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We know about the dinosaurs that inhabited Gondwana in the Cretaceous period from excavations in South America, Africa and even Antarctica. But Australia, which was also part of the supercontinent, remains a blank spot. It is not surprising that each new find from there has strange discoveries. This is what happened with five theropods described in the work of Australian paleontologists.
The state of Victoria in southern Australia is the richest in Cretaceous sauropod dinosaur fossils, especially in its southernmost region. The majority of the fossils found there are small, many of which are unidentified and undescribed. This is all the more significant when scientists from the Victoria Museum Research Institute and Monash University in Australia discover the continent's first carcharodontosaur and the world's oldest megaraptor. The article about this is published in the journal Journal of Vertebrate Paleontology.
The Australian finds are represented by bones from geological formations of different ages - 121-118 and 113-108 million years old. Two large tibiae belonged to carcharodontosaurids, two tail vertebrae and a large tibiae to megaraptors. Another large tibiae was described as a dromaeosaur (winged dinosaur) from the clade Uninagaria.
Carcharodontosaurs were large bipedal predators that occupied the top of the food chain at the same time as tyrannosaurs. In South America, they reached 13 meters in length, and in Australia, they were first discovered. This confirmed the hypothesis of a land bridge that connected the two continents across Antarctica in the Early Cretaceous Period.
The discovery of carcharodontosaurs showed that they could not only live in high-latitude climates and travel between different parts of Gondwana, but also survived there for at least 10 million years. Both described creatures are small - from two to four meters. Researchers did not rule out that they were very young individuals. The most anatomically similar to them predatory dinosaur - Siamraptor from Thailand (Laurasia, which was part of the supercontinent). Scientists have yet to find an explanation.
Before the discovery of carcharodontosaurs, megaraptors were considered the tallest land predators in Australia. Were they competitors? The question is open. The discovered megaraptors are much larger - over six meters, which is already unusual for polar Australia. One of them (specimen NMV P257415) is 5% larger than Australovenator, which was previously considered the largest Cretaceous predatory dinosaur. There are other finds of potentially larger individuals, but due to the inability to compare them with each other, the authors are confident that the Megaraptor they described is the largest known theropod from Australia. Moreover, it is the earliest known in the world.
New evidence suggests that the predatory dinosaur community of polar Australia was more stable and diverse than previously thought, while also hinting at the uniqueness of the local Cretaceous fossil record.
