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... This scar has also been observed in Ekrixinatosaurus, Skorpiovenator, Masiakasaurus, Afromimus tenerensis, the indeterminate Libyan Early Cretaceous abelisauroid PRC NF.1.21, and SHN-JJS 65/2 (Carrano et al., 2002;Smith et al., 2010;Malafaia et al., 2015;Cerroni et al., 2019). It was probably the attachment site for the M. flexor tibialis internus 3 or 2e4 (according to Carrano et al., 2002 andSmith et al., 2010, respectively). ...
... However, the medial fossa of Xenotarsosaurus is less developed than those of Masiakasaurus and Afromimus, in which it is wider and deeper (see Carrano et al., 2011, fig. 23a, b;Cerroni et al., 2019). The fossa faces posteriorly as in several ceratosaurs (e.g., Ceratosaurus, Eoabelisaurus, Skorpiovenator, among others), contrasting the more medially opening fossa observed in some tetanurans (e.g., Allosaurus fragilis). ...
Article
Xenotarsosaurus bonapartei was the third abelisaurid theropod dinosaur to be named from Argentina. The holotype comprises two partial anterior dorsal vertebrae and a complete right hind limb from the Upper Cretaceous (lower Cenomanian–upper Turonian) Bajo Barreal Formation, central Patagonia, Argentina. The materials display morphological features that undoubtedly position Xenotarsosaurus within Abelisauroidea. Moreover, detailed comparisons with members of that theropod group confirm the close relationship of this taxon to abelisaurids. Here we provide an emended diagnosis of Xenotarsosaurus bonapartei that includes five newly recognized autapomorphies: (1) anterior dorsal vertebrae with large, strongly dorsoventrally developed parapophyses; (2) anterior dorsal vertebrae with well-developed centroprezygapophyseal fossae that are taller dorsoventrally than wide mediolaterally; (3) fibular condyle of femur triangular in shape and projecting posteriorly; (4) well-marked groove on the anterolateral corner of the proximal fibula; and (5) iliofibularis tubercle of fibula distally interrupted by a hook-like shaped concavity. To determine its systematic position within Abelisauroidea, we incorporated Xenotarsosaurus into a phylogenetic analysis, recovering this theropod as a non-carnotaurine abelisaurid more derived than Eoabelisaurus mefi. Xenotarsosaurus displays several plesiomorphic traits when compared with penecontemporaneous abelisaurids from the Neuquén Group. Similarly, other non-avian dinosaur taxa from the Bajo Barreal Formation are frequently postulated as more phylogenetically basal than coeval forms from northern Patagonia. This scenario suggests the potential existence of provincialism in early Late Cretaceous continental vertebrate faunas of southern South America. The present study increases knowledge of abelisaurid systematics, evolution, and paleobiogeography and augments our understanding of the Late Cretaceous dinosaur assemblage of central Patagonia.
... The fibular crest of Camarillasaurus does not make contact with the proximal tibia and is located lower on the shaft than in ceratosaurs, thus differing from nontetanuran theropods including ceratosaurs (Figure 10). In the tibia of non-tetanurans, the proximal end shows a proximally extended fibular crest, and the crest reaches the proximal end of the tibia (e.g., Cerroni et al. 2019). Camarillasaurus also shows non-ceratosaurian character, i.e., the development of the fibular crest of the tibia does not extend to the proximal end (e.g., Benson 2010;Cerroni et al. 2019). ...
... In the tibia of non-tetanurans, the proximal end shows a proximally extended fibular crest, and the crest reaches the proximal end of the tibia (e.g., Cerroni et al. 2019). Camarillasaurus also shows non-ceratosaurian character, i.e., the development of the fibular crest of the tibia does not extend to the proximal end (e.g., Benson 2010;Cerroni et al. 2019). The fibular crest of Camarillasaurus is possibly reduced (the fibular crest is partially damaged), and if this is the case, this would be similar to Spinosaurus. ...
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We report theropod caudal vertebrae found at Phu Wiang Mountain, Thailand. They resemble the Portuguese Baryonyx and pertain to the Spinosauridae based on the presence of striations on the surface of the transverse process of the caudals, well developed double keels and a deep ventral groove on the centra, two laminae, delimiting three fossae below the transverse process, and posterior caudals having curved, rod-like neural spines with small process at the base. This supports the presence of spinosaurids in the Sao Khua Formation of Thailand. Furthermore, the putative basal ceratosaur Camarillasaurus Sánchez- Hernández and Benton, 2014 from Spain is found here to be a spinosaurid based on the resemblance of the type materials to the Thai spinosaurid described in the present work, as well as the phylogenetic analysis and the similarity to other spinosaurids. In Europe, spinosaurids have been reported from England, Portugal, and Spain. The reassessment of Camarillasaurus adds to the number of this group in this region. The presence of more than one spinosaurid taxon in the same region is common and can be found in the Kem Kem Beds of Morocco, the Araripe Basin of Brazil, the Iberian Peninsula, and the Khorat Plateau of Southeast Asia.
... In order to determine the phylogenetic position of NMV P252004, we scored it for the Langer et al. (2019) dataset (focused on Ceratosauria), which was in turn modified from that of Rauhut and Carrano (2016). Using Mesquite 3.61 (Maddison and Maddison, 2019), we scored Afromimus for this dataset (following Cerroni et al. (2019)), changed the score of C96 from '?' to '1 & 2' for Limusaurus (following Wang et al. (2017a)), and excluded three operational taxonomic units from our analyses owing to specimen incompleteness (USNM 8415) or questionable assignation to Ceratosauria (Spinostropheus (Rauhut and Carrano, 2016), Deltadromeus (Apesteguía et al., 2016)). Following Langer et al. (2019), characters 33, 103, 104, 117, 138, 154, and 165 were set as ordered. ...
... The cervical vertebrae of Nqwebasaurus thwazi (De Klerk et al., 2000;Choiniere et al., 2012;Sereno, 2017), which has been interpreted as the earliest-branching ornithomimosaur (despite previous debate over its precise phylogenetic position within Coelurosauria; see synopsis in Cerroni et al. (2019)), are also superficially similar to NMV P252004. However, the cervical vertebrae of Nqwebasaurus show several subtle, yet salient, differences from NMV P252004: they (are presumed to) possess anterior pneumatic foramina, lack posterior pneumatic fossae, possess broad postspinal fossae, have anteroposteriorly shorter neural spines, and some possess prominent PCDLs visible in lateral view (Choiniere et al., 2012;Watanabe et al., 2015;Sereno, 2017). ...
Article
Elaphrosaurinae is an enigmatic clade of gracile ceratosaurian theropod dinosaurs known from the Late Jurassic of Africa (Elaphrosaurus bambergi) and Asia (e.g., Limusaurus inextricabilis), and the early Late Cretaceous of Argentina (Huinculsaurus montesi). Elaphrosaurinae is often placed within Noasauridae as the sister taxon to Noasaurinae, a clade of small-bodied theropods that lived in South America, Africa, Madagascar and India throughout much of the Cretaceous. Herein, we report the first evidence of Elaphrosaurinae from Australia: a nearly complete middle cervical vertebra from the upper Lower Cretaceous (lower Albian) Eumeralla Formation of Cape Otway, Victoria, Australia. The fact that this site would have been situated at ~76°S towards the end of the Early Cretaceous (~110–107 Ma) implies that elaphrosaurines were capable of tolerating near-polar palaeoenvironments, whereas its age indicates that elaphrosaurines persisted in Australia until at least the late Early Cretaceous. The new Australian elaphrosaurine, in tandem with the recently described Huinculsaurus montesi from the Cenomanian–Turonian of Argentina, implies that the spatiotemporal distribution of Elaphrosaurinae has heretofore been greatly underestimated. Historic confusion of elaphrosaurines with coelurosaurs, especially ornithomimosaurs, coupled with our generally poor understanding of noasaurid evolution, might explain the apparent dearth of fossils of this theropod clade worldwide.
... In this context, we have scored several previously unknown character states for Skorpiovenator (Supplemental material Table S2). The sample of taxa has been modified with the addition of Afromimus tenerensis (Sereno 2017;Cerroni et al. 2019), Llukalkan aliocranianus , Niebla antiqua (Aranciaga-Rolando et al. 2021), Quilmesaurus curriei (Coria 2001) and Xenotarsosaurus bonapartei (Mart ınez et al. 1986;Ibiricu et al. 2021), whereas other fragmentary taxa have been removed (i.e. 'Spinostropheus-type', Camarillasaurus, Deltadromeus and USNM 8415) due to their questioned ceratosaurian affinity (Rauhut & Carrano 2016;Langer et al. 2019;Samathi et al. 2021). ...
Article
Skorpiovenator bustingorryi is a derived abelisaurid theropod represented by a fairly complete skeleton from the Late Cretaceous sedimentary beds of north-western Patagonia. Although some features were described in the original paper, mainly related to the skull, the appendicular anatomy remains undescribed. The aim of the present contribution is to provide a detailed description and analysis of the available appendicular bones, including comparisons with other ceratosaurian theropods close to Skorpiovenator. In this way, new autapomorphies emerged to further distinguish Skorpiovenator from its relatives. Furthermore, a comprehensive phylogenetic analysis was performed and several characteristics of the hind limb, in particular some of the autopodium, resulted in the identification of new apomorphic traits for Ceratosauria and Abelisauridae. These features might prove to be useful for future phylogenetic analyses and may help to resolve the still confusing and debated internal relationships of abelisaurid theropods.
... Elaphrosaurus, and is markedly differs from the condition seen in coelophysoids and ceratosaurs, in which the fossa is covered anterodorsally by the tibial crest and thus opens posteriorly(Rauhut 2003;Allain et al. 2007;Rauhut & Carrano 2016;Cerroni et al. 2019). ...
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This contribution describes the continental micro- and macrovertebrate fauna of Angeac- Charente (Berriasian, Early Cretaceous). The rich and diversified fauna includes at least 38 different vertebrate taxa from all major clades, and is represented by more than 50 000 specimens. The Angeac–Charente locality includes the most diverse earliest Cretaceous mixed continental bonebed and Lagerstätte known to date in the World, and it provides a good picture of a Purbeckian paleocommunity. It includes remarkable taxa such as a new ornithomimosaur, a large turiasaur, an helochelydrid turtle and numerous mammals. The vertebrate fauna of Angeac has beyond all a Purberckian character. Many exclusively European genera and species belong to families with an essentially Laurasian paleogeographic distribution. Some taxa nevertheless suggest dispersal events between Africa and Europe at the Jurassic/Cretaceous transition. The successive Charente faunas of Chassiron (Tithonian), Cherves–de–Cognac (Berriasian) and Angeac–Charente improve our poor knowledge of the evolution of continental vertebrate faunas at the Jurassic/Cretaceous transition. Rather than reflecting an important faunal turnover between the Tithonian and the Berriasian, they record environmental changes related to the sea–level regression that characterizes the end of the Jurassic.
... This is still supported by the numbers of coelurosaur-bearing localities: whereas this clade occurs in a total of 23% of the Laurasian theropod localities (and this number might be an underestimation, as coelurosaurian occurrences based on isolated teeth have not been considered), no certain coelurosaurian theropod has been identified from the Late Jurassic of Gondwana so far. This is quite probably at least partially an artifact of the poor Gondwanan theropod fossil record, as suggested by the presence of theropods with putative affinities with ornithomimids in the Early Cretaceous of Africa (Nqwebasaurus Choiniere et al., 2012;Afromimus Sereno, 2017, was also suggested to represent an ornithomimid in the original description, but has since been shown to represent an abelisauorid; Cerroni et al., 2019). However, coelurosaurs seem to have at least been rare in Gondwana in the Late Jurassic; even given the low number of known localities, this clade would be expected to be present in three to nine localities, given their relative abundance in the Northern Hemisphere. ...
Article
Late Jurassic South American theropod faunas are still extremely poorly known, with large-sized ceratosaurids and megalosaurids having been identified on the basis of isolated teeth, whereas the only named taxa, Chilesaurus and Pandoravenator, are probable tetanurans of uncertain affinities. Here we describe two new specimens of medium-sized to large theropods from the Oxfordian-Kimmeridgian Cañadón Calcáreo Formation of Chubut, Argentina; an isolated and rather well-preserved anterior cervical vertebra and a very fragmented, but associated assortment of bones, including cranial and vertebral remains. Both specimens show ceratosaurian and, most probably abelisaurid affinities. A faunal analysis underlines the relative abundance of ceratosaurs and the absence of coelurosaurs as main differences of Late Jurassic Gondwanan theropod faunas from their Laurasian counterparts. The presence of abelisaurids in both the Tendaguru Formation and the Cañadón Calcáreo Formation indicates a wide distribution of this clade already in the Late Jurassic in the Southern Hemisphere.
... In both diagrams, relationships among tetanurans collapsed for brevity. noasaurid (as also recently discussed by Cerroni et al., 2019), due to the lack of unambiguous ornithomimosaurian synapomorphies (Makovicky et al., 2004). In particular, Sereno (2017) listed some features in the caudal vertebrae and in the pedal ungual shared by Afromimus and ornithomimosaurs and dismissed the referral to Abelisauroidea. ...
Article
A new ceratosaurian theropod dinosaur, Huinculsaurus montesi gen. et sp. nov., is described here. This taxon is based on the last three dorsal vertebrae and the first and second sacral vertebrae found in association at Aguada Grande, Neuquén Province, Argentina. Although fragmentary, Huinculsaurus shows a unique mix of features which differentiates it from all other theropods, including the sympatric abelisaurid Ilokelesia, and is diagnosed by prezygapophyseal articular facets twice longer than wide, anterior centroparapophyseal lamina strongly developed as an extensive lateral lamina in the posterior dorsal vertebrae, pneumatic foramina located ventrally to the postzygodiapophyseal lamina in the posterior dorsal vertebrae, posteriorly tapering postzygapophysis pointed posteriorly, and an accessory lamina bisecting the parapophyseal centrodiapophyseal fossa in the posterior dorsal neural arches. Phylogenetic analyses recovered Huinculsaurus as most closely related to the Late Jurassic Elaphrosaurus than to other Cretaceous abelisauroids, suggesting the persistence of the elaphrosaurine lineage in South America up to the early Late Cretaceous.
... If the results presented here are correct, then NMV P221202 and LRF 3050.AR represent novel reports of noasaurids from the late Barremian-early Aptian of Victoria and Cenomanian of New South Wales respectively. Under the taxonomic framework presented here, Noasauridae consists of at least six named taxa: Laevisuchus, Noasaurus and Masiakasaurus from the Maastrichtian of India, Argentina, and Madagascar respectively 44,67,87 ; Velocisaurus, from the Santonian of Argentina 88 ; Vespersaurus from the Aptian-Campanian of Brazil 69 and Afromimus tenerensis from the Aptian-Albian of Niger, initially described as an ornithomimid 89 but recently reappraised as a probable noasaurid 90 . Genusaurus sisteronis, from the Albian of France, has previously been considered as a noasaurid 22 , but subsequent analyses, including the one presented here, preferred a position within Abelisauridae. ...
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The diversity of Australia’s theropod fauna from the ‘mid’-Cretaceous (Albian–Cenomanian) is distinctly biased towards the medium-sized megaraptorids, despite the preponderance of abelisauroids in the younger but latitudinally equivalent Patagonian theropod fauna. Here, we present new evidence for the presence of ceratosaurian, and specifically abelisauroid, theropods from the Cenomanian Griman Creek Formation of Lightning Ridge, New South Wales. A partial cervical vertebra is described that bears a mediolaterally concave ventral surface of the centrum delimited by sharp ventrolateral ridges that contact the parapophyses. Among theropods, this feature has been reported only in a cervical vertebra attributed to the noasaurid Noasaurus. We also reappraise evidence recently cited against the ceratosaurian interpretation of a recently described astragalocalcaneum from the upper Barremian–lower Aptian San Remo Member of the upper Strzelecki Group in Victoria. Inclusion of the Lightning Ridge cervical vertebra and Victorian astragalocalcaneum into a revised phylogenetic analysis focused on elucidating ceratosaurian affinities reveals support for placement of both specimens within Noasauridae, which among other characters is diagnosed by the presence of a medial eminence on the ascending process of the astragalus. The Lightning Ridge and Victorian specimens simultaneously represent the first noasaurids reported from Australia and the astragalocalcaneum is considered the earliest known example of a noasaurid in the world to date. The recognition of Australian noasaurids further indicates a more widespread Gondwanan distribution of the clade outside of South America, Madagascar and India consistent with the timing of the fragmentation of the supercontinent.
Article
Herein we apply a new approach to the study of theropod footprints with elongated metatarsal traces from the Upper Cretaceous (lower-middle Cenomanian) Sezze ichnosite (Latium, central Italy). In this study, we combine traditional methods and new tools (i.e., close-range digital photogrammetry, sUAS – small Unmanned Aerial System, Principal Component Analysis, and Cluster Analysis) to identify the osteological features of the foot mirrored in the traces, analyse the differential depth of impressions and reconstruct the anatomical structure of the trackmaker foot. The use of close-range photogrammetry allows us to improve the ichnological interpretation and analysis, focusing on anatomical features such as phalangeal pads and claw traces. A dataset consisting of measurements of 66 foot skeletons of theropods and the five best preserved elongated footprints with metatarsal trace was subjected to Principal Component Analysis and Cluster Analysis, to investigate the morphospace occupied by the principal clade of theropods and find the most likely trackmaker among known taxa. The results indicate the clade of Oviraptorosauria as the more consistent producers for the Sezze theropod footprints, opening new questions about the clade dispersal and on the complex paleobiogeography of the Appenninic Carbonate Platform in the Late Cretaceous. The integrated multidisciplinary approach (high-resolution photogrammetry and morphometric analysis) confirms the utility of the new technological methodologies for the ichnological study.
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This contribution describes the continental micro- and macrovertebrate fauna of Angeac-Charente (Berriasian, Early Cretaceous). The rich and diversified fauna includes at least 38 different vertebrate taxa from all major clades, and is represented by more than 50 000 specimens. The Angeac-Charente locality includes the most diverse earliest Cretaceous mixed continental bonebed and the only Lagerstätte known to date in the World, and it provides a good picture of a Purbeckian paleocommunity. It includes remarkable taxa such as a new ornithomimosaur, a large turiasaur, an helochelydrid turtle and numerous mammals. The vertebrate fauna of Angeac-Charente has beyond all a Purberckian character. Many exclusively European genera and species belong to families with an essentially Laurasian paleogeographic distribution. Some taxa nevertheless suggest dispersal events between Africa and Europe at the Jurassic/Cretaceous transition. The successive Charentese faunas of Chassiron (Tithonian), Cherves-de-Cognac (Berriasian) and Angeac-Charente improve our poor knowledge of the evolution of continental vertebrate faunas at the Jurassic/Cretaceous transition. Rather than reflecting an important faunal turnover between the Tithonian and the Berriasian, they record environmental changes related to the sea–level regression that characterizes the end of the Jurassic.
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Positional variation is documented in ornithomimid pedal unguals from the Dinosaur Park and Horseshoe Canyon Formations of Alberta, Canada, and characters for identifying the position of isolated ornithomimid pedal unguals are discussed. Ungual morphology has been used recently to argue for the coexistence of two distinct ornithomimosaurs, a basal taxon and distinctly more derived taxon, in the Early Cretaceous Arundel Clay of Maryland, USA. However, these conclusions are based on misconceptions of the morphology and positional variability of ornithomimosaur unguals. Some characters previously cited as diagnostic of ornithomimosaur unguals are not actually observed in this clade, or are more homoplastically distributed among theropods. Other characters proposed to distinguish between the two pedal ungual morphs in the Arundel Clay material are shown in the Albertan ornithomimid material to consistently distinguish the different ungual positions within the pes of one individual. Claims of multiple distinct ornithomimosaur taxa in the Arundel Clay are premature, as the two pedal ungual morphotypes more likely represent positional variation in a single taxon.
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A new genus and species of ornithomimosaur, Afromimus tenerensis, is described based on a fragmentary skeleton from the Lower Cretaceous (Aptian—Albian) El Rhaz Formation of Niger. The holotype and only known individual preserves caudal vertebrae, chevrons and portions of the right hind limb. Derived ornithomimosaurian features include the broad, peanut-shaped articular surfaces of mid caudal centra, parasagittal fossae on mid caudal centra for reception of the postzygapophyses of the preceding vertebra, and a raised, subtriangular platform on the ventral aspect of the pedal phalanges. New information is given for, and comparisons made to, Nqwebasaurus thwazi from southern Africa, the oldest and most basal ornithomimosaur. Unlike other coelurosaurian clades that have expansive radiations on northern landmasses, the oldest ornithomimosaur and now another basal form are known from a southern landmass, Africa.
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Abelisauroids are the most abundant theropods in the Cretaceous beds of Patagonia. They are traditionally subdivided into large-sized Abelisauridae and smaller Noasauridae. Here, we describe a new specimen of the small enigmatic abelisauroid Velocisaurus unicus Bonaparte, 1991, which was previously known from a single incomplete specimen from Neuquén City, Neuquén Province, Patagonia. The new material comes from the Santonian Bajo de la Carpa Formation (Late Cretaceous) at the Paso Córdova locality, Río Negro Province. It comprises an almost complete left hind limb and offers novel information about the anatomy of this poorly known abelisauroid. The new material shows that Velocisaurus is remarkable in having a very short, stout, and anteriorly bowed femur, which has a notably subtriangular cross-section at its proximal end. The tibia is long and slender, and the anterior surface of the distal end is anteroposteriorly flat and transversely expanded, with an enlarged surface for the ascending process of the astragalus. The pes has a stout third metatarsal, rod-like metatarsals II and IV, and highly modified phalanges of digit IV. The unique combination of characters of Velocisaurus indicates that this taxon belongs to a still poorly understood radiation of gracile-limbed abelisauroids. The inclusion of Velocisaurus in a comprehensive phylogenetic analysis recovers a monophyletic Noasauridae, but with only very weak support. Detailed analysis of features supporting the inclusion of Velocisaurus within Noasauridae is discussed, and their implications for abelisauroid phylogeny are revisited. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: Brissón Egli, F., F. L. Agnolín, and Fernando Novas. 2016. A new specimen of Velocisaurus unicus (Theropoda, Abelisauroidea) from the Paso Córdoba locality (Santonian), Río Negro, Argentina. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1119156.
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Many recent studies of theropod relationships have been focused on the phylogeny of coelurosaurs and the question of the origin of birds, but the interrelationships and evolution of basal theropods are still poorly understood. Thus, this paper presents a phylogenetic analysis of all theropods, but focuses on the basal members of this clade. The result supports the inclusion of Eoraptor and herrerasaurids in the Theropoda, but differs from other recent studies in two main aspects: (1) The taxa usually grouped as ceratosaurs form two monophyletic clades that represent successively closer outgroups to tetanurans. The more basal of these clades, the Coelophysoidea, comprise the majority of Late Triassic and Early Jurassic theropods. The other clade of basal theropods that are usually included in the Ceratosauria comprises Ceratosaurus, Elaphrosaurus, and abelisaurids. (2) Two monophyletic groups of basal tetanurans are recognized: the Spinosauroidea and the Allosauroidea. In contrast to other recent phylogenetic hypotheses, both clades are united in a monophyletic Carnosauria. The branching pattern of the present cladogram is in general accordance with the stratigraphic occurrence of theropod taxa. Despite the differences in recent analyses, there is a significant level of consensus in theropod phylogeny. At least four different radiations of non-avian theropods can be recognized. These radiations show different patterns in Laurasia and Gondwana, and there are increasing differences between the theropod faunas of the two hemispheres from the Triassic to the Cretaceous.
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Ornithomimosauria is a group of medium to large, lightly built theropods that are mainly known from Cretaceous sediments of central Asia and western North America. This chapter examines the diagnostic features, evolution, and paleobiology, and phylogenetic relationships among ornithomimid taxa. Ornithomimosaurs are represented by Pelecanimimus, Gallimimus, Garudimimus, Ornithomimus, Struthiomimus, Harpymimus, Archaeornithomimus, Shenzhousaurus, and Anserimimus. They are characterized by short, delicate skulls, elongate forelimbs with a weak, nonraptorial manus, and long hindlimbs. The chapter also compares the biogeographic history of ornithomimosaurs within the broader context of several other dinosaur groups that display a predominantly Asian-North American distribution during the Cretaceous.
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Resumen The Late Cretaceous (Maastrichtian) Lameta Formation of central India has yielded dissociated elements of a variety of predatory dinosaurs, most of them coming from a quarry named the "Carnosaur bed." The materials were described by Huene and Matley nearly 70 years ago. They recognized nine theropod species, which they sorted out into the theropod subgroups "Carnosauria" and "Coelurosauria". Huene and Matley also described a considerable amount of theropod hindlimb bones (e.g., femora, tibiae, metatarsals, and pedal phalanges) that they could not refer to any of these species, but vaguely interpreted as corresponding to "allosaurid" or "coelurosaurid" theropods. We reviewed the available collection of Cretaceous theropods from Bara Simla housed at the Geological Survey of India, Calcutta, arriving to the following conclusions: 1) Indosuchus and Indosaurus are abelisaurids, as recognized by previous authors, but available information is not enough to judge whether they are synonyms; 2) Laevisuchus indicus is a small abelisauroid, related to Noasaurus and Masiakasaurus on the basis of their peculiar cervical vertebrae; 3) the controversial taxa " Compsosuchus", " Dryptosauroides", " Ornithomimoides", and " Jubbulpuria" are represented by isolated vertebrae corresponding to different portions of the neck and tail, and also exhibit abelisauroid features; 4) hindlimb bones originally referred to as "allosaurid" and "coelurosaurian" also exhibit abelisauroid characters, and bones of large size are tentatively referred to as corresponding to Indosuchus or Indosaurus, whereas some pedal bones of smaller size may belong to Laevisuchus; 5) two kinds of abelisaurid feet are apparent: one in which the phalanges of digit III and IV are robust, and another type in which the phalanges of digit IV are transversely narrow and dorsoventrally deep. This review demonstrates that all of the theropod elements discovered at the "Carnosaur bed" belong to a single theropod clade, the Abelisauroidea
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A new theropod dinosaur, Lepidocheirosaurus natatilis gen. et sp. nov., from the Upper Jurassic (?Tithonian) deposits of the Kulinda locality (Transbaikal Area, Russia) is described based manus fragments, caudal vertebrae, and imprints of horn scales. The new form is similar in morphology to Nqwebasaurus thwazi de Klerk et al., 2000 from the Lower Cretaceous of South Africa and assigned to the family Nqwebasauridae fam. nov. (Ornithomimosauria, Theropoda). It is proposed that nqwebasaurids searched for relatively small prey in the water column.
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Ceratosauria represents the first widespread and diverse radiation of theropod dinosaurs comprising two main sister clades, Neoceratosauria and Coelophysoidea. This chapter discusses the diagnostic features, phylogenetic placement, and paleobiology of ceratosaurians. The fossil record for Ceratosauria spans a minimum of 155 million years, from the late Carnian of the Late Triassic to the end of the Cretaceous. Ceratosaurs had an essentially global distribution, their remains being found on every continent except Australia and Antarctica. Ceratosaurs evolved into a broad range of sizes and body forms, from lightly built, diminutive taxa such as Segisaurus (1 to 1.5 m in length) to the large abelisaurids, such as Carnotaurus (10 to 11 m). Several coelophysoid taxa were collected from mass burials, where multiple individuals were preserved together. In particular, Syntarsus rhodesiensis is known from at least thirty individuals found at localities in Zimbabwe and South Africa.
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In this article, we develop a new reconstruction of the pelvic and hindlimb muscles of the large theropod dinosaur Tyrannosaurus rex. Our new reconstruction relies primarily on direct examination of both extant and fossil turtles, lepidosaurs, and archosaurs. These observations are placed into a phylogenetic context and data from extant taxa are used to constrain inferences concerning the soft-tissue structures in T. rex. Using this extant phylogenetic bracket, we are able to offer well-supported inferences concerning most of the hindlimb musculature in this taxon. We also refrain from making any inferences for certain muscles where the resulting optimizations are ambiguous. This reconstruction differs from several previous attempts and we evaluate these discrepancies. In addition to providing a new and more detailed understanding of the hindlimb morphology of T. rex--the largest known terrestrial biped--this reconstruction also helps to clarify the sequence of character-state change along the line to extant birds.
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Abelisaurids are a clade of large, bizarre predatory dinosaurs, most notable for their high, short skulls and extremely reduced forelimbs. They were common in Gondwana during the Cretaceous, but exceedingly rare in the Northern Hemisphere. The oldest definitive abelisaurids so far come from the late Early Cretaceous of South America and Africa, and the early evolutionary history of the clade is still poorly known. Here, we report a new abelisaurid from the Middle Jurassic of Patagonia, Eoabelisaurus mefi gen. et sp. nov., which predates the so far oldest known secure member of this lineage by more than 40 Myr. The almost complete skeleton reveals the earliest evolutionary stages of the distinctive features of abelisaurids, such as the modification of the forelimb, which started with a reduction of the distal elements. The find underlines the explosive radiation of theropod dinosaurs in the Middle Jurassic and indicates an unexpected diversity of ceratosaurs at that time. The apparent endemism of abelisauroids to southern Gondwana during Pangean times might be due to the presence of a large, central Gondwanan desert. This indicates that, apart from continent-scale geography, aspects such as regional geography and climate are important to reconstruct the biogeographical history of Mesozoic vertebrates.
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The evolution of birds from theropod dinosaurs was one of the great evolutionary transitions in the history of life [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 and 22]. The macroevolutionary tempo and mode of this transition is poorly studied, which is surprising because it may offer key insight into major questions in evolutionary biology, particularly whether the origins of evolutionary novelties or new ecological opportunities are associated with unusually elevated “bursts” of evolution [23 and 24]. We present a comprehensive phylogeny placing birds within the context of theropod evolution and quantify rates of morphological evolution and changes in overall morphological disparity across the dinosaur-bird transition. Birds evolved significantly faster than other theropods, but they are indistinguishable from their closest relatives in morphospace. Our results demonstrate that the rise of birds was a complex process: birds are a continuum of millions of years of theropod evolution, and there was no great jump between nonbirds and birds in morphospace, but once the avian body plan was gradually assembled, birds experienced an early burst of rapid anatomical evolution. This suggests that high rates of morphological evolution after the development of a novel body plan may be a common feature of macroevolution, as first hypothesized by G.G. Simpson more than 60 years ago [25].
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Early Cretaceous ornithomimosaurian theropod dinosaurs have been reported from various localities in Asia, whereas they remain poorly represented and extremely rare in North America, Africa and Europe. So far, the only known European ornithomimosaur is Pelecanimimus from the Barremian of Spain. The recent discovery in southwestern France of the Angeac bone bed, which has yielded several hundred ornithomimosaur bones, sheds new light on the ornithomimosaurian fossil record. Based on this new material, we re-evaluate here the systematic position of various isolated theropod bones from the Wealden of England, including historical taxa of uncertain affinities. Based on a unique combination of derived characters, Thecocoelurus and Valdoraptor are linked to the Angeac taxon but are considered to be nomina dubia. Valdoraptor from the Valanginian of West Sussex appears to be the oldest known ornithomimosaur together with the contemporaneous Nqwebasaurus from South Africa. Ornithomimosaurs were a common component of the Early Cretaceous European dinosaur fauna. Their presence in Spain, France and England further strengthens the palaeobiogeographic affinities of the European fossil biota with that of Asia during this period.
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A new theropod Abelisauridae is described, Ekrixinatosaurustinis novasi gen. et sp. nov., of northwestern Patagonia (Neuquén Province, Argentina). A preliminar cladistic analysis placed Ekrixinatosaurus together with Majungatholus and Carnotaurini; and the sister group is Ilokelesia. The presence of this specimen in Albian-Cenomarúan beds allows us to support the early divergence (pre-Senonian) of this clade, and the hypothesis of the presence of Abelisauridae in continental Africa. The present distribution of Abelisauridae indicates: 1) a vicariance of this clade based on a pre-Cenomanian pan-Gondwanic distribution; 2) dispersion throughout terrestrial bridges. In both cases, the absence of Abelisauridae in continental Africa can be considered a bias of the fossil record.
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Quilmesaurus curriei Coria, 2001 (Dinosauria, Theropoda). Its taxonomic validity and phylogenetic relationships. A comparative analysis of the Cretaceous theropod Quilmesaurus curriei from the Río Negro province, Patagonia, Argentina was performed in order to elucidate its phylogenetic relationships. Quilmesaurus was considered as basal Tetanurae by Coria (2001), however, Kellner & Campos (2002) suggested that this theropod could be a possible Abelisauria. In our analysis, we observed that the lack of fusion of the tibia with the astragalus-calcaneum is not an exclusive character for Ceratosauria; moreover, the mediodistal crest of femur is commonly well developed in Abelisauroidea. The great development of the distally expanded cnemial crest and the asymmetrical distal end of the tibia are characteristics of Abelisauridae. Finally, other characters like a distally directed process at the end of the cnemial crest and the asymmetry in the origin of the expansion of the malleolii in distal tibia are regarded as synapomorphies of Carnotaurinae. Therefore, Quilmesaurus curriei is considered to belong to Abelisauridae, and it is possibly a member of Carnotaurinae. On the basis of the available evidence, it is not possible to identify autapomorphic characters that allow validating Quilmesaurus curriei, and for this reason we consider it as a nomen vanum.
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The Abelisauridae are a family of mainly Cretaceous theropod dinosaurs with a wide distribution across the Gondwanan land masses. Although their presence in Europe was reported twenty-five years ago, it has often been considered as controversial largely because of the incompleteness of the available speci-mens. We report here the discovery of well-preserved abelisaurid material, including a highly diagnostic braincase, at a Late Cretaceous (late Campanian) locality in the Aix-en-Provence Basin, near the eponym city in south-eastern France. A new abelisaurid taxon is erected, Arcovenator escotae gen. nov., sp. nov., on the basis of cranial and postcranial material. A phylogenetic analysis reveals that the new Abelisauridae from Provence is more closely related to taxa from India and Madagascar than to South American forms. Moreover, Genusaurus, Tarascosaurus and the previous Late Cretaceous discoveries are identified as basal abelisaurids. Contrary to previously proposed palaeobiogeographical models of abelisaurid evolution, the presence of the new taxon in Europe suggests that Europe and Africa may have played a major role in abelisaurid dispersal, which apparently involved crossing marine barriers.
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Patagonia has yielded the most comprehensive fossil record of Cretaceous theropods from Gondwana, consisting of 31 nominal species belonging to singleton taxa and six families: Abelisauridae, Noasauridae, Carcharodontosauridae, Megaraptoridae nov. fam., Alvarezsauridae, and Unenlagiidae. They provide anatomical information that allows improved interpretation of theropods discovered in other regions of Gondwana. Abelisauroids are the best represented theropods in Patagonia. They underwent an evolutionary radiation documented from the Early Cretaceous through to the latest Cretaceous, and are represented by the clades Abelisauridae and Noasauridae. Patagonian carcharodontosaurids are known from three taxa (Tyrannotitan, Giganotosaurus and Mapusaurus), as well as from isolated teeth, collected from Aptian to Cenomanian beds. These allosauroids constituted the top predators during the mid-Cretaceous, during which gigantic titanosaur sauropods were the largest herbivores. Megaraptorans have become better documented in recent years with the discovery of more complete remains. Megaraptor, Aerosteon and Orkoraptor have been described from Cretaceous beds from Argentina, and these taxa exhibit close relationships with the Aptian genera Australovenator, from Australia, and Fukuiraptor, from Japan. The Gondwanan megaraptorans are gathered into the new family Megaraptoridae, and the Asiatic Fukuiraptor is recovered as the immediate sister taxon of this clade. Although megaraptorans have been recently interpreted as members of Allosauroidea, we present evidence that they are deeply nested within Coelurosauria. Moreover, anatomical information supports Megaraptora as more closely related to the Asiamerican Tyrannosauridae than thought. Megaraptorans improve our knowledge about the scarcely documented basal radiation of Gondwanan coelurosaurs and tyrannosauroids as a whole. Information at hand indicates that South America was a cradle for the evolutionary radiation for different coelurosaurian lineages, including some basal forms (e.g., Bicentenaria, Aniksosaurus), megaraptorans, alvarezsaurids less derived than those of Laurasia, and unenlagiids, revealing that Gondwanan coelurosaurs played sharply differing ecological roles, and that they were taxonomically as diverse as in the northern continents. The unenlagiids represent an endemic South American clade that has been recently found to be more closely related to birds than to dromaeosaurid theropods. Analysis of the theropod fossil record from Gondwana shows the highest peak of origination index occurred during the Aptian–Albian and a less intense one in the Campanian time spans. Additionally, peaks of extinction index are recognized for the Cenomanian and Turonian–Coniacian time spans. In comparison, the Laurasian pattern differs from that of Gondwana in the presence of an older extinction event during the Aptian–Albian time-span and a high origination rate during the Cenomanian time-bin. Both Laurasian and Gondwanan theropod records show a peak of origination rates during the Campanian.
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We performed additional preparation on the holotype skeleton of Nqwebasaurus thwazi and discovered new skeletal material. We describe this material, which includes a maxilla with small, conical, unserrated teeth and bones of the braincase, as well as parts of the holotype postcranial anatomy that were previously poorly documented. We incorporate this new anatomical information into a broadly sampled matrix designed to test theropod relationships. Our phylogenetic results hypothesize that Nqwebasaurus is the basalmost ornithomimosaur, and recover numerous characters supporting this relationship, including features of the maxilla, frontal, dentition, axial skeleton, forelimb and hindlimb. Nqwebasaurus is the first African ornithomimosaur and the first Gondwanan member of this group known from articulated skeletal material, supporting the hypothesis that coelurosaurian groups were cosmopolitan during their early evolutionary history. The presence of reduced dentition and a gastric mill in Nqwebasaurus strongly suggest that this taxon was herbivorous.
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We review here the phylogenetic relationships of a theropod distal end of tibia (MB. R.2351) from the Middle Jurassic Stonesfield Slate (Taunton Formation, middle Bathonian) of Oxfordshire, England. This specimen was previously described as a small basal tetanuran, but our reinterpretation suggests that it was an early member of the Abelisauroidea. The new assignment is supported by the presence of an apomorphic vertical facet for the reception of the ascending process of the astragalus, sub-rectangular anterior scar of the astragalar ascending process, median vertical ridge in the scar for the reception of the ascending process of the astragalus, and posterolateral process not distinctly offset from the lateral margin of the shaft. In particular, the Stonesfield specimen shares an overall morphology and a unique combination of apomorphies with the Middle Jurassic Australian abelisauroid Ozraptor. Nevertheless, both specimens differ in some punctual features. MB. R.2351 constitutes the oldest evidence of an abelisauroid outside Gondwana and indicates that the group had achieved a Pangean distribution during, at least, the Middle Jurassic. Thus, the initial diversification of abelisauroids would have occurred earlier than previously thought. Accordingly, the Middle and Late Jurassic Pangean distribution of abelisauroids implies that the absence of the group in Cretaceous Asiamerican assemblages would reflect a regional extinction, in which a competitive replacement with coelurosaurs (e.g. tyrannosauroids) is surely one of the hypotheses that should be tested in future studies.
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At least fourteen ornithomimid skeletons were recovered from the Upper Cretaceous Ulansuhai Formation in Nei Mongol (Inner Mongolia) Autonomous Region of China. They are assigned to a new genus and species. Sinornithomimus dongi. The anatomy of the species is described. Comparative and phylogenetic studies of ornithomimosaurs prove that these skeletons represent a new taxon that is more derived than Archaeornithomimus and more basal than the clade of [(Anserimimus + Gallimimus) + [Struthiomimus + (Dromiceiomimus + Ornithomimus)]]. The phylogenetic analysis suggests that the structure of the hand is similar to Archaeornithomimus and represents an intermediate condition between the primitive (Harpymimus) and the derived (Anserimimus. Gallimimus, Struthiomimus, Dromiceiomimus, and Ornithomimus) conditions. The monophyly of Ornithomimidae is supported by a single synapomorphy (arctometatarsalian condition) in this analysis, indicating that the family is not as strongly supported as previously suggested. The analysis also implies that the shape of the rhamphotheca in North American taxa may have been different from that in Asian taxa. Previous study suggests herbivorous habits of this dinosaur based on characteristics of the gastroliths. The skeletons of Sinornithomimus were collected from a single monospecific bonebed with a high ratio of juvenile individuals (11 of the 14), suggesting gregarious behavior for protection from predators. The abundance of juveniles indicates high mortality of juveniles or a catastrophic mass mortality of a population with a high proportion of juveniles. An increase in the relative ratio of the tibia to femur through the ontogeny of Sinornithomimus suggests higher cursoriality in adult individuals than in juveniles.
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Here we describe a new theropod, Bicentenaria argentina nov. gen. et nov. sp., from the early Late Cretaceous of Patagonia. It is represented by more than a hundred bones belonging to different sized individu- als, which were buried together in disarticulation after little transportation. The available association of skel- etal elements suggests a gregarious behaviour for Bicentenaria, an ethological trait also recorded among other theropod clades. Increasing documentation of monospecific assemblages of different groups of theropods suggests that a gregarious behaviour may have constituted the ancestral condition for Theropoda, at least. Bicentenaria characterizes for the surangular bone with a high dorsal margin and a prominent lateral shelf, a retroarticular process that is low, wide and spoon-shaped, and quadrate bone with its lateral condyle larger than the medial one. Phylogenetic analysis found the Chinese Tugulusaurus and the Patagonian Bicentenaria as successive sis- ter taxa of all other coelurosaurs, thus revealing the importance of the new taxon in the understanding of the early diversification of Coelurosauria. In particular, Bicentenaria amplifies the array of basal coelurosaurs that inhabited Gondwana during the Cretaceous, also including compsognathids, Aniksosaurus and Santanaraptor. Although still restricted to a handful of forms, available information indicates that Gondwana was a cradle for the evolution of different lineages of basal coelurosaurs, different from those documented in Upper Cretaceous beds in the northern landmasses. Analysis of body size distribution in averostran theropods results in the identi- fication of two main episodes of drastic size reduction in the evolutionary history of Coelurosauria: one occurred at the initial radiation of the group (as represented by Bicentenaria, Zuolong, Tugulusaurus, compsognathids, and Aniksosaurus), and a second episode occurred at the early diverification of Paraves or avialans. Reduction in body size may have allowed adult coelurosaurians to exploit ecological niches not occupied before by larger basal averostrans.
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We report the well preserved skeleton of a small theropod dinosaur, Nqwebasaurus thwazi, gen. et sp. nov., from the Lower Cretaceous Kirkwood Formation of South Africa. Nqwebasaurus has an elongate three-digit manus with a partially opposable first digit, a long and slender pes with a highly reduced metatarsal IV, and preserves gastroliths (stomach stones) in its abdominal region. As a basal coelurosaurian, Nqwebasaurus pushes back the Gondwanan record of this derived group of tetanuran theropods approximately 50 million years. This confirms that coelurosaurians were present on the Gondwana supercontinent well before its main phase of fragmentation and supports the hypothesis that this clade could have achieved a global distribution early in their evolution. Nqwebasaurus is one of the most complete and best preserved Cretaceous theropods described thus far from Africa.
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We describe the osteology of the new small theropod dinosaur Masiakasaurus knopfleri, from the Late Cretaceous Maevarano Formation of northwestern Madagascar. Approximately 40% of the skeleton is known, including parts of the jaws, axial column, forelimb, pelvic girdle, and hind limb. The jaws of Masiakasaurus are remarkably derived, bearing a heterodont, procumbent dentition that is unknown elsewhere among dinosaurs. The vertebrae are similar to those of abelisauroids in the reduction of the neural spine, lack of pleurocoelous fossae on the centrum, and extensively pneumatized neural arch. The limb skeleton is relatively gracile and bears numerous abelisauroid synapo-morphies, including a rounded humeral head, peg-and-socket iliac-pubic articulation, prominent femoral medial epi-condyle, expanded tibial cnemial crest, and double-grooved pedal unguals. The femora and tibiae show evidence of dimorphism. More specific features shared between Masiakasaurus, the Argentine Noasaurus, and the Indian Laevi-suchus suggest that these taxa form a clade (Noasauridae) within Abelisauroidea. This is supported by a cladistic phylogenetic analysis of 158 characters and 23 theropod taxa. Additionally, Ceratosauria is rendered paraphyletic in favor of a sister-taxon relationship between Neoceratosauria and Tetanurae that is exclusive of Coelophysoidea. The unique dental and jaw specializations of Masiakasaurus suggest deviation from the typical theropod diet. Finally, the distribution of noasaurids further supports a shared biogeographic history between South America, Madagascar, and India into the Late Cretaceous.
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The appendicular skeleton of the abelisaurid theropod Majungasaurus crenatissimus (Depéret, 1896) Lavocat, 1955 is described for the first time. The available materials include an incomplete pectoral girdle and forelimb, along with the ilium and a nearly complete hind limb. These materials display a number of ceratosaur, abelisauroid, and abelisaurid synapomorphies, supporting the phylogenetic placement of Majungasaurus based previously on cranial anatomy. As in Ceratosaurus and Carnotaurus, the scapular blade is relatively wide and has a pronounced dorsal lip over the glenoid. The humerus is short and bears a globular head, but is more slender than in Carnotaurus. The ilium has a preacetabular hook, a strong supraacetabular crest, a notched posterior margin, and peg-and-socket articulations with both the pubis and ischium. Hind limb elements are proportionally stocky, as in some other abelisaurids. The femur lacks a trochanteric shelf, the tibia has a greatly enlarged cnemial crest, and the fibula bears a deep, posteriorly facing medial fossa. The abelisaurid astragalocalcaneum is described here in detail for the first time, and is more similar to that of tetanurans than to those of coelophysoids. Taken together, these materials illustrate that the appendicular skeleton of abelisaurids was specialized over the typical condition in basal theropods, particularly through the development of enlarged muscle attachment processes.
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SYNOPSIS Recent discoveries and analyses have drawn increased attention to Ceratosauria, a taxo-nomically and morphologically diverse group of basal theropods. By the time of its first appearance in the Late Jurassic, the group was probably globally distributed. This pattern eventually gave way to a primarily Gondwanan distribution by the Late Cretaceous. Ceratosaurs are one of several focal groups for studies of Cretaceous palaeobiogeography and their often bizarre morphological develop-ments highlight their distinctiveness. Unfortunately, lack of phylogenetic resolution, shifting views of which taxa fall within Ceratosauria and minimal overlap in coverage between systematic studies, have made it difficult to explicate any of these important evolutionary patterns. Although many taxa are fragmentary, an increase in new, more complete forms has clarified much of ceratosaur anatomy, allowed the identification of additional materials and increased our ability to compare specimens and taxa. We studied nearly 40 ceratosaurs from the Late Jurassic–Late Cretaceous of North and South America, Europe, Africa, India and Madagascar, ultimately selecting 18 for a new cladistic analysis. The results suggest that Elaphrosaurus and its relatives are the most basal ceratosaurs, followed by Ceratosaurus and Noasauridae + Abelisauridae (= Abelisauroidea). Several additional forms were identified as noasaurids, including Genusaurus. Within Abelisauridae, our analysis reveals a clade including Majungasaurus and the Indian forms, as well as a more weakly supported clade comprising Carnotaurus and Ilokelesia. These results greatly clarify the sequence of character acquisition lead-ing to, and within, Abelisauroidea. Thanks to new noasaurid materials (particularly Masiakasaurus), numerous formerly ambiguous characters can now be resolved as either abelisaurid, noasaurid or abelisauroid synapomorphies. Skull and forelimb shortening, for example, now appear to be features confined to Abelisauridae. Nevertheless, a great deal of phylogenetic resolution is lacking, particu-larly among noasaurids, which hampers attempts to glean meaningful biogeographical information from the phylogeny. As a result, temporal and geographical sampling biases are probably contributing to the apparent patterns in the data and we suggest that definitive answers must await new discover-ies. None of the recent ceratosaurian discoveries bear directly on the controversy surrounding latest Cretaceous ceratosaur biogeography.
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Osteology of the noasaurid theropod Masiakasaurus knopfleri Sampson et al., 2001, is now two-thirds complete. We describe Masiakasaurus knopfleri in detail on the basis of examination of new specimens and emphasis on previously unknown elements. The skull is anteroposteriorly long but low in height, unlike the foreshortened abelisaurid condition. Premaxillary teeth are procumbent, like those of the dentary. Frontal bones are flat and unornamented, but the lacrimal and postorbital exhibit surface texturing. The braincase resembles that of abelisaurids but is more highly pneumatized. The neck is curved anteriorly but horizontal posteriorly, and it transitions to the trunk without significant proportional changes. Centrum pneumaticity appears confined to the neck and anterior trunk. The sacrum includes six vertebrae, and the expanded transverse processes of caudal vertebrae may articulate with caudal ribs. The scapulocoracoid is large and broad. The ilium is both anteroposteriorly long and dorsoventrally deep, and it bears pegs for articulation with sockets on the pubis and ischium, as in other ceratosaurs. The nearly complete pes shows no particular locomotor specializations and allows reinterpretation of the “raptorial” pedal ungual of Noasaurus as a manual element. These new specimens also illuminate the morphology of other noasaurids, especially those from the Lameta Formation. In addition to Madagascar, noasaurids are known from Europe, India, South America, and Africa, spanning at least Aptian–Albian through Maastrichtian time. The new materials of Masiakasaurus increase character resolution within Abelisauroidea, identifying many formerly equivocal features as synapomorphies of the nodes Noasauridae, Abelisauridae, or Abelisauroidea. Unfortunately, the fragmentary nature of nearly all other noasaurids obviates any meaningful ingroup resolution, and as a result no particular evolutionary or biogeographic scenarios for the clade can presently be supported (or rejected) with confidence.
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Compsognathus longipes sits at an important point in theropod evolution at the base of Coelurosauria. Despite its relative completeness and oft-cited morphology, however, the manual morphology has been unclear. This work provides the first detailed study of the morphology of the manus of Compsognathus longipes. It shows that Compsognathus longipes had two fully formed functional digits as well as a reduced, perhaps even non-functional, third digit. That conclusion runs counter to the usual interpretation that Compsognathus longipes had only two phalanges, rather than the expected complement of three, in digit II. This work also identifies a unique suite of metacarpal I morphologies that are used to diagnose a subclade among species often referred to as ‘Compsognathidae’. These features are used to construct an apomorphy-based definition of a new clade name: Compsognathidae. © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 149, 569–581.
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Systematic excavations in the fluvial mudstone unit of the Upper Cretaceous Lameta Formation near Rahioli village in Kheda District, Gujarat, have yielded a large-bodied (~8 m long) abelisaurid theropod, Rahiolisaurus gujaratensis, gen. et sp. nov. Abundant skeletal remains represent this new genus and species. Rahiolisaurus provides novel information on foot morphology, hitherto little known in other abelisaurids. Rahiolisaurus gujaratensis is a gracile and slender-limbed abelisaurid that appears to be a distinctive taxon from the sympatric species Rajasaurus narmadensis.
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The Early Cretaceous fauna of Victoria, Australia, provides unique data on the composition of high latitude southern hemisphere dinosaurs. We describe and review theropod dinosaur postcranial remains from the Aptian-Albian Otway and Strzelecki groups, based on at least 37 isolated bones, and more than 90 teeth from the Flat Rocks locality. Several specimens of medium- and large-bodied individuals (estimated up to ~8.5 metres long) represent allosauroids. Tyrannosauroids are represented by elements indicating medium body sizes (~3 metres long), likely including the holotype femur of Timimus hermani, and a single cervical vertebra represents a juvenile spinosaurid. Single specimens representing medium- and small-bodied theropods may be referrable to Ceratosauria, Ornithomimosauria, a basal coelurosaur, and at least three taxa within Maniraptora. Thus, nine theropod taxa may have been present. Alternatively, four distinct dorsal vertebrae indicate a minimum of four taxa. However, because most taxa are known from single bones, it is likely that small-bodied theropod diversity remains underestimated. The high abundance of allosauroids and basal coelurosaurs (including tyrannosauroids and possibly ornithomimosaurs), and the relative rarity of ceratosaurs, is strikingly dissimilar to penecontemporaneous dinosaur faunas of Africa and South America, which represent an arid, lower-latitude biome. Similarities between dinosaur faunas of Victoria and the northern continents concern the proportional representatation of higher clades, and may result from the prevailing temperate-polar climate of Australia, especially at high latitudes in Victoria, which is similar to the predominant warm-temperate climate of Laurasia, but distinct from the arid climate zone that covered extensive areas of Gondwana. Most dinosaur groups probably attained a near-cosmopolitan distribution in the Jurassic, prior to fragmentation of the Pangaean supercontinent, and some aspects of the hallmark 'Gondwanan' fauna of South America and Africa may therefore reflect climate-driven provinciality, not vicariant evolution driven by continental fragmentation. However, vicariance may still be detected at lower phylogenetic levels.
Article
The complete osteology of the abelisaurid Viavenator exxoni, from the Bajo de la Carpa Formation (Santonian, Upper Cretaceous) is described. Viavenator is characterized by a series of autapomorphies, including: transversely compressed parietal depressions on both sides of the supraoccipital crest; ventral edges of the paraoccipital processes located above the level of the dorsal edge of the occipital condyle; basioccipital-opisthotic complex about two and a half times the width and almost twice the height of the occipital condyle, in posterior view; well-developed crest below the occipital condyle, diverging ventrally and defining the subcondylar recess; deeply excavated and sub-circular basisphenoidal recess, with its major axis transversely oriented; basipterygoid processes horizontally placed with respect to the cranial roof and located slightly dorsally to the basal tubera; mid and posterior cervical centra with slightly convex lateral and ventral surfaces; hyposphene-hypanthrum articular complex present from dorsal 2 onward; presence of an interspinous accessory articular system in middle and posterior dorsal vertebrae; presence of a pair of pneumatic foramina within the prespinal fossa in anterior caudal vertebrae; distal end of the scapular blade posteriorly curved. Particularly, Viavenator shows plesiomorphic cranial characters, i.e. flat frontals lacking domes or horns, combined with derived postcranial characters, e.g. the interspinous accessory joint system of dorsal vertebrae. This combination between plesiomorphic and derived traits suggests that Viavenator is a transitional form, which is an idea supported by its intermediate stratigraphic and phylogenetic placement between the basal and older (e.g. Skorpiovenator, Ilokelesia) and derived and younger members of the clade (e.g. Aucasaurus, Carnotaurus).
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Theropod dinosaurs from the Late Jurassic of Gondwana are still poorly known, with Elaphrosaurus bambergi Janensch, 1920, from the late Kimmeridgian of Tendaguru, Tanzania, being the only taxon represented by more than isolated remains from Africa. Having long been considered a coelurosaurian, more specifically an ornithomimosaur, Elaphrosaurus is currently regarded as a basal ceratosaur. Here, we revise the osteology and phylogenetic position of this important taxon. Elaphrosaurus shows many unusual osteological characters, including extremely elongated and constricted cervical vertebrae, an expansive shoulder girdle with strongly modified forelimbs, a relatively small ilium, and elongate hindlimbs with a very small ascending process of the astragalus that is fused to the tibia. We found this taxon to share many derived characters with noasaurids, such as: strongly elongate cervical and dorsal vertebrae; low, rectangular neural spines in the mid-caudal vertebrae; presence of only an anterior centrodiapophyseal lamina in anterior caudal vertebrae; presence of a wide, U-shaped notch between the glenoid and the anteroventral hook in the coracoid; a laterally flared postacetabular blade of the ilium; a flat anterior side of the distal tibia; and a reduced shaft of metatarsal II. Our analysis placed Elaphrosaurus within a dichotomous Noasauridae as part of a Jurassic subclade, here termed Elaphrosaurinae, that otherwise includes taxa from eastern Asia. These results underscore the long and complex evolutionary history of abelisauroids, which is still only beginning to be understood.
Article
Recent fieldwork in Upper Cretaceous terrestrial deposits in northwestern Madagascar has yielded a remarkable diversity of vertebrates, including several specimens of the abelisaurid theropod Majungasaurus crenatissimus (Depéret, 1896) Lavocat, 1955. Featured among the discoveries is an exquisite specimen (UA 8678) that preserves a virtually complete precaudal vertebral column, numerous costal elements, and portions of the skull and appendicular skeleton. This contribution represents the first description highlighting the postcranial axial skeleton of Majungasaurus. Owing to the completeness and quality of preservation, this specimen allows an examination of the serial transformation of features along the length of the axial skeleton, including a detailed analysis of postcranial pneumaticity in a nontetanuran theropod. Notable features of Majungasaurus include pneumatic cervical ribs with caudally bifurcate shafts and extensive pneumaticity of all postatlantal, precaudal vertebrae. Several postcranial features exhibited by Majungasaurus - including a well-developed cervical epipophysis, laterally expanded dorsal parapophysis, and sub-divided infradiapophyseal fossa in middle dorsal series - support previous phylogenetic studies placing it within Abelisauroidea and Abelisauridae. Majungasaurus (and abelisaurids generally) exhibit a robust cervical skeleton that features tightly interlocking cervical ribs, hyperossification of cervical rib shafts, and hypertrophied muscle attachment sites relative to other basal theropods. These features together highlight an axial core constructed to withstand high stresses, likely reflecting feeding adaptations for predation on large-bodied prey.
Chapter
Tetanurae comprised Carnosauria, a monophyletic group composed of Allosaurus, and Coelurosauria, containing modern birds and all taxa closer to modern birds than to Carnosauria. This chapter examines spinosauroids, carnosaurs, and basal coelurosaurs. Among the taxa in this chapter are the largest carnivorous dinosaurs found in Middle Jurassic through early Late Cretaceous faunal assemblages. The chapter also discusses some of the smallest nonavian dinosaurs, including Compsognathus and Sinosauropteryx.
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Abelisauroidea are a recently recognized clade of theropod dinosaurs that have a predominantly Gondwanan distribution. Recently, a distal theropod tibia from the Middle Jurassic of England was identified as an abelisauroid, representing one of the oldest records of the group in general and the only Jurassic occurrence in Europe. On this basis, rapid radiation of abelisauroid and a global distribution of this clade in the Jurassic were suggested. Here, the specimen in question is re-examined and the characters used for referral to the Abelisauroidea are re-evaluated. None of the proposed characters can be demonstrated to represent abelisauroid synapomorphies and all have a wider distribution; especially coelurosaurian theropods, which are known from contemporaneous beds in England, frequently show the same character combination. Thus, there is currently no secure evidence for the occurrence of abelisauroids in the Jurassic of the northern Hemisphere, and the early evolution of this clade remains poorly known. Furthermore, other fragmentarily known taxa previously referred to Abelisauroidea based on putative synapomorphies of the distal tibia, such as Ozraptor and Austrocheirus, should be considered as Theropoda indet.
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The main features of the phylogeny program TNT are discussed. Windows versions have a menu interface, while Macintosh and Linux versions are command-driven. The program can analyze data sets with discrete (additive, non-additive, step-matrix) as well as continuous characters (evaluated with Farris optimization). Effective analysis of large data sets can be carried out in reasonable times, and a number of methods to help identifying wildcard taxa in the case of ambiguous data sets are implemented. A variety of methods for diagnosing trees and exploring character evolution is available in TNT, and publication-quality tree-diagrams can be saved as metafiles. Through the use of a number of native commands and a simple but powerful scripting language, TNT allows the user an enormous flexibility in phylogenetic analyses or simulations. © The Willi Hennig Society 2008.
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