/ 13 April 2024

Wits team discover beetle that roamed alongside dinosaurs

Photo supplied

Ninety million years ago, a beetle with a sharp, scissor-like mouthparts, an elongated head and notably long antenna, roamed alongside dinosaurs in what is now the Orapa Diamond Mine in Botswana. 

It’s taken about 40 years but Sandiso Mnguni, a postdoctoral fellow at Genus, and his team at the University of the Witwatersrand have now unveiled the fossil, which sheds light on the evolutionary history of beetles. 

This particular specimen is part of the staphylinine rove beetles dating back to the Cretaceous period, about 90 million years ago. The discovery marks the first recorded fossil of a staphylinine rove beetle in Africa and in the Southern Hemisphere. 

The new research, published in the Journal of Entomological Science, describes the new species, Paleothius mckayi, and extends the geographical and temporal boundaries of the understanding of these ancient creatures.

This region of Botswana, known for its rich deposits of Cretaceous age, has become a pivotal site for understanding the biodiversity of the past, revealing a world where these beetles hunted alongside dinosaurs.

“We know this because the sediments from the deposits have been dated using isotopes that you find on the sediments, particularly those that are called zircons,” said Mnguni, who is a palaeoentomologist — the study of fossil insects

“They’ve given us the details of the sediments … and by virtue of the sediments being 90 million years old, then it means the insects are the same age. That’s how we know that they roamed around with dinosaurs because dinosaurs only became extinct 66 million years ago.”

The fossil find was excavated at the Orapa Diamond Mine in the 1980s and photographed without description. “It’s in three different sources and it was just pictures,” he said. “It was just to show the diversity we have from this particular deposit, which is the Orapa Diamond Mine.”

It was housed in the herbarium of the Evolutionary Studies Institute at Wits University, where it was photographed previously, until Mnguni stumbled upon it and ultimately described the specimen. 

Unique site

Paleothius mckayi is named in honour of Ian James McKay, a notable figure in the field of

palaeoentomology, who significantly contributed to the training of Mnguni.

This species was unearthed from lacustrine sediments — deposits that accumulate in lake environments. Its sharp, scissor-like mouthparts suggest a predatory lifestyle, hunting prey in the leaf litter surrounding a crater lake that once existed in this region.

The paper’s authors said that rove beetles, in general, are recognised for their highly mobile lifestyle and versatile habitat preferences, ranging from soil and leaf litter to water margins and even animal nests. 

These beetles play critical roles in controlling pest populations, breaking down organic matter and contributing to nutrient cycling in their ecosystems. 

The preservation of this newly described fossil as a flattened imprint provides a direct window into the widespread distribution of staphylinine rove beetles during the Cretaceous period. 

Until now, similar fossils have been found in diverse locations such as China, Russia, Myanmar and England, but the addition of Botswana to this list highlights the Orapa Diamond Mine as a crucial Cretaceous deposit in Africa with a rich biota encompassing various groups of plants and insects, the authors said.

“The site is actually very unique, it’s very important definitely for our heritage and knowing what was there and documenting diversity,” said Mnguni. “And it’s not only insects; you get plants from the same deposits. It’s a very nice deposit.”

While other researchers have “worked a bit” on the site, Mnguni noted that the last scientific paper produced from the deposit was in 2015 and he had “basically come in and resuscitated the whole thing”.  

Thriving alongside dinosaurs

The discovery shows that these types of beetles were not just present but thriving alongside dinosaurs, and they haven’t changed much over millions of years. This idea, that some creatures evolve very slowly, supports what scientists call “punctuated evolution” — the notion that evolution can happen in bursts following long periods of little change. 

Moreover, this beetle shares some family traits with another group of beetles, suggesting these groups have been related since the Jurassic period, even longer ago. 

“This beetle is a clue into the long, intricate history of life on Earth, showing us how interconnected and unchanged some life forms have been over the ages” and highlights the success of rove beetles in adapting to various environments without significant changes to their morphology,” according to the authors.

The intricate process of describing a new species from such fossils takes hours of detailed analyses. This painstaking work often requires repeated examinations to identify unique characteristics that justify the classification of a new species. 

“The more you look at the specimen, the better you’ll get at understanding it. You might notice details you missed before, which helps you describe it better,” Mnguni said.

The discovery of Paleothius mckayi also paves the way for future discoveries in the Orapa Diamond Mine. 

“There are more fossil rove beetles that will be described from the same deposit by the same authors in the near future, and there are also many fossil insects belonging in other groups that also await description,” the authors said.