Recognition of the Asteroid (Echinodermata) Crown Group: Implications of the Ventral Skeleton

Growth zones and extraxial-axial skeletal homologies in Asteroidea (Echinodermata)

“…The actinals develop as gusset plate systems. The development of actinal gusset plate systems is developmentally secondary to marginals and adambulacrals (Hotchkiss & Clark 1976, Blake & Hotchkiss 2004). The actinals are not adjacent to the terminal plate.…”

<p><strong>Comments on "The phylogeny of post-Palaeozoic Asteroidea </strong><strong>(Neoasteroidea, Echinodermata)" by A.S. Gale and perspectives </strong><strong>on the systematics of the Asteroidea</strong></p>

“…We instead find the marginals and abactinals of Porania antartica Smith to be remarkably similar (using another such term) to those of N. barberoi based on direct specimen comparisons (Blake et al 2000, figs. 1-4;Blake & Hotchkiss 2004, fig. 1.2).…”

“…However, given phrasing difficulties, another criterion is important. Although Gale (2011a: 65) acknowledged that the original interpretation of Noriaster barberoi was "largely on the basis of similarities of ossicle arrangement of the actinal surface with that family," he did not note the crucial alignment of the actinal ossicles with the marginal frame, an expression emphasized in poraniids by Hotchkiss and Clark (1976) and reviewed for asteroids of all ages by Blake and Hotchkiss (2004). Such alignment is suggested in certain members of the Porcellanasteridae (Madsen 1961) but it is otherwise unknown beyond the poraniids and forcipulataceans, and it thereby provides an objective rather than a subjective criterion.…”

Evolutionary and ecological significance of Lepidaster grayi, the earliest multiradiate starfish

“…The basis for much of the controversy over the functional morphology of Palaeozoic starfish is that the phylogenetic relationships of the Asteroidea are poorly understood. It is generally agreed that all Palaeozoic taxa belong to the stem (Blake, 1987; Gale, 1987; Blake & Guensburg, 1990; Donovan & Gale, 1990; Blake, Janies & Mooi, 2000; Blake & Hotchkiss, 2004; Shackleton, 2005), with crown‐group starfish known only from the post‐Permian, but no consensus has been reached as to which are the most basal extant asteroids. Some authors (e.g.…”