Diversity and paleobiology of the Santacrucian birds

DEGRANGE F; NORIEGA JI; ARETA JI

Early Miocene Paleobiology in Patagonia: High-Latitude Paleocommunities of the Santa Cruz Formation

Cambridge University Press

Año: 2012; p. 138 - 155

This chapter presents the state of knowledge of the aviandiversity recorded in Santacrucian beds (late Lower Miocene)with an updated systematic summary of all taxa.Phorusrhacids outnumber seriemas, rheas, and basal falconiformsin diversity and abundance. More fragmentaryoccurrences are reported of pelecaniforms, anseriforms,gruiforms, and ciconiiforms. Body masses of fossil formsare inferred from the dimensions of their hindlimb bones(i.e. femur, tibiotarsus) based on logarithmic equationspreviously modeled from living analogs. In some cases,body sizes of the extinct species are also inferred from therelative sizes of other bones of similar, extant species.Inferences about diet and foraging strategies are basedon the size and shape of the limb elements and structuraldetails of the cranial elements, by analogy with extantbirds. The predator niche is represented by falconids, fourspecies of phorusrhacids and a seriemid. Phorusrhacidsand seriemids probably lived in open areas because oftheir cursorial capabilities. However, birds such as thewaterfowl, limpkins, spoonbills, and darters indicate thepresence of temporarily flooded savannas or permanentwater bodies in forested areas. Habitat preferences ofextant seriemas, rheas, tinamous, and the falconidHerpetotheres are consistent with Chacoan-like conditions,and they are useful to infer by extrapolation similarSantacrucian paleoenvironments for their extinct analogs.Santacrucian scenarios were probably characterized byseasonality in temperature and rainfall and the presenceof alternating areas of herbaceous vegetation with shrubbyor wooded areas.