Paleontologists already know that the extinct marine reptile ichthyosaurs were enormous. Some newly described jawbone fossils uncovered in England represent a new ichthyosaur species. The bones indicate that the ocean titan may have been over 82 feet long, and even pushed the possible limits of vertebrate size. The new find is detailed in a study published April 17 in the open-access journal PLOS ONE.
“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,” study co-author and University of Manchester paleontologist Dean Lomax said in a statement. “These jawbones provide tantalizing evidence that perhaps one day a complete skull or skeleton of one of these giants might be found. You never know.”
Meet the ichthyosaurs
Ichthyosaurs are an extinct group of reptiles that are distant relatives of today’s lizards and snakes. They had long fins and were potentially ambush predators like today’s great white sharks and wolves, feeding on fish and other marine dwellers. Ichthyosaurs also may have followed migration patterns that are similar to today’s whales.
These ancient, swimming reptiles may have been the biggest animals of all time.]
They lived 228 to 112 million years ago and they were most abundant during the Triassic and Jurassic eras. There are over 100 known ichthyosaur species. Their remains have been found in parts of Asia, North America, and Europe. A fossil deposit in present day Nevada may have even been an ichthyosaur birthing ground.
Solving a prehistoric jigsaw puzzle
Over several years, a team from The University of Manchester has discovered and pieced together individual fragments of an ichthyosaur jawbone. A jawbone uncovered in 2016 at the Westbury Mudstone Formation in Somerset was similar to one collected from the same rock formation just a few miles away. The team believe that both of these jawbones belong to a previously undescribed species of ichthyosaur.
In 2020, a father and daughter from Devon named Justin and Ruby Reynolds found the first pieces of the second jawbone to be found in May 2020. Ruby was 11 years-old at the time and found the first chunk of giant bone before searching for more pieces. The family contacted Lomax and fossil collector and study co-author Paul de la Salle, who found the first jawbone in 2016.
“I was amazed by the find. In 2018, my team studied and described Paul’s giant jawbone and we had hoped that one day another would come to light,” said Lomax. “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.”
Over time, several members of the Reynolds family, Paul, and Lomax’s research team visited the site to hunt for more pieces of this rare discovery. They found more pieces of the same jaw which happened to fit together perfectly.
Reasons why children are great at finding fossils on their own.]
“I was very excited to find a part of this huge ichthyosaur. I am very happy to have been involved in a scientific discovery like this,” Ruby Reynolds said in a statement. Ruby and her father are both credited as authors of the new study.
A recent type of ichthyosaur
The last piece of bone was found in October 2022. The research team discovered that the jaw bones are from a unique species of large ichthyosaur they called Ichthyotitan severnensis, or “giant fish lizard of the Severn.” It was probably the size of the blue whalelargest living organism today. Comparing the two instances of the same bone with the same distinct features from the same geologic time period helps support the idea that it is a new species.
The bones are approximately 202 million years old and come from the end of the Triassic Period referred to as the Rhaetian. During the Rhaetian, enormous ichthyosaurs were swimming while dinosaurs were walking on land. However, this was when ichthyosaurs’ time on Earth ended. They became extinct during the Late Triassic global mass extinction event about 200 million years ago, and these bones represent the very last of their kind. Dinosaurs would not survive for another 134 million years.
While this new finding is not the first large ichthyosaur, these results are unique compared to those known to science. These two bones are around 13 million years younger than their most recent geological relatives. These include Shonisaurus sikanniensis from British Columbia, Canada, and Himalayasaurus tibetensis from Tibet, China. A closer examination of the bones’ inner structures also confirmed that the animal was probably still growing at the time of its death.
“The abnormal periosteal growth of these bones suggests bone development strategies that are yet to be understood, which were likely used by late Triassic ichthyosaurs to reach the known biological limits of vertebrates in terms of size,” Marcello Perillo, a study co-author and a paleobiology master’s student at the University of Bonn in Germany, stated. “There is still much mystery surrounding these giants, but we will gradually uncover their secrets with each new fossil we find.”
The ichthyosaur bones will soon be exhibited at the Bristol Museum and Art Gallery.
