The Big Dinosaur Podcast

Episode 240 is all about Hylaeosaurus, an ankylosaur that was one of the first three named dinosaurs.

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In this episode, we discuss:

News:

• Researchers questioned dinosaur soft tissue discoveries after finding microorganisms living on a Centrosaurus fossil source
• A pair of massive Macroelongatoolithus eggs were described from Southeastern Idaho source
• In Zimbabwe, a team of researchers found a 97% complete dinosaur skeleton source
• Potential evidence of T. rex living in groups was teased in Utah source
• The Mukawa dinosaur will be on display at the 2019 Dinosaur Expo source
• The new ceratopsian from Colorado has been declared an “adult Triceratops” source
• The Boston Globe made a list of stops in New England where you can see dinosaur tracks source
• Downtown Drumheller, Alberta, Canada has a new dinosaur mural source

The dinosaur of the day: Hylaeosaurus

• Ankylosaur that lived in the Early Cretaceous in what is now England
• Part of the three original dinosaurs that Richard Owen based Dinosauria on in 1842 (covered the other two, Iguanodon in episode 87 and Megalosaurus in episode 47)
• One of the first dinosaurs discovered
• Gideon Mantell discovered Hylaeosaurus in 1832
• Only a few fossils have been found, so not much is known
• Holotype includes the rear of the skull, vertebrae, and some spikes and armored plates
• Other fossils may be referred to Hylaeosaurus from the Isle of Wight, France, Spain, Germany, and Romania, but many are considered dubious or could belong to Polacanthus
• May have been a basal nodosaurid or a basal ankylosaurid
• Often depicted as a typical nodosaur, with rows of plates on the back and tail and a long head, with a beak to crop vegetation
• Shoulder spines curve back and are long, flattened, narrow, and pointed
• Had at least three long spines on its shoulder, and had body armor
• Estimated to be up to 20 ft or 6 m long (Gregory Paul estimated it to be about 16 ft or 5 m long and weigh 2 tonnes)
• Darren Naish estimated it to be between 9.8 to 13.1 ft (3 to 4 m) long
• Mantell had thought it was 25 ft (7.6 m) long, about half the size of Iguanodon and Megalosaurus, and he thought it was like a modern lizard
• Type species is Hylaeosaurus armatus
• Genus name means “belonging to the forest lizard” or “of the wood lizard”
• Named after the Tilgate Forest where it was found. Later Mantell said it mean “Wealden lizard”, another word for forest, to refer to the Wealden Group, the formation where it was found
• Species name means “armed” or “armored” and refers to the spikes and plates
• First fossils found in West Sussex
• Gideon Mantell wrote to Professor Benjamin Silliman in July 1832 after there was a gunpowder explosion that led to exposing some fossils in boulders. A local fossil dealer put together about 50 pieces and sold them to Mantell (more bones than had been found of Megalosaurus and Iguanodon at the time)
• Hylaeosaurus was the most complete dinosaur skeleton found at the time
• Original specimen is now part of the Natural History Museum of London
• At first Mantell thought it was Iguanodon but William Clift, curator of the Royal College of Surgeons of England museum, noticed it had body armor (plates and spikes). Mantell decided to name the specimen Hylaeosaurus
• Mantell sent Hylaeosaurus to the Geological Society of London, and met with Richard Owen, who told him the paper he’d written about Hylaeosaurus was too long. Mantell’s friend Charles Lyell told him to write a book about the fossils he’d found and write a chapter on Hylaeosaurus. He wrote it in three weeks
• Mantell’s book, The Geology of the South-East of England, was published 1833
• There were four species, but only the type species is still considered to be valid
• Other species included Hylaeosaurus oweni (Mantell named it to honor Richard Owen, but now considered to be a junior synonym of Hylaeosaurus armatus), Hylaeosaurus northhamptoni (originally named Regnosaurus but renamed in 1956 by Alfred Romer), and Hylaeosaurus foxii (originally Polacanthus but renamed in 1971 by Walter Coombs), though neither Hylaeosaurus northmaptoni or Hylaeosaurus foxii have been accepted
• Can see Hylaeosaurus at Crystal Palace Dinosaur (we made a video when we visited https://youtu.be/w7G6ID3Prbc)
• Mark Witton wrote a detailed post about the science behind the Crystal Palace Dinosaurs. He said Benjamin Waterhouse Hawkins didn’t always follow Richard Owen’s ideas on what the dinosaurs should look like, and in some cases made them look more like Mantell’s descriptions
• Hawkins also put spines in a single row along the midline, with lots of small scutes on either side (he went with Mantell’s vision instead of Owen’s, with the single row)
• Owen in 1841 thought the spines were actually ribs (gastralia), because they were asymmetrical, but by 1854 he thought they were spines and later thought there were two rows of spines
• In 1841, Mantell wrote Memoir on a Portion of the Lower Jaw of the Iguanodon, and on the Remains of the Hyloeosaurus and Other Saurians, Discovered in the Strata of Tilgate Forest, in Sussex by Gideon Mantell
• He describes in great detail his find of Hyalaeosaurus, and how many of the fossils were destroyed by workmen (on accident), but that there was still strong evidence of it being a new genus. He also describes the referred specimens (now not considered to be Hyaleosaurus), and includes some sketches
• Mantell wrote he presented everything to Richard Owen, and though he’s worked with artist M. Dinkel, they were not able to complete recreating Hylaeosaurus, but he said he did not regret not finishing the project because “the subject will be elucidated by one far more competent to do it justice”
• Mantell also wrote, ” Removed from the field of my former labours, having disposed of my collection, the fruit of twenty-five years assiduous research, and being engaged in the duties of an arduous profession, this memoir is, in all probability, the last contribution which it will ever be in my power to offer in this interesting department of paleontology. I therefore conclude these remarks in the spirit and in the language of the illustrious philosopher, whose splendid discoveries and eloquent writings first drew my attention to this branch of natural science, and whose kind and generous assistance so often encouraged me to persevere in my investigations:-.” (wrote in French, translates to) “I end here my work, and I leave it to my successors to cultivate a field which I have only opened, and which certainly will give them still richer harvests than all those that I was able to collect *”

Fun Fact: If Gigantoraptor laid a full clutch of the Macrooelongatoolithus eggs that we discussed in the episode, it would lose about 300 pounds.