Femoral ontogeny and locomotor biomechanics of Dryosaurus lettowvorbecki (Dinosauria, Iguanodontia)

RONALD E. HEINRICH, CHRISTOPHER B. RUFF, DAVID B. WEISHAMPEL

Research output: Contribution to journalArticlepeer-review

Abstract

Femoral ontogeny in the iguanodontian dinosaur Dryosaurus lettowvorbecki (Late Jurassic, Tanzania) is analysed biomechanically using principles of beam theory. Statistically significant differences in cross‐sectional properties are found between animals of differing size, reflecting alterations to both the relative amount and distribution of cortical bone during growth. Two explanations are suggested to account for these modifications in bone architecture: (1) increasing mechanical loads related to increasing body size, and (2) changes in the orientation of these loadings associated with a caudal shift of the centre of gravity. It is argued that D. lettowvorbecki hatchlings were not bipedal as generally presumed but obligate quadrupeds. Based on avian growth rates, the transition from quadrupedality to habitual bipedalism is estimated to have occurred within several months of hatching. The biomechanical approach employed here contributes new insight into ontogeny of locomotion in D. lettowvorbecki and provides additional ways of analysing ontogenetic processes among extinct and living species. Ontogenetic changes in femoral morphology and locomotion were analysed in the iguanodontian dinosaur Dryosaurus lettowvorbecki using cross‐sectional data and applying principles of beam theory. The results presented here suggest that locomotor ontogeny in D. lettowvorbecki was more complicated than has generally been recognized. The percentage cortical area (a measure of the relative amount of bone) increases abruptly over a relatively short period during early ontogeny and then remains uniform during subsequent increases in body size. Modifications in cross‐sectional shape also occur with increasing size, as demonstrated by differences in second moment of area ratios. The patterns of change in these properties indicate that the orientation of mechanical loadings acting on the femur of D. lettowvorbecki differed at various stages of growth and development. It is suggested that the alterations in femoral architecture described here reflect a shift from quadrupedality to bipedality early in the ontogeny of this animal.

Original languageEnglish (US)
Pages (from-to)179-196
Number of pages18
JournalZoological Journal of the Linnean Society
Volume108
Issue number2
DOIs
StatePublished - Jun 1993

Keywords

  • Cross‐sectional geometry
  • bipedalism
  • development

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology

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