Of the more than 60,000 vertebrates currently known to humans, finding the largest doesn’t seem to be too much of a problem. To date, scientists believe the largest vertebrate known is the marine mammal called the blue whale (Balaenoptera musculus); it is also considered the largest known animal on Earth (and one of the loudest animals on Earth). Mature blue whales can reach around 75 to 100 feet (23–30.5 meters) in length; they can weigh up to 150 tons (136 metric tons), although because of whaling hunts, the largest of the whales are thought to have dwindled in number, with the average being about 75 to 80 feet (23–25 meters) long. Even baby blue whales are bigger than most animals, averaging, at birth, about 25 feet (7.6 meters) long.

For obvious reasons, determining the smallest vertebrates can be very difficult, and it is often debated how to measure different animals, such as a frog versus a fish. One of the latest contenders was found in 2012—a new species of frog from New Guinea called Paedophryne amauensis that measured around one-third of an inch (7.7 millimeters) in size. It was also found with a “bigger cousin”—the frog Paedophryne swiftorum—that averaged only about 0.33 inch (8.5 millimeters) in size. Still other scientists point to a creature called a Paedocypris progenetica found in 2006—a fish that measures about 0.31 inch (7.9 millimeters) long and lives in the acid swamps of Sumatra.

The following chart lists the largest and smallest vertebrates known to date: