Who are the ancestors of rats? - briefly
Rats are members of the muroid superfamily, which originated from early Paleocene rodents such as ischyromyids and primitive muroids. These early forms evolved into the modern Muridae family that includes the genus Rattus.
Who are the ancestors of rats? - in detail
Rats belong to the family Muridae, subfamily Murinae, which emerged from early muroid rodents during the Paleogene. The earliest recognized muroids appear in the late Paleocene (≈58 million years ago) and include genera such as Paramys and Eothenomys. These small, squirrel‑like mammals exhibit dental patterns—high‑crowned molars with three primary cusps—that foreshadow the occlusal morphology of modern murids.
During the Eocene, diversification gave rise to the clade Ischyromyidae, whose members display a blend of primitive and derived traits. Fossils attributed to Ischyromys and Plagiodontia reveal elongated incisors and a nascent diastema, features that later become characteristic of murine rodents. Molecular clock analyses place the split between the lineage leading to rats and that leading to mice at roughly 12–15 million years ago, supporting the fossil record of Cricetidae‑like forms that co‑existed with early murines.
The Miocene epoch records the appearance of the genus Rattus’s direct precursors. Species such as Rattus praetextus and Rattus cf. norvegicus are documented in European deposits dated 10–5 million years ago. Their skeletal remains show a fully developed auditory bulla and a robust zygomatic arch, indicating advanced gnawing capabilities and enhanced auditory perception—adaptations that facilitated the ecological success of later rats.
Late Pliocene and early Pleistocene fossils, notably Rattus exulans and Rattus rattus ancestors, exhibit the full suite of murine characteristics: a pronounced infraorbital foramen, a shortened rostrum, and a highly specialized dentition pattern (1 incisor, 0 canine, 2 premolars, 3 molars). These traits underpin the rapid expansion of rats into diverse habitats and their eventual commensal relationship with humans.
In summary, the evolutionary lineage of rats traces from early Paleocene muroids through Eocene ischyromyids, Miocene murine precursors, and culminates in Pliocene–Pleistocene species that possess the definitive anatomical features of contemporary rats.