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A dicynodont-theropod association in the latest Triassic of Poland

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Dzik J., Sulej T., Niedźwiedzki G.

Acta Palaeontologica Polonica

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2008

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tom 53

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nr 4

It is generally accepted that during the Triassic the composition of tetrapod faunas underwent a series of fundamental transformations, mainly as a result of diversification of archosaurs and decline of therapsids (Benton 1994, 2004, 2006). The last herbivorous basal synapsids, dicynodonts, disappeared from the record in the early Norian of the Americas, about 220 Ma (Langer et al. 2007), being unknown from the Late Triassic of Europe. Here, we report a partially articulated skeleton and isolated bones of a giant rhino−size dicynodont in the Upper Triassic fluvial sediments at Lisowice (Lipie Śląskie clay−pit) in southern Poland. Paleobotanical data indicate an early Rhaetian age for the fauna (Dzik et al. 2008; Niedźwiedzki and Sulej 2008). The dicynodont bones are associated with bones of carnivorous dinosaurs, pterosaurs, as well as capitosaur and plagiosaur amphibians. Dicynodonts were represented in the Germanic Basin throughout the Late Triassic, as proven by findings of smaller dicynodonts in older deposits in the same area, associated there with temnospondyl amphibians. It appears, thus, that the fossil record of tetrapod succession in the Late Triassic was strongly controlled by ecological factors and biased by uneven representation of particular environments. The Lisowice assemblage proves that faunas dominated by dicynodonts did not entirely disappear at least until the end of the Triassic.

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Macroevolutionary and morphofunctional patterns in theropod skulls: A morphometric approach

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Foth C., Rauhut O. W. M.

Acta Palaeontologica Polonica

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2013

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tom 58

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nr 1

Theropod dinosaurs are one of the most remarkable lineages of terrestrial vertebrates in the Mesozoic, showing high taxo− nomic and ecological diversity. We investigate the cranial diversity of non−avian theropods and some basal birds, using geometric morphometrics to obtain insights into the evolutionary modifications of the skull. Theropod skulls mostly vary in the shape of the snout and length of the postorbital region (principal component [PC] 1), with further variation in orbit shape, depth of the postorbital region, and position of the jaw joint (PC 2 and PC 3). These results indicate that the cranial shape of theropods is closely correlated with phylogeny and dietary preference. Skull shapes of non−carnivorous taxa dif− fer significantly from carnivorous taxa, suggesting that dietary preference affects skull shape. Furthermore, we found a significant correlation between the first three PC axes and functional proxies (average maximum stress and an indicator of skull strength). Interestingly, basal birds occupy a large area within the morphospace, indicating a high cranial, and thus also ecological, diversity. However, we could include only a small number of basal avialan species, because their skulls are fragile and there are few good skull reconstructions. Taking the known diversity of basal birds from the Jehol biota into account, the present result might even underestimate the morphological diversity of basal avialans.

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New specimens of the crested theropod dinosaur Elmisaurus rarus from Mongolia

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Currie P. J., Funston G. F., Osmolska H.

Acta Palaeontologica Polonica

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2016

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tom 61

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nr 1

New specimens of Elmisaurus rarus from the Upper Cretaceous of Mongolia (Nemegt Formation) preserve bones not previously found in “elmisaurids” that help elucidate their relationships to Leptorhynchos elegans and other oviraptorosaurs. Elmisaurus rarus and the North American Leptorhynchos elegans are known from numerous but incomplete specimens that are closely related to, but nevertheless clearly distinguished from, Chirostenotes pergracilis and Epichirostenotes curriei. These specimens include the first known cranial bone attributed to Elmisaurus, the frontal, which clearly shows this animal had a cranial crest (most of which would have been formed by the nasal bones). The first vertebrae, scapula, femora, and tibiae from Elmisaurus are also described. The Elmisaurinae can be distinguished from the Caenagnathinae by the coossification of the tarsometatarsus and smaller size at maturity. Examination of oviraptorosaur hindlimbs reveals four distinct morphotypes, possibly attributable to paleoecological differences.

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The endocranium of the theropod dinosaur Ceratosaurus studied with computer tomography

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Sanders R. K., Smith D. K.

Acta Palaeontologica Polonica

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2005

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tom 50

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nr 3

A well preserved specimen of the theropod Ceratosaurusfrom the Upper Jurassic Morrison Formation of western Colorado was recently described and given the name C. magnicornis. The systematics of the genus is outside the scope of the present study but, as a generally accepted basal tetanuran, the braincase was CT scanned to provide a description of the endocranium, inner ear, pneumatic, and venous sinus systems in a primitive member of this clade. Five major subregions of the theropod endocranium are distinguished for the purpose of simplifying cranial computed tomographic interpretation and to provide a systematic means of comparison to other endocrania. The skull morphology of Ceratosaurus influences the overall braincase morphology and the number and distribution of the major foramina. The low pontine angle and relatively unflexed braincase is considered a more primitive character. The orientation of the horizontal semicircular canal confirms a rather horizontal and unerect posture of the head and neck. As in birds, the narrower skull morphology of Ceratosaurusis associated with fewer cranial nerve foramina. Additionally, the maxillary dominated dentigerous upper jaw of Ceratosaurusis felt to share with the alligator a large rostrally directed maxillary division of the trigeminal nerve and a small ophthalmic branch. The upper bill of birds, being dominated by the premaxillary and lacking teeth, is innervated predominantly by the ophthalmic division of the trigeminal nerve. For this reason, avian−based cranial nerve reconstructions are felt to be inappropriate for basal theropods.Ceratosaurusskull pneumatization and possible evidence of olfactory conchal structures is on the other hand very avian in character. Based on computed tomography, Ceratosaurusis determined to have possessed a typical basal theropod endocranium and bipedal vestibular system similar to Allosaurus.

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Allometric growth in the frontals of the Mongolian theropod dinosaur Tarbosaurus bataar

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Yun C.-G., Peters G. F., Currie P. J.

Acta Palaeontologica Polonica

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2022

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tom 67

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nr 3

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Fused and vaulted nasals of tyrannosaurid dinosaurs: Implications for cranial strength and feeding mechanics

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Snively E., Henderson D. M., Phillips D. S.

Acta Palaeontologica Polonica

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2006

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tom 51

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nr 3

Tyrannosaurid theropods display several unusual adaptations of the skulls and teeth. Their nasals are fused and vaulted, suggesting that these elements braced the cranium against high feeding forces. Exceptionally high strengths of maxillary teeth in Tyrannosaurus rex indicate that it could exert relatively greater feeding forces than other tyrannosaurids. Areas and second moments of area of the nasals, calculated from CT cross−sections, show higher nasal strengths for large tyrannosaurids than for Allosaurus fragilis. Cross−sectional geometry of theropod crania reveals high second moments of area in tyrannosaurids, with resulting high strengths in bending and torsion, when compared with the crania of similarly sized theropods. In tyrannosaurids trends of strength increase are positively allomeric and have similar allometric exponents, indicating correlated progression towards unusually high strengths of the feeding apparatus. Fused, arched nasals and broad crania of tyrannosaurids are consistent with deep bites that impacted bone and powerful lateral movements of the head for dismembering prey.

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A new large-bodied theropod dinosaur from the Middle Jurassic of Warwickshire, United Kingdom

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Benson R. B. J., Radley J. D.

Acta Palaeontologica Polonica

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2010

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tom 55

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nr 1

Previously undocumented postcranial material from the Chipping Norton Limestone Formation (Middle Jurassic: Lower Bathonian) of Cross Hands Quarry, near Little Compton, Warwickshire represents a new large−bodied theropod dinosaur, distinct from the contemporaneous Megalosaurus bucklandii. Cruxicheiros newmanorum gen. et sp. nov. is diagnosed by a single autapomorphy, the presence of a proximomedially inclined ridge within the groove that marks the lateral extent of the posterior flange of the femoral caput (trochanteric fossa). C. newmanorum shows three tetanuran features: widely separated cervical zygapophyses, a swollen ridge on the lateral surface of the iliac blade and an anterior spur of the caudal neural spines. However, due to fragmentary preservation its affinities within Tetanurae remain uncertain: phylogenetic analysis places it as the most basal tetanuran, the most basal megalosauroid (= spinosauroid) or the most basal neotetanuran.

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Large theropod dinosaur footprint associations in western Gondwana: Behavioural and palaeogeographic implications

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Moreno K., de Valais S., Blanco N., Tomlinson A. J., Jacay J., Calvo J. O.

Acta Palaeontologica Polonica

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2012

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tom 57

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nr 1

In modern terrestrial ecosystems, the population size of large predators is low, and a similar pattern has usually been assumed for dinosaurs. However, fossil finds of monospecific, large theropod accumulations suggest that population dynamics were more complex. Here, we report two Early Cretaceous tracksites dominated by large theropod footprints, in Querulpa Chico (Peru) and Chacarilla (Chile). The two sites correspond to distinct depositional environments—tidal basin/delta (Querulpa Chico) and meandering river (Chacarilla)—with both subject to extensive arid or semiarid palaeoclimatic conditions. Although most trackways show no preferred orientation, a clear relationship between two trackmakers is observed in one instance. This observation, coupled with the high abundance of trackways belonging to distinct large theropods, and the exclusion of tracks of other animals, suggests some degree of grouping behaviour. The presence of freshwater sources in a dry climate and perhaps social behaviour such as pair bonding may have promoted interactions between large carnivores. Further, the occurrence of these two tracksites confirms that large theropod dinosaurs, possibly spinosaurids and/or carcharodontosaurids, existed on the western margin of Gondwana as early as the earliest Cretaceous.

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A reassessment of Kelmayisaurus petrolicus, a large theropod dinosaur from the Early Cretaceous of China

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Brusatte S. L., Benson R. B. J., Xu X.

Acta Palaeontologica Polonica

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2012

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tom 57

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nr 1

The Early Cretaceous fossil record of large−bodied theropods from Asia is poor, hindering comparison of Asian predatory dinosaur faunas with those from other continents. One of the few large Asian theropod specimens from this interval is a partial skull (maxilla and dentary) from the Lianmugin Formation (?Valanginian–Albian), the holotype of Kelmayisaurus petrolicus. Most authors have either considered this specimen as an indeterminate basal tetanuran or a nomen dubium. We redescribe K. petrolicus and note that it possesses a single autapomorphy (a deep accessory groove on the lateral surface of the anterior dentary), as well as a unique combination of characters that differentiates it from other theropods, affirming its validity. A phylogenetic analysis recovers K. petrolicus as a basal carcharodontosaurid, which is supported by various features: very deep interdental plates (a carcharodontosaurid synapomorphy), fused interdental plates (present in carchardontosaurids and a limited number of other theropods), and the absence of diagnostic features of other clades of large−bodied theropods such as abelisaurids, megalosauroids, and coelurosaurs. As such,Kelmayisaurusis the second known carcharodontosaurid from Asia, and further evidence that this clade represented a global radiation of large−bodied predators during the Early–mid Cretaceous.

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Giant theropod dinosaurs from Asia and North America: skulls of Tarbosaurus bataar and Tyrannosaurus rex compared

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Hurum J. H., Sabath K.

Acta Palaeontologica Polonica

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2003

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tom 48

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nr 2

The skull of a newly prepared Tarbosaurus bataar is described bone by bone and compared with a disarticulated skull of Tyrannosaurus rex. Both Tarbosaurus bataar and Tyrannosaurus rex skulls are deep in lateral view. In dorsal view, the skull of T. rex is extremely broad posteriorly but narrows towards the snout; in Ta. bataarthe skull is narrower (especially in its ventral part: the premaxilla, maxilla, jugal, and the quadrate complex), and the expansion of the posterior half of the skull is less abrupt. The slender snout of Ta. bataaris reminiscent of more primitive North American tyrannosaurids. The most obvious difference between T. rex and Ta. bataar is the doming of the nasal in Ta. bataar which is high between the lacrimals and is less attached to the other bones of the skull, than in most tyrannosaurids. This is because of a shift in the handling of the crushing bite in Ta. bataar. We propose a paleogeographically based division of the Tyrannosaurinae into the Asiatic forms (Tarbosaurus and possibly Alioramus) and North American forms (Daspletosaurus and Tyrannosaurus). The division is supported by differences in anatomy of the two groups: in Asiatic forms the nasal is excluded from the major series of bones participating in deflecting the impact in the upper jaw and the dentary−angular interlocking makes a more rigid lower jaw.

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Gigantic footprint of a theropod dinosaur in the Early Jurassic of Poland

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Gierlinski G., Niedzwiedzki G., Pienkowski G.

Acta Palaeontologica Polonica

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2001

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tom 46

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nr 3

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Crouching theropod and Navahopus sauropodomorph tracks from the Early Jurassic Navajo Sandstone of USA

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Milan J., Loope D. B., Bromley R. G.

Acta Palaeontologica Polonica

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2008

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tom 53

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nr 2

Numerous tracks and trackways are preserved in the a cross−strata of the Lower Jurassic Navajo Sandstone of northern Arizona and southern Utah, USA. Tracks and trackways of small theropod dinosaurs are particularly abundant within one 10−m−thick interval. This paper describes a crouching trace from a theropod dinosaur that shows impressions of all four limbs, the ischial callosity, the tail, and tracks leading to and away from the crouching site, and revises the interpretation of a well preserved trackway hitherto referred to the synapsid ichnogenus Brasilichnium and here considered to be from a sauropodomorph dinosaur. It is named Navahopus coyoteensisisp. nov. on the basis of morphological differences from the type ichnospecies N. falcipollex. The ichnofamily Navahopodidae is revised to include Tetrasauropous unguiferus, Navahopus falcipollex, and N. coyoteensis.

Ograniczanie wyników

A dicynodont-theropod association in the latest Triassic of Poland

Macroevolutionary and morphofunctional patterns in theropod skulls: A morphometric approach

New specimens of the crested theropod dinosaur Elmisaurus rarus from Mongolia

The endocranium of the theropod dinosaur Ceratosaurus studied with computer tomography

Allometric growth in the frontals of the Mongolian theropod dinosaur Tarbosaurus bataar

Fused and vaulted nasals of tyrannosaurid dinosaurs: Implications for cranial strength and feeding mechanics

A new large-bodied theropod dinosaur from the Middle Jurassic of Warwickshire, United Kingdom

Large theropod dinosaur footprint associations in western Gondwana: Behavioural and palaeogeographic implications

A reassessment of Kelmayisaurus petrolicus, a large theropod dinosaur from the Early Cretaceous of China

Giant theropod dinosaurs from Asia and North America: skulls of Tarbosaurus bataar and Tyrannosaurus rex compared

Gigantic footprint of a theropod dinosaur in the Early Jurassic of Poland

Crouching theropod and Navahopus sauropodomorph tracks from the Early Jurassic Navajo Sandstone of USA