Dr Steve Brusatte: Here’s why some birds survived the asteroid event for SciAm

In an online Scientific American article
“An asteroid extinguished all the dinosaurs except for birds. Here’s why.” paleontologist Steve Brusatte makes the weakest case I have seen since his YouTube video on the same topic.

Click to view YouTube video of Brusatte on SciAm.

Brusatte continues
“In fact, many birds were also extinguished in the fire and fury of the asteroid. Most of them—maybe nearly all of them—followed T. rex to the grave. One estimate puts the scale of bird extinction from this catastrophe at more than 90 percent.”

“Why did only a few birds survive?”

The captions
on the illustration tell Brusatte’s side of his poorly formulated story. “Only birds belonging to modern lineages managed to survive the asteroid apocalypse.”

This is a truism. Survivorship bias. A logic fallacy.

“LOSERS: Pengornis and other archaic birds whose lineages were wiped out by the asteroid had teeth in their jaws, large claws on their hands, a long, bony tail and a small breastbone.”

Unfortunately the illustration shows a bird with tiniest of teeth, claws no larger than those of an emu, a short pygostyle and a breastbone only slightly shorter than the robust humerus.

“WINNERS: Vegavis, an early member of the duck and chicken family, had several traits that scientists suspect were key to the success of modern bird lineages: small body size, a beak instead of teeth, large wings, powerful chest muscles, and a shorter tail that served as an aerodynamic rudder.”

Unfortunately, Vegavis is not a member of the duck or chicken family in the large reptile tree (LRT, 2340 taxa). Vegavis does nest near the base of all crown = extant = modern birds as a basal palaeognath. Chickens and ducks are not primitive – except in genomic tests, which too often fail like this example.

In the LRT toothless Early Cretaceous Archaeorhynchus is the last common ancestor of all crown birds. It greatly resembles the extant kagu, Rhynochetos, a neognathid megapode now restricted to New Caledonia, only much smaller – not quite ankle high.

Unfortunately, in the Brusatte SciAm illustration, Vegavis is shown larger than the enantiornithine Pengornis. Tiny teeth are indeed missing, but the wings are not larger than in Pengornis. The breastbone is a smidge larger, but relative to the humerus length not relatively longer, but does have a low keel. A short pygostyle is also shown for Vegavis, but only the pre-pygostyle elements are known.

Bruasatte’s two sample taxa are separated by 55 million years. Not a fair comparison.

Brusatte continues
“The effects of the asteroid touched all corners of Earth, but no environment had it worse than forests.”

All corners? Or did refugia exist near the poles? Vegavis is from latest Cretaceous Antarctica, far from the equatorial impact site. Plants and animals near the poles were used to long periods without sunlight and cooler temperatures.

Terror birds have been found in Antarctica. They were big. Flightless. Theropod-ish. Their African ancestors, long-legged (not seed-eating) secretary birds,spends time hunting on the ground. Not a great flyer.

In like fashion, highly derived penguins and stilt-legged basal members of the duck/goose family appeared in the Early Paleocene fossil record. Evidently these derived taxa had their evolution = transition and radiation during the long Cretaceous period, tens of millions of year in length, despite a current lack of fossils.

Not supporting Brusatte’s hypothesis,
the kagu is a forest bird. So is the kiwi. 65 mya New Zealand and New Caledonia were at the antipodes = opposite side of the Earth from the asteroid impact site, having just detached from Antarctica. Were those refugia?

Brusatte continues:
“one plant resource remained available for those that could take advantage of it: seeds. Because crown-group birds had sharp, mobile nutcracker beaks, they would have been able to exploit seeds as food, whereas most other animals—including the archaic toothed birds—could not.”

Brusatte does not mention the kiwi or kagu.

Supporting Brusatte, according to Wikipedia,
“Scientists have hypothesized that the Archaeorhynchus had an herbivorous diet, due to the large numbers of gastroliths (stomach stones) found in the gut of all known specimens. High numbers of these gastroliths suggest that they were not swallowed accidentally.^[2] These stones would have been eaten to help break down food that the animal would not have been able to chew because it was toothless”

On the other hand, according to Wikipedia,
“The kagu is exclusively carnivorous, feeding on a variety of animals, with annelid worms, snails, and lizards being among the most important prey items,”

Brusatte brings up a new taxon, Tsidiiyazhi abini,
a 62mya “oldest tree-dwelling bird species” and species of mousebird from New Mexico. The bird “could flip its fourth toe backwards – an adaptation that was useful for climbing and grasping.”

Today mousebirds are restricted to Africa.

Brusatte continues,
“Indeed, if you examine the most up-to-date genealogies of today’s birds—such as the one presented in 2024 by Josefin Stiller of the University of Copenhagen and her colleagues based on entire genomes of hundreds of species—many major groups of contemporary birds are implied to have originated right after the end-Cretaceous extinction in an exuberant burst of evolution.”

Deep time genomic tests fail too often and omit fossil taxa. Use phenomic = trait-based studies, like the LRT. Plus – fossils are notoriously rare – mere pinpoints on the globe. Most of the time you don’t find fossils, unless you know those pinpoints.

Urocolius is a mousebird taxon tested in the LRT.
Mousebirds are highly derived in the LRT, restricted to tropical Africa and related to quetzals, restricted to tropical America. Both are derived from oceanic tropic birds and these arise from Western Hemisphere toucans and Eastern hemisphere hornbills and these are highly derived birds that had a last common ancestor that must have been present prior to the opening of the Atlantic Ocean during the Cretaceous.

Ksepka et al titled their paper,
“Early Paleocene landbird supports rapid phylogenetic and morphological diversification of crown birds after the K–Pg mass extinction.”

Perhaps the paper should have been called, Early Paleocene landbird supports widespread phylogenetic and morphological diversification of crown birds during the entire Cretaceous.”

Crown birds
radiated everywhere during the Cretaceous. We’re just now finding their fossils. Perhaps there were more refugia for the variety that was saved than just near the poles, like near the antipodes of the impact site. Perhaps some clades started over

A little advice:
Show up to every paleo discussion with a wide gamut resolved cladogram of fossil and extant taxa. That way you won’t be harried and hassled by amateurs who do have the falsifiable authority of their own LRT. Give your guesses a little more evidence to work with and don’t compare Early Cretaceous Pengornis to latest Cretaceous Vegavis for time-critical arguments.

References
Ksepka DT, Stidham TA and Williamson TE 2017. Early Paleocene landbird supports rapid phylogenetic and morphological diversification of crown birds after the K–Pg mass extinction. Proceedings of the National Academy of Sciences of the United States of America. 114 (30): 8047–8052.

wiki/Tsidiiyazhi

scientificamerican.com/article/an-asteroid-extinguished-all-the-dinosaurs-except-for-birds-heres-why

Source: https://pterosaurheresies.wordpress.com/2026/04/20/dr-steve-brusatte-heres-why-some-birds-survived-the-asteroid-event-for-sciam/