The scientific world has been divided ever since the discovery of Nanotyrannus, the dwarf species of Tyrannosaurus rex in 1942. Scientists have argued the very existence of the species as many believed that Nanotyrannus never existed. The latest study has shown that the dwarf version of T-rex probably never existed and that it was the immature Tyrannosaurus they mistakenly termed as Nanotyrannus.
A study published in journal Science Advances, led by Holly Woodward of Oklahoma State University confirmed that the 2001 discovery of small Tyrannosaurus named Jane near the town of Ekalaka in Montana revealed that the fossil was of an immature individual and not an adult. Woodward performed microscopic analysis of samples from the interior of Jane's tibia and femur bones and on bones from an animal named Petey. The technique is known as paleohistology, a study of fossil remains.
Osteohistology revealed these were immature individuals 13 to 15 years of age, exhibiting growth rates similar to extant birds and mammals, and that annual growth was dependent on resource abundance. The results support the synonymization of “Nanotyrannus” into Tyrannosaurus and failed to prove that a smaller adult version of Tyrannosaurus really existed.
The results in the science journal stated, "For detailed, orientation-specific histology descriptions, refer to the Supplementary Materials. In general, the femur and tibia cortical bones of Jane and Petey can be classified as a woven-parallel complex. Vascularity and osteocyte lacuna density are uniformly high throughout. In the femora, the primary and secondary osteons surrounding vascular canals are frequently isotropic in the transverse section and anisotropic in the longitudinal section. Also in the transverse section, femur primary tissue exhibits moderate anisotropy regionally and weak anisotropy locally, corresponding to a loose arrangement of mineralized fibers in parallel."
The study helped fill the gap with some knowledge that the scientific world was lacking when it came to the 20-year time period between a dinosaur's hatching and its childhood. Jane weighed one ton before it died and would have weighed under 10 tonnes as an adult if it would have reached the phase of exponentially rapid growth.