Origin of the Mesozoic ‘Boreal’ realm

Abstract

Origin of the Mesozoic 'Boreal' realm SIR-Marine faunas from Jurassic and Cretaceous rocks of the northern hemisphere show the presence of two contrasting faunal realms, known as Tethyan and Boreal, or by equivalent names. The differentiation of these realms has been widely regarded as due to difference in climate, and But Sellwood (1972, p. 154) has rejected this suggestion, and returned to the notion that temperature was the most important factor.