Smallest True Monkey
The Pygmy Marmoset or Dwarf Monkey (Cebuella pygmaea) is the world's smallest true monkey. The species live high in the rainforest canopy of South America. Adults measure around 117 to 152 millimeters (4.6 to 6.0 in) in head-body length and a tail of 172 to 229 millimeters (6.8 to 9.0 in). The average adult body weight is just over 100 grams (3.5 oz). To picture this out; a full-grown pygmy marmoset could fit in an adult human's hand, and it weighs about as much as a stick of butter!
Western Pygmy Blue Butterfly
With a wingspan no bigger than 1.3 centimeters (0.5 inch), the Western Pygmy Blue (Brephidium exilis) is the the smallest in North America and possibly the smallest known butterfly in the world. Although not the brightest of butterflies, its delicate markings make it stand out.
The Royal Antelope (Neotragus pygmaeus), native to West Africa's lowland rainforest is the world's smallest antelope. The shy, light brown colored cute little guy stands about 25 cm (10 inches) and weighs 2.5–3 kg (5.5–7 pounds). A calf is small enough to fit into an average person's open hand.
Cuvier's Dwarf Caiman
The Cuvier's Dwarf Caiman (Paleosuchus palpebrosus) is the smallest extant species of crocodilian. Native to northern and central South America, full-grown males can reach up to 1.6 meters (5.2 feet) in total length. Females can measure up to 1.2 meters (3.9 ft). The tiny crocodilian is also called Cuvier's smooth-fronted caiman and Musky caiman.
Discovered in swamp forests of Sumatra in 2006, the Paedocypris Carp (Paedocypris progenetica) is the world's smallest fish! At only 7.9 mm at maturity, the tiny carp is also considered the smallest vertebrate. The species has a rudimentary skull which leaves the brain unprotected and is known for their ability to live in water with high levels of acidity.
Madame Berthe's Mouse Lemur
The world's smallest living primate is the Madame Berthe's Mouse Lemur (Microcebus berthae). The new lemur species was discovered in Madagascar. The nocturnal creature has an average body length of 9.2 cm (3.6 in), tail length of 12 to 14 cm, and weighs around 30 grams (1.1 oz).
Columbia Basin Pygmy Rabbit
The Columbia Basin Pygmy Rabbit (Brachylagus idahoensis) is the smallest rabbit. The kitten-sized rabbits is found in North America. Once on the verge of extinction, full -grown pygmy rabbit measures from 23.5-29.5 centimeters (9.3-11.6 in) and weighs from 375-500 grams (0.827-1.102 lb). Females are slightly larger than males.
The Barbados Threadsnake (Leptotyphlops carlae) is the world’s smallest species of snake. This species is found in the Caribbean islands of Barbados. At about ten cm long (less than four inches), enough to curl up on a U.S. quarter, the tiny snake might easily be mistaken for an earthworm. Also, the diminutive reptile is as thin as spaghetti noodle.
Virgin Islands Dwarf Gecko
Measuring 16 millimeters (just over half an inch) long from the tip of the snout to the base of the tail, the Virgin Islands Dwarf Gecko (Sphaerodactylus ariasae) is the world's tiniest species of lizard. Discovered in 1964, the dark brown lizard is found in three British Virgin Islands, namely, Virgin Gorda, Tortola and Mosquito Island. When fully grown, this miniature lizard is small enough to curl up on a dime!
The Kitti's Hog-nosed Bat (Craseonycteris thonglongyai) or Bumblebee Bat is the world's smallest bat, maybe even the smallest mammal. Native to Thailand, this diminutive bat is about 36 to 53 mm (1.4 to 2.1 in) in length, a wingspan of about 170 mm (6.7 inches) and weighs less than two grams (0.071 oz). This odd-looking bat is known for its distinctive pig-like snout and relatively wide wings with long tips.