Smallest animals

Size isn’t everything. These Lilliputian creatures, the smallest in their respective taxonomic groups, show that diminution has its advantages.
Smallest frog

Paedophryne amauensis
Paedophryne amauensis.
Saibo
Paedophryne amauensis
Adults of this New Guinea species are, on average, around 7.7 millimeters (0.3 inch) long. They are the smallest known vertebrates.
Smallest snake

Leptotyphlops carlae
© Kaipop/Dreamstime.com
Barbados threadsnake (Leptotyphlops carlae)
At 10.4 centimeters (4.1 inches), this is the smallest snake. It burrows in search of insects and other small invertebrates.
Smallest bird

Mellisuga helenae
© Sergey Uryadnikov/Shutterstock.com
Bee hummingbird (Mellisuga helenae)
Six centimeters (2.4 inches) at its largest, this species is the tiniest bird in the world. It is found only in Cuba.
Smallest fish

Paedocypris progenetica
Aquaristikhaus
Paedocypris progenetica
These Sumatran fish usually reach only around 10 millimeters (0.4 inch) at maturity. One female was less than 8 millimeters (0.3 inch). They don’t even have room for a whole skull in their tiny bodies…parts of the brain are not covered by bone.
Smallest shark

Dwarf lantern shark (Etmopterus perryi).
Encyclopædia Britannica, Inc.
Dwarf lantern shark (Etmopterus perryi)
At around 20 centimeters (8 inches), this guy is the littlest of the sharks. The species also emits light as a form of camouflage from predators lurking below. The light helps break up the animal’s silhouette so that it blends in with the light coming from above.
Smallest cetacean

vaquita
Vaquita (Phocoena sinus) caught in gill net with sharks and other fish in the Gulf of California, Mexico.
© Minden Pictures/SuperStock
Vaquita (Phocoena sinus)
The smallest of the cetaceans, the group that contains whales and dolphins, this endangered porpoise, which frequents the Gulf of California, maxes out at around 1.5 meters (4.9 feet).
Smallest mammal

Suncus etruscus
© Palych/Dreamstime.com
Etruscan shrew (Suncus etruscus)
At less than 3 grams (0.11 ounce), this tiny shrew is the smallest mammal. Its exquisitely tuned reflexes, aided by muscles composed entirely of fast-twitch fibers, assist it in capturing insects