Tyrannosaurus Rex attacked trachyte Triceratops. Source: evolutionary biology According to a recent study published in evolutionary biology, scientists analyzed the remains of T. rex and found that there were differences in the structure of femurs, other bones and teeth in different samples, or that T. rex samples need to be reclassified into three different categories or species. Tyrannosaurus Rex is the only recognized species of Tyrannosaurus Rex. Previous studies have found differences in the femur (thigh bone) and teeth (one or two slender incisors on both sides of the front of the mandible). A team of American scientists analyzed the skeletal and dental remains of 37 samples of Tyrannosaurus Rex. They compared the strength of the femurs in 24 of the samples, a measure of bone strength calculated from the length and circumference of the femur. They also measured the diameter of the bottom of the teeth or the cavities in the gums to determine whether the sample had one or two slender incisors. The team looked at the femurs of each sample, and the number of strong femurs was twice as much as that of thin femurs, which showed that the difference was not due to gender (if it was due to gender, the two numbers should be closer), and the difference was not related to growth status. The tooth structure also varies among different samples, but there are few samples with both femoral data and tooth remains (12). Samples with only one incisor were more likely to have a slender femur. The research team suggested that the change of femur may be from a common ancestor with strong femur to a more slender appearance in later species. The differences in femoral firmness in different sedimentary layers may be significant enough for some samples to be considered independent species. They then nominated two new species, t. imparator and t. Regina, alongside the only recognized Tyrannosaurus Rex to date. (Xinhua News Agency)