Mediaster tenellus Fisher 1905

• Main Author: Mah, Christopher L.
• Format: Other/Unknown Material
• Language: unknown
• Published: 2016
• Subjects: Biodiversity; Taxonomy; Animalia; Echinodermata; Asteroidea; Valvatida; Goniasteridae; Mediaster; Mediaster tenellus; Bering Sea; Gulf of Alaska; Pacific; Alaska
• Online Access: https://zenodo.org/record/6055248; https://doi.org/10.5281/zenodo.6055248

Mediaster tenellus Fisher 1905 Figure 6 A–D, Fig. 7 A Fisher 1905: 307; 1911: 202; Alton 1966a (as M. tenellus ?): 1680, 1688, 1702; Maluf 1988: 34, 118; A.M. Clark 1993: 263; Hendrickx et al. 2011: 808 (discussion about M. transfuga) Comments. Recently collected specimens from the North Pacific (Axial Seamount, Pioneer Seamount and others listed below) described herein are most similar to the M. tenellus described by Alton (1966a), who identified this species as “ M. tenellus ?” stating that his specimens were significantly different based on the greater R:r value (i.e. longer arms) and the number of superomarginals in the type (about 60 per interradius) versus his specimen (30 to 34 per interradius). Alton speculated that one possible reason for the higher number of superomarginals was due to the larger size of the holotype (R= 5.8 cm) versus those of the specimens he described (one of which, USNM E10436 is listed below, R= 3.1 cm). New material of comparable size (USNM 1407950, R=5.24) bears approximately 44–50 superomarginals per interradius which would appear to support Alton’s prediction. Collected North Pacific specimens herein conform to Fisher’s description of Mediaster tenellus based on a comparable number of slender furrow spines (four or five), subambulacral spines (three), the pointed spinelets on the tabulae (abactinal plates), and the granular covering on the marginal plates. These individuals differ in that actinal and marginal granules are pointed rather than prismatic and pedicellariae were not observed on the body surface. As indicated in the description, specimens of M. tenellus present in the southern Gulf of Alaska are more delicate and much more similar in appearance to the holotype of M. tenellus than those in the Bering Sea, which possess a more calcified skeleton and have a more stout appearance. Hippasteria tiburoni, from this same depth range and also from this region was recognized as a distinct species using molecular data (Mah et al. 2014) it is similar to the widely occurring ...