DOI: 10.5061/dryad.8h067
title: Data from: New material and systematic re-evaluation of Medusaceratops lokii (Dinosauria: Ceratopsidae) from the Judith River Formation (Campanian, Montana)

description: Medusaceratops lokii is an enigmatic taxon of ceratopsid represented by
 partial parietals from the Mansfield bonebed in the Campanian Judith River
 Formation, Montana. Originally, all ceratopsid material collected from
 this bonebed was referred to the centrosaurine ceratopsid Albertaceratops,
 but subsequently two parietals were designated the types of the
 chasmosaurine, M. lokii, in part, because they were interpreted to have
 three epiparietals bilaterally. Here we describe new material from the
 bonebed that allows a systematic revision of the taxon. A revised
 reconstruction of the frill, informed by newly discovered parietals,
 reveals that M. lokii had a broad midline ramus and at least five
 epiparietals (ep) around the margin of the frill, both traits that are
 characteristic of Centrosaurinae. From medial to lateral, the epiparietal
 ornamentation consists of a small, variably procurving epiparietal (ep 1),
 an anterolaterally curving pachyostotic hook (ep 2), a smaller pachyostoic
 process (ep 3), and two small triangular epiparietals (ep 4 and 5). A
 phylogenetic analysis of ceratopsids, which is the first to include
 Medusaceratops, indicates that that M. lokii is a unique, early
 centrosaurine ceratopsid taxon that is more closely related to
 Centrosaurini and Pachyrhinosaurini than Nasutoceratopsini. No unequivocal
 chasmosaurine bones or diagnostic material from any other ceratopsid could
 be identified from the Mansfield bonebed, suggesting that it represents
 one of the oldest occurrences of a monodominant accumulation of a
 centrosaurine ceratopsid on record.
description: Text
 S1List of the Mansfield
 bonebed specimens used for character coding.TextS1_Chiba_etal.txtTable S1Specimen list of the Mansfield bonebed material housed in museum collections.TableS1_Chiba_etal_Revised.csvTable S2Compiled postorbital horncore measurements of Centrosaurinae, non-Triceratopsini Chasmosaurinae, and Triceratopsini.TableS2_Chiba_etal_Revised.csvTable S3Compiled humerus and tibia circumference measurements of ceratopsids from Belly River Group and Judith River Formation (Campanian).TableS3_Chiba_etal_Revised.csvSupplemental data 1Data matrix used in phylogenetic analysis in this study (TNT file).SuppDat_Chiba_etal_Revised.tntSupplemental data 23D data of a Medusaceratops parietal (ROM 73832, STL file). The model is scaled in meters.ROM73832_M.lokii_Parietal.stlSupplemental data 33D data of a Medusaceratops parietal (ROM 73837, STL file). The model is scaled in meters.ROM73837_M.lokii_Parietal.stlSupplemental data 43D data of a Medusaceratops postorbital (TMP 2002.069.0010, STL file). The model is scaled in meters.TMP2002.69.10_Medusaceratops_PostorbitalR.stlSupplemental data 53D data of a Medusaceratops postorbital (ROM 73834, STL file). The model is scaled in meters.ROM73834_Medusaceratops_Postorbital.stlSupplemental data 63D data of a Medusaceratops postorbital (ROM 73831, STL file). The model is scaled in meters.ROM73831_M.lokii_Supraorbital.stlSupplemental data 73D data of a Medusaceratops postorbital (WDC-DJR-003, STL file). The model is scaled in meters.12-1CA 2_Merged.stlSupplemental data 8Thin section photograph of mid diaphyseal cross-section of a Medusaceratops tibia (ROM 67873) with plane polarized light (JPG file).ROM67873_TS710_Medusaceratops_TibiaL_x2.jpgSupplemental data 9Thin section photograph of mid diaphyseal cross-section of a Medusaceratops tibia (ROM 67873) with cross polarized light (JPG file).ROM67873_TS710_Medusaceratops_TibiaL_x2_cr.jpg