Long-eared desert hedgehog

There are about 5,400 species of mammals in the air and water and on the land.

Some characteristics of mammals are:

• mammary glands
• hair
• diaphragm
• three middle-ear ossicles
• heterodont dentation
• sweat, sebaceous, and scent glands
• four-chambered heart
• large cerebral cortex

Mammal record setters – the big, the bad, and the ugly:

• Fastest – cheetah at 60-70 mph (97-110 kph)
• Slowest – sloths
• Biggest – blue whale
• Biggest on the land – african elephant
• Biggest primate – gorilla
• Biggest fish – whale shark
• Tallest – giraffe
• Smallest – pygmy shrew (1.2-2.7 g) or maybe the bumblebee bat (about 2 g)
• Loudest – blue whale
• Loudest on land – howler monkey
• Smelliest – striped skunk
• Ugliest – aye-aye or maybe the solenodon
• Fatest – blue whale
• Badest – man
• Wickedest – bats
• Venomest – male duckbilled platypus, some shrews, and the solenodon

Some of the orders of mammals are:

• Monotremata (egg-laying marsupials)
• Marsupialia (marsupials) – They have a different take on how pregnancy should be done.
• Insectivora (insectivores)
• Chiroptera (bats)
• Dermoptera (flying lemurs)
• Macroscelidea (elephant shrews)
• Scandentia (tree shrews)
• Primates (primates)
• Xenarthra (anteaters and relatives)
• Pholidota (pangolins)
• Lagomorpha (rabbits, hares, and pikas)
• Rodentia (rodents) – the most populous group making up to 40 percent of the mammals.
• Cetacea (cetaceans)
• Carnivora (carnivores)
• Pinnipedea (seals and sea lions)
• Proboscidea (elephants)
• Tubulidentata (aardvark)
• Hyracoidea (hyraxes)
• Sirenia (dugongs and manatees)
• Perissodactyla (odd-toed hoofed mammals)
• Artiodactyla (even-toed hoofed mammals)