DuToit, AlexanderShort, GrahamDonatelli, CassandraCohen, KarlyHolzman, Roi2025-10-162025-10-162025https://hdl.handle.net/1773/54154Syngnathoidei, a diverse suborder of syngnathiform fish, include the families Aulostomidae and Fistularidae (cornetfish and trumpetfish), Centriscidae (snipefish and shrimpfish), Solenostomidae (ghost pipefish), and Syngnathidae (seahorses, pipefish, and seadragons). These specialized suction feeders are capable of capturing small zooplankton with remarkable speed. These rapid feeding strikes are powered by elastic energy stored in the epaxial tendons, which is released during prey capture. In seahorses (genus Hippocampus), this system is further enhanced by an elongated sternohyoideus tendon, creating a secondary spring that supplements the epaxial system. The effect of this increasing functional complexity on the wider mechanical linkage system remains unclear in this morphologically diverse clade. Here, we used μCT scan data to measure functionally relevant bone lengths across 30 syngnathiform species from 5 families. We then compared those lengths across a phylogeny to determine where certain features involved in the suction feeding system evolved. We found significant correlations between various functional measurements and identified a robust phylogenetic signal for urohyal length. This marks a transition from a one to two-spring system between pipefish and seahorses, as an elongated sternohyoideus tendon replaces the shortened urohyal bone. We also report ossification of the epaxial tendon in several closely related pipefishes, a feature that may constrain their ability to generate high-powered feeding strikes relative to other lineages.en-USsyngnathiformAulostomidaeFistularidaecornetfishtrumpetfishCentriscidaesnipefishshrimpfishSyngnathidaeseahorsepipefishseadragon