The First Dinosaurs May Be Hidden in Earth’s Least Accessible Places

Ancient fossils of the world’s very first dinosaurs may be buried in places almost impossible to investigate, according to new research from University College London and the UK’s Natural History Museum.

Oldest Dinosaur Fossils and Their Evolutionary Significance

The oldest dinosaur fossils currently on record date back around 230 million years. These specimens, recovered from sites that were once part of Gondwana – the southern half of the late Paleozoic supercontinent Pangea – occupy relatively distant branches of the dino family tree, suggesting they had already been evolving and perhaps dispersing across the world for millions of years.

What’s more, the discovery of dinosaurs from that same period in what was the supercontinent’s northern landmass, Laurasia, has only upturned our understanding of dinosaur history further.

Convinced that paleontologists have not yet traced the true point of origin of dinosaurs, they now suspect that Earth’s most hard-to-get places could hide the starting point for all ‘terrible lizards.’

The Fossil Gap Around the Equator

Between each hemisphere’s claims to the earliest fossils lies a massive gap in the record around the equator. In places where we have found no dinosaur fossils, it’s easy to assume that there were no dinosaurs, but that might not necessarily be the case.

Fossils can only be preserved when the conditions are just right. For trace fossils, like footprints, the imprint in soft mud fills with loose sand, which then compacts. To form a body fossil, the animal carcass covers itself with mud or silt soon after death to prevent it from rotting away completely.

But even if the perfect fossil formed, we might not necessarily find it, especially in locations that are difficult to reach. In a new paper led by University College London paleontologist Joel Heath, the authors point out that paleontological expeditions in the Amazon and the Sahara haven’t been particularly common, or easy-going.

And that’s a problem, because these are the places where they suspect we might find dinosaurs’ more ancient evolutionary history.

“Paleontological expeditions to these regions may be less common as a result of the harsh environment of the Sahara and inaccessibility of many areas of the Amazon,” they write.

Socioeconomic factors, the legacy of colonialism, and political instability have likely hindered research efforts in these regions, as documentation shows.

Modeling Dinosaur Evolution Using Available Fossils

Their study modeled the radiation of dinosaurs in reverse, using known dinosaur fossils, taxonomic data on both dinosaurs and their reptile relatives, and the geography of the period. Rather than assuming that places with no fossils have no dinosaurs, the researchers categorized these regions as having missing information.

And since we don’t really know exactly how the oldest known dinosaurs are related to each other, they modeled three different scenarios based on proposed evolutionary trees.

A model in which silesaurids (considered more like dinosaur cousins than dinosaurs) are ancestors of ornithischian dinosaurs most strongly supports a low-latitude Gondwanan origin, with proof potentially lying in the Sahara and the Amazon.

Ornithischians and the Missing Fossils

Ornithischians are one of the three main dinosaur groups that is oddly absent from the early dinosaur fossil record, but silesaurids as their ancestors would fill some of that gap.

Conveniently, low-latitude Gondwana is also the midpoint between the earliest dinosaur fossils in our current record.

Heath says, “So far, researchers have not found dinosaur fossils in the regions of Africa and South America that once formed this part of Gondwana.”

“However, this might be because researchers haven’t stumbled across the right rocks yet, due to a mix of inaccessibility and a relative lack of research efforts in these areas.”

Read the original artilce on: Science Alert

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