| Baminornis | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Clade: | Avialae |
| Genus: | †Baminornis Chen et al.,2025 |
| Species: | †B. zhenghensis |
| Binomial name | |
| †Baminornis zhenghensis Chen et al., 2025 | |
Baminornis (meaning "Fujian Province bird") is anextinct genus ofbasalavialans from theLate Jurassic (Tithonian age)Nanyuan Formation of China. The genus contains asingle species,B. zhenghensis, known from a partial skeleton.Baminornis is the oldest known avialan to bear a fusedpygostyle.[1]
TheBaminornisholotype specimen,IVPP V33259, was discovered in outcrops of theNanyuan Formation ('layer 2') nearYangyuan Village ofZhenghe County inFujian Province, China. The specimen is incomplete and partially articulated, comprising bones of the left forelimb, and hindlimb, partial leftpectoral andpelvic girdles,dorsal andcaudal vertebrae, thepygostyle, and severalribs andgastralia.[1]
In 2025, Chen et al.describedBaminornis zhenghensis as a new genus and species of early birds based on these fossil remains. Thegeneric name,Baminornis, combinesBamin—theMandarin word for Fujian Province—with theGreek wordornis, meaning "bird". Thespecific name,zhenghensis, references the discovery of the fossil in Zhenghe County.[1]
Baminornis is a small avialan. Its body mass is estimated at 130–300 grams (0.29–0.66 lb) based on the circumference of the femur shaft. Its robust pygostyle comprises five fused vertebrae, curving upward. Similar to other Jurassic avialans, the ilium is about half the length of the femur. As such, it is proportionaltely shorter than in more derived taxa. The shoulder girdle, including thescapula andcoracoid are unfused, more similar to crownward taxa. This may imply improved flight abilities compared to the similarly-agedArchaeopteryx.[1][2]
In theirphylogenetic analyses, Chen et al. (2025) recoveredBaminornis as abasally-branching member of theAvialae, diverging afterArchaeopteryx but beforeJeholornis. The researchers noted that the presence of a pygostyle inBaminornis could warrant a redefinition of the short-tailed bird cladePygostylia. However,Jeholornis does not have a pygostyle; under this scenario, it re-evolved its long tail from short-tailed ancestors. Alternatively, this pygostyle structure may have evolved inBaminornis independently of the later-diverging taxa. Regardless,Baminornis indicates that some of the earliest avialans possessed a pygostyle 20 million years earlier than previously recognized. This highlights the complexity of early bird evolution and the irregular acquisition of seeminglyderived traits.[1]
The results of the analyses of Chen et al. are displayed in thecladogram below, with the two alternate placements of Pygostylia noted:[1]
Baminornis is known from the Nanyuan Formation, which dates to around 150 million years ago, during the Tithonian age of the lateJurassic period. The outcrops of this formation have been interpreted as representing a primarilyswamp-likedepositional environment. Most of the vertebrate fossils from the formation came from aquatic and semiaquatic animals, including indeterminate unnamedteleost fish,turtles, andchoristoderes. However, some avialan fossils have also been discovered, including theanchiornithidFujianvenator and some indeterminate birds, including a possibleornithuromorph known from afurcula. Thislagerstätte is referred to as the Zhenghe Fauna.[1][3]
.jpg)
