Global palaeobiogeographical patterns in brachiopods from survival to recovery after the end-Ordovician mass extinction

摘要

Extinction events usually disrupt palaeobiogeographical patterns, but there have been few detailed studies of the Early Silurian survival-recovery period after the Late Ordovician mass extinction. This paper summarizes and revises published information on the recovery of Early and Late Rhuddanian brachiopod faunas. The global dataset consists of 137 occurrences, 72 genera, and 13 localities of Early Rhuddanian (survival interval), and 271 occurrences, 91 genera, and 26 localities of the Late Rhuddanian (early recovery interval). The data are analyzed using Cluster Analysis, Nonmetric Multidimensional Scaling, and Minimum Spanning Tree using Yule's Y coefficient and the Raup-Crick coefficient (probabilistic index of similarity). The results display palaeolatitudinal distribution patterns for brachiopods during their survival and recovery. Frequency analysis of the data indicates that cosmopolitan taxa before the mass extinction decreased in their post-extinction distribution. The survivors were mostly confined to one palaeoplate or even one locality in the survival interval, but expanded progressively in the subsequent recovery period.