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Hesperornis regalis was but one of many species in its genus, many of which lived in the Western Interior Seaway of Cretaceous North America. This toothed early bird was similar in many ways to today's grebes, loons, and penguins. It possessed short flipper-like wings that would have been somewhat useful for steering underwater, but certainly not for flight. Its legs were fixed at the ankle to the side of the body, and couldn't have been used for walking. On land, it would have had to push itself around with its toes and scoot on its belly, much like a seal - but underwater, those broad lobed feet were perfect for propelling itself swiftly after fish and other marine life.
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Archaeorhynchus spathula is the earliest-known beaked bird. Found in the Early Cretaceous period in the Yixian Formation of China, these birds were capable of powered flight and were primarily herbivorous, probably filling a niche similar to today's pigeons. It is currently also the most basal member of the Euornithes known - Euornithes being the branch of birds encompassing all known modern species.
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My grandmother's 93rd birthday is coming up next week and I told her I would do some art as a gift. Little old ladies, my grandmother included, typically prefer extant dinosaurs to extinct ones, and she's a fan of hummingbirds, which she has lately been trying to attract to her yard. Rufous Hummingbirds (Selasphorus rufus) are a common sight here in the Pacific Northwest, and while they're drawn to a wide range of flowers, western red columbines (Aquilegia formosa) are one of their favorites.

And I think this bit of art stands as an interesting contrast to the rest of the dinosaurs, too - just look at how highly modified they've become over the last several million years! From one line of small theropods came an extremely wide diversity of modern birds with an astounding variety of shapes, sizes, and special adaptations for filling almost every niche on the planet.
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Yandangornis longicaudus is, as the name ("ornis") implies, a bird. We think. It's actually very hard to say. Like birds, it is fully-feathered and has a beak with no teeth. However, it also has a long bony tail, a short fourth toe, and other skeletal features that make it more similar to dinosaurs. Since birds are dinosaurs, the distinction is purely one of interest to taxonomists, who work to figure out which species are more closely related to which other species. From a taxonomic perspective, Yandangornis is a dinosaur, as are all birds - but whether or not it can be called a bird for sure is still up for debate. Discovered in Zhejiang Province, China in 1999 from a largely intact skeleton, we do know that it was more adapted for ground-dwelling than aerial or arboreal life, and was similar in size and habit to today's roadrunners, likely chasing down insects, small reptiles, and primitive mammals on foot.

As a heads up, updates will be spotty over the next couple weeks as I finish my thesis and prepare my defense. I'll try not to go full hiatus on you guys!
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As anyone following this blog is well aware, dinosaurs did not go completely extinct 65 million years ago. A few small genera were able to survive the mass extinction, and one branch in particular became the Avialae, which we know today as birds. They diversified, colonizing habitats their ancestors had once ruled, but now having to compete with mammals as well, which previously had been primarily underground and nocturnal but now found themselves with a variety of niches to exploit.

While many birds were lightweight and airborne, a few different lineages returned to a shape similar to that of their ancestors - the ratites (ostrich, emu, and their relatives), the Gastornithiformes (large predatory ground-dwelling relatives of ducks), the Secretary Bird, and the seriemas, to name a few. But the most striking in terms of convergent evolution with ancestral dinosaurs were the now-extinct Phorusracidae - massive T-rex-like falcons, including the species pictured above, Titanis walleri. It was an estimated 8 feet tall and 330 lbs, and during the last ice age, it ruled the plains of southern North America, once again forcing the smaller mammals to hide or risk being eaten in one great gulp.
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Scansoriopteryx heilmanni is currently only known from the fossil of a hatchling, so exact adult proportions are still unknown. However, like most baby animals today, juvenile dinosaurs had large heads, large eyes, large feet, and short snouts relative to their body length, so estimating the proportions of the adult isn't impossible. One unusual feature, unique to the scansoriopterygidae, is that the third finger on the hand is extremely long. Most dinosaurs have a medium to short first finger, a long second finger, and then a shorter third finger. Czerkas (of the same museum I posted about earlier) suggests that this long third finger, plus its generally very long arms (as compared to the legs) may mean this family of dinosaurs were adept climbers, though others have speculated that the long third finger is an adaptation for fishing out insects from crevices in bark or rocks, like the aye-aye of today.

Wow, 20 drawings already! This one is awfully late, I know, but it's still the 28th here in Pacific Time. Moving complete, for now.
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So since my Qiliania the other day was so tiny on the snout of that Argentinosaurus, I felt it necessary to give it its own portrait. So here you go, a much closer look at the smallest-known non-extant dinosaur. Like other Enantiothornithines, it has developed a pygostyle instead of a long bony tail, asymmetrical wing feathers, and other traits that make it very similar to modern birds, though it still lacks a beak, and instead has a toothed snout. Whether these guys were capable of true flight, we're not yet sure. Instead, it may have been primarily a ground-dweller, and used its wings for wing-assisted incline running (WAIR). Many ground birds today still do this, using their wings primarily to help propel them up a slope without truly leaving the ground for more than a few seconds, and it has been proposed that the use of WAIR by early winged dinosaurs eventually led to the evolution of powered flight.
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Last week, a paper was published in PLOS Biology by a team of Oxford scientists who, based on skeletal measurements, calculated the masses of 426 species of dinosaur. The largest, Argentinosaurus, was a massive sauropod weighing in at roughly 90 tons, while the smallest they measured was Qiliania, an Enantiornithine bird that weighed 15 grams, making the weight of the largest dinosaur 6 million times the weight of the smallest non-extant known species (the smallest-ever dinosaur known is the Bee Hummingbird of Cuba which weighs 2 grams). It's suspected that size played a large role (no pun intended) in the survival of the maniraptorans past the mass extinction 65 million years ago, as the smallest dinosaurs may have been able to avoid the worst effects of the asteroid impact by being more generalist, requiring fewer resources, and/or being able to exploit niches not available to larger species.

Update: today (5/16/14) a team of paleontologists in Argentina announced they've found a new sauropod species that may be even bigger than Argentinosaurus, and estimate its weight at 100 tons. Should be interesting to see what comes of this new discovery.
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Confuciusornis is a genus of four to six known pigeon-sized theropods (at least two may represent the same species) from Jurassic China that appear to be more closely related to true birds than Archaeopteryx is. They are the oldest-known birds with beaks instead of scaly snouts, they have no teeth, and they have a pygostyle instead of the long bony dinosaur-like tail. They have very long pointed wings and asymmetrical flight feathers, making them altogether more like modern birds than any other known creature of their time, but skeletons indicate they weren't capable of powerful flapping flight and may instead have been gliders.

Fossils of this genus have been found in vast quantities, and places where entire flocks of hundreds of birds were preserved simultaneously have been found. They are so abundant that long before they were known to science, several hundred had been collected and sold in Chinese street markets - and this, in fact, is how the first Confuciusornis to be described in the scientific literature was initially found. The colors in this drawing are accurate, but the pattern is not - I was able to find several references that they were gray, brown, orange/red, black, and white, and that the wings were mostly white, but I couldn't find anywhere that showed the exact pattern of how these colors were laid out on the body.


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Lauren Helton

September 2014



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