Medusaceratops

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Medusaceratops
Temporal range: Middle
Ma
↓
Skeleton at Wyoming Dinosaur Museum formerly referred to Albertaceratops
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: †Ornithischia
Clade: †Ceratopsia
Family: †Ceratopsidae
Subfamily: †Centrosaurinae
Genus: †Medusaceratops
Ryan, Russell & Hartman, 2010
Species:
†M. lokii
Binomial name
†Medusaceratops lokii
Ryan, Russell & Hartman, 2010

Medusaceratops is an

extinct genus of centrosaurine ceratopsian dinosaur known from the Late Cretaceous Judith River Formation (middle Campanian stage) of Montana, northern United States. It contains a single species, Medusaceratops lokii.[1]

Discovery

Side view of skeleton

The known material of Medusaceratops came from a bonebed in the badlands on the west side of

Ceratops montanus from a nearby area, however, could not refer the bonebed material to any valid existing taxon. The bonebed, known as the Mansfield Bonebed honoring its landowner, is located on private land and historically has been excavated by several commercial companies. The type material of Medusaceratops and other specimens were excavated more recently and have been purchased by the Wyoming Dinosaur Center from Canada Fossils, Ltd., of Calgary, Alberta. Additional material from the same excavation was purchased and accessioned by the Royal Tyrrell Museum of Palaeontology. Canada Fossils, Ltd., also assembled two composite skeletons using the Mansfield Bonebed material which are in the collections of the Wyoming Dinosaur Center and the Fukui Prefectural Dinosaur Museum, however neither of the casts has an exact reconstruction of Medusaceratops as it was later described.[1]

The name Medusaceratops was coined by

generic name refers to Medusa, a monster from Greek mythology whose "hair" consists of snakes and its gaze could turn men to stone, alluding to a unique trait of this genus - the large, thick snake-like spikes that extend to the sides of the frill, in combination with Latinized Greek ceratops, meaning "horned-face", which is a common suffix for ceratopsian genera names. The specific name lokii honors Loki, a troublemaking god in the Norse mythology, in reference to the years confusion that surrounded the taxonomic designations of the Mansfield Bonebed material before it was given its own name.[1]

The Mansfield Bonebed material was collected from the upper part of the

chasmosaurine,[1] until the naming of Judiceratops by Longrich (2013), also from the Judith River Formation, but from an area equivalent to the lower Oldman Formation or upper Foremost Formation.[2]

However, Ryan had already indicated that part of the Mansfield material represented not a chasmosaurine, but a centrosaurine. Chiba et al. in 2017 described new material of Medusaceratops from the Mansfield Bonebed, found in 2011 and 2012 by David Trexler, indicating the presence of traits that were characteristic of Centrosaurinae in the skeleton of M. lokii. They concluded that all the material could be referred to a single species. The phylogenetic analysis conducted by the authors indicated that Medusaceratops was not a member of Chasmosaurinae after all, but rather an early centrosaurine ceratopsid that was more closely related to

Nasutoceratopsini.[3]

Description

Restoration

Two partial parietals (frills) that are housed at the Wyoming Dinosaur Center were chosen as the type material of Medusaceratops, including the

chasmosaurine material from the Mansfield Bonebed was thought to be referable to Medusaceratops, which totals at several hundred individual elements, upon its original description only these two partial frills have been scientifically described while the rest of the material was being reexamined. Many of the other elements are not diagnosable to a genus level and can only be confidently referable to Ceratopsidae.[1][3]

Upon its original description Medusaceratops was thought to represent a

centrosaurines.[1]

This was challenged in 2018, by the description of additional Mansfield Bonebed material assignable to Medusaceratops. It became apparent that the 1-3 frill spikes mentioned above are in fact spikes 2–4. The first epiparietal is small and variably procurving and thus was misinterpreted before. At least one more epiparietal pair was also identified (after the fourth), resulting in a total of at least 5 pairs, consistent with centrosaurines like Albertaceratops and Wendiceratops, but not with chasmosaurines. The midline ramus of Medusaceratops, a bone separating the two sides of the frill, was also among the newly described material. It is broad, resulting in rounder and smaller frill fenestrae (holes) like in other centrosaurines. Thus, the new study reassigned Medusaceratops to Centrosaurinae, among which it is most similar to Albertaceratops and Wendiceratops.[3]

In 2010, a length of roughly 6 meters (~20 feet) was estimated for Medusaceratops lokii.[4]

Classification

Reconstruction of parietals of various centrosaurines, including Wendiceratops (A) showing 5 epiparietal pairs and broad midline ramus. Medusaceratops itself is marked by letter (F).

Among valid

ceratopsids from the Judith River Formation, Medusaceratops can be directly distinguished from centrosaurine Avaceratops,[3] and chasmosaurines Judiceratops and Spiclypeus[5] based on its unique frill ornamentation. It differs from chasmosaurine Mercuriceratops based on its less unique squamosal bone,[6] as evident from newly described squamosal bones of Medusaceratops.[3] All material previously assigned to the centrosaurine Albertaceratops from the formation is now assigned to Medusaceratops or considered too fragmentary.[1][3]

The cladogram presented below follows a phylogenetic analysis by Chiba et al. (2017) who redescribed Medusaceratops as a centrosaurine:[3]

Centrosaurinae

Diabloceratops eatoni

Machairoceratops cronusi

Nasutoceratopsini

Avaceratops lammersi
(ANSP 15800)

MOR 692

CMN 8804

Nasutoceratops titusi

Malta new taxon

Xenoceratops foremostensis

Sinoceratops zhuchengensis

Wendiceratops pinhornensis

Albertaceratops nesmoi

Medusaceratops lokii

Eucentrosaura

Centrosaurini

Pachyrhinosaurini

See also

References

  1. ^
    ISBN 0-253-35358-0
    .
  2. S2CID 129801786
    .
  3. ^
    S2CID 134031275
    .
  4. ^ Cleveland Museum of Natural History (30 May 2010). "New horned dinosaur: Two-ton plant-eater lived 78 million years ago in Montana". ScienceDaily. ScienceDaily. Retrieved 24 January 2022.
  5. PMID 27191389
    .
  6. S2CID 13957187
    .
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