Late JurassicEdit

The Late Jurassic is the latter portion of the Jurassic Period, spanning roughly 163.5 to 145 million years ago. It is subdivided into the Oxfordian, Kimmeridgian, and Tithonian stages, reflecting a sequence of time in which the world was configured very differently from today. During this interval the supercontinent Pangaea continued to rift and rearrange, giving rise to emerging seaways that reshaped climate zones and biogeography. Fossil-rich sites such as the Morrison Formation in North America and the Solnhofen Limestone in Europe preserve detailed snapshots of ecosystems as they evolved through the Late Jurassic.

Global climates remained warm with high sea levels, and there were no long-lasting polar ice sheets. The configuration of continents created large inland seas and richly diverse coastal environments. On land, gymnosperm-dominated forests and a variety of other plants supported a diverse herbivore fauna, while seas housed a range of marine reptiles, ammonites, and fish. The Late Jurassic also marks important steps in the evolution of birds, with the fossil record capturing early avian forms such as Archaeopteryx from prominently preserved sites like Solnhofen Limestone.

Geology and paleogeography

Continental configurations and plate tectonics
- The late phase of the breakup of Pangaea opened new ocean basins and shallow seaways. This reorganization set the stage for modern ocean circulation patterns and helped create distinct continental biogeographic provinces.
- The early stages of the Atlantic Ocean’s formation began to appear as rifting progressed, influencing coastlines and sedimentation patterns around the world.
Basins, seas, and sedimentation
- Widespread inland seas and epicontinental basins developed in various regions, producing favorable conditions for the deposition of lacustrine and marine sediments that preserve fossils from multiple environments.
- Notable sedimentary records come from western North America, Europe, Africa, and parts of Asia, each documenting how regional climates and tectonics shaped local ecosystems.

Climate and environmental context

Global warmth and sea level
- The Late Jurassic climate was generally warm, with elevated CO2 levels contributing to high atmospheric and ocean temperatures. Sea levels were high, creating shallow, expansive marine habitats as well as humid, forested coasts.
Ecosystem mosaics
- Coastal and floodplain forests supported a diversity of herbivores, while arid or semi-arid interiors persisted in some regions, reflected in the distribution of fossil assemblages across continents.
- The oceans hosted diverse assemblages of invertebrates, ray-finned fishes, marine reptiles, and early forms that would contribute to later marine radiations.

Life and ecosystems

Dinosaurs and major vertebrate groups
- Sauropods remained among the most successful large herbivores, with gigantism exemplified in certain lineages. Other herbivores (including ornithischians) diversified in parallel, occupying a range of feeding strategies.
- Theropods included apex predators and mid-sized hunters, contributing to complex terrestrial food webs.
- Birds were represented by early avian forms such as Archaeopteryx, illustrating an important transition in the dinosaur-bird relationship.
Marine life and reptiles
- In marine realms, plesiosaurs, ichthyosaurs, and various marine reptiles thrived alongside ammonites and fish, indicating robust oceanic ecosystems.
- Ammonites, belemnites, and other invertebrates documented in fossil beds provide key biostratigraphic markers used to correlate across regions.
Plants and ecosystems
- Forests and plant communities were dominated by conifers and other gymnosperms, with cycads and ginkgo relatives contributing to a diverse flora that supported herbivores and, in turn, higher trophic levels.

Notable fossil sites and formations

Morrison Formation (western North America)
- This famous Late Jurassic sequence records a semi-arid to mixed environment with river systems and floodplains. It preserves a rich dinosaur fauna, including sauropods and theropods, and is a cornerstone for understanding North American Late Jurassic ecosystems. See also Morrison Formation.
Solnhofen Limestone (Germany)
- A remarkable Lagerstätte dating to the Late Jurassic (Tithonian) that preserves exceptionally detailed fossils in a shallow marine setting. Among its most famous specimens are early birds and feather impressions, contributing significantly to discussions of flight and feather evolution. See also Solnhofen Limestone.
Kimmeridge Clay Formation (southern England)
- A Late Jurassic marine sequence that records offshore to nearshore conditions and a diverse marine life, helping to illuminate oceanic life and climate at the time. See also Kimmeridge Clay Formation.
Other regional records
- Across continents, additional formations contribute to a mosaic of environments, including coastal lagoons, floodplains, and open seas that collectively document the global variety of Late Jurassic life. See also Jurassic and Pangaea for broader context.

Evolutionary significance and debates

Tempo and pattern of dinosaur diversification
- The Late Jurassic shows substantial diversification and turnover within dinosaur faunas, with regional differences reflecting local climate, geography, and ecosystem structure. Ongoing research continues to refine timing and drivers of these dynamics, including how ecosystem changes influenced the rise of particular lineages.
Early birds and the origin of flight
- The relationship between non-avian theropods and early birds remains a central topic in vertebrate paleontology. Fossil evidence from sites like the Solnhofen Limestone provides critical data for reconstructing the anatomy and capabilities of early avians such as Archaeopteryx and for testing hypotheses about the origins of flight.
Paleogeography and climate interpretation
- Revisions in the age and nature of sedimentary deposits, as well as improved radiometric dating and biostratigraphy, continue to refine reconstructions of Late Jurassic climates and continental configurations. Researchers debate how regional climate variations and tectonic activity shaped the distribution of flora and fauna.
Fossil preservation and sampling bias
- The record from the Late Jurassic reflects taphonomic biases inherent in fossil preservation. Lagerstätten like the Solnhofen Limestone provide unusually complete specimens, while other regions yield sparser data, complicating global comparisons and requiring cautious synthesis.