English: Cladogram showing the assumed relationships and known temporal distribution of the genera Bienvillia, Porterfieldia and Triarthrus, family Olenidae. Based on Ludvigsen, R.; Tuffnell, P.A. (1983). "A revision of the Ordovician olenid trilobite Triarthrus". Geological Magazine 120 (6): 570, figure 3.
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