The Stegosaurus is famous for its double row of large, bony plates (dermal plates) along its back and the spiked tail, known as the thagomizer. These features have intrigued scientists, leading to several hypotheses about their functions, including defense, thermoregulation, and display.
- Dermal plates are large, flat, and arranged in two alternating rows.
- The thagomizer consists of four to ten spikes, used as a defensive weapon.
- Functions considered: defense, thermoregulation, species recognition, sexual display, and communication.
Defense, thermoregulation, and display are all proposed functions of Stegosaurus' plates and spikes.
The dermal plates and thagomizer are the key features, with plates proposed for display/thermoregulation and thagomizer for defense.
Source Material
Author: National Geographic
Document: Stegosaurus: Facts About the Dinosaur’s Plates
Date Published: 2023
Source Material
Author: American Museum of Natural History
Document: Stegosaurus - Plates and Spikes
Date Published: 2024
Thermoregulation
One popular theory suggests that the plates acted as thermoregulatory structures, helping Stegosaurus control its body temperature. Blood vessels inside the plates might have absorbed or released heat, functioning like solar panels or radiators.
- Plates had a rich supply of blood vessels, seen in fossilized cross-sections.
- Could absorb heat from the sun or release excess heat to the air.
- Fossil evidence shows plates had vascularized bone, supporting heat exchange.
- Modern analog: Elephant ears use blood flow for temperature regulation.
Elephant ears use blood flow to regulate temperature, similar to the proposed function of Stegosaurus plates.
Source Material
Author: National Geographic
Document: Stegosaurus’ Plates May Have Worked Like Radiators
Date Published: 2013
Defense
The spiked tail or thagomizer is widely accepted as a defensive weapon. Tail spikes could swing powerfully to deter or injure predators. Some researchers also suggest the plates might have offered passive protection or made the dinosaur appear larger.
- Tail spikes showed signs of wear and damage, indicating use in combat.
- Plates may have shielded the back or deterred predators via intimidation.
- Fossils show tail spike injuries in predator bones.
- Possible analog: Porcupine quills as defensive structures.
Wear and damage on spikes and injuries found in predator fossils support defensive use.
Source Material
Author: Smithsonian Magazine
Document: How Stegosaurus Used Its Thagomizer
Date Published: 2016
Display and Communication
The plates might have been used for species recognition, sexual display, or communication. Their size, shape, and possible coloration could help individuals identify each other, attract mates, or send signals (like aggression or submission).
- Plates show variation between species and possibly between sexes.
- Bright colors or patterns may have been displayed via blood flow changes.
- Some fossils hint at Stegosaurus using plates for social interaction.
- Display traits are common in modern reptiles and birds.
- Hypothetical signals: change in blood flow could alter plate color.
Evidence includes variation in plate shape and potential for coloration and blood flow changes, but direct fossilized pigment is rare.
Source Material
Author: Encyclopaedia Britannica
Document: Stegosaurus: The Dinosaur with the Giant Plates
Date Published: 2024
Conclusion
The plates and spikes of Stegosaurus served multiple potential functions, illustrating the complexity of dinosaur biology and behavior.
- Plates may have regulated temperature, deterred predators, or facilitated social interaction.
- Tail spikes provided an effective defensive mechanism.
- Ongoing research continues to shed light on these iconic structures.