Enigmaster scalaris McKnight & H.E.S. Clark 1996

Enigmaster scalaris McKnight & H.E.S. Clark, 1996

H.E.S. Clark & McKnight, 1996; 207; 2001: 45

Comments. It seems possible that characters listed by McKnight and Clark (1996) may be misinterpreted from dried tissue. The fibrous rungs or bars figured in descriptions of Enigmaster appear to be dried connective ligaments connecting the abactinal surface facets of paired ambulacral ossicles as observed in Ceramaster and other goniasterids. Similarly, the absence of suckers on the tube feet may be a misinterpretation of tube foot from dried tissue deformation. Furthermore, the perception of a suckerless tube foot could be a dried “simple disk” type tube foot as indicated by Santos et al. (2005) who described three different types of tube feet, only one of which actually possessed a well-developed sucker.

The distinctive hastate arm shape observed in Enigmaster could represent unusual phenotypic variation, which is observed in other valvatidans, such as the South African goniasterids Toraster tuberculatus and Calliaster acanthodes (Mortensen 1933) in conjunction with predation or developmental abnormalities.

If the unusual characters that have been used to distinguish Engimaster are de-emphasized, the specimen described by McKnight and Clark (1996) more closely resembles Ceramaster, Peltaster or possibly Sphaeriodiscus. However, the description does not surrender a clear picture of precisely which genus Engimaster may be a synonym of and it is for this reason that Enigmaster is left in the key. Additional specimens, especially wet-preserved material, of the Engimaster morphotype may disprove or further support statements presented herein.

Distribution. Adjacent to Auckland Islands, south of New Zealand, 520 m.

Material examined. None. This species is known from a unique holotype housed in the Auckland Museum (AK 797001), which was unavailable for loan. No other specimens are known.

Description. Because extensive descriptions of this species are outlined in McKnight and H.E.S. Clark (1996) and H.E.S. Clark and McKnight (2001) only a summary description of characters from Clark and McKnight (2001) is listed here. But see comments above on the validity of this description as useful diagnostic characters.

Disk large, thin, weakly pentagonal. Arms hastate (i.e., arrowhead shaped with basal lobes emerging at right angles) with marginals large and regular near arm tip. Marginal plates interradially small, jumbled.

Abactinal plates angular with granules, peripheral series smaller. Central granules round, oval or hexagonal. Granules proximally oblong, oval or irregular in shape with close mosaic of finely thorny granules. Papulae six or seven, surrounding each plate. Present radially, but absent to sparse interradially. Straight pedicellariae present. One type with slender, tapering blades, the other with broad, fan-like blades. Both leave oblong pits, one to four per plate, with a distinct lip. These are widely present abactinally. Other pits lacking lips. Madreporite irregular in shape.

Superomarginals and inferomarginals clearly evident at armtips. Plates wide, rectangular, forming beveled edge to disk. Plates granulated (bare on specimen) with peripheral granulation. Distalmost two to three superomarginals in contact over midline. Interradial marginal series irregular in shape, in jumbled series.

Actinal areas large in regular chevrons. Actinal plates square, rectangular and irregular with plates bordering adambulacrals well defined, rectangular, large. Plates covered by small granules. Peripheral granules round to angular, spaced. Each plate with pedicellariae pits, one to three, occuring more distally and less proximally.

Furrow spines three to five (four on average, proximally three, five distally). Subambulacral spines two or three, short, thick, forming gently curivng series. Subambulacral granules angular, well-spaced forming two to three rows.