A Bird Without a Tail: Study Finds 121-Million-Year-Old Longipteryx Likely Had No Tail Feathers

Growing up, we lived near a bird park. It contains over a hundred different bird species. Among them are parrots, flamingos, toucans, ducks, ibises, owls, and even a cassowary. I remember going there quite often with my dad, Opa and even my uncle. Each time, we had a fun story to tell. Parrots that tried to nibble my dad’s toes, budgies that thought my Opa’s hair was the perfect nesting material, a parrot fascinated by the echo sound when it knocked on a hollow rock, and my young self learning during a bird show that owls are actually rather stupid (thank you to the owl who had been part of that show for over 10 years and still could not always remember his routine, fly from perch A to perch B).

Although the birds came in every shape and size imaginable, from every continent on Earth, they all had one thing in common. To some degree or another, they had tail feathers (rectrices).

For many Early Cretaceous birds, this is much the same. Among these Cretaceous enantiornithine birds is Longipteryx chaoyangensis. Despite numerous Longipteryx fossils in various collections, their soft-tissue traces, such as feathers, are often poorly preserved. A new study by Alexander Clark and his colleagues examined two new fossils, both of which preserve the body and wing plumage. They reveal that Longipteryx probably flew like no other bird alive today, and it may have lacked something we often take for granted in birds: tail feathers.

Meet Longipteryx

Longipteryx belonged to the group of birds known as Enantiornithes. During the Mesozoic, they were the most diverse group of birds alive. Much of what we know about them comes from fossil remains in the Jehol Biota of northeastern China, dated to the Lower Cretaceous, around 121–131 million years ago.

The lake deposits here, formed amid volcanic activity, are famous for preserving soft tissues like skin, muscle, and feather traces, revealing how these ancient birds grew and even what they ate.

Feathers are the most commonly preserved of these soft tissues. Despite body and tail feathers (mostly ornamental) often being found, wing flight feathers (remiges) are surprisingly rare.

Longipteryx is one of the few Jehol birds known from many specimens, easily recognised by its long snout (rostrum) and large teeth at the tip of its jaw. Researchers have long studied various aspects of its life, including its teeth, jaw-joint morphology, and diet. In fact, it is thought that despite their almost kingfisher-like appearance, they may have eaten fruits. The teeth were perhaps used more for aggression and display.

What hasn’t been studied in detail is their plumage. This is simply because earlier specimens lacked feathers preserved well enough for detailed study. Then STM 8-28 and STM 8-132 came along.

Feathered Fossils

The two Longipteryx specimens were found in Jianchang County, in Liaoning Province, by an amateur fossil collector. They had been donated to the Shandong Tianyu Museum of Nature in Pingyi, China.

Based on their long snouts, teeth on the tip of the jaw, as well as several other features, the researchers identified them as Longipteryx.

The first fossil, specimen STM 8-28, was preserved on a single slab seen from its underside (basically as if it was lying on a glass table and you looked at it from below). It probably did not weigh all too much, around 75–89 grams, making it about the size of modern Sturnella birds like meadowlarks.

Its bones were not in the best condition, but they preserved feather traces around almost the entire skeleton. The only unfeathered parts seemed to be the snout and feet. It had body feathers from its head, just in front of the eye socket, down its neck, shoulders, chest, and legs.

Its body feathers were dark and short (5–17 mm) and came with another layer of longer feathers (12–25 mm) just under the right wing, which were probably also part of the body feathers. The folded wings showed dark traces near the outer and middle parts.

Along the tail, though, something was missing.

Instead of long feathers, the tip of its tail was covered in short (5–8 mm) plumage just barely extending past the tail. There was no sign of any tail flight feathers.

On its own, this may not mean much. But then, looking at STM 8-132 revealed much the same. 8–12 mm long feathers on the head and neck and 15–18 mm around the hips and legs. Its wings had primary feathers around 85–120 mm long and secondaries from as short as 26 to as long as 72 mm. Its tail again preserved only short 4–8 mm long feathers, with no trace of tail flight feathers.

Unique Fliers

All in all, 19 Longipteryx fossils are known, more than any other enantiornithine. Many of them preserve soft tissue. Body feathers are rather common on these fossils; wing feathers are rare, so the two new fossils provide a rare glimpse into how these birds might have flown. Both fossils are almost exactly the same size (only about 2% different), yet their longest flight feathers differ by about 18%. This could be natural variation, differences between male and female specimens, or simply that one fossil is more complete than the other.

All fossil enantiornithines have folded wings, making it hard to see their shape and size.

These fossil wings are partly folded too, but still reveal wings with secondaries just over half the length of their primaries, much like the wings of modern warblers, finches, and thrushes, who use a flapping or flap-gliding flight rather than simply soaring or gliding alone. Similar to Orienantius but not so much like most other known enantiornithines.

But just looking at the wing feathers gives you only half the story. Its wing shape suggests a flapping flight, but its muscle attachment is long and weak, much more typical of modern gliders. Additionally, its half-moon-shaped shoulder joint (semi-lunate humeral head) would have limited how far it could move its wings up and down compared to modern birds, and its small breastbone keel points to a relatively small main flight muscle.

Together, this suggests that Longipteryx flew like no living bird does today. That also means comparing its flight to any living bird is not just difficult, but potentially misleading.

“Since enantiornithines represent a whole different lineage of bird flight, there’s no strong one-to-one analogue,” Clark said.

But among the most striking details is its lack of tail flight feathers. No Longipteryx specimen has them, making it unlike any living flying bird. It’s also kind of funny because every reconstruction I could find online includes some form of tail feather, usually shorter, like a kingfisher, but present nonetheless. Now those images may need updating, giving them fluffy hindquarters without the characteristic tail feathers we associate with birds.

Strictly speaking, birds don’t need tail feathers to fly. Some modern birds have been observed flying without them, usually after moulting or shock-moult (dropping feathers when grabbed by a predator) or after injury (e.g. cat attacks). 

“Enantiornithines, like Longipteryx, lacked a tail fan of feathers which in modern birds, helps them brake and steer (among other things),” Clark said. “So landing may have look[ed] different – perhaps their approach to a perch followed a different trajectory.”

Of course, some birds have tail feathers not for flying at all (e.g. the peacock, whose fancy train, made of tail coverts rather than true tail feathers, actually makes flying more difficult). Many enantiornithines also had ornamental tail feathers. Because only some individuals had them, people thought they might belong to males.

However, since none of the 19 Longipteryx specimens has any tail feathers, even the two specimens with well-preserved feathers overall, this suggests neither males nor females had tail feathers at all. This showcases just how differently these birds likely flew.

The authors caution that this is only a tiny fraction of the birds in the Enantiornithes group, so conclusions about the whole group may not hold.

I’ve been watching the birds in my garden more closely. Both for takeoff and landing, they fan their tail feathers. It helps them brake, steer and glide on the air currents. And yet Longipteryx seems to have been fine without them. I do wonder what its flight, takeoff, and landing would have looked like.

Penguins and ostriches have tail feathers; heck, even many bats have a little tail membrane (yes, I know it’s a mammal). So imagining a bird with no tail feathers at all is interesting, and it reminds us how much we still don’t know about these early birds, and how differently things evolved to fly over millions of years.

Why do you think Longipteryx lacked tail feathers, or do you have another theory as to why none of the Longipteryx fossils had tail feathers?

Let me know what you think, and if you'd like to support this blog and the person writing it, you can chip in once, monthly, or yearly. Only if you'd like to.

References

Clark, A., Wang, Y., Wang, X., Zhang, X., Wang, X., Zheng, X., … O’Connor, J. (2026). The plumage of Longipteryx (Aves: Enantiornithes). Journal of Paleontology, 1–9. doi:10.1017/jpa.2026.10282

O’Connor, J., Clark, A., Herrera, F., Yang, X., Wang, X., Zheng, X., ... & Zhou, Z. (2024). Direct evidence of frugivory in the Mesozoic bird Longipteryx contradicts morphological proxies for diet. Current Biology, 34(19), 4559-4566.