Endoskeleton three phyla and one subclass of animals, endoskeletons of various complexity are found: Chordata, Echinodermata, Porifera, and Coleoidea. An endoskeleton may function purely for support (as in the case of sponges), but often serves as an attachment site for muscle and a mechanism for transmitting muscular forces. A true endoskeleton is derived from mesodermal tissue. Such a skeleton is present in echinoderms and chordates. The poriferan 'skeleton' consists of microscopic calcareous or siliceous spicules or a spongin network. The Coleoidae do not have a true endoskeleton in the evolutionary sense; there, a mollusk exoskeleton evolved into several sorts of internal
Branching order of bacterial phyla (Ciccarelli et al., 2006) is not monophyletic in this phylogram, but this may be erroneous given the large amount of literature in favour of basal Acidobacteria. Contrary to 16S trees, the deepest branching clade is the Firmicutes. Nevertheless, the last common ancestor was between Bacteria and Archaea+Eukarya. Branching order of bacterial phyla (Ciccarelli et al., 2006) There are several models of the Branching order of bacterial phyla, one of these was proposed in 2006 by Ciccarelli "et al." for their iTOL project. This tree is based on a concatenated set of conserved protein and not 16S rRNA (cf. Branching order of bacterial phyla (Woese,