Paleontologists recently uncovered a new species of dinosaur with a remarkable set of characteristics, offering new insights into the evolutionary relationship between theropod dinosaurs and modern birds. The species, named Shri rapax, was identified from an almost complete and articulated skeleton that dates back to the Late Cretaceous period, approximately 75 to 72 million years ago. The discovery, described in a study published in Historical Biology in July 2025, not only enriches our understanding of dinosaur morphology but also provides a deeper perspective on the predatory behaviors and ecological roles of these ancient creatures.
This particular species is part of the Dromaeosauridae family, a group of bird-like theropods that evolved during the Cretaceous period. The specimen of Shri rapax was found in the Djadokhta Formation in Mongolia, though its exact locality remains uncertain due to the specimen’s illicit origins and complicated history. Before being formally acquired by a French company, the dinosaur had been illegally poached and passed through private collections in Japan and England. Despite the murky provenance of the fossil, paleontologists were able to determine its species through detailed skeletal analysis and comparison with other dromaeosaurid fossils.
The Dromaeosauridae Family: A Close Relative of Birds
Dromaeosauridae is a clade of small- to medium-sized theropod dinosaurs that are known from several Cretaceous units across the world, including regions in North America, Asia, Europe, South America, and even Antarctica and Madagascar. As described by lead author Andrea Cau and colleagues, Shri rapax shares key features with other members of the dromaeosaurid group, positioning it firmly within the evolutionary lineage of birds. These dinosaurs are often noted for their bird-like characteristics, such as feathers and other integumentary structures, a trait that has sparked much interest in understanding the link between dinosaurs and modern avians.
The unique combination of skeletal features in Shri rapax, including its robust forelimbs and specialized hands, offers valuable clues about the role of these theropods in their ecosystems. These adaptations are believed to be linked to its predatory behavior, which could have involved tackling larger prey than that typically hunted by other members of the Velociraptor genus. In fact, it is theorized that the evolution of these robust hand features was influenced by interactions with other dinosaurs, particularly ceratopsians, which were larger and more robust herbivores that could actively defend themselves against predators.
A Close Link to Feathered Dinosaurs
A striking feature of the dromaeosaurids, including Shri rapax, is the presence of feather-like integumentary structures, a defining characteristic that strengthens the connection between theropods and modern birds. Shri rapax, though not possessing preserved feathers, belongs to a group of dinosaurs where feather-like structures have been identified in exceptional fossil specimens. As noted in the article, “Feather-like integumentary structures, true pennaceous feathers and remnants of the digestive tract are found in exceptionally-preserved dromaeosaurids from the Lower Cretaceous Jehol Biota of north-eastern China (e.g. Daurlong wangi, Sinornithosaurus millenii, Microraptor zhaoianus).” These preserved remnants highlight the importance of understanding the evolution of feathers, not only for thermoregulation and display but also as crucial evidence in the study of bird-dinosaur evolutionary relationships.
Along with the troodontids, dromaeosaurids are universally considered the closest relatives of birds among dinosaurs. This connection is particularly important in understanding the origin of flight and other avian traits. For Shri rapax, the robust features of its hands suggest a specialized predatory strategy, while the possibility of feather-like structures adds to the fascinating complexity of its appearance and behavior.
The Predatory Behavior and Adaptations of Shri rapax
One of the most striking features of Shri rapax is the exceptional robustness of its hands, particularly the thumb (pollex). As the researchers point out, “The most unusual feature of Shri rapax is the exceptional robustness of the hand.” The hands of Shri rapax are approximately 150% more robust transversely than those of other dromaeosaurids from the Djadokhta Formation, making them proportionally stouter than any other known member of the family. This structural adaptation is believed to be related to the animal’s interaction with ceratopsians, which were large, herbivorous dinosaurs known for their defensive behaviors. The enhanced hand strength likely allowed Shri rapax to handle larger prey more effectively than its close relatives, such as Velociraptor mongoliensis.
The robust hands of Shri rapax may also have been a response to the ceratopsians’ active antipredatory behaviors. “We suggest that frequent interactions with the ceratopsians, combined with active antipredatory behavior by the latter, could had promoted the evolution of more robust forearms and stockier hands among some Djadokhtan velociraptorines,” the researchers explained. This adaptation may have made Shri rapax better equipped to overpower its prey, a key feature that sets it apart from other velociraptorines.
Additionally, the study suggests that Shri rapax may have shared predatory behaviors with its close relative Velociraptor mongoliensis. According to the researchers, “If we assume that Shri rapax shared the predatory behavior of its close relative Velociraptor mongoliensis, the more robust proportions of its hands imply that it was better adapted to target larger and more robust prey than those usually preyed on by Velociraptor.” This implies that Shri rapax was not just a small predator but likely played a more significant role in its ecological niche, targeting larger and tougher prey.
The Poaching and Fossil Trade
An important aspect of this discovery is the complicated history of the Shri rapax fossil. The specimen was initially illegally poached before 2010 and subsequently passed through private collections in Japan and England before being acquired by the French company Eldonia. As noted in the study, “This dromaeosaurid specimen was illegally poached before 2010, then retained in private collections in Japan and England before being acquired by the French company Eldonia.” This highlights the ongoing issue of fossil poaching and the black market for rare specimens, which can often result in the loss of important scientific data.
The provenance of Shri rapax remains uncertain, with the researchers tentatively suggesting that it may have come from Ukhaa Tolgod in Mongolia, based on the available documentation. However, “The exact locality of the specimen is unknown.” This uncertainty complicates the scientific understanding of the specimen’s original context, making it difficult to fully assess its ecological role during the Cretaceous period. Nevertheless, the detailed study of the fossil has provided invaluable information about the species’ anatomy and its relationship with other theropod dinosaurs.
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