The question of what color Stegosaurus was remains one of the biggest unknowns in dinosaur paleontology. Although popular culture often depicts the Jurassic herbivore in drab greens and browns, the actual hue of its skin is a scientific mystery. Direct evidence of dinosaur coloration is rarely preserved over the tens of millions of years separating us from the Mesozoic Era. Science addresses this challenge by examining the limitations of the fossil record and applying modern analytical techniques. Exploring the potential colors of Stegosaurus requires understanding why this information is usually lost and how the animal’s unique anatomy might have influenced its appearance.
Why Stegosaurus Color Remains a Mystery
The primary reason the color of Stegosaurus is unknown lies in the nature of fossilization itself. This process, known as taphonomy, strongly favors the preservation of hard tissues like bone and teeth, while soft tissues almost always decay entirely. Skin, muscle, internal organs, and the microscopic structures containing pigment break down quickly after death, usually before fossilization can begin. This differential preservation means that the vast majority of dinosaur fossils are skeletal remnants, providing no direct data on external appearance.
Pigmentation is contained within organic molecules highly susceptible to decomposition and chemical alteration over geological timescales. The original color-bearing compounds, or chromophores, are destroyed by bacteria, chemical reactions, and the pressure and heat involved in burial. Consequently, even when skin impressions are preserved, they usually record only the texture and pattern of scales, not the color. The lack of soft tissue preservation in Stegosaurus specimens means that the color-determining layers of its epidermis are absent.
Paleontological Clues: How Color Is Determined
Despite the pervasive loss of soft tissue, scientists have developed methods to infer the coloration of some extinct species. This technique centers on the analysis of melanosomes, which are tiny, pigment-containing organelles found in the skin and feathers of many animals. Melanin, the pigment they hold, is chemically robust, and under exceptional fossilization conditions, the physical structure of the melanosomes can be preserved. The shape and density of these microscopic structures correlate directly to specific colors in modern animals.
Eumelanin produces black and gray colors and is associated with elongated, sausage-shaped melanosomes. Phaeomelanin, which results in reddish-brown or chestnut tones, is stored in more spherical melanosomes. By examining these fossilized organelles using a scanning electron microscope, researchers have reconstructed the color patterns of some feathered dinosaurs, such as Sinosauropteryx and Anchiornis.
These preserved microstructures provide empirical evidence for reconstructing color patterns, like the striped tail of Sinosauropteryx. However, this analytical method depends on the rare preservation of integumentary structures, such as feathers or fine skin filaments, which are not present in Stegosaurus fossils. Furthermore, many vibrant colors, like bright yellows and reds, are caused by pigments like carotenoids, which degrade too quickly to be preserved.
Applying Color Theory to Stegosaurus Anatomy
Since direct evidence is unavailable, hypotheses about Stegosaurus color are based on its morphology and presumed ecology. One theory suggests a functional coloration for camouflage, likely involving dull, earthy tones like greens, grays, or browns. Large, grazing herbivores often utilize countershading, where the back is darker and the belly is lighter, to counteract the effect of shadows. This pattern would have helped the massive animal blend into the low-lying Jurassic scrub.
A contrasting hypothesis focuses on the prominent dorsal plates, which may have served a purpose in visual display or signaling. These plates were anchored in the skin and were highly vascularized, meaning they contained numerous blood vessels. This rich blood supply suggests the plates could have flushed with blood, potentially changing their color to a vivid red or pink for a temporary visual effect. Such a display could have been used for species recognition, intimidating rivals, or attracting mates, a concept known as sexual selection. The keratin sheath that likely covered the plates could also have been brightly colored, favoring striking, contrasting patterns over simple camouflage.