Novavis

MEANING: Strange bird

PERIOD: Early Cretaceous

CONTINENT: Asia

Novavis is an enantiornithean bird from the Early Cretaceous of what is now China. Enantiornithes are small theropods and represent early relatives of modern birds. They were feathered and capable of flight, but still had toothed beaks and clawed fingers. Novavis was approximately 15 cm in length, and is distinguished by its unusually small pubis.

Abstract from paper: We describe a partial skeleton of an enantiornithine from the Changma locality of the Lower Cretaceous Xiagou Formation in northwestern China. The specimen is tentatively interpreted as a gastric pellet. The specimen preserves an unusually short pubis that is subequal in length to the ischium, an autapomorphy among enantiornithines, justifying erection of a new taxon, Novavis pubisculata nov. gen., nov. sp. The abbreviated length of the pubis suggests that the abdominal cavity in this species was proportionately shorter than in all other known enantiornithines. Although several muscles attach to the pubis, the mm. pubocaudalis internus and externus were probably the most functionally impacted by the increased distance between the pubes and caudal vertebrae and subsequent elongation of these muscles. In crown avians this would result in a decrease in the contraction speed of these muscles, which play a role in tail fanning and are thus important for flight during take-off and landing. Although the underlying function of the short pubis and changes in the size of the abdominal cavity are unknown, the widespread absence of aerodynamic tail musculature and plumage in enantiornithines may have relaxed pressures constraining the length of these muscles, such that elongation of these muscles through a shortened pubis was not detrimental to the aerodynamic abilities of these birds.

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Novavis is from the Early Cretaceous. The Cretaceous is the third and final geological period of the Mesozoic Era, with the Early Cretaceous making up roughly the first half, lasting from about 143 to 100 million years ago. The poles were ice-free, due to the relatively warm climate, and forests extended into high latitudes. The continued breakup of the continents created new coastlines and isolated landmasses, influencing the evolution of distinct dinosaur faunas.

It was a time of transition, as many groups of animals and plants began to take on more modern forms while others declined or disappeared. Pterosaurs continued to thrive, though early birds were becoming more diverse and widespread. Mammals remained small but adapted to a variety of ecological niches. In the oceans, ichthyosaurs and plesiosaurs were common, and early mosasaurs began to appear.

Dinosaurs remained the dominant land animals, with groups like iguanodontians, spinosaurids, and carcharodontosaurids rising to prominence. While sauropods declined in some regions, they remained abundant in the Southern Hemisphere. The first true ceratopsians appeared, and ankylosaurs replaced stegosaurs in their niche. Dromaeosaurs and other small theropods diversified. During this time, the first flowering plants evolved, gradually changing global ecosystems by providing new food sources for herbivores.

Novavis is an enantiornithean avialan. Enantiornithes is a diverse group of early birds, also known as the "opposite birds." They were the most successful group of Mesozoic birds, spanning the Cretaceous and found on nearly every continent. They ranged from sparrow-sized to birds with wingspans of a meter or more. The group's name refers to a distinctive detail of the shoulder: the joint between the scapula and coracoid is reversed compared to modern birds. Like other early birds, most retained clawed hands, conical teeth, and a reduced but often still visible bony tail base, though many also developed a pygostyle for supporting tail feathers.

Enantiornithes were capable fliers and occupied a wide range of ecological roles. Some were tree-dwelling insectivores, others fed on seeds, fish, or possibly sap, and their beaks and toe proportions vary widely, pointing to considerable ecological diversity. Exceptional fossils preserve elaborate plumage, including ribbon-like tail feathers in some males, suggesting sexual display was important. Many hatchlings appear to have been precocial, able to fly soon after hatching, a strategy quite different from most modern birds. Enantiornithes were wiped out at the end of the Cretaceous, leaving Neornithes, the ancestors of all living birds, as the only surviving avian lineage.