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Tytuł:
Osteology of the unenlagiid theropod Neuquenraptor argentinus from the Late Cretaceous of Patagonia
Autorzy:
BRISSÓN EGLI, FEDERICO
ARANCIAGA ROLANDO, ALEXIS M.
AGNOLÍN, FEDERICO L.
NOVAS, FERNANDO E.
Powiązania:
https://bibliotekanauki.pl/articles/945635.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
dinosauria
theropoda
unenlagiidae
neuquenraptor
cretaceous
argentina
patagonia
Opis:
Neuquenraptor argentinus was described as the first undoubted deinonychosaurian theropod from Gondwana. The only known specimen is represented by a fragmentary skeleton, including a nearly complete foot, coming from Late Cretaceous beds of Neuquén Province, Patagonia, Argentina. Neuquenraptor was later considered as belonging to the Southern Hemisphere paravian clade Unenlagiidae, and proposed as a junior synonym of Unenlagia comahuensis. The aim of the present paper is to include a detailed anatomical description of Neuquenraptor (up to the date only known by a preliminary description). Comparisons with other paravians, especially unenlagiids, resulted in the finding of characters that may be considered as diagnostic of Unenlagiidae (e.g., scar-like fourth trochanter of femur, metatarsal II with tongue-shaped process over the caudal surface of metatarsal III, well-developed convex longitudinal plantar crest of metatarsal IV). Furthermore, comparisons between Neuquenraptor and Unenlagia are carried out with the aim to evaluate the possible synonymy between these taxa. These comparisons indicate that at least two similar-sized unenlagiids were present on the Portezuelo Formation. However, in concordance with previous authors, we are not able to support nor dismiss the possible synonymy between Unenlagia and Neuquenraptor. Additional findings of unenlagiid fossils from the Portezulo Formation will help to clarify the taxonomic status of these taxa.
Źródło:
Acta Palaeontologica Polonica; 2017, 62, 3; 549-562
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Why tyrannosaurid forelimbs were so short: An integrative hypothesis
Autorzy:
Padian, Kevin
Powiązania:
https://bibliotekanauki.pl/articles/2216272.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Dinosauria
Theropoda
Tyrannosaurus
Abelisaurus
Carcharodontosaurus
predation
limb proportions
Opis:
The unusually shortened limbs of giant theropods, including abelisaurids, carcharodontosaurids, and derived tyrannosauroids such as Tyrannosaurus rex have long been an object of wonder, speculation, and even derision on the part of both paleontologists and the public. Two questions commonly asked are “Why did the forelimbs become so short?” and “What did the animals use such short forelimbs for, if for anything?” Because basal tyrannosauroids and their outgroups, as well as the outgroups of other giant theropods, had longer forelimbs, the foreshortening of these elements in derived taxa was secondary, and it ostensibly involved a shift in developmental timing of the forelimb elements. Factors proposed to have influenced the evolutionary foreshortening include natural selection, sexual selection, energetic compensation, ontogenetic vagaries, and rudimentation due to disuse. Hypotheses of use have varied from a supporting anchor that allows the hindlimbs a purchase to stand from a reclining position to a pectoral version of pelvic claspers during intercourse to a sort of waving display during sexual or social selection. None of these hypotheses explain selective regimes for reduction; at best, they might argue for maintenance of the limb, but in all cases a larger limb would have suited the function better. It is likely that we have been looking the wrong way through the telescope, and that no specific function of the forelimbs was being selected; instead, another crucial adaptation of the animal profited from forelimb reduction. Here I propose, in the context of phylogenetic, ontogenetic, taphonomic, and social lines of evidence, that the forelimbs became shorter in the context of behavioral ecology: the great skull and jaws provided all the necessary predatory mechanisms, and during group-feeding on carcasses, limb reduction was selected to keep the forelimbs out of the way of the jaws of large conspecific predators, avoiding injury, loss of blood, amputation, infection, and death. A variety of lines of evidence can test this hypothesis.
Źródło:
Acta Palaeontologica Polonica; 2022, 67, 1; 63-76
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Oviraptorosaur tail forms and functions
Autorzy:
Persons,IV, W.S.
Currie, P.J.
Norell, M.A.
Powiązania:
https://bibliotekanauki.pl/articles/945893.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Dinosauria
paleozoology
Theropoda
Oviraptorosauria
oviraptorosaur
pygostyle
caudal musculature
functional morphology
Opis:
Oviraptorosaur caudal osteology is unique among theropods and is characterized by posteriorly persistent and exceptionally wide transverse processes, anteroposteriorly short centra, and a high degree of flexibility across the pre-pygostyle vertebral series. Three-dimensional digital muscle reconstructions reveal that, while oviraptorosaur tails were reduced in length relative to the tails of other theropods, they were muscularly robust. Despite overall caudal length reduction, the relative size of the M. caudofemoralis in most oviraptorosaurs was comparable with those of other non-avian theropods. The discovery of a second Nomingia specimen with a pygostyle confirms that the fused terminal vertebrae of the type specimen were not an abnormality. New evidence shows that pygostyles were also present in the oviraptorosaurs Citipati and Conchoraptor. Based on the observed osteological morphology and inferred muscle morphology, along with the recognition that many members of the group probably sported broad tail-feather fans, it is postulated that oviraptorosaur tails were uniquely adapted to serve as dynamic intraspecific display structures. Similarities, including a reduced vertebral series and a terminal pygostyle, between the tails of oviraptorosaurs and the tails of theropods widely accepted as basal members of the Avialae, appear to be convergences.
Źródło:
Acta Palaeontologica Polonica; 2014, 59, 3; 553-567
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new approach to evaluate the cursorial ability of the giant theropod Giganotosaurus carolinii
Autorzy:
Blanco, R E
Mazzetta, G V
Powiązania:
https://bibliotekanauki.pl/articles/21508.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Cretaceous
Theropoda
Dinosauria
theropod
dinosaur
Giganotosaurus
South America
Giganotosaurus carolinii
Opis:
The cursorial capability of the South American giant theropod Giganotosaurus carolinii should have been quite limited taking into account the strength indicator of its femur (approximately 7 GPa⁻¹) as well as the risk of experiencing grave or even lethal injuries involved in the falling of this multitonne animal on a run. However, even at low speeds a fall would have caused serious injuries. Thus, in accordance to the approach developed in this study, the maximum speed of Giganotosaurus should be not that which will implicate corporal lesions with minimum probability of lethalness. Instead, its maximum speed should be that which would permit the recovery of body equilibrium as each step is taken. Taking into consideration this approach, an indicator of stability is defined for bipedal, cursorial animals. This indicator is determined by the relationship between the time available for the movement of hip joint during the retraction of a hindlimb and the time needed to move the opposite hindlimb by an angle (in function of the speed) of sufficient magnitude as to facilitate the recovery of body equilibrium. This indicator was used to estimate the maximum speed of locomotion of Giganotosaurus (about 14 m s⁻¹) at which, from a kinematic point of view, the danger of falling does not exist.
Źródło:
Acta Palaeontologica Polonica; 2001, 46, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Scapular orientation in theropods and basal birds, and the origin of flapping flight
Autorzy:
Senter, P
Powiązania:
https://bibliotekanauki.pl/articles/21712.pdf
Data publikacji:
2006
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
bird
Archaeopteryx
Aves
flight
Theropoda
flapping flight
theropod
basal bird
paleontology
Opis:
Basal birds such as Archaeopteryx and Confuciusornis are typically portrayed as flapping fliers. However, here I show that shoulder joint orientation in these animals prevented elevation of the humerus above the dorsum, thereby preventing use of the recovery stroke, an important part of flapping flight. In members of the clade Ornithothoraces, which includes extant birds and the extinct avian clade Enantiornithes, the shoulder joint is reoriented to permit elevation of the humerus above the dorsum, permitting flapping flight. Although basal birds may have glided, flapping flight began significantly later in avian evolution than has been thought.
Źródło:
Acta Palaeontologica Polonica; 2006, 51, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Macroevolutionary and morphofunctional patterns in theropod skulls: A morphometric approach
Autorzy:
Foth, C.
Rauhut, O.W.M.
Powiązania:
https://bibliotekanauki.pl/articles/21033.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
macroevolution
theropod dinosaur
skull
Theropoda
feeding ecology
biomechanics
evolution
Mesozoic
paleontology
Opis:
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.
Źródło:
Acta Palaeontologica Polonica; 2013, 58, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Caudipteryx as a non-avalian theropod rather than a flightless bird
Autorzy:
Dyke, G J
Norell, M.A.
Powiązania:
https://bibliotekanauki.pl/articles/22434.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
bird
Avialae
feather
Cretaceous
Caudipteryx zoui
China
Theropoda
Dinosauria
Yixian Formation
paleontology
Opis:
Caudipteryx zoui is a small enigmatic theropod known from the Early Cretaceous Yixian Formation of the People’s Republic of China. From the time of its initial description, this taxon has stimulated a great deal of ongoing debate regarding the phylogenetic relationship between non−avialan theropods and birds (Avialae) because it preserves structures that have been uncontroversially accepted as feathers (albeit aerodynamically unsuitable for flight). However, it has also been proposed that both the relative proportions of the hind limb bones (when compared with overall leg length), and the position of the center of mass in Caudipteryx are more similar to those seen in extant cusorial birds than they are to other non−avialan theropod dinosaurs. This conclusion has been used to imply that Caudipteryx may not have been correctly interpreted as a feathered non−avialan theropod, but instead that this taxon represents some kind of flightless bird. We review the evidence for this claim at the level of both the included fossil specimen data, and in terms of the validity of the results presented. There is no reason—phylogenetic, morphometric or otherwise—to conclude that Caudipteryx is anything other than a small non−avialan theropod dinosaur.
Źródło:
Acta Palaeontologica Polonica; 2005, 50, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Avialan status for Oviraptorosauria
Autorzy:
Maryanska, T
Osmolska, H.
Wolsan, M.
Powiązania:
https://bibliotekanauki.pl/articles/23106.pdf
Data publikacji:
2002
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
bird
Avialae
phylogenetic analysis
Cretaceous
phylogenetic nomenclature
Theropoda
Dinosauria
dinosaur
Oviraptorosauria
paleontology
Opis:
Oviraptorosauria is a clade of Cretaceous theropod dinosaurs of uncertain affinities within Maniraptoriformes. All previous phylogenetic analyses placed oviraptorosaurs outside a close relationship to birds (Avialae), recognizing Dromaeosauridae or Troodontidae, or a clade containing these two taxa (Deinonychosauria), as sister taxon to birds. Here we present the results of a phylogenetic analysis using 195 characters scored for four outgroup and 13 maniraptoriform (ingroup) terminal taxa, including new data on oviraptorids. This analysis places Oviraptorosauria within Avialae, in a sister−group relationship with Confuciusornis. Archaeopteryx, Therizinosauria, Dromaeosauridae, and Ornithomimosauria are successively more distant outgroups to the Confuciusornis−oviraptorosaur clade. Avimimus and Caudipteryx are successively more closely related to Oviraptoroidea, which contains the sister taxa Caenagnathidae and Oviraptoridae. Within Oviraptoridae, “Oviraptor” mongoliensis and Oviraptor philoceratops are successively more closely related to the Conchoraptor−Ingenia clade. Oviraptorosaurs are hypothesized to be secondarily flightless. Emended phylogenetic definitions are provided for Oviraptoridae, Caenagnathidae, Oviraptoroidea, Oviraptorosauria, Avialae, Eumaniraptora, Maniraptora, and Maniraptoriformes.
Źródło:
Acta Palaeontologica Polonica; 2002, 47, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Velociraptorine dromaeosaurid teeth from the Kimmeridgian [Late Jurassic] of Germany
Autorzy:
van der Lubbe, T
Richter, U.
Knotschke, N.
Powiązania:
https://bibliotekanauki.pl/articles/21506.pdf
Data publikacji:
2009
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
velociraptorine dromaeosaurid
tooth
Kimmeridgian
Late Jurassic
Jurassic
Germany
Saurischia
Theropoda
Dromaeosauridae
dromaeosaurid
paleontology
Opis:
Six theropod teeth from a Late Jurassic (Kimmeridgian) bone bed in Langenberg Quarry of Oker (Goslar, Germany) are identified as a new dromaeosaurid taxon, here left in open nomenclature. Direct comparison reveals that the teeth are very similar to velociraptorine dromaeosaurid teeth from the Guimarota coal mine (Late Jurassic, Portugal) and to velociraptorine dromaeosaurid teeth from Uña (Barremian, Cuenca Province, Spain). Our data indicate that the teeth from the Kimmeridgian of Lower Saxony are of velociraptorine dromaeosaurid type, and therefore represent one of the oldest occurrences of the group Dromaeosauridae.
Źródło:
Acta Palaeontologica Polonica; 2009, 54, 3; 401-408
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An articulated pes from a small parvicursorine alvarezsauroid dinosaur from Inner Mongolia, China
Autorzy:
Hone, D.W.E.
Choiniere, J.N.
Tan, Q.
Xu, X.
Powiązania:
https://bibliotekanauki.pl/articles/21549.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
paleontology
Dinosauria
Theropoda
maniraptoran
arctometatarsalian organism
Cretaceous
Inner Mongolia
alvarezsauroid dinosaur
dinosaur
China
Opis:
A near complete and articulated parvicursorine pes from the Campanian Wulansuhai Formation is described. This pes is referred to the genus Linhenykus and is one of the first foot skeletons to be described for a derived alvarezsaur, providing new information on the first digit of the pes. The evolution of a laterally directed flange of the anterior face of the distal third metatarsal in arctometatarsalian taxa is described and discussed. This flange may have increased stability of the foot during cursorial locomotion and may also provide useful taxonomic and systematic data.
Źródło:
Acta Palaeontologica Polonica; 2013, 58, 3
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new ornithomimid dinosaur with gregarious habits from the Late Cretaceous of China
Autorzy:
Kobayashi, Y
Lu, J.C.
Powiązania:
https://bibliotekanauki.pl/articles/20983.pdf
Data publikacji:
2003
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Cretaceous
Late Cretaceous
Theropoda
Dinosauria
China
Ornithomimosauria
gragarious habit
dinosaur
Ornithomimidae
paleontology
ornithomimid dinosaur
Opis:
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.
Źródło:
Acta Palaeontologica Polonica; 2003, 48, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Skull structure and evolution in tyrannosaurid dinosaurs
Autorzy:
Currie, P J
Hurum, J.H.
Sabath, K.
Powiązania:
https://bibliotekanauki.pl/articles/22810.pdf
Data publikacji:
2003
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
parsimonious analysis
phylogenesis
Coelurosauria
Tyrannosauridae
Theropoda
Dinosauria
skull structure
evolution
dinosaur
paleontology
tyrannosaurid dinosaur
Opis:
Tyrannosauridae can be subdivided into two distinct subfamilies—the Albertosaurinae and the Tyrannosaurinae. Previously recognized subdivisions Aublysodontinae and Shanshanosaurinae are rejected because they are based on insufficient material and juvenile specimens. Our results are based upon a phylogenetic analysis using PAUP program (Swofford 1999) of 77 skull characters and seven genera (Albertosaurus, Alioramus, Daspletosaurus, Gorgosaurus, Nanotyrannus, Tarbosaurus, and Tyrannosaurus); with Allosaurus as outgroup. Of the 77 characters used, more than half were parsimony informative. Asingle most parsimonious tree was obtained with the Tree Length being 88. The analysis of cranial characters and comparison of postcranial features reveal that Tarbosaurus bataar is not the sister taxon of Tyrannosaurus rex (contra Holtz 2001). Their similarities are partially due to the fact that both are extremely large animals. Thus, Tarbosaurus should be considered a genus distinct from Tyrannosaurus.
Źródło:
Acta Palaeontologica Polonica; 2003, 48, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
New information on scavenging and selective feeding behaviour of tyrannosaurids
Autorzy:
Hone, D.W.E.
Watabe, M.
Powiązania:
https://bibliotekanauki.pl/articles/20999.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
paleontology
new information
scavenging
feeding behaviour
tyrannosaurid
Dinosauria
Theropoda
Tarbosaurus
paleoecology
carnivore
predation
fossil record
Opis:
Feeding traces for carnivorous theropod dinosaurs are typically rare but can provide important evidence of prey choice and mode of feeding. Here we report a humerus of the hadrosaurine Saurolophus which was heavily damaged from feeding attributed to the giant tyrannosaurine Tarbosaurus. The bone shows multiple bites made in three distinctive styles termed “punctures”, “drag marks” and “bite−and−drag marks”. The distribution of these bites suggest that the animal was actively selecting which biting style to use based on which part of the bone was being engaged. The lack of damage to the rest of the otherwise complete and articulated hadrosaur strongly implies that this was a scavenging event, the first reported for a tyrannosaurid, and not feeding at a kill site.
Źródło:
Acta Palaeontologica Polonica; 2010, 55, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An unusual theropod dinosaur from the Late Cretaceous Nemegt Formation of Mongolia
Autorzy:
Osmolska, H
Powiązania:
https://bibliotekanauki.pl/articles/22126.pdf
Data publikacji:
1996
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Theropoda
Mongolia
gady kopalne
skamienialosci
kosci
Bagaraatan ostromi
dinozaury
paleontologia
paleozoologia
Kotlina Nemegt
anatomia zwierzat
Opis:
An incomplete skeleton of a theropod dinosaur, Bagaraatan ostromi gen, et sp. n., was found in the Nemegt Fm. at Nemegt, Mongolia. The mandible in B. ostromi has a shallow but massive dentary, relatively deep postdentary portion with two surangular foramina and somewhat elongated retroarticular process; on the lateral surface of the postacetabular process of the ilium there are two large depressions for muscle origins separated by a crestlike projection; the fibula is fused distally with the tibiotarsus and the coalesced astragalocalcaneum. Bagaraatan represents the Tetanurae and displays some synapomorphies with the Avetheropoda, however, incompleteness of the skeleton of B. ostromi does not allow to determine its more precise affiliation. Bagaraatan was about 3.0-3.5 m long, had a relatively small head and slender hind limbs. The presence of strongly developed hyposphenes in a long series of anterior caudals rendered its tail only slighily flexible proximally.
W pracy opisano nowego mięsożernego dinozaura Bagaraatan ostromi gen. et sp. n. (Theropoda). Okaz obejmujący żuchwę, serię 25 kręgów ogonowych, fragmenty kości miednicy oraz kończyny tylnej, został znaleziony w osadach formacji Nemegt (?środkowy mastrycht) Kotliny Nemegt (Pustynia Gobi, Mongolia) przez Polsko-Mongolską Ekspedycję Paleontologiczną, w l970 roku. Zachowane szczątki świadczą, że B. ostromi był teropodem ok. 3.0-3.5 m długim, o smukłych kończynach tylnych i usztywnionym ogonie. Długość żuchwy wskazuje, że czaszka była stosunkowo niewielka. Żuchwa jest masywna i zaopatrzona była w silne zęby, z których zachowały się tylko korzenie i podstawy koron. Jej część tylna jest dość wysoka i przypomina żuchwy teropodów zaliczanych do polifiletycznej grupy „Carnosauria”, różni się jednak od nich bardziej wydłużonym wyrostkiem pozastawowym i dwoma, zamiast jednego, otworami w kości nadkątowej. W odróżnieniu od większości znanych teropodów, u których najwyżej tylko kilka przednich kręgów ogonowych wykazuje obecność dodatkowych wyrostków (hyposfenów) wzmacniających połączenia międzykręgowe, u B. ostromi wyrostki te występują między kilkunastoma proksymalnymi kręgami ogonowymi, co ograniczało ruchomość ogona także w tym odcinku. Kość biodrowa B. ostromi wyróżnia się obecnością dwóch zagłębień na bocznej stronie wyrostka zapanewkowego, zapewne dla przyczepu bardzo silnego mięśnia biodrowo-udowego. Takie zagłębienia nie są znane u żadnych innych dinozaurów. W budowie podudzia zwraca uwagę częściowy zrost kości piszczelowej i strzałkowej ze sobą oraz z proksymalnym rzędem kości stępu. Zrost tych kości spotykany jest tylko w jednej, prymitywnej grupie teropodów, Ceratosauria, od której jednak B. ostromi różni się szeregiem zaawansowanych cech. Fragmentaryczność materiału, a zwłaszcza brak czaszki i kończyn przednich, sprawiają trudność w zaliczeniu Bagaraatan do jednej ze znanych jednostek taksonomicznych w obrębie Theropoda. Jednak pewne cechy diagnostyczne wskazują, że rodzaj ten jest przedstawicielem Tetanurae Gauthier 1986 i jest najbliżej spokrewniony z Avetheropoda Paul 1988, aczkolwiek jest od nich prymitywniejszy.
Źródło:
Acta Palaeontologica Polonica; 1996, 41, 1; 1-38
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The endocranium of the theropod dinosaur Ceratosaurus studied with computer tomography
Autorzy:
Sanders, R K
Smith, D.K.
Powiązania:
https://bibliotekanauki.pl/articles/22430.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
cranial pneumatic system
Ceratosaurus
virtual rendering
paleoneurology
Theropoda
theropod dinosaur
computer tomography
dinosaur
endocranium
paleontology
Opis:
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.
Źródło:
Acta Palaeontologica Polonica; 2005, 50, 3
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
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