Faunal turnover and development of fossil avifaunas in South America.

Abstract

This paper presents the first quantitative analysis of faunal dynamics in fossil S American birds. The record up to 1981 includes 61 families (8 extinct, 13%), 194 genera (50 extinct, 26%), and 276 species (93 extinct, 34%). A number of fossil families in the Cenozoic of S America indicate that important lineages have left no trace in the Recent fauna. Thus Recent birds cannot provide us with sufficient clues to reconstruct the composition of early to mid-Tertiary S American faunas. Relatively few late Pleistocene genera and species have become extinct, so that reconstruction of Pleistocene faunas based on Recent taxa can probably represent a statistically accurate picture of the recent past. Reconstruction of faunal histories can be substantially improved, however, by consultation of the fossil record of the Pliocene and Pleistocene. Rates of faunal turnover, expressed as the average of estimates of origination rates (based on first appearances in the fossil record) and extinction rates (last appearances) of S American genera per million years, increased from the Miocene to the late Pleistocene. The statistics of faunal dynamics are as yet insufficiently precise to detect the occurrence of the Great American Interchange in birds, although individual examples (Milvago, Teratornithidae Titanis) suggest that it took place. -from Author