Affiliation:
1. Life Sciences Building, University of Bristol, 24 Tyndall Avenue, Bristol, UK
2. Paläontologisches Institut und Museum, Universität Zürich, Karl-Schmid-Strasse 4, 8006 Zürich, Switzerland
Abstract
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 four 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 reveal 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.
Cited by
10 articles.
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