The morphology and systematics of<i>Avaceratops</i>, a primitive horned dinosaur from the Judith River Formation (Late Campanian) of Montana, with the description of a second skull

Penkalski, Paul; Dodson, Peter

doi:10.1080/02724634.1999.10011182

Cited by 28 publications

(42 citation statements)

References 20 publications

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“…ventrally displaced maxillary toothrow, elongate supraorbital horncores, pronounced epijugals) otherwise absent in all other late Campanian centrosaurines. Phylogenetic analysis (figure 2; see also the electronic supplementary material for character definitions, matrix and expanded summary of results) places Nasutoceratops as the sister taxon of Avaceratops from the Judith River Formation of Montana [21,28]. Together, Nasutoceratops and Avaceratops form a previously unrecognized clade that branched off near the base of Centrosaurinae.…”

Section: Discussionmentioning

confidence: 99%

A remarkable short-snouted horned dinosaur from the Late Cretaceous (late Campanian) of southern Laramidia

et al. 2013

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The fossil record of centrosaurine ceratopsids is largely restricted to the northern region of western North America (Alberta, Montana and Alaska). Exceptions consist of single taxa from Utah (Diabloceratops) and China (Sinoceratops), plus otherwise fragmentary remains from the southern Western Interior of North America. Here, we describe a remarkable new taxon, Nasutoceratops titusi n. gen. et sp., from the late Campanian Kaiparowits Formation of Utah, represented by multiple specimens, including a nearly complete skull and partial postcranial skeleton. Autapomorphies include an enlarged narial region, pneumatic nasal ornamentation, abbreviated snout and elongate, rostrolaterally directed supraorbital horncores. The subrectangular parietosquamosal frill is relatively unadorned and broadest in the mid-region. A phylogenetic analysis indicates that Nasutoceratops is the sister taxon to Avaceratops, and that a previously unknown subclade of centrosaurines branched off early in the group's history and persisted for several million years during the late Campanian. As the first well-represented southern centrosaurine comparable in age to the bulk of northern forms, Nasutoceratops provides strong support for the provincialism hypothesis, which posits that Laramidia—the western landmass formed by inundation of the central region of North America by the Western Interior Seaway—hosted at least two coeval dinosaur communities for over a million years of late Campanian time.

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Section: Discussionmentioning

confidence: 99%

A remarkable short-snouted horned dinosaur from the Late Cretaceous (late Campanian) of southern Laramidia

et al. 2013

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“…Thus, while ANSP 15800 and a referred "adult Avaceratops" MOR 692 (Penkalski and Dodson 1999) do both occur in the Judith River Formation, it will never be possible to definitively assign the latter specimen to Avaceratops without a series of ontogenetic intermediates linking ANSP 15800 to a diagnostic adult morphology of MOR 692. We also note two of the arguments (lack of epimarginals and fenestrated parietals) for assigning MOR 692 as an adult Avaceratops by Penkalski and Dodson (1999) are weakened by the fact that (i) MOR 692 does have epiparietals, although they are low and well fused to the underlying parietal; and (ii) the parietals are incomplete in both specimens, and although small, anteriorly placed fenestrae could have been present, there is no evidence that they were. Finally, we note that the specimens are not chronostratigraphically equivalent, being separated by at least 2 Ma (Fig.…”

Section: Comments On Avaceratopsmentioning

confidence: 99%

“…The Malta new taxon thins adjacent to the thickened rami. It has been argued (Penkalski and Dodson 1999) that ANSP 15800 and MOR 692 lack parietal fenestrae, but this condition is difficult to determine in either specimen due to breakage; however, if they were present in either, they would have been small. Similarly, our reconstruction of the frill of CMN 8804 (Fig.…”

Section: Relationships Of Cmn 8804mentioning

confidence: 99%

“…The holotype of Avaceratops (ANSP 15800) is unequivocally a small, juvenile centrosaurine that lacks the key elements of the nasal and postorbitals. The parietosquamosal frill lacks epimarginals, which, as in juveniles of derived centrosaurins, is most likely related to its ontogenetic age and so is of little or no diagnostic utility (contra Penkalski and Dodson 1999). When included in phylogenetic analyses, ANSP 15800 is usually recovered as a basal taxon within Centrosaurinae, but, as argued by Evans et al (2013) and Currie et al (2016), a basal position in a phylogenetic analysis is typical for taxa based on juvenile material, and (or) missing diagnostically important characteristics.…”

Section: Comments On Avaceratopsmentioning

confidence: 99%

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A basal ceratopsid (Centrosaurinae: Nasutoceratopsini) from the Oldman Formation (Campanian) of Alberta, Canada

et al. 2017

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A partial skull (CMN 8804) of a ceratopsid from the upper unit of the Campanian Oldman Formation of Alberta is the first Canadian example of the newly established Nasutoceratopsini, a new subclade of Centrosaurinae defined as the stembased clade of centrosaurine ceratopsids more closely related to Nasutoceratops titusi than to Centrosaurus apertus. The new clade is diagnosed, in part, by having a parietosquamosal frill lacking modified epimarginals; a small nasal horncore; large, rostrolaterally directed postorbital horncores; and a relatively short, deep face. Although the CMN 8804 taxon closely resembles Nasutoceratops, its phylogenetic position within Nasutoceratopsini is unresolved. The CMN 8804 taxon would have been contemporaneous with dinosaurs from the lower portion of the Dinosaur Park Formation 200 km to the northwest in Dinosaur Provincial Park. The presence of the CMN 8804 taxon in Alberta, and the approximately contemporaneous Nasutoceratops in Utah, indicates that the nasutoceratopsins persisted in both north and south Laramidia well after the first appearance (i.e., Coronosaurus brinkmani) of the newly defined Centrosaurini. This stem-based clade is composed of centrosaurine ceratopsids with welladorned parietosquamosal frills and short postorbital horncores that are more closely related to Centrosaurus apertus than Pachyrhinosaurus canadensis. The rarity of nasutoceratopsins in the well-sampled sediments of Laramidia suggests that they may have had different ecological preferences than centrosaurins, or that their relatively non-diagnostic, fragmentary remains may be misidentified as other centrosaurins. The temporally (ϳ79-76 Ma) and geographically (Utah to Alberta) large distributions of Nasutoceratopsini weakens the hypothesis of distinct north and south Laramidian provinciality.Résumé : La boîte crânienne partielle (CMN 8804) d'un cératopsidé de l'unité supérieure de la Formation d'Oldman, du Campanien de l'Alberta, est le premier exemple canadien de Nasutoceratopsini, un nouveau sous-clade de centrosaurinés défini comme étant le clade de tronc de cératopsidés centrosaurinés plus étroitement apparenté à Nasutoceratops titusi qu'à Centrosaurus apertus. Le diagnostic du nouveau clade repose en partie sur la présence d'une frange pariétosquamosale exempte d'ornementation épimarginale modifiée, d'un petit cornillon nasal, de grands cornillons postorbitaux dirigés rostrolatérale-ment et d'une face profonde et relativement courte. Bien que le taxon de CMN 8804 ressemble de près à Nasutoceratops, sa position phylogénétique au sein des Nasutoceratopsini n'est pas résolue. Le taxon de CMN 8804 aurait été contemporain de dinosaures de la partie inférieure de la Formation de Dinosaur Park, à 200 km au nord-ouest, dans le Dinosaur Provincial Park. La présence du taxon de CMN 8804 en Alberta et de Nasutoceratops environ en même temps en Utah indique que les nasutocératopsinés ont persisté tant dans le nord que dans le sud de la Laramidie bien après la première apparition (c.-à -d., Coronosaurus ...

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“…This morphology is common to all known ceratopsids (e.g., Brown, 1917;Lehman 1989;Holmes and Ryan, 2013). However, morphology of the ribs associated with the last dorsal and dorsosacral vertebrae Centrosaurus (Brown 1917) 0.81 Centrosaurus (Lull 1933) 0.70 Styracosaurus (Holmes and Ryan 2013) 0.74 Brachyceratops (Gilmore 1917) 0.80 Avaceratops (Penkalski and Dodson 1999) 0.80* Triceratops (Gilmore 1917) 0.63 Triceratops (Penkalski and Dodson 1999) 0.59 Triceratops (Fujiwara 2009) 0.66 Vagaceratops 0.68 cf. Anchiceratops (Mallon and Holmes 2010) 0.73 Chasmosaurus belli (CMN 2245, Sternberg 1927 0.71 Chasmosaurus belli (ROM 843, J. Mallon, pers.…”

Section: Rib Morphologymentioning

confidence: 99%

The postcranial skeleton of Vagaceratops irvinensis (Dinosauria, Ceratopsidae)

Holmes

2014

Vert. Anat. Morph. Palaeo.

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Abstract:The postcranial skeleton of Vagaceratops (= Chasmosaurus) irvinensis (CMN 41357), lacking only the tail, most of the left front and left hind limbs, and portions of the pelvis, is preserved in articulation. It is one of the most complete, best articulated ceratopsid skeletons known. Both the manus and vertebral column exhibit conspicuous pathologies, possibly an indication of advanced age at the time of death. The vertebral column comprises a syncervical, six additional cervical vertebrae, and 12 dorsals. A partial synsacrum is represented by two dorsosacrals, four sacrals, two caudosacrals, and a partial third caudosacral centrum. The ribcage, although crushed, is nearly complete. The sternum is unusually wide compared with other ceratopsids. As in other chasmosaurines, the humerus bears a prominent deltopectoral crest that forms the anterior edge of the broad, rectangular proximal humeral expansion. The medial tuberosity is separated from the dorsal surface of the humerus by a distinct notch. The insertion for the latissimus dorsi is conspicuous. The deltopectoral crest extends a full half of the distance to the distal end of the humerus. Epipodials of the forelimb are relatively short compared to the corresponding propodial. The ulna has a long, distinctly triangular olecranon, broadly rounded anterolateral process, prominent medial process, and a deeply concave trochlear notch. The terminal phalanges on the fourth and fifth manual digits are relatively large, and unlike other ceratopsids have distinct distal (possibly articular) facets. The fourth trochanter of the femur is relatively proximal in position. This study and other recent studies of ceratopsid postcrania suggest that potentially useful taxonomic variation is present in the number of dorsosacrals, size of the groove on the ventral surface of the sacrum, morphology of the last dorsal and dorsosacral ribs, morphology of the scapula and proximal expansion of the humerus, morphology of the ulna, ratio of humerus/epipodium, morphology of the fifth manual digit, and position of the fourth trochanter of the femur.

show abstract

The morphology and systematics ofAvaceratops, a primitive horned dinosaur from the Judith River Formation (Late Campanian) of Montana, with the description of a second skull

Cited by 28 publications

References 20 publications

A remarkable short-snouted horned dinosaur from the Late Cretaceous (late Campanian) of southern Laramidia

A remarkable short-snouted horned dinosaur from the Late Cretaceous (late Campanian) of southern Laramidia

A basal ceratopsid (Centrosaurinae: Nasutoceratopsini) from the Oldman Formation (Campanian) of Alberta, Canada

The postcranial skeleton of Vagaceratops irvinensis (Dinosauria, Ceratopsidae)

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