THE CLIMATE ROLE IN THE DISTRIBUTION OF THE TERRESTRIAL CRETACEOUS CROCODYLOMOPRHA THROUGHOUT GONDWANALAND

ISMAR DE SOUZA CARVALHO, ZULMA GASPARINI Y LEONARDO SALGADO

Mendoza, Argentina

Simposio; Gondwana 12: Geological and Biological Heritage of Gondwana; 2005

Comisión ad hoc

The terrestrial Cretaceous Crocodylomorpha from Gondwana comprises distinct groups as the notosuchians, peirosaurids, baurusuchids and the sphagesaurids. They are found overspread in Brazil, Uruguay, Argentina, Camerum, Niger, Malawi, Madagascar, China and Pakistan, in deposits of fluvial and lake environments. The oldest ones are probably Berriasian (Uiraúna Basin, Brazil), despite their diversification took place during Aptian-Albian in South America, Africa  and also China. A peculiar aspect of these terrestrial crocodylomorphs is that some of them are cosmopolitan. Notosuchians are found in Brazil (Uiraúna, Parnaíba, Araripe and Bauru basins), Uruguay  (Guichón Formation), Argentina (Neuquén Basin), África (Koum, Tegama and Mahajanga basins) and China (Wulong Formation). The peirosaurids occur in Brazil (Bauru Basin), Argentina (Neuquén Basin) and Madagascar (Mahajanga Basin). The baurusuchids are found in Brazil (Bauru Basin), Argentina (Neuquén Basin) and Pakistan (Pab Formation, Balochistan Province). The sphagesaurids are the unique group still restrict to South America (Bauru Basin, Brazil). According to Markwick living crocodilians are climatically controlled by a mean annual temperature equal or more than 14.2ºC, although local hydrological conditions play an important role, providing a buffer effect against temperature extremes. Then the extant crocodilians are limited to tropical and subtropical environments. The analysis of the geological distribution of terrestrial Crocodylomorpha in the Early and Late Cretaceous palaeogeographic and palaeoclimatic maps show a spatial distribution that similarly to modern crocodilians indicates that temperature was the principal influence on their global distribution. Although the continentality, expressed by seasonality and increased aridity is a limiting factor to the distribution of extant crocodilians, the Cretaceous notosuchians, baurusuchids, peirosaurids and sphagesaurids are found distributed in arid climate zones during Early and Late Cretaceous. Probably they developed ecological strategies that allowed them to live in a hot and arid climate. The aridity or maybe a seasonal warm and dry climate alternated with moments of more wet periods, play a role, that have not yet been analyzed, that justify the domain of bizarre crocodilians in Gondwana during the Cretaceous.