Totoralia, a new conical-shaped mollusk from the Middle Cambrian of western Argentina
| Autor: | Tortello, M. F., Sabattini, N. M. |
|---|---|
| Rok vydání: | 2011 |
| Předmět: | |
| Zdroj: | Dipòsit Digital de Documents de la UAB Universitat Autònoma de Barcelona Geologica Acta; Vol. 9 No 2 (2011); 175-185 Geologica Acta; Vol. 9 No. 2 (2011); 175-185 Geologica Acta; Vol. 9 Núm. 2 (2011); 175-185 RCUB. Revistas Científicas de la Universidad de Barcelona instname Geologica Acta; 2011: Vol.: 9 Núm.: 2; p. 175-185 Recercat. Dipósit de la Recerca de Catalunya Recercat: Dipósit de la Recerca de Catalunya Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya) |
| ISSN: | 1696-5728 1695-6133 |
| Popis: | The new genus Totoralia from the Late Middle Cambrian of El Totoral (Mendoza Province, western Argentina) is described herein. It is a delicate, high, bilaterally symmetrical cone with a sub-central apex and five to seven prominent comarginal corrugations. In addition, its surface shows numerous fine comarginal lines, as well as thin, closely spaced radial lirae. Totoralia gen. nov., in most respects, resembles the Cambrian helcionellids Scenella BILLINGS and Palaeacmaea HALL and Whitfield. Although Scenella has been considered as a chondrophorine cnidarian by some authors in the past, now the predominant view is that it is a mollusk. Likewise, several aspects of Totoralia gen. nov. morphology indicate closer affinities with mollusks. The specimens studied constitute elevated cones that are rather consistent in height, implying that they were not flexible structures like those of the chondrophorines. The presence of a short concave slope immediately in front of the apex can also be interpreted as a mollusk feature. In addition, the numerous comarginal lines of the cone are uniform in prominence and constant in spacing, and are only represented on the dorsal surface of the shell; thus, they are most similar to the incremental growth lines of shells of mollusks. The morphology of Totoralia gen. nov. is regarded as primitive in the Helcionelloida because the ancestor of the class is likely to have had a minute, untorted limpet-shaped shell. Although the new genus herein described seems to be endemic to Argentina, the Cambrian occurrences of related scenellid genera suggest affinities with Laurentia. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|