Monoissa

Monoissa is a genus of extinct cartilaginous fish that lived during the Carboniferous period. These ancient sharks are primarily known from fossilized teeth and fin spines, which are relatively common in certain Carboniferous marine deposits. The teeth of Monoissa are often described as small and serrated, suggesting a diet of smaller invertebrates or possibly fish. The fin spines are also a distinctive feature, typically being slender and ridged.

Fossil discoveries indicate that Monoissa inhabited shallow marine environments. Their small size, estimated to be around 1 to 2 meters in length, likely placed them as prey for larger predatory sharks of the time. The classification of Monoissa has been debated among paleontologists, with some placing it within the order Hybodontiformes, a group of extinct sharks that were abundant during the Mesozoic Era. However, its early appearance in the Carboniferous suggests it may represent an ancestral form or a separate lineage within the broader cartilaginous fish evolutionary tree. The limited fossil record makes a precise phylogenetic placement challenging. Nevertheless, Monoissa provides valuable insights into the diversity and evolution of sharks during the Paleozoic era.