Episode 460: Were dinosaurs smarter than mammals?



Episode 460: Were dinosaurs smarter than mammals? New research into early dinosaur social skills suggest they were (at least at one point in history). Plus: The first good evidence of sexual dimorphism in dinosaurs; and Maz Maddox joins to discuss her RELIC series, about humans who can shape shift into dinosaurs.


  • Dinosaurs learned an advanced social skill called visual perspective taking at least 60 million years before mammals source
  • Another group of researchers found sexual dimorphism in dinosaurs, but this time they used more than just size or ornamentation. source


Maz Maddox, a fellow dinosaur enthusiast and author of the RELIC series, about humans who can shape shift into dinosaurs. Follow her on Instagram and Facebook @mazmaddox

The dinosaur of the day: Wannanosaurus

  • Basal pachycephalosaur that lived in the Late Cretaceous in what is now Anhui, China (Xiaoyan Formation)
  • Small, walked on two legs, had a long tail, had a long, thick but flat skull, and has been depicted with bristles on its back
  • Had small, densely packed bony bits on the back of the head
  • Had short arms, with the humerus (arm bone) half the length of the femur (leg bone)
  • Holotype was small, with a femur about 3.1 in (8 cm) long
  • Estimated to be about 2 ft (60 cm) long
  • As a pachycephalosaur, probably was herbivore or omnivorous, eating plants and maybe insects
  • Described in 1977 by Hou Lian-Hai
  • Type species is Wannanosaurus yansiensis
  • Genus name means “Wannan lizard” and refers to where the fossils were discovered
  • Wannan refers to the southern part of Anhui province, and is an alternative name for Anhui
  • Species name refers to Yansi, the town near where the fossils were found
  • Fossils found in 1970 by the Anwei Provincial Survey
  • Found two individuals, including part of the skull roof and lower jaw, leg bones, parts of the arm, vertebrae
  • Paper describing Wannanosaurus made lots of comparisons with the pachycephalosaur Stegoceras
  • But also said it most closely resembles Yaverlandia (at the time thought to be a pachycephalosaur, now thought to be a maniraptoran theropod) and Homalocephale
  • In 2009, Richard Butler and Qi Zhao re-examined Wannanosaurus
  • When they studied Wannanosaurus, noted that some of the material from the holotype and paratype were missing, so the authors based observations based on Hou’s figures and description
  • However, Hou made some mistakes, as Butler and Zhao pointed out. For example, Hou identified the humerus as from the left side, but it was on the right (measurements were the same, being less than 50% the length of the femur)
  • Found that some bones in the skull weren’t fused, so the holotype was probably a juvenile or subadult
  • But no histology done on it yet, so not 100% sure
  • Authors classified Wannanosaurus in Pachycephalosauria but said since the fossils are from juveniles it complicates where to place it phylogenetically
  • Controversy on where it sits in the pacycephalosaur phylogenetic tree
  • In the past has been classified as a Homalocephalidae (family no longer used but grouped together pachycephalosaurs without domed skulls)
  • Had a flat skull with large openings, so thought to be basal in the Pachycephalosauria clade
  • Pachycephalosaurs are known for the thick skull roof
  • Most recent studies say it’s part of Pachycephalosauria, but not pachycephalosauridae

Fun Fact:

Many animals don’t have any sexual size dimorphism(SSD) at all. For example, 39% of mammals have no SSD (meaning the males and females are the same size).

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