Baminornis

MEANING: Fujian Province bird

PERIOD: Late Jurassic

CONTINENT: Asia

Baminornis is the oldest known bird with a fused pygostyle, a skeletal feature that implies tail feathers. Its discovery pushed back current understanding of bird evolution and global distribution by 20 million years. Baminornis was about 15 cm in length, had many features in common with modern birds, including the capability for powered flight.

Abstract from paper: Recent macroevolutionary studies predict a diversification of early birds during the Jurassic period, but the unquestionable Jurassic bird fossil record is limited to Archaeopteryx, which has also been referred to deinonychosaurian dinosaurs by some analyses. Although they have feathered wings, the known Jurassic birds are more similar to non-avialan theropods in having the ancestral long reptilian tail. This is in stark contrast to most Cretaceous and crownward taxa, which have a short tail that terminates in a compound bone called the pygostyle. Here we report on the oldest short-tailed avialan, Baminornis zhenghensis gen. et sp. nov., from the recently discovered Late Jurassic Zhenghe Fauna, which fills a noticeable spatio-temporal gap in the earliest branching avialan fossil record. B. zhenghensis exhibits a unique combination of derived ornithothoracine-like pectoral and pelvic girdles and plesiomorphic non-avialan maniraptoran hand, demonstrating mosaic evolution along stem avialan line. An avialan furcula collected from the same locality is referrable to ornithuromorphs on the basis of our morphometric and phylogenetic analyses. These newly discovered fossils demonstrate the early appearance of highly derived bird features, and together with an anchiornithine fossil from the same locality, they suggest an earlier origin of birds and a radiation of early birds in the Jurassic.

Baminornis is from the Late Jurassic. The Late Jurassic was a dynamic period, spanning from about 162 to 143 million years ago. The continents were continuing to drift apart, and the supercontinent Pangaea had fully split into Laurasia in the north and Gondwana in the south. This continental rearrangement led to the formation of large inland seas and shallow coastlines that fostered diverse ecosystems. The climate during the Late Jurassic was warm and humid, with lush forests of conifers and ferns that stretched across much of the continents, creating a rich ecosystem where dinosaurs flourished the dominant land animals.

Dinosaurs continued to diversify through the Late Jurassic, with some of the most famous species evolving in this time. Many well-known sauropods, such as Brachiosaurus and Apatosaurus roamed the land, exhibiting niche partitioning with their selectively distinct neck positions. Alongside them, stegosaurs became widespread, their plates and spikes making them one of the era's most recognizable groups. Theropods like Allosaurus and Ceratosaurus were the apex predators, evolving large, powerful bodies and sharp teeth that allowed them to hunt the gigantic herbivores. The early evolution of birds was taking place, setting the stage for the numerous species that would fill the skies in the eras to come.

Unlike the dramatic mass extinctions that marked the beginning and end of the Mesozoic, the Jurassic Period ended without a sharp boundary. As the continents continued to drift, ecosystems gradually transformed into unique habitats that supported the more specialized dinosaur species of the Cretaceous.

Baminornis is an avialan. The evolution of birds began in the Jurassic Period, with the earliest birds derived from a clade of theropod dinosaurs named Avialae. The Archaeopteryx has famously been known as the first example of a bird for over a century, and this concept has been fine-tuned as better understanding of evolution has developed in recent decades.

Like other theropods, all avialans are bipedal, walking on their two hind legs. Most of the earliest groups were carnivorous, though some smaller species are known to have been omnivores. Avialans generally have long, winged forelimbs, though these have become smaller in many flightless species. The wings usually bore three large, flexible, clawed fingers in early forms. Over time, the fingers became fused and stiffened in some lineages, and the claws reduced or lost. An increasingly asymmetric wrist joint allowed the forelimbs to elongate and an elaboration of their plumage eventually allowed the evolution of flapping flight possible.

Birds, as we know them today, are the only surviving lineage of dinosaurs. As these early avialan dinosaurs continued to evolve through the Late Jurassic and into the Cretaceous, they developed lighter skeletons, improved respiratory systems, and more specialized feathers, all of which contributed to better aerial capabilities. The classic features we associate with modern birds - beaks, powerful flight muscles, and highly refined feathers - gradually emerged over millions of years. By the end of the Mesozoic, true birds had diversified into a wide range of ecological roles, from fish hunters to seed eaters. While most dinosaur lineages vanished in the Cretaceous-Paleogene extinction event, this small, feathered group managed to survive and radiate into one of the most successful vertebrate clades alive today.