Search results for "Devonian"
showing 7 items of 77 documents
New Lower Devonian Polygnathids (Conodonta) from the Spanish Central Pyrenees, with comments on the early radiation of the group
2014
The comprehensive study of six Pragian-lower Emsian (Lower Devonian) sections from the Spanish Central Pyrenees has yielded a rich assemblage of conodont faunas, highlighting an important succession of Polygnathus species. Among them, the presence of the biostratigraphical markers P. pireneae , P. kitabicus, P. excavatus excavatus and P. exc. 114 stands out. This conodont succession allows the identification of the Pragian/Emsian boundary and the early Emsian zones and subzones: the kitabicus Zone and the Lower and Middle excavatus subzones. It is also remarkable the presence of three new polygnathid species: P. aragonensis n. sp., P. carlsi n. sp. and P. ramoni n. sp. Additionally, P. pan…
The reconstruction of easterly wind directions for the Eifel region (Central Europe) during the period 40.3–12.9 ka BP
2010
Abstract. A high resolution continuous reconstruction of last glacial wind directions is based on provenance analysis of eolian sediments in a sediment core from the Dehner dry Maar in the Eifel region (Germany). This Maar is suitable to archive easterly wind directions due to its location west of the Devonian carbonate basins of the Eifel-North-South-Zone. Thus, eolian sediments with high clastic carbonate content can be interpreted as an east wind signal. The detection of such east wind sediments is applied by a new module of the RADIUS grain size analyze technique. The investigated time period from 40.3–12.9 ka BP can be subclassified in three units: The first unit covers the periods of …
First record of conulariids from the Tērvete Formation, Upper Devonian of Latvia
2020
Phosphatized remains belonging to conulariids have been found in the Middle Famennian (Upper Devonian) deposits of the TÄrvete Formation of Latvia for the first time. The ornamentation pattern and characteristics of the exoskeleton indicate that the conulariids, represented by two incomplete and flattened specimens, belong to a single species within the genus Paraconularia. Paraconularia sp. from the TÄrvete Formation differs from Conularia latviensis Delle from the JoniÅ¡kis Formation in size and details of the morphology of the periderm; however, most probably, the species C. latviensis also belongs to the genus Paraconularia. Finding well-preserved almost complete conulariids agrees with…
Vascular structure of the earliest shark teeth
2018
Here we use synchrotron tomography to characterise dental vasculature in the oldest known tooth-bearing sharks, Leonodus carlsi Mader, 1986 and Celtiberina maderi Wang, 1993. Three dimensional reconstruction of the vascular system and microstructure of both taxa revealed a complex and dense network of canals, including horizontal, ascending and secondary bifurcated canals, as well as histological features consistent with an osteodont histotype. However, L. carlsi and C. maderi also exhibit significant morphological differences, showing Leonodus a typical diplodont tooth morphology with a linguo-labially elongated base, that contrast with Celtiberina’s teeth that show a single conical cusp c…
Chondrichthyan microremains from the Givetian of the Aragonian Pyrenees (Spain)
2007
Keywords .-L owervarcus Zone, Middle varcus Zone, Teeth, Scales, Squamation pattern, Phoebodus fastigatus. Abstract .-AL ower andbasal Middle varcus Zone (Givetian, Middle Devonian) vertebrate association consisting of chondrichtyan teeth and scales of the genus Phoebodus is documented for the first time from the Aragonian Pyrenees of Spain. This record suggests that different teeth morphologies that were previously treated as separate taxa could be grouped in Phoebodus fastigatus. Moreover, the teeth and scales association is in agreement with the previously recons- tructed squamation pattern of this taxon.
Tooth replacement rates in early chondrichthyans: a qualitative approach
2009
The continuous replacement of teeth throughout their lifetime is a common characteristic of most chondrichthyans. This process was already present in the earliest representatives of the group. It has been well established that different species of extant sharks show rapid tooth replacement rates; however, some authors have suggested that in early chondrichthyans this rate might have been much slower. Here we present a qualitative approach to analyse tooth replacement rates in the Early Devonian shark Leonodus carlsi, the earliest tooth-bearing shark known to date. For this, we have examined 1,103 isolated teeth from Celtiberia, Spain. Our study provides strong evidences of an extremely slow…
Enameloid microstructure in the oldest known chondrichthyan teeth
2009
Botella, H., Donoghue, P.C.J and Martinez-Perez, C. 2009. The enameloid microstructure of the oldest known chondrichthyan teeth. — Acta Zoologica (Stockholm) 90 (Suppl. 1): 103‐108 Previous studies on tooth enameloid microstructure in several chondrichthyan taxa spanning the phylogeny of the group provided support for the homology of chondrichthyan tooth enameloid. This hypothesis requires that a single crystallite enameloid (SCE) monolayer must be present in the teeth of the most primitive chondrichthyan. However, the dental microstructure of the earliest sharks has yet to be investigated. We have studied the tooth enameloid microstructure of the two oldest tooth-bearing shark species curr…