Manipulonyx

MEANING: Manipulating claw

PERIOD: Late Cretaceous

CONTINENT: Asia

Manipulonyx is an alvarezsaurid theropod whose discovery revealed this family may be adapted toward an egg-based diet. Smaller claws on the hands prove mechanically capable of holding an egg in place, while a larger claw would puncture the shell. This hypothesis questions the previously standing idea that alvarezsaurs were specially adapted to insectivory.

Abstract from paper: A new parvicursorine theropod, Manipulonyx reshetovi, gen. et sp. nov., is based on a fragmentary skeleton from the Upper Cretaceous (Maastrichtian) Nemegt Formation at Khermeen Tsav, Gobi Desert, Mongolia. The new taxon differs from other parvicursorines in a unique combination of characters. The skeleton of Manipulonyx preserves an articulated and complete forelimb, including rudimentary side fingers, and a complete series of proximal carpals (ulnare, intermedium, and radiale). The proximal carpals were previously unknown for Parvicursorinae. This specimen also shows for the first time the presence of additional dermal ossifications in the carpus, three spikes articulated with (medial and lateral spikes) or attached to (palmar spike) the carpometacarpus. We hypothesize that parvicursorines were egg-eating animals and they used these spikes (covered by a keratinous sheath), as well as rudimentary side fingers, to fix the forelimb on the round and elusive egg surface. After such fixation, the egg-shell was punctured by the hypertrophied manual claw. This interpretation is supported by a number of morphofunctional traits of the parvicursorine forelimb discussed in the paper, including the hypertrophied deltopectoral crest of the humerus, keeled sternum, enlarged ectepicondyle of humerus, hypertrophied olecranon of ulna, and lack of the flexor tubercle on the main manual ungual phalanx.

Manipulonyx is from the Late Cretaceous. The Cretaceous is the third and final geological period of the Mesozoic Era, with the Late Cretaceous making up roughly the second half of it, lasting from about 100 to 66 million years ago. It was a time of significant evolutionary change, with dinosaurs reaching their greatest diversity before the mass extinction at the end of the Cretaceous.

The Cretaceous was a period with a relatively warm climate, though the Late Cretaceous experienced a global cooling trend, caused by falling levels of carbon dioxide in the atmosphere. The continents were nearing their present positions, but high sea levels flooded low-lying regions, turning Europe into an archipelago, and forming the Western Interior Seaway in North America. These seas were home to a variety of marine reptiles, including mosasaurs and plesiosaurs, while pterosaurs and birds shared the skies.

On land, dinosaurs continued to thrive and diversify during the Late Cretaceous, producing many of the most well-known goups, including tyrannosaurs, hadrosaurs, and pachycephalosaurs. Established Cretaceous dinosaur clades like the ceratopsians, ankylosaurs, and dromaeosaurs continued to flourish. Sauropod species consisted almost exclusively of titanosaurs, which seemed to be confined to the Southern Hemisphere for much of the Late Cretaceous. Flowering plants and grasses diversified and spread, becoming the dominant flora similar to what we see today.

The Cretaceous (along with the Mesozoic) ended with the Cretaceous-Paleogene (K-Pg) extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. This event, likely triggered by an asteroid impact, is marked by the abrupt K-Pg boundary, a distinct geologic layer separating the Mesozoic and Cenozoic Eras. In its aftermath, mammals and avian dinosaurs rapidly diversified, becoming the dominant land animals of the Cenozoic Era.

Manipulonyx is an alvarezsaur. Alvarezsaurs are a group of small, bird-like theropod dinosaurs that originated in Asia in the Jurassic, and became more prominent in the Cretaceous, spreading to the Americas and Europe. Their exact placement within the theropod family tree has been debated, but alvarezsaurs are generally considered to be highly specialized maniraptorans.

While basal alvarezsauroids show less extreme adaptations and more typical theropod anatomy, the derived alvarezsaurids proved to be highly specialized. They were small, lightly built, and fast-running animals, typically under 2 meters in length. Their skeletons reveal long hindlimbs adapted for speed, bird-like skulls with slender jaws, and a keeled sternum for strong muscle attachment - traits that suggest a very active lifestyle. One of their most distinctive features is their forelimbs - extremely short but robust, with a single dominant claw and reduced digits. Their exact diet remains uncertain, but many paleontologists believe they were insectivores, using their strong arms to break into tough nests like those of termites.

Despite their unusual build, alvarezsaurs represent a successful and diverse branch of maniraptoran evolution, highlighting the varied ecological roles small theropods played in Mesozoic ecosystems.