Citation:

Ribeiro, V., Holwerda F., & Mateus O. (2013).  Theropod egg sites from the Lourinhã Formation, Portugal. Journal of Vertebrate Paleontology, Program and Abstracts, 2013. 198.

Dinosaur eggs and eggshells of Jurassic age or older are relatively rare worldwide when compared with Cretaceous ones. However, the Lourinha region in central-west Portugal is rich in Kimmeridgian-Tithonian dinosaur egg- and eggshell localities, two with associated theropod embryo material of Lourinhanosaurus and another large theropod.
Here, we describe specimens from two sites from the Late Kimmeridgian-Early Tithonian Sobral Member of the Lourinha Formation: i) eggshells from Casal da Rola (Museu da Lourinhã [ML]1194) and ii) a new isolated egg from Porto das Barcas (ML1842). These are compared with previous findings with similar morphology: Lourinhanosaurus nest from Paimogo (ML565) and clutches from Peralta (ML156), and the theropod clutch ML1403, also from Porto das Barcas but in a different horizon and locality than ML1842.
Two main ootaxa were identified: ML1194 as Preprismatoolithus and ML1842 as an undescribed Dendroolithus-like phaceloolithid. The first is clearly identified by the dinosauroid eggshell morphotype angustiprismatic/obliquiprismatic, with an
obliquicaniculate or angusticaniculate pore system, smooth outer surface, and an eggshell thickness range of 0.8-1.0 mm. Dendroolithus is identified by: eggs are medium sized (10-20 cm) and spherical in shape; eggshell morphotype dendrospherulitic, with shell units irregularly shaped and displaying a fanning pattern; pores display a prolatocanaliculate network throughout the eggshell; outer surface ornamentation is irregular with crests and the pores irregularly dispersed between the crests; and average eggshell thickness is approximately 1.1 mm.
The eggshells from Casal da Rola are identical to Preprismatoolithus eggs from Paimogo and Peralta. The eggs from Paimogo have been assigned to Lourinhanosaurus by the presence of embryos, so we ascribe Casal da Rola also to Lourinhanosaurus.
The phaceloolithid egg ML1842 is morphologically identical to the clutch ML1403 found in the same area and assigned to a large theropod. Apart from Porto das Barcas, Phaceloolithidae is only known from the Late Cretaceous of China and Mongolia.