Gross morphology and microstructure of type locality ossicles of Psephophorus polygonus Meyer, 1847 (Testudines, Dermochelyidae)

Delfino, Massimo, Scheyer, Torsten M., Chesi, Francesco, Fletcher, Tamara, Gemel, Richard, MacDonald, Stewart, Rabi, Márton and Salisbury, Steven W. (2013) Gross morphology and microstructure of type locality ossicles of Psephophorus polygonus Meyer, 1847 (Testudines, Dermochelyidae). Geological Magazine, 150 5: 767-782. doi:10.1017/S001675681200091X


Author Delfino, Massimo
Scheyer, Torsten M.
Chesi, Francesco
Fletcher, Tamara
Gemel, Richard
MacDonald, Stewart
Rabi, Márton
Salisbury, Steven W.
Title Gross morphology and microstructure of type locality ossicles of Psephophorus polygonus Meyer, 1847 (Testudines, Dermochelyidae)
Formatted title
Gross morphology and microstructure of type locality ossicles of Psephophorus polygonus Meyer, 1847 (Testudines, Dermochelyidae)
Journal name Geological Magazine   Check publisher's open access policy
ISSN 0016-7568
1469-5081
Publication date 2013-09
Sub-type Article (original research)
DOI 10.1017/S001675681200091X
Volume 150
Issue 5
Start page 767
End page 782
Total pages 16
Place of publication Cambridge, United Kingdom
Publisher Cambridge University Press
Collection year 2014
Language eng
Formatted abstract
Psephophorus polygonus Meyer, 1847, the first fossil leatherback turtle to be named, was described on the basis of shell ossicles from the middle Miocene (MN6–7/8?) of Slovakia. The whereabouts of this material is uncertain but a slab on display at the Naturhistorisches Museum Wien is considered the neotype. We rediscovered further type locality ossicles in four European institutions, re-evaluated their gross morphology and described for the first time their microstructure by comparing them with Dermochelys coriacea, the only living dermochelyid turtle. The gross morphology is congruent with that already described for P. polygonus, but with two significant exceptions: the ridged ossicles of P. polygonus may have a distinctly concave ventral surface as well as a tectiform shape in cross-section. They do not develop the external keel typical of many ossicles of D. coriacea. Both ridged and non-ridged ossicles of P. polygonus are characterized by compact diploe structures with an internal cortex consisting of a coarse fibrous meshwork, whereas the proportionately thinner ossicles of D. coriacea tend to lose the internal cortex, and thus their diploe, during ontogeny. The ossicles of both P. polygonus and D. coriacea differ from those of other lineages of amniotes whose carapace is composed of polygonal ossicles or platelets, in having growth centres situated at the plate centres just interior to the external bone surface and not within the cancellous core or closer to the internal compact layer. The new diagnosis of P. polygonus allows us to preliminarily re-evaluate the taxonomy of some of the Psephophorus-like species. Despite some macro- and micromorphological differences, it seems likely that Psephophorus was as cosmopolitan as extant Dermochelys and had a broadly similar ecology, with a possible difference concerning the dive depth.
Keyword Dermochelys coriacea
Bone histology
Middle Miocene
Palaeoecology
Petrographic thin-sections
Taxonomy
Dermal armor
Turtles
Histology
Miocene
Coriacea
Slovakia
Eocene
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2014 Collection
School of Biological Sciences Publications
 
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