Limnasterias, Setiadi, 2019

Setiadi, Anargha, 2019, A new genus and two new species of sea stars (Family Asterinidae) from Indonesian marine lakes, with notes on habitat and feeding ecology, Zootaxa 4712 (3), pp. 392-402 : 394

Limnasterias gen. nov.

Type species. Limnasterias oinops sp. nov.

Other included species. Limnasterias estradivariae sp. nov.

Diagnosis. Stellate, high aspect body with discrete rays, sides almost vertical, flat actinally. Abactinal surface covered by thick tissue, occluding plate boundaries; plates with crescentiform notch if papulate, with glassy convexities and one to seven digitiform to sacciform spinelets. Papulae mostly single, large, on upper rays around 75% the width of adjacent plates; aligned irregularly on disc and ray medians, laterally in series of up to five rows. Papulate area extensive, on rays directly bordering superomarginals or separated by up to two rows of non-papulate plates. Inferomarginals laterally elongate with distal projection, boot-shaped, with clusters of tall spinelets at the apex. Actinal plates obliquely aligned, with single spines. Superambulacral plates absent. Superactinal plates reduced to a single row lining distal end of marginal angle, often appressed to abactinal wall. Interior with thin resinous lining.

Taxonomic comments. Limnasterias gen. nov. is distinguished from other asterinid genera by stellate, high body with nearly perpendicular sides; thick abactinal integument; boot-shaped inferomarginals; monacanthid actinal plates and extensive, single papulae serially aligned at ray sides in up to five rows; interior with only reduced superactinal plates present and resinous lining. Papular pores are large, often three-quarters the width of nearest plates. Papulae are absent only from near ray tips, margins, actinals, and parts of the interradiial axes. These characters impart a perforated, sieve-like appearance to dried specimens with ruptured papulae. Interior distinctly devoid from protrusions or buttressing plates aside from superactinal plates, which are appressed to the marginal corner.

Limnasterias gen. nov. shares some features with Tegulaster and Disasterina , notably the stellate form, integument cover, irregular plate alignment at ray median, glassy sacciform armature, circular superomarginal plates and predominantly monacanthid actinal interradial plates. However, it is distinguished by its high semicircular profile without flattened margins, thinner plates (compared to Tegulaster ), reduced superactinal plates, presence of resinous lining and absence of superambulacral plates. Inferomarginal plates of Limnasterias gen. nov. are boot-shaped with distal projections, instead of ovoid or rectangular as in Tegulaster or Disasterina . Also notable are five rows of papulate plates at the sides of ray bases in Limnasterias gen. nov., compared to three rows in Tegulaster or irregular in Disasterina ( O’Loughlin & Waters 2004) ; the former possesses more numerous and larger papulae, with papulate plates immediately bordering superomarginal series for much of the ray in larger specimens.

Limnasterias gen. nov. is dissimilar from other genera used for comparison, including Ailsastra O’Loughlin & Rowe, 2005 ; Aquilonastra O’Loughlin 2004 ; Asterinides Verrill 1913 ; Cryptasterina Dartnall et al. 2003 ; Meridiastra O’Loughlin 2002 ; Paranepanthia Fisher 1913 ; and Pseudasterina Jangoux & Aziz 1985 . While the lack of superambulacral plates is shared by all but Aquilonastra and Cryptasterina , most possess internal contiguous projections from abactinal or actinal plates at the interradii ( O’Loughlin & Waters 2004), which are not found in Limnasterias gen. nov. Importantly, other diagnostic characters such as sunken carinal series ( Ailsastra ), granuliform armaments ( Meridiastra , Cryptasterina ), interior projections of abactinal and actinal plates ( Asterinides , Meridiastra ), dense clusters of acicular armaments ( Paranepanthia ) and flattened margins or thin interradii ( Aquilonastra , Cryptasterina , Meridiastra , Paranepanthia , Pseudasterina ) are not applicable for Limnasterias gen. nov.

Etymology. Generic name is a combination of limna- (G., “lake”) and - asterias (G., “starry”), referring to its habitat and shape.