New coelacanth material from the Middle Triassic of eastern Switzerland, and comments on the taxic diversity of actinist
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New coelacanth material from the Middle Triassic of eastern Switzerland, and comments on the taxic diversity of actinistans Lionel Cavin • Heinz Furrer • Christian Obrist
Received: 1 February 2013 / Accepted: 9 August 2013 / Published online: 16 November 2013 Ó Swiss Geological Society 2013
Abstract New coelacanth material from the Middle Triassic Prosanto Formation of the Ducan and Landwasser area near Davos in eastern Switzerland, Canton Graubu¨nden, is described. A sub-complete individual is visible in ventral view, and shows details of its branchial apparatus. In particular, it possesses relatively large teeth on the ceratobranchials, and possible ossified hypobranchials. Few diagnostic characters are observable, and most of them are visible on the mandibles preserved in lateral view. This specimen shares characters with Ticinepomis peyeri, a smaller form from the Middle Triassic of Monte San Giorgio, whose holotype is re-described in part here. A second specimen, a fragmentary caudal skeleton shows the typical supplementary lobe of coelacanths, and meristic characters indicating probable close affinities with T. peyeri. We refer this material to Ticinepomis cf. T. peyeri. Because the new specimen is larger than the holotype, we refute the possible juvenile status of the small specimen from Monte San Giorgio. The new material of Ticinepomis from Canton Graubu¨nden shows anatomical features not Editorial handling: D. Marty.
Electronic supplementary material The online version of this article (doi:10.1007/s00015-013-0143-7) contains supplementary material, which is available to authorized users. L. Cavin (&) Department of Geology and Palaeontology, Muse´um d’Histoire Naturelle, CP6434, 1211 Geneva 6, Switzerland e-mail: [email protected] H. Furrer Pala¨ontologisches Institut und Museum der Universita¨t Zu¨rich, Karl Schmid-Strasse 4, 8006 Zurich, Switzerland C. Obrist Erliackerweg 8, 4462 Rickenbach, BL, Switzerland
preserved on the holotype and allows the addition of new characters to a previously published data matrix of actinistians. A phylogenetic analysis is performed, which supports that Ticinepomis is nested among the Latimeriidae. The diversity of post-Palaeozoic coelacanths is assessed. The taxic diversity of observed occurrences shows a peak in the Early Triassic and a peak in the Late Jurassic, as detected in previous studies. When ghost lineages are included in the computation, the Late Jurassic peak is smoothened. By comparing the taxic diversity curves with the curve of average ghost lineage duration, we conclude that the Early Triassic peak of diversity was probably caused by a biological radiation, whereas the Late Jurassic peak of observed diversity is probably the result of a Lagersta¨tten effect. Keywords Prosanto Formation Ladinian Phylogeny Taxic diversity Branchial apparatus Institutional and anatomical abbreviations PIMUZ Collection of the Palaeontological Institute and Museum, University of Zu¨rich Ang Angular a.Pa Anterior parietal Apal Autopalatine Art Articular art.fa A
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