Porania Gray 1840

Porania Gray 1840

Figure 6 A–F

Porania Gray 1840: 288; 1866: 15–16; Perrier 1875: 280 [1876: 96]; Viguier 1879: 220 –222; Smith 1879: 276; Sladen 1889: 358; Perrier 1891: K107, 163; Bell 1893: 79; Perrier 1893: 849; 1894: 163; Fisher 1911: 248 (in key); Koehler 1921: 41; 1924: 152; Mortensen 1927: 90; Fisher 1940: 154; Madsen 1956: 160; Bernasconi 1964: 263; Spencer & Wright 1966: U69; Tablado 1982: 88; A. M. Clark 1984: 42; Clark & Downey 1992: 206; A.M. Clark 1993: 231; Asteropsis (pt) Müller & Troschel 1842: 62

Pseudoporania Dons 1936: 18 [type species Pseudoporania stormi Dons 1936]

Type species: Porania pulvillus (O.F. Müller 1776)

Diagnosis. (Note: This diagnosis is based primarily on P. pulvillus. The status of “ Pseudoporania ” stormi remains uncertain and as such, it was not included as part of the treatment herein.) Body weakly stellate R/ r=1.2–2.4. Disk tumescent, rays triangular in outline. Interradial arcs rounded. Abactinal, marginal and actinal surface overlain by a thick layer of skin obscuring plate boundaries in wet or certain dried specimens. Abactinal skeleton with round, cylindrical and irregularly lobate or polygonal shaped plates. Abactinal plates primarily imbricate but with some showing variable density and some displaying more open distribution between plates. Papular pores, one to ten per region, several of which are confluent. Papulae absent interradially. Papulae less abundant relative to how dense imbricate plates ae present. Marginal plates, oblong to scresent shaped. Inferomarginals similar in shape, somewhat more oblong) to but more staggered from superomarginals. Inferomarginals staggered from superomarginals. Each inferomarginal with one to five short, blunt cylindrical skin covered spine forming a distinct fringe along the actinolateral edge. Actinal surface flat. Plates quadrate to rectangular, imbricate and arranged in regular transverse series corresponding to the adambulacral plates and to the actinal-facing inferomarginals. Actinal surface devoid of accessories. Furrow spines one or two, most often two. Single subambulacral spine, all furrow spines sheathed by thck skin.

Included species: P. pulvillus (O.F. Müller 1776), P. s t o r m i (Dons 1936)

Taxonomic comments. Glabraster & Pseudoporania: Porania as has been outlined by A.M. Clark (1984) and Clark & Downey (1992) is paraphyletic. Our Fig. 1 supports “ Porania ” antarctica as a separate, distinct lineage. Re-assessment of subgenera, such as Pseudoporania based on morphology also suggests paraphyly of Porania. Fig. 1 shows separation between Porania pulvillus and “ Porania ” antarctica leading to reistatement of Glabraster A.H. Clark. Porania pulvillus represents the type species for Porania and retains the original designation. Porania pulvillus displays distinctly different abactinal and marginal plate morphology from Glabraster antarctica. The North Atlantic P. pulvillus has a densely articulated, reticulate, becoming imbricate skeleton (Fig. 5 A, F), as opposed to the more widely spaced, distinctly reticulate skeleton observed in G. a n t a rc t i c a (Fig. 6 A). Marginal plate morphology between the two taxa and adambulacral spination (i.e., furrow and subadambulacral spines) is also significantly different between the two taxa. In contrast, the actinal and marginal plate orientation looks identical to those in Glabraster antarctica, which suggests some parallelism in actinal plate systems.

Pseudoporania stormi Dons 1936 should only provisionally be considered as a subgenus within Porania. As indicated below, it shows several characters consistent with established poraniid genera, such as Chondraster or Culcitopsis.