In 1940, Alfred Romer and Llewellyn Ivor Price proposed that the sail served a thermoregulatory function, allowing individuals to warm their bodies with the sun's heat. In the following years, many models were created to estimate the effectiveness of thermoregulation in "Dimetrodon". For example, in a 1973 article in the journal "Nature", paleontologists C. D. Bramwell and P. B. Fellgett estimated that it took a individual about one and a half hours for its body temperature to rise from . In 1986, Steven C. Haack concluded that the warming was slower than previously thought and that the process probably took four hours. Using a model based on a variety of environmental factors and hypothesized physiological aspects of "Dimetrodon", Haack found that the sail allowed "Dimetrodon" to warm faster in the morning and reach a slightly higher body temperature during the day, but that it was ineffective in releasing excess heat and did not allow "Dimetrodon" to retain a higher body temperature at night. In 1999, a group of mechanical engineers created a computer model to analyze the ability of the sail to regulate body temperature during different seasons, and concluded that the sail was beneficial for capturing and releasing heat at all times in the year.