Titanichthys: Devonian-Period Armored Fish was Suspension Feeder
Titanichthys lived in shallow seas of Morocco, North America and Europe some 380 million years ago (Devonian period).
It likely exceeded 5 m in length and its lower jaw reached lengths exceeding 1 m. However, unlike its similarly giant contemporary Dunkleosteus, there is no previous evidence of how Titanichthys fed.
University of Bristol paleobiologist Samuel Coatham, University of Zurich’s Professor Christian Klug and their colleagues sought to investigate the question indirectly, using biomechanical analysis to compare the lower jaw of Titanichthys with those of other species.
“We have found that Titanichthys was very likely to have been a suspension-feeder, showing that its lower jaw was considerably less mechanically robust than those of other placoderm species that fed on large or hard-shelled prey,” Coatham said.
“Consequently, those feeding strategies (common amongst its relatives) would probably have not been available for Titanichthys.”
The scientists analyzed a nearly complete lower jaw of Titanichthys found in the Southern Maïder basin, Morocco.
They tested the resilience of their specimens by virtually applying forces to the jaws, using a technique called finite element analysis (FEA) to assess how likely each jaw was to break or bend.
This revealed that the lower jaw of Titanichthys was much less resistant to stress and was more likely to break than those of the other placoderm species, such as Dunkleosteus.
Therefore, the jaw of Titanichthys probably would not have been able to withstand the higher stresses associated with their strategies of feeding on large prey, which thus exert more mechanical stress on the jaws.
This pattern was consistent in both sharks and whales, with the suspension-feeder proving less resistant to stress than the other species within the same lineage.
Further analyses comparing the distribution of stress across the jaws showed similar patterns in Titanichthys and the basking shark, reinforcing this comparison.
“Our methods could be extended to identify other such species in the fossil record and investigate whether there were common factors driving the evolution and extinction of these species,” Coatham said.
“We suggest a link between oceanic productivity and the evolution of Titanichthys, but this should be investigated in detail in the future. An established link could have implications for our understanding of the conservation of modern suspension-feeders.”
Samuel J. Coatham et al. Was the Devonian placoderm Titanichthys a suspension feeder? R. Soc. open sci 7 (5): 200272; doi: 10.1098/rsos.200272