Incisor overgrowth and molar malocclusion in Thaptomys nigrita (Rodentia: Sigmodontinae)

Rodents possess continuously growing incisors requiring balanced wear to avoid dental disorders. While common in captivity, dental anomalies are rarely reported in wild populations. This study reports cases in wild Thaptomys nigrita from three populations in southeastern Brazil, including the first record of incisor overgrowth in a wild sigmodontine. Morphological and age analyses revealed malocclusion, molar rotation, root exposure, interdental spacing, and alveolar bone loss, sometimes resembling periodontitis. Severe incisor hypertrophy was linked to trauma or occlusal imbalance. Findings suggest mechanical, traumatic, bacterial, or genetic origins, and indicate such anomalies may be more frequent in wild rodents than previously recognized.