Episode 458: Beyond Bones: Feathers. Plus a mammal found fossilized on top of (and likely fighting) a Psittacosaurus

News:

• A new recreation of the color on Wulong’s impressive feathers source
• Beetles found in amber munching on cretaceous dinosaur feathers source
• 2004 paper about the first ever parasitic louse found in the fossil record (which was eating dinosaur feathers) source
• Most (maybe all) modern birds molt at least once a year, but Mesozoic dinosaurs may have molted less frequently source

The dinosaur of the day: Caudipteryx

• Basal oviraptor theropod that lived in the Early Cretaceous in what is now Liaoning Province, China (Yixian Formation)
• Looked very birdlike, covered in black downy feathers, with long legs, a long neck, short arms with feathers on it, tail feathers, and a rounded snout
• Peacock sized
• Estimated to be almost 2 ft 5 in to nearly 3 ft (about 0.7 to 0.9 m) long and weigh 11 lb (5 kg), based on its femur
• Very light, with delicate bones
• Had a box-like skull
• Had large eyes
• Had a short snout and not many teeth
• Had small, weak teeth
• Had a hallux (first toe) that may have been partly reversed/backward facing and had body proportions like modern flightless birds
• Probably could perch, like some modern birds
• Like early birds and the oviraptorid Heyuannia, had a short third finger on its hands
• Had short claws on its hands
• Hand is longer than either the humerus or radius (arm bones)
• Had long legs, and probably was a fast runner
• Thought to be secondarily flightless (evolved from animals that could fly)
• Had a highly developed wishbone, or furcula, like modern birds
• Wishbone similar to Archaeopteryx, Confuciusornis, and other non-avian theropods
• In 2019, Arindan Roy and others found the feathers of Caudipteryx to be black and the tail feathers to have a banding pattern
• Had a short tail that was stiff toward the tip/end, similar to birds and oviraptorosaurs
• Had a fan of feathers on its tail
• Had feathers with vanes and barbs on its hands (between almost 6 to 8 in or 15 to 20 cm long)
• Had longer, symmetrical feathers on its arms and tail, probably for display or brooding (symmetrical feathers means it couldn’t fly)
• Downy feathers probably kept it warm
• In 2018, Yaser Talori and others experimented with a robot Caudipteryx with realistic wing proportions to test if the feathers on the wings helped it run faster
• Found that if wings were fixed and extended out, would have only helped with small amounts of lift and drag. Same with flapping while running
• Based on results, found that its feathers were probably for display
• Possibly helped with turning, like ostriches do
• In 2019, Yaser Talori and others re-examined how Caudipteryx used its feathers and used the robot again
• Estimated the max running speed to be about 8 m/s (meters per second)
• Found that while running, there would have been some forced vibrations that taught it to flap its wings
• In 2022 Jing-Shan Zhao and others, including Yaser Talori, went back to the Caudipteryx robot and found more support that flapping evolved long before feathered dinosaurs could fly (flapped while running on the ground)
• Probably omnivorous, though possibly an herbivore
• Possibly ate insects and plants
• Two individuals have been found with gastroliths
• Had a long neck, with ten vertebrae (later one individual found with 12 vertebrae)
• Based on the neck and gastroliths, thought to be possibly herbivorous
• Two species: Caudipteryx zoui and Caudipteryx dongi
• Type species in Caudipteryx zoui
• Genus name means “tail feather”
• Named by Ji Qiang and others in 1998
• Several skeletons have been found, and first bones found in 1997
• Type specimen found was close to mature when it died, based on fusions and ossifications in the bones
• Species name “zoui” refers to “Zou Jiahua, vice-premier of China and an avid supporter of the scientific work in Liaoning”
• Second species, Caudipteryx dongi, named in 2000 by Zhong-He Zhou and Xiao-Lin Wang
• Nearly complete skeleton found in 1998, with well preserved wing feathers, nearly complete arms, hindlimbs, and pelvis (no skull)
• More articulated than the type species, and was a large individual
• Caudipteryx dongi had a relatively long upper half of the pelvis, compared to Caudipteryx zoui, and smaller sternum (middle part of chest)
• Had a short first toe (hallux) that faces backward, so may have been able to perch
• Had skin impressions on the arms and hands, and “the skin doubles the width of the digits when the animal was alive”
• Species name “dongi” “refers to Zhiming Dong, a distinguished Chinese dinosaur expert”
• Not all scientists think Caudipteryx is an oviraptor
• Some scientists think it was a bird
• Because of Caudipteryx, there’s been lots of debate about how birds and dinosaurs are related
• In 1998 when Caudipteryx was named, there was debate on the origin and evolution of early birds and whether they evolved from coelurosaurian theropods
• When named, authors said Caudipteryx represents “stages in the evolution of birds from feathered, ground-living bipedal dinosaurs”
• Clump of feathers preserved on the chest
• Authors named Caudipteryx based on two nearly complete, partially articulated skeletons with feather impressions on the arms, tail, and body (found in 1997). Originally thought to be a maniraptoran that’s closer to birds than other dinosaurs (lots of discussions since, and had been compared with oviraptors and flightless birds)
• When Caudipteryx was described, it was thought to provide the first evidence of feathers in dinosaurs. But Zhou and Wang wrote: “This opinion, however, has been challenged by many paleornithologists who suggest that Caudipteryx was probably a flightless bird, a “Mesozoic kiwi””
• In the paper naming Caudipteryx dongi, interpreted Caudipteryx as a feathered dinosaur, but authors said “we believe the debate on the dinosaurian or avian state of Caudipteryx and oviraptorids will continue”
• In 2000, Jones and others said Caudipteryx was a flightless bird, based on comparing body proportions of flightless birds and non-avian theropods
• In 2002, Teresa Maryanski and others found Caudipteryx to be both oviraptor and bird (had feathers, oviraptors found to brood eggs)
• In 2005 Gareth Dyke and Mark Norell found Caudipteryx to be a non-avian theropod and not a flightless bird
• Proportions of leg bones and center of mass are more similar to modern running/cursorial birds than non-avian theropods, which is why some scientists found it to be a flightless bird
• Dyke and Norell argued that the conclusion that Caudipteryx was a flightless bird was based on the assumption that birds are not related to non-bird theropods
• Lawrence Witmer said, “The presence of unambiguous feathers in an unambiguously non-avian theropod has the rhetorical impact of an atomic bomb, rendering any doubt about the theropod relationships of birds ludicrous.”
• In 2000, Xiaolin Wang and others studied two new specimens of Caudipteryx (each had skulls and were nearly completely articulated)
• One referred to Caudipteryx zoui, the other an indeterminate species
• Found lots of birdlike features but still found it to be a feathered dinosaur
• Found hallux is at least partially reversed (backward), so ancestor of Caudipteryx probably was able to hang out in trees
• Specimens are slightly smaller than the other ones found
• But their leg to arm ratio was smaller than the larger specimens, which may mean the arms developed earlier than the legs
• In 2021, Xiaoting Zheng and others studied cartilage of Caudipteryx (soft tissue!)
• Demineralized the material and said it “shows exquisite preservation”
• Found chondrocytes, which maintain cartilage and one had a nucleus and “fossilized threads of chromatin” (which is a mix of DNA and proteins that form the chromosomes found in cells), and said it “retained some of their original chemistry”
• Said it was the second example of fossilized chromatin threads. First one was found in cartilage of the hadrosaur Hypacrosaurus
• Paper said, “These data show that some of the original nuclear biochemistry is preserved in this dinosaur cartilage material and further support the hypothesis that cartilage is very prone to nuclear fossilization and a perfect candidate to further understand DNA preservation in deep time”
• Authors said nuclei thought to degrade quickly after death, but there are lots of fossil tissues with preserved nuclei (“from permafrost-preserved Cenozoic mammals, Mesozoic dinosaurs, various Cenozoic, Mesozoic, and Paleozoic plants, and even embryo-like fossil cell clusters that are more than 600 Million years (My) old”)
• Also said recent taphonomy experiments on plants and algae showed nuclei to be more stable and decay slower than previously thought
• Cartilage found in mammals “is one of the most durable and decay resistant soft tissues of the body”, because it’s shielded by surrounding tissues, there’s no vascularization (blood vessels), which protects from microbial invasions, and has a “low cell density and its cells have an anaerobic metabolism” (no oxygen)
• Chondrocytes have a delay when it comes to self destruction of cells and tissues (known as autolysis) which helps fossilize nuclei, and calcified cartilage seems to be even more decay resistant, so it’s not surprising that fossilized calcified cartilage has “exceptional cellular and nuclear preservation […] regardless of the age of the fossil”
• May take a few weeks for chondrocytes to decay after an animal dies, which means in order for nuclear preservation in cartilage, the animal doesn’t need to be buried immediately
• Compared Caudipteryx to a chicken and found similarities
• Based on the chemistry of the tissues and surrounding sediments, found iron and other materials helped in the preservation, and these other materials are common in the Jehol Biota (though the iron came later)
• Found a cartilage cell nucleus (which has genetic material)
• “Some of the original nuclear biochemistry is preserved in this dinosaur cartilage material”
• “It was recently proposed that even though DNA is apparently in a non-PCR amplifiable and non-sequenceable form in Mesozoic fossils, some of the original chemistry and molecules may still be preserved in the form of DNA fossilization products. This may explain why some dinosaur cells can still react with DNA stains, even though a DNA sequence has never been authenticated in any fossil much older than ~1.2 My. Although the results presented here are preliminary chemical data, they still support the hypothesis concerning DNA fossilization products and reaffirm that much more efforts need to be made to investigate all the unanswered questions about DNA preservation in deep time, especially in fossilized cartilage.”
• Other dinosaurs that lived around the same time and place include the tyrannosauroid Dilong and the dromaeosaur Sinornithosaurus

Fun Fact:

Small mammals sometimes attacked much larger dinosaurs in the Mesozoic. A new fossil seems to show a Repenomamus (a mammal) attacking a Psittacosaurus.

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