Evidence of Reproductive Stress in Titanosaurian Sauropods Triggered by an Increase in Ecological Competition

Abstract

The occurrence of dinosaur pathologic eggs in the Late Cretaceous of Europe is well known, but their origin remains unclear. Here we expose the results of a detailed sampling of the conspicuous fossil record of Late Cretaceous titanosaurian eggs (oogenus Megaloolithius) from several southwestern Europe basins. After examining more than 450 samples, we observed a remarkable and statistically supported occurrence of multiple pathologic eggs in a relatively short stratigraphic range at the end of the early Maastrichtian, circa 71-70 Ma. All pathologic specimens exhibit multi-layered eggshell condition, a characteristic related to dystocia, or egg retention within the female uterus for an abnormal prolonged period of time. After exploring various scenarios, the occurrence of pathologic eggs is strongly correlated with an intense dinosaur faunal replacement that occurred during the early Maastrichtian in the Ibero-Armorican Island. Given that inter-species competiveness is proved to produce major affects in ecological communities, our results suggest that pathologies in the eggs of European titanosaurians could be a consequence of an increase in reproductive stress triggered by direct ecological competition between different dinosaurs. Thus, the present study provides a new perspective of how dinosaurs might have been affected by ecological/environmental disturbance.

Life and reproduction of titanosaurians: Isotopic hallmark of mid-palaeolatitude eggshells and its significance for body temperature, diet, and nesting

“…The isotopic compositions of the well-preserved eggshells plot into Cluster 3 (δ 13 C = − 15.0 to − 11.3‰ and δ 18 O = 28.0 to 32.7‰), while those from Sallent plot into Cluster 2 (δ 13 C = − 11.3 to − 7.8‰ and δ 18 O = 25.5 to 29.0‰). Sellés et al (2017) provided additional δ 13 C and δ 18 O values for pathologic specimens from the same sites. They also noticed a very wellpreserved microstructure and reported δ 13 C and δ 18 O values similar to those reported by Riera et al (2013), even though less tightly clustered.…”

Electron backscatter diffraction (EBSD) study of elongatoolithid eggs from China with microstructural and parataxonomic implications

“…Female birds that ingest synthetic pesticides through the food chain could produce significantly thinner or even soft eggshells (Hickey and Anderson 1968; Oestreicher et al 1971; Lincer 1975; Pruett-Jones et al 1981; Lundholm 1997; Holm et al 2006; Bouwman et al 2019). Delayed oviposition derived by environmental stresses can cause the formation of multilayered eggshells in birds, non-avian dinosaurs, and turtles (Romanoff and Romanoff 1949; Ewert et al 1984; Jackson and Varricchio 2003; Jackson et al 2004; Sellés et al 2017; Bailleul et al 2019). Other disorders of the avian female reproductive system related to abnormal eggshell and rarely seen microstructural abnormalities in non-avian dinosaur eggshells have also been reported, most of which are related to aging or infection of the female birds (Romanoff and Romanoff 1949; Keymer 1980; Grellet-Tinner et al 2010).…”

New Late Cretaceous titanosaur sauropod dinosaur egg clutches from lower Narmada valley, India: Palaeobiology and taphonomy

“…Such abnormal eggs result when the parent is facing physiological and/or environmental stresses, such as lack of nesting sites, floods or droughts, high population, sickness, diet, etc. [ 57 , 91 , 93 , 94 ].…”