Cyrtometopinid trilobites from the upper Volkhov and lower Lynna Formation(lower Darriwilian) of NW Russia

TY - JOUR

T1 - Cyrtometopinid trilobites from the upper Volkhov and lower Lynna Formation(lower Darriwilian) of NW Russia

AU - Hansen, Thomas

PY - 2009

Y1 - 2009

N2 - Two cyrtometopinid trilobite taxa from the lower Darriwilian of NW Russia are examined. A new species of the genus Krattaspis is described, extending the stratigraphical range of the genus into the lower Darriwilian (Middle Ordovician). K. paraspinosis n.sp. is the youngest representative of the genus, but is closest to forms assigned to Cyrtometopus and confirms the derivation of Cyrtometopus from Krattaspis. Ontogenetic studies of K. paraspinosis n.sp. and Cyrtometopus clavifrons Angelin, 1854, from the same beds indicates a forward displacement of the eyes with increasing size, which may be contrary to all other known members of the family Cheiruridae.

AB - Two cyrtometopinid trilobite taxa from the lower Darriwilian of NW Russia are examined. A new species of the genus Krattaspis is described, extending the stratigraphical range of the genus into the lower Darriwilian (Middle Ordovician). K. paraspinosis n.sp. is the youngest representative of the genus, but is closest to forms assigned to Cyrtometopus and confirms the derivation of Cyrtometopus from Krattaspis. Ontogenetic studies of K. paraspinosis n.sp. and Cyrtometopus clavifrons Angelin, 1854, from the same beds indicates a forward displacement of the eyes with increasing size, which may be contrary to all other known members of the family Cheiruridae.

M3 - Journal article

SN - 0011-6297

VL - 58

SP - 1

EP - 13

JO - Bulletin of the Geological Society of Denmark

JF - Bulletin of the Geological Society of Denmark

ER -