Shark (Chondrichthyes) microremains from the Lower Cretaceous Quiricó Formation, Sanfranciscana Basin, Southeast Brazil

Abstract

ABSTRACT The first chondrichthyan teeth, dermal and oropharyngeal denticles from the Lower Cretaceous lacustrine Quiricó Formation (Sanfranciscana Basin), in southeastern Brazil are described. Eight microremains morphologies have been recovered from lower levels of this formation, dated as possibly Valanginian with basis on ostracods. The dermal denticles belongs to indeterminate Hybodontiformes; some teeth are ascribed to ?Lonchidiidae. The presence of Tribodus is suggested by some dermal denticles, but this assignment requires confirmation with more complete material. The new specimens indicate a much greater diversity of chondrichthyans in the Quiricó Formation than previously thought. The associated occurrence of hybodontiforms, the coelacanthiform Mawsonia and early neopterygians observed in the Sanfranciscana Basin is not uncommon for the Cretaceous sedimentary strata of Brazil and Africa. However, the use of the Quiricó Formation shark remains as biostratigraphic tool is limited, due to their current poor taxonomic and relatively broad temporal distribution.