Ecological signature of the end-Triassic biotic crisis: what do bivalves have to say?

Abstract

In order to understand the causes underlying the Triassic–Jurassic (T/J) mass extinction, we tested different bivalve features for extinction selectivity, i.e. shell mineralogy, age at the Rhaetian and three main autoecologic traits (feeding mechanism, tiering and motility/attachment). Also, diversity and turnover rates throughout the Triassic and the Early Jurassic were analysed in detail. The dataset employed for this analysis was a precise database at genus level including data from Induan to Sinemurian times. Results point to a true mass extinction for bivalves around the T/J boundary. This extinction was not age-selective at the boundary. Certain analyses suggested that shell mineralogy was a character significantly increasing survival odds, but this relationship seems to reflect selectivity on autoecologic traits. There was no difference in extinction proportions between both feeding types (i.e. deposit feeders and filter feeders); among the other traits, deep burrowers, epifaunal-motile and endobyssate forms seem to have been favoured, while shallow burrowers (and probably reclined forms) were more heavily affected. This pattern suggests an environmental stress at the boundary with some particular issues affecting the different life modes. Models linking magmatism in the Central Atlantic Magmatic Province with the end-Triassic mass extinction are a plausible scenario for this kind of perturbation.

Keywords:

• end-Triassic extinction
• Bivalvia
• selectivity
• shell-mineralogy
• autoecology
• CAMP

Acknowledgements

We thank A. Márquez-Aliaga for comments and help with bibliography and database, M. De Renzi for discussion on several methods applied in this work, M. Griffin for improvement of English of the manuscript and M. Manceñido for his suggestions and constant motivation, and for critically reading of the manuscript. Special thanks to S. E. Damborenea for reading previous versions of this paper and for her comments and suggestions which greatly improved its quality. This paper benefited from the comments of M. Hautmann, W. Kiessling, M. Aberhan and two anonymous reviwers. Research was funded by a post-doctoral grant of MAEC-AECID (Ministerio de Asuntos Exteriores y de Cooperación y Agencia Española de Cooperación Internacional) to S.R. and a CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina) doctoral scholarship to J. E. This is a contribution to IGCP projects 506 and 572.

Notes

1. Email: [email protected]

Additional information

Notes on contributors

Javier Echevarría

1