Macrofauna of the Villamartín Section: Coniacian/Santonian boundary, North Castilian Platform, Burgos, Spain

The occurrence of macrofossils in the Villamartín section, a succession of outer platform sediments spanning the Coniacian/Santonian (C/S) boundary in the North Castilian Platform of northern Spain, is documented, with taxa recognised illustrated and their distribution discussed. This section could serve as a “boundary parastratotype” to complement the Cantera de Margas section of Olazagutia (Navarra, northern Spain), the proposed C/S boundary stratotype section that lacks in ammonites. The inoceramid bivalve Platyceramus undulatoplicatus (Römer), whose first occurrence (FO) is the primary marker for the Coniacian/Santonian boundary, occurs at two levels, separated by only 2 m of sediment. Additional criteria for correlation are provided by the FO of the ammonite Placenticeras polyopsis (Dujardin) and the occurrence of the inoceramid bivalve Platyceramus cycloides (Wegner) above the boundary, and the first and/or the last occurrences below the boundary of: the inoceramid bivalves Magadiceramus villamartinensis (López), M. subquadratus (Schlüter) (index species of the M. subquadratus Zone) and Inoceramus stantoni Sokolov; the ammonites Protexanites bourgeoisi (d'Orbigny) (index species of the P. bourgeoisi Zone), Texanites hispanicus Collignon, Hemitissotia turzoi Karrenberg (index species of the Hemitissotia sp. Zone), Prionocycloceras iberiense (Basse) (index species of the P. iberiense Zone), and Gauthiericeras margae (Schlüter) (index species of the G. margae Zone); and the echinoids Cyathocidaris cyathifera (Agassiz), Proraster atavus (Arnaud), Micraster burgiensis Lambert, Micraster laxoporus d'Orbigny and Salenia (Salenia) geometrica? Agassiz.