scholarly journals Anomalously high variation in postnatal development is ancestral for dinosaurs but lost in birds

2016 ◽  
Vol 113 (51) ◽  
pp. 14757-14762 ◽  
Author(s):  
Christopher T. Griffin ◽  
Sterling J. Nesbitt
Keyword(s):  
Postnatal Development ◽  
Intraspecific Variation ◽  
Early Jurassic ◽  
Late Triassic ◽  
Growth Trajectories ◽  
Low Levels ◽  
Triassic Period ◽  
Rates Of Growth

Compared with all other living reptiles, birds grow extremely fast and possess unusually low levels of intraspecific variation during postnatal development. It is now clear that birds inherited their high rates of growth from their dinosaurian ancestors, but the origin of the avian condition of low variation during development is poorly constrained. The most well-understood growth trajectories of later Mesozoic theropods (e.g.,Tyrannosaurus,Allosaurus) show similarly low variation to birds, contrasting with higher variation in extant crocodylians. Here, we show that deep within Dinosauria, among the earliest-diverging dinosaurs, anomalously high intraspecific variation is widespread but then is lost in more derived theropods. This style of development is ancestral for dinosaurs and their closest relatives, and, surprisingly, this level of variation is far higher than in living crocodylians. Among early dinosaurs, this variation is widespread across Pangaea in the Triassic and Early Jurassic, and among early-diverging theropods (ceratosaurs), this variation is maintained for 165 million years to the end of the Cretaceous. Because the Late Triassic environment across Pangaea was volatile and heterogeneous, this variation may have contributed to the rise of dinosaurian dominance through the end of the Triassic Period.

Chapter 18 Triassic history

1997 ◽  
Vol 17 (1) ◽  
pp. 340-362 ◽  
Author(s):  
W. Brian Harland ◽  
Isobel Geddes
Keyword(s):  
Middle Triassic ◽  
Early Jurassic ◽  
Late Triassic ◽  
Early Triassic ◽  
Marked Contrast ◽  
Angular Unconformity ◽  
Triassic Period ◽  
Age Determinations

The Triassic Period of about 40 million years dutation spanned about a third of that of the Carboniferous and Permian interval. The Triassic rocks of Svalbard are easily distinguished from the underlying Permian strata because of a distinct desconformity between them and a marked contrast in facies from the resistant. pale coloured, cherls and siliciclastics of the Kapp Starostin Formation to the softer, darker areno-argillaceous Vardebukta and equivalent formations. Figure 18.1 shows the distribution of Triassic strata in Svalbard.The minor angular unconformity represents a hiatus mainly in the Permian rather than the Triassic record. The dominantly argillaceous facies constitute the Early Triassic to Late Middle Triassic Sassendalen Group. The rocks can be well dated from ammonoids, typically within calcareous concretions in the shales.The succeding Kapp Toscana Group is distinguished by a dominatly sandy deltaic facies in which age determinations are difficult. It spans both Late Triassic and Early Jurassic spoehs (roughly mid-Ladinian to mid-Bathonian). The Triassic-Jurassic boundary is not easy to estimate. Nevertheless towards the end of Triassic time (e.g. Rhaetian) the overall scene changed. Thus of the three formations of the Kapp Toscana Group the lower two (Tschermakfjellet and De Geerdalen) belong to the Triassic story. The overlying Wilhelmøya Formation may possibly range from Latest Triassic through Liassic time, and due to its complexity it is also discussed in the Jurassic-Crataceous chapter (19).The facies of the two groups reflect two distinct environmental configurations. The Sassendalen Group was deposited on a distal marine muddy shelf with a

Provenance of Jurassic sedimentary rocks of south-central Quesnellia, British Columbia: implications for paleogeography

2004 ◽  
Vol 41 (1) ◽  
pp. 103-125 ◽  
Author(s):  
Nathan T Petersen ◽  
Paul L Smith ◽  
James K Mortensen ◽  
Robert A Creaser ◽  
Howard W Tipper
Keyword(s):  
Detrital Zircon ◽  
Middle Jurassic ◽  
Sedimentary Rocks ◽  
Source Area ◽  
Lower Jurassic ◽  
Early Jurassic ◽  
Late Triassic ◽  
Nd Isotopes ◽  
South Central ◽  
History Of

Jurassic sedimentary rocks of southern to central Quesnellia record the history of the Quesnellian magmatic arc and reflect increasing continental influence throughout the Jurassic history of the terrane. Standard petrographic point counts, geochemistry, Sm–Nd isotopes and detrital zircon geochronology, were employed to study provenance of rocks obtained from three areas of the terrane. Lower Jurassic sedimentary rocks, classified by inferred proximity to their source areas as proximal or proximal basin are derived from an arc source area. Sandstones of this age are immature. The rocks are geochemically and isotopically primitive. Detrital zircon populations, based on a limited number of analyses, have homogeneous Late Triassic or Early Jurassic ages, reflecting local derivation from Quesnellian arc sources. Middle Jurassic proximal and proximal basin sedimentary rocks show a trend toward more evolved mature sediments and evolved geochemical characteristics. The sandstones show a change to more mature grain components when compared with Lower Jurassic sedimentary rocks. There is a decrease in εNdT values of the sedimentary rocks and Proterozoic detrital zircon grains are present. This change is probably due to a combination of two factors: (1) pre-Middle Jurassic erosion of the Late Triassic – Early Jurassic arc of Quesnellia, making it a less dominant source, and (2) the increase in importance of the eastern parts of Quesnellia and the pericratonic terranes, such as Kootenay Terrane, both with characteristically more evolved isotopic values. Basin shale environments throughout the Jurassic show continental influence that is reflected in the evolved geochemistry and Sm–Nd isotopes of the sedimentary rocks. The data suggest southern Quesnellia received material from the North American continent throughout the Jurassic but that this continental influence was diluted by proximal arc sources in the rocks of proximal derivation. The presence of continent-derived material in the distal sedimentary rocks of this study suggests that southern Quesnellia is comparable to known pericratonic terranes.

scholarly journals New insights on the early Mesozoic evolution of multiple tectonic regimes in the northeastern North China Craton from the detrital zircon provenance of sedimentary strata

Solid Earth ◽  
2018 ◽  
Vol 9 (6) ◽  
pp. 1375-1397 ◽  
Author(s):  
Yi Ni Wang ◽  
Wen Liang Xu ◽  
Feng Wang ◽  
Xiao Bo Li
Keyword(s):  
North China Craton ◽  
North China ◽  
Early Jurassic ◽  
Orogenic Belt ◽  
Detrital Zircons ◽  
Late Triassic ◽  
Early Triassic ◽  
The South ◽  
The North ◽  
Early Mesozoic

Abstract. To investigate the timing of deposition and provenance of early Mesozoic strata in the northeastern North China Craton (NCC) and to understand the early Mesozoic paleotectonic evolution of the region, we combine stratigraphy, U–Pb zircon geochronology, and Hf isotopic analyses. Early Mesozoic strata include the Early Triassic Heisonggou, Late Triassic Changbai and Xiaoyingzi, and Early Jurassic Yihe formations. Detrital zircons in the Heisonggou Formation yield  ∼ 58 % Neoarchean to Paleoproterozoic ages and  ∼ 42 % Phanerozoic ages and were sourced from areas to the south and north of the basins within the NCC, respectively. This indicates that Early Triassic deposition was controlled primarily by the southward subduction of the Paleo-Asian oceanic plate beneath the NCC and collision between the NCC and the Yangtze Craton (YC). Approximately 88 % of the sediments within the Late Triassic Xiaoyingzi Formation were sourced from the NCC to the south, with the remaining  ∼ 12 % from the Xing'an–Mongolia Orogenic Belt (XMOB) to the north. This implies that Late Triassic deposition was related to the final closure of the Paleo-Asian Ocean during the Middle Triassic and the rapid exhumation of the Su–Lu Orogenic Belt between the NCC and YC. In contrast,  ∼ 88 % of sediments within the Early Jurassic Yihe Formation were sourced from the XMOB to the north, with the remaining  ∼ 12 % from the NCC to the south. We therefore infer that rapid uplift of the XMOB and the onset of the subduction of the Paleo-Pacific Plate beneath Eurasia occurred in the Early Jurassic.

Stratigraphic evolution of a Late Triassic to Early Jurassic intracontinental basin in southeastern South China: A consequence of flat-slab subduction?

2014 ◽  
Vol 302 ◽  
pp. 44-63 ◽  
Author(s):  
Chong-Jin Pang ◽  
Bryan Krapež ◽  
Zheng-Xiang Li ◽  
Yi-Gang Xu ◽  
Hai-Quan Liu ◽  
...  
Keyword(s):  
South China ◽  
Early Jurassic ◽  
Late Triassic ◽  
Flat Slab ◽  
Flat Slab Subduction ◽  
Stratigraphic Evolution
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