Dinosaur fossils are incredibly rare in Western Australia. Most of what we understand about dinosaurs in the State comes from a few isolated bones, and trackways (sets of footprints) found near Broome. Besides dinosaurs, the Mesozoic was filled with other distinctive reptile groups, including crocodiles, pterosaurs (flying reptiles) and a range of marine reptile groups. None of these groups are dinosaurs, although some (crocodiles and pterosaurs) were related to dinosaurs. Pterosaurs and various marine reptiles of this age have also been discovered in Western Australia.
The Mesozoic era, commonly known as the Age of the Dinosaurs, is a subdivision of geological time extending from 252 to 66 million years ago. We divide the era into three periods:
- the Triassic (252–201 million years ago),
- the Jurassic (201–145 million years ago), and
- the Cretaceous (145–66 million years ago).
The Mesozoic era started and ended with two big mass extinctions — the Permian–Triassic extinction event (around 252 million years ago) and the Cretaceous–Paleogene extinction event (around 66 million years ago).
The Mesozoic era began and ended with two major mass extinctions: the Permian–Triassic (252 million years ago) and Cretaceous–Paleogene (66 million years ago). The Permian–Triassic event is the most devastating in history, wiping out over 85 per cent of species, while the Cretaceous–Paleogene event led to the extinction of 75 per cent of species.
This chart summarises the major groups of reptiles discussed on this page, including when in the Mesozoic they lived and one interpretation of how the groups may be related to each other.
Dinosaurs in Western Australia
Dinosaurs, first appearing in the Late Triassic, were the most famous large reptiles of the Mesozoic, with rapid diversification in the Jurassic and Early Cretaceous. Other reptiles like ichthyosaurs, plesiosaurs, mosasaurs, and pterosaurs were related but not dinosaurs. Except for birds, dinosaurs went extinct at the end of the Cretaceous.
Fossils in Western Australia are scarce, including:
- A partial tibia from Ozraptor subotaii (Middle Jurassic, c. 170 million years old) near Geraldton.
- A vertebra from an unknown dinosaur, possibly a sauropod, also near Geraldton.
- A toe bone from a small theropod near Gingin, potentially older than the surrounding Late Cretaceous rock.
The low number of dinosaur fossils in the State is due to limited exposure of suitable rocks and environments for bone preservation, with river and swamp deposits being the best for fossilisation. Factors like rapid river flow or slow sedimentation complicate preservation.
Dinosaur footprints in Broome
The strongest evidence of dinosaurs in Western Australia comes from the Lower Cretaceous Broome Sandstone (about 130 million years old) near Broome. Extensive rock surfaces along beaches reveal numerous dinosaur footprints, ranging from a few centimeters to over a meter across, including some of the world's largest tracks.
These footprints represent a variety of herbivores and carnivores, with 21 identified track types, including sauropods, theropods, ornithopods, and ankylosaurs—matching groups found elsewhere in Australia despite no bones being discovered in the west. Stegosaurs are also recorded, though absent from other Australian sites.
The Broome trackways provide key insights into Australia's dinosaur diversity, community structure, and movement, earning international significance and a spot on the Australian National Heritage List in 2011. Many tracks are visible only at low tide and may erode over time, though new ones may emerge. Unfortunately, some footprints have been stolen, including a rare stegosaur footprint in 1996.
Giant reptiles of the Mesozoic
Dinosaurs were not the only large animals to live during the Mesozoic era — pterosaurs and a variety of marine reptile groups are known from Western Australia during this time.
Flying wonders
Pterosaurs were the first vertebrates to achieve powered flight. Though closely related to dinosaurs and crocodiles, they were distinct members of Archosauria. Emerging in the Late Triassic, they dominated the skies before birds evolved, with diverse diets ranging from fish to small vertebrates. Some, like Quetzalcoatlus, had wingspans up to 11 metres — like an ultralight plane.
Pterosaur fossils are rare in Western Australia, with finds including a partial ulna from the 70-million-year-old Miria Formation near Exmouth and a jaw fragment from Gingin. They are also scarce across Australia, with isolated bones found in Queensland, Victoria, and New South Wales, leaving much to discover about Mesozoic flying reptiles.
Marine terrors
Like pterosaurs, Mesozoic marine reptiles were not dinosaurs and were unrelated to each other. These include:
- Ichthyosaurs – fish- or dolphin-like reptiles with large eyes.
- Mosasaurs – elongated, crocodile-like reptiles related to snakes and lizards.
- Plesiosaurs – paddle-limbed reptiles, including long-necked elasmosaurs and short-necked pliosaurs.
Western Australia has many marine reptile fossils, though most are fragmentary. Leptocleidus clemai from the Muderong Shale near Kalbarri is the most complete Mesozoic reptile skeleton found in the state.
Marine reptiles are common across Australia, especially in Queensland and New South Wales. Around 110 million years ago, the Eromanga Sea covered this region, preserving a rich diversity of vertebrate fossils, including dinosaurs, marine reptiles, pterosaurs, and early mammals.
Precious coprolites
Fossil dung, or coprolites, is common in the fossil record but can be mistaken for non-fossil nodules. Like other fossils, coprolites undergo physical and chemical changes during fossilisation, making them safe to handle. Although identifying the animal responsible is challenging, the variety of coprolite shapes and sizes helps us understand the types of animals in past environments.
While coprolites can lose their internal structure through mineral replacement, visible structures can reveal the animal's diet, aiding the reconstruction of past food webs. Due to difficulty in identifying them, coprolites are less studied than bones or shells.
In Western Australia, coprolites are found in areas with dinosaur or marine reptile fossils. Notably, large, well-formed coprolites in the Hill Spring area of the Gascoyne region, preserved in the Gearle Siltstone, suggest they were produced by large marine reptiles like plesiosaurs or ichthyosaurs.
The coprolites vary in shape, including 'cigar-shaped' ones that seem to have rolled on the seafloor before being buried. Their internal structure was not preserved, and the dung has been replaced by different minerals. Notably, the Gearle coprolites contain high amounts of platinum-group metals, gold, and silver, though not enough to make them economically viable for mining.
Cretaceous extinctions
By the end of the Cretaceous, around 66 million years ago, marine reptiles, pterosaurs, and most dinosaurs went extinct globally, with only birds surviving. Birds evolved from theropod dinosaurs earlier in the Mesozoic and were well-established by the Cretaceous. While no Mesozoic bird fossils have been found in Western Australia, rare remains and trackways have been discovered elsewhere in Australia. Crocodilians, along with birds and early mammals, also survived the extinction event.
The cause of the mass extinction is still debated, but many believe an asteroid impact was a key factor, supported by the Chicxulub crater in Mexico. Despite Western Australia's sparse Mesozoic fossil record, its remote regions remain underexplored, suggesting that new discoveries will continue to shed light on the State's ancient inhabitants.
Many of the fossils (especially bones) discussed here can be seen at the WA Museum Boola Bardip.
Do your part to protect Western Australia’s fossils by staying up to date with the restrictions and responsibilities related to fossils and State geoheritage, following all laws and regulations, and spreading the word to others (including tourists).
Further reading about dinosaurs and giant reptiles
Show moreDinosaur discoveries — a set of short articles or videos from the American Museum of Natural History describing recent dinosaur-related news or discoveries from around the world.
Dinosaur discovery online exhibition — online exhibition on dinosaurs and other plants and animals living in the Cretaceous Period from the Western Australian Museum.
Long, J 2004, It’s true! Dinosaurs never died: Allen & Unwin, Crows Nest, New South Wales, 88p.
Long, JA 1998, Dinosaurs of Australia and New Zealand and other animals of the Mesozoic Era: Harvard University Press, Cambridge, Massachusetts, USA, 188p.
University of California Museum of Paleontology: Those diverse diapsids.
Vickers-Rich, P and Rich, TH 1999, Wildlife of Gondwana: dinosaurs and other vertebrates from the ancient supercontinent: Indiana University Press, Bloomington, Indiana, USA, 304p.
