L. Leuzinger, L. Kocsis, Zoneibe Luz, T. Vennemann, A. Ulyanov, M. Fernández
Abstract. Here we report high-latitude stable isotope compositions of Maastrichtian fossil fish and marine reptiles (mainly mosasaurs) from Antarctica (64°S paleolatitude) and compare them with mid-paleolatitude samples from Argentine Patagonia (45°S). Disparities between the δ13C values of bony fish and marine reptiles correspond to differences in the foraging ground (distance from the shore and depth), while dramatically higher δ13C values (by 18‰) in shark enameloid cannot be explained through ecology and are here imputed to biomineralization. Comparison with extant vertebrates suggests that the diet alone can explain the offset observed between bony fish and mosasaurs; however, breath holding due to a diving behavior in mosasaurs may have had some impact on their δ13C values, as previously suggested. The δ18OPO4 values of the remains confirm a relatively stable, elevated body temperature for marine reptiles, meaning that they were thermoregulators. We calculated a water temperature of ∼8°C for Antarctica from the fish δ18OPO4 values, warmer than present-day temperatures and consistent with the absence of polar ice sheets during the latest Maastrichtian. Our fish data greatly extend the latitudinal range of Late Cretaceous fish δ18OPO4 values and result in a thermal gradient of 0.4°C/1° of latitude when combined with literature data.
{"title":"Latest Maastrichtian middle- and high-latitude mosasaurs and fish isotopic composition: carbon source, thermoregulation strategy, and thermal latitudinal gradient","authors":"L. Leuzinger, L. Kocsis, Zoneibe Luz, T. Vennemann, A. Ulyanov, M. Fernández","doi":"10.1017/pab.2022.38","DOIUrl":"https://doi.org/10.1017/pab.2022.38","url":null,"abstract":"Abstract. Here we report high-latitude stable isotope compositions of Maastrichtian fossil fish and marine reptiles (mainly mosasaurs) from Antarctica (64°S paleolatitude) and compare them with mid-paleolatitude samples from Argentine Patagonia (45°S). Disparities between the δ13C values of bony fish and marine reptiles correspond to differences in the foraging ground (distance from the shore and depth), while dramatically higher δ13C values (by 18‰) in shark enameloid cannot be explained through ecology and are here imputed to biomineralization. Comparison with extant vertebrates suggests that the diet alone can explain the offset observed between bony fish and mosasaurs; however, breath holding due to a diving behavior in mosasaurs may have had some impact on their δ13C values, as previously suggested. The δ18OPO4 values of the remains confirm a relatively stable, elevated body temperature for marine reptiles, meaning that they were thermoregulators. We calculated a water temperature of ∼8°C for Antarctica from the fish δ18OPO4 values, warmer than present-day temperatures and consistent with the absence of polar ice sheets during the latest Maastrichtian. Our fish data greatly extend the latitudinal range of Late Cretaceous fish δ18OPO4 values and result in a thermal gradient of 0.4°C/1° of latitude when combined with literature data.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":"49 1","pages":"353 - 373"},"PeriodicalIF":2.7,"publicationDate":"2022-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42635314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. The Cambrian saw a dramatic increase in metazoan diversity and abundance. Between-assemblage diversity (beta diversity) soared in the first three Cambrian stages, suggesting a rapid increase in the geodisparity of marine animals during the Cambrian radiation. However, it remains unclear how these changes scale up to first-order biogeographic patterns. Here we outline time-traceable provinces for marine invertebrates across the Cambrian period using a compositional network based on species-level fossil occurrence data. Results confirm an increase in regional differences of faunal composition and a decrease in by-species geographic distribution during the first three stages. We also show that general biogeography tends to be reshaped after global extinction pulses. We suggest that the abrupt biogeographic differentiation during the Cambrian radiation was controlled by a combination of tectonics, paleoclimate, and dispersal capacity changes.
{"title":"Coupling of geographic range and provincialism in Cambrian marine invertebrates","authors":"L. Na, Á. Kocsis, Qijian Li, W. Kiessling","doi":"10.1017/pab.2022.36","DOIUrl":"https://doi.org/10.1017/pab.2022.36","url":null,"abstract":"Abstract. The Cambrian saw a dramatic increase in metazoan diversity and abundance. Between-assemblage diversity (beta diversity) soared in the first three Cambrian stages, suggesting a rapid increase in the geodisparity of marine animals during the Cambrian radiation. However, it remains unclear how these changes scale up to first-order biogeographic patterns. Here we outline time-traceable provinces for marine invertebrates across the Cambrian period using a compositional network based on species-level fossil occurrence data. Results confirm an increase in regional differences of faunal composition and a decrease in by-species geographic distribution during the first three stages. We also show that general biogeography tends to be reshaped after global extinction pulses. We suggest that the abrupt biogeographic differentiation during the Cambrian radiation was controlled by a combination of tectonics, paleoclimate, and dispersal capacity changes.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":"49 1","pages":"284 - 295"},"PeriodicalIF":2.7,"publicationDate":"2022-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49665603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. The ecogeographic rule known as Bergmann's rule suggests that there is a positive relationship between body size and latitude when comparing closely related taxa. The underlying mechanism or mechanisms to explain this pattern vary as widely as the taxa that seem to follow it, which has led to skepticism over whether Bergmann's rule should be considered a rule at all. Despite this, Bergmann's rule is widespread among modern birds, mammals, beetles, and some amphibians, but far fewer extinct taxa have been subjected to tests of Bergmann's rule. To examine whether Bergmann's rule is detected in extinct taxa, we compared body-size proxies in Lystrosaurus recovered from Early Triassic–aged strata in Antarctica, South Africa, India, and China. Our results reveal that average body size is largest at mid-northern paleolatitudes (∼45°N) instead of the highest southern paleolatitudes (∼70°S). Additionally, maximum body size is consistent across the Northern and Southern Hemispheres, indicating that Bergmann's rule did not apply for Lystrosaurus during the Early Triassic. To test potential sample size biases in our results, we used rarefaction and subsampling to show that only the Karoo Basin is well sampled and that large individuals are exceedingly rare, except in the Turpan-Junggar Basin of Xinjiang, China. Taken together, our results suggest that Lystrosaurus had the potential to reach large body sizes in each of the latitudinally widespread geologic basins studied here, but that local conditions may have allowed individuals at mid-northern paleolatitudes a greater chance of reaching a large size compared with southern congeners that suffered increased mortality when young or at a small size.
{"title":"A test of Bergmann's rule in the Early Triassic: latitude, body size, and sampling in Lystrosaurus","authors":"Z. Kulik, C. Sidor","doi":"10.1017/pab.2022.25","DOIUrl":"https://doi.org/10.1017/pab.2022.25","url":null,"abstract":"Abstract. The ecogeographic rule known as Bergmann's rule suggests that there is a positive relationship between body size and latitude when comparing closely related taxa. The underlying mechanism or mechanisms to explain this pattern vary as widely as the taxa that seem to follow it, which has led to skepticism over whether Bergmann's rule should be considered a rule at all. Despite this, Bergmann's rule is widespread among modern birds, mammals, beetles, and some amphibians, but far fewer extinct taxa have been subjected to tests of Bergmann's rule. To examine whether Bergmann's rule is detected in extinct taxa, we compared body-size proxies in Lystrosaurus recovered from Early Triassic–aged strata in Antarctica, South Africa, India, and China. Our results reveal that average body size is largest at mid-northern paleolatitudes (∼45°N) instead of the highest southern paleolatitudes (∼70°S). Additionally, maximum body size is consistent across the Northern and Southern Hemispheres, indicating that Bergmann's rule did not apply for Lystrosaurus during the Early Triassic. To test potential sample size biases in our results, we used rarefaction and subsampling to show that only the Karoo Basin is well sampled and that large individuals are exceedingly rare, except in the Turpan-Junggar Basin of Xinjiang, China. Taken together, our results suggest that Lystrosaurus had the potential to reach large body sizes in each of the latitudinally widespread geologic basins studied here, but that local conditions may have allowed individuals at mid-northern paleolatitudes a greater chance of reaching a large size compared with southern congeners that suffered increased mortality when young or at a small size.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":"49 1","pages":"53 - 67"},"PeriodicalIF":2.7,"publicationDate":"2022-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47423153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Cubo, P. Aubier, Mathieu G. Faure-Brac, Gaspard Martet, Romain Pellarin, Idriss Pelletan, M. Sena
Abstract. Notosuchia is a group of mostly terrestrial crocodyliforms. The presence of a prominent crest overhanging the acetabulum, slender straight-shafted long bones with muscular insertions close to the joints, and a stable knee joint suggests that they had an erect posture. This stance has been proposed to be linked to endothermy, because it is present in mammals and birds and contributes to the efficiency of their respiratory systems. However, a bone paleohistological study unexpectedly suggested that Notosuchia were ectothermic organisms. The thermophysiological status of Notosuchia deserves further analysis, because the methodology of the previous study can be improved. First, it was based on a relationship between red blood cell size and bone vascular canal diameter tested using 14 extant tetrapod species. Here we present evidence for this relationship using a more comprehensive sample of extant tetrapods (31 species). Moreover, contrary to previous results, bone cross-sectional area appears to be a significant explanatory variable (in addition to vascular canal diameter). Second, red blood cell size estimations were performed using phylogenetic eigenvector maps, and this method excludes a fraction of the phylogenetic information. This is because it generates a high number of eigenvectors requiring a selection procedure to compile a subset of them to avoid model overfitting. Here we inferred the thermophysiology of Notosuchia using phylogenetic logistic regressions, a method that overcomes this problem by including all of the phylogenetic information and a sample of 46 tetrapods. These analyses suggest that Araripesuchus wegeneri, Armadillosuchus arrudai, Baurusuchus sp., Iberosuchus macrodon, and Stratiotosuchus maxhechti were ectothermic organisms.
{"title":"Paleohistological inferences of thermometabolic regimes in Notosuchia (Pseudosuchia: Crocodylomorpha) revisited","authors":"J. Cubo, P. Aubier, Mathieu G. Faure-Brac, Gaspard Martet, Romain Pellarin, Idriss Pelletan, M. Sena","doi":"10.1017/pab.2022.28","DOIUrl":"https://doi.org/10.1017/pab.2022.28","url":null,"abstract":"Abstract. Notosuchia is a group of mostly terrestrial crocodyliforms. The presence of a prominent crest overhanging the acetabulum, slender straight-shafted long bones with muscular insertions close to the joints, and a stable knee joint suggests that they had an erect posture. This stance has been proposed to be linked to endothermy, because it is present in mammals and birds and contributes to the efficiency of their respiratory systems. However, a bone paleohistological study unexpectedly suggested that Notosuchia were ectothermic organisms. The thermophysiological status of Notosuchia deserves further analysis, because the methodology of the previous study can be improved. First, it was based on a relationship between red blood cell size and bone vascular canal diameter tested using 14 extant tetrapod species. Here we present evidence for this relationship using a more comprehensive sample of extant tetrapods (31 species). Moreover, contrary to previous results, bone cross-sectional area appears to be a significant explanatory variable (in addition to vascular canal diameter). Second, red blood cell size estimations were performed using phylogenetic eigenvector maps, and this method excludes a fraction of the phylogenetic information. This is because it generates a high number of eigenvectors requiring a selection procedure to compile a subset of them to avoid model overfitting. Here we inferred the thermophysiology of Notosuchia using phylogenetic logistic regressions, a method that overcomes this problem by including all of the phylogenetic information and a sample of 46 tetrapods. These analyses suggest that Araripesuchus wegeneri, Armadillosuchus arrudai, Baurusuchus sp., Iberosuchus macrodon, and Stratiotosuchus maxhechti were ectothermic organisms.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":"49 1","pages":"342 - 352"},"PeriodicalIF":2.7,"publicationDate":"2022-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45874704","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Evolutionary events may impact the geological carbon cycle via transient imbalances in silicate weathering, and such events have been implicated as causes of glaciations, mass extinctions, and oceanic anoxia. However, suggested evolutionary causes often substantially predate the environmental effects to which they are linked—problematic when carbon cycle perturbations must be resolved in less than a million years to maintain Earth's habitability. What is more, the geochemical signatures of such perturbations are recorded as they occur in widely distributed marine sedimentary rocks that have been densely sampled for important intervals in Earth history, whereas the fossil record—particularly on land—is governed by the availability of sedimentary basins that are patchy in both space and time, necessitating lags between the origination of an evolutionary lineage and its earliest occurrence in the fossil record. Here, we present a simple model of the impact of preservational filtering on sampling to show that an evolutionary event that causes an environmental perturbation via weathering imbalance should not appear earlier in the rock record than the perturbation itself and, if anything, should appear later rather than simultaneously. The Devonian Hangenberg glaciation provides an example of how evolutionary events might be more fruitfully considered as potential causes of environmental perturbations. Just as the last samplings of species lost in mass extinction are expected to come before the true environmental event, first appearance should be expected to postdate the geological expression of a lineage's environmental impact with important implications for our reading of Earth history.
{"title":"The preservation of cause and effect in the rock record","authors":"Michael P. D'Antonio, D. Ibarra, C. Boyce","doi":"10.1017/pab.2022.33","DOIUrl":"https://doi.org/10.1017/pab.2022.33","url":null,"abstract":"Abstract. Evolutionary events may impact the geological carbon cycle via transient imbalances in silicate weathering, and such events have been implicated as causes of glaciations, mass extinctions, and oceanic anoxia. However, suggested evolutionary causes often substantially predate the environmental effects to which they are linked—problematic when carbon cycle perturbations must be resolved in less than a million years to maintain Earth's habitability. What is more, the geochemical signatures of such perturbations are recorded as they occur in widely distributed marine sedimentary rocks that have been densely sampled for important intervals in Earth history, whereas the fossil record—particularly on land—is governed by the availability of sedimentary basins that are patchy in both space and time, necessitating lags between the origination of an evolutionary lineage and its earliest occurrence in the fossil record. Here, we present a simple model of the impact of preservational filtering on sampling to show that an evolutionary event that causes an environmental perturbation via weathering imbalance should not appear earlier in the rock record than the perturbation itself and, if anything, should appear later rather than simultaneously. The Devonian Hangenberg glaciation provides an example of how evolutionary events might be more fruitfully considered as potential causes of environmental perturbations. Just as the last samplings of species lost in mass extinction are expected to come before the true environmental event, first appearance should be expected to postdate the geological expression of a lineage's environmental impact with important implications for our reading of Earth history.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":"49 1","pages":"204 - 214"},"PeriodicalIF":2.7,"publicationDate":"2022-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49488114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. The rise of jawed vertebrates (gnathostomes) and extinction of nearly all jawless vertebrates (agnathans) is one of the most important transitions in vertebrate evolution, but the causes are poorly understood. Competition between agnathans and gnathostomes during the Devonian period is the most commonly hypothesized cause; however, no formal attempts to test this hypothesis have been made. Generally, competition between species increases as morphological similarity increases; therefore, this study uses the largest to date morphometric comparison of Silurian and Devonian agnathan and gnathostome groups to determine which groups were most and least likely to have competed. Five agnathan groups (Anaspida, Heterostraci, Osteostraci, Thelodonti, and Furcacaudiformes) were compared with five gnathostome groups (Acanthodii, Actinopterygii, Chondrichthyes, Placodermi, and Sarcopterygii) including taxa from most major orders. Morphological dissimilarity was measured by Gower's dissimilarity coefficient, and the differences between agnathan and gnathostome body forms across early vertebrate morphospace were compared using principal coordinate analysis. Our results indicate competition between some agnathans and gnathostomes is plausible, but not all agnathan groups were similar to gnathostomes. Furcacaudiformes (fork-tailed thelodonts) are distinct from other early vertebrate groups and the least likely to have competed with other groups.
{"title":"Examining competition during the agnathan/gnathostome transition using distance-based morphometrics","authors":"B. Scott, P. S. Anderson","doi":"10.1017/pab.2022.32","DOIUrl":"https://doi.org/10.1017/pab.2022.32","url":null,"abstract":"Abstract. The rise of jawed vertebrates (gnathostomes) and extinction of nearly all jawless vertebrates (agnathans) is one of the most important transitions in vertebrate evolution, but the causes are poorly understood. Competition between agnathans and gnathostomes during the Devonian period is the most commonly hypothesized cause; however, no formal attempts to test this hypothesis have been made. Generally, competition between species increases as morphological similarity increases; therefore, this study uses the largest to date morphometric comparison of Silurian and Devonian agnathan and gnathostome groups to determine which groups were most and least likely to have competed. Five agnathan groups (Anaspida, Heterostraci, Osteostraci, Thelodonti, and Furcacaudiformes) were compared with five gnathostome groups (Acanthodii, Actinopterygii, Chondrichthyes, Placodermi, and Sarcopterygii) including taxa from most major orders. Morphological dissimilarity was measured by Gower's dissimilarity coefficient, and the differences between agnathan and gnathostome body forms across early vertebrate morphospace were compared using principal coordinate analysis. Our results indicate competition between some agnathans and gnathostomes is plausible, but not all agnathan groups were similar to gnathostomes. Furcacaudiformes (fork-tailed thelodonts) are distinct from other early vertebrate groups and the least likely to have competed with other groups.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":"49 1","pages":"313 - 328"},"PeriodicalIF":2.7,"publicationDate":"2022-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44874692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Bryozoans are active non-phototrophic biomineralizers that precipitate their calcareous skeletons in seawater. Carbonate saturation states varied temporally and spatially in Paleozoic oceans, and we used the Bryozoan Skeletal Index (BSI) to investigate whether bryozoan calcification was controlled by seawater chemistry in Paleozoic trepostome and cryptostome bryozoans. Our results show that cryptostome bryozoan genera were influenced by ocean chemistry throughout the Paleozoic and precipitated the most calcite at lower latitudes, where carbonate saturation states are generally higher, and less in midlatitudes, where carbonate will be relatively undersaturated. Trepostome bryozoan genera show a similar but weaker trend for the Ordovician to Devonian, suggesting that, like the cryptostomes, they were unable to metabolically overcome falling saturation states and simply precipitated less robust skeletons at higher latitudes. Carboniferous to Triassic trepostomes differ, however, and show a trend toward increased calcification at higher latitudes, indicating an ability to overcome unfavorable carbonate saturation states. Analysis of Permian trepostomes at the species level indicates this is most pronounced in the Southern Hemisphere, where calcification is matched by increased feeding capacity. It is proposed that this increased feeding capacity allowed trepostomes to metabolically overcome unfavorable carbonate saturation states. The differing responses of trepostome and cryptostome bryozoans to carbonate saturation states suggest that bryozoans should not be considered as a single group in marine extinctions linked to ocean chemistry changes. Likewise, it would suggest that modern stenolaemate and gymnolaemate bryozoans should be treated separately when considering their response to modern ocean chemistry changes.
{"title":"Latitudinal influences on bryozoan calcification through the Paleozoic","authors":"C. Reid, P. N. Wyse Jackson, M. Key","doi":"10.1017/pab.2022.31","DOIUrl":"https://doi.org/10.1017/pab.2022.31","url":null,"abstract":"Abstract. Bryozoans are active non-phototrophic biomineralizers that precipitate their calcareous skeletons in seawater. Carbonate saturation states varied temporally and spatially in Paleozoic oceans, and we used the Bryozoan Skeletal Index (BSI) to investigate whether bryozoan calcification was controlled by seawater chemistry in Paleozoic trepostome and cryptostome bryozoans. Our results show that cryptostome bryozoan genera were influenced by ocean chemistry throughout the Paleozoic and precipitated the most calcite at lower latitudes, where carbonate saturation states are generally higher, and less in midlatitudes, where carbonate will be relatively undersaturated. Trepostome bryozoan genera show a similar but weaker trend for the Ordovician to Devonian, suggesting that, like the cryptostomes, they were unable to metabolically overcome falling saturation states and simply precipitated less robust skeletons at higher latitudes. Carboniferous to Triassic trepostomes differ, however, and show a trend toward increased calcification at higher latitudes, indicating an ability to overcome unfavorable carbonate saturation states. Analysis of Permian trepostomes at the species level indicates this is most pronounced in the Southern Hemisphere, where calcification is matched by increased feeding capacity. It is proposed that this increased feeding capacity allowed trepostomes to metabolically overcome unfavorable carbonate saturation states. The differing responses of trepostome and cryptostome bryozoans to carbonate saturation states suggest that bryozoans should not be considered as a single group in marine extinctions linked to ocean chemistry changes. Likewise, it would suggest that modern stenolaemate and gymnolaemate bryozoans should be treated separately when considering their response to modern ocean chemistry changes.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":"49 1","pages":"271 - 283"},"PeriodicalIF":2.7,"publicationDate":"2022-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49203651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Bennion, J. MacLaren, Ellen J. Coombs, F. G. Marx, O. Lambert, V. Fischer
Abstract. The repeated return of tetrapods to aquatic life provides some of the best-known examples of convergent evolution. One comparison that has received relatively little focus is that of mosasaurids (a group of Late Cretaceous squamates) and archaic cetaceans (the ancestors of modern whales and dolphins), both of which show high levels of craniodental disparity, similar initial trends in locomotory evolution, and global distributions. Here we investigate convergence in skull ecomorphology during the initial aquatic radiations of these groups. A series of functionally informative ratios were calculated from 38 species, with ordination techniques used to reconstruct patterns of functional ecomorphospace occupation. The earliest fully aquatic members of each clade occupied different regions of ecomorphospace, with basilosaurids and early russellosaurines exhibiting marked differences in cranial functional morphology. Subsequent ecomorphological trajectories notably diverge: mosasaurids radiated across ecomorphospace with no clear pattern and numerous reversals, whereas cetaceans notably evolved toward shallower, more elongated snouts, perhaps as an adaptation for capturing smaller prey. Incomplete convergence between the two groups is present among megapredatory and longirostrine forms, suggesting stronger selection on cranial function in these two ecomorphologies. Our study highlights both the similarities and divergences in craniodental evolutionary trajectories between archaic cetaceans and mosasaurids, with convergences transcending their deeply divergent phylogenetic affinities.
{"title":"Convergence and constraint in the cranial evolution of mosasaurid reptiles and early cetaceans","authors":"R. Bennion, J. MacLaren, Ellen J. Coombs, F. G. Marx, O. Lambert, V. Fischer","doi":"10.1017/pab.2022.27","DOIUrl":"https://doi.org/10.1017/pab.2022.27","url":null,"abstract":"Abstract. The repeated return of tetrapods to aquatic life provides some of the best-known examples of convergent evolution. One comparison that has received relatively little focus is that of mosasaurids (a group of Late Cretaceous squamates) and archaic cetaceans (the ancestors of modern whales and dolphins), both of which show high levels of craniodental disparity, similar initial trends in locomotory evolution, and global distributions. Here we investigate convergence in skull ecomorphology during the initial aquatic radiations of these groups. A series of functionally informative ratios were calculated from 38 species, with ordination techniques used to reconstruct patterns of functional ecomorphospace occupation. The earliest fully aquatic members of each clade occupied different regions of ecomorphospace, with basilosaurids and early russellosaurines exhibiting marked differences in cranial functional morphology. Subsequent ecomorphological trajectories notably diverge: mosasaurids radiated across ecomorphospace with no clear pattern and numerous reversals, whereas cetaceans notably evolved toward shallower, more elongated snouts, perhaps as an adaptation for capturing smaller prey. Incomplete convergence between the two groups is present among megapredatory and longirostrine forms, suggesting stronger selection on cranial function in these two ecomorphologies. Our study highlights both the similarities and divergences in craniodental evolutionary trajectories between archaic cetaceans and mosasaurids, with convergences transcending their deeply divergent phylogenetic affinities.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":"49 1","pages":"215 - 231"},"PeriodicalIF":2.7,"publicationDate":"2022-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44686526","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Understanding current and future biodiversity responses to changing climate is pivotal as anthropogenic climate change continues. This understanding is complicated by the multitude of available metrics to quantify dynamics and by biased sampling protocols. Here, we investigate the impact of sampling protocol strategies using a data-rich fossil record to calculate effective diversity using Hill numbers for the first time on Paleogene planktonic foraminifera. We sample 22,830 individual tests, in two different size classes, across a 7 Myr time slice of the middle Eocene featuring a major transient warming event, the middle Eocene climatic optimum (MECO; ∼40 Ma), at study sites in the midlatitude North Atlantic. Using generalized additive models, we investigate community responses to climatic fluctuations. After correcting for any effects of fossil fragmentation, we show a peak in generic diversity in the early and middle stages of the MECO as well as divergent trajectories between the typical size-selected community (>180 µm) and a broader assemblage, including smaller genera (>63 µm). Assemblages featuring smaller genera are more resilient to the climatic fluctuations of the MECO than those assemblages that feature only larger genera, maintaining their community structure at the reference Hill numbers for Shannon's and Simpson's indices. These results raise fundamental questions about how communities respond to climate excursions. In addition, our results emphasize the need to design studies with the aim of collecting the most inclusive data possible to allow detection of community changes and determine which species are likely to dominate future environments.
{"title":"Small but mighty: how overlooked small species maintain community structure through middle Eocene climate change","authors":"L. Kearns, S. Bohaty, K. Edgar, T. Ezard","doi":"10.1017/pab.2022.24","DOIUrl":"https://doi.org/10.1017/pab.2022.24","url":null,"abstract":"Abstract. Understanding current and future biodiversity responses to changing climate is pivotal as anthropogenic climate change continues. This understanding is complicated by the multitude of available metrics to quantify dynamics and by biased sampling protocols. Here, we investigate the impact of sampling protocol strategies using a data-rich fossil record to calculate effective diversity using Hill numbers for the first time on Paleogene planktonic foraminifera. We sample 22,830 individual tests, in two different size classes, across a 7 Myr time slice of the middle Eocene featuring a major transient warming event, the middle Eocene climatic optimum (MECO; ∼40 Ma), at study sites in the midlatitude North Atlantic. Using generalized additive models, we investigate community responses to climatic fluctuations. After correcting for any effects of fossil fragmentation, we show a peak in generic diversity in the early and middle stages of the MECO as well as divergent trajectories between the typical size-selected community (>180 µm) and a broader assemblage, including smaller genera (>63 µm). Assemblages featuring smaller genera are more resilient to the climatic fluctuations of the MECO than those assemblages that feature only larger genera, maintaining their community structure at the reference Hill numbers for Shannon's and Simpson's indices. These results raise fundamental questions about how communities respond to climate excursions. In addition, our results emphasize the need to design studies with the aim of collecting the most inclusive data possible to allow detection of community changes and determine which species are likely to dominate future environments.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":"49 1","pages":"77 - 98"},"PeriodicalIF":2.7,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42682557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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