The bone is the supraoccipital which ossifies from two lateral centers of ossification which later fuse, rather than from a median center. No dermal parietal component is present at any stage in the so-called parieto-supraoccipital. Previous hypotheses of the homology of these elements and of additional ossifications are reviewed in light of developmental information obtained herein. No signs of ontogenetic fusion were observed in any of the purported compound elements. gyrinus (except dorsal- and anal-fin distal radials) at 14.1 mm SL. punctatus at 22.4 mm SL and almost complete in N.
Development of the skeleton is complete in I. I reexamine the homologies of bones previously hypothesized to represent compound elements in catfishes as well as an additional element only known to occur in some ictalurids.
To further our understanding of the siluriform skeleton, I document the development of the entire skeleton in two ictalurid species, Ictalurus punctatus (channel catfish) and Noturus gyrinus (tadpole madtom) from five days pre-hatch to adult. Although well documented in adults, information on skeletal development in catfishes is relatively sparse and typically focused on particular regions of the skeleton (e.g., Weberian apparatus).
The skeleton of Siluriformes is characterized by several autapomorphies, including secondary absence, extreme modification, and purported fusion of several ossifications. Nevertheless, the widespread low support and resolution at most basal nodes pose a considerable challenge in understanding major patterns of intergeneric relationships, which in turn hinders our efforts to shed critical light on the biogeographic history of the group. Our results are broadly congruent with recent studies that have uncovered rampant polyphyly within the genus Trichomycterus and provide emerging evidence, as a result of increased taxonomic representation, for geographically circumscribed subclades of Trichomycterus species.
Sononym 1.0.4 osx torrent plus#
Within Trichomycterus, we uncovered a novel clade of central Andean species and reveal a close relationship among southern Andean taxa that included a non‐monophyletic Silvinichthys, Bullockia, Hatcheria, plus a number of Trichomycterus species. Our results do not corroborate Trichomycterinae split into two reciprocally monophyletic groups, and we show strong support for a sister‐group relationship between Eremophilus mutisii and Trichomycterus bogotensis that suggests some degree of evolutionary distinctiveness for this clade of Colombian‐endemic species. Our results confirm previous findings of strong support for a monophyletic subfamily Trichomycterinae while rejecting the monophyly of its most diverse genus, Trichomycterus. This study assembled both available and novel comparative DNA sequence data inclusive of Hatcheria, Silvinichthys, and additional Trichomycterus species not represented in previous studies to form the most taxonomically comprehensive molecular dataset of the Trichomycterinae at the genus level to date. No previous studies using molecular data have included representatives of Hatcheria and Silvinichthys, and none have included dense representation of the diverse Andean species of Trichomycterus. Consensus is emerging among studies using DNA sequence data addressing problems in the taxonomy and relationships of trichomycterid catfishes, a dominant component of the Neotropical freshwater ichthyofauna, that have heretofore eluded efforts based on morphological data alone.