Unusual kinematics and jaw morphology associated with piscivory in the poeciliid, Belonesox belizanus

Lara A. Ferry-Graham, L. Patricia Hernandez, Alice C. Gibb, Cinnamon Pace

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Piscivory in fishes is often associated with the evolution of highly elongate jaws that achieve a large mouth opening, or gape. Belonesox belizanus, the pike killifish, has independently evolved this morphology, which is derived from short-jawed poeciliids within the Cyprinodontiformes. Using kinematic analysis of high-speed video footage, we observed a novel aspect of the elongate jaws of Belonesox; the premaxilla rotates dorsally during mouth opening, while the lower jaw rotates ventrally. Anatomical study revealed that this unusual motion is facilitated by the architecture of the premaxillomandibular ligament, prominent within cyprinodontiforms. In Belonesox, it allows force to be transferred from the lower jaw directly to the premaxilla, thereby causing it to rotate dorsally. This dorsal rotation of the premaxilla appears to be assisted by a mediolateral twisting of the maxilla during jaw opening. Twisting maxillae are found in members of the group such as Fundulus, but are lost in Gambusia. Models revealed that elongate jaws partially account for the enlarged gape, but enhanced rotation at the quadrato-mandibular joint was equally important. The large gape is therefore created by: (i) the convergent evolution of elongate jaws; (ii) enhanced jaw rotation, facilitated by loss of a characteristic cyprinodontiform trait, the lip membrane; and (iii) premaxilla rotation in a novel direction, facilitated by the retention and co-option of additional cyprinodontiform traits, the premaxillomandibular ligament and a twisting maxilla.

Original languageEnglish (US)
Pages (from-to)140-147
Number of pages8
Issue number3
StatePublished - May 2010


  • Cyprinodontiforms
  • Elongate jaws
  • Mouth opening
  • Pike killifish
  • Premaxillary rotation

ASJC Scopus subject areas

  • Animal Science and Zoology


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