Humans may be the ones who cracked the code on cell phones, written language, and sliced bread, but the animal kingdom brings a lot to the table in terms of sheer size and strength. Yes, it was a human being who wrote “Romeo and Juliet,” as was the inventor of the vacuum cleaner, but these accomplishments don’t mean much to a 12-foot-wide crab or a 300-pound bird. As humans, we can only bow our heads in respect to these massive kings and queens of the animal world.

The animals included on this list all share one trait: They are larger than any other animal of their kind, which may have a little something to do with an evolutionary trend. In recent years, new research has emerged in support of Cope’s rule, which posits that over generations, animals will evolve to become larger. This Stanford study found that while it’s not necessarily the case that all animals have become bigger over time, those that were already on the larger side did evolve and branch off to become more diverse—which can ultimately prove beneficial in terms of survival.

That being said, there are certainly some ancient creatures whose unfathomable size would have made them an unwelcome guest in the modern world. Take the extinct Titanoboa, for instance: a 3,000-pound, 48-foot-long snake whose remains were discovered in Colombia.

Stacker has done extensive research in order to create this unique list, which features the largest animals of their kind for certain categories of the animal kingdom. These categories, including mammal, bird, fish, and beyond, offer an overall look at the living beings that tower over others of their kind.

Read on to learn more about the biggest animals in the world.

Mammal: Blue whale

The blue whale is the largest animal on earth, and perhaps the largest ever to have existed, usually ranging between 70 and 90 feet in length (though there are records of some that have exceeded the 100-foot mark). These whales have been found in every ocean across the globe, often traveling in pairs; areas off the California coast hold the densest population. Unsurprisingly, being that big requires many calories: Blue whales can eat between 2 and 4 tons of krill (a shrimp-like crustacean) a day.

Land mammal: African bush elephant

The African bush elephant, which can weigh up to 11 tons and reach 13 feet in height, is characterized by its pronounced tusks, and large head and ears. The elephant is also notable for its dextrous and sensitive trunk, which is made up of over 40,000 muscles and tendons and thereby allows the elephant to handle objects of all sizes with ease. African bush elephants can be found in most African countries, though their survival is at stake due to both poaching concerns and habitat destruction.

Reptile: Saltwater crocodile

Despite earning the cute-sounding nickname of “saltie,” the saltwater crocodile is often regarded as a fearsome creature—due to its 1,000-pound weight, massive jaws, and willingness to eat nearly any animal that wanders into its sights. These crocodiles hunt by waiting just below the surface of a body of water, then bursting out using their tails in order to catch and drown their prey. Saltwater crocodiles can be found in a variety of regions, ranging from Australia to Southeast Asia.

Lizard: Komodo dragon

The Komodo dragon‘s name alone is an indicator of this lizard’s power and physical characteristics: It’s dark and scaly, extremely strong, and uses a long, thin forked tongue to test the air for signs of nearby prey. At maturity, a Komodo dragon weighs 154 pounds on average, though the largest confirmed specimen was more than twice that size. Found in Indonesian Islands, the Komodo dragon can both eat 80% of its own body weight in one meal, and empty its stomach at will in order to reduce its weight and escape danger more quickly.

Snake: Giant anaconda

Referenced in pop culture from hip-hop songs to action movies, this jungle-dwelling snake can weigh in at around 550 pounds. Found in swampy regions of South America, and commonly known as the green anaconda, this creature not only possesses the ability to swim, but is in fact more agile in the water than on land. The mega-snake kills its prey with asphyxiation, and is known to maintain its size by dining on large animals such as pigs and deer.

Bird: Ostrich

The ostrich may not actually be able to fly, but this African bird can run at speeds of 45 miles per hour when threatened. An adult male ostrich may weigh close to 300 pounds, and can reach a height of 9 feet (about half of which comes from its neck). This last surviving member of the genus Struthio dines on things like berries and grass, and has a progressive approach to the division of household labor: Both females and males take turns guarding and tending to their eggs after a female has laid them.