Plumadraco

MEANING: Feather dragon

PERIOD: Early Cretaceous

CONTINENT: Asia

Plumadraco is an enantiornithean bird that lived during the Early Cretaceous period in what is now China. The genus is known from a complete skeleton preserving soft tissues, including a pair of elongated tail feathers.

Abstract from paper: Bird diversity is reflected in the abundance and variety of extraordinary plumages. Some of these include elongate, ornamental tail feathers that are typically attributed to either intraspecific communication in monomorphic species or sexual selection in sexually-dimorphic ones. Enantiornithines (Aves: Ornithothoraces) were the most diverse group of birds during the Cretaceous. Importantly, some enantiornithine fossils preserve soft tissues, most often in the form of feathers surrounding the body. Unlike any living bird, many enantiornithine specimens lack tail feathers (rectrices) all together, with the tail region consisting entirely of contour feathers. However, when present, enantiornithine rectrices typically consist of a pair of elongate, ornamental feathers with unusually wide rachises, referred to as rachis-dominated feathers. Here we describe Plumadraco bankoorum gen. et sp. nov., a new bohaiornithid enantiornithine with a pair of exceptionally long rectrices. These tail feathers measure twice the individual’s body length, ending in proportionally small pennaceous rackets, thus adding to the growing diversity of these unusual feathers. The fine preservation of these tail feathers, in comparison to other enantiornithine rectrices, reveals previously unrecognized structural variation that hints at their potential function in courtship displays. Although ornamental feathers in enantiornithines are widely considered sexually dimorphic, determining the selection pressures that shaped them is difficult due primarily to limited soft tissue data. Enantiornithine rectrices are likely the result of an interplay between both sexual and naturally selective pressures, similar to the processes which produce analogous structures in birds today.

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Plumadraco 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.

Plumadraco 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.