A revision of the comatulid genus Stephanometra AH Clark with a rediagnosis of the genus Lamprometra AH Clark (Echinodermata: Crinoidea)

Abstract

Several genera in the comatulid crinoid family Mariametridae are currently ambiguously distinguished on the basis of variations in length and robustness of oral pinnules. Previous descriptions have suggested that at least the genera Stephanometra and Lamprometra, both common and widespread on Indo-western Pacific reefs, are imperfectly distinguishable. A detailed morphological re-examination supports distinct Stephanometra and Lamprometra. The five currently recognized species of Stephanometra are reduced to two: S. echinus under S. tenuipinna, and S. spicata (including S. oxyacantha) and S. spinipinna under S. indica. Of specimens examined in the indica-spicata-oxyacantha series, 20% are intermediates that cannot be satisfactorily assigned to species based on current diagnoses. In Lamprometra, L. klunzingeri and L. palmata gyges are formally reduced to infrasubspecific variants of L. palmata.

Phylogeny and taxonomy of Himerometroidea (Echinodermata: Crinoidea)

“…Stephanometra, formerly in Mariametridae, is here treated as belonging to the resurrected Stephanometridae, based on the analysis support plus the following morphological feature: distal margin of oral pinnule segments smoothly rounded (no spines); articular facets of one to few oral pinnules completely flat with reduced shallow ambulacral groove; small shallow ligamentary cavities, and limited tissue, all together generating a stiffness and styliform appearance of oral pinnules (Rankin & Messing, 2008). At least some Colobometridae and Pontiometridae have similarly stiff, spinelike oral pinnulars but differ from Stephanometra in having a rim of strong spines along the distal margins and often a better developed ambulacral groove (C. G. Messing, personal observations).…”

“…With the exceptions of two molecular phylogenetic reconstructions spanning all extant crinoid groups (Hemery et al, 2013;Rouse et al, 2013), and sequence-based revisions of a few taxa (Comatulidae, Summers et al, 2014Summers et al, , 2017Aporometra, Helgen & Rouse, 2006; Himerometra and some Mariametridae genera, Taylor et al, 2017Taylor et al, , 2018Foo et al, 2021), the currently taxonomic Comatulida remains based largely on morphology. Although recent revisions have clarified features of some groups (e.g., Messing, 1981Messing, , 1995Messing, , 1998Messing, , 2013Messing, , 2020aRowe et al ., 1986;Rankin & Messing, 2008;Roux et al, 2019), relatively little work has so far applied phylogenetic methods (Messing & White, 2001;Summers et al, 2014Summers et al, , 2017Taylor et al, 2017Taylor et al, , 2018Foo et al, 2021), and most of the current familial-to specific-level classification of Comatulida remains based on A.H. Clark's Monograph of Existing Crinoids (A. H. Clark, 1915a, 1921, 1931, 1941, 1947, 1950A. H. Clark & A. M. Clark, 1967) with minor modifications in Hess & Messing (2011).…”

Shallow-water Comatulids (Echinodermata: Crinoidea: Comatulida) of the Ashizuri-Uwakai Sea, Shikoku Island, Southern Japan

“…Genus Lamprometra A. H. Clark, 1913 is characterized by enlarged but not spine-like proximal pinnules, of which P 2 is the largest. Recent taxonomic revision showed the monospecificity of this genus (Rankin and Messing 2008).…”