One such breakthrough led by Griffith University’s Australian Research Centre for Human Evolution (ARCHE), in collaboration with international partners, comes from the exploration of underground settings, including caves and lava tubes, which have remained largely untapped reservoirs of archaeological abundance in Arabia.

Through meticulous excavation and analysis, researchers have uncovered a wealth of evidence at Umm Jirsan, spanning from the Neolithic to the Chalcolithic/Bronze Age periods (~10,000-3,500 years ago).

“Our findings at Umm Jirsan provide a rare glimpse into the lives of ancient peoples in Arabia, revealing repeated phases of human occupation and shedding light on the pastoralist activities that once thrived in this landscape,” said Dr Mathew Stewart, the lead researcher and a Research Fellow at ARCHE.

“This site likely served as a crucial waypoint along pastoral routes, linking key oases and facilitating cultural exchange and trade.”

Rock art and faunal records attest to the pastoralist use of the lava tube and surrounding areas, painting a vivid picture of ancient lifeways.

Depictions of cattle, sheep, goat and dogs corroborate the prehistoric livestock practices and herd composition of the region.

Isotopic analysis of animal remains indicates that livestock primarily grazed on wild grasses and shrubs, while humans maintained a diet rich in protein, with a notable increase in the consumption of C3 plants over time, suggesting the emergence of oasis agriculture.

“While underground localities are globally significant in archaeology and Quaternary science, our research represents the first comprehensive study of its kind in Saudi Arabia,” added Professor Michael Petraglia, Director of ARCHE.

“These findings underscore the immense potential for interdisciplinary investigations in caves and lava tubes, offering a unique window into Arabia’s ancient past.”

The research at Umm Jirsan underscores the importance of collaborative, multidisciplinary approaches to archaeological inquiry and highlights the significance of Arabia’s archaeological heritage on the global stage.

Researchers involved in this study work in close partnership with the Heritage Commission, Saudi Ministry of Culture, and the Saudi Geological Survey. Additional partners include King Saud University and key institutions in the UK, the USA, and Germany.

Father and daughter, Justin and Ruby Reynolds from Braunton, Devon, found the first pieces of the second jawbone to be found in May 2020, while searching for fossils on the beach at Blue Anchor, Somerset. Ruby, then aged 11, found the first chunk of giant bone before searching together for additional pieces.

Realising they had discovered something significant, they contacted leading ichthyosaur expert, Dr Dean Lomax, a palaeontologist at The University of Manchester. Dr Lomax, who is also a 1851 Research Fellow at the University of Bristol, contacted Paul de la Salle, a seasoned fossil collector who had found the first giant jawbone in May 2016 from further along the coast at Lilstock.

Dr Dean Lomax said: “I was amazed by the find. In 2018, my team (including Paul de la Salle) studied and described Paul’s giant jawbone and we had hoped that one day another would come to light. This new specimen is more complete, better preserved, and shows that we now have two of these giant bones — called a surangular — that have a unique shape and structure. I became very excited, to say the least.”

Justin and Ruby, together with Paul, Dr Lomax, and several family members, visited the site to hunt for more pieces of this rare discovery. Over time, the team found additional pieces of the same jaw which fit together perfectly, like a multimillion-year-old jigsaw.

Justin said: “When Ruby and I found the first two pieces we were very excited as we realised that this was something important and unusual. When I found the back part of the jaw, I was thrilled because that is one of the defining parts of Paul’s earlier discovery.”

The last piece of bone was recovered in October 2022.

The research team, led by Dr Lomax, revealed that the jaw bones belong to a new species of giant ichthyosaur that would have been about the size of a blue whale. Comparing the two examples of the same bone with the same unique features from the same geologic time zone supports their identifications.

The team have called the new genus and species Ichthyotitan severnensis, meaning “giant fish lizard of the Severn.”

The bones are around 202 million years old, dating to the end of the Triassic Period in a time known as the Rhaetian. During this time, the gigantic ichthyosaurs swam the seas while the dinosaurs walked on land. It was the titans’ final chapter, however — as the story told in the rocks above these fossils record a cataclysm known as the Late Triassic global mass extinction event. After this time, giant ichthyosaurs from the family known as Shastasauridae go extinct. Today, these bones represent the very last of their kind.

Ichthyotitan is not the world’s first giant ichthyosaur, but de la Salles’ and Reynolds’ discoveries are unique among those known to science. These two bones appear roughly 13 million years after their latest geologic relatives, including Shonisaurus sikanniensis from British Columbia, Canada, and Himalayasaurus tibetensis from Tibet, China.

Dr Lomax added: “I was highly impressed that Ruby and Justin correctly identified the discovery as another enormous jawbone from an ichthyosaur. They recognised that it matched the one we described in 2018. I asked them whether they would like to join my team to study and describe this fossil, including naming it. They jumped at the chance. For Ruby, especially, she is now a published scientist who not only found but also helped to name a type of gigantic prehistoric reptile. There are probably not many 15-year-olds who can say that! A Mary Anning in the making, perhaps.”

Ruby said: “It was so cool to discover part of this gigantic ichthyosaur. I am very proud to have played a part in a scientific discovery like this.”

Further examinations of the bones’ internal structures have been carried out by master’s student, Marcello Perillo, from the University of Bonn, Germany. His work confirmed the ichthyosaur origin of the bones and revealed that the animal was still growing at the time of death.

He said: “We could confirm the unique set of histological characters typical of giant ichthyosaur lower jaws: the anomalous periosteal growth of these bones hints at yet to be understood bone developmental strategies, now lost in the deep time, that likely allowed late Triassic ichthyosaurs to reach the known biological limits of vertebrates in terms of size. So much about these giants is still shrouded by mystery, but one fossil at a time we will be able to unravel their secret.”

Concluding the work, Paul de la Salle added: “To think that my discovery in 2016 would spark so much interest in these enormous creatures fills me with joy. When I found the first jawbone, I knew it was something special. To have a second that confirms our findings is incredible. I am overjoyed.”

The new research has been published today in the open access journal PLOS ONE.

Ruby, Justin and Paul’s discoveries will soon go on display at the Bristol Museum and Art Gallery.

Lomax said: “This research has been ongoing for almost eight years. It is quite remarkable to think that gigantic, blue whale-sized ichthyosaurs were swimming in the oceans around what was the UK during the Triassic Period. These jawbones provide tantalising evidence that perhaps one day a complete skull or skeleton of one of these giants might be found. You never know.”

The warming experiments led to a 1.4 degrees Celsius increase in air temperature and a 0.4 degrees increase in soil temperature, along with a 1.6 percent drop in soil moisture. These changes boosted ecosystem respiration by 30 percent during the growing season, causing more carbon to be released because of increased metabolic activity in soil and plants. The changes persisted for at least 25 years after the start of the experimental warming — which earlier studies hadn’t revealed.

“We knew from earlier studies that we were likely to find an increase in respiration with warming, but we found a remarkable increase — nearly four times greater than previously estimated, though it varied with time and location,” says Sybryn Maes of Umeå University, the study’s lead author.

The increase in ecosystem respiration also varied with local soil conditions, such as nitrogen and pH levels. This means that differences in soil conditions and other factors lead to geographic differences in the response — some regions will see more carbon release than others. Understanding the links between soil conditions and respiration in response to warming is important for creating better climate models.

“Our work represents the first assessment of ecosystem respiration response to experimental warming across such a broad environmental gradient in the tundra, incorporating a comprehensive set of environmental drivers,” says Associate Professor Ellen Dorrepaal of Umeå University.

The study also offers a broader perspective on Arctic and alpine regions by predicting increases in respiration across the whole tundra area together with more detailed information about variation in the sensitivity of the response.

“We see that some areas, particularly parts of Siberia and Canada, exhibit greater sensitivity to warming,” says Professor Matti Kummu of Aalto University. “We anticipate an increase in respiration across the whole Arctic and alpine tundra, but more in situ data, particularly on the local soil conditions, is key to addressing the outstanding uncertainties and refining our predictions.”

Understanding how ecosystems shift in response to climate change and how these changes feed back into the climate is vital to get an accurate picture of how our world will change. These findings serve as an important baseline for improved climate models, but the researchers plan to refine them further by analyzing how the experimental sites change over time and expand the experiment’s scope to include new sites.