Humble origins for a successful strategy: complete enrolment in early Cambrian olenellid trilobites |
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Authors: | Javier Ortega-Hernández Jorge Esteve Nicholas J Butterfield |
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Institution: | 1.Department of Earth Sciences, University of Cambridge, Downing Site, Cambridge CB2 3EQ, UK;2.Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, People''s Republic of China |
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Abstract: | Trilobites are typified by the behavioural and morphological ability to enrol their bodies, most probably as a defence mechanism against adverse environmental conditions or predators. Although most trilobites could enrol at least partially, there is uncertainty about whether olenellids—among the most phylogenetically and stratigraphically basal representatives—could perform this behaviour because of their poorly caudalized trunk and scarcity of coaptative devices. Here, we report complete—but not encapsulating—enrolment for the olenellid genus Mummaspis from the early Cambrian Mural Formation in Alberta, the earliest direct evidence of this strategy in the fossil record of polymerid trilobites. Complete enrolment in olenellids was achieved through a combination of ancestral morphological features, and thus provides new information on the character polarity associated with this key trilobite adaptation. |
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Keywords: | Mummaspis Mural formation Lower Dyeran functional morphology |
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