Abstract
BackgroundMegaloolithid eggs have long been associated with sauropod dinosaurs. Despite their extensive and worldwide fossil record, interpretations of egg size and shape, clutch morphology, and incubation strategy vary. The Pinyes locality in the Upper Cretaceous Tremp Formation in the southern Pyrenees, Catalonia provides new information for addressing these issues. Nine horizons containing Megaloolithus siruguei clutches are exposed near the village of Coll de Nargó. Tectonic deformation in the study area strongly influenced egg size and shape, which could potentially lead to misinterpretation of reproductive biology if 2D and 3D maps are not corrected for bed dip that results from tectonism.Methodology/FindingsDetailed taphonomic study and three-dimensional modelling of fossil eggs show that intact M. siruguei clutches contained 20–28 eggs, which is substantially larger than commonly reported from Europe and India. Linear and grouped eggs occur in three superimposed levels and form an asymmetric, elongate, bowl-shaped profile in lateral view. Computed tomography data support previous interpretations that the eggs hatched within the substrate. Megaloolithid clutch sizes reported from other European and Indian localities are typically less than 15 eggs; however, these clutches often include linear or grouped eggs that resemble those of the larger Pinyes clutches and may reflect preservation of incomplete clutches.Conclusions/SignificanceWe propose that 25 eggs represent a typical megaloolithid clutch size and smaller egg clusters that display linear or grouped egg arrangements reported at Pinyes and other localities may represent eroded remnants of larger clutches. The similarity of megaloolithid clutch morphology from localities worldwide strongly suggests common reproductive behaviour. The distinct clutch geometry at Pinyes and other localities likely resulted from the asymmetrical, inclined, and laterally compressed titanosaur pes unguals of the female, using the hind foot for scratch-digging during nest excavation.
Highlights
The titanosaur clade has long been associated with eggs of the oofamily Megaloolithidae [1,2,3,4,5,6]
The most extensively documented megaloolithid localities occur in Upper Cretaceous rocks of southern France, northern Catalonia, India, and South America [7]
Trace fossil nests [37] and GH20 calculated for the Auca Mahuevo titanosaur eggs in Argentina [36] suggest that these eggs were not incubated underground and the strategy employed remains unclear
Summary
The titanosaur clade has long been associated with eggs of the oofamily Megaloolithidae [1,2,3,4,5,6]. The 1997 discovery of titanosaur embryos in Megaloolithus patagonicus eggs from the Auca Mahuevo locality in Argentina allowed the first definitive assignment of Megaloolithus eggs to titanosaur sauropod dinosaurs [10,11]. This extensive and worldwide fossil record of megaloolithid eggs provides important data for assessing reproductive characteristics such as egg size and shape, clutch morphology, and incubation strategy. Megaloolithid eggs have long been associated with sauropod dinosaurs Despite their extensive and worldwide fossil record, interpretations of egg size and shape, clutch morphology, and incubation strategy vary. Tectonic deformation in the study area strongly influenced egg size and shape, which could potentially lead to misinterpretation of reproductive biology if 2D and 3D maps are not corrected for bed dip that results from tectonism
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