The levels of homoplasy and phylogenetic reliability of different types of data sets have since long intrigued evolutionary scientists. This paper provides, to the author's knowledge, the first assessment of the relative contribution of a large set of myological and osteological characters in simultaneous phylogenetic analyses. The biological taxon used as a case study for this comparison was the highly diverse and cosmopolitan teleost Siluriformes (catfishes) which, with 34 families, about 437 genera and more than 2700 species, represents about one third of all freshwater fishes and one of the most diverse vertebrate groups. Such a direct comparison of the relative contribution of these two types of data sets has the advantage that the homoplasy levels and the phylogenetic trees being compared refer to the same group and, more importantly, to the very same terminal taxa. The overall analysis of the results presented in this work seems to indicate that: (1) osteological structures display a greater morphological variation than myological ones; (2) this difference (which is very likely overenhanced by the fact that the phylogenetic variation of osteological structures has historically been the subject of many more studies and descriptions than myological ones) is particularly notable in small taxa, such as genera or species; (3) myological characters provide, however, a high proportion of informative characters for disclosing the relationships between larger taxa, and, thus, for disclosing the phylogeny of the higher clades in which these taxa are included. These results raise some puzzling, general questions. For instance, what are the reasons for the seemingly greater morphological variation of osteological structures? And why is this greater morphological variation of osteological structures in relation to myological structures particularly pronounced in low ranking taxa? Does natural selection eventually act, in certain cases, more on bones than on muscles? Is the development of myological structures eventually more constrained than that of osteological features? What explains the apparently high reliability of muscular characters to disclose the higher-level phylogeny of higher taxa? More direct comparisons, either of other major groups of teleosts or of vertebrates in general, are clearly needed to infer if the patterns found in the direct comparison of this work correspond to a more general phylogenetic pattern, or instead refer to a particular situation found in the order Siluriformes.
The wide geographical distribution of the mainly freshwater catfishes has long intrigued the scientific community. This work provides a new insight into the phylogeny and the puzzling biogeographical distribution of catfishes. The important implications for teleost biogeography and plate tectonics are discussed. The results of the author's cladistic study on catfish higher level phylogeny, together with a revision of the data available concerning different fields such as palaeobiogeography, phylogeny, ecology and molecular biology, as well as the growing evidence supporting the existence of some remaining Pangean connections between Gondwana and Laurasia extending into the Early Cretaceous, strongly support a rather complex biogeographic scenario with multiple pre-drift and post-drift continental dispersions, vicariances, and, possibly, some marine migrations. According to this scenario: 1) catfishes originated in the South American region at a moment when there were still some remaining Pangean connections between Gondwana and Laurasia; 2) after this, there was a relatively rapid pre-drift continental dispersion of several, but not all, main groups of Siluriformes from the South-American region to Africa and other Gondwanan areas, with some of those groups succeeding in radiating ulteriorly via the remaining continental Pangean connections between Gondwana and Laurasia to this latter super-continent; 3) the final separation between Laurasia and Gondwana, and posteriorly between the regions constituting each of these super-continents, contributed to important vicariant events; 4) this scenario was still further complicated by numerous events such as the collision of India with Asia, the re-establishment of certain land connections between previously separated continents (e.g., between the Americas), and eventually also by some marine migrations, thus explaining the highly complex biogeographical distribution of the Siluriformes. In sustaining such a scenario, this work thus supports that, contrary to what is often accepted, some groups of 'modern teleosts' did have a Pangean origin.
The Osteichthyes, including bony fishes and tetrapods, is a highly speciose group of vertebrates, comprising more than 42000 living species. The anatomy of osteichthyans has been the subject of numerous comparative studies, but these mainly concern osteological structures; much less attention has been paid to muscles. In fact, the most detailed and comprehensive myological comparative analyses that were actually based on a direct observation of representatives of various major osteichthyan groups were provided various decades by authors such as Luther, Kesteven and principally Edgeworth. The present work provides an updated discussion of the homologies and evolution of the osteichthyan mandibular, hyoid and hypobranchial muscles, based on the author's own analyses and on a survey of the literature, both old and recent. The risks of discussing muscle homologies on the basis of a single line of evidence, even when it concerns innervation or development, is emphasized. It is stressed than only by taking into consideration various lines of evidence (e.g. developmental biology, comparative anatomy, functional morphology, paleontology, molecular biology, experimental embryology, innervation and/or phylogeny) it is possible to establish well-grounded hypotheses of muscle homology.
The cephalic and pectoral girdle structures of the South African catfish Austroglanis gilli are described and compared with those of other catfishes, either studied by us or described in the literature, as the foundation for a discussion on Austroglanididae autapomorphies, and also on the phylogenetic relationships between the austroglanidids and the other catfishes. Our observations, comparisons, and bibliographical overview revealed only two Austroglanidae autapomorphies, namely: 1) the peculiarly shaped, posteriorly bifurcated sesamoid bone 1 of the suspensorium; and 2) the markedly broad fourth basibranchial. Another feature, the marked lateral bifurcation of the anterodorsolateral laminar projection of the sphenotic bone, may eventually constitute an additional austroglanidid autapomorphy, but, perhaps more reasonably, be a synapomorphic feature to support a close relationship between A. gilli and A. barnardi. With respect to the phylogenetic position of the Austroglanididae within the Siluriformes, these fishes seem to be closely related to the ictalurid and the cranoglanidid, and particularly to the ariid and the claroteid catfishes.
The cephalic and pectoral girdle structures of the pseudopimelodin Batrochoglanis raninus are described and compared to those of a representative of another pseudopimelodin genera, namely Microglanis cottoides, as well as to several other pimelodid and non-pimelodid catfishes, as the foundation for a discussion on the synapomorphies and phylogenetic relationships of the Pseudopimelodinae. Our observations and comparisons pointed out two new, additional features that could represent potential Pseudopimelodinae synapomorphies: 1) mesethmoid markedly bifurcated anteriorly; 2) spoon-shaped autopalatine with a somewhat roundish, markedly enlarged dorsoventrally, posterior tip. In addition, our observations and comparisons indicate that the subfamilies Pseudopimelodinae, Pimelodinae and Heptapterinae do constitute a monophyletic assemblage, and, thus, contradict the commonly accepted idea that the family Pimelodidae is a polyphyletic group.
The osteological and myological structures of the cephalic region and pectoral girdle of the Asiatic catfish Heteropneustes fossilis are described and compared with those of several other catfishes, as the foundation for an analysis on the phylogenetic relationships of the genus Heteropneustes. Our observation and comparisons support a close relationship between Heteropneustes and the clariid catfishes. More specifically, the present study supports De Pinna's 1993 study, according to which Horaglanis and Uegitglanis, two genera commonly included in the family Clariidae, are the successive sister-groups of a monophyletic clade composed by the genus Heteropneustes and the remaining clariid genera.
The cephalic and pectoral girdle structures of the auchenipterid Centromochlus heckelii (Centromochlinae) are described and compared with those of two representatives, Auchenipterus dentatus and Ageneiosus vittatus (Auchenipterinae), of the other auchenipterid subfamily, as well as with several other catfishes, as the foundation for a discussion on the synapomorphies and phylogenetic position of the Auchenipteridae. Our observations and comparisons support the idea that the Auchenipteridae and the Doradidae are sister-groups, and also that the clade formed by these two Neotropical families is closely related to the African mochokids. In addition, our observations and comparisons identified a potentially new auchenipterid synapomorphy, maxillary markedly elongated proximo-distally.