Monosphenodontidae

Monosphenodontidae is an extinct family of lizards belonging to the order Squamata. Fossils attributed to this family have been found in deposits dating from the Early Cretaceous to the Late Cretaceous periods. The geographic distribution of Monosphenodontidae fossils is primarily within North America and Europe, suggesting a relatively widespread presence across the Northern Hemisphere during the Mesozoic Era.

The defining characteristics of Monosphenodontidae relate to their cranial and dental morphology. They are generally recognized for possessing a single, fused element in the jaw, which is a key feature distinguishing them from some other lizard groups. Their teeth were typically pleurodont, meaning they were attached to the inner side of the jawbone, and often showed adaptations for a diet of insects or small invertebrates.

The precise phylogenetic position of Monosphenodontidae within Squamata has been a subject of ongoing scientific discussion and revision. While they share some features with certain modern lizard groups, their unique combination of traits places them as a distinct evolutionary lineage. Their extinction, like many other reptilian groups, is likely linked to the environmental changes that occurred at the end of the Cretaceous period. Further discoveries of Monosphenodontidae fossils continue to refine our understanding of their anatomy, evolutionary relationships, and paleoecology.