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Ecological view

Apex diversity through the Mesozoic

Stacked curves showing how many apex predator species of each clade were alive at each moment, based on our curated dataset. Reads the changing of the guard as a single picture: pseudosuchian dominance collapsing at the T-J boundary, carcharodontosaurid peak, tyrannosaurid explosion in the last ~25 Ma.

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Late Triassic Early Jurassic Middle Jurassic Late Jurassic Early Cretaceous Late Cretaceous 0 2 4 6 8 10 240 220 200 180 160 140 120 100 80 66 Millions of years ago Apex species alive
Pseudosuchia (terrestrial) 2
Early theropods 6
Megalosauridae + Spinosauridae 7
Allosauroidea + Carcharodontosauridae 8
Tyrannosauroidea 7
Abelisauridae 6
Megaraptora + other Coelurosauria 3
Marine reptiles 9
Sharks 3
How to read this chart

What the axes mean

The horizontal axis is time, in millions of years ago (Ma). It runs from 240 Ma on the left (early Mesozoic) to 66 Ma on the right (the end of the age of dinosaurs). The vertical axis counts how many apex predator species of each lineage were alive at that moment.

Why the curves are stacked

Each colored band is a clade (a branch of the tree of life, like "tyrannosaurs" or "mosasaurs"). The thicker a band at any moment, the more species of that group existed then. The total height at any point is the total apex predator diversity across all clades.

Four patterns worth noticing

  1. The T-J extinction (~201 Ma). The brown Pseudosuchia band collapses. The apex slot empties and then, within a few million years, early theropods (pale orange) take over the land.
  2. The Morrison peak (~155 Ma). Three large theropods coexist in North America — Allosaurus, Torvosaurus, Ceratosaurus — pushing the yellow Allosauroidea + Carcharodontosauridae band to an early high.
  3. Carcharodontosaurid dominance (~130–90 Ma). The yellow band thickens in both hemispheres, then fades around the Cenomanian-Turonian. The apex crown changes hands.
  4. Two empires at the end (last ~25 Ma). Tyrannosauridae (purple) rise in the north while Abelisauridae (pink) rise in the south, with almost no overlap. A split world, ended by K-Pg.

What we can infer

  • Apex slots are rarely empty. When one lineage collapses, another fills it within a few million years.
  • Two lineages can share a world when they partition prey or habitat — like spinosaurs and carcharodontosaurids in North African rivers around 94 Ma.
  • Turnover is sometimes global (T-J, K-Pg) and sometimes regional (carcharodontosaurids fade faster in Laurasia than in Gondwana).

What it doesn't tell you

  • It counts species, not individuals or biomass. A single T. rex species might have outweighed three rare Morrison apex combined.
  • The fossil record is patchy. Poorly sampled regions (Antarctica, central Africa, most of the deep ocean) push counts downward in an artificial way.
  • The curves should be read as a lower bound of real diversity — the actual ecosystems had more apex than we can count.
Counts per Ma step from the curated dataset of 53 apex species. This is a lower bound — rare or yet-to-be-added species will push any curve up.
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