> > “We can see it went in water deeper than 50 meters because it was preserved with a particular mineral called glauconite, which is a green phosphate mineral. And it only forms in cooler temperatures in water deeper than 50 meters,” explained Henderson.
> Surely this is nonsense.
It is not, though the problem here seems to be that you have badly misread it.
> You cannot tell the depths that a living creature swam, from the mineral deposits on its fossilized body!
Probably not, but this isn’t saying anything about the depths that a living creature swam, but the depths to which the corpse of a land-walking creature sank.
The three paragraphs before the one you quoted about how far it went (after death, not in life), with some marked ellisions for brevity:
A land-based megaherbivore preserved in an ancient seabed is not as uncommon as one might think. […] Scientists suspect its carcass may have been carried from a river to the sea in a flooding event; it may have bobbed at the surface upside-down for a few days before sinking into the ocean depths.
It would have been kept at the surface by what’s referred to as “bloat-and-float,” as the buildup of postmortem gasses would keep it buoyant. Modeling done by Henderson indicates its heavy armor would have rolled it onto its back, a position he suspects may have prevented ocean predators from scavenging its carcass.
Once the gases that kept it floating were expelled, Borealopelta sank to the ocean floor, landing on its back.
> Oh please. How is it possible to deduce the colouring of a fossilized creature?
“One way to determine an organism’s coloration has been to examine the structure of fossilized melanosomes under the microscope. Melanosomes are small storage sacs within cells that store pigment. Two main flavors of pigments are found in animal tissues called eumelanin and pheomelanin.[…] Classically, scientists have examined the microscopic structure to distinguish between eumelanosomes and pheomelanosomes. However, these structures are often difficult to distinguish microscopically and mineralized microbes can often be mistaken for these organelles. […]
“The genius of Wogelius and his collaborators was to study the chemistry of eumelanin and pheomelanin from modern surviving organisms and then apply what they found to ancient samples. It turns out that each form of melanin has a distinctive associated element – copper for eumelanin and zinc for pheomelanin. X-ray beams can be bounced off the fossil melanosomes, and the way they are reflected depends on the different elements of these pigments. The exact distribution of eumelanin and pheomelanin can be mapped onto a fossil’s structure, providing something like a ‘paint for numbers’ for the fossils! This technique has already been used to paint a picture of an extinct red mouse that lived 3 million years ago. Now investigators hope to use the technique to go even further back in time to capture pictures of the earliest organisms to roam the planet.”
https://sitn.hms.harvard.edu/flash/2019/color-dinosaur-actua...