Callichthyidae

Abstract: The current hypothesis of relationship among the Loricarioidea (a diverse group of Neotropical catfishes) is used as the basis for a case study of historical transformation in the feeding mechanism in this monophyletic clade. The historical approach to functional mor- phology is discussed and is used in this analysis as a means of examining the evolutionary sequence of structure-function transformation. The distribution of structural novelties in the feeding mechanism and their functional correlates are mapped onto the current hypothesis of loricarioid phylogeny. Three major steps in the transformation of the feeding mechanism are identified. The first was the acquisition of highly mobile premaxillae in the lineage leading to the Callichthyidae, Astroblepidae, and Loricariidae. The second step occurred in the lineage leading to the Astroblepidae and Loricariidae: both families possess highly mobile premaxillae with new muscular insertions and movements that are independent of maxillary mobility. Another specialization at this level was the loss of the interoperculo-mandibular ligament and the ac- quisition of independent bilateral lower jaw mobility via loss of the tight connection between right and left sides of the lower jaws. The third major step occurred in the lineage leading to the Loricariidae. Further subdivision of the jaw adductor muscle resulted in an additional mesial subdivision with a direct muscle insertion onto the premaxillae. A neomorphic structure, the intermandibular cartilage plug (also shared by astroblepids) is specialized in loricariids with a direct attachment to the hyoid, resulting in an additional biomechanical linkage between the hyoid and mandible. A major trend in the evolution of the loricarioid feeding mechanism is the increase in the number of biomechanical linkages. This is hypothesized to be causally related to morphological and trophic diversity. Two explicit predictions are made testing the hypothesis that decoupling of primitively constrained biomechanical elements is related to increased mor- phological and functional diversity in descendant species. (Historical analysis; feeding mecha- nisms; evolutionary morphology; catfishes; biomechanics.) The analysis of pattern and process in

Abstract: A new species of Corydoras is described from the upper Rio Machado, Rio Madeira basin, Rondonia State, Brazil. The new species can be distinguished from its congeners by the absence of contact between the posterior process of the parieto-supraoccipital and the nuchal plate; a ventral laminar expansion of the infraorbital 1 conspicuously developed; and the posterior margin of the pectoral-fin spine with serrations along almost of its entire length, only lacking in the distal portion. Additionally, Corydoras hephaestus possesses dorsal and pectoral spines short, and exhibits an unusual color pattern in life. The conservation status of the new species and other endemic species are briefly commented.

Abstract: Three new species of Hyphessobrycon (Characiformes: Characidae) are described from the upper rio Araguaia basin. Hyphessobrycon langeanii n. sp. is distinguished from all congeners by the presence of a well-defined, round humeral spot, a reticulate color pattern, a broad, horizontally-elongate caudal-peduncle blotch, and a relatively wide, faint midlateral dark stripe. Hyphessobrycon eilyos n. sp. is distinguished from all congeners by the absence of humeral and caudal spots; by the presence of numerous dark chromatophores on the lateral surface of the body, intensely concentrated on the ventral region from the pelvic-fin origin to the end of the caudal-fin base, dorsal, adipose, and caudal fins with carmine red pigmentation in life; and the presence of 7-11 maxillary teeth. Hyphessobrycon weitzmanorum n. sp. is distinguished from all congeners by the combination of the possession of two humeral spots and a general dark color pattern. These three new species, along with Creagrutus molinus (Characidae), Apareiodon tigrinus (Parodontidae), Aspidoras velites (Callichthyidae), an undescribed member of the Hypoptopomatinae (Loricariidae), Cnesterodon septentrionalis (Poeciliidae), and Simpsonichthys cholopteryx (Rivulidae), all of which are apparently endemic of the upper rio Araguaia, indicate that this area is a previously unrecognized area of endemism.