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Reply to the comment on Chu et al., “Lilliput effect in freshwater ostracods during the Permian-Triassic extinction” [Palaeogeography, Palaeoclimatology, Palaeoecology 435 (2015): 38-52]
The body size of marine ectotherms is often negatively correlated with ambient water temperature, as seen in many clades during the hyperthermal crisis of the end-Permian mass extinction (c. 252 Ma). However, in the case of ostracods, size changes during ancient hyperthermal events are rarely quantified. In this study, we evaluate the body size changes of ostracods in the Aras Valley section (northwest Iran) in response to the drastic warming during the end-Permian mass extinction at three taxonomic levels: class, order, species. At the assemblage level, the warming triggers a complete species turnover in the Aras Valley section, with larger, newly emerging species dominating the immediate post-extinction assemblage for a short time. Individual ostracod species and instars do not show dwarfing or a change in body size as an adaptation to the temperature stress during the end-Permian crisis. This may indicate that the ostracods in the Aras Valley section might have been exceptions to the temperature–size rule (TSR), using an adaptation mechanism that does not involve a decrease in body size. This adaptation might be similar to the accelerated development despite constant instar body sizes that can be observed in some recent experimental studies of ostracod responses to thermal stress.
In the Junggar Basin, northwestern China, the mass extinction-related strata at the base and top of the Triassic have been well studied, but the biostratigraphy and vegetation patterns of the Middle–Late Triassic sediments are comparatively poorly resolved. Here we investigate Middle–Late Triassic successions of the Dalongkou Section in the southern Junggar Basin for palynostratigraphy and vegetation patterns. Three palynological abundance zones are proposed here: the Aratrisporites Abundance Zone (Middle Triassic), the Dictyophyllidites - Aratrisporites Abundance Zone (latest Middle to early Late Triassic) and the Lycopodiacidites - Stereisporites informal abundance zone (Late Triassic). A review of previous records of the Fukangichthys Fauna indicates that this vertebrate fossil assemblage is stratigraphically located within the uppermost part of the Karamay Formation and is Middle Triassic in age. The revised dating of this and other faunas are further used to constrain the palynological zones in the Junggar Basin. Although the palynoflora is consistently dominated by non-striate bisaccate pollen (produced by seed ferns and/or conifers) in the studied section, spores record a distinctive abundance increase during the late Middle Triassic. Spore taxon abundance changes indicate a vegetational shift from a Middle Triassic-early Late Triassic community characterized by abundant lycophytes (likely Annalepis and Pleuromeia ) to a Late Triassic ecosystem with abundant dipteridaceous ferns (e.g. Dictyophyllum ) in the Junggar Basin and across North China. This study updates Triassic biostratigraphy in the Junggar Basin, and sheds light on temporal floral changes in this basin and elsewhere in North China during the Middle to Late Triassic.
Supplementary material at https://doi.org/10.6084/m9.figshare.c.6655485
The Carnian Pluvial Episode (CPE; ∼234‒232 million years ago) is characterized by an accelerated hydrological cycle, global warming and a period of elevated biotic turnover. Using spores and pollen, we reconstruct vegetation and climate changes through a Carnian‒Norian (Upper Triassic) interval of the Huangshanjie Formation from the Junggar Basin, China. Four palynofloras were identified, representing distinct vegetation communities. Among these palynofloras, we observed a prominent shift from a conifer-dominated climax forest community, with common ginkgophytes and bennettites, to a fern-dominated community, suggestive of an environmental perturbation. We interpret this change as a regional shift in vegetation, likely caused by increased humidity, consistent with the CPE. Our records represent the first indication of a possible CPE-induced vegetation response in the Junggar Basin and highlight how this event likely affected floral communities of inland Laurasia.
Supplementary material at https://doi.org/10.6084/m9.figshare.c.5738637
A reduction in body size (Lilliput effect) has been repeatedly proposed for many marine organisms in the aftermath of the Permian-Triassic (PT) mass extinction. Specifically-reduced maximum sizes of benthic marine invertebrates have been proposed for the entire Early Triassic. This concept was originally based on observations on Early Triassic gastropods from the western USA basin and the Dolomites (N Italy) and it stimulated subsequent studies on other taxonomic groups. However, only a few studies have tested the validity of the Lilliput effect in gastropods to determine whether the paucity of large-sized gastropods is a genuine signal or the result of a poor fossil record and insufficient sampling. In combination with a review of the literature, we document numerous new, abundant, large-sized gastropods from Griesbachian outcrops of Greenland and from the Smithian-early Spathian interval in the southwestern USA. We show that large-sized (“Gulliver”) gastropods (i) were present soon after the PT mass extinction, (ii) occurred in various basins, sedimentary facies and environmental contexts (from shallow to deeper settings), and (iii) belong to diverse higher-rank taxa. Focusing on the western USA basin, we investigate areas from which microgastropod shell-beds were previously presented as being typical. However, we show that Gulliver gastropods do occur in the very same areas. Insufficient sampling effort is probably the main reason for the rarity of reports of large Early Triassic gastropods, which is supported by preliminary rarefaction-based simulations. Finally, it appears that the recently documented middle to late Smithian climate shifts and the severe end-Smithian extinction of nekto-pelagic faunas did not reduce maximum shell sizes of gastropods.
For the first time the non-marine ostracod association of the Vjaznikovian Gorizont, late Tatarian, in the East European platform is described. The ostracod fauna consists of non-marine forms which are typical of the youngest horizons of the late Tatarian from the East European platform, as well as of some species which are known from the Permian and (?)Triassic beds of Siberia. Vjaznikovian ostracods occupy the highest position in the Permian, at the transition into the Triassic.
The ‘Lilliput Effect’ represents a pronounced reduction in the size of the biota associated with the aftermath of mass extinctions. Although there is empirical evidence that suggests that it may be a common pattern during the recoveries from various mass extinction events, it remains to be analyzed in more detail to understand how pervasive the trend is from temporal, spatial, and taxonomic perspectives. The ‘Lilliput Effect’ could represent dynamics associated with or important diversions from a variety of biologic ‘rules’, such as Cope's and Bergmann's, governing size changes. Furthermore, there are a variety of possible patterns that could produce the ‘Lilliput Effect’ including: 1) the survival of small taxa; 2) the dwarfing of larger lineages; and 3) the evolutionary miniaturization from larger ancestral stocks. Finally, an interdisciplinary approach, involving stratigraphy, phylogenetics, and sclerochronology, is necessary to better understand the ecologic and evolutionary underpinnings of the ‘effect’. This approach needs to be more uniformly applied to different extinctions and taxonomic groups, allowing a more effective comparison and resulting in a more holistic perspective on the ‘Lilliput Effect’.
New analyses reveal two intervals of distinctly lower δ13C values in the terrestrial organic matter of Permian–Triassic sequences in northern Xinjiang, China. The younger negative δ13Corg spike can be correlated to the conspicuous and sharp δ13C drops both in carbonate carbon and organic carbon near the Permian–Triassic event boundary (PTEB) in the marine section at Meishan. The geochemical correlation criteria are accompanied by a magnetic susceptibility pulse and higher abundances of distinctive, chain-like organic fossil remains of Reduviasporonites.The older negative δ13Corg spike originates within a latest Permian regression. Significant changes in organic geochemical proxies are recorded in the equivalent interval of the marine section at Meishan. These include relatively higher concentrations of total organic carbon, isorenieratane, C14–C30 aryl isoprenoids and lower ratios of pristane/phytane that, together, indicate the onset of anoxic, euxinic and restricted environments within the photic zone. The massive and widespread oxidation of buried organic matter that induced these euxinic conditions in the ocean would also result in increased concentrations of 13C-depleted atmospheric CO2. The latest Permian environmental stress marked by the older negative δ13Corg episode can be correlated with the distinct changeover of ostracod assemblages and the occurrences of morphological abnormalities of pollen grains. These observations imply that biogeochemical disturbance was manifested on the land at the end of the Permian and that terrestrial organisms responded to it before the main extinction of the marine fauna.
The Elikah River section spanning the Lopingian (Late Permian) to the Griesbachian (Early Triassic) time interval in the Central Alborz Mountains (north Iran) was sampled for ostracod analysis. We report 79 species distributed among 38 genera. Four new species are described: Acratia? pervagata Forel sp. nov., Microcheilinella alborzella Forel sp. nov., Basslerella superarella Crasquin sp. nov. and Cavellina nesenensis Crasquin sp. nov. The ontogeny of 13 species is described and sexual dimorphism in the genus Microcheilinella is here undoubtedly recognized for the first time. Six species show precocious sexual dimorphism of their carapace as early as A-5 juvenile. The Lilliput effect is for the first time recorded and quantified for two species. Rare long-time span Palaeocopida species, known throughout the entire Permian, document relatively long-term evolution, including the size and growth rate modifications associated with the earlier appearance of carapace sexual dimorphism through time. These patterns might be related to the Guadalupian–Lopingian events and/or to climatic modifications occurring during the Permian interval.
During the International Peri-Tethys Program, the realization of the maps required efficient correlation tools. During the Late Paleozoic and particularly during the Wordian (Middle Permian), the Russian Platform was under continental and/or marginal paleoenvironmental conditions. This paper draws up the synthesis of the ostracode species recognized in the Middle-Late Permian in this area, from the Barents Sea up to the Precaspian Depression, and shows their importance as a stratigraphic tool for the correlations of continental series.
The most important Eurasian sections, where the transitional Permian/Triassic boundary beds are characterized palaeontologically, are found in the Germanic Basin (West European platform), Moscow Basin (East European platform), Tungusska Basin (Siberian platform), Jimsar Basin, Dalongkou area (Tianshan Mountains), and Noyan Somon depression (Mongolia). Usually the Permian and Triassic continental formations formed under distinct palaeogeographic (especially climatic) and palaeotectonic conditions, so the lithological and sedimentological differences between them are pronounced. Difficult problems appear in those regions where the sedimentation at this level proceeded under very similar conditions (Tungusska Basin, Jimsar Basin) across the Permo–Triassic boundary (PTB). Among palaeontological data, the most important for correlation of these continental beds is the tetrapod fauna. Broad interchange between the tetrapod fauna of the Old World continents resulted in the wide distribution during the Late Permian and Early Triassic of common or closely related forms, which enables distant correlations. The PTB is marked by the change of the Late Permian tetrapod communities, dominated by the large herbivore Dicynodon (or closely allied forms), to assemblages that include Lystrosaurus as the most common form. This is recorded in Lower Triassic beds of Eastern Europe, China, Mongolia, India and Siberia. The Upper Permian sporomorph associations (sa) are dominated by striate bissacate pollen, whereas the early Lower Triassic ones are distinguished by the very important role of spores, primarily by cavate trilete (Lundbladispora, Densoisporites) and also by non-striate dissacate (Klausipollenites) and teniate pollen (Lunatisporites). In the oldest horizons of the Triassic, very distinctive species of conchostracans (Falsisca eotriassica Kozur or the closely related form F. verhojanica Molin) appear. The PTB is within a normal polarity zone, formerly considered the lowest palaeomagnetic zone of the Triassic. The boundary beds of two sections (Moscow Basin and Jimsar Basin) may be equally worthy as candidates for the PTB GSSP in the continental series. The preference should be given to the section better characterized and internationally accessible to scientists. The PTB generally accepted for the continental series coincides more or less with the base of the Otoceras concavum ammonite zone of the Boreal province, and with the base of the boundary clay in Tethys. At the same time, it lies clearly below the traditionally adopted PTB in marine sequences at the base of the Otoceras woodwardi zone and also below the First Appearance Datum (FAD) of I. parva in the Meishan section, proposed now as the PTB GSSP (Yin, 1996, The Palaeozoic–Mesozoic Boundary Candidate of Global Stratotype Section and Point of the Permian–Triassic Boundary, China University Geoscience Press, Wuhan, 137 pp.). This demonstrates that the FAD of I. parva can be asynchronous (see Baud, 1996, Albertiana 18, pp. 6–9). That is why in the choice of the PTB GSSP in the marine series it is necessary to take into consideration the generally accepted point of view on the position of PTB in the continental series.
Four major biotic crises are recognized in the history of the Upper Silurian graptoloids. While the causes of extinction are largely unknown, the scenarios of the crises are fairly well ascertained. A model of recovery proposed here implies two alternatives: (1) some of the relic species exhibit great abundance frequently associated with a subnormal phenotype (the post‐event syndrome) and the ensuing rediversification involves indigenous speciation or (2) as a result of the lack of evolutionary response on the part of the local survivors, vacant habitats are filled by immigrants. Numerous cryptic and Lazarus taxa among the immigrants indicate the presence of pelagic refuges and centers of evolution. They may be identified as Central Water masses bounded by gyres.
Conchostracan-rich beds between the Siberian Trap flood basalts and within the thick underlying Hungtukun tuffs of the Tunguska Basin can be closely correlated with conchostracan faunas of Dalongkou (NW China) and the Germanic Basin. The Germanic Basin faunas in turn can be closely correlated with the marine international stratigraphic time scale, and the accuracy of the biostratigraphic correlation of the Permian–Triassic boundary (PTB) is confirmed by a minimum in δ 13 C carb values at this level. These high-resolution correlations demonstrate conclusively that the PTB is located within the temporally brief but thick Siberian Trap flood basalt sequence. The PTB lies slightly above the level of the main Permo-Triassic extinction event in low latitude marine beds, which occurred at the base of the C. meishanensis–H. praeparvus conodont zone and correlates with the beginning of the Siberian Trap flood basalt event. The main end-Permian continental extinction event was somewhat earlier, within the middle of the C. changxingensis–C. deflecta conodont zone. This horizon marks a mass extinction that devastated a diverse conchostracan fauna and left only low diversity faunas at low and high latitudes. This continental extinction event horizon lies within the middle of the Hungtukun tuffs of the Tunguska Basin and 107 m above the base of the Guodikeng Formation at Dalongkou (NW China). A "Triassic type" pioneer flora with numerous lycopod spores appears immediately above this level. Severe high northern and southern latitude marine extinctions occurred concurrently with this continental event, but low latitude marine biota was not then affected. This earlier event is best explained by global warming. The main low latitude extinction event in marine warm water faunas occurred somewhat later and left no signature in high latitude marine faunas or in continental faunas, but it does coincide with a rapid collapse of tropical rain forest environments (disappearance of the highly diverse Gigantopteris flora). This collapse likely was caused by global cooling due to a volcanic winter event. Published by Elsevier B.V.
Measured lithostratigraphic sections of the classic Permian–Triassic non-marine transitional sequences covering the upper Quanzijie, Wutonggou, Guodikeng and lower Jiucaiyuan Formations at Dalongkou and Lucaogou, Xinjiang Province, China are presented. These measured sections form the framework and reference sections for a range of multi-disciplinary studies of the P–T transition in this large ancient lake basin, including palynostratigraphy, vertebrate biostratigraphy, chemostratigraphy and magnetostratigraphy. The 121 m thick Wutonggou Formation at Dalongkou includes 12 sandstone units ranging in thickness from 0.5 to 10.5 m that represent cyclical coarse terrigenous input to the lake basin during the Late Permian. The rhythmically-bedded, mudstone-dominated Guodikeng Formation is 197 m and 209 m thick on the north and south limbs of the Dalongkou anticline, respectively, and 129 m thick at Lucaogou. Based on limited palynological data, the Permian–Triassic boundary was previously placed approximately 50 m below the top of this formation at Dalongkou. This boundary does not coincide with any mappable lithologic unit, such as the basal sandstones of the overlying Jiucaiyuan Formation, assigned to the Early Triassic. The presence of multiple organic δ13C-isotope excursions, mutant pollen, and multiple algal and conchostracan blooms in this formation, together with Late Permian palynomorphs, suggests that the Guodikeng Formation records multiple climatic perturbation signals representing environmental stress during the late Permian mass extinction interval. The overlap between the vertebrates Dicynodon and Lystrosaurus in the upper part of this formation, and the occurrence of late Permian spores and the latest Permian to earliest Triassic megaspore Otynisporites eotriassicus is consistent with a latest Permian age for at least part of the Guodikeng Formation. Palynostratigrahic placement of the Permian–Triassic boundary in the Junggar Basin remains problematic because key miospore taxa, such as Aratrisporites spp. are not present. Palynomorphs from the Guodikeng are assigned to two assemblages; the youngest, from the upper 100 m of the formation (and the overlying Jiucaiyuan Formation), contains both typical Permian elements and distinctive taxa that elsewhere are known from the Early Triassic of Canada, Greenland, Norway, and Russia. The latter include spores assigned to Pechorosporites disertus, Lundbladisporafoveota, Naumovaspora striata, Decussatisporites mulstrigatus and Leptolepidites jonkerii. While the presence of Devonian and Carboniferous spores and Early Permian pollen demonstrate reworking is occurring in the Guodikeng assemblages, the sometimes common occurrence of Scutasporites sp. cf. Scutasporites unicus, and other pollen, suggests that the Late Permian elements are in place, and that the upper assemblage derives from a genuine transitional flora of Early Triassic aspect. In the Junggar Basin, biostratigraphic data and magnetostratigraphic data indicate that the Permian–Triassic boundary (GSSP Level) is in the middle to upper Guodikeng Formation and perhaps as high as the formational contact with the overlying Jiucaiyuan Formation.
Evolutionary trends in Late Permian Darwinulocopina are summarised with reference to extensive collections from eastern European Russia, from the White Sea in the North to the Cis-Caspian in the South. They inhabited large, shallow lakes in which the variety of habitats was favourable for high ostracod diversity. Three superfamilies are represented: the Darwinuloidea preferred lakes with terrigenous sedimentation and insignificant bicarbonate, the Suchonelloidea inhabited lakes with increased bicarbonate and could also live in low-sulphate waters, and the Darwinuloidoidea inhabited high-bicarbonate water bodies and could also survive in low-magnesium waters. Different evolutionary trends account for the different ages of the crucial stages of development of each superfamily: the beginning of the mid-Tatarian for the Darwinuloidea, the late Tatarian for the Suchonelloidea and Darwinuloidoidea.
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