Level 1 — Absolute Beginner

Dinosaurs lived a very long time ago. We find their bones in rock. The bones are called fossils. Usually only hard things stay. Soft things like skin and blood go away.

But now scientists have a surprise. They looked inside the leg bone of a small dinosaur from Brazil. Inside the bone they found tiny red blood cells.

The dinosaur died about 115 million years ago. Its name is Aratasaurus. It walked on two legs. It was not very big.

Why did the blood cells stay? The scientists think a special mineral covered them. The mineral is hard. It kept the cells safe for millions of years.

a dinosaur

A large animal that lived millions of years ago.

a bone

A hard white part inside the body of an animal or person.

a fossil

The remains of an old animal or plant kept in rock.

blood

The red liquid inside the body.

a cell

The smallest living part of a body.

a mineral

A hard natural substance found in rock.

soft

Easy to press or bend, not hard.

a scientist

A person who studies how the world works.

Level 2 — Elementary

An international team of scientists says it has found red blood cells, turned to stone, inside the leg bones of a dinosaur that lived about 115 million years ago. The work was published this week in a leading American journal, the Proceedings of the National Academy of Sciences.

The dinosaur is called Aratasaurus museunacionali. It was a small meat eating dinosaur that walked on two legs, and its bones were dug up in the north east of Brazil. The fossil was named in 2020 in honour of Brazil's National Museum, which lost much of its collection in a fire in 2018.

The team studied thin channels inside the bone, the tiny tubes where blood vessels once ran. Inside those channels they found round shapes the size and form of red blood cells. They also detected the chemical fingerprint of heme, the part of our blood that carries oxygen and gives blood its red colour.

Soft tissue almost never survives this long, so the researchers wanted to explain why these cells did. Their answer is a manganese mineral called hausmannite, which seems to have coated the cells soon after the animal died and locked them in place. The team also found pieces of amino acids, the building blocks of the protein collagen.

a journal

A magazine where scientists publish their research.

to dig up

To take something out of the ground.

a channel

A narrow passage through which something can pass.

a blood vessel

A tube in the body that carries blood.

oxygen

The gas in air that animals need to breathe.

soft tissue

The parts of a body that are not bone, such as muscle and skin.

to coat

To cover the surface of something with a thin layer.

protein

A substance in living things that builds and repairs the body.

Level 3 — Intermediate

A paper published this week in the Proceedings of the National Academy of Sciences makes a claim that would have been dismissed as impossible a generation ago: that mineralised red blood cells, complete with the chemical signature of heme, are still sitting inside the vascular canals of a dinosaur bone 115 million years after the animal died.

The specimen is the holotype of Aratasaurus museunacionali, a modest sized theropod recovered from the Araripe Basin in north eastern Brazil and formally described in 2020. Its name honours the Museu Nacional in Rio de Janeiro, which lost a large part of its collection to fire in 2018. The researchers examined the femur and tibia, concentrating on the microscopic canals that once carried blood vessels through living bone.

The team was led by Kliti Grice of Curtin University in Australia, with collaborators at the Japan Agency for Marine-Earth Science and Technology, the Brazilian National Museum, the Regional University of Cariri and Johns Hopkins University. Alexander Kellner, one of Brazil's best known palaeontologists, is a senior author. Alongside the cell like structures and heme derived molecules, the group reported amino acids associated with collagen, the principal protein of bone.

Preservation, not discovery, is the heart of the paper. Organic molecules normally break apart within thousands of years, so the authors looked for a mechanism and found one in hausmannite, a manganese oxide mineral that appears to have precipitated around the cells shortly after death and shielded them from water and oxygen. Claims of ancient biomolecules have a contested history in palaeontology, and independent laboratories will need to reproduce the heme signatures before the result is settled. If it holds, the method may apply to other fossils from the same chemical setting.

a holotype

The single specimen used to define a new species.

a theropod

A member of the group of mostly meat eating dinosaurs that walked on two legs.

a vascular canal

A microscopic tunnel in bone that carried blood vessels.

a palaeontologist

A scientist who studies fossils.

collagen

The main structural protein in bone, skin and tendon.

to precipitate

In chemistry, to come out of a liquid and form a solid.

a biomolecule

A molecule produced by a living organism.

to reproduce a result

To repeat an experiment and obtain the same finding.

Level 4 — Advanced

Palaeontology has spent three decades arguing about whether anything organic can outlast the Cretaceous. A paper in this week's Proceedings of the National Academy of Sciences advances the strongest version of the affirmative case yet assembled: mineralised structures with the size, shape and position of red blood cells, carrying detectable heme signatures, inside the vascular canals of a dinosaur limb bone laid down roughly 115 million years ago.

The fossil is the holotype of Aratasaurus museunacionali, a mid sized theropod from the Araripe Basin of north eastern Brazil, described in 2020 and named for the Museu Nacional in Rio de Janeiro, which lost most of its holdings in the 2018 fire. An international group led by Kliti Grice of Curtin University, with co-authors at the Japan Agency for Marine-Earth Science and Technology, the Brazilian National Museum, the Regional University of Cariri and Johns Hopkins University, and with the palaeontologist Alexander Kellner as a senior author, sectioned the femur and tibia and worked inward to the microscopic channels that once carried the animal's vasculature.

What distinguishes the study from earlier reports of dinosaur soft tissue is that it offers a chemical mechanism rather than an anomaly. Heme and the amino acid fragments of collagen should degrade within thousands of years under normal conditions. The authors argue that hausmannite, a manganese oxide, precipitated around the cells very soon after death, encasing them in a mineral shell that excluded oxygen and circulating water and arrested the reactions that would otherwise have destroyed them. The specific chemistry of the Araripe sediments, long celebrated for exceptional fossil preservation, is doing the work.

Scepticism is appropriate and the authors would expect it. The field remembers the long dispute over collagen peptides reported from a Tyrannosaurus femur, where contamination by modern biological material and by laboratory reagents proved extremely difficult to exclude. The persuasive next step is replication in independent laboratories using separate samples and different analytical routes. If the heme signatures survive that scrutiny, the significance extends past a single Brazilian theropod: it would identify a mineralogical fingerprint that tells researchers which fossil deposits are worth searching for molecular remains, and which are not.

the Cretaceous

The geological period from about 145 to 66 million years ago.

vasculature

The system of blood vessels in a body or organ.

to section

To cut something into thin slices for examination.

an anomaly

Something that does not fit the expected pattern.

to degrade

To break down into simpler substances over time.

contamination

The unwanted presence of material from another source.