The ontogeny of Ellipsocephalus (Trilobita) and systematic position of Ellipsocephalidae

Abstract

Laibl, L., Fatka, O., Budil, P., Ahlberg, P., Szabad, M., Vokáč, V. & Kozák, V., 24.3.2015. The ontogeny of Ellipsocephalus (Trilobita) and systematic position of Ellipsocephalidae. Alcheringa 39, 477–487. ISSN 0311-5518.Well-preserved early holaspid stages of the Cambrian Series 3 trilobites Ellipsocephalus hoffi (Schlotheim, 1823) and Ellipsocephalus polytomus Linnarsson, 1877 have been discovered in the Příbram-Jince Basin (Czech Republic) and Jämtland (Sweden), respectively. Both species show remarkable morphological changes during late ontogeny. The earliest holaspides share long genal spines, and long macrospines on the second thoracic segment. Whereas macrospines disappear abruptly in later stages, genal spines are progressively shortened. Consequently, the ontogeny of trilobites of Ellipsocephalidae is revised. The morphology of early meraspid cranidia and ontogenetic patterns in the disappearance of macrospines suggest that this family is closely related to members of Redlichiida rather than Ptychopariida.Lukáš Laibl [lukaslaibl@gmail.com] and Oldřich Fatka [fatka@natur.cuni.cz], Charles University, Institute of Geology and Palaeontology, Albertov 6, 128 43, Prague 2, Czech Republic; Petr Budil [petr.budil@geology.cz], Czech Geological Survey, Klárov 3, Prague 1, 118 21, Czech Republic; Per Ahlberg [per.ahlberg@geol.lu.se], Department of Geology, Lund University, Sölvegatan 12, SE-223 62 Lund, Sweden; Michal Szabad [geosz.pb@seznam.cz], Obránců míru 75, 261 02 Příbram VII, Czech Republic; Václav Vokáč [lichas@seznam.cz], Ke Kukačce 21, 312 00 Pilsen, Czech Republic; Vladislav Kozák [vlada.kozak@tiscali.cz], K Moravině 11/1689, 190 00 Prague 9, Czech Republic.