Final answer:
The statement is false because major extinctions in the Mesozoic era occurred at the end of the Triassic and the end of the Cretaceous periods, not during the Middle Jurassic.
Step-by-step explanation:
The claim that one of the major extinctions of the Mesozoic took place during the Middle Jurassic is false. The major extinctions that framed the Mesozoic era occurred at the end of the Triassic and the end of the Cretaceous periods.
The mass extinction that ended the Triassic period allowed dinosaurs to flourish during the Jurassic, which is sometimes referred to as the golden age of dinosaurs. The end-Cretaceous, or Cretaceous-Paleogene (K-Pg), mass extinction was the event that led to the demise of the dinosaurs and a significant reduction in biodiversity.
Dinosaurs dominated the Mesozoic era, which was also known as the "Age of Reptiles." The Mesozoic era was marked by the rise and eventual fall of dinosaurs, culminating in their extinction at the end of the Cretaceous period, not during the Middle Jurassic.