Fujianvenator

MEANING: Fujian hunter

PERIOD: Late Jurassic

CONTINENT: Asia

Fujianvenator had long legs, suggesting it may have been a strong runner, and possibly had a terrestrial or wading lifestyle. Fujianvenator was a small dinosaur, weighing about 640 g. As an avialan, it was almost certainly covered in feathers, though it does not seem likely to have been capable of flight.

Abstract from paper: Birds are descended from non-avialan theropod dinosaurs of the Late Jurassic period, but the earliest phase of this evolutionary process remains unclear owing to the exceedingly sparse and spatio-temporally restricted fossil record1,2,3,4,5. Information about the early-diverging species along the avialan line is crucial to understand the evolution of the characteristic bird bauplan, and to reconcile phylogenetic controversies over the origin of birds3,4. Here we describe one of the stratigraphically youngest and geographically southernmost Jurassic avialans, Fujianvenator prodigiosus gen. et sp. nov., from the Tithonian age of China. This specimen exhibits an unusual set of morphological features that are shared with other stem avialans, troodontids and dromaeosaurids, showing the effects of evolutionary mosaicism in deep avialan phylogeny. F. prodigiosus is distinct from all other Mesozoic avialan and non-avialan theropods in having a particularly elongated hindlimb, suggestive of a terrestrial or wading lifestyle—in contrast with other early avialans, which exhibit morphological adaptations to arboreal or aerial environments. During our fieldwork in Zhenghe where F. prodigiosus was found, we discovered a diverse assemblage of vertebrates dominated by aquatic and semi-aquatic species, including teleosts, testudines and choristoderes. Using in situ radioisotopic dating and stratigraphic surveys, we were able to date the fossil-containing horizons in this locality—which we name the Zhenghe Fauna—to 148–150 million years ago. The diversity of the Zhenghe Fauna and its precise chronological framework will provide key insights into terrestrial ecosystems of the Late Jurassic.

Fujianvenator 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.

Fujianvenator is a paravian. The evolution of birds began in the Jurassic Period, with the earliest birds derived from a clade of theropod dinosaurs named Paraves. 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 paravians 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. Paravians 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 paravian 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.