Latirhinus uitstlani,a ‘broad-nosed’ saurolophine hadrosaurid (Dinosauria,Ornithopoda) from the late Campanian (Cretaceous) of northern Mexico

We describe a new genus and species of hadrosaurid dinosaur, Latirhinus uitstlani, from upper Campanian strata of the Cerro del Pueblo Formation in northern Mexico. The new taxon differs from other hadrosaurids, except Gryposaurus, in possessing a deep and arcuate dorsal process of the nasal; it differs from Gryposaurus, as well as from all other saurolophines, in having a broader narial foramen, and an anterodorsally curved deltoid crest of the scapula (convergent with Lambeosaurinae within the context of Hadrosauridae). L. uitstlani appears to be allied to ‘kritosaurs’, particularly to species of Gryposaurus, and it represents one of the southernmost saurolophines of North America. Likewise, L. uitstlani adds to the diversity of saurolophines in the southern Western Interior Basin and its occurrence in northern Mexico is consistent with the apparent predominance of ‘kritosaurs’ in southern Laramidia during late Campanian times.     

A Re-Evaluation of the Chasmosaurine Ceratopsid Genus Chasmosaurus (Dinosauria: Ornithischia) from the Upper Cretaceous (Campanian) Dinosaur Park Formation of Western Canada

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.     

A New Large-Bodied Oviraptorosaurian Theropod Dinosaur from the Latest Cretaceous of Western North America

The oviraptorosaurian theropod dinosaur clade Caenagnathidae has long been enigmatic due to the incomplete nature of nearly all described fossils. Here we describe Anzu wyliei gen. et sp. nov., a new taxon of large-bodied caenagnathid based primarily on three well-preserved partial skeletons. The specimens were recovered from the uppermost Cretaceous (upper Maastrichtian) Hell Creek Formation of North and South Dakota, and are therefore among the stratigraphically youngest known oviraptorosaurian remains. Collectively, the fossils include elements from most regions of the skeleton, providing a wealth of information on the osteology and evolutionary relationships of Caenagnathidae. Phylogenetic analysis reaffirms caenagnathid monophyly, and indicates that Anzu is most closely related to Caenagnathus collinsi, a taxon that is definitively known only from a mandible from the Campanian Dinosaur Park Formation of Alberta. The problematic oviraptorosaurs Microvenator and Gigantoraptor are recovered as basal caenagnathids, as has previously been suggested. Anzu and other caenagnathids may have favored well-watered floodplain settings over channel margins, and were probably ecological generalists that fed upon vegetation, small animals, and perhaps eggs.     

Skull Ecomorphology of Megaherbivorous Dinosaurs from the Dinosaur Park Formation (Upper Campanian) of Alberta,Canada

Megaherbivorous dinosaur coexistence on the Late Cretaceous island continent of Laramidia has long puzzled researchers, owing to the mystery of how so many large herbivores (6–8 sympatric species, in many instances) could coexist on such a small (4–7 million km²) landmass. Various explanations have been put forth, one of which–dietary niche partitioning–forms the focus of this study. Here, we apply traditional morphometric methods to the skulls of megaherbivorous dinosaurs from the Dinosaur Park Formation (upper Campanian) of Alberta to infer the ecomorphology of these animals and to test the niche partitioning hypothesis. We find evidence for niche partitioning not only among contemporaneous ankylosaurs, ceratopsids, and hadrosaurids, but also within these clades at the family and subfamily levels. Consubfamilial ceratopsids and hadrosaurids differ insignificantly in their inferred ecomorphologies, which may explain why they rarely overlap stratigraphically: interspecific competition prevented their coexistence.     

A new basal ornithopod dinosaur (Frenchman Formation,Saskatchewan, Canada), and implications for late Maastrichtian ornithischian diversity in North America

A small, articulated basal ornithopod skeleton from the Frenchman Formation (late Maastrichtian) of Saskatchewan (RSM P 1225.1), previously referred to the taxon Thescelosaurus, differs from both recognized species of this taxon (Thescelosaurus neglectus and Thescelosaurus garbanii). The differences are taxonomically informative and we recognize this specimen as the holotype of a new species, Thescelosaurus assiniboiensis sp. nov. , diagnosed by the presence of two autapomorphies, and displaying plesiomorphic traits more similar to those of Parksosaurus, than to those of the other Thescelosaurus species. The Frenchman Formation also harbours an intriguing faunal assemblage in which Thescelosaurus represents one of the most abundant dinosaur taxa, and preserves a relatively high proportion of small (putatively juvenile and subadult) specimens of many dinosaur taxa. Further work that increases the faunal sample from this formation, and that permits quantitative comparisons with contemporary formations, will determine whether or not these differences are well supported, and will determine their ultimate palaeobiological significance. Identification of a third species of Thescelosaurus from the late Maastrichtian of North America suggests that this taxon was more diverse than previously recognized, and shows an increase in diversity from the Campanian through the late Maastrichtian, contrasting the trends seen in most other ornithischian clades. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163 , 1157–1198.     

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

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

A New Brachylophosaurin Hadrosaur (Dinosauria: Ornithischia) with an Intermediate Nasal Crest from the Campanian Judith River Formation of Northcentral Montana

Background

Brachylophosaurini is a clade of hadrosaurine dinosaurs currently known from the Campanian (Late Cretaceous) of North America. Its members include: Acristavus gagslarsoni, which lacks a nasal crest; Brachylophosaurus canadensis, which possesses a flat paddle-shaped nasal crest projecting posteriorly over the dorsal skull roof; and Maiasaura peeblesorum, which possesses a dorsally-projecting nasofrontal crest. Acristavus, from the lower Two Medicine Formation of Montana (~81–80 Ma), is hypothesized to be the ancestral member of the clade. Brachylophosaurus specimens are from the middle Oldman Formation of Alberta and equivalent beds in the Judith River Formation of Montana; the upper Oldman Formation is dated 77.8 Ma.

Methodology/Principal Findings

A new brachylophosaurin hadrosaur, Probrachylophosaurus bergei (gen. et sp. nov.) is described and phylogenetically analyzed based on the skull and postcranium of a large individual from the Judith River Formation of northcentral Montana (79.8–79.5 Ma); the horizon is equivalent to the lower Oldman Formation of Alberta. Cranial morphology of Probrachylophosaurus, most notably the nasal crest, is intermediate between Acristavus and Brachylophosaurus. In Brachylophosaurus, the nasal crest lengthens and flattens ontogenetically, covering the supratemporal fenestrae in large adults. The smaller nasal crest of Probrachylophosaurus is strongly triangular in cross section and only minimally overhangs the supratemporal fenestrae, similar to an ontogenetically earlier stage of Brachylophosaurus. Sutural fusion and tibial osteohistology reveal that the holotype of Probrachylophosaurus was relatively more mature than a similarly large Brachylophosaurus specimen; thus, Probrachylophosaurus is not simply an immature Brachylophosaurus.

Conclusions/Significance

The small triangular posteriorly oriented nasal crest of Probrachylophosaurus is proposed to represent a transitional nasal morphology between that of a non-crested ancestor such as Acristavus and the large flat posteriorly oriented nasal crest of adult Brachylophosaurus. Because Probrachylophosaurus is stratigraphically and morphologically intermediate between these taxa, Probrachylophosaurus is hypothesized to be an intermediate member of the Acristavus-Brachylophosaurus evolutionary lineage.     

A tyrannosaur jaw bitten by a confamilial: scavenging or fatal agonism?

Bell, P.R. & Currie, P.J. 2009: A tyrannosaur jaw bitten by a confamilial: scavenging or fatal agonism?. Lethaia, Vol. 43, pp. 278–281. A partial dentary of an adult tyrannosaur from the Dinosaur Park Formation of Alberta, Canada, preserves the embedded tooth of another tyrannosaur within the bone. The specimen’s incompleteness precludes generic identification of either the jaw or the embedded tooth, although Gorgosaurus and/or Daspletosaurus are most likely given the stratigraphic position. The absence of healing around the lesion indicates the bite took place either post‐mortem or within weeks prior to the death of this animal. A post‐mortem bite can be explained by confamilial or cannibalistic scavenging. Alternatively, the bite would represent a perimortem instance of intrafamilial aggression that may have resulted in the death of that animal. An estimated 6053N of bite force was required to produce the bite mark. This specimen provides the best evidence for aggressive peri‐ or post‐mortem confamilial interaction among tyrannosaurs and corroborates previous studies based on inferred tooth marks. □Alberta, behaviour, Campanian, Cretaceous, Dinosaur Park Formation, Theropoda, Tyrannosauridae.     

A NEW, LARGE ORNITHOMIMID FROM THE CRETACEOUS DINOSAUR PARK FORMATION OF ALBERTA, CANADA: IMPLICATIONS FOR THE STUDY OF DISSOCIATED DINOSAUR REMAINS

Abstract:  Only two ornithomimid genera, Ornithomimus and Struthiomimus , are currently known from the Upper Cretaceous of North America. However, a number of ornithomimid elements from Alberta's Dinosaur Park Formation (Upper Campanian), cannot be assigned to either Ornithomimus or Struthiomimus . These bones, including a frontal, caudal vertebrae, and unguals of the manus and the pes, come from animals significantly larger than any previously known Judithian ornithomimid. The frontal exhibits several unusual features, including transverse expansion over the prefrontals, and extreme reduction of the supratemporal fossae. Caudal vertebrae are characterized by neural arches that are posteriorly shifted and transversely expanded. Manual unguals possess a highly concave articular surface, a flexor tubercle divided by a sulcus, and a broad claw. Pedal unguals display highly concave articular surfaces, and a ridge-like flexor tubercle dividing a deep ventral fossa. Although it is difficult to know whether these elements represent a single taxon, this is currently the most parsimonious hypothesis. This study demonstrates how isolated dinosaur bones can extend our knowledge of dinosaur faunas.     

A remarkable hollow-crested hadrosaur from Russia: an Asian origin for lambeosaurines

The nearly complete skeleton of a new lambeosaurine dinosaur, Olorotitan arharensis, has been discovered in the Maastrichtian Tsagayan Formation at Kundur, Far Eastern Russia. This is the most complete dinosaur skeleton ever discovered in Russia and, with its finely preserved supracranial crest, the most complete lambeosaurine outside North America. This new taxon is remarkable by the unusual shape of its hollow crest and by the important elongation of its neck and of its sacrum. An additional articulation between adjacent neural spines made the proximal third of the tail rigid, but it cannot be excluded that it is a pathological feature. Phylogenetic analysis shows that Olorotitan is the sister-taxon of the North American genera Corythosaurus and Hypacrosaurus. Lambeosaurines originated from Asia and then migrated to North America before or at the beginning of the Late Campanian. To cite this article: P. Godefroit et al., C. R. Palevol 2 (2003) 143–151.     

Description of a new long‐snouted beaked whale from the Late Miocene of Denmark: evolution of suction feeding and sexual dimorphism in the Ziphiidae (Cetacea: Odontoceti)

A new genus and species of Ziphiidae, Dagonodum mojnum gen. nov., sp. nov., from the upper Miocene Gram Formation (c. 9.9–7.2 Ma) represents the first occurrence of the family in Denmark. This long‐snouted ziphiid is characterized by two pairs of mandibular tusks, the Eustachian outlet that approximately levels with the dorsalmost margin of the posterior portion of the involucrum, and the left trapezoid nasal with a posteromedial projection into the frontal. A phylogenetic analysis including 25 species and 69 characters was conducted. Dagonodum mojnum is placed in a basal ziphiid clade as the sister taxon of Messapicetus. The specimen is probably a male, because it has enlarged tusks. Alternatively, females could also be involved in fights and develop erupted tusks as in the extant Berardius. Although less well supported, this interpretation proposes that aggressive interactions were not restricted to males in stem‐ziphiids. With a thickened thyrohyal and the presence of a precoronoid crest, D. mojnum was able to use suction feeding, but was less specialized to it compared to extant ziphiids. The elongated neck of D. mojnum less optimized to perform deep dives, and the shallow depth at which the Gram Formation was deposited corroborates the hypothesis that at least part of the stem‐ziphiids were not regular deep divers.     

A new kinosternoid from the Late Cretaceous Hell Creek Formation of North Dakota and Montana and the origin of the <Emphasis Type="Italic">Dermatemys mawii</Emphasis> lineage

A nearly complete turtle shell from the Late Cretaceous (Maastrichtian) Hell Creek Formation of Slope County, North Dakota, represents the most complete remains to date of a Mesozoic kinosternoid turtle and a new species, Hoplochelys clark nov. sp. The new taxon is diagnosable from other representatives of Hoplochelys by the plesiomorphic placement of the humeral/femoral sulcus behind the hyo/hypoplastral suture and the autapomorphic development of an interrupted median (neural) keel. All six previously named Paleocene (Puercan and Torrejonian) representatives of Hoplochelys lack diagnostic characters and are synonymized as Hoplochelys crassa. A phylogenetic analysis reveals that Hoplochelys spp. and Agomphus pectoralis are most parsimoniously placed within Kinosternoidea along the phylogenetic stem of the extant Mesoamerican River Turtle Dermatemys mawii, extending that taxon’s stem lineage from the early Eocene to the late Maastrichtian. The two primary crown lineages of Kinosternoidea are thus known from the Mesozoic and split prior to the late Campanian. The presence of a thickened cruciform plastron, true costiform processes, only three inframarginals, and the reduction of the medial contact of the abdominals are synapomorphies of Chelydroidea, the clade formed by Chelydridae and Kinosternoidae.     

Skull shapes of the Lissodelphininae: radiation,adaptation and asymmetry

Within Delphinidae, the sub‐family Lissodelphininae consists of 8 Southern Ocean species and 2 North Pacific species. Lissodelphininae is a result of recent phylogenetic revisions based on molecular methods. Thus, morphological radiation within the taxon has not been investigated previously. The sub‐family consists of ecologically diverse groups such as (1) the Cephalorhynchus genus of 4 small species inhabiting coastal and shelf waters, (2) the robust species in the Lagenorhynchus genus with the coastal La. australis, the offshore La. cruciger, the pelagic species La. obscurus and La. obliquidens, and (3) the morphologically aberrant genus Lissodelphis. Here, the shapes of 164 skulls from adults of all 10 species were compared using 3‐dimensional geometric morphometrics. The Lissodelphininae skulls were supplemented by samples of Lagenorhynchus albirostris and Delphinus delphis to obtain a context for the variation found within the subfamily. Principal components analysis was used to map the most important components of shape variation on phylogeny. The first component of shape variation described an elongation of the rostrum, lateral and dorsoventral compression of the neurocranium and smaller temporal fossa. The two Lissodelphis species were on the high extreme of this spectrum, while Lagenorhynchus australis, La. cruciger and Cephalorhynchus heavisidii were at the low extreme. Along the second component, La. cruciger was isolated from the other species by its expanded neurocranium and concave facial profile. Shape variation supports the gross phylogenetic relationships proposed by recent molecular studies. However, despite the great diversity of ecology and external morphology within the subfamily, shape variation of the feeding apparatus was modest, indicating a similar mode of feeding across the subfamily. All 10 species were similar in their pattern of skull asymmetry, but interestingly, two species using narrowband high frequency clicks (La. cruciger and C. hectori) were among the most asymmetric species, contradicting previous interpretations of odontocete skull asymmetry. J. Morphol. 277:776–785, 2016. © 2016 Wiley Periodicals, Inc.     

The role of ontogeny on character polarization in early dinosaurs: a new specimen from the Late Triassic of southern Brazil and its implications

Only recently, new ontogenetic series of early dinosaurs and related groups have been described. Here, we present an isolated immature dinosauriform femur from the Late Triassic of southern Brazil and investigate its influence on character polarization. Because the specimen shares a number of synapomorphies with Pampadromaeus barberenai, herein we postulate that it corresponds to a juvenile individual of that taxon. Accordingly, we investigate the morphological variation between juvenile and mature individuals of P. barberenai. Scoring these character states into a published phylogenetic data-set of Dinosauromorpha reveals that morphological variation is higher than that observed among closely-related taxa. Ontogenetic variation thus exerts influence on character polarization. In addition, modification of the scores affected by ontogeny produces different topologies, as noted by the reduction in both the number of most parsimonious trees and number of steps, and increased inclusivity of some clades and reduction of polytomies as well. Our study, together with other recent contributions, sheds light on the morphologic pathways seen during dinosauromorph ontogenetic development, which is crucial to more reliably assess phylogenetic reconstructions and macroevolutionary patterns of this widespread and successful group.     

A new blunt-snouted dyrosaurid,Anthracosuchus balrogus gen. et sp. nov. (Crocodylomorpha,Mesoeucrocodylia), from the Palaeocene of Colombia

A new exceptionally brevirostrine dyrosaurid is described from the middle Palaeocene (58–60 million years ago) Cerrejón Formation, northeastern Colombia, based on four partial skulls and associated postcrania. This taxon is unique among dyrosaurids not only in skull shape, but also in having orbital tuberosities, and osteoderms that are dorsoventrally thick and unpitted, a trait otherwise unknown in Crocodylomorpha. Results from a cladistic analysis of Dyrosauridae suggest that the new taxon, together with Cretaceous–Palaeocene Chenanisuchus lateroculi from Africa and Cerrejonisuchus improcerus also from the Cerrejón Formation, are the most basal members of the family. Results from a biogeographic analysis indicate at least three independent dispersals of dyrosaurids from Africa to the New World occurred in the Late Cretaceous or early Palaeocene. Widely set orbits in the new taxon indicate a deviation from surface-based predation, characteristic of other dyrosaurids, to sub-surface predation, as in modern Gavialis. Tooth impressions found on turtle shells recovered from the same locality match well with teeth of the new taxon indicating possible predation.http://www.zoobank.org/urn:lsid:zoobank.org:pub:AB2B24A5-27CC-4D3F-B580-F11F17851CE6