The authors observed that the femur varied throughout specimens, some with more robust femurs and others with more gracile femurs. The authors likewise recommend that the variation in femurs is not related to development of the specimen as robust femurs were found in some juvenile specimens 2 thirds the size of a gracile and adult femurs were discovered in some specimens that were full adult size.
The distinctions in thigh toughness throughout layers of sediment might be thought about unique enough that the specimens could possibly be thought about separate types.”
The first, Tyrannosaurus imperator (tyrant lizard emperor), relates to specimens found at the lower and middle layers of sediment, characterized with more robust femurs and usually two incisor teeth. The second, Tyrannosaurus regina (tyrant lizard queen), is linked to specimens from the upper and possibly middle layers of sediment, defined with slenderer thighs and one incisor tooth.
A brand-new analysis of Tyrannosaurus skeletal remains exposes physical distinctions in the femur, other bones, and oral structures throughout specimens that could recommend Tyrannosaurus rex specimens require to be re-categorized into 3 distinct groups or species, reports a study released in Evolutionary Biology.
Tyrannosaurus rex is the only acknowledged species of the group of dinosaurs, or genus, Tyrannosaurus to date. Previous research study has acknowledged variation throughout Tyrannosaurus skeletal remains in the femur (thighbone) and specimens with either one or 2 slim incisor teeth on each side of front ends of the jaw.
Gregory Paul and coworkers examined the bones and oral remains of 37 Tyrannosaurus specimens. The authors compared the effectiveness of the thigh in 24 of the specimens, a procedure calculated from the length and circumference that provides a sign of the strength of the bone. They also measured the diameter of the base of teeth or space in the gums to assess if specimens had a couple of slender incisiform teeth.
The authors observed that the thigh varied throughout specimens, some with more robust thighs and others with more gracile femurs. The authors found there were 2 times more robust thighs than gracile ones across specimens, which recommends that this is not a difference triggered by sex, which would likely lead to a more even divided. The authors likewise suggest that the variation in thighs is not connected to growth of the specimen as robust femurs were discovered in some juvenile specimens two thirds the size of an adult and gracile femurs were found in some specimens that were full adult size.
Oral structure likewise varied across specimens, although those with both femur measurements and dental remains was low (12 specimens). Specimens with one incisor tooth were associated with often having higher thigh gracility.
Of the Tyrannosaurus specimens, 28 might be identified in unique layers of sediment (stratigraphy) at the Lancian upper Masstrichtian formations in North America (approximated to be from between 67.5 to 66 million years ago). The authors compared Tyrannosaurus specimens with other theropod types found in lower layers of sediment.
The variation in Tyrannosaurus femur robustness in the top layer of the sediments was greater than what was observed in some earlier theropod specimens. This recommends that the Tyrannosaurus specimens found at greater layers of sediment physically developed into more unique types compared to specimens from lower layers, and other dinosaur types.
Gregory Paul, lead author, said: “We discovered that the modifications in Tyrannosaurus thighs are most likely not associated to the sex or age of the specimen. We propose that the modifications in the thigh might have developed with time from a typical forefather who displayed more robust femurs to end up being more gracile in later species. The distinctions in femur effectiveness across layers of sediment may be considered unique enough that the specimens might potentially be considered separate species.”
The authors choose 2 potential new types of Tyrannosaurus based on their analysis. The very first, Tyrannosaurus imperator (tyrant lizard emperor), connects to specimens discovered at the lower and middle layers of sediment, identified with more robust thighs and typically two incisor teeth. The authors argue these functions have been retained from earlier forefathers (tyrannosaurids). The second, Tyrannosaurus regina (tyrant lizard queen), is connected to specimens from the upper and perhaps middle layers of sediment, characterized with slenderer thighs and one incisor tooth. The acknowledged types Tyrannosaurus rex ( tyrant lizard king) was identified in the upper and perhaps middle layer of sediment with specimens classed as retaining more robust thighs while having only one incisor tooth. Some specimens might not be identified based on their remains so were not assigned to a types.
The authors acknowledge that they can not eliminate that the observed variation is because of extreme private distinctions, or irregular sexual dimorphism, rather than different groups, and they likewise caution that the area within sediment layers is not understood for some specimens. The authors discuss the problems of appointing fossil vertebrates to a potential new species.
The authors conclude that the physical variation discovered in Tyrannosaurus specimens combined with their stratigraphy are a sign of 3 potential groups that might be chosen as two brand-new types, T. imperator and T. regina, together with the only recognized types to date, T. rex.
Reference: “The Tyrant Lizard King, Queen and Emperor: Multiple Lines of Stratigraphic and morphological Evidence Support Subtle Evolution and Probable Speciation Within the North American Genus Tyrannosaurus” by Gregory S. Paul, W. Scott Persons IV and Jay Van Raalte, 1 March 2022, Evolutionary Biology.DOI: 10.1007/ s11692-022-09561-5.