Redaktor:DinoVictor/pieskovisko

Gorgosaurus libratus

V roku 1913 našiel paleontológ Charles Hazelius Sternberg v geologicky mierne staršom albertskom súvrství Dinosaur Park kostru iného tyranosaura, ktorému nasledujúci rok dal Lawrence Morris Lambe meno Gorgosaurus libratus. Neskôr boli v Alberte a v americkom štáte Montana nájdené ďalšie jedince tohto druhu. Zistením, že sa rod Gorgosaurus od rodu Albertosaurus líši len drobnými rozdielmi ho Dale Russell v roku 1970 deklaroval za jeho mladšie synonymum a druh Gorgosaurus libratus premenoval na Albertosaurus libratus, čím sa časový rozsah výskytu tohto dinosaura zvýšil o niekoľko miliónov rokov a areál rozprestierania rozšíril o stovky kilometrov ďalej na juh.

In 2003, Philip J. Currie, benefiting from much more extensive finds and a general increase in anatomical knowledge of theropods, compared several tyrannosaurid skulls and came to the conclusion that the two species are more distinct than previously thought. The decision to use one or two genera is rather arbitrary, as the two species are sister taxa,more closely related to each other than to any other species. Recognizing this, Currie nevertheless recommended that Albertosaurus and Gorgosaurus be retained as separate genera, as he concluded that they were no more similar than Daspletosaurus and Tyrannosaurus,which are almost always separated. In addition, several albertosaurine specimens have been recovered from Alaska and New Mexico,and Currie suggested that the Albertosaurus-Gorgosaurus situation may be clarified once these are described fully. Most authors have followed Currie's recommendation, but some have not.