Paralophaster Fisher 1940
- Dataset
- New Genera, Species, and observations on the biology of Antarctic Valvatida (Asteroidea)
- Rank
- GENUS
Classification
- kingdom
- Animalia
- phylum
- Echinodermata
- class
- Asteroidea
- order
- Valvatida
- family
- Solasteridae
- genus
- Paralophaster
description
The key diagnostic character for Paralophaster is based upon Fisher’s (1940) diagnosis which describes “ undifferentiated ” superomarginal plates. The description of this character has undergone modification by A. M. Clark (1962) and H. E. S. Clark (1963) as superomarginal plates which are similar or identical to the abactinal plates in size. Based on observations of Lophaster specimens, the marginal plates show two relatively thick and elongate paxillar heads which are variably articulated or show fusion at the basal portion of each plate. This appears to be a consistent character of marginal plates among Lophaster species. Paralophaster in P. godfroyi, P. antarcticus, and P. densus when clearly present appear to be shorter and smaller overall than the inferomarginals, but closer in appearance to the abactinal paxillae. Marginal paxillae in Lophaster appear to be a function of size, length and wide spacing versus those in Paralophaster which are smaller, shorter and more crowded. Marginal Plates in Paralophaster Blake’s (1978) criterion defined the marginal plate series as extending from the primary on the disk to the terminal plate on the arm. Identification of plates as superomarginal versus inferomarginal plate series was based on their relative position, with the inferomarginal series identified based on its proximity to the adambulacral plate series. Marginal plate characters show two primary trends in Paralophaster, those with only a single prominent marginal plate series and those showing two, including clearly defined superomarginals. In both instances, it is assumed that both series are present but that there is some degree of character modification to the superomarginal and / or inferomarginal series. In the former, there is only a single prominent series which, based on location and position is thought to be an enlarged inferomarginal series. A. M. Clark (1962) interpreted this as superomarginal plates which were essentially identical with the abactinal paxillae but very weakly expressed or jumbled, such as in Paralophaster lorioli. Paralophaster paucispinus n. sp. displays a more extreme case with a seemingly incomplete or possibly absent superomarginal plate series. In the other Paralophaster, there is a well-developed, observable series of superomarginals that are present on the abactinal surface above and either adjacent or alternating with the inferomarginal plates, such as in P. godfroyi, P. hyalinus, P. antarcticus and P. densus. In these latter species, larger specimens (> R = 3.0 cm) such as those of Paralophaster godfroyi, the paxillar base of the presumptive superomarginal plates were directly articulated on the surface of the trunk of the larger inferomarginal paxillae in a manner identical to those on other solasterids, such as Lophaster gaini. In Paralophaster antarcticus, superomarginal paxillae were observed as a separate series, intercalated above and between the larger inferomarginal series.