Dinosaurs and Their Leg Count
No known dinosaur species ever had 500 feet. Dinosaurs, a diverse group of reptiles that dominated terrestrial ecosystems for over 165 million years, typically moved on either two or four limbs.
Many familiar dinosaurs, such as the predatory Tyrannosaurus rex or the swift Velociraptor, were bipedal, meaning they walked on two legs. Other large dinosaurs, like the long-necked sauropods such as Brachiosaurus or the armored Stegosaurus, were quadrupedal, utilizing all four limbs for movement and support.
The Real Multi-Legged Wonder
While no dinosaur had 500 feet, the animal kingdom does include a creature renowned for its astonishing number of limbs: the millipede Illacme plenipes. This unique arthropod holds the record for having up to 750 legs. Discovered in California, this species highlights the incredible diversity of life on Earth.
Illacme plenipes is a slender, thread-like creature, typically less than an inch long, that lives in moist soil and leaf litter. It belongs to the class Myriapoda, a group of arthropods with elongated bodies and numerous segments, each bearing one or two pairs of legs. This classification places millipedes in a completely different branch of the animal kingdom from reptiles like dinosaurs. Their many legs allow them to navigate complex underground environments, burrowing through tight spaces in search of decaying plant matter, which constitutes their primary diet.
Why the Misconception?
The popular notion of a “500-footed dinosaur” likely stems from a broader public understanding of “prehistoric creatures” that often blurs the lines between vastly different ancient life forms. The term “prehistoric” encompasses a massive span of time and an immense variety of organisms, including not only dinosaurs but also marine reptiles, flying reptiles, and diverse invertebrates. This broad categorization can lead to confusion regarding the specific characteristics of distinct groups.
Dinosaurs were a specific group of reptiles that lived during the Mesozoic Era, roughly 252 to 66 million years ago, characterized by unique anatomical features such as an upright stance and specific hip structures. In contrast, millipedes like Illacme plenipes are arthropods, an entirely separate phylum, with an evolutionary history distinct from vertebrates like dinosaurs. The scientific classification system helps organize life into hierarchical categories, clarifying the relationships and differences between various organisms, thereby dispelling such widespread misconceptions about ancient life.