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"THE VESTIGIAL COCCYX a remnant of a now-missing tail, shows how developmental remnants reflect evolutionary history, revealing the complex association that leads to such structures being expressed (or not), which is itself an informative aspect of organismal history." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn

COMPOUND CLUES. "Sometimes a feature’s function (if it ever had one) can be lost or shifted, but compound clues together reveal the intertwined relationship between a lineage’s phylogeny and ontogeny." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn

HOLDOVER NAVEL. "Perhaps the most conspicuous ontogenetic leftover is found on the abdomen of all placental mammals: the umbilicus (navel or ‘belly button’). Strictly speaking this is a scar: although the umbilical cord has a function, the umbilicus itself never had one, making this a nonfunctional embryonic holdover, unlike the formerly functional circulatory and urogenital remains." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn

POSTNATAL TAILS. "All chordates possess, again at some stage of the life cycle, a postanal tail. Because the tail is retained in many ‘adult’ (i.e., sexually mature) chordates—and in nearly all adult vertebrates, with the major exception of apes and frogs—this can often be viewed as a true evolutionary vestige when the tail is partly or wholly non-functional in adults." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn

VESTIGIAL BONES. "Examples include cranial and other bony sutures that reveal formerly distinct ossification centers. During formation of endochondral (cartilage replacement) long bones, a growth zone forms between the bony shaft (diaphysis) and end plate (epiphysis). These elements eventually fuse when growth ends, leaving a tell-tale epiphyseal line where elements were formerly separated. This too is an artifact of ontogeny." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn

TRANSFORMATIONS. "The endostyle—another of the six diagnostic chordate features—is known (from its metabolic and iodine-concentrating activities) to be homologous to the thyroid gland. This represents another relic of shared ontogenetic and phylogenetic transformations." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn

"BILATERALLY SYMMETRIC embryos of echinoderms, which as adults display pentamerous radial symmetry, likewise are relics that disclose secrets of echinoderm origins. Even the possession of a head region at one end (rather than in the center) of cephalized animals is a form of historical remain: still obviously functional yet a reminder of the past, when heads first arose." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn

REMNANTS. "Consider the six basic ‘diagnostic’ features of the Phylum Chordata, found in all chordates (and only chordates) at some point in their life cycle: the notochord; single, dorsal, hollow neural tube; myomeres (segmental muscle units); postanal tail; pharyngeal slits; and endostyle. In short, it is not possible to disconnect ontogenetic from phylogenetic remnants in this instance. Homologies of these jointly conserved evolutionary-developmental structures constitute another type of historical residues." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn

DEFAULT NIPPLES. "Darwin perpetuated the myth that male nipples are true evolutionary vestiges that stem from lactation in male as well as female ancestral mammals. They are, however, a developmental holdover from the early, indifferent stage of embryonic development, when the milk line arises but before the embryo has developed along the default female track or divergent male pathway. Male nipples are default structures formed earlier in development than the differentiation between males and females." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn

INTERTWINED. "In many cases it is not easy to disentangle the evolutionary and developmental processes that interact to produce wholesale phenotypic alteration." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn