Shri rapax

Shri rapax is a small-bodied dromaeosaurid theropod from the Upper Cretaceous Djadokhta Formation of Mongolia. Described in 2025 by Moutrille and colleagues, it represents a new genus and species of highly derived eudromaeosaur and is one of the best-preserved dromaeosaurid specimens from the Campanian-aged sediments of the Gobi Desert.

The generic name Shri is a Sanskrit honorific meaning “radiance” or “glory,” while the species name rapax (“grasping” or “predatory” in Latin) refers to its inferred raptorial behavior.

The holotype includes a nearly complete and well-articulated skeleton, providing valuable insight into the anatomy and function of dromaeosaurid limbs, particularly their grasping capabilities. Shri rapax is notable for possessing a robust forelimb with highly recurved manual claws and exceptional preservation of soft tissues.

Geographic Location

Fossil locality: Attributed to Ukhaa Tolgod, Ömnögovi Province, southern Mongolia

Physical Characteristics

The holotype specimen of Shri rapax (MPC-D 102/117) includes a nearly complete, three-dimensionally preserved skeleton, missing only parts of the skull and distal tail. Key preserved elements include:

• Nearly complete pectoral girdle (scapulocoracoid)

• Complete forelimbs, including articulated manus

• Partial axial skeleton, with dorsal, sacral, and caudal vertebrae

• Pelvis, including ilium, pubis, and ischium

• Complete hind limbs and pes, including a large pedal digit II ungual (“killing claw”)

Anatomically, Shri rapax displays classic eudromaeosaurid features:

• A hypertrophied sickle-shaped claw on the second pedal digit

• Elongate, recurved manual unguals

• Enlarged deltopectoral crest on the humerus

• Laterally facing glenoid fossa, allowing powerful forelimb abduction

• Pneumatic cranial bones and axial elements

The overall proportions suggest a gracile yet muscular predator built for agility and prey capture. The manus exhibits particularly strong grasping adaptations, leading the authors to interpret Shri as highly proficient at seizing and manipulating prey with its forelimbs.

Size Estimation

No femur or complete axial length is preserved; however, the authors compare Shri rapax directly to Deinonychus antirrhopus, a well-known dromaeosaurid. The humerus of Shri measures approximately 64% the length of that in Deinonychus.

Given that Deinonychus averaged 3.2 meters (10.5 feet) in length and ~80 kg (176 lbs) in mass:

• Length: 3.2 m × 0.64 ≈ 2.05 meters (6.7 feet)

• Mass: 80 kg × (0.64)³ ≈ 21 kilograms (46 lbs)

These proportions are supported by detailed osteological comparisons in the original description and align with similarly sized dromaeosaurids like Velociraptor mongoliensis.

Diet and Feeding Habits

Shri rapax was a carnivore, likely preying on small vertebrates, such as mammals, lizards, and possibly hatchling dinosaurs. Its anatomy supports a raptorial mode of predation:

• Grasping forelimbs with recurved claws

• Robust arms and deltopectoral crest for powerful flexion

• A highly recurved “killing claw” on digit II of the foot

The forelimbs appear to have played an unusually significant role in prey capture. The authors describe Shri as having a high degree of manual grasping ability, perhaps using both hands and feet in a coordinated strike-and-subdue strategy.

Habitat and Distribution

Shri rapax lived during the Campanian stage of the Late Cretaceous (~75–71 Ma), in what is now the Gobi Desert region of southern Mongolia. The Djadokhta Formation is well-known for its semi-arid, aeolian (wind-blown) depositional environment composed of reddish cross-bedded sandstones and siltstones.

This ecosystem was home to a diverse vertebrate fauna, including:

• Dromaeosaurids: Velociraptor mongoliensis, Tsaagan mangas

• Oviraptorosaurs: Citipati, Khaan

• Protoceratopsids: Protoceratops andrewsi

• Small mammals, lizards, and birds

• Occasional ankylosaurs and alvarezsaurs

Shri rapax likely occupied the niche of a small-to-mid-sized predator, competing with or replacing other similarly sized maniraptorans in its local environment.

Behavior and Social Structure

Although direct behavioral evidence is lacking, Shri’s morphology supports interpretations of a solitary, fast, and agile predator. The powerful forelimbs, recurved unguals, and lateral shoulder joint motion suggest active prey capture. Its relatively small size suggests it likely preyed upon smaller vertebrates and may have used a combination of ambush and short-burst pursuit strategies.

There is no evidence for pack hunting, but gregarious behavior cannot be ruled out. The well-developed forelimb musculature and flexible manus imply complex prey-handling capabilities, potentially unique among its relatives.

Discovery and Research

The specimen MPC-D 102/117 was discovered in Mongolia and has been housed in the collection of the Institute of Paleontology and Geology, Mongolian Academy of Sciences. Although the exact locality was undocumented, the original collector and stratigraphic evidence strongly support provenance from the Ukhaa Tolgod beds of the Djadokhta Formation.

Described in 2025 by Moutrille et al., Shri rapax is distinguished by a combination of features in the scapulocoracoid, humerus, and manual unguals. Phylogenetic analysis places it within Dromaeosauridae, as a derived member of Eudromaeosauria, closely related to Velociraptor and Tsaagan.

Significance and Notable Facts

• One of the most complete and three-dimensionally preserved dromaeosaurids from the Djadokhta Formation

• Displays exceptional adaptations for grasping prey with the forelimbs

• First dromaeosaurid from Mongolia to show such extensive preservation of the pectoral girdle and forelimb anatomy

• Helps clarify dromaeosaurid diversity and functional morphology in Late Cretaceous Asia

• Likely lived sympatrically with Velociraptor, but may have occupied a slightly different predatory niche

Conclusion

Shri rapax is a small but anatomically important dromaeosaurid that adds new perspective to the Late Cretaceous ecosystems of Mongolia. Its excellent preservation and unique grasping adaptations highlight the diversity of predatory strategies within Dromaeosauridae. As a likely specialist in active prey capture, Shri may have been one of the most manual-dominant raptorial theropods known to date.