A distinct dinosaur life history?

Abstract

Five factors, mobile terrestrial lifestyle, oviparity, parental care, multi-year maturation and juvenile sociality, contribute to a distinct life history for Mesozoic dinosaurs in comparison to extant archosaurs and mammals. Upright, para-sagittal gait reflects several synapomorphies of Dinosauria, and wide histological sampling suggests that multi-year maturation typified dinosaurs across a range of body sizes. Fossil support for juvenile sociality exceeds that for either oviparity or parental care. Implications of these factors include temporal segregation of adults for an extended, perhaps months-long reproductive cycle; spatial separation of adults and perhaps hatchlings to suitable nesting sites; increased likelihood for territoriality; reduced potential for long migrations; intraspecific niche segregation by age; population and community structure and macroevolutionary patterns. Fossil evidence for oviparity, parental care and juvenile sociality consists of combinations of adults, juveniles, embryos, eggs or traces and emphasises the importance of bonebeds and taphonomy in understanding dinosaur life-history strategies. Oviparity and parental care, predicted for dinosaurs by their extant phylogenetic bracket, have the least fossil support and cautions against overextending parsimonious interpretations to extinct taxa with the risk of obscuring novel or intermediate behaviours. Given the great diversity of Mesozoic dinosaurs, the proposed life history is hypothesised to represent only a general tendency.

Keywords:

• dinosaurs
• life history
• sociality
• parental care
• oviparity
• taphonomy

Acknowledgements

Thanks to Jack Horner, Paul Sereno and Ben Scherzer for providing opportunities or collaborations on various dinosaur bonebeds important to the formulation of this work. Research was supported by NSF grant #0847777 (EAR). Lee Hall provided the graphics. Tom Holtz and Jack Horner provided helpful and timely reviews.