Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

Journal of Paleontology

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by BENEDETTO, J. L. Search for Related Content GeoRef GeoRef Citation

NEW UPPER CAMBRIAN–TREMADOC RHYNCHONELLIFORMEAN BRACHIOPODS FROM NORTHWESTERN ARGENTINA: EVOLUTIONARY TRENDS AND EARLY DIVERSIFICATION OF PLECTORTHOIDEANS IN THE ANDEAN GONDWANA

¹ Consejo Nacional de Investigaciones Científicas y Técnicas, Centro de Investigaciones Paleobiológicas, Universidad Nacional de Córdoba, Av. Vélez Sarsfield 299, 5000 Córdoba, Argentina, <jbenedetto{at}arnet.com.ar>

New rhynchonelliformean brachiopods are documented from Upper Cambrian and Tremadoc beds of the Cordillera Oriental and Puna regions, which are representative of the initial radiation of Plectorthoidea on the Andean (South American) shelves of Gondwana. Protorthisina n. gen., so far the oldest known representative of the family Euorthisinidae, and Lesserorthis n. gen. (Euorthisinidae?) are described, as well as the new species Euorthisina? nazarenensis, Kvania mergli, Kvania lariensis, Kvania azulpampensis (with two subspecies), Kvania? primigenia, and Nanorthis calderensis (with two subspecies). Protorthisina, Kvania, and Nanorthis form a stratigraphically continuous series of species displaying well-defined evolutionary trends involving size, shell ornament, and internal features. In the cardinalia, a transition from a V-shaped septalium (typical of Protorthisina) through almost parallel brachiophore plates (typical of Kvania) to the orthoid notothyrial platform of Nanorthis is documented. The species Nanorthis purmamarcaensis Benedetto and "Nanorthis" grandis (Harrington) are considered as the end members of the lineage. The heterochronic (peramorphic) origin of this trend is supported by ontogenetic evidence from species of Kvania and Nanorthis calderensis. The origin of the ‘plectorthoid’ cardinalia of Kvania from a euorthisinid configuration present in the stem group, followed by the appearance of a orthoidlike configuration in Nanorthis, pose an intricate systematic problem. The preliminary phylogenetic analysis of the northwestern basin taxa shows that the Upper Cambrian Protorthisina simplex n. gen. and sp. is the stem group of both the nanorthid and euorthisinid clades. On the basis of the new evidence, the genus Nanorthis is removed from the Orthoidea to the Plectorthoidea, and the diagnosis of the families Euorthisinidae and Nanorthidae are revised.

This article has been cited by other articles:

				E. VILLAS, Z. A. HERRERA, and G. C. ORTEGA EARLY ORTHID BRACHIOPODS FROM THE TREMADOCIAN (LOWER ORDOVICIAN) OF NORTHWESTERN ARGENTINA Journal of Paleontology, July 1, 2009; 83(4): 604 - 613. [Abstract] [Full Text] [PDF]