Diversity and ecological relationships of Cestoda and parasites of freshwater stingrays (Myliobatiformes, Potamotrygonidae), in the upper Paraná River, Brazil.

The Neotropical freshwater stingrays of genus present a unique and complex natural history and biogeographical pattern that can be traced to a marine origin and the colonization of the continental environment during the Miocene. During the evolution of potamotrygonids, several species of the parasitic fauna coevolved and co-opted concomitantly to their hosts during the colonization of the new environments. One striking example can be observed during the colonization of the upper Paraná River region.

Osteohistological characterization of notosuchian osteoderms: Evidence for an overlying thick leathery layer of skin.

Osteoderms are mineralized structures embedded in the dermis, known for nonavian archosaurs, squamates, xenarthrans, and amphibians. Herein, we compared the osteoderm histology of Brazilian Notosuchia of Cretaceous age using three neosuchians for comparative purposes. Microanatomical analyses showed that most of them present a diploe structure similar to those of other pseudosuchians, lizards, and turtles.