Although ray-finned fishes (e.g. catfish, salmon) are the most diverse group of vertebrates on the planet today, their early evolution is poorly understood. This is because primitive fossil ray-finned fishes, the palaeoniscoids, are an understudied group. Countless palaeoniscoids remain to be described and included in analyses that investigate evolutionary relationships among extinct and extant ray-finned fishes. These extinct fishes are important because the body plan of today's fishes has originated from palaeoniscoids, and there is evidence that some are closely related to today's fishes. The goal of this project is to shed light onto the early evolution of fishes by investigating the interrelationships of palaeoniscoids in a comprehensive study. This will be accomplished with descriptions of new species from museum collections, investigations into anatomical changes in ancestral palaeoniscoids and descendants, and reconstructing evolutionary relationships among palaeoniscoids and living fishes.
Knowledge of relationships of fossil ray-finned fishes (palaeoniscoids) will provide a better understanding of the early evolution of today's living fishes. Fossil fishes most closely related to today's forms will be identified. Anatomical features identified in this project can affect many areas of study into today's fishes by identifying the ancestral condition for ray-finned fishes. In addition, lessons describing what can be learned from fossil fishes will be created for elementary school students.
Actinopterygian fishes are the most speciose vertebrates on the planet. Fossil lower actinopterygians, or non-teleostean fossil fishes, are critical to understanding the early evolution of actinopterygians but these fishes are poorly understood. This project focused on a subset of these fossil fishes, the palaeoniscoid actinopterygians. The main goal of this project was to form a better understanding of palaeoniscoids by concentrating on descriptions of new taxa, reassessments of morphological characters, and phylogenetic analyses to investigate the evolutionary relationships of taxa ranging from the Devonian to the recent. By concentrating on the morphology of these fishes and phylogenetic analyses, a greater understanding of palaeoniscoid fishes was formed The taxonomic portion of the project was successful and resulted in the description of four new taxa. One taxon described is the earliest occurrence of a specific genus in North America, and only the second discovery of this type of fish in North America. The investigations into morphological characters were also successful. A skull bone, the preoperculum, was examined across an array of Paleozoic, Mesozoic, and recent fishes. This project concluded that this cheek bone is more diverse than previously thought. It was also the first time this morphological character was examined within a phylogenetic context. These findings were presented at national and international meetings to other paleoichthyologists and published in a book series dedicated to paleoichthyology. One of the most important outcomes of this project dealt with the recognition that there is no standardization in how bones of the snout region of palaeoniscoids are identified and named. The same bone names are used to identify very different bones. This is problematic because it makes comparing taxa described by different researchers difficult, impairs our understanding of the morphological diversity of palaeoniscoids, and presents potential pitfalls when building character matrices for analyses into phylogenetic relationships. A fundamental problem with the different ways bones have been identified is that homology has not always taken into consideration. Homology refers to similarity between structures due to common inheritance. Two different organisms will have homologous structures if and only if that structure was inherited from a common ancestor. Homology is important because only homologous structures can shed light onto evolutionary relationships. This project concluded that how bones have been identified in the past is a major problem that has hindered our understanding of palaeoniscoids. To resolve this, this project produced new nomenclature rules for the identification of snout bones in palaeoniscoids. This new set of rules was founded on an attempt to identify homologous structures by basing identifications on the presence or absence of particular characters. Here, homologous structures in different taxa were identified using a specific criteria; Remane’s criteria of similarity in position and detail. This nomenclature scheme was applied to previously described palaeoniscoids to standardize the identifications and comparisons among these fishes. After this was done, patterns regarding the makeup of the snout in Devonian and Carboniferous palaeoniscoids emerged. Certain snout morphologies are present in Devonian fishes and not Carboniferous. The snouts of Carboniferous fishes are more morphologically diversity than those of Devonian fishes. These patterns were obscured because of how bone names were previously applied. Findings from this portion of the study were presented to the paleontology community at a scientific conference. This portion of the project will be submitted for publication in a symposium volume dealing with advances in morphological studies of fishes. The findings of this portion of the study do not just apply to palaeoniscoids and the call for the identification of bones based on homology applies to many other fields. With new insights into taxa and characters, phylogenetic analyses were performed to investigate the evolutionary relationships of palaeoniscoid fishes. A morphological character matrix was built. The snout characters and codings used in this matrix reflected the nomenclature scheme described above. Actinopterygian fishes from the Devonian to the Recent were coded. The character matrix was analyzed using both Parsimony and Bayesian analyses. This study was the first time Bayesian methodologies were employed to study the relationships of lower actinopterygians. Bayesian analyses did not recover a monophyletic group, but the parsimony analyses did. Parsimony analyses recovered a monophyletic Palaeoniscomorpha and Palaeonisciformes; therefore this analysis resulted in dismantling the paraphyletic grouping of palaeoniscoid fishes. These monophyletic groups were supported by characters that have been traditionally associated with palaeoniscoid fishes. Overall, this project represents the largest investigation into the relationships of lower actinopterygians to date. Major results include a better understanding of the taxonomic diversity of palaeoniscoid fishes and suites of morphological characters. These insights positively affected investigations into the relationships of palaeoniscoids. These results provide insight into where future work should be directed. More emphasis must be placed on the reexamination of morphological characters and attention to homology. The results of this project suggest that these steps are key to our understanding of palaeoniscoids.
