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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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Spinophorosaurus nigerensis GCP-CV-4229 (holotype).(Aā€“C)ā€” Braincase in dorsal (A), caudal (B), and left lateral (C) views. (D, E)ā€” Right quadrate and pterygoid in lateral (D) and medial (E) views. (F, G)ā€” Dorsal end of right quadrate in lateral (F) and caudal (G) views. Scale bars ā€Š=ā€Š10 cm (Aā€“C), 5 cm (D, E), and 2 cm (F, G).
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pone-0006924-g002: Spinophorosaurus nigerensis GCP-CV-4229 (holotype).(Aā€“C)ā€” Braincase in dorsal (A), caudal (B), and left lateral (C) views. (D, E)ā€” Right quadrate and pterygoid in lateral (D) and medial (E) views. (F, G)ā€” Dorsal end of right quadrate in lateral (F) and caudal (G) views. Scale bars ā€Š=ā€Š10 cm (Aā€“C), 5 cm (D, E), and 2 cm (F, G).

Mentions: The skull roof of Spinophorosaurus (Fig. 2Aā€“C) is characterized by frontals that are, unlike the remaining skull sutures, fused in midline and bear a small median pineal foramen about 10 mm rostral to the frontoparietal suture. The specimen has an open postparietal notch, otherwise known only from dicraeosaurids [16], [17] and the Chinese Abrosaurus [18]. The base of the occipital condyle is concave laterally, as in Shunosaurus [19]. The enlarged basal tubera are laterally directed, unlike any other known sauropod. The quadrate lacks a concavity on its caudal side (Fig. 2Dā€“G), a plesiomorphic condition otherwise reported only for Tazoudasaurus among Sauropoda [20]. The teeth of Spinophorosaurus are unique in having spaced, enlarged denticles in the apical region of the crown, with a higher denticle count on the mesial carina (Fig. S1).


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)

Spinophorosaurus nigerensis GCP-CV-4229 (holotype).(Aā€“C)ā€” Braincase in dorsal (A), caudal (B), and left lateral (C) views. (D, E)ā€” Right quadrate and pterygoid in lateral (D) and medial (E) views. (F, G)ā€” Dorsal end of right quadrate in lateral (F) and caudal (G) views. Scale bars ā€Š=ā€Š10 cm (Aā€“C), 5 cm (D, E), and 2 cm (F, G).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0006924-g002: Spinophorosaurus nigerensis GCP-CV-4229 (holotype).(Aā€“C)ā€” Braincase in dorsal (A), caudal (B), and left lateral (C) views. (D, E)ā€” Right quadrate and pterygoid in lateral (D) and medial (E) views. (F, G)ā€” Dorsal end of right quadrate in lateral (F) and caudal (G) views. Scale bars ā€Š=ā€Š10 cm (Aā€“C), 5 cm (D, E), and 2 cm (F, G).
Mentions: The skull roof of Spinophorosaurus (Fig. 2Aā€“C) is characterized by frontals that are, unlike the remaining skull sutures, fused in midline and bear a small median pineal foramen about 10 mm rostral to the frontoparietal suture. The specimen has an open postparietal notch, otherwise known only from dicraeosaurids [16], [17] and the Chinese Abrosaurus [18]. The base of the occipital condyle is concave laterally, as in Shunosaurus [19]. The enlarged basal tubera are laterally directed, unlike any other known sauropod. The quadrate lacks a concavity on its caudal side (Fig. 2Dā€“G), a plesiomorphic condition otherwise reported only for Tazoudasaurus among Sauropoda [20]. The teeth of Spinophorosaurus are unique in having spaced, enlarged denticles in the apical region of the crown, with a higher denticle count on the mesial carina (Fig. S1).

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