MEANING: Desert bird
PERIOD: Late Cretaceous
CONTINENT: Asia
Shuvuuia is a small, bird-like theropod in the family Alvarezsauridae. It is one of the smallest known non-avian dinosaurs, at just 1 m in length and weighing about 3.5 kg. Shuvuuia had a fragile skull, long legs for running, and short powerful arms with a large claw on each hand. Like all alvarezsaurids, it is thought that the small but robust arms were adapted for digging and tearing. This, along with the long tube-like snout suggest that Shuvuuia fed on colonial insects like termites. Shuvuuia's skull is unique in its ability to flex the upper jaw independently from the rest of the skull.
Shuvuuia is from the Cretaceous. The Cretaceous is a geological period that lasted from about 145 to 66 million years ago. It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, "chalk", which is abundant in the latter half of the period.
The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct flora and fauna, while dinosaurs continued to dominate on land. The world was ice free, and forests extended to the poles. During this time, new groups of mammals and birds appeared. During the Early Cretaceous, flowering plants appeared and began to rapidly diversify, becoming the dominant group of plants across the Earth by the end of the Cretaceous, coincident with the decline and extinction of previously widespread gymnosperm groups.
The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary (K–Pg boundary), a geologic signature associated with the mass extinction that lies between the Mesozoic and Cenozoic Eras.
Shuvuuia is an alvarezsaur. Alvarezsauria is a group of small theropod dinosaurs that originated in Asia in the Jurassic, and became more prominent in the Cretaceous, spreading to the Americas and Europe. The size of the derived members range between 0.5 and 2 m, making them some of the smallest known non-avian dinosaurs. Haplocheirus was the largest and most primitive member of the Alvarezsauroidea, suggesting a pattern of miniaturization as time went on.
Alvarezsaurs are known for their long legs, suggesting they were great runners, and their extremely short, yet robust, arms. Derived members are characterized by digit reduction. Over the course of their evolution, one finger on each hand, along with its corresponding claw, grew larger, while the others became reduced. Eventually, the most derived species were left a single large claw tipping each short arm, with the remaining fingers being so small as to seem vestigial.
These changes have been interpreted as adaptations for digging. One possible interpretation suggests that alvarezsauroids fed on insects, using their claws to dig under tree bark. This is consistent with their long snout and small teeth. Another interpretation suggests that they used their claws to break into ant and termite colonies.