Episode 490: A brand new stegosaur posing as an ankylosaur

Episode 490: A brand new stegosaur posing as an ankylosaur. Thyreosaurus was a stegosaur, however wore its armor like an ankylosaur; A brand new iguanodontian, Hesperonyx, was named from Portugal; and dinosaur of the day Eotyrannus, a big early tyrannosauroid


  • A brand new stegosaur, Thyreosaurus atlasicus, had massive oval plates totally different than some other stegosaur supply
  • A brand new iguanodontian, Hesperonyx martinhotomasorum, was present in Portugal supply
  • Dinosaurs and concrete have rather a lot in frequent


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The dinosaur of the day: Eotyrannus

  • Tyrannosauroid theropod that lived within the Early Cretaceous in what’s now the Isle of Wight, United Kingdom (Wessex Formation)
  • Estimated to be as much as 15 ft (4.5 m) lengthy
  • Giant for an early tyrannosaur
  • Gracile
  • Had a protracted tail, walked on two legs
  • Had lengthy arms with three lengthy fingers (and claws)
  • Had slender fingers
  • Early reconstruction interpreted Eotyrannus has having for much longer arms
  • Had a vaguely rectangular snout, as Darren Naish put it
  • Had serrated tooth
  • Had thick, fused nasals and nasal had a whole lot of pneumatization (air-filled cavities)
  • Had lengthy shin bones and foot bones
  • A lot of the skeleton nonetheless not recognized
  • Fossils first present in 1995 by Gavin Leng
  • One of many first early recognized tyrannosaurs
  • Helps present that early tyrannosauroids had been gracile, with lengthy arms and three lengthy fingers on every hand
  • Fossils discovered at a cliffside publicity
  • Leng discovered a hand claw, then took it to Hutt, then curator on the Museum of Isle of Wight, who went to the location and excavated the remainder of the bones
  • Kind species is Eotyrannus lengi
  • Genus identify means “daybreak tyrant”
  • Genus identify refers back to the dinosaur being labeled as an early tyrannosaur
  • Described in 2001 by Stephen Hutt and others (together with Darren Naish, who in 2022 together with Andrea Cau printed a monograph of Eotyrannus)
  • Monograph based mostly on Naish’s PhD thesis
  • Species identify in honor of Leng
  • Some synonyms, which at the moment are nomen nudum, embody Fusinasus, Gavinosaurus, and Lengosaurus
  • Fossils discovered embody components of the cranium, vertebrae, components of the ribs, arms, legs, and pelvis from a subadult
  • Lack of fusion, means it’s most likely a subadult
  • Nevertheless, not thought to develop a lot greater than the estimated 4.5 m
  • Naish and Cau discovered the cranium doesn’t present longirostrine proportions, not like Megaraptor (doesn’t have a protracted jaw)
  • The not lengthy snout exhibits that tyrannosauroids “weren’t persistently and perpetually specialised for sturdy snouts optimised for highly effective biting throughout their historical past”
  • Second most full theropod from the Wessex Formation, after Neovenator
  • Theropods have been discovered within the space because the 1860s (a lot of them named from fragments)
  • Most of the Eotyrannus bones are damaged or fragmentary
  • Bones are embedded in arduous mudstone
  • Naish stated Eotyrannus was not a fairly fossil, and was troublesome to arrange (nonetheless extra work to do in getting ready)
  • Holotype was disarticulated earlier than fossilizing, so most of its skeleton was scattered
  • Makes it arduous to determine a lot of the fossil materials
  • Fossils present in a plant particles mattress
  • Two different skeletons discovered with it
  • Potential an animal drowned, and Eotyrannus was interested in the carcass, which could have been a battleground between a couple of theropods and resulted in deaths
  • Or Eotyrannus could have been partially scavenged earlier than it was buried
  • Or specimen could have been deposited within the plant particles mattress by a flood
  • Lived in a heat surroundings
  • Had moist and dry seasons
  • Different dinosaurs that lived across the identical time and place embody sauropods, ornithopods comparable to Iguanodon and Mantellisaurus, the carcharodontosaurian Neovenator, the spinosaurids Riparovenator and Ceratosuchops, the dromaeosaur Ornithodesmus, the compsognathid Aristosuchus and Calamosaurus, and different theropods
  • Different animals that lived across the identical time and place embody spiders, wasps, fish, amphibians, lizards, turtles, crocodiliforms, plesiosaurs, mammals, and pterosaurs

Enjoyable Truth:

Thyreosaurus is considered the primary stegosaur ever discovered with its plates flat in opposition to its physique reasonably than sticking up off its physique. This makes it similar to an ankylosaur, but it surely’s not the primary stegosaur to share stunning options with ankylosaurs.

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