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Biodiversity of the Silurian osteostracans of the East Baltic

Published online by Cambridge University Press:  23 February 2015

T. Märss ,
O. Afanassieva  and
H. Blom
T. Märss
Affiliation:
Institute of Geology at Tallinn University of Technology, Ehitajate Road 5, 19086 Tallinn, Estonia. Email: Tiiu.Marss@ttu.ee
O. Afanassieva
Affiliation:
Borissiak Paleontological Institute, Russian Academy of Sciences, Profsoyuznaya 123, Moscow 117997, Russia. Email: oafan@paleo.ru
H. Blom*
Affiliation:
Subdepartment of Evolution and Development, Department of Organismal Biology, Uppsala University, Norbyvägen 18A, SE-752 36 Uppsala, Sweden. Email: Henning.Blom@ebc.uu.se
*
*corresponding author
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Abstract

The sculpture and histology of osteostracan head shields and trunk squamations from the Silurian of Estonia are described, illustrated and used for the identification of disarticulated microremains collected from outcrop sections and numerous drill cores in Estonia and Latvia over the last 40 years. The scattered osteostracan material contains thousands of specimens of scales and shield fragments. The sculpture and histology of species of the previously identified eight genera in the region (Tremataspis, Dartmuthia, Saaremaaspis, Oeselaspis, Aestiaspis, Thyestes, Procephalaspis, Witaaspis) are redescribed, together with Ateleaspis, found in Estonia for the first time. The sculpture on the cornua of several taxa is described for the first time. The new taxa Tremataspis perforata sp. nov., Dartmuthia procera sp. nov., Eldaaspis miklii gen. et sp. nov., Tahulaspis ordinata gen. et sp. nov., Tahulaspis praevia gen. et sp. nov., Meelaidaspis gennadii gen. et sp. nov. and Ohesaareaspis ponticulata gen. et sp. nov. are established, based upon sculpture and histological characteristics of the exoskeleton. The supraoral field with denticles of that field are described for the first time in Oeselaspis pustulata, as is the supraoral plate with buccal denticles in Meelaidaspis gennadii gen. et sp. nov. Thin sections of all taxa (except of Witaaspis) have been studied. This work sheds light on East Baltic osteostracan biodiversity from the Maasi Beds of the Jaagarahu Stage, Sheinwoodian, lower Wenlock up to the Ohesaare Stage, upper Přidoli, Silurian.

Keywords

“Agnatha”EstoniaexoskeletonsLatviamicroremainsOsteostraci
Type
Articles
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 105 , Issue 2 , June 2014 , pp. 73 - 148
Copyright
Copyright © The Royal Society of Edinburgh 2015 

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