Manipulonyx reshetovi
- 演化之聲
- Mar 20
- 2 min read
Updated: Apr 9
Age
Cretaceous（Maastrichtian）
70 Ma
Taxonomy
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Saurischia
Family: Alvarezsauridae
Genus: Manipulonyx
Species: Manipulonyx reshetovi
Morphological description
Manipulonyx reshetovi is a small-sized theropod dinosaur, with an estimated body length of less than one meter. Its hind limbs are elongated and slender, whereas the forelimbs are extremely reduced. Despite their short length, the forelimbs possess a robust humerus and a strongly developed second manual digit.
The radius and ulna of the forelimb are fused, and the three metacarpals are also completely fused into a single unit. These elements are connected to three proximal carpal bones, forming a large and structurally complex wrist apparatus.
The manus consists of three digits, but two of them are highly reduced. Only the second digit is hypertrophied. Each digit bears a claw, with the claw of the second digit being exceptionally large and strongly curved. Around the metacarpus, three small bony spikes are present, oriented anteriorly, posteriorly, and medially. These spikes were likely covered by keratinous sheaths in life.
Etymology
The generic name Manipulonyx is derived from the Latin manipulare, meaning "to handle" or "to manipulate", combined with the Greek onyx, meaning "claw".
The species name honors the fossil discoverer, V. Y. Reshetov.
Biological description
The fossil material of Manipulonyx reshetovi was discovered in 1979 from the Upper Cretaceous Nemegt Formation in Mongolia. It belongs to Parvicursorinae within Alvarezsauridae. The holotype specimen (PIN 3142/364) preserves 13 vertebrae, most of the forelimb, and partial pelvic and hind limb elements. Although the skeleton is incomplete, the forelimb is the most completely preserved among known parvicursorines.
Previous interpretations of alvarezsaurid dinosaurs suggested that they underwent rapid miniaturization and possessed specialized forelimbs adapted for digging, likely used to break into insect nests. Based on this view, derived forms were thought to be insectivorous.
However, the morphology of Manipulonyx challenges this interpretation. Its forelimbs are extremely short and would have been ineffective for reaching the ground or excavating nests. This has led researchers to propose an alternative hypothesis: that parvicursorines were egg-eaters.
The forelimb structure of Manipulonyx appears well suited for grasping eggs. The bony spikes on the metacarpus, together with the reduced lateral digits, could have helped stabilize the forelimb against the smooth surface of an egg. Once secured, the enlarged second digit—with its powerful claw—could puncture the eggshell.
It is hypothesized that these small dinosaurs may have entered the nests of other dinosaurs, possibly under low-light conditions, seized a single egg, and then transported it to a safer location before consumption.
（Author: Bai Leng）
Reference
Averianov, A. O., Lopatin, A. V., Atuchin, A. A. (2025). Forelimb structure and function in a new Late Cretaceous parvicursorine theropod dinosaur from Mongolia. Proceedings of the Zoological Institute of the Russian Academy of Sciences.
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