Lower Devonian calmoniid trilobites from the Argentine Precordillera: New taxa of the Bouleia Group, and remarks on the tempo of calmoniid radiation.

EDGECOMBE, G.D.; VACCARI, N.E.; WAISFELD, B.G.

GEOLOGICAL MAGAZINE

Cambridge University Press

Lugar: Londres; Año: 1994 vol. 131 p. 449 - 464

0016-7568

New calmoniids from the Lower Devonian Talacasto Formation in the Precordillera of San Juan, Argentina, extend the stratigraphic and geographic ranges of a clade including Bouleia Kozlowski, 1923 and Parabouleia Eldredge, 1972. The new genus Talacastops accommodates the Lochkovian T. zarelae sp.nov. from the Talacasto Formation and a closely related species from western Bolivia (Talacastops sp.nov. A). The diagnosis of Parabouleia is broadened to include P. eldredgei sp.nov., from Lochkovian strata in the lower part of the Talacasto Formation. Calmoniids from below the Scaphiocoelia Assemblage Zone display morphological disparity that rivals later occurrences, and do not conform to a model of gradual transformation of an acastomorph ancestor. Stratigraphic range extensions based on correction for ghost lineages imply a high diversity within Calmoniidae very early in the Devonian.