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The sail-backed reptile Ctenosauriscus from the latest Early Triassic of Germany and the timing and biogeography of the early archosaur radiation.

Butler RJ, Brusatte SL, Reich M, Nesbitt SJ, Schoch RR, Hornung JJ - PLoS ONE (2011)

Bottom Line: In addition, we describe Ctenosauriscus-like postcranial material from the earliest Middle Triassic (early Anisian) Röt Formation of Waldhaus, southwestern Germany.Comprehensive numerical phylogenetic analyses demonstrate that both Ctenosauriscus and the Waldhaus taxon are members of a monophyletic grouping of poposauroid archosaurs, Ctenosauriscidae, characterised by greatly elongated neural spines in the posterior cervical to anterior caudal vertebrae.The earliest archosaurs, including Ctenosauriscus, appear in the body fossil record just prior to the Olenekian/Anisian boundary (c. 248 Ma), less than 5 million years after the Permian-Triassic mass extinction.

View Article: PubMed Central - PubMed

Affiliation: Bayerische Staatssammlung für Paläontologie und Geologie, München, Germany. r.butler@lrz.uni-muenchen.de

ABSTRACT

Background: Archosaurs (birds, crocodilians and their extinct relatives including dinosaurs) dominated Mesozoic continental ecosystems from the Late Triassic onwards, and still form a major component of modern ecosystems (>10,000 species). The earliest diverse archosaur faunal assemblages are known from the Middle Triassic (c. 244 Ma), implying that the archosaur radiation began in the Early Triassic (252.3-247.2 Ma). Understanding of this radiation is currently limited by the poor early fossil record of the group in terms of skeletal remains.

Methodology/principal findings: We redescribe the anatomy and stratigraphic position of the type specimen of Ctenosauriscus koeneni (Huene), a sail-backed reptile from the Early Triassic (late Olenekian) Solling Formation of northern Germany that potentially represents the oldest known archosaur. We critically discuss previous biomechanical work on the 'sail' of Ctenosauriscus, which is formed by a series of elongated neural spines. In addition, we describe Ctenosauriscus-like postcranial material from the earliest Middle Triassic (early Anisian) Röt Formation of Waldhaus, southwestern Germany. Finally, we review the spatial and temporal distribution of the earliest archosaur fossils and their implications for understanding the dynamics of the archosaur radiation.

Conclusions/significance: Comprehensive numerical phylogenetic analyses demonstrate that both Ctenosauriscus and the Waldhaus taxon are members of a monophyletic grouping of poposauroid archosaurs, Ctenosauriscidae, characterised by greatly elongated neural spines in the posterior cervical to anterior caudal vertebrae. The earliest archosaurs, including Ctenosauriscus, appear in the body fossil record just prior to the Olenekian/Anisian boundary (c. 248 Ma), less than 5 million years after the Permian-Triassic mass extinction. These earliest archosaur assemblages are dominated by ctenosauriscids, which were broadly distributed across northern Pangea and which appear to have been the first global radiation of archosaurs.

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Stratigraphic and geographical data for German ctenosauriscid specimens.Stratigraphy of the German Buntsandstein (left), showing the stratigraphic levels at which Ctenosauriscus and the Waldshut ctenosauriscid were collected. Map of Germany (right) showing Triassic outcrops and the Bremketal and Waldshut localities.
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pone-0025693-g001: Stratigraphic and geographical data for German ctenosauriscid specimens.Stratigraphy of the German Buntsandstein (left), showing the stratigraphic levels at which Ctenosauriscus and the Waldshut ctenosauriscid were collected. Map of Germany (right) showing Triassic outcrops and the Bremketal and Waldshut localities.

Mentions: The holotype specimen (GZG.V.4191) of Ctenosauriscus koeneni was discovered early in 1871 in a quarry at Bremketal ( =  “Bremke dell”) near Göttingen (Fig. 1), northern Germany, and later (November 1871) donated by master builder and architect Eduard Freise (1816–1885) to the University of Göttingen. The German palaeontologist Friedrich von Huene erected a new genus and species, Ctenosaurus koeneni, for the specimen in 1902 based upon examination of a photograph sent to him by Adolf von Koenen (1837–1915), professor of geology and palaeontology at the University of Göttingen. Huene [29] provided a more extensive description based upon direct examination of the specimen and additional preparation (Fig. 2A–C). Huene [29], [33] suggested that two individuals were represented by the holotype slabs (one individual represented by the slab and counterpart referred to below as slabs A1 and A2, and one represented by the slabs B1 and B2), and considered Ctenosaurus to represent a pelycosaurian-grade synapsid on the basis of its elongate neural spines. Abel [34] questioned the pelycosaurian affinities and considered C. koeneni to represent a temnospondyl similar to the sail-backed Platyhystrix (cf. [35]). Because the genus name Ctenosaurus was preoccupied, Kuhn [36] erected the replacement name Ctenosauriscus.


The sail-backed reptile Ctenosauriscus from the latest Early Triassic of Germany and the timing and biogeography of the early archosaur radiation.

Butler RJ, Brusatte SL, Reich M, Nesbitt SJ, Schoch RR, Hornung JJ - PLoS ONE (2011)

Stratigraphic and geographical data for German ctenosauriscid specimens.Stratigraphy of the German Buntsandstein (left), showing the stratigraphic levels at which Ctenosauriscus and the Waldshut ctenosauriscid were collected. Map of Germany (right) showing Triassic outcrops and the Bremketal and Waldshut localities.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3194824&req=5

pone-0025693-g001: Stratigraphic and geographical data for German ctenosauriscid specimens.Stratigraphy of the German Buntsandstein (left), showing the stratigraphic levels at which Ctenosauriscus and the Waldshut ctenosauriscid were collected. Map of Germany (right) showing Triassic outcrops and the Bremketal and Waldshut localities.
Mentions: The holotype specimen (GZG.V.4191) of Ctenosauriscus koeneni was discovered early in 1871 in a quarry at Bremketal ( =  “Bremke dell”) near Göttingen (Fig. 1), northern Germany, and later (November 1871) donated by master builder and architect Eduard Freise (1816–1885) to the University of Göttingen. The German palaeontologist Friedrich von Huene erected a new genus and species, Ctenosaurus koeneni, for the specimen in 1902 based upon examination of a photograph sent to him by Adolf von Koenen (1837–1915), professor of geology and palaeontology at the University of Göttingen. Huene [29] provided a more extensive description based upon direct examination of the specimen and additional preparation (Fig. 2A–C). Huene [29], [33] suggested that two individuals were represented by the holotype slabs (one individual represented by the slab and counterpart referred to below as slabs A1 and A2, and one represented by the slabs B1 and B2), and considered Ctenosaurus to represent a pelycosaurian-grade synapsid on the basis of its elongate neural spines. Abel [34] questioned the pelycosaurian affinities and considered C. koeneni to represent a temnospondyl similar to the sail-backed Platyhystrix (cf. [35]). Because the genus name Ctenosaurus was preoccupied, Kuhn [36] erected the replacement name Ctenosauriscus.

Bottom Line: In addition, we describe Ctenosauriscus-like postcranial material from the earliest Middle Triassic (early Anisian) Röt Formation of Waldhaus, southwestern Germany.Comprehensive numerical phylogenetic analyses demonstrate that both Ctenosauriscus and the Waldhaus taxon are members of a monophyletic grouping of poposauroid archosaurs, Ctenosauriscidae, characterised by greatly elongated neural spines in the posterior cervical to anterior caudal vertebrae.The earliest archosaurs, including Ctenosauriscus, appear in the body fossil record just prior to the Olenekian/Anisian boundary (c. 248 Ma), less than 5 million years after the Permian-Triassic mass extinction.

View Article: PubMed Central - PubMed

Affiliation: Bayerische Staatssammlung für Paläontologie und Geologie, München, Germany. r.butler@lrz.uni-muenchen.de

ABSTRACT

Background: Archosaurs (birds, crocodilians and their extinct relatives including dinosaurs) dominated Mesozoic continental ecosystems from the Late Triassic onwards, and still form a major component of modern ecosystems (>10,000 species). The earliest diverse archosaur faunal assemblages are known from the Middle Triassic (c. 244 Ma), implying that the archosaur radiation began in the Early Triassic (252.3-247.2 Ma). Understanding of this radiation is currently limited by the poor early fossil record of the group in terms of skeletal remains.

Methodology/principal findings: We redescribe the anatomy and stratigraphic position of the type specimen of Ctenosauriscus koeneni (Huene), a sail-backed reptile from the Early Triassic (late Olenekian) Solling Formation of northern Germany that potentially represents the oldest known archosaur. We critically discuss previous biomechanical work on the 'sail' of Ctenosauriscus, which is formed by a series of elongated neural spines. In addition, we describe Ctenosauriscus-like postcranial material from the earliest Middle Triassic (early Anisian) Röt Formation of Waldhaus, southwestern Germany. Finally, we review the spatial and temporal distribution of the earliest archosaur fossils and their implications for understanding the dynamics of the archosaur radiation.

Conclusions/significance: Comprehensive numerical phylogenetic analyses demonstrate that both Ctenosauriscus and the Waldhaus taxon are members of a monophyletic grouping of poposauroid archosaurs, Ctenosauriscidae, characterised by greatly elongated neural spines in the posterior cervical to anterior caudal vertebrae. The earliest archosaurs, including Ctenosauriscus, appear in the body fossil record just prior to the Olenekian/Anisian boundary (c. 248 Ma), less than 5 million years after the Permian-Triassic mass extinction. These earliest archosaur assemblages are dominated by ctenosauriscids, which were broadly distributed across northern Pangea and which appear to have been the first global radiation of archosaurs.

Show MeSH