115 сая жилийн настай үлэг гүрвэлийн яснаас цусны улаан эсийн ул мөр илрүүлжээ

The dinosaur’s name means “born of fire.” Paleontologists who described Aratasaurus museunacionali in 2020 combined the Tupi words for “born” and “fire” to honor Brazil’s National Museum in Rio de Janeiro, which burned in September 2018 and lost much of its collection.

The fossil itself had been at the museum since 2016, but it was stored in an area the flames did not reach, and it came through intact. Six years after the fire, the same leg bones are at the center of a much bolder claim.

An international team led by Curtin University geochemist Kliti Grice reports that the bones of Aratasaurus museunacionali contain mineralized red blood cells still carrying traces of heme, the iron-bearing part of hemoglobin that lets blood carry oxygen. The study appeared on November 2 in Proceedings of the National Academy of Sciences, and not everyone is convinced the structures are blood cells.

A Young Predator That Died on a Bacterial Mat

The fossil was found in 2008 in a gypsum mine in Santana do Cariri, in the Brazilian state of Ceará, and was at first mistaken for a pterosaur. Preparing it took years of slow, delicate work, because the bones were fragile and had to be freed from the surrounding rock under a microscope.

What emerged was a partial right hind leg from a meat-eating theropod about 3.1 meters (10 feet) long. The animal was roughly four years old and weighed around 34 kilograms (75 pounds) when it died, small for a predator whose distant relatives would later include the tyrannosaurs.

It died on a microbial mat, a layer of bacteria and archaea typical of coastal flats. Grice told ABC Australia that being engulfed in the mat probably helped enormously with preservation, and that the Brazilian scientists who sent her the bones had no idea anything special might be inside.

Tiny Shapes in the Blood Vessel Channels

Under the microscope, the team saw numerous small, rounded bodies packed inside the vascular canals, the channels in bone that once held blood vessels. Shape alone proves little, since minerals and microbes can produce convincing cell lookalikes, so the researchers combined imaging with several chemical tests.

Extracts from the bone contained heme B and an altered form of it, which was about 90 times more abundant, a sign that most of the heme had changed chemically during fossilization. Spectroscopy then detected the signature of a porphyrin, the ring structure at the heart of heme, inside the cell-like shapes themselves, along with iron, nitrogen and carbon.

The team also found hydroxyproline, an amino acid associated with collagen, and a manganese oxide mineral called hausmannite inside the structures. The researchers suggest its antioxidant properties may have helped shield the material. Tests for ancient DNA came back negative, so nobody is cloning this dinosaur anytime soon.

“To detect intact heme-derived molecules in 115-million-year-old red blood cells is astonishing,” Grice said in a Curtin statement, calling it “a landmark discovery.”

The Contamination Question

Porphyrins are everywhere in nature. Plants use them in chlorophyll, and bacteria make similar compounds for their own needs. The obvious worry is that the heme seeped in from the microbial mat, or came from microbes that later moved into the bone.

That has happened before. A 2019 study of Centrosaurus bones found recent organic material and living microbial communities inside the fossils, showing that buried bone can become a habitat with its own chemistry.

The team’s answer is chemical contrast. The surrounding mat was dominated by compounds from photosynthetic pigments, while the porphyrins in the bone extract were overwhelmingly heme-related. Even so, the paper acknowledges that heme-producing microbes cannot be completely ruled out.

Claims of dinosaur blood chemistry are not new either. In 1997, a team that included paleontologist Mary Schweitzer reported heme compounds in Tyrannosaurus rex bone, opening a debate that has never fully closed.

Experts Split on the Cells

Schweitzer, now an emeritus professor at North Carolina State University, told ABC she found the blood-cell evidence unconvincing. “I have no problem with the presence of heme and collagen in the bone matrix,” she said, while praising the authors for using multiple methods.

Her objection is size. One of the imaged “cells” measured roughly 15 microns, which she noted is smaller than nearly all red blood cells of non-mammals. Those cells keep their nucleus and tend to be larger as a result, as in today’s birds and reptiles.

Mauricio Barbi of the University of Regina, also not involved in the work, called the evidence convincing for mineralized structures consistent with red blood cells. He added that identifying them still involves interpretation, since what survives are chemical remnants and mineral structures rather than intact cells or hemoglobin.

To test how blood can mineralize in the kind of setting where Aratasaurus died, Curtin researchers have started an unusual experiment. They are trying to fossilize human blood using microbial mat samples collected from Shark Bay in Western Australia.

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