The Big Dinosaur Podcast

Episode 299 is all about Sinosauropteryx, One of the first known feathered dinosaurs, known for its long banded tail.

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In this episode, we discuss:

News:

• A new carcharodontosaur, Lusovenator, was named in Portugal source
• A new analysis dates the Carnian Pluvial Episode to 234 million years ago source
• Universiti Malaysia Kelantan recently found dinosaur footprints in Bukit Panau source
• There is a way to hack the hidden Google Chrome dinosaur game to make your T. rex invincible source

The dinosaur of the day: Sinosauropteryx

• Compsognathid that lived in Early Cretaceous in what is now Liaoning Province, China (Yixian Formation)
• Small, longest specimen found was about 3.5 ft (1.07 m) long, and weighed about 1.2 lb (0.5 kg)
• Holotype was only 27 in (68 cm) long, but was a juvenile
• Bipedal, and had short arms, large claws on its first fingers, and a long tail
• Had 64 vertebrae in the tail, the longest tail relative to the body length of any known theropod
• Tail helped it balance while it ran
• Had long legs
• Arms were about 30% the length of the legs
• Hands were long compared to the arms
• Had three fingers on each hand
• Had a high skull
• Similar to Compsognathus
• Type and only species: Sinosauropteryx prima
• Genus name means “Chinese reptilian wing”
• Species means “first” and refers to the fact it’s the first, feathered, non-avian dinosaur found
• The original description of Sinosauropteryx found that this dinosaur “upsets and supersedes the over 100 year standing of Archaeopteryx as the ancestor to birds,” and that it shows Ostrom’s proposal that theropods turned into birds
• Described in 1996 by Ji and Ji
• First dinosaur outside of Avialae to be found with evidence of feathers
• Not closely related to Archaeopteryx
• Distantly related to Aves, so not a bird
• Discovered in 1996 by Li Yuman, a farmer and fossil hunter
• Fossils were in two slabs, and he sold them to two museums: National Geological Museum in Beijing, and the Nanjing Institute of Geology and Paleontology
• It was a big find, and got many scientists and artists excited, including Phil Currie, Michael Skrepnick, John Ostrom
• Three specimens have been found and described and assigned to Sinosauropteryx
• One of the specimens may be a new species or even a new genus, but hasn’t been officially named
• Carnivorous
• Ate insects and small mammals
• Had heterodont teeth, with teeth on the upper jaws were slender and not serrated, and teeth behind them on the maxillae were serrated
• One specimen found with lizard gut contents, likely Dalinghosaurus, a fast runner. Also found small eggs in the abdomen, though they were in the wrong part of the body for the egg shells to stay intact, so likely that they were unlaid Sinosauropteryx eggs. Eggs were 1.4 in (36 mm) long and 1 in (26 mm) wide. Having two eggs may mean Sinosauropteryx had dual oviducts, like other theropods, and laid eggs in pairs
• Another specimen, the one that may be another species or genus, was found with mammal jaws in its gut region, including the jaws of Zhangheotherium, a venomous mammal (had tarsal spurs, spurs on the feet, similar to modern platypus, which also produced venom)
• First non-avian dinosaur found with feather-like structures
• Had simple, filament-like feathers
• Feathers are short, small, and uniform
• Primitive feathers were up to 1.2 in (3 cm) long
• Could not fly, but feathers may have been for insulation or display
• Primitive feathers were short, down-like filaments, on the back of the head, the arms, beck, back, and top and bottom of the tail
• Feathers have also been found on sides of the body, in patches
• Chen, Dong, and Zheng suggested that based on the patches and randomness of the patches, it was probably covered in feathers when it was alive
• There’s a gap between the feathers and bones, which were probably filled in by skin and muscle tissue
• Scientists found by looking through a microscope that the filaments were dark along the edges and light inside, so they may have been hollow like feathers of modern birds
• Feathers are too dense to examine single structures, but may have had two types of filaments, thick and thin, where the thick ones were stiffer. The feathers may have had a central quill with thinner projections or barbs coming out, similar to modern bird feathers, but with more primitive structures
• In 2018, Evan Saitta and others did a study that found the thick filaments may actually be bundles of thin filaments. They found the thick filaments didn’t have any calcium phosphate, which is found in modern feather quills
• Suggested that Sinosauropteryx feathers were single-branch filaments, though maybe sometimes they joined at the base into tufts, kind of like down-like feathers
• The filaments were controversial at first, and thought by some to be collagen fibers instead of primitive feathers, and that these fibers formed a frill on the back and under the tail, like some modern aquatic lizards. Not having feathers would mean Sinosauropteryx was not the most basal known theropod with feathers, and would also call into question the theory that feathers evolved for insulation first, not flight, and that they appeared in basal dinosaurs that evolved into birds
• Many scientists did not agree that the structures were fibers
• Then a 2017 paper by Smithwick and others found that the structures were definitely not collagen fibers. They compared it to well known collagen fibers in the ichthyosaur Stenopterygius, and they found that the apparently shaft-like collagen fibers in the ichthyosaur were actually scratch marks and cracks, and the shafts in Sinosauropteryx were the actual fossilized structures
• They also found no evidence of the filaments having beaded structures similar to those found in decaying collagen in modern sea mammals, and suggested that parts of the fossil was preserved in 3D and cast shadows that looked like beaded structures in low quality photos
• In the holotype in the abdomen there’s a pigmented area that was thought to possibly be traces of organs, maybe the liver, that John Ruben and others described as part of a crocodilian-like “hepatic piston” respiratory system, a specialized breathing mechanism where muscles attached to the liver and pubic bones of the hip pull the liver back to inflate the lungs, for short bursts of running/activity
• A later study found that the pigmented area was probably part of an organ or something inside the body, the organs would have been distorted and flattened through the fossilization process
• Dark pigment was also found in the eye area
• First dinosaur to have colors scientifically described
• Had a reddish, light banded tail coloration
• Nick Longrich suggested in 2002 it had a banding pattern on the tail, alternating between dark and light colors, because the dark banded areas were so evenly spaced it couldn’t have been from random separation of fossil slabs, and so they were fossilized pigments. Also Sinosauropteryx may have had countershading, with dark feathers on the top of the body and lighter colors on the bottom, and bands on tail to help camouflage
• Fucheng Zhang and others in 2010 supported the idea, when they found evidence of preserved melanosomes, and they confirmed the dark and light tail banding of Sinosauropteryx. They compared melanosome types to those in modern birds and came up with a range of colors, and found the darker Sinosauropteryx feathers in the tail were chestnut or reddish brown (melanosomes were spherical in shape). Don’t know the color of the lighter stripes because some pigments degrade and can’t tell from fossils. Finding these melanosomes is more evidence these structures were feathers
• Later findings found it had a bandit mask like a raccoon around its eyes and had countershading patterns on its body, usually associated with an animal in an open habitat with not much covering, and not a dense forest, which means the Jehol Biota (Yixian Formation and Jiufotang Formation) had a variety of habitat types
• With the countershading, Sinosauropteryx could blend in
• Dinosaurs had good vision, so they needed camouflage. For Sinosauropteryx, needed to blend in to avoid predators and also to sneak up on prey
• Bandit mask may have helped with defense, to be a warning signal, though Sinosauropteryx was so small it probably wasn’t a threat to larger theropods
• Because the tail was so long, it probably couldn’t hold it’s tail perfectly horizontal all the time, so having the banded tail maybe helped throw off predators and prey, by being a distracting and drawing attention away from the head and body. Or possibly the banding made the tail less recognizable to predators
• Probably spent a lot of time in the sun, not in shade
• Lived in an area with freshwater lake, gymnosperm forests (like conifers), and lots of insects, bivalves, and gastropods, as well as mammals and birds. Lots of volcanic eruptions, wildfires, and noxious gases that came from the lakes. But it was temperate with wet and dry seasons (yearly temperature was 50 F (10 C)

Fun Fact: The Carnian Pluvial Explosion was a very rainy period in the Triassic when many early dinosaurs show up in the fossil record.

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