No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
New leptoceratopsids from the Upper Cretaceous of Alberta, Canada
... We assessed the phylogenetic position of RBCM P900 using the character-taxon matrix for ceratopsians presented by He et al. (2015), derived from previous matrices built by Farke et al. (2014), Ryan et al. (2012), andMakovicky (2001). Our matrix includes 34 taxa and 165 characters (Supplemental Informations 1 and 4) and was compiled in Mesquite v3.04 build 725 (Maddison & Maddison, 2011). ...
... The fact that RBCM P900, the first dinosaur specimen recovered from the Sustut Basin, is a leptoceratopsid rather than one of the more commonly encountered groups in many coeval formations in western North America, such as hadrosaurs, ceratopsids, or tyrannosaurs, is surprising, especially given well-documented preservational biases against small-bodied dinosaurs in more fossiliferous areas (Brown et al., 2013a(Brown et al., , 2013bEvans et al., 2013). Most leptoceratopsid taxa are distinguished on the basis of cranial morphology, especially aspects of the lower jaw anatomy (Ryan et al., 2012). However, excellent postcranial material is known for many taxa, making it possible to identify diagnostic features in RBCM P900 despite the absence of cranial material for this specimen. ...
... Despite their stratigraphic and geographic proximity, Leptoceratops and Montanoceratops are not recovered as close relatives in recent phylogenetic analyses in this analysis or by He et al. (2015) and preceding versions of that matrix. Montanoceratops occupies a relatively basal position within Leptoceratopsidae (Makovicky, 2010;Ryan et al., 2012;Farke et al., 2014;He et al., 2015), and was found to be the sister taxon to Ischioceratops from Asia by He et al. (2015). Leptoceratops typically occupies a more derived position and has been recovered as the sister taxon to the Asian Udanoceratops (He et al., 2015). ...
A partial dinosaur skeleton from the Sustut Basin of northern British Columbia, Canada, previously described as an indeterminate neornithischian, is here reinterpreted as a leptoceratopsid ceratopsian, Ferrisaurus sustutensis , gen. et. sp. nov. The skeleton includes parts of the pectoral girdles, left forelimb, left hindlimb, and right pes. It can be distinguished from other named leptoceratopsids based on the proportions of the ulna and pedal phalanges. This is the first unique dinosaur species reported from British Columbia, and can be placed within a reasonably resolved phylogenetic context, with Ferrisaurus recovered as more closely related to Leptoceratops than Montanoceratops . At 68.2–67.2 Ma in age, Ferrisaurus falls between, and slightly overlaps with, both Montanoceratops and Leptoceratops , and represents a western range extension for Laramidian leptoceratopsids.
... The first phylogenetic analysis specifically targeting only basal neoceratopsians was published in 1998 . Several other studies have followed, producing a consensus of basal neoceratopsian relationships (Makovicky, 2001;Chinnery and Horner, 2007;Ryan et al., 2012). Additionally, some new ceratopsian species have never been included in a broad-ranging cladistic analysis You and Dong, 2003), and others have not yet been included in an analysis together He et al., 2015;Zheng et al., 2015). ...
... It has passed through several iterations (Makovicky, 2002(Makovicky, , 2010Makovicky and Norell, 2006). This matrix also provided the basis for the analyses in Xu et al. (2002Xu et al. ( , 2006Xu et al. ( , 2010b, Lee et al. (2011), Ryan et al. (2012), Farke et al. (2014), and to an extent Han et al. (2017). Of the four main matrices, it was the only one purpose-built as part of a major taxonomic review of all known basal neoceratopsian species (Makovicky, 2002). ...
... D, Makovicky (2010). E, Ryan et al. (2012). F, strict consensus of trees in this figure. ...
Basal neoceratopsians are a relatively diverse group of small- to medium-sized herbivorous dinosaurs from the Early to Late Cretaceous of Asia and North America. Although known for over a century, this group has only relatively recently received intense independent study, tied to the rapid increase in known diversity since 1997. Auroraceratops rugosus is one of these recently discovered species and is one of the best-known basal neoceratopsians, being represented by over 80 specimens, and is also the most completely represented neoceratopsian from the Early Cretaceous. A phylogenetic analysis focusing on non-ceratopsid ceratopsians examines the phylogenetic context of Auroraceratops. The analysis is based on a new matrix of 41 taxa and 257 characters. The results recover an Auroraceratops-Aquilops-ZPAL MgD-I/156 clade within basal Neoceratopsia that is sister to a clade composed of Asiaceratops, Yamaceratops, Mosaiceratops, and the larger clades Leptoceratopsidae and Coronosauria. This phylogeny recovers a monophyletic Coronosauria, Leptoceratopsidae, and Protoceratopsidae. Helioceratops is recovered as sister to the rest of Leptoceratopsidae, Ischioceratops is recovered nested within Leptoceratopsidae, and the enigmatic genus Mosaiceratops is recovered as a basal neoceratopsian, sister to Yamaceratops. Yinlong, and Hualianceratops are recovered in an expanded Chaoyangsauridae, and the genus Psittacosaurus is recovered as the earliest diverging lineage in Ceratopsia. Ajkaceratops, the only European ceratopsian, is robustly recovered as sister to the rest of Ceratopsoidea.
SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP
Citation for this article: Morschhauser, E. M., H. You, D. Li, and P. Dodson. 2019. Phylogenetic history of Auroraceratops rugosus (Ceratopsia: Ornithischia) from the Lower Cretaceous of Gansu Province, China; pp. 117–147 in Hailu You, Peter Dodson, and Eric Morschhauser (eds.), Auroraceratops rugosus (Ornithischia, Ceratopsia) from the Early Cretaceous of northwestern Gansu Province, China. Society of Vertebrate Paleontology Memoir 18. Journal of Vertebrate Paleontology 38(Supplement). DOI: 10.1080/02724634.2017.1509866.
... In Dinosaur Provincial Park (DPP), where the entirely exposed DPF is 70 m thick, bentonites collected from the top of the Oldman Formation (5.5 m below the DPF), the middle of the DPF (36.0 m above the Oldman Formation), and near the base of the LCZ (61.5 m above the Oldman Formation) yielded 40 Ar/ 39 The DPF also currently has three recognized distinct faunal zones, each of which is characterized by a unique assemblage of centrosaurine and lambeosaurine taxa [15,16]. These Dinosaur Park faunal zones (DPFZs) are, in ascending stratigraphic order: Centrosaurus-Corythosaurus Zone (DPFZ 1), Styracosaurus-Lambeosaurus lambei Zone (DPFZ 2), and Lambeosaurus magnicristatus-pachyrhinosaur Zone (DPFZ 3). ...
... These Dinosaur Park faunal zones (DPFZs) are, in ascending stratigraphic order: Centrosaurus-Corythosaurus Zone (DPFZ 1), Styracosaurus-Lambeosaurus lambei Zone (DPFZ 2), and Lambeosaurus magnicristatus-pachyrhinosaur Zone (DPFZ 3). Chasmosaurus russelli, C. belli, and V. irvinensis are also thought to be constrained to these three zones, respectively [15,16]. pm s vr, ventral recess on premaxillary septum; po, postorbital; r, rostral; r dpr, rostral dorsal process; r vpr, ventral process of rostral; sbor f, subordinate fossa; sf, septal fossa; sf acc st, septal fossa accessory strut; sfl, septal flange; tpr, triangular process; tpr rc, triangular process recess. ...
... The relatively large stratigraphic range of C. russelli is the result of recently conducted fieldwork, which revealed that the holotype (CMN 8800) of this species was recovered from the upper DPF, and not the lower DPF as previously supposed. This sequence supports the stratigraphic null hypothesis of no temporal separation between Chasmosaurus specimens previously referred to C. belli and C. russelli (Fig 4; contra [5,15,16]). ...
Background:
The chasmosaurine ceratopsid Chasmosaurus is known from the Upper Cretaceous (Campanian) Dinosaur Park Formation of southern Alberta and Saskatchewan. Two valid species, Chasmosaurus belli and C. russelli, have been diagnosed by differences in cranial ornamentation. Their validity has been supported, in part, by the reported stratigraphic segregation of chasmosaurines in the Dinosaur Park Formation, with C. belli and C. russelli occurring in discrete, successive zones within the formation.
Results/conclusions:
An analysis of every potentially taxonomically informative chasmosaurine specimen from the Dinosaur Park Formation indicates that C. belli and C. russelli have indistinguishable ontogenetic histories and overlapping stratigraphic intervals. Neither taxon exhibits autapomorphies, nor a unique set of apomorphies, but they can be separated and diagnosed by a single phylogenetically informative character-the embayment angle formed by the posterior parietal bars relative to the parietal midline. Although relatively deeply embayed specimens (C. russelli) generally have relatively longer postorbital horncores than specimens with more shallow embayments (C. belli), neither this horncore character nor epiparietal morphology can be used to consistently distinguish every specimen of C. belli from C. russelli.
Status of kosmoceratops in the dinosaur park formation:
Kosmoceratops is purportedly represented in the Dinosaur Park Formation by a specimen previously referred to Chasmosaurus. The reassignment of this specimen to Kosmoceratops is unsupported here, as it is based on features that are either influenced by taphonomy or within the realm of individual variation for Chasmosaurus. Therefore, we conclude that Kosmoceratops is not present in the Dinosaur Park Formation, but is instead restricted to southern Laramidia, as originally posited.
... The leptoceratopsids are a group of small, quadrupedal horned dinosaurs that have so far been found exclusively in the Upper Cretaceous (upper Santonian-upper Maastrichtian) of Asia and western North America [1]. With a typical body length of about two meters, they are much smaller than the contemporary ceratopsids [2]. ...
... In order to more effectively assess the position of Ischioceratops within Ceratopsia, the specimen was coded in the data matrix published by Farke et al [83], which was modified from earlier matrices [1,30,44,74,77,84] (S2 File). We changed character (130) to the following: Femoral fourth trochanter triangular and pendant (0) or parallelogram-shaped and pendant (1) or ridge-like (2) or reduced (3). ...
... We changed character (130) to the following: Femoral fourth trochanter triangular and pendant (0) or parallelogram-shaped and pendant (1) or ridge-like (2) or reduced (3). We changed character (154) to the following: Dorsal border of iliac blade vertical (0) or strongly everted (1). As a result of detailed observations from Ischioceratops and other basal ceratopsians, the following new character (number 155) was added to the matrix: Neural spines of middle caudal vertebrae: no longer than neural spines of anterior caudals (0) or longer than neural spines of anterior caudals (1) The matrix (Table A in S2 File) was run in TNT 1.1 [80] using the tree bisection reconnection algorithm, with 10,00 replicates, up to 10,000 trees saved per replication, and branches with a minimum length of 0 collapsed. ...
The partial skeleton of a leptoceratopsid dinosaur, Ischioceratops zhuchengensis gen. et sp. nov., was excavated from the bone-beds of the Upper Cretaceous Wangshi Group of Zhucheng, Shandong Province, China. This fossil represents the second leptoceratopsid dinosaur specimen recovered from the Kugou locality, a highly productive site in Zhucheng. The ischium of the new taxon is morphologically unique among known Dinosauria, flaring gradually to form an obturator process in its middle portion and resembling the shaft of a recurve bow. An elliptical fenestra perforates the obturator process, and the distal end of the shaft forms an axehead-shaped expansion. The discovery of Ischioceratops increases the known taxonomic diversity and morphological disparity of the Leptoceratopsidae.
... In order to assess its position within Ceratopsia, Aquilops was scored using previously published matrices, with additions and revisions as noted below. Characters 1-133 were taken from Makovicky and Norell [3], characters 134-147 were taken from Makovicky [63], characters 148 and 149 were taken from characters 135 and 136 of Lee et al. [64], and characters 150 and 151 are from Ryan et al. [65]. In order to help resolve Ceratopsidae, characters 152 (circumnarial depression, if deep, simple or complex) and 153 (narial spine absent or present) were added. ...
... In order to help resolve Ceratopsidae, characters 152 (circumnarial depression, if deep, simple or complex) and 153 (narial spine absent or present) were added. Following Ryan et al. [65], character 140 was replaced with the construction and codings of character 134 from Lee et al. [64]. A full list of characters is provided in Text S1 (File S1). ...
... Five additional steps were required to force Aquilops as a ceratopsoid. The overall structure of the tree is, unsurprisingly, similar to that produced using other recent versions of the matrix [63,65]. ...
The fossil record for neoceratopsian (horned) dinosaurs in the Lower Cretaceous of North America primarily comprises isolated teeth and postcrania of limited taxonomic resolution, hampering previous efforts to reconstruct the early evolution of this group in North America. An associated cranium and lower jaw from the Cloverly Formation (?middle-late Albian, between 104 and 109 million years old) of southern Montana is designated as the holotype for Aquilops americanus gen. et sp. nov. Aquilops americanus is distinguished by several autapomorphies, including a strongly hooked rostral bone with a midline boss and an elongate and sharply pointed antorbital fossa. The skull in the only known specimen is comparatively small, measuring 84 mm between the tips of the rostral and jugal. The taxon is interpreted as a basal neoceratopsian closely related to Early Cretaceous Asian taxa, such as Liaoceratops and Auroraceratops. Biogeographically, A. americanus probably originated via a dispersal from Asia into North America; the exact route of this dispersal is ambiguous, although a Beringian rather than European route seems more likely in light of the absence of ceratopsians in the Early Cretaceous of Europe. Other amniote clades show similar biogeographic patterns, supporting an intercontinental migratory event between Asia and North America during the late Early Cretaceous. The temporal and geographic distribution of Upper Cretaceous neoceratopsians (leptoceratopsids and ceratopsoids) suggests at least intermittent connections between North America and Asia through the early Late Cretaceous, likely followed by an interval of isolation and finally reconnection during the latest Cretaceous.
... Small ornithischian occurrences were nearly absent from the database of Currie and Koppelhus (2005) because there is a taphonomic bias against their preservation (Brown et al. 2013b), and because either their associated quarries were long forgotten or their collection did not require substantial digging that would produce a quarry. We therefore sourced more comprehensive count data from additional literature (leptoceratopsids: Ryan et al. 2012;pachycephalosaurids: Evans et al. 2013;thescelosaurids: Brown et al. 2013a). Pachycephalosauridae is overrepresented among the small ornithischians, due to the taphonomic resistance of their distinctive frontoparietal domes Mallon and Evans 2014). ...
... Third, leptoceratopsids and immature ceratopsids provide a notable exception to the pattern we document here. These two groups coexisted in North America for at least 20 million years (Ryan et al. 2012), and yet their near-total overlap in ecomorphospace (assuming our 13 linear variables adequately reflect niche relationships) suggests that their ecological interactions were not strongly competitive in nature. Therefore, any dietary resources shared by the two groups may not have been limiting in the same way. ...
It has been argued that, throughout the Mesozoic, the immature growth forms of megaherbivorous dinosaurs competitively excluded small herbivorous dinosaur species, leading to the left-skewed species richness-body mass distributions of their fossil assemblages. By corollary, where large and small herbivores coexisted over a geologically significant period of time, they must have exhibited niche partitioning. We use multivariate ecomorphological analysis of the Late Cretaceous ornithischian dinosaur assemblage of North America to examine this prediction. Our results indicate good ecomorphological separation of most, but not all, species at small body size, although more work is required to demonstrate that these patterns were adaptive. Calculation of browse profiles using corrected abundance data and bracketed estimates of energy requirements suggests that immature megaherbivores – most particularly hadrosaurids – outstripped coexisting small ornithischian species in their control of the resource base.
... The DPF has also been subdivided into three distinct faunal zones, with each one characterized by a unique assemblage of centrosaurine and lambeosaurine taxa (Ryan and Evans 2005;Ryan et al. 2012;Fig. 2). ...
... Chasmosaurus russelli, C. belli, and V. irvinensis were also thought to be constrained to these three zones, respectively (Ryan and Evans 2005;Ryan et al. 2012). However, Campbell et al. (2016) recently demonstrated that skulls previously referred to C. russelli span all three zones, as the holotype was actually collected from the upper (Lambeosaurus magnicristatus-pachyrhinosaur) zone. ...
The Dinosaur Park Formation (DPF) has a diverse assemblage of chasmosaurines currently represented by Chasmosaurus belli, C. russelli, Vagaceratops irvinensis, and Mercuriceratops gemini, and may also include remains possibly referable to Spiclypeus shipporum. Two skulls, YPM 2016 and AMNH 5402, previously referred to C. belli, both have a straight posterior parietal bar with five epiparietals present (YPM 2016) or inferred (AMNH 5402) on each side – the combination of which is unique to V. irvinensis. Based on our new morphological observations and interpretations of these two skulls, we recover V. irvinensis as a species of Chasmosaurus (C. irvinensis), although the interrelationships between C. irvinensis, C. belli, and C. russelli remain unclear. We refrain from formerly assigning YPM 2016 and AMNH 5402 to C. irvinensis, however, as their parietal fenestrae are significantly larger and their epiparietals are significantly shorter than those of C. irvinensis; instead, we reassign these two skulls to Chasmosaurus sp. Given the low stratigraphic position of YPM 2016 (unknown in AMNH 5402) relative to C. irvinensis, we believe this specimen to represent a basal member of the lineage leading to C. irvinensis. If our assessment is correct, this would indicate that the C. irvinensis lineage has a large degree of stratigraphic overlap with that of C. belli and C. russelli. The close phylogenetic relationship and supposed stratigraphic separation for these three taxa reported in previous studies were used to suggest that they may represent an anagenetic lineage, whereby C. russelli evolved into C. belli, and C. belli evolved into, and was entirely replaced by, the latter. However, the lack of stratigraphic separation between these three taxa indicates that they instead arose via cladogenesis.
... Whether the result of collecting bias (Goodwin and Horner, 2010) or taphonomic bias (Eberth, 2010), it is nonetheless a trend that also includes smaller members of the clade. Many non-ceratopsoid ceratopsians either have very limited postcranial remains (Hualianceratops, Chaoyangsaurus, Archaeoceratops yujingziensis, Asiaceratops, Yamaceratops), or their postcranial remains have not been described in the literature (Prenoceratops), or they lack postcranial remains entirely (Liaoceratops, Aquilops, Helioceratops, Gryphoceratops, Unescoceratops, Magnirostris, Ajkaceratops) (Nessov, 1995;Zhao et al., 1999;Xu et al., 2002;You and Dong, 2003;Chinnery, 2004;Makovicky and Norell, 2006;Jin et al., 2009;} Osi et al., 2010;You et al., 2010;Ryan et al., 2012;Farke et al., 2014;He et al., 2015). In the context of this relative paucity of ceratopsian postcranial remains, the material from Auroraceratops becomes quite important. ...
... Although much less flamboyant than their ceratopsid cousins (Sampson et al., 2010), basal neoceratopsians have enjoyed a renaissance of interest since 1998 (Makovicky, 2010). A sustained pace of new discoveries ( } Osi et al., 2010;You et al., 2010;Lee et al., 2011;Ryan et al., 2012;Zheng et al., 2015;He et al., 2015) has greatly increased the diversity of known species. Basal neoceratopsians were a successful radiation in parallel to the radiation of ceratopsids in the latest Cretaceous on both sides of the Pacific Ocean (Makovicky, 2010;Xu et al., 2010;Morschhauser et al., 2019b). ...
The species Auroraceratops rugosus was originally described based upon a single skull. With the recovery of over 80 individuals, a complete description of the postcranial skeleton is presented. Auroraceratops is currently the most complete exemplar we have of ceratopsian postcranial anatomy between Psittacosaurus and Leptoceratops. Adult Auroraceratops had a length of approximately 125 cm and an approximate hip height of 44 cm. Osteological correlates of stance in the fore- and hind limb unequivocally indicate a bipedal gait. The phylogenetically corrected quadrupedal mass-estimation equation modified for mass estimation of bipedal terrestrial vertebrates estimates an average mass of Auroraceratops at 15.5 kg. It has the phylogenetically and temporally earliest documentation of the syncervical in Ceratopsia. The mid-caudal neural spines are elongate and erect, a feature previously only known in Leptoceratopsidae and Protoceratopsidae. Despite being longer than in most ceratopsians, the mid-caudal neural spines are not as tall as in some leptoceratopsids. Most of the phylogenetically relevant characters of the postcranial skeleton in Auroraceratops are a mosaic of features plesiomorphic to Neoceratopsia and features previously considered to be unique to later diverging clades, such as Leptoceratopsidae and Protoceratopsidae.
Citation for this article: Morschhauser, E. M., H. You, D. Li, and P. Dodson. 2019. Postcranial morphology of the basal neoceratopsian (Ornithischia: Ceratopsia) Auroraceratops rugosus from the Early Cretaceous (Aptian–Albian) of northwestern Gansu Province, China; pp. 75–116 in Hailu You, Peter Dodson, and Eric Morschhauser (eds.), Auroraceratops rugosus (Ornithischia, Ceratopsia) from the Early Cretaceous of northwestern Gansu Province, China. Society of Vertebrate Paleontology Memoir 18. Journal of Vertebrate Paleontology 38(Supplement). DOI: 10.1080/02724634.2017.1524383.
... The strong ventrally convex curvature to the ventral margin of the dentary of Archaeoceratops, leptoceratopsids (Sternberg, 1951;Chinnery, 2004;Ryan et al., 2012), and Yamaceratops (Makovicky and Norell, 2006) contrasts with the straight ventral margin of the dentary of Auroraceratops. Yinlong also has two small lateral processes on the predentary, and its dentary is much shallower than that of Auroraceratops (Fig. 4). ...
... However, unlike Auroraceratops, the tooth row of Montanoceratops is not parallel to the ventral margin of the dentary. Montanoceratops, along with several other leptoceratopsids (Xu et al., 2010;Ryan et al., 2012), has a dentary that is deeper rostrally than it is caudally (Chinnery and Weishampel, 1998), which contrasts with the equal height of the dentary of Auroraceratops . ...
The basal neoceratopsian dinosaur Auroraceratops rugosus was described based on a single skull from the Gongpoquan Basin in northwestern Gansu Province, China. The genus is now known from over 80 specimens, including many from the neighboring Yujingzi Basin. Auroraceratops is one of the best-known basal neoceratopsians. Auroraceratops can be diagnosed by the following autapomorphies: inflated premaxillary teeth; a fungiform expansion of the lacrimal; large tuber caudodorsally on the dentary near the contact with the surangular; and tubercle on the lateral face of the dentary at about the middle of the mandible. Auroraceratops also has a combination of plesiomorphic and derived characters. It possesses characters plesiomorphic to Neoceratopsia, such as broad nasals (seen in basal ceratopsians, such as Yinlong), the absence of a lateral ridge on the surangular, a relatively high number of premaxillary teeth (three), and rugosity on the dentary, jugal, surangular, and sometimes the postorbital, which is in detail similar to that seen in chaoyangsaurids. At the same time, Auroraceratops possesses derived characters not seen in Liaoceratops, the earliest diverging member of Neoceratopsia. These features include an epijugal and a surangular wall lateral to the mandibular glenoid fossa. The cranial anatomy of the early horned dinosaur Auroraceratops rugosus is described.
Citation for this article: Morschhauser, E. M., D. Li, H. You, and P. Dodson. 2019. Cranial anatomy of the basal neoceratopsian Auroraceratops rugosus (Ornithischia: Ceratopsia) from the Yujingzi Basin, Gansu Province, China; pp. 36–68 in Hailu You, Peter Dodson, and Eric Morschhauser (eds.), Auroraceratops rugosus (Ornithischia, Ceratopsia) from the Early Cretaceous of northwestern Gansu Province, China. Society of Vertebrate Paleontology Memoir 18. Journal of Vertebrate Paleontology 38(Supplement). DOI: 10.1080/02724634.2017.1399136.
... Recent discoveries of new taxa and revisions of historically described taxa have increased the number of ceratopsian species and the cranial material available, with some taxa represented now by dozens of specimens. These new studies have increased the knowledge of the systematics and taxonomy of the group, along with their complex palaeobiogeography and evolutionary history (Sampson, 1995;Wolfe and Kirkland, 1998;Lambert et al., 2001;Xu et al., 2002Xu et al., , 2006Xu et al., , 2010aXu et al., , 2010bMakovicky and Norell, 2006;Ryan, 2007;Sereno et al., 2007Sereno et al., , 2010Wu et al., 2007;Longrich, 2010Longrich, , 2013Sampson et al., , 2013Farke et al., 2011Farke et al., , 2014Lee et al., 2011;Fiorillo and Tykoski, 2012;Ryan et al., 2012aRyan et al., , 2012bHedrick and Dodson, 2013;Wick and Lehman, 2013;Brown and Henderson, 2015;Evans and Ryan, 2015;Han et al., 2015;Zheng et al., 2015). This large dataset now allows the application of GM to skulls and lower jaws (both in lateral view) and a quantitative investigation of cranial and lower jaw shape variation within ceratopsians through time in a specific phylogenetic scenario. ...
... We followed Sampson et al. ( , 2013, Evans and Ryan (2015), and Brown and Henderson (2015) regarding the affinities within Chasmosaurinae and Centrosaurinae. Lambert et al. (2001), Ösi et al. (2010), , Ryan et al. (2012a), were considered for the relationships within Protoceratopsidae. For the phylogenetic relationships within Leptoceratopsidae, we followed Nessov et al. (1989), Nessov (1995 We calibrated branch lengths in millions of years (Ma) based on the stratigraphic occurrences in the fossil record. ...
Organisms: Ceratopsians were herbivorous, beaked dinosaurs, ranging from 1 m to 9 m in body length, usually four-footed, and with a bony frill that extended backwards from the cranium over the nape of the neck. Known from Asia, Europe, and North America, they appeared in the Late Jurassic and persisted until the end of the Late Cretaceous. Questions: Which evolutionary processes drive the phenotypic evolution of skulls and lower jaws within Ceratopsia? What is the degree of morphological integration between the skull and lower jaw, and between the snout and frill among clades? Finally, are there any morphological evolution rate shifts across the ceratopsian phylogeny? Data: Photographs from 121 ceratopsian skulls and 122 lower jaws in lateral view, both from original photos and published pictures. Fifty-five ceratopsian species are represented in the sample. Methods: We investigated cranial and lower jaw shape changes across ceratopsians applying two-dimensional geometric morphometrics. We also investigated the morphological variation of the snout and the frill. Using phylogenetic generalized least squares regression, we estimated the degree of phylogenetic signal in size and shape data, as well as in the shape–size relationship. We performed phenotypic evolutionary rate analysis on shape data to describe phenotypic shifts across the phylogeny. Using a rarefied version of Escoufier's RV coefficient, we tested morphological integration between skulls and lower jaws, and between snouts and frills. Finally, we explored the potential link between cranial and frill shape evolution in ceratopsians and the radiation of angiosperms using a linear regression model. Results: Skull, snout, and frill shapes differ among clades (with the exception of lepto-ceratopsids and protoceratopsids). Lower jaws show distinct morphologies among groups. Size and shape changes are phylogenetically structured. The frill drives the morphological variation Correspondence: L. Maiorino, of the skull, co-varying much more with the lower jaw than with the snout. The frill appears to evolve to co-vary better with the lower jaw in the more morphologically derived clades than in basal ones. A significant linear relationship does exist between cranial shape and angiosperm occurrences, suggesting the hypothesis that the frill evolved in response to changes in dietary compositions associated with the turnover between gymnosperms and angiosperms during the Cretaceous. Significant negative shifts in evolutionary rates characterize skull, snout, frill, and lower jaw shapes, corresponding to nodes where psittacosaurids diverge from other taxa. In contrast, a significant positive shift in skull and snout shape rate of evolution characterizes the clade Ceratopsoidea. Conclusion: The frill is the main driving force in the overall cranial shape within Ceratopsia and evolved secondarily to better co-vary with the lower jaw to produce a more efficient masti-catory apparatus. The changes in frill shape are correlated with the angiosperm diversification that occurred in the Cretaceous and thus correlated with changes in diet. Ceratopsians exhibit a slowdown in the phenotypic evolutionary rate in the Early Cretaceous and an acceleration of the phenotypic rate in the Late Cretaceous.
... An updated dinosaurian faunal list for the DPF was compiled from multiple sources Ryan and Evans, 2005;Longrich, 2008Longrich, , 2009Eberth and Evans, 2011;Ryan et al., 2012). Attempts have been made to survey the literature as thoroughly as possible and to use the most current taxonomy. ...
... This point marks the smallest taxon that exceeds 50% completeness, in this case 100% complete (Ornithomimus edmontonicus), and as such marks the point where the smallest nearly complete taxa are found. The second division occurs at a less precise location between the 29th and 32nd taxa (inclusive of: Unescoceratops koppelhusae (Ryan et al., 2012), the large unnamed ornithomimid (Longrich, 2008), Edmontonia rugosidens and Panoplosaurus mirus) at an estimated mass between 160 and 1600 kg. Although the sliding window mean difference method is ambiguous as to the precise location of this division, the middle of this range (between the large unnamed ornithomimid and Edmontonia rugosidens) is characterised by both the most massive relatively incomplete taxon (all larger taxa are more than 41% complete), and a distinct jump in size from 370 kg to 1400 kg. ...
... To assess the systematic position of Hualianceratops, a new character list and matrix was compiled and analyzed (S1 and S2 Files). Our data matrix was mainly based on those of Ryan et al. [15] and Farke et al. [9], which were in turn modified from the matrices of Makovicky and Norell [8], Makovicky [16], Xu et al. [17], and Lee et al. [18]. However, these matrices contain few characters germane to the basalmost ceratopsians. ...
... Therefore, the dentary is much deeper relative to its length in Hualianceratops than in Yinlong. A relatively deep dentary is a derived feature that occurs in Psittacosaurus [29,33] and some derived neoceratopsians such as Protoceratops [36] and Leptoceratops [15] (Fig 8). ...
Ceratopsia is one of the best studied herbivorous ornithischian clades, but the early evolution of Ceratopsia, including the placement of Psittacosaurus, is still controversial and unclear. Here, we report a second basal ceratopsian, Hualianceratops wucaiwanensis gen. et sp. nov., from the Upper Jurassic (Oxfordian) Shishugou Formation of the Junggar Basin, northwestern China. This new taxon is characterized by a prominent caudodorsal process on the subtemporal ramus of the jugal, a robust quadrate with an expansive quadratojugal facet, a prominent notch near the ventral region of the quadrate, a deep and short dentary, and strongly rugose texturing on the lateral surface of the dentary. Hualianceratops shares several derived characters with both Psittacosaurus and the basal ceratopsians Yinlong, Chaoyangsaurus, and Xuanhuaceratops. A new comprehensive phylogeny of ceratopsians weakly supports both Yinlong and Hualianceratops as chaoyangsaurids (along with Chaoyangsaurus and Xuanhuaceratops), as well as the monophyly of Chaoyangosauridae + Psittacosaurus. This analysis also weakly supports the novel hypothesis that Chaoyangsauridae + Psittacosaurus is the sister group to the rest of Neoceratopsia, suggesting a basal split between these clades before the Late Jurassic. This phylogeny and the earliest Late Jurassic age of Yinlong and Hualianceratops imply that at least five ceratopsian lineages (Yinlong, Hualianceratops, Chaoyangsaurus + Xuanhuaceratops, Psittacosaurus, Neoceratopsia) were present at the beginning of the Late Jurassic.
... Leptoceratopsids and other basal neoceratopsians have short, deep jaws that would be well-suited to shearing tough, fibrous vegetation (Longrich, 2010), and Leptoceratopsidae in particular are characterized by teeth with a unique combination of crushing and shearing facets (Ostrom, 1966) and very short, deep, 'nutcracker' jaws (Brown, 1914;Kurzanov, 1992;Chinnery, 2004;Chinnery and Horner, 2007;Ryan et al., 2012) with the dentigerous process of the maxilla being correspondingly short and deep (Chinnery, 2004;Chinnery and Horner, 2007). As the strength of a structure in bending or shearing increases with depth (Gordon, 1978), this jaw structure suggests adaptation to produce high bite forces and process highly resistant food items. ...
... (Kurzanov, 1992;Xu et al., 2010a), (2), Leptoceratops, Montanoceratops, Gryphoceratops, Unescoceratops and cf. Prenoceratops (Alberta) (Brown, 1914;Makovicky, 2010;Miyashita et al., 2010;Ryan et al., 2012); (3) Montanoceratops, Prenoceratops, Cerasinops, and Leptoceratops (Brown, 1942;Chinnery and Horner, 2007;Ott, 2007) (Miyashita et al., 2010) (Montana); (4) Black Creek ceratopsian (this paper); (5) Kristianstaad ceratopsian (Sweden) (Lindgren et al., 2007); (6) Craspedodon lonzeensis (Belgium) (Godefroit and Lambert, 2007). (Owens and Sohl, 1989); stratigraphic column after Harris and Self--Trail (Harris and Self--Trail, 2006). ...
Tyrannosaurs and hadrosaurs from the Late Cretaceous of eastern North America (Appalachia) are distinct from those found in western North America (Laramidia), suggesting that eastern North America was isolated during the Late Cretaceous. However, the Late Cretaceous fauna of Appalachia remains poorly known. Here, a partial maxilla from the Campanian Tar Heel Formation (Black Creek Group) of North Carolina is shown to represent the first ceratopsian from the Late Cretaceous of eastern North America. The specimen has short alveolar slots, a ventrally projected toothrow, a long dentigerous process overlapped by the ectopterygoid, and a toothrow that curves laterally, a combination of characters unique to the Leptoceratopsidae. The maxilla has a uniquely long, slender and downcurved posterior dentigerous process, suggesting a specialized feeding strategy. The presence of a highly specialized ceratopsian in eastern North America supports the hypothesis that Appalachia underwent an extended period of isolation during the Late Cretaceous, leading the evolution of a distinct dinosaur fauna dominated by basal tyrannosauroids, basal hadrosaurs, ornithimimosaurs, nodosaurs, and leptoceratopsids. Appalachian vertebrate communities are most similar to those of Laramidia. However some taxa-including leptoceratopsids-are also shared with western Europe, raising the possibility of a Late Cretaceous dispersal route connecting Appalachia and Europe.
... En general, el registro fósil de dinosaurios mexicanos coincide con las faunas de dinosaurios de Norteamérica, con abundantes taxa de gran tamaño como tiranosáuridos, hadrosáuridos y ceratópsidos y en menor abundancia los pequeños dromeosáuridos, troodóntidos y pachycephalosáuridos. Destaca la presencia de abundantes ornitomímidos en México. Según Holtz Jr. et al. (2004), Zanno y Sampson (2005), Ryan et al. (2012), Brown et al. (2013) y Evans et al. (2013), las faunas norteamericanas estaban representadas por una diversidad subestimada de pequeños dinosaurios pertenecientes a los Oviraptorosauria, Thescelosauridae, Pachycephalosauridae y Leptoceratopsidae. Su rareza en el registro fósil de toda Norteamérica se debe a la mayor susceptibilidad de los pequeños huesos a la destrucción por los carnívoros, la fragmentación a través de la bioturbación y a procesos erosivos . ...
... novel finding and may be the result of taphonomic biases not studied in Mexico. According to Holtz et al. (2004), Zanno and Sampson (2005), Ryan et al. (2012), Brown et al. (2013) and Evans et al. (2013) in addition to the large bodied taxa of the North American dinosaurs, they are also represented by underestimated diversity of small dinosaurs belonging to the Oviraptorosauria, Thescelosauridae, Pachycephalosauridae and Leptoceratopsidae. Their rarity in the fossil record of all North America is due by the greater susceptibility of small bones to destruction by carnivores, breakage through bioturbation and weathering . ...
For many years the diversity of dinosaurs of Mexico during the Late Cretaceous has been poorly understood. This is due to the limited taxonomical determinations and the abundant undescribed material. This paper presents a new review of the up-to-date osteological record of Late Cretaceous dinosaurs from Mexico, based on published papers, unpublished data and direct observation of the material housed in Mexican paleonto-logical collections and in the field. Some diagnostic dinosaur bones were taxonomically reassigned and others reported in the literature were located in collections. We document new localities with dinosaur remains in Fronteras Sonora, Manuel Benavides and Jiménez Chihuahua, General Cepeda and Saltillo Coahuila. Additionally we report new material relating to tyrannosaurids, ornithomimids, ankylosaurs, ceratopsids and hadrosaurids which extends their geographic and temporal distribution in Mexico. This investigation has revealed a dinosaur faunal assemblage consistent with others studies of North American Late Cretaceous faunas , abundant large bodied dinosaurs and poorly represented small dinosaurs. The lack of oviraptorosaurs, lepoceratopsids and thescelosaurids suggests the need to develop new method in the search for small-dinosaurs in order to gain a more complete picture of dinosaur communities in Mexico and North America during the Late Cretaceous.
... An updated dinosaurian faunal list for the DPF was compiled from multiple sources Ryan and Evans, 2005;Longrich, 2008Longrich, , 2009Eberth and Evans, 2011;Ryan et al., 2012). Attempts have been made to survey the literature as thoroughly as possible and to use the most current taxonomy. ...
... This point marks the smallest taxon that exceeds 50% completeness, in this case 100% complete (Ornithomimus edmontonicus), and as such marks the point where the smallest nearly complete taxa are found. The second division occurs at a less precise location between the 29th and 32nd taxa (inclusive of: Unescoceratops koppelhusae (Ryan et al., 2012), the large unnamed ornithomimid (Longrich, 2008), Edmontonia rugosidens and Panoplosaurus mirus) at an estimated mass between 160 and 1600 kg. Although the sliding window mean difference method is ambiguous as to the precise location of this division, the middle of this range (between the large unnamed ornithomimid and Edmontonia rugosidens) is characterised by both the most massive relatively incomplete taxon (all larger taxa are more than 41% complete), and a distinct jump in size from 370 kg to 1400 kg. ...
A study of the distribution of dinosaurian body masses in the Dinosaur Park Formation (DPF; Campanian; southern Alberta), reveals a prominent negative skew; a pattern distinct from those of modern terrestrial faunas. We find a direct and robust correlation between taxon size (estimated live body mass) and known completeness. There is a clear dichotomy between large and small-bodied taxa at around 60 kg, in which taxa less than 60 kg are significantly less complete (mean completeness = 7.6%) than those with an estimated mass of 60 kg or greater (mean = 78.2%). Along with completeness, there is also a strong association of body size and taphonomic mode, with small taxa known largely from isolated and occasionally associated remains, and large taxa known from articulated skeletons. In addition, there is a significant correlation between taxon body mass and both date of discovery and of description, with taxa < 60 kg taking an average of 65.9 and 75.6 years to discover and describe, respectively, compared to 33.6 and 34.1 years for taxa > 60 kg. The rates of both cumulative discovery and description for large taxa are best described by a logarithmic curve nearing an asymptote, whereas small taxa show either a linear or power increase through time. This suggests that our current knowledge of the large-bodied dinosaur assemblage is reasonably representative of the true biological fauna with few discoveries likely to be made in the future. However, small taxa are greatly underestimated in both their diversity and abundance, with many more potential discoveries to be made. Given that (1) the sedimentary deposits and fossil assemblages in the DPF together represent one of the best studied examples of a Mesozoic alluvial‐paralic (terrestrial) ‘palaeoecosystem,’ and (2) similar patterns have been suggested (but not documented) for other Mesozoic terrestrial ecosystems in the Western Interior of North America, we suggest that this pattern of size bias may typify vertebrate fossil assemblages in terrestrial Mesozoic systems. If so, such biases must be considered before patterns of diversity in dinosaur communities through time can be considered accurate, or used to compare and interpret Mesozoic palaeoecosystems.
... Among western North American units, only the Niobrara Formation of Kansas, the Milk River Formation of Alberta and the Allison Member (Menefee Formation) of New Mexico produce dinosaur material from the same time diagnostic to low taxonomic levels. Each has produced two species currently considered valid [102][103][104][105][106][107]. The Niobrara dinosaurs include the Santonian hadrosauromorph Claosaurus and nodosaurid Niobrarasaurus [102]. ...
During the Cretaceous, diversifications and turnovers affected terrestrial vertebrates experiencing the effects of global geographical change. However, the poor fossil record from the early Late Cretaceous has concealed how dinosaurs and other terrestrial vertebrates responded to these events. I describe two dinosaurs from the Santonian to Early Campanian of the obscure North American paleolandmass Appalachia. A revised look at a large, potentially novel theropod shows that it likely belongs to a new clade of tyrannosauroids solely from Appalachia. Another partial skeleton belongs to an early member of the Hadrosauridae, a highly successful clade of herbivorous dinosaurs. This skeleton is associated with the first small juvenile dinosaur specimens from the Atlantic Coastal Plain. The tyrannosauroid and hadrosaurid substantiate one of the only Late Santonian dinosaur faunas and help pinpoint the timing of important anatomical innovations in two widespread dinosaur lineages. The phylogenetic positions of the tyrannosauroid and hadrosaurid show Santonian Appalachian dinosaur faunas are comparable to coeval Eurasian ones, and the presence of clades formed only by Appalachian dinosaur taxa establishes a degree of endemism in Appalachian dinosaur assemblages attributable to episodes of vicariance.
... Eberth, 2017, personal communication). This confidently places the specimen within the Corythosaurus-Centrosaurus zone (Ryan et al., 2012;Mallon et al., 2013), and as result, is here referred to Centrosaurus apertus as this is the only centrosaurine ceratopsid species known to occur in this well sampled (>20 diagnostic skulls and ∼20 bonebeds) interval (Eberth & Getty, 2005;Brown, 2013). ...
Bite marks on bones can provide critical information about interactions between carnivores and animals they consumed (or attempted to) in the fossil record. Data from such interactions is somewhat sparse and is hampered by a lack of records in the scientific literature. Here, we present a rare instance of feeding traces on the frill of a juvenile ceratopsian dinosaur from the late Campanian Dinosaur Park Formation of Alberta. It is difficult to determine the likely tracemaker(s) but the strongest candidate is a small-bodied theropod such as a dromaeosaur or juvenile tyrannosaur. This marks the first documented case of carnivore consumption of a juvenile ceratopsid, but may represent scavenging as opposed to predation.
... Macrofloral remains suggest that the Santonian was characterized by a warm and humid climate (Bell, 1963;Wolfe and Upchurch, 1987;Upchurch and Wolfe, 1993), while microfloral assemblages indicate a landscape of open forests with shallow ponds (Braman, 2001;Kalgutkar and Braman, 2008). The Deadhorse Coulee Member has produced a diverse fauna composed of amphibians, bony fishes, chondrichthyans, crocodylomorphs, dinosaurs, mammals, squamates, and turtles, although most are represented by microvertebrate remains and isolated or partial skeletal remains (for a recent review, see Larson, 2010;Ryan et al., 2012;Evans et al., 2013;Larson et al., 2014). This faunal assemblage documents a transitional phase in Late Cretaceous ecosystems that preserves the last occurrences of archaic taxa and the earliest representatives of faunas typical of the latest Cretaceous (e.g., Fox, 1968;Larson, 2010). ...
The North American fossil record of dinosaur eggshells for the Cretaceous is primarily restricted to formations of the middle (Albian–Cenomanian) and uppermost (Campanian–Maastrichtian) stages, with a large gap in the record for intermediate stages. Here we describe a dinosaur eggshell assemblage from a formation that represents an intermediate and poorly fossiliferous stage of the Upper Cretaceous, the Santonian Milk River Formation of southern Alberta, Canada. The Milk River eggshell assemblage contains five eggshell taxa: Continuoolithus, Porituberoolithus, Prismatoolithus, Spheroolithus, and Triprismatoolithus. These ootaxa are most similar to those reported from younger Campanian–Maastrichtian formations of the northern Western Interior than they are to ootaxa reported from older middle Cretaceous formations (i.e., predominantly Macroelongatoolithus). Characteristics of the Milk River ootaxa indicate that they are ascribable to at least one ornithopod and four small theropod species. The taxonomic affinity of the eggshell assemblage is consistent with the dinosaur fauna known based on isolated teeth and fragmentary skeletal remains from the formation, although most ornithischians and large theropods are not represented by eggshell. Relative to the Milk River Formation eggshell, similar oospecies occurring in younger Cretaceous deposits tend to be somewhat thicker, which may reflect an increase in body size of various dinosaur lineages during the Late Cretaceous.
... Both species are currently reported from both the upper Campanian Dinosaur Park Formation of the Belly River Group and the younger uppermost Campanian to lower Maastrichtian Horseshoe Canyon Formation of the Edmonton Group (Makovicky et al., 2004;Eberth et al., 2013). This distribution contrasts with the pattern of rapid species turnover and greater taxonomic diversity observed in many other dinosaur clades (e.g., Ryan et al., 2012). ...
A partial ornithomimid skeleton, ROM 1790, from the lower Dinosaur Park Formation (upper Campanian) of Alberta was previously referred to Struthiomimus altus, but lacks diagnostic characters of that species. It is here described as the holotype of a new species, Rativates evadens, gen. et sp. nov., diagnosed by the form of the maxilla-jugal contact, the reduction of the mid-caudal neural spines, the convex fusion of the left and right ischial shafts, the straight-edged distal end of the third metatarsal, and possibly the relatively enlarged medial condyle of the tibia. A histological section of the femur confirms that the type specimen is not a juvenile, despite its relatively small size (approximately 50% the size of large individuals of Struthiomimus altus). Phylogenetic analysis recovers Rativates as a member of a derived ornithomimid clade that includes Ornithomimus, Struthiomimus, and the Asian taxa Anserimimus and Qiupalong. Fusion of the proximal tarsals to the tibia in some ornithomimid specimens was observed to be more complete than previously recognized, increasing the suite of features that these non-avian dinosaurs share homoplastically with birds. http://zoobank.org/urn:lsid:zoobank.org:pub:E0163526-7C26-4E8C-90C9-C72A3E90ED2D SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: McFeeters, B., M. J. Ryan, C. Schröder-Adams, and T. M. Cullen. 2016. A new ornithomimid theropod from the Dinosaur Park Formation of Alberta, Canada. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1221415. 2016
... Mass estimates based on the largest orodromine femur from Dinosaur Park (63 mm; TMP 1979.011.0032) using the method of Anderson et al. (1985) results in an estimate of 13 kg, lower than that for Stegoceras validum (68 mm; UALVP 002) at 16 kg. The orodromines and pachycephalosaurs from the Belly River Group were less than one-tenth the mass of all other known ornithischians in the Dinosaur Park Formation, with the possible exception of Unescoceratops (Ryan et al., 2012). ...
... Fieldwork conducted from 2007 to 2009 in the Milk River Formation by the Royal Ontario Museum and Cleveland Museum of Natural History has resulted in the collection of significant new vertebrate macrofossil material (Larson et al., 2012;Ryan et al., 2012). Additionally, undocumented dinosaur fossils in the collections of the Royal Ontario Museum (collected in 1949 and 1950) and the University of Alberta (collected in 1970 and 1977) have recently been cataloged and prepared. ...
... This suggests some degree of size-sorting of terrestrial organism remains during post-mortem transport: furthermore, it might explain why remains of marine hesperornithiform birds (which presumably lived in and around the water) are more abundant than those of terrestrial dinosaurs. When large animals are excluded from consideration , the composition of the archosaur fauna of the Kristianstad Basin is similar to that of the upper Campanian –lower Maastrichtian dinosaurbearing formations of Canada (Weishampel et al. 2004;Ryan & Evans 2005), which also contain small ornithopods such as Parksosaurus warreni (Parks 1926;Sternberg 1937;Galton 1973;Boyd et al. 2009) and leptoceratopsids (Ryan & Currie 1998) such as Unescoceratops koppelhusae (Ryan et al. 2012). The Upper Cretaceous Wangshi Group of China has also produced leptoceratopsids, specifically Zhuchengceratops inexpectus (Xu et al. 2010), although the only other small ornithischian recovered from these sediments to date is Micropachycephalosaurus hongtuyanensis, a cerapodan of uncertain affinities (Dong 1978;Butler & Zhao 2009). ...
Mesozoic dinosaur fossils are exceptionally rare in Scandinavia. The Swedish record is typically depauperate, with the Kristianstad Basin of Skåne (Scania) yielding all of the known fossils from Swedish Cretaceous strata. Although highly fragmentary, these body remnants are important because they provide evidence of a relatively diverse fauna, including previously recognized hesperornithiform birds and leptoceratopsid ceratopsians, as well as indeterminate ornithopods that are confirmed here for the first time. In this paper, we describe three phalanges (from Åsen) and an incomplete right tibia (from Ugnsmunnarna) from the Kristianstad Basin. One of the phalanges appears to pertain to a leptoceratopsid ceratopsian, providing further evidence of these small ornithischians in the Cretaceous sediments of Sweden. The other two phalanges are interpreted as deriving from small ornithopods similar to Thescelosaurus and Parksosaurus. The tibia appears to represent the first evidence of a non-avian theropod dinosaur in the Cretaceous of Sweden, with a previous report of theropod remains based on fish teeth having been corrected by other authors. The remains described herein provide important additions to the enigmatic dinosaurian fauna that inhabited the Fennoscandian archipelago during the latest Cretaceous.
... The following basal neoceratopsian taxa were analysed: Liaoceratops yanzigouensis, Archaeoceratops yujingziensis, Leptoceratops gracilis and Protoceratops andrewsi (Ryan 2012), with each taxa being successively more derived. Leptoceratops from the family Leptoceratopsidae that includes both Asian and North American forms (You and Dodson 2004). ...
Neoceratopsians (Psittacosauridae and Ceratopsia) exhibit an evolutionary trend in the tooth morphology. Psittacosaurs and basal neoceratopsians are characterized by simple, single-rooted, leaf-shaped teeth in both the maxillae and dentaries that are used primarily for cutting plant material. More derived neoceratopsians (e.g., Leptoceratopsidae) have larger, more complex teeth that show indications of some oral processing by grinding material. The derived Ceratopsidae have complex, double-rooted teeth that are tightly packed into tooth batteries and can be stacked four teeth deep at each alveolar position. This project analysed tooth morphology in the dentaries of both basal neoceratopsians and derived Ceratopsidae to determine if changes in morphology can be quantified between genera, and can be used to distinguish between genera. One dentary each from selected taxa were analyzed to 1) determine if the teeth within the tooth row showed variations in morphology; and, 2) whether variations in morphology could be identified between species. Sampled taxa include Leptoceratops gracilis (Leptoceratopsidae), Protoceratops andrewsi (Protoceratopsidae), Centrosaurus apertus and Styracosaurus albertensis (Ceratopsidae). Several measurements were taken on each dentary tooth including total length, crown height and basal length. Qualitative observations were also taken, when possible. The quantitative data were then used in Principal Component Analyses (PCA) to determine morphological and size variation across individual dentaries and between taxa. Most of the PCA showed signs of size differences between teeth in individual jaws, but no morphology variations could be identified using the measured parameters. Size variations were also identified between taxa. Morphological changes within and between taxa can be assessed qualitatively by visual analysis, but further measurements and study will be required in order to quantify these differences.
... Many North American species have close relatives in Asia, which requires dispersal between the two continents. This pattern is seen in centrosaurine ceratopsids (Xu et al., 2010b), leptoceratopsids (Xu et al., 2010a;Ryan et al., 2012), pachycephalosaurids , saurolophine and lambeosaurine duckbills (Prieto-Márquez, 2010), ankylosaurids (Sullivan, 1999), ornithomimids (Xu et al., 2011), tyrannosaurids (Carr et al., 2011), alvarezsaurs (Longrich and Currie, 2009a), caenagnathids , dromaeosaurs (Longrich and Currie, 2009b) and perhaps alvarezsaurs (Longrich and Currie, 2009a). In particular, current hadrosaur phylogenies require multiple dispersal events to explain their distribution (Prieto-Márquez, 2010). ...
The upper Campanian of the American Southwest has produced dinosaurs that are unknown from the northern Great Plains and vice versa. This has led to the idea that North America's Campanian dinosaur fauna was characterized by high levels of endemism and distinct faunal provinces. Here, two horned dinosaurs known from the Southwest, Pentaceratops and Kosmoceratops, are described from southern Canada. Pentaceratops aquilonius sp. nov. is represented by two frill fragments from the uppermost Dinosaur Park Formation near Manyberries, southeast Alberta. Features shared with Pentaceratops include large, triangular epiparietals, an M-shaped parietal posterior bar, and an epiparietal P1 that curls up and twists laterally. The Manyberries specimens differ from Pentaceratops sternbergii and Utahceratops gettyi in that the posterior bar is broader, emargination is weakly developed, and P1 is directed dorsally, rather than anteriorly. Phylogenetic analysis places P. aquilonius as sister to a clade comprising P. sternbergii and Utahceratops. Kosmoceratops is documented by a partial skull from Dinosaur Provincial Park. Previously referred to Chasmosaurus, the skull exhibits derived features inconsistent with this referral, including a reduced septal flange, a caudally inclined narial strut, a triangular narial process, a reduced frontal fontanelle, a weakly hooked rostral, and a narrow, caudally inclined internal naris. Phylogenetic analysis recovers the animal as sister to Kosmoceratops richardsoni, but differences in the shape of the naris and nasal horn suggest that it likely represents a distinct species. The presence of Pentaceratops and Kosmoceratops in Canada argues against the idea of distinct northern and southern faunal provinces, but the fact that they differ from their southern relatives confirms that endemism was high in the Campanian. The ability of dinosaur lineages to disperse long distances across North America suggests that dinosaur distribution was not constrained by geographic barriers, climate, or flora. Instead, dinosaur endemism may result from competitive exclusion of immigrants by established populations adapted to local environmental conditions.
... Associated fauna. Freshwater gastropods and bivalves, hybodontiforms (Hybodus montanensis), orectolobiforms, rajiforms (Myledaphus tritus), acipenseriforms, aspidorhynchiforms, lepisosteiforms, amiiforms, other intermediate holosteans (Holostean A and B), elopomorphs, osteoglossomorphs, hiodontiforms, albuliforms, esociformes, other intermediate teleosts, albanerpetontids, salamanders, frogs, baenid, macrobaenid, chelydrid, adocid, nanhsiungchelyid, and trionychid turtles, plesiosaurs, choristoderes, lizards, crocodyliforms, ankylosaurs, pachycephalosaurs, ceratopsians, ornithopods, non-avian theropods, birds, and mammals (Currie and Koppelhus 2005;Fox and Naylor 2006;Hilton and Grande 2006;Longrich 2006Longrich , 2008Longrich , 2009Evans et al. , 2009Newbrey et al. 2007;Arbour et al. 2009;Longrich and Currie 2009;Matsumoto and Evans 2010;Ryan et al. 2012;Averianov and Archibald 2013b;Gardner and DeMar 2013;Larson and Currie 2013;Wilson et al. 2013). ...
Citation: Averianov A (2014) Review of taxonomy, geographic distribution, and paleoenvironments of Azhdarchidae (Pterosauria) ZooKeys 432: 1–107. doi: 10.3897/zookeys.432.7913 Abstract The taxonomy, geographic distribution, and paleoenvironmental context of azhdarchid pterosaurs are reviewed. All purported pteranodontid, tapejarid, and azhdarchid specimens from the Cenomanian Kem Kem beds of Morocco are referred to a single azhdarchid taxon, Alanqa saharica. The four proposed autapomorphies of Eurazhdarcho langendorfensis from the lower Maastrichtian Sebeş Formation of Ro-mania are based on misinterpretations of material and this taxon is likely a subjective junior synonym of Hatzegopteryx thambema. Among 54 currently reported azhdarchid occurrences (51 skeletal remains and 3 tracks) 13% are from lacustrine deposits, 17% from fluvial plain deposits, 17% from coastal plain depos-its, 18% from estuarine and lagoonal deposits, and 35% from costal marine deposits. Azhdarchids likely inhabited a variety of environments, but were abundant near large lakes and rivers and most common in nearshore marine paleoenvironments. Copyright Alexander Averianov. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. A peer-reviewed open-access journal
... Ryan et al. 2012), Montanoceratops cerorhynchos and Leptoceratops gracilis. Montanoceratops cerorhynchos is known from one specimen, a braincase, from the upper Tolman Member, with an estimated age of 69.0-69.5 Ma. ...
A high-resolution biostratigraphic analysis of 287 dinosaurian macrofossils and 138 bonebeds in the Edmonton Group (Upper Cretaceous) of southern Alberta provides evidence for at least three dinosaurian assemblage zones in the Horseshoe Canyon Formation (HCFm). From bottom to top the zones comprise unique assemblages of ornithischians and are named as follows: (1) Edmontosaurus regalis – Pachyrhinosaurus canadensis (lower zone); (2) Hypacrosaurus altispinus – Saurolophus osborni (middle zone); and (3) Eotriceratops xerinsularis (upper zone). Whereas the lower and middle zones are well defined and based on abundant specimens, the validity of the uppermost zone (E. xerinsularis) is tentative because it is based on a single specimen and the absence of dinosaur taxa from lower in section. The transition from the lower to the middle zone coincides with the replacement of a warm-and-wet saturated deltaic setting by a cooler, coastal-plain landscape, characterized by seasonal rainfall and better-drained substrates. Whereas changes in rainfall and substrate drainage appear to have influenced the faunal change, changes in mean annual temperature and proximity to shoreline appear to have had little influence on faunal change. We speculate that the
faunal change between the middle and upper zones also resulted from a change in climate, with ornithischian dinosaurs responding to the re-establishment of wetter-and-warmer climates and poorly-drained substrates. Compared with the shorter duration and climatically-consistent dinosaurian assemblage zones in the older Dinosaur Park Formation of southern Alberta, HCFm assemblage zones record long-term morphological stasis in dinosaurs. Furthermore, the coincidence of faunal and paleoenvironmental changes in the HCFm suggest climate-change-driven dinosaur migrations into and out of the region.
... Mass estimates based on the largest orodromine femur from Dinosaur Park (63 mm; TMP 1979.011.0032) using the method of Anderson et al. (1985) results in an estimate of 13 kg, lower than that for Stegoceras validum (68 mm; UALVP 002) at 16 kg. The orodromines and pachycephalosaurs from the Belly River Group were less than one-tenth the mass of all other known ornithischians in the Dinosaur Park Formation, with the possible exception of Unescoceratops (Ryan et al., 2012). ...
Relative to large-bodied dinosaurs, the diversity of small-bodied dinosaurs from the Campanian of North America is poorly understood due to a lack of well-preserved skeletons. We document the first articulated remains, as well as the first cranial bones, of non-iguanodontian ornithopods from the Belly River Group of Alberta. The geologically oldest specimen consists of the posterior half of an articulated skeleton from the middle unit of the Oldman Formation and shares many anatomical features with the contemporaneous Orodromeus makelai and the older Oryctodromeus cubicularis. A second, younger specimen from the upper Oldman Formation is distinct from other ornithopods in having a reduced distal portion of the fibula that is fused to the anterior surface of the tibia; it is designated as the type of a new taxon, Albertadromeus syntarsus, gen. et sp. nov. Numerous isolated elements from small ornithopods from the Dinosaur Park Formation are also identified, but cannot be assigned to the generic level with confidence. Although small-bodied ornithopod material is rare, their known postcranial material outnumbers those of taphonomically equivalent and contemporaneous pachycephalosaurs, which are known to be abundant and diverse due to their robust and frequently recovered cranial domes. These findings suggest considerable undiscovered diversity of small-bodied ornithopods, and highlight biases against the preservation of small taxa in this system.
SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP
Here we report a new articulated skeleton of Yamaceratops dorngobiensis (MPC-D 100/553) from the Khugenetjavkhlant locality at the Shine Us Khudag (Javkhlant Formation, ?Santonian-Campanian) of the eastern Gobi Desert, Mongolia, which represents the first substantially complete skeleton and the first juvenile individual of this taxon. The specimen includes a nearly complete cranium and large portions of the vertebral column and appendicular skeleton. Its skull is about 2/3 the size of the holotype specimen, based on mandibular length. Its juvenile ontogenetic stage is confirmed by multiple indicators of skeletal and morphological immaturity known in ceratopsians, such as the long-grained surface texture on the long bones, the smooth external surface on the postorbital, open neurocentral sutures of all caudal vertebrae, a large orbit relative to the postorbital and jugal, the low angle of the lacrimal ventral ramus relative to the maxillary teeth row, narrow frontal, and straight ventral edge of the dentary. Osteohistological analysis of MPC-D 100/553 recovered three lines of arrested growth, implying around 3 years of age when it died, and verified this specimen’s immature ontogenetic stage. The specimen adds a new autapomorphy of Yamaceratops , the anteroventral margin of the fungiform dorsal end of the lacrimal being excluded from the antorbital fossa. Furthermore, it shows a unique combination of diagnostic features of some other basal neoceratopsians: the ventrally hooked rostral bone as in Aquilops americanus and very tall middle caudal neural spines about or more than four times as high as the centrum as in Koreaceratops hwaseongensis , Montanoceratops cerorhynchus , and Protoceratops andrewsi . The jugal with the subtemporal ramus deeper than the suborbital ramus as in the holotype specimen is also shared with A. americanus , Liaoceratops yanzigouensis , and juvenile P. andrewsi . Adding 38 new scorings into the recent comprehensive data matrix of basal Neoceratopsia and taking into account the ontogenetically variable characters recovered Y. dorngobiensis as the sister taxon to Euceratopsia (Leptoceratopsidae plus Coronosauria). A second phylogenetic analysis with another matrix for Ceratopsia also supported this position. The new phylogenetic position of Y. dorngobiensis is important in ceratopsian evolution, as this taxon represents one of the basalmost neoceratopsians with a broad, thin frill and hyper-elongated middle caudal neural spines while still being bipedal.
Despite an abundance of ornithomimid fossils from the Late Cretaceous of Alberta, Canada, only isolated elements are known from the upper Maastrichtian Scollard Formation. Ornithomimus velox and Struthiomimus sedens are the two taxa recognized from penecontemporaneous formations in the U.S.A., but the incomplete nature of these specimens and the lack of contemporary material from Alberta creates a gap in our understanding of ornithomimid diversity during the late Maastrichtian of North America. Here, I describe the first diagnostic ornithomimid fossils from the upper Maastrichtian Scollard Formation of central Alberta, Canada, providing new information about the taxonomic composition of North American ornithomimids during the late Maastrichtian. The first fossil, an articulated forelimb, exhibits metacarpal ratios and features of the manual unguals that support its referral to the genus Ornithomimus. The second fossil, an associated hind limb, belongs to a large-bodied ornithomimid, and based on characteristics of the pedal unguals is assigned to the genus Struthiomimus. Based on these taxonomic designations, the stratigraphic ranges of both Ornithomimus and Struthiomimus are extended from the upper Campanian Dinosaur Park Formation through to the upper Maastrichtian Scollard Formation of Alberta, which constitutes more than 10 million years of time. These specimens offer new knowledge on the taxonomic composition of ornithomimids in Alberta, but the unusually long stratigraphic range coupled with the difficulty in diagnosing either specimen to species underscores the need for review of North American ornithomimid taxonomy.
The unexpected discovery of non-avian dinosaurs from Arctic and Antarctic settings has generated considerable debate about whether they had the capacity to reproduce at high latitudes—especially the larger-bodied, hypothetically migratory taxa. Evidence for dinosaurian polar reproduction remains very rare, particularly for species that lived at the highest paleolatitudes (>75°). Here we report the discovery of perinatal and very young dinosaurs from the highest known paleolatitude for the clade—the Cretaceous Prince Creek Formation (PCF) of northern Alaska. These data demonstrate Arctic reproduction in a diverse assemblage of large- and small-bodied ornithischian and theropod species. In terms of overall diversity, 70% of the known dinosaurian families, as well as avialans (birds), in the PCF are represented by perinatal individuals, the highest percentage for any North American Cretaceous formation. These findings, coupled with prolonged incubation periods, small neonate sizes, and short reproductive windows suggest most, if not all, PCF dinosaurs were nonmigratory year-round Arctic residents. Notably, we reconstruct an annual chronology of reproductive events for the ornithischian dinosaurs using refined paleoenvironmental/plant phenology data and new insights into dinosaur incubation periods. Seasonal resource limitations due to extended periods of winter darkness and freezing temperatures placed severe constraints on dinosaurian reproduction, development, and maintenance, suggesting these taxa showed polar-specific life history strategies, including endothermy.
An associated incomplete skeleton of a ceratopsid dinosaur from the Campanian deposits of the Allison Member of the Menefee Formation in New Mexico, USA is described. Although it was originally described over two decades ago, newly prepared portions of the Menefee Formation skeleton and reinterpretations of previously known morphology, in addition to newly described specimens have provided new information on ceratopsids, and centrosaurines in particular. These new data allow for a thorough reassessment of the specimen and the erection of a new taxon: Menefeeceratops sealeyi gen. et sp. nov., potentially the oldest recognized member of Centrosaurinae. Menefeeceratops sealeyi is represented by diagnostic cranial and postcranial skeletal elements. The cranial elements include a portion of the left premaxilla, a nearly complete left postorbital horncore, a parietal fragment, the right and left squamosals, the left jugal, the predentary, and the left dentary. Postcranial material consists of two cervical vertebrae, eight dorsal vertebrae, a partial sacrum with six sacral vertebrae, 11 dorsal ribs, the distal left radius, proximal and distal portions of the left ulna, the left femur, and a left metatarsal II. The taxonomic validity of Menefeeceratops sealeyi is supported by a combination of several morphological characters. These include a lack of epiossifications on the lateroposterior edge of the parietal (shared with Machairoceratops), three epiossifications on the squamosal, and three smaller, secondary undulations as part of episquamosal locus S1. There are also two subequal embayments on the posterior free margin of the squamosal with the more dorsal embayment (between episquamosal loci 1 and 2) distinctly larger than the ventral (= lateroventral) one (between episquamosal loci 2 and 3), three ridges on the lateral (dorsolateral) surface of the squamosal, an elongate posterior portion of the squamosal, the presence of a shallow but distinct groove on the medial surface of the squamosal nearly paralleling the ventrolateral and ventroposterior edges, elongate postorbital (= supraorbital) horns that are anteriorly curved distally, and two elongate ridges on the lateral surface of the dentary that diverge anteriorly, creating a distinct anterior triangular fossa. Phylogenetic analysis of Menefeeceratops sealeyi places this new species as a basal centrosaurine, most closely related to Crittendenceratops krzyzanowskii, thus adding to the growing record of centrosaurines discovered in western North America. It thus provides new information about the diversity of morphologies throughout different species and the temporal and paleobiogeographic distribution of these animals throughout Laramidia during the Late Cretaceous. Its presence as one of the, if not the, oldest members of the Centrosaurinae also suggests centrosaurines originated in the southern portions of western North America and the southern Rocky Mountain region, and subsequently radiated north during the upper middle to late Campanian.
Not enough room
Modern carnivore communities include species that span a range of body sizes. For example, on the African savannah, there are small species (mongooses), medium species (wild dogs), and large species (lions). This variation reflects available prey sources that best suit each group. Carnivorous dinosaur communities, however, were missing species that fall into the middle, or mesocarnivore, group as adults. Schroeder et al. looked across communities, space, and time and found that this absence appears to have been driven by the distinctive biology of dinosaurs, in which giant adults start out as tiny hatchlings. Growing juvenile dinosaurs thus filled the other niches and limited trophic species diversity.
Science , this issue p. 941
Morphology forms the most fundamental level of data in vertebrate palaeontology because it is through interpretations of morphology that taxa are identified, creating the basis for broad evolutionary and palaeobiological hypotheses. Assessing maturity is one of the most basic aspects of morphological interpretation and provides the means to study the evolution of ontogenetic changes, population structure and palaeoecology, life‐history strategies, and heterochrony along evolutionary lineages that would otherwise be lost to time. Saurian reptiles (the least‐inclusive clade containing Lepidosauria and Archosauria) have remained an incredibly diverse, numerous, and disparate clade through their ~260‐million‐year history. Because of the great disparity in this group, assessing maturity of saurian reptiles is difficult, fraught with methodological and terminological ambiguity. We compiled a novel database of literature, assembling >900 individual instances of saurian maturity assessment, to examine critically how saurian maturity has been diagnosed. We review the often inexact and inconsistent terminology used in saurian maturity assessment (e.g. ‘juvenile’, ‘mature’) and provide routes for better clarity and cross‐study coherence. We describe the various methods that have been used to assess maturity in every major saurian group, integrating data from both extant and extinct taxa to give a full account of the current state of the field and providing method‐specific pitfalls, best practices, and fruitful directions for future research. We recommend that a new standard subsection, ‘Ontogenetic Assessment’, be added to the Systematic Palaeontology portions of descriptive studies to provide explicit ontogenetic diagnoses with clear criteria. Because the utility of different ontogenetic criteria is highly subclade dependent among saurians, even for widely used methods (e.g. neurocentral suture fusion), we recommend that phylogenetic context, preferably in the form of a phylogenetic bracket, be used to justify the use of a maturity assessment method. Different methods should be used in conjunction as independent lines of evidence when assessing maturity, instead of an ontogenetic diagnosis resting entirely on a single criterion, which is common in the literature. Critically, there is a need for data from extant taxa with well‐represented growth series to be integrated with the fossil record to ground maturity assessments of extinct taxa in well‐constrained, empirically tested methods.
The Cenomanian to Maastrichtian of the Late Cretaceous saw the flooding of the interior of North America by the Western Interior Seaway, which created the eastern landmass of Appalachia and the western landmass of Laramidia. Though Appalachian dinosaur faunas are poorly known, they are nevertheless important for understanding Cretaceous dinosaur paleobiogeography and ecology. In order to better track the vicariance of eastern and western North American dinosaur faunas over the duration of the Cretaceous, the former were compared with the latter from the Aptian to Maastrichtian Stages of the Late Cretaceous using several similarity indices. The data gathered from biogeographic similarity indices suggest that an almost completely homogenous North American dinosaur fauna found in the Early Cretaceous experienced significant vicariance, splitting into a Laramidian fauna differentiated by the presence of ceratopsids, pachycephalosaurids, saurolophids, lambeosaurines, ankylosaurids, therizinosaurids, and troodontids and an Appalachian fauna characterized by the lack of the aforementioned groups and the presence of non-hadrosaurid hadrosauroids, massive hadrosauroids, basal hadrosaurids, leptoceratopsians, “intermediate”-grade tyrannosauroids, and nodosaurids between the Cenomanian and Campanian, with these two faunas later experiencing limited dispersal after the disappearance of the Western Interior Seaway from the American Interior during the Maastrichtian. Dinosaur provincialism and ecology on Appalachia are also investigated and discussed. Though the fossil record of dinosaurs for parts of the Cretaceous is poor throughout North America and in the eastern portion of the continent especially, the analyses herein nevertheless allow for a greater glimpse at dinosaur biogeography and ecology in Appalachia and in North America generally during the time.
The horned Ceratopsidae represent one of the last radiations of dinosaurs, and despite a decade of intense work greatly adding to our understanding of this diversification, their early evolution is still poorly known. Here, two postorbital horncores from the upper Foremost Formation (Campanian) of Alberta are described, and at ∼78.5 Ma represent some of the geologically oldest ceratopsid material. The larger of these specimens is incorporated into a fused supraorbital complex, and preserves a massive, straight, postorbital horncore that is vertical in lateral view, but canted dorsolaterally in rostral view. Medially, the supracranial sinus is composed of a small, restricted caudal chamber, and a large rostral chamber that forms the cornual diverticulum. This morphology is distinct from that of the long-horned Chasmosaurinae, and similar to, but still different from, those of younger Centrosaurinae taxa. The smaller specimen represents an ontogenetically younger individual, and although showing consistent morphology to the larger specimen, is less taxonomically useful. Although not certain, these postorbital horns may be referable to a long-horned basal (i.e., early-branching, non-pachyrhinosaurini, non-centrosaurini) centrosaurine, potentially the contemporaneous Xenoceratops , largely known from the parietosquamosal frill. These specimens indicate the morphology of the supracranial sinus in early, long-horned members of the Ceratopsidae, and add to our understanding of the evolution of the cranial display structures in this iconic dinosaur clade.
Ceratopsians were herbivorous dinosaurs that dominated many of the terrestrial ecosystems in Asia and North America during the Cretaceous. The bizarre variety of skulls and lower jaw morphologies as well as the inferred ecological abundance of many species in this clade indicate that Ceratopsia was a successful group. Here we analyzed 126 lower jaws from 50 ceratopsian species, using two-dimensional geometric morphometrics and finite element analysis to investigate differences in shape and structural performance of this part of the feeding apparatus across Ceratopsia. Morphological differences in lower jaws across ceratopsian clades are said to originate from feeding adaptation. Our results show that the stress (physical loadings modeled in response to biting) in lower jaws was quite similar between “basal” and “derived” taxa, whereas major differences among clades occur for stress values associated with the coronoid process. The basal ceratopsians Hualianceratops and Yinlong had a highly stressed and primitive lower jaw, indicating that those animals may have fed on relatively soft foliage and fruits. A similar condition was found for basal neoceratopsians and protoceratopsids. Psittacosaurids possessed a well-integrated and compact lower jaw able to withstand high stress, at the cost of having a highly stressed coronoid process. Leptoceratopsids were characterized by the opposite condition. Taxa such as Leptoceratops, Prenoceratops, Zhuchengceratops and Cerasinops appear to have had a comparatively efficient feeding apparatus. Ceratopsidae represents the clade with the most efficient masticatory apparatus within Ceratopsia, even if the horizontal ramus of the lower jaw appears less able to withstand high levels of stress as compared with other ceratopsians. Additionally, we found the dentary and surangular–angular complex co-evolved to generate a masticatory apparatus able to withstand high stress, particularly in Protoceratopsidae and Triceratopsini. The major phenotypic evolutionary rate and morphological changes occurred during the mid- to Late Cretaceous, when intense climate change and angiosperm diversification could have affected the evolution of ecological diversity and feeding biomechanics in Ceratopsia.
Psittacosaurus is one of the most specimen-rich dinosaurs known, and the large number of specimens provides a unique opportunity to better understand dinosaurs at the specific level through quantitative statistical analyses as well as qualitative primary description. Intraspecific diversity in dinosaurs is little known as the majority of dinosaurs are based on single, often incomplete specimens. In this dissertation Psittacosaurus is examined using geometric morphometrics, qualitative osteological description, traditional morphometrics, and bone histology. Geometric morphometric analyses demonstrate that taphonomic postmortem distortion drives the location in morphospace of each specimen and obscures true biologic shape, making assessments of intraspecific and ontogenetic variability in P. lujiatunensis difficult. Comparisons with a modern, undeformed dataset show that taphonomic deformation can account for up to 30% of observed shape variation in P. lujiatunensis. These studies demonstrate that taphonomy is a critical factor to consider in geometric morphometric-based studies of shape changes in fossil organisms. I also examine a small monospecific deposit that includes a large Psittacosaurus specimen and twenty-four juveniles, and describe it using osteological, histologic, and taphonomic methods to elucidate morphological and microstructural changes that occur during Psittacosaurus ontogeny as well as determine the burial history of the deposit. Finally, though this particular bonebed assemblage has been interpreted as a possible nesting structure, I provide taphonomic evidence, including petrographic thin sections and x-ray diffraction of the surrounding rock, that suggests that the animals were more likely entombed by a fluvial or lahar flow.
The Late Cretaceous was a time of tremendous global change, as the final stages of the Age of Dinosaurs were shaped by climate and sea level fluctuations and witness to marked paleogeographic and faunal changes, before the end-Cretaceous bolide impact. The terrestrial fossil record of Late Cretaceous Europe is becoming increasingly better understood, based largely on intensive fieldwork over the past two decades, promising new insights into latest Cretaceous faunal evolution. We review the terrestrial Late Cretaceous record from Europe and discuss its importance for understanding the paleogeography, ecology, evolution, and extinction of land-dwelling vertebrates. We review the major Late Cretaceous faunas from Austria, Hungary, France, Spain, Portugal, and Romania, as well as more fragmentary records from elsewhere in Europe. We discuss the paleogeographic background and history of assembly of these faunas, and argue that they are comprised of an endemic ‘core’ supplemented with various immigration waves. These faunas lived on an island archipelago, and we describe how this insular setting led to ecological peculiarities such as low diversity, a preponderance of primitive taxa, and marked changes in morphology (particularly body size dwarfing). We conclude by discussing the importance of the European record in understanding the end-Cretaceous extinction and show that there is no clear evidence that dinosaurs or other groups were undergoing long-term declines in Europe prior to the bolide impact.
The taxonomic history of the Ceratopsia began in 1876 with the description of Monoclonius crassus Cope followed in 1889 by Triceratops horridus Marsh. After a peak of discovery and description in the 1910s and 1920s resulting from the Canadian dinosaur rush in the province of Alberta and the Central Asiatic Expeditions to Mongolia of the American Museum of Natural History, the study of ceratopsians declined to a low level until the 1990s, when discoveries in China, Montana, Utah, Alberta, and elsewhere, abetted by increased biostratigraphic and phylogenetic precision, led to an unprecedented resurgence of activity. Even Richard C. Fox, along with colleagues from Peking University, joined in the activity, by naming Psittacosaurus lujiatunensis. To place the activity in historical perspective, half of all known ceratopsians have been described since 2003. Despite important finds of basal ceratopsians in China, Mongolia, and Korea, North America continues to dominate ceratopsian, especially ceratopsid, diversity.
Taphonomic biases dictate how organisms are represented in the fossil record, but their effect on studies of vertebrate diversity dynamics is poorly studied. In contrast to the high diversity and abundance of small-bodied animals in extant ecosystems, small-bodied dinosaurs are less common than their large-bodied counterparts, but it is unclear whether this reflects unique properties of dinosaurian ecosystems or relates to taphonomic biases. A new, fully domed pachycephalosaurid dinosaur, Acrotholus audeti, from the Santonian of Alberta predates incompletely domed taxa, and provides important new information on pachycephalosaur evolution and the completeness of the ornithischian fossil record. Here we provide the first empirical evidence that the diversity of small-bodied ornithischian dinosaurs is strongly underestimated based on ghost lineages and the high proportion of robust and diagnostic frontoparietal domes compared with other pachycephalosaur fossils. This suggests preservational biases have a confounding role in attempts to decipher vertebrate palaeoecology and diversity dynamics through the Mesozoic.
A new basal neoceratopsian taxon from the eastern Gobi Desert is described. Yamaceratops dorngobiensis, tax. nov., is probably of late Early Cretaceous age, and occupies a phylogenetic position intermediate between Liaoceratops and Archaeoceratops. It is the most basal taxon to display a number of traditional neoceratopsian synapomorphies concentrated in the cheek region and mandible. These include presence of an epijugal, lateral displacement of the coronoid process, a lateral ridge on the surangular for insertion of the jaw adductors, and a lateral wall to the mandibular glenoid. Yamaceratops shares two synapomorphies (tubercles on the ventral edge of the angular and shape of the jugal) with Liaoceratops, indicating that the transient presence of derived characters may be prevalent in the early evolutionary history of Ceratopsia. Yamaceratops shares aspects of frill morphology with Liaoceratops and Leptoceratops that suggest a function unrelated to display for this anatomical structure in basal neoceratopsians, and hints at a more complex evolutionary history for ceratopsian frills. Considerations of patristic distances and mosaic evolution among basal neoceratopsian taxa indicate that a greater diversity of these animals remains undiscovered.
The age of the nonmarine Two Medicine Formation of northwestern Montana is currently based upon correlations with K-Ar-dated Western Interior ammonite zones. Ar-40/Ar-39 dating of biotite and plagioclase separated from four bentonites and one crystal-rich tuff permits for the first time direct determination of the age of Two Medicine strata. Biotite and plagioclase from a bentonite 10 m below the top of the Two Medicine Formation yield concordant Ar-40/Ar-39 ages of 74 Ma, while biotite and plagioclase from two bentonites and a crystal-rich tuff from approximately 100 m above the base of the formation cluster in age around 80 Ma. The total duration of Two Medicine deposition is estimated using these new radio-isotopic ages via extrapolation of an average rock accumulation rate. The new Ar-40/Ar-39 ages facilitate regional correlation of the dinosaur-dominated paleofauna recovered from the Two Medicine Formation, and help constrain the timing of the Claggett and Bearpaw transgressions. The ages support correlation of the richly fossiliferous upper lithofacies suite of the Two Medicine Formation with exposures of the Judith River Formation in Dinosaur Provincial Park, Alberta, Canada. Radioisotopically dated exposures of the Judith River Formation within Montana that include important Judithian ''age'' mammal localities correlate approximately with middle and lower parts of the middle lidiofacies suite of the Two Medicine Formation. The new Ar-40/Ar-39 ages further indicate that the transgressions of the Claggett and Bearpaw seas culminated within northwestern Montana at ca. 79.6 and 74.0 Ma, respectively.
The Late Cretaceous of Alberta preserves one of the most complete records of fossil turtles within a single geographic area in North America. The Cenomanian Dunvegan Formation contains the earliest record of the family Trionychidae in North America. The Santonian Milk River Formation contains a minimum of ten taxa with Adocus, a small trionychid, and a member of the Solemydidae being the most abundant. Diversity remains high in the mid-Campanian Judith River Group. The solemyidid last occurs in the basal beds of the Judith River Group. A member of the Macrobaenidae first occurs in the Dinosaur Park Formation, the uppermost formation in the Judith River Group. Turtles diversity is low in the late Campanian lower Horseshoe Canyon Formation, and they are absent in the early Maastrichtian upper Horseshoe Canyon Formation. Diversity increases in the late Maastrichtian Scollard Formation, although it is much less than in the contemporaneous Hell Creek Formation of Montana. Two of the taxa present in the Scollard Formation, Compsemys and Plastomenus, occur in late Campanian or early Maastrichtian formations in more southerly areas of North America. The changes in turtle diversity through the Campanian and Maastrichtian are interpreted as a result of shifts in a latitudinal turtle diversity gradient resulting from changes in climate. Based on this interpretation a decrease in temperature from the mid-Campanian to early Maastrichtian, followed by a rapid increase at the beginning of the late Maastrichtian is supported.
The ceratopsians represent one of the last dinosaurian radiations. Traditionally the only universally accepted speciose clade within the group was the Ceratopsidae. However, recent discoveries and phylogenetic analyses have led to the recognition of a new speciose clade, the Leptoceratopsidae, which is predominantly known from the Upper Cretaceous of North America.
Here we report a new leptoceratopsid taxon, Zhuchengceratops inexpectus gen. et sp. nov., based on a partial, articulated skeleton recovered from the Upper Cretaceous Wangshi Group of Zhucheng, Shandong Province, China. Although Zhuchengceratops is significantly different from other known leptoceratopsids, it is recovered as a derived member of the group by our phylogenetic analysis. Furthermore, Zhuchengceratops exhibits several features previously unknown in leptoceratopsids but seen in ceratopsids and their close relatives, suggesting that the distribution of morphological features within ceratopsians is more complex than previously realized.
The discovery of Zhuchengceratops increases both the taxonomic diversity and the morphological disparity of the Leptoceratopsidae, providing further support for the hypothesis that this clade represents a successful radiation of horned dinosaurs in parallel with the Ceratopsidae in the Late Cretaceous. This documents a surprising case of the coexistence and radiation of two closely-related lineages with contrasting suites of jaw and dental features that probably reflect adaptation to different food resources.
A new genus and species of horned dinosaurs, Udanoceratops tschizhovi, characterized mainly by very large size and the lack of a horn on its nasal bones is described. Data on the phylogenetic relationships of Udanoceratops are presented. -Journal summary
This systematic palaeontology describes isolated dinosaur teeth from the last twenty million years of the Late Cretaceous in South Alberta, Canada. The material was obtained by screenwashing vertebrate microfossil localities. For the first time, dinosaur teeth are described with the palaeo-biological range of variability that is present in every population. A second range of variability that occurs between different formations is taken into account. In total the tooth morphology of 12 dinosaurian taxa is described on the basis of over 5000 isolated teeth. The measurements of the most complete specimens of a taxon are put into diagrams to show ranges of variability. A morphological divergence throughout time is documented for the genus Saurornitholestes and the species Richardoestesia gilmorei. Both taxa are indistinguishable in the lower portion of the studied sequence, but subsequently differ in later formations.
Approximately half of existing dinosaur species belonging to the Order Ornithischia, or the 'bird-hipped' dinosaurs, which include such familiar forms as the stegosaurs, ankylosaurs, hadrosaurs, and ceratopsids. Although ornithischians are generally conceded to have descended from a common ancestor, little is known about the pattern of descent. Comparison of more recently discovered ornithischian fossils from China and Mongolia to better-known North American forms has shed light on the pattern of evolutionary diversification among ornithischians, a pattern that began approximately 200 My ago and ended abruptly nearly 140 My later at the end of the Cretaceous.-from Author
Protoceratopsians are best known in North America from associated skeletal material of Montanoceratops from the early Maastrichtian of Montana and Campanian of Alberta and Leptoceratops from the late Maastrichtian of Alberta and Wyoming. We report here the first occurrence of protoceratopsian elements from the middle Campanian (Dinosaur Park Formation) of Alberta. The specimens consist of a fragmentary right dentary and an almost complete left dentary which can be referred to Leptoceratops sp. Recent examination of Albertan microvertebrate material has identified cf. protoceratopsians teeth from the latest Santonian (Milk River Formation), extending the record of Albertan protoceratopsians back almost 20 million years. The rarity of these small ornithischians in the fossil record of Alberta may have been due to ecological exclusion from the wet, coastal environments that were preferred by the larger, more abundant ceratopsids.
— We studied sequence variation in 16S rDNA in 204 individuals from 37 populations of the land snail Candidula unifasciata (Poiret 1801) across the core species range in France, Switzerland, and Germany. Phylogeographic, nested clade, and coalescence analyses were used to elucidate the species evolutionary history. The study revealed the presence of two major evolutionary lineages that evolved in separate refuges in southeast France as result of previous fragmentation during the Pleistocene. Applying a recent extension of the nested clade analysis (Templeton 2001), we inferred that range expansions along river valleys in independent corridors to the north led eventually to a secondary contact zone of the major clades around the Geneva Basin. There is evidence supporting the idea that the formation of the secondary contact zone and the colonization of Germany might be postglacial events. The phylogeographic history inferred for C. unifasciata differs from general biogeographic patterns of postglacial colonization previously identified for other taxa, and it might represent a common model for species with restricted dispersal.
Three classifications of the Dinosauria have been proposed, which differ from each other in the principles on which their authors proposed to make the divisions. First in time is Professor Cope’s classification (‘Philadelphia, Acad. Nat. Sci. Proc.,’ November 13th, 1866, and December 31st, 1867; ‘Amer. Phil. Soc. Trans.,’ vol. 14, Part I). He relied upon the characters of the tarsus and the ilium; and on their varied condition divided Dinosaurs into three orders named Orthopoda, Goniopoda, and Symphopoda. In the Orthopoda , the generic types associated are Scelidosaurus, Hylæosaurus, Iguanodon, and Hadrosaurus. And in this group the relations of the tibia and fibula are compared to those of modern Lizards, the proximal tarsals being distinct from each other and from the tibia. The ilium has a narrowed anterior prolongation.
Basal (cladistically) neoceratopsians are relatively small, gracile members of Ceratopsia (‘horned” dinosaurs), which also includes larger forms such as Triceratops and Centrosaurus. The Asian basal neoceratopsians share some very important traits not found in any North American group until now, including a fenestrated frill and premaxillary teeth. Likewise, the North American basal taxa have some traits not found in the Asian forms, the most important of which is a very specialized tooth wear pattern. Cerasinops hodgskissi, a new basal neoceratopsian from the Lower Two Medicine River Formation of Montana, exhibits all of the above characters along with others previously found on only one of the two continents. The new species is a sister group to Leptoceratopsidae in a cladistic analysis, and is a link between the taxa on the two continents. Cerasinops also exhibits extremely interesting anatomical and histological features that indicate the possibility of bipedality in this taxon, a locomotor pattern not found previously in basal neoceratopsians (it has been suggested in some, but with little evidence).
Montanoceratops cerorhynchus has been described as the sister group of Ceratopsidae, even though analyses and diagnosis of this taxon have been tentative and incomplete. A second specimen of M. cerorhynchus includes new diagnostic elements, most notably a partial skull including the caudal half of the braincase, pectoral girdle and manus. Results of a cladistic analysis of eight basal neoceratopsians (Protoceratops, Leptoceratops, Bagaceratops, Microceratops, Breviceratops, Montanoceratops, Asiaceratops, and Udanoceratops) and four ceratopsids (Centrosaurus, Anchiceratops, Chasmosaurus, and Styracosaurus) confirm Montanoceratops as the sister group of Ceratopsidae. Microceratops and Asiaceratops are positioned at the base of Neoceratopsia. Protoceratops, Leptoceratops, and Udanoceratops constitute a monophyletic Protoceratopsidae. Paleogeographical interpretation of the cladogram suggests that Neoceratopsia originated in Asia, and that there were at least two migrations of ceratopsians from Asia to North America.
A skeletal reconstruction of the small protoceratopsian dinosaur Leptoceratops gracilis from the latest Cretaceous of Alberta is presented. Leptoceratops has a greater number of presacral vertebrae than in other known protoceratopsids, and the presacral vertebral count is recognized to be somewhat variable in ceratopsids as well. Psittacosaurids, protoceratopsids, and ceratopsids represent distinct lineages of the same general group of ornithischian dinosaurs.
The lambeosaurine hadrosaurid Parasaurolophus is known from rare occurrences in Campanian deposits of western North America. A previously undescribed large hadrosaurid braincase from the Dinosaur Park Formation (Alberta, Canada) is assigned to the genus Parasaurolophus on the basis of several derived characters associated with the frontal- nasal articulation at the base of the crest. This identification is supported by two separate phylogenetic analyses, in which the specimen clusters with other more completely known Parasaurolophus exemplars. If correctly identified, the specimen represents the third and largest cranial specimen of the genus from the Late Cretaceous of Alberta. The specimen occurs in the same deposits as the holotype specimen of Parasaurolophus walkeri and may represent a late ontogenetic stage of this taxon. As opposed to a small frontal dome in the holotype of P. walkeri, the external contribution of the frontal to the skull roof is obliterated in the new specimen. If these hypothesized ontogenetic changes in the skull roof correlate with the size and posterodorsal development of the crest, as in other lambeosaurines, it suggests that the crest had not reached its full expression in the holotype. When placed into a detailed biostratigraphic context for the first time, the limited Parasaurolophus material from the Belly River Group is distributed in the lower half of the Dinosaur Park Formation at Dinosaur Provincial Park. This suggests that Parasaurolophus may be associated with the lower Centrosaurus-Corythosaurus assemblage zone and may have preferred more inland environments than other hadrosaurids, such as Lambeosaurus and Prosaurolophus.
The first detailed description of the lambeosaurine Lambeosaurus magnicristatus (Ornithischia: Hadrosauridae) confirms that it is a distinct taxon characterized by its comparatively enormous cranial crest, formed predominantly by the caudodorsal process of the premaxilla, and an acute crest-snout angle. The holotype of L. magnicristatus occurs stratigraphically higher than all other Dinosaur Park Formation lambeosaurines at the Dinosaur Provincial Park locality. The only referred specimen was collected over 170 kilometers southeast of the type locality. Correlation of its host stratum with the well-known Dinosaur Park section reveals that L. magnicristatus has no biostratigraphic overlap with L. lambei and suggests that it replaces L. lambei on a regional scale in southern Alberta at the end of ‘Dinosaur Park time.’ Species-level phylogenetic analysis of Lambeosaurinae corroborates the monophyly of Lambeosaurus. The genus is characterized by five apomorphies, including a procumbent crest, complete enclosure of the ophthalmic canal of the laterosphenoid, the presence of a flange on the caudodorsal process of the premaxilla that overlaps the nasal in the rostral region of the crest, caudal extension of the premaxilla such that it forms the caudal margin of the crest, and a unique joint between the rostral nasal and the caudodorsal process of the premaxilla. Lambeosaurine phylogeny indicates that the development of a hypertrophied cranial crest evolved independently at least three times within the clade, suggesting that the crest enlargement is a recurring evolutionary trend within Lambeosaurinae.
A new basal neoceratopsian genus and species, Prenoceratops pieganensis, is described from the Two Medicine Formation of Montana. This material represents the only bone-bed deposition of a basal neoceratopsian currently known, and in addition is almost entirely disarticulated allowing for a more thorough understanding of basal neoceratopsian cranial morphology. The new taxon is characterized by a lower, more sloping head than in Leptoceratops, with a nasal that is pinched caudally, a wide, triangular jugal, extremely gracile surangular, and reduced articular among other autapomorphies. A preliminary cladistic analysis unites Prenoceratops firmly with the other North American basal neoceratopsians (and one Asian taxon) in the clade Leptoceratopsidae.
In 2008, a new basal neoceratopsian was discovered in the Tando beds (Albian) of Tando Basin in South Korea. It represents the first ceratopsian dinosaur in the Korean peninsula and is assigned to Koreaceratops hwaseongensis gen. et sp. nov. Autapomorphies of Koreaceratops include very tall neural spines over five times higher than the associated centra in the distal caudals, and a unique astragalus divided into two fossae by a prominent craniocaudal ridge on the proximal surface. A phylogenetic analysis indicates that Koreaceratops is positioned between Archaeoceratops and all more derived neoceratopsians, and the elongation of caudal neural spines was an important derived character in non-ceratopsid neoceratopsians. The very tall caudal neural spines in Koreaceratops, Montanoceratops, Udanoceratops, Protoceratops, and Bagaceratops appear to be homoplasious, suggesting an independent adaptation, possibly for swimming. Skeletal evidence suggests that obligate quadrupedalism occurred gradually in neoceratopsians progressing from bipedal through facultative quadrupedalism, to complete quadrupedalism in Coronosauria.
A redescription of the Montanoceratops cerorhynchus holotype, with a review of referred material
- P J Makovicky
Makovicky, P.J., 2010. A redescription of the Montanoceratops cerorhynchus holotype, with a review of referred material. In: Ryan, M.J., Chinnery-Allgeier, B.J.,
Eberth, D.A. (Eds.), New Perspectives on Horned Dinosaurs. Indiana University
Press, Bloomington, IN, pp. 68e82.
A Montanoceratops cerorhynchus (Dinosauria: Ceratopsia) braincase from the Horseshoe Canyon Formation of Alberta
- P J Makovicky
Makovicky, P.J., 2001. A Montanoceratops cerorhynchus (Dinosauria: Ceratopsia)
braincase from the Horseshoe Canyon Formation of Alberta. In: Tanke, D.H.,
Carpenter, K., Skrepnick, M.W. (Eds.), Mesozoic Vertebrate Life, New Research
Inspired by the Paleontology of Philip J. Currie. Indiana University Press,
Bloomington, IN, pp. 243e262.
The geology Dinosaur Provincial Park e A Spectacular Ancient Ecosystem Revealed
- D A Eberth
Eberth, D.A., 2005. The geology. In: Currie, P.J., Koppelhus, E.B. (Eds.), Dinosaur Provincial Park e A Spectacular Ancient Ecosystem Revealed. Indiana University Press, Bloomington, IN, pp. 54e82. Eberth, D.A., Deino, A.A., 1992. Geochronology of the Nonmarine Judith River Formation of Southern Alberta, Society of Economic Paleontologists and M.J. Ryan et al. / Cretaceous Research 35 (2012) 69e80
69e80 150 and 151 could be coded for the dentaries; 95e106 could be coded for the teeth. The final data matrix consisted of 151 characters scored for 26 ingroup taxa and two outgroup taxa
- M J Ryan
M.J. Ryan et al. / Cretaceous Research 35 (2012) 69e80 150 and 151 could be coded for the dentaries; 95e106 could be coded for the teeth. The final data matrix consisted of 151 characters scored for 26 ingroup taxa and two outgroup taxa, following Makovicky (2010).
Theme meeting, Mesozoic of the Western Interior, Fort Collins, Abstracts with programs
- Mineralogists
Mineralogists, 1992, Theme meeting, Mesozoic of the Western Interior, Fort
Collins, Abstracts with programs, p. 24.
Geochronology of the Nonmarine Judith River Formation of Southern Alberta
- D A Eberth
- A A Deino
Eberth, D.A., Deino, A.A., 1992. Geochronology of the Nonmarine Judith River
Formation of Southern Alberta, Society of Economic Paleontologists and
Bones and rocks of the Upper Cretaceous Two Medicine-Judith River clastic wedge complex
- J R Horner
- J G Schmitt
- F Jackson
- R Hanna
Horner, J.R., Schmitt, J.G., Jackson, F., Hanna, R., 2001. Bones and rocks of the Upper
Cretaceous Two Medicine-Judith River clastic wedge complex, Montana. In:
Hill, C.L. (Ed.), Guidebook for the Field Trips of the Society of Vertebrate
Paleontology 61st Annual Meeting: Mesozoic and Cenozoic Paleontology in the
Western Plains and Rocky Mountains. Museum of the Rockies, Occasional Paper
3, 3e13.
The geographic and stratigraphic distribution of articulated and associated dinosaur remains
- P J Currie
- D A Russell
Currie, P.J., Russell, D.A., 2005. The geographic and stratigraphic distribution of
articulated and associated dinosaur remains. In: Currie, P.J., Koppelhus, E.B.
(Eds.), Dinosaur Provincial Park e A Spectacular Ancient Ecosystem Revealed.
Indiana University Press, Bloomington, IN, pp. 537e567.
A new species of Pachyrhinosaurus (Dinosauria, Ceratopsidae) from the Upper Cretaceous of Alberta, Canada A New Horned Dinosaur from an Upper Cretaceous Bone Bed in Alberta
- P J Currie
- W Langston
- Jr
- D H Tanke
Currie, P.J., Langston, W., Jr., Tanke, D.H., 2008. A new species of Pachyrhinosaurus
(Dinosauria, Ceratopsidae) from the Upper Cretaceous of Alberta, Canada. In:
Currie, P.J., Langston, W., Jr., Tanke, D.H. (Eds.), A New Horned Dinosaur from an
Upper Cretaceous Bone Bed in Alberta, Canada. National Research Council Press,
Ottawa, 108 pp.
Dinosaur Provincial Park e A Spectacular Ancient Ecosystem Revealed
- D A Eberth
Eberth, D.A., 2005. The geology. In: Currie, P.J., Koppelhus, E.B. (Eds.), Dinosaur
Provincial Park e A Spectacular Ancient Ecosystem Revealed. Indiana University
Press, Bloomington, IN, pp. 54e82.