 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 200 kilograms ( 440 lb ) individual about one and a half hours for its body temperature to rise from 26 to 32 ° C ( 79 to 90 ° F ) . 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 . 
