Episode 355 is all about Arrhinoceratops, a ceratopsian which looks a lot like a miniature Torosaurus (or Triceratops).

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In this episode, we discuss:

News:

• A new abelisaurid, Kurupi itaata, was named from Brazil—the first theropod named from Sao Paulo state source
• An allosauroid from Uzbekistan, Ulughbegsaurus, was the apex predator over dromaeosaurids and the tyrannosaur Timurlengia source
• Three types of dinosaur footprints were recently found in the Thar desert of Rajasthan, India source
• Dinny the dinosaur, the Brontosaurus statue at the Calgary Zoo, has been restored source
• Two men in Massachusetts were arrested after being caught allegedly trying to steal dinosaur footprints source
• Another fun list of dinosaur sites includes a sculpture garden in San Diego, CA source
• Moon Girl and Devil Dinosaur is coming back as an animated series on Disney in February 2022 source

The dinosaur of the day: Arrhinoceratops

• Chasmosaurine ceratopsian that lived in the Late Cretaceous in what is now Alberta, Canada (Horseshoe Canyon Formation)
• Probably looked a lot like Triceratops, but a different frill, and smaller
• Based on the skull, estimated to be about 15 ft (4.5 m) long and weigh 2,900 lb (1.3 tonnes)
• Had a broad, square neck frill with two fenestrae (openings)
• Had deep grooves along the neck frill
• Sides of the frill had about nine ossifications
• Left squamosal on the frill side has an opening from a pathology, maybe from a wound
• Some scalloping around the frill
• Had long brow horns and a short, blunt nose horn
• Horns turn outward
• Snout was short and high
• Had dental batteries
• Probably ate ferns, cycads, and conifers
• Described in 1925 by William Parks
• Holotype is a partially crushed, somewhat distorted skull without the lower jaws, found along the Red Deer River on Neill’s Ranch site during a 1923 expedition from the University of Toronto
• Type species is Arrhinoceratops brachyops
• Genus name means “no nose horn face”
• Species name means “short faced”
• Only the skull is known
• Parks wrote, “The nasal horn core is apparently absent, but the nasal bone is sharp above and somewhat rugose, suggesting that it may have carried a horny sheath.” Also said the nasal bone rose abruptly, but had no trace of a horn core and that there was no sign on the surface of the bone that the structure had been lost (too smooth)
• Later studies of Arrhinoceratops found Parks had made some mistakes in his original description
• In 1933 Richard Swann Lull wrote a revision of Ceratopsia. Lull said there was more evidence of a nasal horn on Arrhinoceratops than in the type specimen of Triceratops obtusus (“Hatcher” at the Smithsonian)
• Lull also said it was strange Arrhinoceratops was so rare when hundreds of Triceratops had been found
• More fossils in Utah found in the 1930s, that were posthumously named Arrhinoceratops? utahensis in 1946 by Charles Whitney Gilmore
• Gilmore wasn’t sure it was Arrhinoceratops, because at the time there were fossils from up to 11 individuals of an undescribed ceratopsian, and they were all fragmentary so it was hard to tell what they should be assigned to
• Gilmore had died the year before the publication, so a colleague probably finished it
• Douglas Lawson reclassified it as Torosaurus utahensis in 1976 (said it was different from Torosaurus latus because Torosaurus latus had a proportionally shorter squamosal bone)
• In 2011 Helen Tyson said only the type specimen could be considered for sure to be Arrhinoceratops brachyops
• Also said Arrhinoceratops did have a nasal core
• And said that Torosaurus is the closest relative of Arrhinoceratops
• In 2014, more Arrhinoceratops fossils found
• Took two years to excavate, and found babies and adults, so maybe they traveled in herds or families
• Found a bone bed with five specimens
• Before, only known from two skulls
• Fossils found in 2010 by Frank Hadfield, who has been described as a dinosaur enthusiast. He noticed lower jaws and a horn core
• Over 3,000 pounds of fossils. Used helicopters to airlift some
• Prepared at the Royal Tyrrell Museum
• Not clear how the group died, but could be from a flood
• The find included skull bones, parts of the arms, and hip bones
• In 2014 Jordan Mallon and others published on new information about Arrhinoceratops
• Described a second specimen, with a relatively complete skull, vertebrae, and partial left forelimb
• Had a triangular nasal horncore
• In 2015, Jordan Mallon and others published on the skull ontogeny of Arrhinoceratops
• Described the partial skull of a juvenile chasmosaurine attributed to Arrhinoceratops, and looked at more mature specimens to understand the ontogeny
• Found that as Arrhinoceratops matured, the horncores got longer and shifted more to a forward inclination, the frill epiossifications became lower and fused to the underlying frill, and the face got longer
• Also the scalloping around the frill margins got smaller as it aged
• In 2013, Canada’s Museum of Nature in Ottawa had a “Dino Idol” contest, where visitors to the museum voted between five dinosaurs (whose fossils were still in jackets). The winner got prepared
• Had five options, all with nicknames: “Headrosaur” (the skull of a hadrosaur), “Mystery Jaw” (jaw of a carnivore like Gorgosaurus or Daspletosaurus), “Stumpy” (the skull of a ceratopsid, maybe Arrhinoceratops), “Regal Ed” (partial skeleton of an Edmontosaurus, whose head had already been prepared), and “Canadian Club” (the back half of an ankylosaur
• “Canadian Club” won (had been wrapped up for 100 years). All five contestants had been collected in the 1910s and 1920s by Charles Sternberg and his three sons
• Lived a few million years before Triceratops
• Other dinosaurs that lived around the same time and place included Anchiceratops, Albertosaurus, Hypacrosaurus, Saurolophus, Parksosaurus, Ornithomimus, Struthiomimus

Fun Fact: Ecosystems usually have many mesopredators, but just one apex predator. However, they sometimes switch roles.

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