Was the Devonian placoderm Titanichthys a suspension-feeder?

• Main Authors: Coatham, Samuel, Vinther, Jakob, Rayfield, Emily, Klug, Christian
• Format: Other/Unknown Material
• Language: unknown
• Published: Zenodo 2020
• Subjects: baleen whales
• Online Access: https://doi.org/10.5061/dryad.9kd51c5d6

Large nektonic suspension-feeders have evolved multiple times. The apparent trend among apex predators for some evolving into feeding on small zooplankton is of interest for understanding the associated shifts in anatomy and behaviour while the spatial and temporal distribution gives clues to an inherent relationship with ocean primary productivity and how past and future perturbations to these may impact on the different tiers of the food web. The evolution of large nektonic suspension-feeders - 'gentle giants' - occurred 4 times among chondrichthyan fishes (e.g. whale sharks, basking sharks and manta rays), as well as in baleen whales (mysticetes), the Mesozoic pachycormid fishes and at least twice in radiodontan stem group arthropods (Anomalocaridids) during the Cambrian Explosion. The Late Devonian placoderm Titanichthys has tentatively been considered to have been a megaplanktivore, primarily due to its gigantic size and narrow, edentulous jaws while no suspension-feeding apparatus have ever been reported. Here the potential for microphagy and other feeding behaviours in Titanichthys is assessed via a comparative study of jaw mechanics in Titanichthys and other placoderms with presumably differing feeding habits (macrophagy and durophagy). Finite element models of the lower jaws of Titanichthys termieri in comparison to Dunkleosteus terrelli and Tafilalichthys lavocati reveal considerably less resistance to von Mises stress in this taxon. Comparisons with a selection of large-bodied extant taxa of similar ecological diversity reveals similar disparities in jaw stress resistance. Our results therefore conform to the hypothesis that Titanichthys was a suspension-feeder with jaws ill-suited for biting and crushing but well suited for gaping ram feeding. Funding provided by: Swiss National Science Foundation* Crossref Funder Registry ID: Award Number: 200020_184894 Funding provided by: Swiss National Science Foundation Crossref Funder Registry ID: http://dx.doi.org/10.13039/501100001711 Award Number: ...