Sinotyrannus

Sinotyrannus was a large tyrannosaur, measuring approximately long and weighing . It is among the largest basal tyrannosauroids known, repudiating the previously presumed trend that tyrannosauroids gradually increased in size throughout the Cretaceous period from small basal forms like Dilong to advanced apex predators such as Tyrannosaurus. The holotype, KZV-001, consists of a disarticulated partial skeleton including the front portion of the skull, three dorsal vertebrae, incomplete ilia, three articulated manual phalanges (including an ungual), and other fragmentary bones. ==Classification==

The original description of Sinotyrannus proposed that it could have been the earliest tyrannosaurid due to its large size, However, Brusatte et al. (2016) instead placed Juratyrant and Stokesosaurus outside of the Proceratosauridae, and proposed that Sinotyrannus represents the sister taxon of Yutyrannus within Proceratosauridae. The results of their phylogenetic analyses are shown in the cladogram below: }} Naish & Cau in 2022 found Sinotyrannus within Proceratosauridae but placed Yutyrannus among the more advanced Tyrannosauroidea. In 2024, Andrea Cau published a comprehensive theropod phylogenetic framework that could be used to identify immature specimens of other taxa. The following year, Cau and Paterna used an updated version of this dataset to deduce that Sinotyrannus—known from a specimen of an adult individual—was a mature form of the "compsognathid" Huaxiagnathus, which is known only from two immature specimens. Both species share a dorsally convex with a short preacetabular process without an anteroventral hook. Other differences observed between the two species are likely the result of differences in body size and ontogenetic stage, consistent with the more established growth series of other tyrannosauroids like Tyrannosaurus. Since Huaxiagnathus was named before Sinotyrannus, this genus name holds priority, making Sinotyrannus a junior synonym of the former. In their phylogenetic tree, the combined Sinotyrannus+Huaxiagnathus operational taxonomic unit (OTU) was recovered as the sister taxon to Eotyrannus in a clade with other traditional proceratosaurids. ==Paleoenvironment==

Sinotyrannus lived in a rather wet environment with well-watered forests and large lakes. The area experienced great diversity in terms of vertebrate fauna, with many taxa, such as Microraptor, living alongside Sinotyrannus. Despite this, the area was quite prone to high volcanism. ==See also==