Phylogenetic Tree of Rodents

1. Desmarest’s hutia
2. Degu
3. Coypu, or nutria
4. Chinchillas
5. North American porcupine
6. Domestic guinea pig
7. Patagonian mara
8. Capybara
9. Naked mole rat
10. Porcupines
11. Eurasian beaver
12. South African springhare
13. Great jerboa
14. Hamsters
15. Mouse-like hamster
16. Muskrat
17. House mouse
18. Eurasian harvest mouse
19. Striped field mouse
20. Brown rat
21. Cairo spiny mouse
22. Gerbils
23. Edible dormouse
24. Chacoan mara
25. Marmots
26. Typical striped grass mouse
27. Red acouchi
28. Lowland paca
29. Harris's antelope squirrel
30. Four-striped grass mouse
31. Northern Luzon giant cloud rat
32. Malagasy giant rat
33. Yellow steppe lemming
34. Cactus mouse
35. Rock cavy
36. Eurasian red squirrel
37. Eastern gray squirrel
38. Woodland dormouse
39. Ring-tailed lemur
40. Common gundi
41. Northern viscacha
42. Syrian hamster
43. Аustralian water rat
44. European water vole
45. Neumann’s Grass Rat

Order Rodents Rodentia

With over 2,500 living species, rodents comprise more than one third of all mammalian species. Rodents are found worldwide (except in Antarctica and on some islands). Most rodents are small animals with body sizes ranging from 5 cm in some birch mice to 130 cm in the capybara. All rodents share one characteristic that distinguishes them from other mammals: they have specific dentition. All of them have one pair of upper and one pair of lower incisors. These teeth are large and curved; they are eroded and grow continuously, with the growth rate reaching 0.8 mm per day (in beavers). Only the front surface of these teeth has enamel, while the back surface consists of softer dentine, which is eroded by constant gnawing, leaving the enamel edge as sharp as a blade. Rodents do not have canines and their incisors are separated from the molars or premolars with a wide gap (called diastema). Rodents usually have a compact, cylindrical body and short legs of different length: the front legs are mostly longer than the back legs. The front foot typically has five digits, while the back foot has three to five digits. Rodents have a pointed head supported by the thick, short neck; they also feature large, protruding eyes, long whiskers, and very flexible lips. The body hairs are of the same length over the body except for some cases when the hairs form tufts on tops of the ears; in some species the fur is also thicker on the end of the tail. In some rodents the over hair is modified into scale-like structures. Rodents have fairly large brains but small number of the convolutions of cerebral hemispheres. These animals live in a complex world of smells. They have many cutaneous scent glands that they use for scent-marking. Their modified hairs – vibrissae – form specialized touch organs; vibrissae are very thick and long in most species of rodents.

Rodents form a significant link in the natural food chains through processing huge amounts of food biomass and transforming it into more concentrated animal products. Rodents serve as components of the prey base for numerous carnivorous animals and extirpation of rodents may dramatically affect natural ecological balance.

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