Fossil Localities & Sites

DIRECT What the material preserves

Resin traps an object and holds its shape. That's why Burmese amber has produced feather structures and small bird parts at a level of detail the Jehol shales can't reach — including a reported three-dimensional Stage IIIb down feather, a barbs-plus-barbules form with no rachis, which sits exactly where the Prum & Brush developmental model predicts an intermediate should be. That report (Roy et al. 2020) is a preprint, and we treat it as a preprint.

The scientific value is not in dispute here. What follows is about where the specimens come from, not whether they're informative.

CONTESTED Why provenance is the problem

The amber mines sit in Kachin State, in a region of active armed conflict, and the trade in this amber is linked to that conflict and to human-rights abuses. Specimens typically move from the mines through commercial dealers and gem markets before a researcher ever sees them, which means the buying, describing, and publishing of a fossil can put money and legitimacy back into that chain.

The legal position doesn't settle it either. Myanmar's export law is a grey zone for this material: depending on which statute applies, the same piece of amber is a gemstone or a fossil, and those categories carry different rules. A specimen can therefore have left the country lawfully under one reading and unlawfully under another. "It was legally exported" is not, on its own, a clean answer.

What the Society of Vertebrate Paleontology asked for

On 21 April 2020, the SVP wrote to more than 300 journals requesting a publication moratorium on "fossil specimens in amber from Myanmar after June 2017, when the Tatmadaw began its" offensive to seize the mines. The June 2017 line is the point at which the SVP considered the material's route to market to have changed.

After the February 2021 military coup, the SVP wrote a second letter stating that "a continued moratorium is still warranted on the publication of fossil specimens in amber obtained from sources in Myanmar after January 2021." That letter names the military-linked conglomerates Myanmar Economic Corporation (MEC) and Myanmar Economic Holdings Ltd (MEHL).

Neither letter is a law, and neither can compel anyone. They are a professional body asking journals to use the one lever the field actually controls: publication.

How the field actually responded

Unevenly. Some journals changed policy — the Journal of Systematic Palaeontology and Acta Palaeontologica Polonica among them. Others dissented, and publication of Burmese amber material continued.

The measurable result: of 222 amber papers published between June 2020 and June 2022, only 9 — about 4% — addressed the ethical issues at all. That figure comes from a systematic survey of the literature, not from advocacy. It is the clearest available statement of where the field stands: the moratorium was requested, discussed, and largely not reflected in what got published.

What would change this

A standing policy should say what would move it. Ours would change on a formal resolution of the SVP moratorium — a withdrawal, a revision of the dates, or a successor position from the society. Short of that, the June 2017 and January 2021 lines stand, and this page gets re-checked against the SVP's current position rather than left to age quietly.

• Displayed: amber material with documented pre-June-2017 provenance, labelled as such.
• Described but not displayed: findings from material we cannot date to before June 2017 — reported with the provenance gap stated.
• Not used: material identified as obtained after January 2021, or traceable to MEC or MEHL.

DIRECT Solnhofen Limestone — Bavaria, Germany

The limestone here is so fine-grained it was quarried to make printing plates, and that same grain size is why it recorded feather impressions rather than just bones. Solnhofen is where the transitional evidence first became impossible to ignore: an animal with asymmetric flight feathers on its wings and tail, and with teeth, a long bony tail, and clawed hands.

Archaeopteryx is best read as a historical anchor rather than a singular "first bird", and the site's own taxa record makes that point. Note also that this site's older pages disagree with each other on how many Solnhofen specimens are known — that count needs checking against a primary source before any number goes back on the page.

DIRECT Yixian & Jiufotang Formations (Jehol Biota) — Liaoning, China

If one place carries this volume, it's Jehol. Repeated ash falls buried lake-basin animals fast enough to preserve integument, and the result is a run of taxa that pinned down when specific bird traits appeared. Sinosauropteryx gave countershading and a banded tail. Microraptor gave a four-winged body plan and, through melanosome geometry, glossy black plumage. Caudipteryx gave symmetrical vaned feathers on an animal that could not fly — the cleanest single argument that pennaceous feathers came before flight. Confuciusornithids and Sapeornis fill in the early avialan grades above Archaeopteryx.

Yutyrannus huali, from the Yixian Formation at roughly 125 Ma, is the largest dinosaur with direct feather evidence: long filaments preserved on more than one specimen. The often-quoted holotype mass of about 1,414 kg comes to us through secondary reporting and should be verified against the primary paper before it's published as a hard number.

Two records usually grouped with Jehol actually come from an older window in the same region: the Tiaojishan and Haifanggou Formations at roughly 163–160 Ma, which produced Anchiornis huxleyi (Liaoning/Hebei) and the membrane-winged Ambopteryx longibrachium. Worth keeping separate, because that older window is Late Jurassic, not Cretaceous.

Discrepancy to resolve: the site's taxa record places Mei long in the Yixian Formation, Liaoning, while the sites brief lists it with the Gobi material. Both cannot be right. Verify before publishing either.

DIRECT Burmese Amber — Kachin State, Myanmar

Amber preserves what rock flattens. Kachin amber holds feathers and small bird body parts in three dimensions, at a level of structural detail no compression fossil matches — including a reported Stage IIIb down feather that would sit neatly inside the Prum & Brush developmental model. That report is a 2020 preprint (Roy et al.) and has not been treated here as settled.

This material also comes with a problem that the science does not resolve. Amber from Kachin State is linked to armed conflict and human-rights abuses, and Myanmar's export law treats it ambiguously — gemstone or fossil, depending on which statute you read. The Society of Vertebrate Paleontology has asked journals for a publication moratorium on material collected after specific dates. Our policy, and what we will and won't show, is set out in full in the standing Burmese amber ethics statement. Nothing on this site sourced from Kachin amber appears without documented pre-June-2017 provenance.

DIRECT Djadokhta & Barun Goyot Formations — Gobi Desert, Mongolia

The Gobi's contribution isn't feathers — it's behaviour caught mid-act. Oviraptorid specimens including Citipati are preserved sitting on top of their own egg clutches with the arms drawn over the eggs, which is bird-style nest attendance recorded directly rather than inferred. Velociraptor mongoliensis comes from the Djadokhta, and carries ulnar quill knobs: skeletal attachment points for large pennaceous feathers on an animal that could not fly.

The Gobi also produced Mononykus, a small alvarezsaurid with drastically reduced, single-clawed forelimbs. Its skeleton is direct evidence; its feathering is bracketed from relatives, not preserved. It's a useful reminder that "bird-like" body plans arose more than once and in odd directions.

DIRECT Hell Creek Formation — Montana and the Dakotas, USA

Hell Creek is the last pre-impact ecosystem in the Northern Hemisphere and it contains the boundary layer, so it does two jobs at once: it shows who was alive, and it shows the moment. The Chicxulub impact is dated to 66.038 ± 0.011 Ma, and the palynological record across the boundary preserves the global forest collapse as a "fern spike".

It also hosts this volume's honest limit case. Skin impressions from Tyrannosaurus rex — abdomen, thorax, neck, pelvis, tail — show scales across the preserved regions. Extensive feathering is not supported by that evidence. Because the dorsum has no skin impressions, sparse or patchy feathering can't be strictly excluded, but a fully feathered T. rex runs against what's actually preserved. Set alongside the feathered basal tyrannosauroid Yutyrannus, the pattern reads as a reversion to scales in the derived giants, possibly tied to size. That reading is still argued over, and we leave it argued over.

Anzu wyliei, a roughly 3-metre caenagnathid oviraptorosaur, comes from the same formation. Its skeleton is direct; its feathering is bracketed from oviraptorosaur relatives.

DIRECT Messel Pit & Green River Formation — the handoff to Volume I

This is where Volume II hands the story to Volume I. Both sites preserve small Eocene landbirds in articulated, often near-complete condition, and among them are the halcyornithids — stem representatives of the parrot total group. Cyrilavis colburnorum comes from the Green River Formation's Fossil Butte Member in Wyoming; Pseudasturides and Serudaptus come from Messel; Pulchrapollia comes from the London Clay. Together they're the closest thing we have to a fossil approach to living parrots.

The family name has a tangle behind it: Halcyornithidae (Harrison & Walker, 1972) is the senior synonym of Pseudasturidae (Mayr, 1998).

CONTESTED What the stem-parrot record does not settle

Three things are worth stating plainly before anyone reads the Eocene material as "early parrots".

• Halcyornithid placement is unresolved. Recent literature describes it as elusive. These are stem representatives on current readings, and current readings are moving.
• Psittacopes has probably switched sides. Long treated as parrot-like, it is now more often placed on the passerine stem within Psittacopasseres. Older site copy that lists it as a stem parrot is out of date.
• No crown parrot is known from the Paleogene at all. The origin of crown Psittaciformes rests on molecular dating, which supports a Gondwanan/Australasian origin — Late Cretaceous under the favoured calibration at roughly 80 Ma, but calibration-dependent across a 50–82 Ma range. Give the range, not a date.

Parrots are the closest living relatives of passerines, in the clade Psittacopasseres within Eufalconimorphae. That relationship is well supported; the fossil calibration of when it happened is not.

Other localities carrying single load-bearing fossils

Not every important specimen comes from a famous deposit. Several of this volume's key records are effectively one place, one fossil.

• Niobrara Formation and the Western Interior Seaway, North America — Ichthyornis dispar, the gull-sized toothed ornithuran whose CT-reconstructed skull shows a still-toothed jaw with a small kinetic beak tip and a modern-grade brain; and Hesperornis regalis, a roughly 1.5 m flightless foot-propelled diver. Between them they show the ornithuran radiation was already specialising before the impact. 10.1038/s41586-018-0053-y
• Vega Island, Antarctica — Vegavis iaai, Maastrichtian (~68–66 Ma). A second specimen preserves the oldest known fossil syrinx, three-dimensionally and asymmetrically, implying honking vocalisations. It remains the only Mesozoic syrinx known. 10.1038/nature19852
• Maastricht Formation, Belgium — Asteriornis maastrichtensis, the "Wonderchicken", at roughly 66.7 Ma: a small (~395 g) long-legged near-shore stem galloanseran, skull recovered by CT, living somewhere in the order of 300,000–800,000 years before the boundary. Its Northern-Hemisphere occurrence complicates a strictly Gondwanan origin for crown birds. 10.1038/s41586-020-2096-0