Osteohistology and Growth of Edmontosaurus and Assessment of Life History Changes in Hadrosaurid Dinosaurs

Data on the life history of an organism provides an important window into its biology, ecology, and evolution but has been challenging to obtain for the extinct due to limitations of fossil sampling and the inability for direct observation. The recent utilization of osteohistology, which is the study of the internal bone microstructure, has revolutionized paleontological research and permitted quantitative assessment of numerous life history aspects in extinct organisms. Hadrosaurid dinosaurs, the dominant large-bodied terrestrial herbivores in most Late Cretaceous ecosystems, have an exceptional fossil record consisting of over 60 species and multiple ontogenetic bonebeds making them an ideal clade on which to conduct life history studies. The objectives of this thesis were to integrate new data and methods to investigate ontogenetic growth and test life history strategies in hadrosaurid populations from the Late Cretaceous of North America, with a particular emphasis on the integration of osteohistological methods with limb growth and size frequency distributions for inferring biomechanical gait shifts, growth and population dynamics, and mass death preservational patterns. The results in this thesis demonstrate that the proportions of the appendicular skeleton of hadrosaurid dinosaurs did not undergo allometric growth through ontogeny and provide no compelling evidence to support the previously hypothesized ontogenetic gait shift in hadrosaurids. Size-frequency distributions underestimate age and overestimate growth rates. However, when paired with osteohistology, the data reveal that juvenile hadrosaurids segregated from adults providing essential insight into the population dynamics of these animals. The comprehensive growth curve analysis indicates that hadrosaurids exhibited a similar growth trajectory regardless of a wide ranging asymptotic body size (~3000–6000 kg) suggesting that the clade as a whole inherited a similar growth strategy attaining adult size within 7–9 years. This thesis strongly recommends both the independent assessment and the integration of allometric scaling, size-frequency distributions, and osteohistology to provide more accurate and precise paleobiological interpretations of life history characteristics.

Department dc:contributor.department

Ecology and Evolutionary Biology

Year dc:date.issued

2018

Author dc:creator

• Wosik, Mateusz

Advisor dc:contributor.advisor

• Evans, David C

• dinosaur
• growth
• hadrosaur
• histology
• population structure
• taphonomy

Handle dc:identifier.uri

http://hdl.handle.net/1807/102954

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/102954