Data for: Is the hyoid a constraint on innovation? A study in convergence driving feeding in fish-shaped marine tetrapods

The hyoid apparatus is essential for underwater feeding in marine tetrapods, but it is unclear whether this complex has evolved as convergently as other traits, such as dentition or locomotion. Here we compare the ossified hyoid elements in ophthalmosaurid ichthyosaurs and odontocete cetaceans, two groups with an overall similar body shape, to understand whether the hyoid elements show any signs of convergence in the context of feeding. We examined three types of data (size, morphology, and internal bone microstructure) in ophthalmosaurid and odontocete taxa in which these elements are preserved. Our data show that ichthyosaurs never experienced a shift in feeding mode, which might indicate that their hyoid apparatus never adapted to suction feeding. Also, the internal microstructure of the two animal groups differs, where the odontocetes have an overall less compact structure, ophthalmosaurid ichthyosaurs have cancellous inner cones in an outer, more compact sheath. These differences a..., Thirteen ophthalmosaurid specimens with one or both hyoid rods preserved were studied (Table 1), out of which 11 preserved at least one complete hyoid so that measurements could be used for calculations. For eight out of the thirteen specimens, anterior-posterior orientation was known. To compare the ophthalmosaurids to the published data on non-ophthalmosaurids (Triassic-Middle Jurassic; Motani et al. 2013), the same measurements were collected from publications, colleagues and museum visits; anteroposterior length in a straight line (HL), and width taken half-way (HW). Both were log10-transformed for analysis. Hyobranchial robustness was calculated as in Motani et al. 2013 log10 HL: log10 HW, similar to the “stylohyal robustness index” in Bloodworth and Marshall (Bloodworth and Marshall 2007) and in Johnston and Berta (2010). Among the ophthalmosaurid specimens with hyoids (Table 1), none were preserved in articulation in such a way that mandibular width (MW of Motani et al. 2013) nor..., In this Dryad submission:
- supplementary text files with data on morphology of ichthyosaur hyoids (two word files)
- supplementary table with measurement data on cetaceans (excel file)
- the ichthyosaur measurement data also including non-ophthalmosaurids, which are the underlying data for these calculations (excel file),