Degrees of sclerotization in lobopodous and stenopodous limbs of fossil lobopodians and arthropods.

<p><b>A.</b><i>Surusicaris elegans</i> gen. et sp. nov., holotype (ROM 62976), showing the three right anterior uniramous limbs with faint traces of cuticular boundaries. <b>B.</b> Limbs of <i>Diania cactiformis</i> Liu et al., counterpart of YKLP 11319 (from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124979#pone.0124979.ref079" target="_blank">79</a>]). Note the thickness and regularity of the subdivisions. <b>C.</b><i>Aysheaia pedunculata</i> Walcott, part of holotype (USNM 57655), posterior limbs preserved at various angles. The aspect of the annulations varies from discordant through faint to regular. <b>D.</b><i>Hadranax augustus</i> Budd and Peel [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124979#pone.0124979.ref126" target="_blank">126</a>], trunk lobopods of the mid-section of holotype (MGUH 24.527). <b>E.</b> Posterior endopod of the bivalved arthropod <i>Odaraia alata</i> Walcott. Poor sclerotization can lead to a deformed preservation of segments’ shape, but the rectangular aspect of some segments and the general elongated habitus usually remain characteristic of arthrodization. <b>F.</b> Anterior limb of <i>Canadaspis perfecta</i> preserved twisted and dislocated. In certain cases, taphonomy can reshape an arthrodized limb to a much more compact structure, although the undulation or folding of segments’ boundaries are not necessarily associated with such deformations. <b>G.</b> The “poorly sclerotized” anterior endopods of the fuxianhuiid <i>Chengjiangocaris kunmingensis</i> Yang et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124979#pone.0124979.ref014" target="_blank">14</a>] (YKLP 12024). Note their relatively advanced arthrodization in comparison to <i>Surusicaris</i>. Abbr. al<i>x</i>: anterior limb (1–3). Scale numbers in mm.