Episode 392: What makes a dinosaur a dinosaur?

Episode 392: What makes a dinosaur a dinosaur? How we differentiate dinosaurs from their closest kin like pterosaurs, crocodilians, and dinosauromorphs.

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The dinosaur of the day: Erlikosaurus

  • Therizinosaurid that lived within the Late Cretaceous in what’s now Mongolia (Bayan Shireh Formation)
  • Seems in Jurassic World: The Sport and in Jurassic World: Alive (and has fur like feathers)
  • Had a cumbersome physique, with a small head, giant claws, and physique most likely lined in feathers
  • Feather assumption primarily based on preserved feather impressions discovered on therizinosaurs Beipiaosaurus and Jianchangosaurus
  • Estimated to be 11 ft (3.4 m) lengthy and weigh 330 to 550 lb (150 to 250 kg)
  • Had a big humerus (about 12 in or 30 cm lengthy)
  • Had robust arms with lengthy claws
  • Had a backwards directed pelvis
  • Had claws on its ft, probably for self-defense
  • Had 4 toes on every foot
  • Had a considerably lengthy snout
  • Had a considerably lengthy mind
  • Had an enlarged forebrain, which can have helped with evading predators and social habits
  • Olfactory tract a lot bigger than the mind
  • Had a fairly good sense of scent and good listening to
  • Had good stability
  • Fossils present in 1972 throughout a Soviet-Mongolian expedition, together with a nicely preserved cranium, practically full proper foot, and practically full left humerus (different fossils discovered, together with fragmentary cervical vertebrae)
  • Described in 1980 by Altangerel Perle and Rinchen Barsbold
  • Kind species is Erlikosaurus andrewsi
  • Genus title means “Erlik’s lizard”
  • Genus title refers to Erlik, “the lamaist deity, king of the useless”
  • Species title is in honor of Roy Chapman Andrews
  • Second therizinosaur discovered within the formation
  • Discovered a really full cranium
  • Cranium has been described as “remarkably uncrushed”
  • Holotype cranium is about 10 in (25 cm) lengthy
  • In 1981, Perle named and described Erlikosaurus once more, as if it hadn’t been carried out already, however spelled it as Erlicosaurus
  • Most scientists think about Erlikosaurus to be legitimate
  • First therizinosaur, then referred to as segnosaurs, the place a whole cranium was discovered, which helped paleontologists study extra about this group
  • Therizinosaurs, often called segnosaurs within the Seventies, have been thought to not be dinosaurs. Then in 1970 Rozhdestvensky prompt they have been theropods
  • In 1980, therizinosaurs have been considered gradual and semiaquatic (however then extra therizinosaurs have been discovered, they usually have been seen to be extra theropod-like)
  • James Clark and others in 1994 redescribed the Erlikosaurus cranium and located the options to be in line with the concept that therizinosaurs have been theropods
  • In 2010, Gregory Paul prompt Erlikosaurus was synonymous with Enigmosaurus (named in 1983). They have been present in the identical formation and solely pelvic fossils have been discovered for Enigmosaurus (no pelvis discovered for Erlikosaurus). However not everybody agrees (the 2 species have been discovered in several elements of the formation, the higher and decrease boundary, and the hip of Enigmosaurus seemed very completely different from Erlikosaurus’s shut relative, Segnosaurus
  • Herbivorous
  • Had a big intestine to course of meals
  • Had a nicely developed keratinous beak
  • Had enamel in its jaws
  • May crop crops and strip leaves off branches
  • A research in 2013 by Stephan Lautenschlager and others CT scanned the cranium of Erlikosaurus and located the beak helped stabilize the cranium whereas it was consuming, which made the cranium much less prone to bend or get deformed
  • Earlier than the research, beaks have been thought to exchange enamel to make the top lighter, and ultimately assist with flight
  • A 2021 research by Fion Waisum Ma and others digitally modeled and simulated over 40 theropod jaws from 5 teams (included Tyrannosaurus, Velociraptor, ornithomimosaurs, therizinosaurs, and oviraptorosaurs) and located theropods advanced to have extra structurally stronger jaws to eat harder meals (jaws obtained extra secure when biting, and fewer prone to have bone fractures)
  • Jaws turned stronger in carnivores and herbivores
  • Erlikosaurus had downward-bending jaws that would assist relieve stress when cropping crops
  • Had a comparatively weak chew pressure in comparison with different theropods
  • In 2012, Stephan Lautenschlager discovered Erlikosaurus chew pressure was low in comparison with different theropods and in relation to its physique mass
  • Nevertheless, Komodo dragons are likely to have weak chew forces for his or her measurement
  • Keratinous beak was a bonus as a result of it’s all the time rising, so it may rapidly restore fractures
  • A 2015 research by Stephan Lautenschlager and others digitally modeled after which analyzed muscle pressure for 3 theropods when opening their jaws: Erlikosaurus, Allosaurus, and Tyrannosaurus (and in contrast them to crocodiles and birds)
  • Muscle tissues that open and shut jaws can solely stretch a lot earlier than tearing, which performs a task in what an animal can eat
  • Allosaurus and Tyrannosaurus may confide in 90 levels, whereas Erlikosaurus was solely about 45 levels
  • Trendy carnivores normally can open their jaws wider than herbivores
  • Lived alongside therizinosaur Segnosaurus, however have been area of interest partitioned
  • A lot smaller than Segnosaurus, which was 20 to 23 ft (6 to 7 m) lengthy
  • Segnosaurus had completely different enamel from Erlikosaurus
  • Erlikosaurus had symmetrical enamel, and Segnosaurus had complicated options, with serrations and reducing edges and will most likely eat harder vegetation
  • Erlikosaurus most likely used its beak and muscle groups in its neck to crop crops, and doubtless processed its meals in its intestine
  • Segnosaurus most likely processed its meals extra with its jaws and enamel
  • Lived in a semi-arid local weather, with lakes and rivers
  • Different animals that lived across the identical time and place included therizinosaurs, tyrannosaurs, ceratopsians, hadrosaurs, ornithomimosaurs, troodontids, pterosaurs, and fish

Enjoyable Reality:

Dinosaurs are essentially the most profitable terrestrial vertebrates of all time.

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