Madrid. A new analysis of bone remains reveals differences that could suggest that the tyrannosaurus rex should be reclassified into three species: rex, queen and emperor.
Till the date, tyrannosaurus rex it is the only recognized species of this group of dinosaurs or genus. Previous research has recognized the variation between the skeletal remains of Tyra-nnosaurus on the femur (thigh bone) and specimens with one or two slender incisor teeth on each side of the front ends of the jaw.
A team led by Gregory Paul –an independent researcher, author and illustrator who works in paleontology– analyzed the bones and dental remains of 37 specimens of Tyrannosaurus. The authors compared the robustness of the femur in 24 specimens, calculated from the length and circumference, which gives an indication of the strength of the bone. They also measured the diameter of the base of the teeth or the space in the gums to assess whether the samples had one or two thin incisors.
different femurs
According to the results published in Evolutionary Biologythe authors found that there were femurs twice as robust as gracile among the specimens, suggesting that it is not a difference caused by sex, which would probably result in a more even division.
The authors also suggest that the variation in the femurs is not related to the growth of the individual, as robust bones were found in two-thirds adult size juvenile specimens and gracile bones were found in some full adult size.
The dental structure also varied among the specimens, although those with femur measurements and dental remains were low (12 specimens). Individuals with an incisor tooth were correlated with greater gracefulness of the femur.
common ancestor
“We propose that the changes in the femur may have evolved over time from a common ancestor that showed more robust femurs to become more graceful in later species. The differences in the robustness of the femur across the sediment layers are distinct enough that the specimens can be considered separate species,” stated Paul.
The authors nominate two potential new species: the first, tyrannosaurus imperator (tyrant lizard emperor), is related to specimens found in the lower and middle layers of the sediment, characterized by more robust femurs and usually two incisors. They argue that these characteristics have been preserved from earlier ancestors (tyrannosaurids).
The second, tyrannosaurus regina (queen tyrant lizard), is related to specimens from the upper and possibly middle layers of the sediment, characterized by thinner femurs and an incisor tooth.
the recognized species Tyrannosaurus rex (tyrant king lizard) was identified in the upper layer and possibly in the middle of the sediment with classified specimens retaining more robust femurs and having only one incisor tooth. Some specimens could not be identified based on their remains, so they were not assigned to a species.
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