Abstract
Conodont elements are distinguished by their high morphological diversity and evolution, but their function has been few investigated. In particular, P1 elements were proposed to be analogous to mammal molars based on a positive allometric relationship between their platform length/area and their total length, which was previously identified in Carboniferous taxa. Here we apply the same method to test the null hypothesis of isometric growth in two Late Triassic taxa, Metapolygnathus communisti and Epigondolella rigoi, using 3D models of growth series. We further test if these co-occurring taxa showed the same growth allometry, reflecting overlapping trophic niches. In both species platform length and platform area showed positive allometry with respect to element length, which is consistent with a molar-like function. The allometric relationship did not differ significantly between both Late Triassic taxa, which mean they rather occupy the same trophic niche. We further tested the overlap in the trophic niches using Dirichlet Normal Energy, a dental topographic analysis. Adult specimens of E. rigoi showed higher DNE values than M. communisti’s, consistent with a capacity to break harder food and so having a different diet. Based on DNE values available for primates, adult values for E. rigoi were similar to those reported for insectivores or folivores; for folivores or omnivores for adults M. communisti. This means that these conodont species might have eaten food that required analogous breaking forces. Diet differentiation within this broad niche supports trophic diversification as an important driver of the remarkable disparity of conodont elements.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Analyses were revised as well as the Results and Discussion part. The main conclusions remain the same. Table 2 and Table 3 added. Only Figure 1 remains, the other were either modified, new or deleted.