Tyrannosaurus remains a clue to three possible separate species

A new analysis of Tyrannosaurus skeletal remains reveal physical differences in the femur, other bones, and dental structures between specimens that may suggest tyrannosaurus rex specimens should be reclassified into three distinct groups or species, reports a study published in evolutionary biology.

tyrannosaurus rex is the only recognized species of the dinosaur group, or genus, Tyrannosaurus nowadays. Previous research has recognized variation across Tyrannosaurus skeletal remains in the femur (femur) and specimens with one or two thin incisors on either side of the anterior ends of the jaw.

Gregory Paul and his colleagues analyzed the bones and dental remains of 37 Tyrannosaurus specimens. The authors compared the sturdiness of the femur in 24 of the specimens, a measure calculated from length and girth that gives an indication of bone strength. They also measured the diameter of the base of the teeth or the space in the gums to determine if the specimens had one or two thin incisiform teeth.

The authors observed that the femur varied between specimens, some with more robust femurs and others with more slender femurs. The authors found that there were twice as many stout femora as slender femora among the specimens, suggesting that this is not a sex-caused difference, which would likely result in more splitting. equal. The authors also suggest that the variation in femora is unrelated to specimen growth, as stout femora have been found in some juvenile specimens at two-thirds the size of an adult and slender femora have been found in some. adult-sized specimens.

Tooth structure also varied between specimens, although those with both femur measurements and tooth remains were low (12 specimens). Specimens with an incisor tooth were correlated with an often higher femoral gracilis.

Of the Tyrannosaurus specimens, 28 could be identified in distinct layers of sediment (stratigraphy) in the Late Masstrichtian formations of the Lancien in North America (estimated between 67.5 and 66 million years old). The authors compared Tyrannosaurus specimens with other theropod species found in lower sediment layers.

Uniquely robust Tyrannosaurus femurs were found in the lower sediment layer (six femurs). The variation in femur robustness in the lower layer was not different from that of other theropod species, indicating that probably a single species of Tyrannosaurus existed at this point. One Grace Tyrannosaurus femur was identified in the middle layer with five other slender femurs in the top layer, alongside other robust femurs. The change in Tyrannosaurus the sturdiness of the femur in the upper sediment layer was higher than that seen in some earlier theropod specimens. This suggests that the Tyrannosaurus specimens found in upper layers of sediment physically developed into more distinct forms compared to specimens in lower layers and other dinosaur species.

Gregory Paul, lead author, said: “We found that changes in Tyrannosaurus the femurs are probably not related to the sex or age of the specimen. We propose that changes in the femur may have evolved over time from a common ancestor that exhibited more robust femora to become more slender in later species. The differences in femur robustness across sediment layers can be considered distinct enough that the specimens could potentially be considered separate species.”

The authors designate two potential new species of Tyrannosaurus based on their analysis. The first one, Imperator Tyrannosaurus (tyrant lizard emperor), refers to specimens found in the lower and middle layers of sediment, characterized by more robust femurs and usually two incisors. The authors argue that these features were carried over from earlier ancestors (tyrannosaurids). The second, tyrannosaurus regina (tyrant lizard queen), is related to specimens from the upper and possibly middle layers of sediment, characterized by thinner femurs and an incisor tooth. The recognized species tyrannosaurus rex (tyrant lizard king) has been identified in the upper and possibly middle layer of sediments with specimens classified as retaining more robust femurs while having only one incisor. Some specimens could not be identified based on their remains and therefore were not assigned to a species.

The authors acknowledge that they cannot rule out that the observed variation is due to extreme individual differences, or atypical sexual dimorphism, rather than separate groups, and they also caution that the location in the sediment layers is not known for some specimens. The authors discuss the difficulties of assigning fossil vertebrates to a potential new species.

The authors conclude that the physical variation found in Tyrannosaurus the specimens combined with their stratigraphy indicate three potential groups that could be proposed as two new species, T.imperator and T. Reginaalongside the only recognized species to date, T. rex.

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