Home Dinosaur Episode 485: New Species of Ankylosaur Was Likely Social While Young

Episode 485: New Species of Ankylosaur Was Likely Social While Young

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Episode 485: New Species of Ankylosaur Was Likely Social While Young

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Episode 485: New Species of Ankylosaur Was Likely Social While Young. New ankylosaur Datai yingliangis is already a contender for best ankylosaur of 2024; What’s up with how ankylosaurs ate their food? Also, connection challenge with orthodontic braces; And a deep dive into a new animal found to have osteoderms.

News:

  • New ankylosaur, Datai yingliangis, was described with a pair of horns at the back of its jaw source
  • Ankylosaurs were megaherbivores that evolved skulls and jaws to eat different foods from other herbivores source

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The dinosaur of the day: Avisaurus

  • Enantiornithine bird that lived in the Late Cretaceous in what is now Montana, U.S. (Hell Creek Formation)
  • Looked like a bird you’d see today, except it had teeth
  • Covered in feathers, had sharp claws on its feet, and a short tail, had a beak
  • Estimated to be up to 28 in (72 cm) long and weigh 11 lb (5.1 kg)
  • Type and only species is Avisaurus archibaldi
  • Genus name means “bird lizard”
  • Species name is in honor of J. David Archibald, who found the fossil
  • Fossils found in 1975
  • Holotype is just one lower leg bone, the tarsometatarsus
  • Holotype is the individual that a species name is based on
  • Has one of the largest tarsometatarsi known for enantiornithines, at about 2.9 in (almost 74 mm) long
  • Another fossil found, an incomplete coracoid (part of the shoulder) is larger than the holotype
  • Had inwardly curved claws, and was probably a predator
  • There was a second species that Varricchio and Chiappe named in 1995, called Avisaurus gloriae, found in the Two Medicine Formation. In 2018 Atterholt and others renamed it as its own genus, Gettyia
  • At first thought to be a non-avian theropod, when Brett-Surman and Paul described it in 1985, and then later Chiappe in 1992 redescribed it as an enantiornithine
  • Enantiornithes are extinct avialans, or birds
  • Lots of them, and lots of different types, lived in the Mesozoic
  • Went extinct at the end of the Cretaceous
  • First appeared about 131 mya, found in the Huajiying Formation in China
  • Enantiornithes have been found on all continents except Antarctica
  • Many of them found in the Jehol Group (about half of the species)
  • Not as many found in North America, and all the ones found in North America are from the Late Cretaceous
  • First probably enantiornithines fossils found in North America were three foot fragments found in Wyoming (Lance Formation), including an incomplete metatarsal III that may be from an Avisaurus archibaldi
  • Over 80 species have been named, but probably not all of them are valid (some named just from one bone)
  • Almost all enantiornithines had teeth and clawed fingers on their wings
  • But otherwise, they looked a lot like modern birds
  • Most Enantiornithes were small (sparrow sized) but there’s a lot of variability
  • Very diverse group, that includes waders, swimmers, insectivores, fishers, and raptors
  • First enantiornithine found was thought to be a modern bird: Gobipteryx. Thought to be a paleognath related to ostriches
  • First considered to be its own lineage in 1981 by Cyril Walker
  • Name Enantiornithes means “opposite birds”
  • Named because their shoulder bones have a socket joint between them that is the reverse, or opposite, of modern birds
  • Avisaurus is part of the family Avisauridae, which includes animals from South America, such as Soroavisaurus and Neuquenornis
  • Michael Brett-Surman and Gregory Paul named Avisauridae in 1985, but at the time thought they were small non-avian dinosaurs
  • Brett-Surman and Paul did think Avisaurus could be an enantiornithine
  • Brett-Surman and Paul in 1985 wrote: “In 1975, an expedition from the University of California (Berkeley) collecting in the Hell Creek Formation of Montana, recovered fragments of fossil bird bones associated with dinosaurian and other reptilian remains. This collection included a complete metatarsus that was called dinosaurian by neoornithologists but avian by most dinosaur paleontologists!”
  • At that point, a series of studies had found that birds were descendants of theropod dinosaurs, and as a result, scientists knew there were lots of similarities between the clades
  • Mentioned that this made it difficult in assigning isolated leg/foot bones to the proper group
  • Chiappe later assigned them to Aves, and Enantiornithes in 1992 based on some of their features being similar to Archaeopteryx and some Cretaceous birds
  • Avisauridae is a family of enantiornithine that lived in the Cretaceous
  • Known for features in their leg and foot bones, including parts being not completely fused
  • Largest and last of the enantiornithines, but not many fossils have been found
  • Mostly know them from their leg bones
  • Probably could perch in trees, and may have been arboreal

Fun Fact:

Osteoderms, “skin armor”, evolved over 20 times in large reptiles including animals like crocodiles and ankylosaurs, but there are also tiny “mice” today that have osteoderms.

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