Ma means “million years ago”
A label like 150 Ma means approximately 150 million years before the present. Older numbers sit to the left, younger ones to the right, ending at the K–Pg boundary around 66 Ma.
Deep time
When did they live?
Each horizontal bar is a genus (not every species on Earth—ranges are simplified). Drag the scrubber to zoom toward the young end of the axis (the Late Cretaceous). Bars outside the focused window fade.
252 Ma
159 Ma
66 Ma
Triassic
Jurassic
Cretaceous
Mass extinction: Non-avian dinosaurs disappear from the fossil record at the K–Pg boundary (~66 Ma). Read the dedicated page for mechanisms and survivors: End of an era.
Species gallery uses the same genera with longer descriptions.
How To Read Deep Time
Geological time can feel abstract at first. A few concepts make this chart much easier to interpret.
Bars show named genera, not every species
Each row is a genus-level summary. That keeps the graphic readable, but it also means each bar compresses variation between species, specimens and debates over exact boundaries.
First and last appearances are estimates
Paleontologists date fossils through stratigraphy, radiometric dates from associated rocks and comparisons between formations. The fossil record rarely captures the exact first or last individual of a lineage.
Absence is not proof of total absence
A genus may appear “missing” in some interval because suitable rocks were not preserved, exposed or sampled. Fossil history is shaped by both biology and geology.
Why zoom toward the end?
The Late Cretaceous contains many of the most famous genera, but the timeline is intentionally broad enough to show that the dinosaur story starts much earlier. Zooming makes it easier to compare the crowded last chapters without losing the full Mesozoic frame.
What to compare as you browse
Look for overlap between predator and herbivore lineages, note how long some groups persist, and compare Jurassic giants with Cretaceous specialists. The interesting pattern is not only who lived when, but which body plans keep returning.
Milestones Hidden Inside the Timeline
A long chart can feel overwhelming, so here are some of the big patterns it helps reveal.
Early dinosaur experimentation
The oldest part of the chart shows that dinosaurs start as part of a wider archosaur radiation rather than appearing fully dominant from day one. Their later success is a long story, not a single explosive event.
Jurassic giant-herbivore world
Long Jurassic spans for sauropodomorphs highlight just how successful giant herbivory became. Once those body plans settled into major ecosystems, they remained central for an enormous stretch of time.
Cretaceous specialization
In the later part of the chart you can compare more specialized lineages: horned dinosaurs, duck-bills, tyrannosaurs, dromaeosaurs, titanosaurs and odd theropods such as therizinosaurs. The late Mesozoic is crowded with ecological variety.
The abrupt edge at 66 Ma
The shared stop at the K–Pg boundary is a visual reminder that the end of non-avian dinosaurs was not a slow fade stretched evenly across all groups. It is a sharp geological and ecological break in the record.