April 2023: publication Diversity
Living Taxa and Their Importance in Understanding the Extinct Diversity: A Look at Polypterid Pinnules
The polypteriformes are a small group of archaic-looking African fishes with thick, enameled scales and distinctive spines, the pinnules, which carry a series of small dorsal fins. Their history is very ancient and they are the sister group to all other bony fish. As such, the study of their past diversity is interesting but is hampered by a fossil record that is difficult to exploit because it is essentially made up of isolated scales and pinnules. Previous studies suggest that pinnules have unique characteristics that allow species identification, but intra-individual variability has little or not considered.
The present work aims to test their diagnostic relevance in a present-day species before studying the morphology of fossil pinnules in more detail. We describe the intra-individual and intraspecific morphological variation of pinnules in the type species of the family, Polypterus bichir.
We find (1) that intra-individual variability relates to the anteroposterior axis of the dorsal fin, (2) that morphological differences between and within individuals overlap with those proposed to distinguish species.
We conclude that most of the descriptors used so far to distinguish species on the basis of their pinnae are not robust; only some can be retained and other approaches need to be developed to interpret the fossil record of polypteriformes.
References
Coelho M.V., Cupello C., Brito P.M., Otero O. 2023 – Living Taxa and Their Importance in Understanding the Extinct Diversity: A Look at Polypterid Pinnules – Diversity 2023, 15, 517 – https://doi.org/10.3390/d15040517