Pro-ostraca of Triassic belemnoids (Cephalopoda) from Northern Calcareous Alps, with observations on their mode of preservation in an environment of northern Tethys which allowed for carbonization of non-biomineralized structures.
2012 (Engelska)Ingår i: N. Jb. Geol. Paläont. Abh., Vol. 266, nr 1, s. 31-38Artikel i tidskrift (Refereegranskat) Published
Abstract [en]
A pro-ostracum – the anterior dorsal plate subdivided into three longitudinal fields – is
developed in Triassic phragmoteuthids (Phragmoteuthis, Breviconoteuthis) and the belemnotheutid? (Lunzoteuthis) but is missing in aulacocerids which have a pro-ostracum-like structure – the dorsal apertural crest with arched growth lines. Two types of pro-ostraca: a Phragmoteuthis-type, characterized by arched growth lines in each field, and a Lunzoteuthis-type, in which the median field has arched growth lines and lateral fields bear converging longitudinal ridges, are distinguished. The pro-ostracum with the ridged lateral fields evidently obtained further rapid development; in the Sinemurian belemnite Nannobelus the ridged lateral fields are already formed by the longitudinally exposed narrow portions of succeeding, overlapping sublayers of the pro-ostracum. This structure apparently enabled efficient mantle/shell linkage that facilitated effective manoeuvring, an active mode of life and global radiation of Jurassic belemnites. Exceptional, large scale, preservation of pro-ostraca in lower Carnian of Schindelberg, Lower Austria, and Raibl, North Italy, was possibly due to the concurrency of (1) an environment of the northern Tethys that allowed for post-mortem carbon substitution of chitin and other non-biomineralized material, such as ink and mantle tissue, and (2) the inorganic-organic composition of pro-ostracum as indicated by micro-laminations typical of chitin-containing material and characterized by alteration of chitinous and carbonate laminas similar to those in cuttlebones of Recent Sepia.
Ort, förlag, år, upplaga, sidor
Stuttgart, 2012. Vol. 266, nr 1, s. 31-38
Nyckelord [en]
Pro-ostracum, pro-ostracum-like structure, coleoids, chitin fossilization, carbonization, Late Triassic, Alps
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Identifikatorer
URN: urn:nbn:se:nrm:diva-1362DOI: DOI: 10.1127/0077-7749/2012/0266OAI: oai:DiVA.org:nrm-1362DiVA, id: diva2:862528
Projekt
evolutionary shell morphology and ultrustructure as a key to coleoid cephalopod phylogeny2015-10-222015-10-222015-11-26Bibliografiskt granskad