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Episode 392: What makes a dinosaur a dinosaur?

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    Episode 392: What makes a dinosaur a dinosaur? How we differentiate dinosaurs from their closest family members 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 in all probability coated 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, presumably 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 steadiness
    • Fossils present in 1972 throughout a Soviet-Mongolian expedition, together with a nicely preserved cranium, almost full proper foot, and almost 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 lifeless”
    • 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 executed already, however spelled it as Erlicosaurus
    • Most scientists contemplate Erlikosaurus to be legitimate
    • First therizinosaur, then known as segnosaurs, the place a whole cranium was discovered, which helped paleontologists study extra about this group
    • Therizinosaurs, often called segnosaurs within the Nineteen Seventies, have been thought to not be dinosaurs. Then in 1970 Rozhdestvensky urged they have been theropods
    • In 1980, therizinosaurs have been considered sluggish 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 according to the concept therizinosaurs have been theropods
    • In 2010, Gregory Paul urged 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 numerous elements of the formation, the higher and decrease boundary, and the hip of Enigmosaurus regarded 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 tooth in its jaws
    • Might crop vegetation 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 interchange tooth to make the pinnacle lighter, and finally 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 developed to have extra structurally stronger jaws to eat harder meals (jaws acquired extra steady when biting, and fewer prone to have bone fractures)
    • Jaws grew to become stronger in carnivores and herbivores
    • Erlikosaurus had downward-bending jaws that would assist relieve stress when cropping vegetation
    • Had a comparatively weak chew drive in comparison with different theropods
    • In 2012, Stephan Lautenschlager discovered Erlikosaurus chew drive was low in comparison with different theropods and in relation to its physique mass
    • Nevertheless, Komodo dragons are inclined to have weak chew forces for his or her dimension
    • Keratinous beak was a bonus as a result of it’s all the time rising, so it may shortly 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 speak in confidence to 90 levels, whereas Erlikosaurus was solely about 45 levels
    • Fashionable 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 tooth from Erlikosaurus
    • Erlikosaurus had symmetrical tooth, and Segnosaurus had complicated options, with serrations and slicing edges and will in all probability eat harder vegetation
    • Erlikosaurus in all probability used its beak and muscle tissues in its neck to crop vegetation, and doubtless processed its meals in its intestine
    • Segnosaurus in all probability processed its meals extra with its jaws and tooth
    • Lived in a semi-arid local weather, with lakes and rivers
    • Different animals that lived across the similar time and place included therizinosaurs, tyrannosaurs, ceratopsians, hadrosaurs, ornithomimosaurs, troodontids, pterosaurs, and fish

    Enjoyable Truth:

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

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