Journal of Paleontology; May 2006; v. 80; no. 3;
p. 477-495; DOI: 10.1666/0022-3360(2006)80[477:EOATFT]2.0.CO;2
© 2006 Paleontological Society
EARLY ORDOVICIAN AGNOSTOID TRILOBITES FROM THE SOUTHERN MONTAGNE NOIRE, FRANCE
M. FRANCO TORTELLO1,2,
DANIEL VIZCAÏNO3 and
J. JAVIER ÁLVARO2,4
1 Departamento Paleozoología Invertebrados, Museo de Ciencias Naturales, Paseo del Bosque s/n°, 1900 La Plata, Argentina,
2 Laboratoire de Paléontologie et Paléogéographie du Paléozoïque, UMR 8014 CNRS, Université des Sciences et Technologies de Lille, UFR Sciences de la Terre, 59655 Villeneuve d'Ascq, France, <tortello{at}museo.fcnym.unlp.edu.ar>,
3 7, rue Jean-Baptiste Chardin, Maquens, 11090 Carcassonne, France, <daniel.vizcaino{at}wanadoo.fr>,
4 Departamento Ciencias de la Tierra, Universidad de Zaragoza, 50009 Zaragoza, Spain, <Jose-Javier.Alvaro{at}univ-lille1.fr>
New collections rich in agnostoid trilobites were recovered from Lower Ordovician strata of the southern Montagne Noire, France. The faunas occur in the La Gardie/Val d'Homs, SaintChinian, La Maurerie, and Landeyran formations, coinciding with deposition in muddy outer-platform settings. Many previously described species are revised and their stratigraphic ranges emended. The studied agnostoids include Geragnostus cf. sidenbladhi (Linnarsson), G. aff. sidenbladhi, G. crassus Tjernvik, G. splendens (Holub), G. cf. explanatus Tjernvik, G. boutouryensis Howell, G. occitanus Howell, Geragnostus sp., Trinodus corpulentus Howell, Homagnostoides ferralsensis (Munier-Chalmas and Bergeron), Corrugatagnostus coulobresensis n. sp., Corrugatagnostus sp., Leiagnostus miqueli Sdzuy, and Leiagnostus sp. The record from the upper part of the SaintChinian Formation suggests a late Tremadocian age, whereas an early Arenigian age is indicated for the upper part of the La Maurerie Formation. Although the agnostoid record generally reinforces the peri-Gondwanan character of the Lower Ordovician shelly faunas from the Montagne Noire, some agnostoid species are independent of specific paleogeographic boundaries.
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