scholarly journals Colobops : a juvenile rhynchocephalian reptile (Lepidosauromorpha), not a diminutive archosauromorph with an unusually strong bite

2020 ◽  
Vol 7 (3) ◽  
pp. 192179 ◽  
Author(s):  
Torsten M. Scheyer ◽  
Stephan N. F. Spiekman ◽  
Hans-Dieter Sues ◽  
Martín D. Ezcurra ◽  
Richard J. Butler ◽  
...  
Keyword(s):  
Late Triassic ◽  
Temporal Region ◽  
Post Mortem ◽  
Feeding Apparatus ◽  
Distributed Groups ◽  
Scan Data ◽  
Globally Distributed

Correctly identifying taxa at the root of major clades or the oldest clade-representatives is critical for meaningful interpretations of evolution. A small, partially crushed skull from the Late Triassic (Norian) of Connecticut, USA, originally described as an indeterminate rhynchocephalian saurian, was recently named Colobops noviportensis and reinterpreted as sister to all remaining Rhynchosauria, one of the earliest and globally distributed groups of herbivorous reptiles. It was also interpreted as having an exceptionally reinforced snout and powerful bite based on an especially large supratemporal fenestra. Here, after a re-analysis of the original scan data, we show that the skull was strongly dorsoventrally compressed post-mortem, with most bones out of life position. The cranial anatomy is consistent with that of other rhynchocephalian lepidosauromorphs, not rhynchosaurs. The ‘reinforced snout' region and the ‘exceptionally enlarged temporal region’ are preservational artefacts and not exceptional among clevosaurid rhynchocephalians. Colobops is thus not a key taxon for understanding diapsid feeding apparatus evolution.

scholarly journals Architecture and functional morphology of the skeletal apparatus of ozarkodinid conodonts

1997 ◽  
Vol 352 (1361) ◽  
pp. 1545-1564 ◽  
Author(s):  
Mark A. Purnell ◽  
Philip C. J. Donoghue
Keyword(s):  
Functional Morphology ◽  
Food Item ◽  
Anterior Part ◽  
The Body ◽  
Scale Model ◽  
Post Mortem ◽  
Feeding Apparatus ◽  
Food Acquisition ◽  
Anterior Edge

Ozarkodinid conodonts were one of the most successful groups of agnathan vertebrates. Only the oropharyngeal feeding apparatus of conodonts was mineralized, and the skeletal elements were generally disarticulated on the death and decay of the body. Occasionally, however, they were preserved in association as ‘natural assemblages’, fossilized in situ after post–mortem collapse of the apparatus. From analysis of element arrangement in natural assemblages of Idiognathodus from the Pennsylvanian of Illinois we have produced a precise scale model of the feeding apparatus of ozarkodinid conodonts. At the front lay an axial Sa element, flanked by two groups of four close-set elongate Sb and Sc elements which were inclined obliquely inwards and forwards; above these elements lay a pair of arched and inward pointing M elements. Behind the S-M array lay transversely oriented and bilaterally opposed Pb and Pa elements. Our model sheds new light on food acquisition in conodonts. We propose that the anterior S and M elements of ozarkodinid conodonts were attached to cartilaginous plates. In order for the animal to feed, these plates were first everted, and then drawn back and upward over the anterior edge of an underlying cartilage. These movements produced a highly effective grasping action, the cusps and denticles of the elements converging to grab and impale any food item that lay anterior to the open array. According to this hypothesis, the anterior part of the conodont apparatus is comparable to, and possibly homologous with, the lingual apparatus of extant agnathans; the elements themselves, however, have no direct homologues.

Proton Magnetic Resonance Spectroscopy (1H MRS) of the Hippocampal Formation in Schizophrenia: A Pilot Study

1994 ◽  
Vol 165 (4) ◽  
pp. 481-485 ◽  
Author(s):  
Henry A. Nasrallah ◽  
Thomas E. Skinner ◽  
Petra Schmalbrock ◽  
Pierre-Marle Robitaille
Keyword(s):  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Proton Magnetic Resonance ◽  
Proton Magnetic Resonance Spectroscopy ◽  
Hippocampal Formation ◽  
Resonance Spectroscopy ◽  
Temporal Region ◽  
Post Mortem ◽  
Temporal Structures ◽  
The Right

BackgroundRecent post-mortem and magnetic resonance imaging (MRI) studies strongly suggest a decrease in the volume of the hippocampus and other limbic temporal structures in schizophrenia. Therefore, we hypothesised that N-acetyl aspartate (NAA) which is found mainly in neurons and which can be measured by proton magnetic resonance spectroscopy (1H MRS) would be decreased in the limbic temporal region in schizophrenia.MethodConsenting subjects fulfilling DSM-III-R criteria for schizophrenia (n = 11) and matched healthy volunteers (n = 11) who were recruited in a tertiary university referral centre, participated in a 1H MRS brain study. Proton MRS spectra were obtained from a 12 cm3 voxel (2 × 2 × 3 cm) in the right and left hippocampus/amygdala region. A researcher blind to the source of the spectra, measured the NAA intensity in all subjects, which were then statistically compared across the two groups.ResultsNAA intensities were significantly reduced in the right hippocampus/amygdala region of schizophrenic patients (P = 0.038). The difference of the left side did not reach significance at the 95% confidence level.ConclusionsThe findings of decreased NAA in this study suggest that there may be a decrement in neuronal number or tissue volume of the right hippocampal/amygdala region in schizophrenia. Biochemical alterations in the metabolism of NAA in schizophrenia may be an alternative explanation. The findings are consistent with other types of post-mortem and in vivo evidence for hypoplasia of the limbic temporal structures in schizophrenia, postulated to be of neurodevelopmental pathogenesis.

scholarly journals The rise of the ruling reptiles and ecosystem recovery from the Permo-Triassic mass extinction

2018 ◽  
Vol 285 (1880) ◽  
pp. 20180361 ◽  
Author(s):  
Martín D. Ezcurra ◽  
Richard J. Butler
Keyword(s):  
Mass Extinction ◽  
Evolutionary Rates ◽  
Middle Permian ◽  
Late Triassic ◽  
Ecosystem Recovery ◽  
Terrestrial Vertebrates ◽  
Earth History ◽  
Biodiversity Change ◽  
Globally Distributed ◽  
Early Late

One of the key faunal transitions in Earth history occurred after the Permo-Triassic mass extinction ( ca 252.2 Ma), when the previously obscure archosauromorphs (which include crocodylians, dinosaurs and birds) become the dominant terrestrial vertebrates. Here, we place all known middle Permian–early Late Triassic archosauromorph species into an explicit phylogenetic context, and quantify biodiversity change through this interval. Our results indicate the following sequence of diversification: a morphologically conservative and globally distributed post-extinction ‘disaster fauna’; a major but cryptic and poorly sampled phylogenetic diversification with significantly elevated evolutionary rates; and a marked increase in species counts, abundance, and disparity contemporaneous with global ecosystem stabilization some 5 million years after the extinction. This multiphase event transformed global ecosystems, with far-reaching consequences for Mesozoic and modern faunas.

scholarly journals Environmental and diagenetic controls on the morphology and calcification of the Ediacaran metazoan Cloudina

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Amy Shore ◽  
Rachel Wood
Keyword(s):  
Mechanical Strength ◽  
Tube Wall ◽  
High Energy ◽  
Early Diagenesis ◽  
Low Energy ◽  
Post Mortem ◽  
Relative Thickness ◽  
Controlled Morphology ◽  
Globally Distributed

AbstractCloudina is a globally distributed Ediacaran metazoan, with a tubular, funnel-in-funnel form built of thin laminae (ca. 1–10 μm). To what degree local environmental controlled morphology, and whether early diagenesis controlled the degree of calcification of Cloudina, is debated. Here we test these hypotheses by considering assemblages from four, coeval localities from the Upper Omkyk Member, Nama Group, Namibia, from inner ramp to mid-ramp reef across the Zaris Subbasin. We show that sinuosity of the Cloudina tube is variable between sites, as is the relative thickness of the tube wall, suggesting these features were environmentally controlled. Walls are thickest in high-energy reef settings, and thinnest in the low-energy, inner ramp. While local diagenesis controls preservation, all diagenetic expressions are consistent with the presence of weakly calcified, organic-rich laminae, and lamina thicknesses are broadly constant. Finally, internal ‘cements’ within Cloudina are found in all sites, and pre-date skeletal breakage, transport, as well as syn-sedimentary botryoidal cement precipitation. Best preservation shows these to be formed by fine, pseudomorphed aragonitic acicular crystals. Sr concentrations and Mg/Ca show no statistically significant differences between internal Cloudina cements and botryoidal cements, but we infer all internal cements to have precipitated when Cloudina was still in-situ and added considerable mechanical strength, but may have formed post-mortem or in abandoned parts of the skeleton.

The osteology and relationships of Clevosaurus (Reptilia: Sphenodontida)

1988 ◽  
Vol 321 (1204) ◽  
pp. 125-178 ◽  
Keyword(s):  
Sister Group ◽  
Late Triassic ◽  
Temporal Region ◽  
Variable Degree ◽  
Partial Reduction ◽  
Median Ridge ◽  
South West ◽  
Fourth Species

The sphenodontid genus Clevosaurus from the late Triassic of south west Britain is represented by at least two different species. Exceptionally abundant remains of Clevosaurus occur as part of a diverse assemblage of microvertebrates lodged within fissure deposits at localities in Glamorgan and Avon. Although the majority of specimens occur as beautifully preserved disassociated elements, certain associated and articulated remains have been recovered. Contemporaneous vertebrates include other sphenodontians, archosaurs and procolophonids. C. hudsoni is fully restored as a lizard-like reptile approximately 25 cm long. It was essentially insectivorous, although it may have also been facultatively herbivorous, breaking down food with a well-developed precision shear bite. A smaller species, C. minor , is less widespread and its remains are generally not as well preserved. It seems probable that a third species might be distinguished on the basis of dental characteristics, and the occurrence of a fourth species cannot be discounted. A distinct suite of apomorphic characters separates the Sphenodontida from other lepidosauromorphs and these apomorphies are readily identifiable in Clevosaurus . In certain late Triassic sphenodontians the lower temporal arcade was apparently incomplete, but, contrary to Robinson’s ( J. geol. Soc. Lond . 129, 457 (1973)) description, the lower temporal arcade was unbroken in Clevosaurus . However, the articulation between the jugal, squamosal and quadratojugal does not conform to the configuration exhibited by all other sphenodontians in which both temporal arcades are complete. In addition, the possession of a supratemporal in Clevosaurus is unique among known sphenodontians. The parietal table in Clevosaurus is intermediate between the broad, flat plesiomorphic condition, seen in forms such as Polysphenodon and Homoeosaurus , and the derived narrow median ridge displayed by Kallimodon and Sphenodon . Consequently, within the Sphenodontida the position of Clevosaurus is unclear; however, on the basis of the prominently flanged additional teeth, some reduction in tooth numbers and at least some partial reduction in the width of the parietal table, it would appear to share certain characteristics with Sapheosaurus and Kallimodon. Palaeopleurosaurus , described by Carroll (1985) as a primitive pleurosaur, may also have affinities with this grouping. Some of the earliest sphenodontians, such as Planocephalosaurus and Diphydontosaurus , exhibit fusion of the median skull roofing elements, a short temporal region and retention of a variable degree of pleurodonty in the marginal dentition. Together with Gephyrosaurus these genera may constitute a monophyletic assemblage forming the sister group of all other sphenodontians.

The role of Central Asia in dinosaurian biogeography

1993 ◽  
Vol 30 (10) ◽  
pp. 2002-2012 ◽  
Author(s):  
Dale A. Russell
Keyword(s):  
North America ◽  
Central Asia ◽  
Early Cretaceous ◽  
Late Cretaceous ◽  
Middle Jurassic ◽  
Late Jurassic ◽  
Late Triassic ◽  
Globally Distributed ◽  
Northern And Southern Hemispheres

Dinosaurian biogeography may have been largely controlled by the Mesozoic fragmentation of Pangea and the reassembly of its fragments into a new, boreal supercontinent (Laurasia). Although Late Triassic and Early Jurassic dinosaurs were globally distributed, Chinese assemblages were dominated by endemic forms from Middle Jurassic into Early Cretaceous time. The affinities of Aptian – Albian immigrants to Asia were strongest with North America and Europe rather than Gondwana, indicating that the northern and southern hemispheres had by then attained their biogeographic identity. This distinctiveness was maintained through Cretaceous time. Europe seems to have been a buffer area between Paleolaurasia and Gondwana; of the northern continents it was the most strongly influenced by Gondwana dispersants. Late Jurassic dinosaur assemblages in North America exhibited Gondwana affinities, but by Late Cretaceous time they were dominated by forms of Asian ancestry.

Malerisaurus , a new eosuchian reptile from the late Triassic of India

1980 ◽  
Vol 291 (1048) ◽  
pp. 163-200 ◽  
Keyword(s):  
Flood Plain ◽  
Late Triassic ◽  
Temporal Region ◽  
Skeletal Morphology ◽  
The Family ◽  
Gastric Contents ◽  
Gondwana Supergroup

Two almost complete skeletons of a new eosuchian reptile, Malerisaurus robinsonae n.sp., were discovered as the presumable gastric contents of ‘twin’ skeletons of Parasuchus hislopi . The specimens are from fluvial flood plain deposits of the late Triassic Maleri Formation of the Gondwana supergroup, India. The osteology of Malerisaurus is described in detail. Malerisaurus was a small, gracile, long-necked eosuchian, facultatively bipedal, and probably able to climb trees or to take to the water when alarmed. It is comparable to modern bipedal lizards in size, proportions and inferred activities. The skull, although showing some carnivorous adaptation, is relatively unspecialized and indicates an insectivorous diet. Because Malerisaurus shows such a combination of primitive and advanced features as a diapsid skull, unossified laterosphenoid, lack of antorbital and mandibular fenestrae, slender limbs, primitive girdles, distinctive elongated cervicals and lack of dermal armour, it is assigned to the suborder Prolacertiformes of the order Eosuchia. A classification of Prolacertiformes indicates four families within this suborder: Petrolacosauridae, Protorosauridae, Prolacertidae and Tanystropheidae. Malerisaurus is tentatively allied to Protorosaurus in the family Protorosauridae; in neither genus is the temporal region of the skull adequately known. Malerisaurus furnishes detailed information about the skeletal morphology of what may be a hitherto undocumented lineage of eosuchian reptiles.

Technology and virtual teams: using globally distributed groups in MBA learning

1998 ◽  
Vol 15 (5) ◽  
pp. 174-182 ◽  
Author(s):  
Lori Rockett ◽  
Josep Valor ◽  
Paddy Miller ◽  
Peter Naude
Keyword(s):  
Virtual Teams ◽  
Distributed Groups ◽  
Globally Distributed

scholarly journals Braincase redescription of Efraasia minor Huene, 1908 (Dinosauria: Sauropodomorpha) from the Late Triassic of Germany, with comments on the evolution of the sauropodomorph braincase

2018 ◽  
Author(s):  
Mario Bronzati ◽  
Oliver W M Rauhut
Keyword(s):  
Ct Scan ◽  
Morphological Change ◽  
Morphological Variation ◽  
Soft Tissues ◽  
Jugular Vein ◽  
Foramen Magnum ◽  
Late Triassic ◽  
New Information ◽  
Phylogenetic Perspective ◽  
Scan Data

The braincase anatomy of the sauropodomorph dinosaur Efraasia minor (Late Triassic, Norian, Löwenstein Formation of Germany) is redescribed in detail, adding new information based on CT-Scan data. We discuss the evolution of sauropodomorph braincases from a phylogenetic perspective, focusing on non-neosauropodan representatives. For this, we revised braincase characters used in data matrices focused on these assemblage of taxa. This led to the recognition of problems with some of the phylogenetic characters, which did not accurately reflect the morphological variation observed among taxa within the group. We also discuss the presence of a divided metotic foramen in members of the group. This has implications for the recognition of soft tissues associated with braincase foramina in non-sauropodan sauropodomorphs, and we propose that the the path for the jugular vein was either through the posterior foramen resulting from this division or through the foramen magnum. Finally, our study demonstrates a series of differences regarding braincase anatomy between “prosauropods” and sauropod taxa. However, it remains unclear if these differences might be due to a drastic morphological change at the basis of the Sauropoda or if they simply reflect the lack of braincase materials of non-neosauropodan sauropods, which might exhibit transitional morphologies.

Recovery of lacustrine ecosystems after the end-Permian mass extinction

Geology ◽  
2020 ◽  
Vol 48 (6) ◽  
pp. 609-613 ◽  
Author(s):  
Xiangdong Zhao ◽  
Daran Zheng ◽  
Guwei Xie ◽  
Hugh C. Jenkyns ◽  
Chengguo Guan ◽  
...  
Keyword(s):  
Mass Extinction ◽  
Middle Triassic ◽  
Ordos Basin ◽  
Late Triassic ◽  
Fossil Assemblage ◽  
Ca 242 ◽  
The Ordos Basin ◽  
Permian Mass Extinction ◽  
Globally Distributed ◽  
Lacustrine Ecosystem

Abstract The end-Permian mass extinction (EPME; ca. 252 Ma) led to profound changes in lacustrine ecosystems. However, whether or not post-extinction recovery of lacustrine ecosystems was delayed has remained uncertain, due to the apparent rarity of Early and Middle Triassic deep perennial lakes. Here we report on mid–Middle Triassic lacustrine organic-rich shales with abundant fossils and tuff interlayers in the Ordos Basin of China, dated to ca. 242 Ma (around the Anisian-Ladinian boundary of the Middle Triassic). The organic-rich sediments record the earliest known appearance, after the mass extinction, of a deep perennial lake that developed at least 5 m.y. earlier than the globally distributed lacustrine shales and mudstones dated as Late Triassic. The fossil assemblage in the organic-rich sediments is diverse and includes plants, notostracans, ostracods, insects, fishes, and fish coprolites, and thus documents a Mesozoic-type, trophically multileveled lacustrine ecosystem. The results reveal the earliest known complex lacustrine ecosystem after the EPME and suggest that Triassic lacustrine ecosystems took at most 10 m.y. to recover fully, which is consistent with the termination of the “coal gap” that signifies substantial restoration of peat-forming forests.

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