"Order" - what is it, definition of the term
In biological classification, the rank situated between class and family groups together families that share a set of fundamental morphological and genetic traits; this category unites organisms such as rats and mice, which, despite belonging to different families, are placed together because they exhibit the characteristic rodent dentition, skull structure, and evolutionary lineage that define the same taxonomic grouping.
Detailed information
The taxonomic rank that groups rats, mice and related mammals is the mammalian clade Rodentia. It occupies the level directly below the class Mammalia and above families such as Muridae. This classification unites species that share a distinctive set of morphological and genetic features.
Key characteristics defining this group include:
- a single pair of continuously growing incisors in each jaw,
- a gap (diastema) separating incisors from cheek teeth,
- robust mandibles adapted for gnawing,
- a highly developed auditory bulla,
- a tendency toward high reproductive rates and short gestation periods.
Rodentia comprises over 2,200 extant species, representing roughly 40 % of all mammalian diversity. Members inhabit virtually every terrestrial ecosystem, from tropical rainforests to arid deserts and urban environments. Their ecological roles range from seed dispersers and soil engineers to prey for numerous predators.
Evolutionary history traces back to the early Paleocene, with fossil records documenting rapid diversification during the Eocene and Oligocene. Adaptive radiation produced a wide array of body sizes, dietary specializations, and locomotor strategies, underpinning the group's resilience and global distribution.