Episode 302 is all about Monoclonius, a relative of Styracosaurus with a large nasal horn—sometimes considered synonymous with Centrosaurus.
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In this episode, we discuss:
News:
- “The first 3D preserved embryonic skull of a sauropod” was described and includes a horn on its upper lip source
- In Wales, there are footprints with “squelch marks” that may be dinosaur footprints. source
- A graphics student sculpted a Velociraptor that will be on permanent display at Radford University Museum of the Earth Sciences source
- The Witte Museum in San Antonio, Texas will soon be a state and federal fossil repository source
- You can now get four new Jurassic World: Camp Cretaceous dinosaurs in happy meals source
- Jurassic World: Dominion will include “a surprising faction of prehistoric creatures that you’ve never seen before” source
The dinosaur of the day: Monoclonius
- Ceratopsian that lived in the Late Cretaceous in what is now Montana, US (Judith River Formation), and Alberta, Canada (Dinosaur Park Formation)
- Dubious genus, maybe, and a Bone Wars dinosaur
- Lots of confusion/debate around Monoclonius and Centrosaurus
- Named in 1876 by Edward Drinker Cope
- Found fossils with Charles Sternberg in 1876 in Chouteau County Montana, about 100 mi (150 km) from the site of Battle of the Little Bighorn, which happened that June. Found in different locations, and found most elements (only the feet were missing completely), including the base of the nasal horn, part of the skull frill, brow horns, vertebrae, sacrum, shoulder girdle, thighbones, shinbone, fibula, parts of the forelimb, and more
- Cope described and named his find two weeks after leaving Montana, October 1876
- Ceratopsians were not yet a distinct group, so Cope didn’t know much about the fossils found (like the nasal horn, brown horns, he thought the frill was part of the breastbone)
- Cope thought Monoclonius was a hadrosaur
- After Marsh described Triceratops in 1889, Cope looked at Monoclonius and determined that Triceratops, Monoclonius, and Agathaumas were are a similar group of dinosaurs. (Cope also named Agathaumas and Polyonax)
- Cope wrote in 1889, The Horned Dinosauria of the Laramie” about one of the most complete skeletons in his collection, Monoclonius crassus. Some evidence of the Bone Wars: “This family is called by Marsh the Ceratopsidae; but as it is not certain that Ceratops, Marsh, is distinct from one of the genera previously named, I shall call it the Agathaumantidae, from the longest known genus, Agathaumas.”
- He redescribed Monoclonius as having a large nasal horn, two brow horns over the eyes, and a large frill, and then he named three more Monoclonius species: Monoclonius recurvicornis (“with a recurved horn”, based on a specimen with a short, curved nasal horncore), Monoclonius sphenocerus (“wedge-horned” based on a specimen Sternberg found in 1876 on Cow Island in Missouri that had a long nasal horn), and Monoclonius fissus (“the split one” based on a specimen that Cope thought had a split squamosal, but turned out the squamosal was a pterygoid, or jaw bone)
- Cope wrote that Monoclonius sphenocerus has many skeletal parts, including parts of the skull, found by Charles H. Stenberg in 1876 on the Missouri River, near Cow Island. “The Monoclonius sphenocerus is an animal of large size, exceeding the rhinoceros in height, and the nasal horn is the most formidable weapon I have observed in a reptile”
- Monoclonius used to have many species assigned to it (16?), and now there’s only one (and it’s dubious). The others have been reassigned (Chasmosaurus, Eoceratops, etc.)
- After Cope and Marsh died, John Bell Hatcher worked on finishing Cope’s Ceratopsia monograph. He didn’t like Cope’s methods, and found that the type specimen of Monoclonius crassus was a composite and therefore a bunch of syntypes, so he chose one as a lectotype
- Charles H. Sternberg found more specimens, and Lawrence Lambe found Centrosaurus to be distinct from Monoclonius. Then Barnum Brown in 1914 found there was only one valid species that Cope named (there were other species named by other scientists): Monoclonius crassus, and then he compared Monoclonius with Centrosaurus and found the two were synonymous. Then he named another species, Monoclonius flexus (“the curved one”) based on a skull found in 1912 with a forward curving nasal horn. Lawrence Lambe responded in 1915 saying Monoclonius dawsoni was Brachyceratops, Monoclonius sphenocerus was Styracosaurus, and Monoclonius crassus was not distinct enough (lectotype was too damaged and had no nasal horn), and he referred Brown’s Monoclonius flexus to Centrosaurus apertus. In 1917 Brown named Monoclonius nasicornus (“with the nose horn”) and Monoclonius cutleri, based on a skeleton with skin impressions but no skull
- Lots of debate, then Richard Swan Lull published “Revision of the Ceratopsia” in 1933, where he said Centrosaurus was a junior synonym of Monoclonius but still its own species (Monoclonius apertus instead of Centrosaurus apertus). Charles M. Sternberg (Charles H. Sternberg’s son) said in 1938 there were Monoclonius-types in Alberta. In 1940 he named Monoclonius lowei, in honor of his field assistant Harold D’acre Robinson Lowe who worked with him during six field seasons
- Charles M. Sternberg wrote about Monoclonius in 1938, about how Monoclonius was distinct from Centrosaurus because of the shape and proportion of its horn cores. Brown thought Centrosaurus was a synonym of Monoclonius. He wrote, “While collecting vertebrate fossils from the uppermost strate of the Belly River series in the southeastern corner of Alberta last summer, my ambition of twenty years was realized in the discovery of two skulls which can be identified as Monoclonius.”
- By the 1990s there were three theories: 1) Monoclonius crassus was valid and the same as Centrosaurus apertus, a junior synonym; 2) Monoclonius crassus was a nomen dubium and other Monoclonius species should be referred to other genera; 3) Monoclonius and Centrosaurus were both valid, separate taxon
- Peter Dodson in 1990 found that Monoclonius and Centrosaurus were both valid taxon. But in 1997 Scott Sampson and others found that the Monoclonius crassus lectotype and referred specimens were nomina dubia because they were all juveniles or subadults and that most centrosaurines had a “Monoclonius” phase while growing, which is why the specimens were found in many places and lived at many times
- Peter Dodson and Allison Tumarkin in 1998 said that the bone structure could be because of pedomorphosis (adults keeping juvenile traits), based on the holotype of Monoclonius lowei having an interparietal bone that was 609 mm long and the longest of any known centrosaurine (second longest one was from an adult specimen, showing Monoclonius lowei was probably not a subadult)
- In 2006, Michael Ryan found that the holotype of Monoclonius lowei was a large subadult, because an osteoderm on the edge of the frill was starting to develop and there were skull sutures not closed
- Charles M. Sternberg had named Monoclonius lowei in 1940, based on a large, somewhat flattened skull that had a small, backward curved nasal horn (found in Dinosaur Park Formation)
- Ryan suggested Monoclonius lowei could be a subadult of Styracosaurus, Achelousaurus, or Einiosaurus
- Peter Dodson said Monoclonius lowei is “almost certainly a diagnosable species”
- Type species is Monoclonius crassus
- Genus name means “single sprout”
- Genus name refers to the way its teeth grew compared to dinosaur Diclonius, which means “double sprout”, that Cope named in the same paper where he named Monoclonius. Cope said that Diclonius had two sets of teeth at a time (one in use and one replacement set ready to go) and Monoclonius only had one set of teeth at a time, and grew replacement teeth after a tooth had fallen out). The tooth he described has been lost, and based on that description, probably was the tooth of a hadrosaur, not a ceratopsian/centrosaurine
- Species name means “the fat one”
- Herbivorous
- Can see Monoclonius in Phil Tippett’s Prehistoric Beast
Fun Fact: Animals with one horn are sometimes described as monocerotic from the Greek Mono (one) and ceros (horn). The Latin version of one horn is Unicornu (anglicized to Unicorn).
