Episode 443: Dinosaurs on Islands. Featuring Prehistoric Planet 2

Episode 443: Dinosaurs on Islands. Featuring Prehistoric Planet 2. What caused sea level to rise in the Cretaceous and turned Europe into a series of islands? Would Hatzegopteryx be a threat to humans? Which islands did the Prehistoric Planet crew film on? We’ll answer all those questions and more!


The dinosaur of the day: Morrosaurus

  • Ornithopod iguanodont that lived in the Late Cretaceous in what is now Antarctica, at James Ross Island
  • Looked somewhat like Iguanodon, but smaller, with longer legs
  • Considered to be medium-sized
  • Estimated to be up to 13 ft (4 m) long
  • Probably was a fast runner
  • Type and only species is Morrosaurus antarcticus
  • Fossils were found in 2002 by Fernando Novas, who found a partial skeleton in the Snow Hill Island Formation
  • Named and described in 2016 by Sebastian Rozadilla and others
  • Genus name means “El Morro lizard”
  • Genus name refers to El Morro on James Ross Island, where the fossils were found
  • Species name refers to Antarctica
  • Holotype is part of the right hind leg and part of the foot
  • Holotype is at the Museo Argentino of Ciencias Naturales
  • Rozadilla and others wrote: “The Cretaceous fossil record of non-avian dinosaurs in Antarctica is strongly patchy and biased”
  • Holotype was found about 98 ft (30 m) below a theropod
  • Fossils found associated with plesiosaur bones and lots of marine invertebrates
  • In 2019, Matthew Lamanna and others described more Morrosaurus material, including more of the foot and associated but unidentified fragments
  • The foot material probably belonged to the holotype of Morrosaurus, based on where it was found and that part of the foot was missing with the holotype
  • Also mentioned some sort of ornithopod skeleton found near where the Morrosaurus holotype was found. Could be Morrosaurus, but no overlapping bones to compare (ornithopod skeleton doesn’t have the hind limb), so can’t know for sure
  • Closely related to Trinisaura, the only other named ornithopod found in Antarctica
  • Morrosaurus had a stouter femur and tibia (leg bones), compared to Trinisaura, which was gracile
  • Bigger than Trinisaura
  • In 2020, Jordi Garcia-Marsa and others did histology on Morrosaurus and Trinisaura
  • Found the holotype of Morrosaurus was a sexually mature subadult
  • Found the growth pattern of Morrosaurus and Trinisaura was similar to Gasparinisaura and Australian ornithopods
  • Found Morrosaurus could grow fast, but it happened periodically, not continuously
  • Growth slowed down as it got older
  • Past histological studies found that Triassic and Jurassic archosaurs grew in cycles and grew quickly when they were young, which means this is a plesiomorphic feature (ancestral) for archosauriforms, which would have made it possible for dinosaurs to live in extreme environments without needing important physiological changes
  • Part of the group Elasmaria, which are known for running fast
  • Elasmaria includes dinosaurs from what is now Patagonia, Antarctica, and Australia, which shows they had similar types of animals
  • Land connection between Patagonia and Antarctica means there were some shared animals and plants
  • Seems that dinosaurs from the James Ross Basin are similar to the dinosaurs found in southern South America
  • Similar to lots of Patagonian animals, such as Gasparinisaura, an ornithopod that lived in the Late Cretaceous in what is now Patagonia
  • Lived in a seasonal climate, with winters getting down to almost -30° Celsius
  • Could get lots of rainfall, and lots of humidity

Fun Fact:

There are a lot of types of islands, but Continental islands are the best places to find dinosaurs.

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