Blue whales are not all one size. Four subspecies are recognized, including the smaller pygmy blue whale. The earliest known anatomically modern blue whale is a partial skull fossil from southern Italy, about 1.5 to 1.25 million years old. As of November 2026, the blue whale is the largest animal known to have ever existed. The longest confirmed ones are about 30 meters long and weigh up to 190 to 200 tonnes. A typical blue whale weighs between 72 and 135 tonnes, much less than the record-holders. Whalers took 350,000 to 360,000 blue whales in the first half of the 20th century; the International Whaling Commission banned all blue whale hunting in 1966. As of November 2026, blue whales are listed as endangered, which means they are at risk of dying out.

A blue whale can be about 100 feet long. Blue whales feeding on krill, the tiny shrimp-like animals they eat, off California reach an average depth of about 201 meters, with dives lasting about 9.8 minutes on average. A blue whale lives about 80 to 90 years. Its calls are very low. Sources give different figures for how loud they are, from 188 dB to 200 dB, so reported loudness varies. As of November 2026, the sperm whale makes the loudest sounds of any animal, with a source level as loud as 236 decibels underwater. That is louder than the 188 dB top reported for blue whales. Sperm whales can plunge to 2,250 meters, making them the third deepest diving mammal.

In 2023 scientists described Perucetus colossus, a whale from the middle Eocene of Peru. Its estimated skeleton weight is greater than that of any known mammal or aquatic vertebrate. Its bones were extremely heavy and dense. They suggest it swam slowly in shallow coastal water, since its bone weight gain is an adaptation linked to shallow diving. As of November 2026, one guess at its weight ranges from 85 to 340 tonnes. That overlaps the heaviest blue whales and is still argued. To judge how heavy it was, the team compared the bones with the whole body in many living animals. Applying that ratio gave a size that makes it a contender for the heaviest animal on record. Perucetus was probably much shorter than a blue whale, with length guesses from about 15 to 20 meters.

Patagotitan was a huge plant-eating dinosaur from Argentina. It walked on four legs. Its thigh bone (femur) alone was 2.38 meters long. The Natural History Museum says it was far longer, almost twice as tall and more than three times heavier than Diplodocus. Other contenders for the largest dinosaur are Argentinosaurus and Puertasaurus. The first Argentinosaurus bone was found in 1987 on a farm near Plaza Huincul, Argentina. A 1989 dig added several back vertebrae and parts of the sacrum; as of November 2026, the animal is known only from fragmentary remains, but it was one of the largest land animals of all time, at 30 to 35 meters long and 65 to 80 tonnes. Even so, a blue whale is bigger than any dinosaur known.

Paraceratherium was one of the largest land mammals known. It lived about 34 to 23 million years ago. As of November 2026, it stood about 4.8 meters at the shoulder, was about 7.4 meters long and weighed about 15 to 20 tonnes. Megalodon is a similar puzzle. Its fossils are fragmentary, so size guesses vary from 14.2 to 24.3 meters. Scientists have debated whether its body was more robust or more elongated than that of modern lamniform sharks. Leedsichthys, a Jurassic fish, was the largest ray-finned fish known; older guesses were larger, but recent research lowered the biggest to about 16.5 meters. It fed on plankton. Its gill arches carried gill rakers with delicate bone plates that filtered tiny food from the sea water. As of November 2026, the whale shark is the largest living fish and the largest non-cetacean animal. A whale shark's skeleton is made of thick flexible cartilage, and it has no rib cage. The whale shark also filters plankton and small fish out of the water.

As of November 2026, giant squid size has often been exaggerated, especially total length. Claims of 20 meters or more have not been scientifically documented. Recent guesses put the maximum body size near 5 meters from the fins to the arm tips. Much of a giant squid's great length is arms and tentacles, which makes it much lighter than its chief predator, the sperm whale. The giant squid is the second-largest mollusc. Its eyes are up to at least 27 cm across, the largest of any living creature except perhaps the colossal squid. Big eyes can detect scarce light, including glowing light, in deep water. Which spider is biggest depends on what is measured. As of November 2026, the goliath birdeater is largest by weight and body length, but the giant huntsman spider has the greater leg span.

The giraffe's long neck seems to have started lengthening early in the giraffe family tree. Comparison with ancient relatives suggests the vertebrae closest to the skull lengthened first. Some record-holders are not animals. As of November 2026, Pando, a grove of aspen trees, is one organism: about 47,000 stems that are genetically identical and linked by roots over about 106 acres. It is counted as the largest tree by weight, but classification systems differ. The General Sherman Tree has an estimated volume of 52,500 cubic feet. Wood volume became the accepted standard for comparing the size of different trees. Its trunk weighs nearly 1,400 tons, roughly the weight of 15 blue whales. As of November 2026, the blue whale is the biggest animal that has ever lived.

Words to know

• subspecies: local variety
• vertebrae: backbone bones
• fragmentary: in pieces
• exaggerated: made too big