The Jurassic Period followed the Triassic Period and was followed by the Cretaceous Period. The Jurassic Period is divided into the Lower (or Early) Jurassic, the Middle Jurassic, and the Upper (or Late) Jurassic. The Lower Jurassic is subdivided into four stages: the Hettangian, the Sinemurian, the Pliensbachian, and the Toarcian. The Middle Jurassic is subdivided into four stages as well: the Aalenian, the Bojocian, the Bathonian, and the Callovian. The Middle Jurassic has often been considered a 'black hole' of paleontology, as most of our knowledge of the Jurassic comes from bone-beds dating to the Lower or Upper Jurassic. The Upper Jurassic is divided into three stages: the Oxfordian, the Kimmeridgian, and the Tithonian. This article will examine the evolution of large life forms in the Jurassic Period, paying particular attention to terrestrial and aquatic lifeforms. This article will not focus heavily on smaller life-forms (such as the radiation of the ammonites, diversification of smaller oceangoing creatures - such as the fishes - or the evolutionary paths of ancient insects); nor will it examine the evolution of plant life. These matters are briefly addressed in the sister article, THE JURASSIC PERIOD.
For profiles of Jurassic dinosaurs, visit DINOSAURS OF THE JURASSIC.
For more information on Jurassic pterosaurs, visit PTEROSAURS OF THE JURASSIC.
Click on the links below to go on a journey through the Jurassic!
No comments:
Post a Comment