{"id":186540,"date":"2021-04-19T16:56:59","date_gmt":"2021-04-19T14:56:59","guid":{"rendered":"https:\/\/www.myza.co.za\/what-an-unusual-fossil-reveals-about-parental-care-among-pre-mammalian-ancestors\/"},"modified":"2021-04-19T16:56:59","modified_gmt":"2021-04-19T14:56:59","slug":"what-an-unusual-fossil-reveals-about-parental-care-among-pre-mammalian-ancestors","status":"publish","type":"post","link":"https:\/\/www.myza.co.za\/press\/what-an-unusual-fossil-reveals-about-parental-care-among-pre-mammalian-ancestors\/","title":{"rendered":"What an unusual fossil reveals about parental care among pre-mammalian ancestors"},"content":{"rendered":"

South Africa\u2019s Karoo region<\/a> is world famous for its wealth of fossil remains. Many of these are from long extinct land animals that lived between 280 and 200 million years ago. This was a time before the dinosaurs, when all the landmasses were joined into the supercontinent of Pangaea<\/a>.<\/p>\n

Most of the fossil skeletons that have been found in the Karoo belong to therapsids<\/a>. These ancient reptilian precursors to mammals are often called \u201cmammal-like reptiles\u201d.<\/p>\n

But it is very rare to find therapsid skeletons preserved in underground fossilised burrow casts. These are ancient burrows that were filled by sediments (during a flood for example), and were later deeply buried by time and the elements and turned into rock.<\/p>\n

That\u2019s why a find<\/a> in the 1980s in the Namakwa district of South Africa\u2019s Northern Cape province, near Fraserburg, was especially significant. Skeletons found in the terminal chamber of spiral-shaped burrow casts demonstrated that they were excavated by a small herbivorous mammal-like reptile called Diictodon<\/em>. <\/p>\n

It wasn\u2019t clear why the animals might have gone underground but it was assumed to be mainly for body temperature regulation. Then, in 2014, some new burrow casts were found at the same site. These contained the scattered skeletons of adult and infant Diictodon<\/em>. Now, after a few years of careful study, we have been able to establish<\/a> that adult males were in the burrows, along with infants of the same species. <\/p>\n

This supports the idea that Diictodon<\/em> went underground to breed and also that adult males may have played a role in feeding and protecting their litter. This is a rare reproductive behaviour for most modern male mammalian species. These new finds indicate that Diictodon<\/em> was burrowing and giving some parental care to its young. This was long thought to be unique to mammals. Now we have evidence that this behaviour also existed in their remote cousins, the mammal-like reptiles and it deepens the root of \u201cmammalness\u201d \u2013 the point in time when mammal-like behaviours first emerged \u2013 even further than previously thought.<\/p>\n

Technology sheds light<\/h2>\n

Modern animals use burrows for a variety of reasons: avoiding predators, food hoarding, brooding, and avoiding extreme humidity and temperature fluctuations. <\/p>\n

In the fossil record it is not always clear what ancient animals were using their burrows for. Luckily, modern technology means that scientists are increasingly able to answer such questions. Our team worked with the European Synchrotron Radiation Facility<\/a> in Grenoble, France. <\/p>\n

The X-ray beam generated in this synchrotron is 100 billion times brighter than the more common medical X-ray scanners, making it possible to create much sharper images. The technique we used is also much more sensitive to density variation: this is essential when trying to see fossilised bones surrounded by rock that can have very similar density. Using this powerful X-ray beam, we could digitally extract all the bones entombed in the burrow\u2019s rock infill.<\/p>\n

Illustration of Diictodon warren in the ancient Karoo 260 million years ago.<\/span> Cedric Hunter, Iziko SA Museum<\/span><\/span> <\/figcaption><\/figure>\n

This meant we didn\u2019t have to physically break the infill or damage the fossil. Even better, we discovered a second infant Diictodon<\/em> that wasn\u2019t visible from the surface. This reinforces the interpretation of the burrow as a brooding chamber, a conclusion that would have remained out of reach without the synchrotron.<\/p>\n