Timeline Explorer

Interactive geologic timeline with dinosaur placement

Explore the Mesozoic Era through an interactive timeline spanning 186 million years. See when each dinosaur lived, which species coexisted, and how ecosystems changed from the Triassic through the Cretaceous.

252 Ma Mesozoic Era — Age of Dinosaurs 66 Ma
TRIASSIC
JURASSIC
CRETACEOUS

Click on a period in the timeline above to explore.

How to Use

  1. 1
    Set your time range

    Use the period selector to zoom into the Triassic, Jurassic, or Cretaceous, or drag the handles on the full Mesozoic bar to define a custom window spanning any span of millions of years.

  2. 2
    Filter by clade or region

    Apply filters for major clades such as Theropoda or Sauropodomorpha, or narrow by continent to see which species coexisted in a specific region during your selected interval.

  3. 3
    Tap a species bar for details

    Each horizontal bar represents the known temporal range of a species based on the stratigraphic age of its type formation. Tap any bar to open a summary panel with taxonomy, type locality, and key references.

About

The Mesozoic Era is divided into three periods — Triassic, Jurassic, and Cretaceous — each separated by major faunal transitions. Dinosaurs first appeared in the Carnian stage of the Triassic, approximately 231 million years ago, based on records from the Ischigualasto Formation in Argentina. For most of the Triassic they remained a subordinate component of terrestrial ecosystems dominated by other archosaur groups.

The Jurassic saw the first truly global dinosaur radiation. Gondwana and Laurasia, the two supercontinent fragments produced by the break-up of Pangaea, still had intermittent faunal connections, explaining why closely related sauropods occur in both North America and Africa. By the Early Cretaceous, further continental separation had produced increasing faunal provincialism, with distinct assemblages evolving independently on each landmass.

Stratigraphy — the study of rock layers and their ages — is the foundation of any geological timeline. The International Commission on Stratigraphy maintains the official Geological Time Scale, which assigns absolute ages to stage boundaries using a combination of radiometric dating, magnetostratigraphy, and biostratigraphy. The DinoFYI timeline uses this standard framework, with all formation ages traceable to the most recent edition of the ICS chart.

FAQ

How are the age ranges for each dinosaur determined?
Age ranges are derived from the radiometric dates assigned to the geological formations in which a species was found. Uranium-lead dating of volcanic ash layers (tephrochronology) within or adjacent to fossil-bearing strata provides the most precise dates. Where direct radiometric dates are unavailable, biostratigraphic correlation with better-dated formations is used. Ranges therefore reflect formation ages, not the precise lifespan of a species, which is always shorter.
Which geological period had the greatest dinosaur diversity?
The Late Cretaceous (roughly 100 to 66 million years ago) shows the highest described species richness in the fossil record, driven in part by the break-up of Pangaea into separate landmasses that promoted geographic isolation and speciation. However, Jurassic deposits, especially the Morrison Formation in North America and the Tendaguru Beds in Tanzania, preserve spectacular faunas of giant sauropods and large theropods. Diversity estimates are heavily influenced by sampling bias — well-studied formations yield more named species.
Did T. rex and Stegosaurus ever coexist?
No. Stegosaurus lived during the Late Jurassic, approximately 155 to 150 million years ago, while Tyrannosaurus rex is known only from the very end of the Cretaceous, around 68 to 66 million years ago. The temporal gap between them is greater than the gap between T. rex and modern humans. This illustrates a common misconception: the Mesozoic Era was not a single moment but an immense expanse of geological time during which faunas changed dramatically.
What caused the transition from Triassic to Jurassic dinosaur faunas?
The end-Triassic extinction event, around 201 million years ago, eliminated many competing archosaur lineages, including aetosaurs, phytosaurs, and large rauisuchians. This ecological release allowed dinosaurs, which had been a minority component of Triassic faunas, to diversify rapidly into the vacated niches. Early Jurassic dinosaur faunas are characterised by a proliferation of sauropodomorphs and the first large theropods.
How reliable are first and last appearance data in the timeline?
First and last appearances are bounded by the known fossil record and are therefore minimum estimates of a lineage's true temporal range. The Signor-Lipps effect means that a species' actual last occurrence likely predates the apparent last occurrence in the fossil record. Conversely, ghost lineages — phylogenetically inferred but unsampled intervals — suggest some lineages existed long before their first known fossil. The timeline marks these uncertainties with dashed range extensions where relevant.