Avian Paternal Care Had Dinosaur Origin

• Published in: Science (American Association for the Advancement of Science) 2008-12, Vol.322 (5909), p.1826-1828
• Main Authors: Varricchio, David J, Moore, Jason R, Erickson, Gregory M, Norell, Mark A, Jackson, Frankie D, Borkowski, John J
• Format: Article
• Language: English
• Subjects: Adults; Animal behavior; Animal reproduction; Animals; Behavior, Animal; Biological Evolution; Birds; Birds - physiology; Bone and Bones - anatomy & histology; Bones; Clutch Size; Dinosaurs; Dinosaurs - physiology; Earth sciences; Earth, ocean, space; Eggs; Evolutionary biology; Exact sciences and technology; Female; Female animals; Femur; Fossils; Histology; Male; Male animals; Maternal Behavior; Nesting Behavior; Ovulation; Paleontology; Paternal Behavior; Ratites; Regression Analysis; Sexual Behavior, Animal; Vertebrate paleontology
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1163245

The repeated discovery of adult dinosaurs in close association with egg clutches leads to speculation over the type and extent of care exhibited by these extinct animals for their eggs and young. To assess parental care in Cretaceous troodontid and oviraptorid dinosaurs, we examined clutch volume and the bone histology of brooding adults. In comparison to four archosaur care regressions, the relatively large clutch volumes of Troodon, Oviraptor, and Citipati scale most closely with a bird-paternal care model. Clutch-associated adults lack the maternal and reproductively associated histologic features common to extant archosaurs. Large clutch volumes and a suite of reproductive features shared only with birds favor paternal care, possibly within a polygamous mating system. Paternal care in both troodontids and oviraptorids indicates that this care system evolved before the emergence of birds and represents birds' ancestral condition. In extant birds and over most adult sizes, paternal and biparental care correspond to the largest and smallest relative clutch volumes, respectively.