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Actinopteri - Characiformes - Cynodontidae
Canine teeth large, bladelike, labiolingually compressed; sharp, raised cutting edge along midline of symphyseal face and apex, cutting edge placed more labially on articular face. Cutting edge finely and regularly serrate on IGM 183259 (fig. 5.4A); cutting edge sharp and nonserrace on IGM 183692 (fig. 5.4B).
The two fragmentary specimens are identified as the greatly enlarged mandibular canines of Hydrolycus based on their distinctive form, large size, and sharp cutting edges. The serrated cutting edge of IGM 183259 is matched exactly by the unerupted and recently erupted mandibular canines of modern specimens. The unserraced cutting edge of IGM 183259 is like those of the erupted and worn teeth of the saine modern specimens. In addition to two nominal species of Hydrolycus (H. scomberoides and H. pectoralis) there are at least two undescribed species (N. Menezes pers. comm.). Skeletal material of only H. scomberoides was available for comparison with the fossils. Because it is not known if there are interspecific differences in the large canine teeth, the fossils are not assigned at the species level.
Smaller canine teeth (fIg. 5.4C) with flattened labial sides, rounded lingual sides, and nonserrate cutting edges displaced laterally are common fossils in the Honda Group beds. These teeth are identical to the medium and small canines of Hydrolycus and also to chose of Cynodon gibbus and Rhaphiodon vulpinus, the other two taxa of the Cynodontidae. Identification of these smaller canines below family level is not possible.
Hydrolycus is widely distributed in the Orinoco and Amazon drainages and the Guiarias. These fishes are absent from the present Magdalena region. Hydrolycus are large pelagic piscivores found in big rivers and open-water lakes. The immense mandibular canines are presumably used to injure prey.
If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.