Aristocystitidae

Belongs within: Diploporita. The Aristocystitidae are a group of Lower Ordovician to Middle Silurian cystoids characterised by having the brachioles arising from facets directly adjacent to the mouth, with ambulacra exceedingly short. Characters (from Kesling 1967): Theca ovate to elongate, typically tapered or constricted at aboral end, containing numerous, irregularly arranged plates. Column small and… Continue reading Aristocystitidae

Diploporita

Belongs within: Pelmatozoa.Contains: Aristocystitidae, Protocrinitida, Sphaeronitidae. The Diploporita are a Lower Ordovician to Lower Devonian group of echinoderms in which the thecal plates bear pore groups each located on a single plate. Characters (from Kesling 1967): Thecal pores developed as units mostly confined to single plates, typically in form of diplopores but in some present… Continue reading Diploporita

Protocrinitida

Belongs within: Diploporita. The Glyptosphaeritida are a group of Lower Ordovician to Middle Silurian cystoids bearing radial ambulacra with alternating lateral branches. Characters (from Kesling 1967): Diplopore-bearing cystoids with globular, ovate, pear-shaped, or saclike thecae. Ambulacra radial, extending over theca, with alternating lateral branches ( single or in groups) leading to brachiole facets; in many… Continue reading Protocrinitida

Sphaeronitidae

Belongs within: Diploporita. The Sphaeronitidae are a group of Lower Ordovician to Lower Devonian cystoids with short ambulacra branching directly from the corners of the mouth. Characters (from Kesling 1967): Theca typically spherical to ovoid. Ambulacra short, commonly preserved as grooves in thecal plates of oral region, branching directly (fan-wise) from corners of mouth; several… Continue reading Sphaeronitidae