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Fig. 6 | BMC Evolutionary Biology

Fig. 6

From: Mandibulate convergence in an armoured Cambrian stem chelicerate

Fig. 6

Segmental composition of major panarthropod groups as expressed through the mean of numbers of podomere (left), head limbs (center) and trunk somites (right). We use logarithmic instead of raw values to facilitate reading. Upper graphs have their error bars representing the standard deviation of the data; the error bars for lower graphs represent the minimal and maximal values inside each group. Note the punctual effect of the evolution of habeliidan heads (blue arrows) compared to the trend observed for the trunk. Tentatively, we have considered the first maxilliped in certain mandibulates as part of the functional “head,” owing to its high morphological integration to that tagma. Trilobites are not included here, their high plasticity in trunk somite number being considered autapomorphic and an arguable deviation from the general pattern seen in other artiopodans. The topology is based on phylogenetic results presented herein (Fig. 5). Double branches indicate paraphyletic groups

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