Vegavis and the Honks of the Cretaceous

In mid-October, a [paper] was published that described the first voicebox ever found for an ancient bird. Let’s dive right in!

Off the coast of Antarctica, there is an island called Vega. It sits just east of the Antarctic Peninsula.

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Google map of Vega Island, Antarctica.

Two specimens of the extinct duck, Vegavis iaai were found on that island in the early 1990s. The name means ‘bird of Vega’: “Vega” for the island where it was found, “avis” meaning bird in latin, and “iaai” for the Instituto Antártico Argentino (IAA), which led the expedition. The fossils date back to the late Cretaceous (69-66 million years ago).

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Vegavis by M. Skrepnick.

These specimens are amazing because they show us that modern groups of birds, like the ducks, were already present in the Late Cretaceous. Now the story gets even cooler. The authors of this paper CT scanned the second specimen of Vegavis and noticed something that had never been found in a dinosaur fossil.

This specimen has a voicebox preserved in its chest! Many animals produce sounds using their larynx (a section of the windpipe, or trachea, that houses the vocal chords). In birds, the voicebox (called a syrinx) is actually lower in the chest, at the base of the trachea.

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A mammal voicebox on the left and a bird voicebox on the right. Images modified from the National Institutes of Health and the Cornell Bird Lab.

This structure is made of cartilage and can fossilize easier than soft tissue, however, no one has ever found a fossilized syrinx until now. Using CT scans, the authors found that the syrinx has fused rings, which is a feature usually found in more derived birds. They also found that the syrinx is slightly asymmetrical, which is only found in birds with two sound sources. Sometimes this asymmetry can be used to tell the sex of the bird as males will have more asymmetrical syrinxes.

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Vegavis with its syrinx by N. Fuller/Sayo Art/UT Austin.

Because Vegavis was found to be an early duck, and because of the features of the syrinx, the authors think that Vegavis was probably able to produce honks and other simple calls like modern ducks and geese make.

The question is – why do we only find syrinxes in the Late Cretaceous? Crocodilians have a larynx that only has a little mineral component, meaning it doesn’t fossilize as well. We don’t know what dinosaurs had, but we do know that at some point they had to evolve a syrinx since that’s what birds have today. Perhaps we do not find earlier fossil syrinxes because they were only evolved later in bird evolution. Or maybe we’ll find earlier syrinxes in the fossil record. What do you think we’ll find?

A Tiny Pterosaur

This week, an [article] was published about a new pterosaur specimen. The specimen was found in British Columbia, Canada and is from the Late Cretaceous (around 83-76 million years ago). The specimen includes a humerus and some vertebrae.

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Figure 1 from the paper showing the location of the new specimen.

Pterosaurs are among my favorite animals. They were one of three vertebrate groups that was able to fly. They have a huge diversity in head shapes, feeding styles, and body sizes.

Pterosaur diversity sergey krasovskiy

Pterosaur diversity by S. Krasovskiy.

Pterosaurs share many flight-related features with birds, like hollow bones, long arms, fusion of many of their bones, but they fly in a completely different way. Birds have long arms with fused hands at the end and asymmetrical feathers that allow them to create lift. Pterosaurs also have long arms, but instead of fusing their hands, they extend and embiggen their ring finger. Instead of feathers, pterosaurs had a skin membrane that extended from their hips (or ankles in some) to the tip of their ring finger. In comparison, bats also use a skin membrane, but they have all of their fingers in the membrane instead of just one.

wing comparison

These are all different solutions to being able to fly.

This new specimen of pterosaur is known to be an azhdarchid because of features in its bones. Another famous azhdarchid pterosaur is Quetzalcoatlus, which had the height of a giraffe and the wingspan of a Cessna airplane.

Queztal Mark Witton

Quetzalcoatlus with a giraffe for scale. By M. Witton.

Now, the interesting thing about this pterosaur is that it’s very small. Most pterosaur fossils from the Late Cretaceous are very large (like Quetzalcoatlus), even though they started out very small in the Triassic and Jurassic. This new specimen is comparably tiny, with a wingspan of only 1.5 meters. And it’s not a baby. Based on microscopic features of the bones, the authors think this specimen is a late-stage juvenile (like a teenager) or a sub-adult.

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Figure 6 from the paper showing the new pterosaur with a cat for scale.

Why is that important? Remember how I said that birds and pterosaurs are very similar. When you have animals that have similar habits and habitats, they tend to compete for resources, like foods and shelter. There is a hypothesis (a testable scientific idea) that pterosaurs had to get really large because birds out-competed them at smaller sizes. This new specimen shows that small pterosaurs still existed during the Late Cretaceous. The authors also note that since we don’t find baby pterosaurs in the Late Cretaceous, that maybe small pterosaurs existed, but weren’t fossilized.