Sexual dimorphism within the stem-group arthropod Isoxys volucrisfrom the Sirius Passet Lagerstätte, North Greenland
Nielsen, M.L., Rasmussen, J.A. & Harper, D.A.T. 2017. Sexual dimorphism within the stem-group arthropod Isoxys volucrisfrom the Sirius Passet Lagerstätte, North Greenland. © 2017 by Bulletin of the Geological Society of Denmark, Vol. 65, pp. 47–58. ISSN 2245-7070. (www.2dgf.dk/publikationer/bulletin).
Abstract:
Morphometric analyses carried out on 126 specimens of the early Cambrian (Cambrian Series 2, Stage 3) stem-group arthropod Isoxys volucris from North Greenland reveal a bimodal distribution, where Morphogroup A is characterised by a significantly wider doublure than Morphogroup B. The dimorphism is interpreted as intraspecific variation related to gender (sexual dimorphism), where the relative numbers of individuals within the two morphogroups are equal (ratio 1:1). The discovery of established sexual dimorphism in Isoxys may have implications for the taxonomic discrimination of other stemgroup arthropods within the morphologically diverse and disparate animals of the early Cambrian.
Keywords: Sirius Passet Lagerstätte, Isoxys, stem-group arthropods, sexual dimorphism, early Cambrian.
Addresses:
Morten Lunde Nielsen, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5–7, DK-1350 Copenhagen K, Denmark.
Jan Audun Rasmussen, Fossil and Mo-clay Museum, Museum Mors, Skarrehagevej 8, DK-7900 Nykøbing Mors, Denmark.
David A.T. Harper, Department of Earth Sciences, Palaeoecosystems Group, Durham University, Stockton Road, Durham DH1 3LE, United Kingdom; also Department of Geology, Lund University, Sölvegatan 12, S-223 62 Lund, Sweden.
Corresponding author: Jan Audun Rasmussen
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