Dinosaur Genera Research Articles

The record ofTorosaurus(Ornithischia: Ceratopsidae) in Canada and its taxonomic implications

AbstractThe horned dinosaur genus Torosaurus has a challenging history, relating both to its geographic distribution and taxonomy. Whereas Torosaurus has been reported from Upper Maastrichtian deposits in Canada, which would mark the northernmost range of the genus, recent work has questioned the generic identity of the implicated material, which primarily consists of a pair of cranial frills. Perhaps more problematically, the validity of the genus itself has been a subject of recent debate, with some arguing that Torosaurus is simply a skeletally mature growth form of the contemporaneous Triceratops. In this study, we describe and illustrate the relevant frill material from Canada, and determine that it is most plausibly attributable to the Torosaurus morph. Moreover, we apply for the first time osteohistological sampling to some postcranial material associated with one of the frills, and find that the animal was still growing at the time of death. This finding, in addition to other considerations presented here, leads us to conclude that Torosaurus is a valid genus, and is not simply a mature growth form of Triceratops.

Dinosaur Bones from the Maestrazgo UNESCO Global Geopark (Teruel, Spain)

The current territory of the Maestrazgo UNESCO Global Geopark has provided fossils that pioneered dinosaur research in Spain. The first Spanish dinosaur, Aragosaurus ischiaticus (published in 1987), five other new genera of dinosaurs and six species were described from fossils found at Geopark sites. These are the sauropod Galveosaurus herreroi (Galvesaurus herreroi) in 2005, the iguanodontians Delapparentia turolensis in 2011 and Iguanodon galvensis in 2015, the basal ornithopod Gideonmantellia amosanjuanae in 2012, and the theropod Camarillasaurus cirugedae in 2014. This makes it one of the most relevant areas in Spain for dinosaur research and has given rise to numerous scientific publications on paleontology and the stratigraphy of the area. It has also led to the construction of several facilities to promote education and geotourism.

The correct authorship of Coloradisaurus (Dinosauria, Sauropodomorpha): Galton, 1990, not Lambert, 1983

Until now, authorship of the sauropodomorph dinosaur genus Coloradisaurus has been attributed to Lambert, 1983. Here we demonstrate that Lambert's work does not meet the requirements of Articles 13.1 and 13.3 of the Code for availability of this name, therefore it is a nomen nudum in that publication. Instead, it was inadvertently made available a few years later by another worker, as ColoradisaurusGalton, 1990.

Psittacosaurus amitabha, a New Species of Ceratopsian Dinosaur from the Ondai Sayr Locality, Central Mongolia

Psittacosaurus is the most speciose nonavian dinosaur genus, represented by at least 10 (and possibly as many as 19) species uncovered over a wide geographic range. Here, we report a new species of large-bodied Psittacosaurus from the Ondai Sayr locality in central Mongolia, which has hitherto produced only one other Psittacosaurus specimen. This new species is characterized by: (1) an elongate snout, with a gently inclined rostronasal margin, (2) a cranium dorsally convex rather than flat, (3) a subtemporal length less than 40% of total skull length, (4) a maxillary lamina that cups the posterior toothrow, (5) five premaxillary foramina arrayed in an arc, (6) an antorbital fossa as long as it is wide, and (7) a palpebral with a well-developed posterior tonguelike process. Psittacosaurus amitabha is resolved as the most basal member of the genus Psittacosaurus in our phylogenetic analysis. This taxon expands our knowledge of the already-speciose genus Psittacosaurus as well as our understanding of the Ondai Sayr fauna, which is poorly known in comparison to other Mongolian Early Cretaceous localities.

Introducing the Mazongshan Dinosaur Fauna

ABSTRACTThe Mazongshan Dinosaur Fauna (MDF) includes all dinosaurs recovered from the late Early Cretaceous Xiagou and Zhonggou formations in the Mazongshan area of Gansu Province in northwestern China. Currently, 11 distinctive dinosaur genera have been recovered in this fauna, representing three theropods, two sauropods, four hadrosauroids, and two neoceratopsians. Four features can be recognized for the MDF: (1) the presence of large herbivorous theropods, such as the therizinosaur Suzhousaurus and ornithomimosaur Beishanlong; (2) the presence of diverse basal hadrosauroids, represented by at least four genera; (3) an abundance of basal neoceratopsians, represented by numerous individuals of Auroraceratops; and (4) an apparent lack of psittacosaurids. The MDF is unique and different from any other known dinosaur faunas, including that from the Jehol Biota.Citation for this article: You, H.-L., E. M. Morschhauser, D.-Q. Li, and P. Dodson. 2019. Introducing the Mazongshan Dinosaur Fauna; pp. 1–11 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: 10.1080/02724634.2017.1396995.AbbreviationsCAGS IGInstitute of Geology, Chinese Academy of Geological Sciences, Beijing, ChinaCCDPChina-Canada Dinosaur ProjectIVPPInstitute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, ChinaMDFMazongshan Dinosaur FaunaSADPSino-American Mazongshan Dinosaur ProjectSJDPSino-Japanese Silk Road Dinosaur ExpeditionSSESino-Swedish Expedition

Considerations on the replacement of a type species in the case of the sauropod dinosaur Diplodocus Marsh, 1878

The sauropod dinosaur genus Diplodocus Marsh, 1878, is currently typified by a morphologically undiagnosable type species, D. longus Marsh, 1878. Only two caudal vertebrae and an associated partial chevron of its holotype (Yale Peabody Museum [YPM] VP.001920) remain reasonably complete, but more, fragmentary caudal vertebrae are available, and provide additional morphological information. YPM VP.001920 can be referred to Diplodocus generally, but cannot be distinguished from other Diplodocus species based on autapomorphies. Thus, the genus Diplodocus would have to be considered a nomen dubium. In order to resolve this unsatisfactory taxonomic issue, Tschopp and Mateus (2016) proposed to designate a new type species for the genus Diplodocus: namely, the well-known D. carnegii Hatcher, 1901.Herein, we expand upon historical and taxonomic issues concerning the holotype of D. longus, in order to: (1) provide additional imagery and information on the specimen and (2) to address comments against the replacement of D. longus by D. carnegii as the type species of Diplodocus as proposed by Tschopp and Mateus (2016).

The nomenclatural status of the carnivorous dinosaur genus Altispinax v. Huene, 1923 (Saurischia, Theropoda) from the Lower Cretaceous of England

The nomenclatural status of the carnivorous dinosaur genus Altispinax v. Huene, 1923 (Saurischia, Theropoda) from the Lower Cretaceous of England

Case 3700DiplodocusMarsh, 1878 (Dinosauria, Sauropoda): proposed designation ofD. carnegiiHatcher, 1901 as the type species

Abstract. The purpose of this application, under Articles 78.1 and 81.1 of the Code, is to replace Diplodocus longus Marsh, 1878 as the type species of the sauropod dinosaur genus Diplodocus by the much better represented D. carnegii Hatcher, 1901, due to the undiagnosable state of the holotype of D. longus (YPM 1920, a partial tail and a chevron). The holotype of D. carnegii, CM 84, is a well-preserved and mostly articulated specimen. Casts of it are on display in various museums around the world, and the species has generally been used as the main reference for studies of comparative anatomy or phylogeny of the genus. Both species are known from the Upper Jurassic Morrison Formation of the western United States. The genus Diplodocus is the basis for the family-level taxa diplodocinae Marsh, 1884, diplodocidae Marsh, 1884, diplodocimorpha Marsh, 1884 (Calvo & Salgado, 1995) and diplodocoidea Marsh, 1884 (Upchurch, 1995). It is also a specifier of at least 10 phylogenetic clades. With the replacement of D...

Perinates of a new species of Iguanodon (Ornithischia: Ornithopoda) from the lower Barremian of Galve (Teruel, Spain)

Although Iguanodon is one of the most abundant and well-known of Europe's dinosaur genera, fossils of young specimens are very rare. Indeed, the fossil record contains very few examples of the young of any non-hadrosaurid iguanodontian. Here we report the discovery of 13 Iguanodon perinates from the Lower Cretaceous of Galve (Teruel, Spain). The characteristics of an adult and juvenile found nearby show these perinates to belong to a new species: Iguanodon galvensis sp. nov. The histological and osteological features of these young animals indicate them to have been in their first year of life. The taphonomic features of their remains, plus the finding of clearly embryonic vertebrae alongside them, suggest the perinates of this species remained in the vicinity of their nests for some time, possibly congregating in nursery areas.

The Isle of Wight and its crucial role in the ‘invention’ of dinosaurs

Dinosaurs were ‘invented’ in April 1842. Any history, before this, must separate periods of pre-history. The first covers the period before 1824 (when the first dinosaur genus Megalosaurus was described). Here the Isle of Wight discloses a forgotten pioneer in natural history, the stone mason/sculptor James Hay (c. 1748–1821) who may well have included, by 1818, such dino-to-be material in his remarkable Portsmouth museum. This was described on his death as ‘the best private collection in the kingdom’. Sadly, his material is lost, and no accurate diagnosis is possible. The second period extends from 1824 to 1842. The significant figure here is the Russia and East Indies merchant James Vine (1774–1837), who first revealed how Iguanodon bones occurred in abundance in the Island's south-west coastal outcrops. One, between September 1841 and April 1842, revealed to Richard Owen his long-sought fossil sacrum of an Iguanodon. This was in the private London museum of the political radical W. D. Saull (1783–1855). The discovery of this single fossil enabled Owen to ‘invent’ dinosaurs. He later wrote of this historic specimen how ‘the characters of the order Dinosauria were mainly founded on this specimen’. So, in a real sense, the Isle of Wight is the birthplace of Dinosaurs.

Opinion 2320(Case 3536)StegosaurusMarsh, 1877 (Dinosauria, Ornithischia): type species replaced withStegosaurus stenopsMarsh, 1887

The Commission has preserved stability in the taxonomy of stegosaurian dinosaurs by replacing Stegosaurus armatus Marsh, 1877, the unidentifiable type species of the ornithischian dinosaur genus Stegosaurus Marsh, 1877, with the very well represented nominal species Stegosaurus stenops Marsh, 1887, also from the Upper Jurassic Morrison Formation, U.S.A.

Case 3536StegosaurusMarsh, 1877 (Dinosauria, Ornithischia): proposed replacement of the type species withStegosaurus stenopsMarsh, 1887

The purpose of this application, under Article 81.1 of the Code, is to preserve stability in the taxonomy of stegosaurian dinosaurs by replacing Stegosaurus armatus Marsh, 1877, the unidentifiable type species of the ornithischian dinosaur genus Stegosaurus Marsh, 1877, with the very well represented nominal species Stegosaurus stenops Marsh, 1887, also from the Upper Jurassic Morrison Formation, U.S.A. This genus is the basis for Stegosauria Marsh, 1877, stegosauroidea Marsh, 1880, stegosauridae Marsh, 1880 and stegosaurinae Marsh, 1880. Maidment et al. (2008) listed seven putative autapomorphic characters for Stegosaurus and five for the species Stegosaurus armatus in its current usage. However, the holotype of S. armatus, which consists of an articulated series of 18 incomplete vertebrae from the proximal half of the tail and a very large but incomplete dermal plate, shows none of these diagnostic characters and so S. armatus must be considered a nomen dubium. However, the holotype of S. stenops Marsh, 1887 shares all 12 autapomorphies with S. armatus in its current usage, being based on an almost complete skeleton (USNM 4934), most of it still in the rock preserving almost natural articulation, which would make S. stenops by far the best available species to replace S. armatus as type species of Stegosaurus Marsh, 1877.

Dinosaur diversity and the rock record

Palaeobiodiversity analysis underpins macroevolutionary investigations, allowing identification of mass extinctions and adaptive radiations. However, recent large-scale studies on marine invertebrates indicate that geological factors play a central role in moulding the shape of diversity curves and imply that many features of such curves represent sampling artefacts, rather than genuine evolutionary events. In order to test whether similar biases affect diversity estimates for terrestrial taxa, we compiled genus-richness estimates for three Mesozoic dinosaur clades (Ornithischia, Sauropodomorpha and Theropoda). Linear models of expected genus richness were constructed for each clade, using the number of dinosaur-bearing formations available through time as a proxy for the amount of fossiliferous rock outcrop. Modelled diversity estimates were then compared with observed patterns. Strong statistically robust correlations demonstrate that almost all aspects of ornithischian and theropod diversity curves can be explained by geological megabiases, whereas the sauropodomorph record diverges from modelled predictions and may be a stronger contender for identifying evolutionary signals. In contrast to other recent studies, we identify a marked decline in dinosaur genus richness during the closing stages of the Cretaceous Period, indicating that the clade decreased in diversity for several million years prior to the final extinction of non-avian dinosaurs at the Cretaceous-Palaeocene boundary.

Two ornithischian dinosaurs renamed: Microceratops Bohlin 1953 and Diceratops Lull 1905

The Ceratopsian dinosaur genera Diceratops Lull, 1905 and Microceratops Bohlin, 1953 are preoccupied by the Hymenoptera insects, Diceratops Foerster, 1868 and Microceratops Seyrig, 1952, respectively. Therefore, the name of the ceratopsian dinosaur Diceratops Lull, 1905 from the Late Cretaceous of United States is a junior homonym of the hymenoptera Diceratops Foerster, 1868. Diceratus n. gen. (Greek di = “two,” Greek ceratos = “horned”) is proposed as the replacement name of Diceratops Lull, 1905. Some workers have considered Diceratops synonymous with Triceratops (e.g., Dodson and Currie, 1990) but it was reinstated by Forster (1996) after analysis of the characteristics of all existing ceratopsid skulls, and recent reviews (e.g., Dodson et al., 2004) have considered Diceratops a valid genus.

How to find a dinosaur, and the role of synonymy in biodiversity studies

Taxon discovery underlies many studies in evolutionary biology, including biodiversity and conservation biology. Synonymy has been recognized as an issue, and as many as 30–60% of named species later turn out to be invalid as a result of synonymy or other errors in taxonomic practice. This error level cannot be ignored, because users of taxon lists do not know whether their data sets are clean or riddled with erroneous taxa. A year-by-year study of a large clade, Dinosauria, comprising over 1000 taxa, reveals how systematists have worked. The group has been subject to heavy review and revision over the decades, and the error rate is about 40% at generic level and 50% at species level. The naming of new species and genera of dinosaurs is proportional to the number of people at work in the field. But the number ofvalidnew dinosaurian taxa depends mainly on the discovery of new territory, particularly new sedimentary basins, as well as the number of paleontologists. Error rates are highest (>50%) for dinosaurs from Europe; less well studied continents show lower totals of taxa, exponential discovery curves, and lower synonymy rates. The most prolific author of new dinosaur names was Othniel Marsh, who named 80 species, closely followed by Friedrich von Huene (71) and Edward Cope (64), but the “success rate” (proportion of dinosaurs named that are still regarded as valid) was low (0.14–0.29) for these earlier authors, and it appears to improve through time, partly a reflection of reduction in revision time, but mainly because modern workers base their new taxa on more complete specimens. If only 50% of species are valid, evolutionary biologists and conservationists must exercise care in their use of unrevised taxon lists.

The earliest discoveries of dinosaurs: the records re-examined

The history of English discoveries of dinosaurs is recounted, from Robert Plot's first illustration of a dinosaur bone in 1677 to the first formal scientific description and naming of a dinosaur genus by William Buckland in 1824. It is shown that the English discoveries were more numerous than recognized hitherto and that they amply predated the first finds in France and North America. Though bones of other dinosaur groups were discovered, the majority of English finds were of carnosaur (probably megalosaur) bones and teeth. It is considered probable that all the various bones and teeth of Megalosaurus , obtained piecemeal from the Stonesfield Slate at Stonesfield, Oxfordshire over 125 years, were the remains of a single individual dinosaur.

Dinosaurs: the encyclopedia

This is the first supplement to the encyclopaedia that was named an ALA Outstanding Reference Book. This work maintains the arrangement of the primary volume and is up to date late into 1998. It includes over a dozen new dinosaur genera and even more new species and new life restorations. Section One provides introductory text on subtopics such as The Mesozoic Era, Ectothermy Versus Endothermy, and Dinosaur Extinctions. Section Two continues the workable ordering of dinosaur systematics. Section Three continues the alphabetical compilation of new dinosaur genera, and the last section continues the detailing of doubtful genera that have appeared in the palaeontological literature.

Fantasia and Our Changing Views of Dinosaurs

Popular culture often presents us with images that can color our perception of the past, even if those images are later shown to be inaccurate. One such image, the “Rite of Spring” sequence from Walt Disney's Fantasia (1940), can act as a starting point for a discussion of our changing views of dinosaurs. At least fourteen recognizable dinosaur genera, as well as other extinct reptiles (plesiosaurs, mososaurs, pterosaurs, and pelycosaurs) and transitional forms between fish and amphibians and between reptile and birds, are represented in the sequence. Compared to more recent dinosaur films, perhaps no other sequence so genuinely attempted to portray dinosaurs as they actually might have been. Of course, many of the interpretations presented in the “Rite of Spring” have not survived the scientific progress of the past half century, but this demonstrates the need to be constantly aware of new discoveries and interpretations; not only about dinosaurs, but about any branch of science.

Cranial morphology and systematics ofChasmosaurus(Dinosauria: Ceratopsidae) from the Upper Cretaceous of western Canada

ABSTRACT The ceratopsid dinosaur genus Chasmosaurus from the Judith River Formation (Campanian; Judithian) of western Canada shows considerable variability in cranial morphology due in part to an unusually long ontogenetic trajectory. Nevertheless, two more or less distinct morphs can be identified. Allometry and sexual dimorphism cannot be invoked to account for this variability, leaving the presence of two species as the most likely explanation. In C. belli, the posterior margin of the parietal frill shows little or no emargination and bears one large triangular epoccipital on each posterolateral corner. Additional epoccipitals may be present, but are much less prominent. Chasmosaurus Canadensis, Chasmosaurus kaiseni, and Chasmosaurus brevirostris also show this morphology, and are here considered junior synonyms of Chasmosaurus belli. Chasmosaurus russelli is characterized by a deeply emarginated posterior parietal margin. On each side, the posterior margin of the frill forms a broad arch, bearing thre...

Historical Dinosaurs: Episodes in Discovery and Restoration

Inspired by the approaching sesquicentennial year of the Dinosauria, a classification term created by Sir Richard Owen in 1841 originally corresponding to three extinct genera of enormous, terrestrial British Mesozoic reptiles, the author created miniature models of several dinosaur genera. Sculptures commemorating historically significant restorative stages in paleontological understanding for five genera (Iguanodon, Megalosaurus, Had-rosaurus, Stegosaurus, and Chasmosaurus) were constructed to emphasize the theme of ‘evolving’ ideas concerning dinosaur representations. The stories behind the scientific derivation and ‘evolution’ of these forms illustrate several interesting episodes in the history of dinosaur paleontology.