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Article: Post-embryonic development of Fritzolenellus suggests the ancestral morphology of the early developmental stages in Trilobita

Papers in Palaeontology - Volume 7 Issue 1 - Cover
Publication: Papers in Palaeontology
Volume: 7
Part: 2
Publication Date: May 2021
Page(s): 839 859
Author(s): Lukáš Laibl, Jörg Maletz, and Pascal Olschewski
DOI: 10.1002/spp2.1324
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How to Cite

LAIBL, L., MALETZ, J., OLSCHEWSKI, P. 2021. . Papers in Palaeontology, 7, 2, 839-859. DOI: /doi/10.1002/spp2.1324

Author Information

  • Lukáš Laibl - Institute of Earth Sciences, Géopolis University of Lausanne CH-1015 Lausanne Switzerland
  • Lukáš Laibl - Czech Academy of Sciences Institute of Geology Rozvojová 269 165 00 Prague 6 Czechia
  • Lukáš Laibl - Institute of Geology & Palaeontology Faculty of Science Charles University Albertov 6 Prague 12843 Czechia
  • Jörg Maletz - Department of Geological Sciences Freie Universität Berlin Malteserstrasse 74-100 D-12249 Berlin Germany
  • Pascal Olschewski - Department of Geological Sciences Freie Universität Berlin Malteserstrasse 74-100 D-12249 Berlin Germany

Publication History

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    Trilobite development has been intensively explored during the past decades, but information on ancestral character combinations in the early developmental stages of trilobites remains unknown. Trilobites of the superfamily Olenelloidea are one of the earliest diverging groups. Study of their development coupled with the development of other early diverging trilobite groups can provide information on the ancestral morphology of trilobite early stages. Herein we describe numerous well-preserved specimens of the olenelloid trilobite Fritzolenellus lapworthi. The earliest stages have circular cephala bearing intergenal spines and lacking genal spines. During subsequent development, morphological changes involve the modification of the cephalic shape from circular to semicircular, expansion of the frontal glabellar lobe, gradual shortening of intergenal spines and origin and prolongation of genal spines. Trunk development of Fritzolenellus suggests that macropleurae and macrospine development are two independent processes and that the origin of the opisthotrunk is linked with the onset of phase 5 of cephalic development. The morphology of the early developmental stages of Fritzolenellus and of some related taxa differs in many aspects from the morphology of equivalent stages of some other members of Olenelloidea. Consequently, two basic morphotypes are recognized during the early development of Olenelloidea: the Fritzolenellus and the Olenellus morphotypes. Comparison with Fallotaspidoidea and Redlichiina indicates that early developmental stages of these taxa share character combinations that are typical for the Fritzolenellus morphotype. Such a comparison suggests that characters defining the Fritzolenellus morphotype are ancestral for Trilobita. The Olenellus morphotype is probably a derived condition within Olenelloidea and might be related to predator deterrence.

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