What percentage of theropod dinosaurs were feathered?
FAMILY LIST / Theropoda
The Theropoda ("Animal feet") were two-legged (bipede) carnivores (carnivores) with sharp teeth and claws on their grasping hands, among others these were Allosaurus and Neovenator and their descendants, the birds (Aves). The Theropoda belong to the lizard-hipped dinosaurs (Saurischia) and were widespread worldwide. They evolved into the largest land-dwelling carnivores like Spinosaurus and Carcharodontosaurus, but the vast majority of this group was rather small, such as Compsognathus or Microraptor.
The theropods usually had a fairly large skull with large eyes, and also had a good sense of smell and hearing. The teeth were flattened on the side and curved back a little. The teeth had small jagged edges on the leading edge, and because they were at right angles to the cutting edge, they were extraordinarily sharp. The legs were vertical and centered under the body, which was balanced over the pelvis. The animals kept the spine mostly horizontal, the neck mostly curved in an S-shape. When running fast, the theropods were able to shift their tails upwards, which enabled them to better maneuver when chasing prey.
Majungasaurus / © Raul Lunia
There were big differences in the function and appearance of the forearms. In some animals, the gripping function of the hand (e.g. the Velociraptor) certainly played a major role. However, some large theropods such as the tyrannosaurs had very much reduced fore limbs, these large carnivores could not reach the mouth with their stubby arms, and the function of the short arms is not clear. The theropod's legs were significantly longer than the arms and the lower legs longer than the thighs. This suggests that many of these animals were able to run at high speeds, at least for a short time. Toes II, III and IV were directed forward. These were the walking toes, the short inner first toe did not touch the ground, the outer fifth toe was reduced to a stump bone. The toes ended in pointed horn claws. There were also big differences in the texture of the skin. If the overwhelming number of theropods probably had a lizard-like scale skin, some species developed such as Sinosauropteryx in the Cretaceous period a plumage that was not used for flying but rather as protection against the cold.
Since many dinosaurs are very closely related to birds, many were feathered as well. With the theropods like for exampleVelociraptor this is considered safe. However, some well-preserved fossils also contain imprints of down and feathers, for example those of theSinornithosaurusin which down-like structures are visible that run along the back. Protarcheopteryx had a small fan made of feathers at the tail end. However, these were not yet feathers as we know them from today's birds, but so-called proto feathers, which are comparable to down. The feathers developed from skin flakes or small skin thorns. Oviraptors also probably had thin plumage, as in close relatives like Caudipteryx fossil evidence of feathers has been preserved. Chinese researchers discovered three skeletons of the in 2011 in Liaoning Province in northeast China Yutyrannus. What is special about these finds is that imprints of feathers have been preserved on the three almost complete skeletons of this large theropod. However, these are more like a fluff than the feathers that today's birds have. The narrow so-called proto feathers were aligned parallel to each other and about 15 centimeters long. Their distribution on the body suggests that these dinosaurs from the tyrannosaur family had a densely feathered skin structure. Until the discovery of the Yutyrannus the researchers assumed that only the smaller dinosaurs were feathered. The discovery of this species makes it more likely that adult tyrannosaurs also had plumage.
In 2015, the scientist Martin G. Lockley and his colleagues presented an interesting scientific work on the mating behavior of theropods. According to this, some theropods apparently scratched their feet in the ground like chickens during courtship. The researchers examined several theropod footprints in four locations in the US state of Colorado in the Dakota Sandstone Formation, whose rock layers date from the mid-Cretaceous period about 100 million years ago. They discovered hollows from which apparently sand was being scraped. They found 60 symmetrically arranged hollows that were up to two meters long and up to 25 centimeters deep. The researchers ruled out scratching to build nests or looking for water and food because they found no evidence of nests or prey. They therefore assume that at certain times of the year, probably in spring, the scratching was used for courtship. Many recent birds such as the puffin or the African ostrich do this today too.
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Developmental and evolutionary novelty in the serrated teeth of theropod dinosaurs
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Evolution of high tooth replacement rates in theropod dinosaurs
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Theropod dinosaurs from Argentina
Martin Daniel Ezcurra, Fernando Emilio Novas, 2016
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Theropod dinosaurs from the Upper Cretaceous of the South Pyrenees Basin of Spain
Angelica Torices, Philip J. Currie, Jose Ignacio Canudo, Xabier Pereda-Suberbiola, 2015
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Theropod footprints from the Lower Cretaceous Cangxi Formation in the Northern Margin of the Sichuan Basin, China / Lida Xing, Martin G. Lockley, Bolin Tong, Hendrik Klein, W. Scott Persons IV, Guangzhao Peng, Yong Ye, Miaoyan Wang, 2021 / Biosis: Biological Systems, 2 (1), 174-182PDF
Theropod teeth from the upper Maastrichtian Hell Creek Formation “Sue” Quarry: New morphotypes and faunal comparisons / Terry A. Gates, Lindsay E. Zanno, Peter J. Makovicky, 2015
Acta Palaeontologica Polonica 60 (1), 2015: 131-139 doi: http://dx.doi.org/10.4202/app.2012.0145 /PDF
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Theropods size and body mass table // Dinodata.de:
Creative Commons 4.0 International (CC BY 4.0)
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Graphics and illustrations by Raul Lunia
Graphics and illustrations of Martin F. Chavez
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