January 20 , 2017:

Here we describe El Horcajo, a new multiootaxic assemblage in the vicinity of Trevijano (La Rioja, Spain). It is located in the palustrine facies of the Enciso Group (Cameros Basin). This new locality has provided dozens of eggshell fragments, together with other vertebrate remains and charophyte fructifications, which allow dating of the locality as Valanginian-Hauterivian. Five ootaxa have being recognized: 1) the Spheroolithidae Guegoolithus turolensis; 2) a surprisingly thick Prismatoolithidae indet., with certain affinities to the oogenus Sankofa and which may represent a new oogenus and oospecies for this oofamily; 3) the Krokolithidae Krokolithes sp.; 4) recrystallized ?Testudoolithidae eggshells; and 5) ?Geckoolithidae eggshells of uncertain affinity. This oodiversity is similar to that of other eggshell microsites. The ootaxonomic list differs from the other Iberian locality of the same age, Pochancalo 1, Villanueva de Huerva Formation, in lacking sauropod and megalosaurid theropod eggshells, but shares the presence the ornithopod and coelurosaurian theropod eggshells with other younger microsites found in similar facies. These new locality has immediate consequences for the tectono-sedimentary framework of the Cameros Basin and the reliability of eggshells as biostratigraphic markers, as challenges both the age of the Enciso Group and the viability of Guegoolithus as a guide fossil for the lower Barremian.

Miguel Moreno Azanza, José Manuel Gasca, Ignacio Díaz Martínez, Blanca Bauluz Lázaro, José Ignacio Canudo Sanagustín, Arturo Fernández & Félix Pérez-Lorente (2016)
A multi-ootaxic assemblage from the Lower Cretaceous of the Cameros Basin (La Rioja; Northern Spain). [Una asociación multi-ootáxica del Cretácico Inferior de la Cuenca de Cameros (La Rioja; Norte de España)].
Spanish Journal of Palaeontology 31(2): 305-320.