The Bathonian Age represents a captivating chapter in Earth’s deep history, forming a distinct segment within the larger Jurassic Period. This ancient interval provides a window into a world vastly different from our own, characterized by evolving continents, dynamic climates, and a rich tapestry of life forms.
When Was the Bathonian Age?
The Bathonian Age is a specific time interval within the Middle Jurassic epoch. It began approximately 168.2 million years ago and concluded around 165.3 million years ago, spanning roughly three million years. This age follows the Bajocian Age and precedes the Callovian Age. Geologists identify the start of the Bathonian by the first appearance of the ammonite species Parkinsonia (Gonolkites) convergens in the fossil record. The end of the Bathonian is similarly defined by the first appearance of the ammonite genus Kepplerites.
The World of the Bathonian
During the Bathonian Age, the supercontinent Pangaea continued its slow breakup. This continental rifting led to the gradual opening of new ocean basins, including the nascent central Atlantic Ocean and the Gulf of Mexico. Heightened plate tectonic movement contributed to significant volcanic activity and mountain-building events across the globe. Shallow seaways extended across many continental areas, resulting in the deposition of marine and coastal sediments that preserved a diverse array of fossils. The climate during this period was generally warm, with some evidence suggesting a subtropical environment that experienced alternating wet and dry seasons, likely influenced by a global monsoonal circulation.
Life Flourishing in the Bathonian
The Bathonian Age hosted a wide variety of life, both on land and in the seas. Terrestrial environments were dominated by diverse dinosaur groups. These included early stegosaurs, large sauropods, and various theropods, which were the dominant predators of the time. For instance, the Isle of Skye in Scotland has yielded remains of basal eusauropods and early theropods from this period.
Beyond dinosaurs, other reptiles like crocodilians and pterosaurs were also present. The plant life formed the foundation of these ecosystems, consisting primarily of gymnosperms, such as ferns, cycads, and conifers. Marine environments were rich with life, featuring large marine reptiles like plesiosaurs and ichthyosaurs, alongside a diverse array of fish and thriving invertebrate communities.
Key Discoveries and Their Insights
Our understanding of the Bathonian Age has largely been shaped by significant fossil discoveries from specific geological formations. The Stonesfield Slate in Oxfordshire, England, is a particularly important site, renowned for yielding an unusually diverse mix of marine, freshwater, and terrestrial fossils from the Middle Jurassic. These discoveries include remains of over 15 species of reptiles, such as turtles, crocodilians, pterosaurs, and various dinosaurs.
Among the notable finds from Stonesfield are the type specimens of Megalosaurus bucklandii, recognized as the first dinosaur to be formally described. These fossil findings provide detailed insights into the Bathonian climate, geography, and the composition of its ancient ecosystems. Scientists have used these remains to reconstruct the ancient world and its inhabitants.