Intraspecific variation and directional casque asymmetry in adult southern cassowaries (Casuarius casuarius)

Todd L. Green, David Ian Kay, Paul M. Gignac

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


The cranial casques of modern cassowaries (Casuarius) have long intrigued researchers; however, in-depth studies regarding their morphological variation are scarce. Through visual inspection, it has been recognized that casque variability exists between conspecifics. Understanding casque variation has both evolutionary and ecological importance. Although hypothesized to be targeted by selection, intraspecific casque variation has not been quantified previously. Through a large sample of C. casuarius (n = 103), we compared casque shape (lateral and rostral views) between sexes and between individuals from non-overlapping geographical regions using two-dimensional (2D) geometric morphometrics. We found no statistically significant differences between the casque shape of females and males and few substantial shape differences between individuals from different geographic areas. Much of the intraspecific variation within C. casuarius is due to casque asymmetries (77.5% rightward deviating, 20.7% leftward deviating, and 1.8% non-deviating from the midline; n = 111), which explain the high variability of southern cassowary casque shape, particularly from the rostral aspect. Finally, we discuss how our non-significant findings implicate social selection theory, and we identify the benefits of quantifying such variation for further elucidating casque function(s) and the social biology of cassowaries.

Original languageEnglish
Pages (from-to)951-965
Number of pages15
JournalJournal of Anatomy
Issue number4
StatePublished - Oct 2022


  • cranial structure
  • geometric morphometrics
  • paleognathous birds
  • phenotypic variation
  • shape analysis
  • social selection
  • theropod
  • visual display


Dive into the research topics of 'Intraspecific variation and directional casque asymmetry in adult southern cassowaries (Casuarius casuarius)'. Together they form a unique fingerprint.

Cite this