Supernumerary cranial bone occurrences within coyotes (Canis latrans)

Activity: Talk typesOral presentation


Wormian bones, also known as intrasutural bones, are supernumerary bones that variably develop from separate ossification centers within the sutures and fontanelles of the skull. Wormian bone etiology is not definitively understood, as pathological, mechanical, and genetic hypotheses have been suggested. The majority of research regarding Wormian bones has been done on humans and few studies have systematically examined non-human animals. To fill this gap in knowledge, we extensively surveyed coyote (Canis latrans) specimens, which are plentiful in museum collections. Here, we aim to gain insight regarding intraspecific variation of Wormian bones. C. latrans is a carnivorous canid that is well-suited for this study because it allows comparisons to other previously surveyed carnivoran taxa that allow us to test for common correlations between the presence and anatomical location of Wormian bones and stresses or other internal or external factors induced by a carnivorous diet. We hypothesize that the locations of Wormian bones within C. latrans and other carnivorans will be correlated with their phylogenetic relationships or ecological roles, contrasting with our null hypothesis of a random distribution of Wormian bone occurrences.

We systematically examined 239 complete skulls of C. latrans in the Oklahoma State University Collection of Vertebrates for occurrences of Wormian bones. When found, the Wormian bone’s suture location was recorded along with the specimen’s sex and collection locality if available. Our location categories were based on anatomical suture (i.e: coronal, sagittal, frontal) or fontanelles (i.e lambda, bregmatic) with a total of 12 categories.

Out of the 239 specimens examined, 29 had at least one Wormian bone, which is 12.18% of our sample. The most represented categories were the frontal-palatine (20.6%), the maxilla-frontal (13.8%), and the coronal (10.3%). Our data differs from a study on bobcats (Lynx rufus) that found bregmatic bones in 11.6% of the total sample, while we only found a 0.4% occurrence rate in C. latrans. We found a higher occurrence of all Wormian bones in coyotes than a previous study that found a rate of 5.20% in canids. However, this study did not specify which species were examined and only had a sample size of 19. We fail to reject the null hypothesis that our results deviate from a random distribution of Wormian bones across observed sutures. Additionally, we found no difference in the occurrence rate of Wormian bones for sex or collection locality.

This is the first large systematic study of non-human Wormian bones that accounts for species, sex, collection locality, and multiple suture locations. Our results show that there is no potential bias towards suture location of Wormian bones in coyotes and therefore no strong correlations can be made with localized variables acting upon particular sutures.

Future work will involve examining other taxa for comparison in order to evaluate Wormian bone proportions across the mammalian clade.
Period15 Feb 2024
Event title
Oklahoma State University Center for Health Sciences Research Week 2024
Event typeConference
LocationTulsa, United States, OklahomaShow on map


  • skull
  • coyote
  • anatomical