Fossil eggshell cuticle elucidates dinosaur nesting ecology.

Area of Science:

• Paleontology
• Biogeochemistry
• Evolutionary Biology

Background:

• The avian eggshell cuticle, composed of lipids and hydroxyapatite (HAp), protects against dehydration and microbial invasion.
• Cuticle modulates eggshell reflectance and is a crucial trait for ecological signaling in modern birds.
• Direct evidence for cuticle preservation in extinct birds and non-avian dinosaurs has been lacking.

Purpose of the Study:

• To present the first direct and chemical evidence for cuticle preservation on dinosaur eggshells.
• To investigate the presence and composition of the cuticle layer in fossil theropod eggshells.
• To explore the evolutionary implications of cuticle preservation in dinosaur nesting ecology.

Main Methods:

• Analysis of oviraptorid and alvarezsaurid dinosaur eggshells using scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), and Raman spectroscopy (RS).
• Elemental analysis with EPMA to identify hydroxyapatite (HAp) in the cuticle layer.
• Chemometric analysis of Raman spectra to confirm cuticle preservation in fossil and extant eggs.

Main Results:

• High concentrations of phosphorus, indicative of hydroxyapatitic (HAp) cuticle, were detected at the boundary between dinosaur eggshells and sediment.
• Elemental analysis confirmed the autochthonous origin of phosphorus, ruling out sediment contamination.
• Raman spectroscopy provided supportive evidence for cuticle preservation in oviraptorid and alvarezsaurid eggshells.

Conclusions:

• The study validates cuticle preservation on dinosaur eggshells, extending its presence through deep time.
• Cuticle preservation can be traced back to maniraptoran dinosaurs, potentially enhancing their reproductive success.
• Preserved dinosaur eggshell cuticles offer a new resource for studying the evolution of dinosaur nesting strategies and ecology.