Medusaceratops vs Carcharodontosaurus

"A NEW CHASMOSAURINE CERATOPSID, Medusaceratops
lokii, is described based on material collected from a
bonebed in the Judith River Formation (Campanian)
near Havre, Montana. Originally, all ceratopsid material
from the bonebed was referred to the basal centrosaurine
Albertaceratops Ryan 2007, the holotype of which was
collected from the Oldman Formation of Alberta, Can-
ada. Reassessment of several key features of parietals
from the Montanan bonebed, including the number and
shape of the preserved epiparietals, necessitates referral
of at least some material from this site to the new taxon.
Although the bonebed does include centrosaurine ele-
ments (including a lateral parietal ramus and a squam-
osal) that may eventually be referable to Albertaceratops,
it appears to be dominated by elements of chas-
mosaurine affinity. In addition to being the first un-
equivocal occurrence of a Campanian-aged
chasmosaurine ceratopsid in Montana, Medusaceratops
lokii is also the oldest known Chasmosaurine ceratopsid
(approximately 77.5 Ma).

Introduction

Until the early 2000s, Ceratopsidae was limited to 13 named
genera in two clades ("subfamilies"), Centrosaurinae and
Chasmosaurinae (Ryan and Russell 2001)."