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A new basal sauropod dinosaur from the middle Jurassic of Niger and the early evolution of sauropoda.

Remes K, Ortega F, Fierro I, Joger U, Kosma R, Ferrer JM, Project PALDESNiger Project SNHMIde OA, Maga A - PLoS ONE (2009)

Bottom Line: Spinophorosaurus demonstrates that many putatively derived characters of Middle Jurassic East Asian sauropods are plesiomorphic for eusauropods, while South Gondwanan eusauropods may represent a specialized line.The anatomy of Spinophorosaurus indicates that key innovations in Jurassic sauropod evolution might have taken place in North Africa, an area close to the equator with summer-wet climate at that time.Jurassic climatic zones and phytogeography possibly controlled early sauropod diversification.

View Article: PubMed Central - PubMed

Affiliation: Paleontology, Steinmann Institute for Geology, Mineralogy and Paleontology, University of Bonn, Bonn, Germany. kristian.remes@uni-bonn.de

ABSTRACT

Background: The early evolution of sauropod dinosaurs is poorly understood because of a highly incomplete fossil record. New discoveries of Early and Middle Jurassic sauropods have a great potential to lead to a better understanding of early sauropod evolution and to reevaluate the patterns of sauropod diversification.

Principal findings: A new sauropod from the Middle Jurassic of Niger, Spinophorosaurus nigerensis n. gen. et sp., is the most complete basal sauropod currently known. The taxon shares many anatomical characters with Middle Jurassic East Asian sauropods, while it is strongly dissimilar to Lower and Middle Jurassic South American and Indian forms. A possible explanation for this pattern is a separation of Laurasian and South Gondwanan Middle Jurassic sauropod faunas by geographic barriers. Integration of phylogenetic analyses and paleogeographic data reveals congruence between early sauropod evolution and hypotheses about Jurassic paleoclimate and phytogeography.

Conclusions: Spinophorosaurus demonstrates that many putatively derived characters of Middle Jurassic East Asian sauropods are plesiomorphic for eusauropods, while South Gondwanan eusauropods may represent a specialized line. The anatomy of Spinophorosaurus indicates that key innovations in Jurassic sauropod evolution might have taken place in North Africa, an area close to the equator with summer-wet climate at that time. Jurassic climatic zones and phytogeography possibly controlled early sauropod diversification.

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Phylogenetic relationships of Spinophorosaurus, based on an analysis of 27 taxa and 235 characters.(A)— Single most parsimonious tree. Numbers next to nodes indicate bootstrap support values for nodes that show more than 50% support. White numbers in black circles: 1, Sauropoda; 2, Eusauropoda; 3, Neosauropoda; 4, Mamenchisauridae. Dashed line indicates alternative sister-group relationship of Barapasaurus and Patagosaurus as hypothesized in the main text, requiring only a single additional step. (B)— Proposed evolutionary scenario of early sauropods with an endemic South Gondwanan clade during the Lower and Middle Jurassic. White bars indicate insecurities in the dating of the formations in which these taxa were found. Abbreviation: CGD, Central Gondwanan Desert.
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pone-0006924-g006: Phylogenetic relationships of Spinophorosaurus, based on an analysis of 27 taxa and 235 characters.(A)— Single most parsimonious tree. Numbers next to nodes indicate bootstrap support values for nodes that show more than 50% support. White numbers in black circles: 1, Sauropoda; 2, Eusauropoda; 3, Neosauropoda; 4, Mamenchisauridae. Dashed line indicates alternative sister-group relationship of Barapasaurus and Patagosaurus as hypothesized in the main text, requiring only a single additional step. (B)— Proposed evolutionary scenario of early sauropods with an endemic South Gondwanan clade during the Lower and Middle Jurassic. White bars indicate insecurities in the dating of the formations in which these taxa were found. Abbreviation: CGD, Central Gondwanan Desert.

Mentions: A data matrix based on [40] containing 28 operational taxonomical units and 235 anatomical characters (see Methods, Text S1, and Dataset S1) was analyzed with PAUP* 4.0b10 [44], using a heuristic search with random setting and 1000 replicates (following the settings used in [40]). Plateosaurus was defined as an outgroup and used to root the tree. The analysis resulted in a single most parsimonious tree (length 515 steps, CI 0.551, RI 0.667, RC 0.368; Dataset S2). Bootstrap analysis was run on the matrix with simple addition heuristic search and 1000 bootstrap replicates. Calculated bootstrap support values of more than 50% are included in Fig. 6A.


A new basal sauropod dinosaur from the middle Jurassic of Niger and the early evolution of sauropoda.

Remes K, Ortega F, Fierro I, Joger U, Kosma R, Ferrer JM, Project PALDESNiger Project SNHMIde OA, Maga A - PLoS ONE (2009)

Phylogenetic relationships of Spinophorosaurus, based on an analysis of 27 taxa and 235 characters.(A)— Single most parsimonious tree. Numbers next to nodes indicate bootstrap support values for nodes that show more than 50% support. White numbers in black circles: 1, Sauropoda; 2, Eusauropoda; 3, Neosauropoda; 4, Mamenchisauridae. Dashed line indicates alternative sister-group relationship of Barapasaurus and Patagosaurus as hypothesized in the main text, requiring only a single additional step. (B)— Proposed evolutionary scenario of early sauropods with an endemic South Gondwanan clade during the Lower and Middle Jurassic. White bars indicate insecurities in the dating of the formations in which these taxa were found. Abbreviation: CGD, Central Gondwanan Desert.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2737122&req=5

pone-0006924-g006: Phylogenetic relationships of Spinophorosaurus, based on an analysis of 27 taxa and 235 characters.(A)— Single most parsimonious tree. Numbers next to nodes indicate bootstrap support values for nodes that show more than 50% support. White numbers in black circles: 1, Sauropoda; 2, Eusauropoda; 3, Neosauropoda; 4, Mamenchisauridae. Dashed line indicates alternative sister-group relationship of Barapasaurus and Patagosaurus as hypothesized in the main text, requiring only a single additional step. (B)— Proposed evolutionary scenario of early sauropods with an endemic South Gondwanan clade during the Lower and Middle Jurassic. White bars indicate insecurities in the dating of the formations in which these taxa were found. Abbreviation: CGD, Central Gondwanan Desert.
Mentions: A data matrix based on [40] containing 28 operational taxonomical units and 235 anatomical characters (see Methods, Text S1, and Dataset S1) was analyzed with PAUP* 4.0b10 [44], using a heuristic search with random setting and 1000 replicates (following the settings used in [40]). Plateosaurus was defined as an outgroup and used to root the tree. The analysis resulted in a single most parsimonious tree (length 515 steps, CI 0.551, RI 0.667, RC 0.368; Dataset S2). Bootstrap analysis was run on the matrix with simple addition heuristic search and 1000 bootstrap replicates. Calculated bootstrap support values of more than 50% are included in Fig. 6A.

Bottom Line: Spinophorosaurus demonstrates that many putatively derived characters of Middle Jurassic East Asian sauropods are plesiomorphic for eusauropods, while South Gondwanan eusauropods may represent a specialized line.The anatomy of Spinophorosaurus indicates that key innovations in Jurassic sauropod evolution might have taken place in North Africa, an area close to the equator with summer-wet climate at that time.Jurassic climatic zones and phytogeography possibly controlled early sauropod diversification.

View Article: PubMed Central - PubMed

Affiliation: Paleontology, Steinmann Institute for Geology, Mineralogy and Paleontology, University of Bonn, Bonn, Germany. kristian.remes@uni-bonn.de

ABSTRACT

Background: The early evolution of sauropod dinosaurs is poorly understood because of a highly incomplete fossil record. New discoveries of Early and Middle Jurassic sauropods have a great potential to lead to a better understanding of early sauropod evolution and to reevaluate the patterns of sauropod diversification.

Principal findings: A new sauropod from the Middle Jurassic of Niger, Spinophorosaurus nigerensis n. gen. et sp., is the most complete basal sauropod currently known. The taxon shares many anatomical characters with Middle Jurassic East Asian sauropods, while it is strongly dissimilar to Lower and Middle Jurassic South American and Indian forms. A possible explanation for this pattern is a separation of Laurasian and South Gondwanan Middle Jurassic sauropod faunas by geographic barriers. Integration of phylogenetic analyses and paleogeographic data reveals congruence between early sauropod evolution and hypotheses about Jurassic paleoclimate and phytogeography.

Conclusions: Spinophorosaurus demonstrates that many putatively derived characters of Middle Jurassic East Asian sauropods are plesiomorphic for eusauropods, while South Gondwanan eusauropods may represent a specialized line. The anatomy of Spinophorosaurus indicates that key innovations in Jurassic sauropod evolution might have taken place in North Africa, an area close to the equator with summer-wet climate at that time. Jurassic climatic zones and phytogeography possibly controlled early sauropod diversification.

Show MeSH
Related in: MedlinePlus