parts divided by a median elevation that may be longitudinally depressed. The right part of the scar is more extended anteriorly and tear-drop-like in outline with a pointed posterior and rounded anterior margins. The left part is less elongate and oval in outline. The scars of paired external, oblique muscles adjoin the posterior adductor scar from which they are separated by thin plications. They are long, weakly broadening anteriorly, and subparallel lateral valve margins. The scars of interna] oblique muscles vary from rounded quadrate to oval with extended lateral margins. They are shallower and 1.5-2 times broader than the external oblique muscle scars. The scars of the anterior oblique muscle and anterior adductors are grouped together into one muscle platform. The anterior adductor scars are seriticircular and large. The scar of the anterior oblique muscle is oval and elongated with a rounded anterior margin. In well-preserved specimens, a narrow median slit is traced 1-2 mm posteriorly to the anterior oblique muscle scar. A pair of alate impressions with distinct growth lines is seen just posteriorly to the anterior muscle platform. These impressions are set on an elevated median basement. Their posterior margin is curved inwards, externally convex, and biased toward the striplike median line internally. Their internal ends may be expanded and curved inward. Their growth lines appear to continue the growth lines of anterior adductors. These impressions are identified as attachment sites of a gastroparietal system through the central opening of which the coelomic fluid fed the main mande canals. The traces of the vascular system in the dorsal valve are seen from the middle of the visceral field to its anterior margin. They are represented by wide main mande canals that curve weakly inwards and have bifurcated distal tips (lateral canals) that diverge from the main canals.

    Credolingula subtruncata Smirnova & Ushatinskaya, 2001

    Holotype: PIN, no. 4796/7. Type locality: Akusha Village, Dagestan. Type horizon: Lower Cretaceous, Upper Albian.
    Etymology: From the closely related species Lingula truncata Sowerby, 1836 and the Latin prefix sub (under/with).

    Diagnosis - (Smirnova & Ushatinskaya, 2001)   no figure

    The shell is strongly elongated, moderately convex posteriorly and fiattened anteriorly, with rounded umbo, parallel lateral margins, and rounded-trapezoidal anterior margin. The shell width is equal over its length. Both valves bear weak flat-sloped folds defined anteriorly by two short plications. Fine and relatively wide growth lines alternate. No trace of radial striation. The ventral valve umbo is low, pointed, its apical angle is 95-100°. The pseudointerarea is narrow, the pedicle groove is broad and shallow. The dorsal valve umbo is low, rounded; the dorsal valve pseudointerarea is narrow.
    Close to the type species. The ventral valve contains two distinct subparallel grooves, anterior adductor scars, and separated scars of the posterior and anterior oblique muscles. The dorsal valve contains faint scars of internal and extemal oblique muscles. The anterior adductor scars are prolate and tilted toward each other at a 65-70°angle. The presence of a median slit is possible.

    Credolingula? bagualensis (Wilckens, 1905)

    Lingula bagualensis Wilckens, 1905.
    Lingularia? bagualensis Holmer & Bengtson, 1996.
    Lingula bagualensis Williams et al, 2000.

    Holotype: MLP 9006. Type locality: upper valley of the Río Baguales, southern Patagonia, Chile (Magallanes or Austral Basin). Type horizon: Cerro Cazador Formation, uppermost Cretaceous.
    Etymology: .

    Diagnosis -


    Lingulide muscle arrangement