Astrotholus antarcticus ( Fisher, 1940 )

Mah, Christopher L., 2023, New Genera, Species, and observations on the biology of Antarctic Valvatida (Asteroidea), Zootaxa 5310 (1), pp. 1-88 : 10-12

publication ID	https://doi.org/ 10.11646/zootaxa.5310.1.1
publication LSID	lsid:zoobank.org:pub:C6664128-1B4E-40C8-80E8-6D09AB49CB30
DOI	https://doi.org/10.5281/zenodo.8090090
persistent identifier	https://treatment.plazi.org/id/03C387E8-6638-FFE8-FF68-E6B285EFFE4E
treatment provided by	Plazi
scientific name	Astrotholus antarcticus ( Fisher, 1940 )
status

Treatment

Astrotholus antarcticus ( Fisher, 1940) View in CoL

FIGURE 1A–F View FIGURE 1

Anseropoda antarctica Fisher, 1940: 149 View in CoL ; Madsen 1955: 13; A.M. Clark 1962: 32 (key only); Bernasconi 1973a: 344.

Diagnosis

Body stellate (R/r=1.4–1.7), disk thick, strongly arched. Interradial arcs weakly curved to straight ( Fig. 1A View FIGURE 1 ). Abactinal plates scalar, imbricate, covered by widely spaced truncate granuliform spinelets, 3 to 6, ( Fig. 1B View FIGURE 1 ) distribution patterns associated with underlying plates. Superomarginals oval to quadrate with rounded edges in 1:1 relationship with inferomarginals. Superomarginals approximately twice to three times wider than inferomarginals, at least as viewed on the abactinal surface ( Fig. 1C View FIGURE 1 ). Actinal plates with short, thorn-like spinelets, 2 to 5 ( Fig. 1F View FIGURE 1 ). Furrow spines thorn-like, webbed 2 to 5 (6 indicated on the type) with spine number decreasing distally. Subambulacral spines, 2–5, webbed, arranged as an oblique comb relative to the furrow spines ( Fig. 1D View FIGURE 1 ).

Comments

Except for a further occurrence of this species from the type locality ( Madsen 1955), few accounts of this species have been reported since its original description ( Fisher 1940). Species epithet has been changed to reflect change in genus name.

Comment on Paratype USNM E10104 View Materials for Anseropoda antarctica

Examination of USNM E10104, a paratype specimen for Anseropoda antarctica listed by Ahearn (1995) reveals that it is incorrectly identified and not part of the original type series as designated by Fisher (1940). The specimen displays the plate pattern and the continuous granulation that identifies Kampylaster incurvatus rather than Anseropoda antarctica . Fisher (1940) listed seven specimens as part of the original type series, all of which were confirmed in the Discovery collections at the British Museum of Natural History (J. Ablett, pers. comm.). Although Kampylaster incurvatus is reported in Fisher (1940), no specimens from the Clarence Island type locality were listed in his account bringing the locality data for USNM E10104 into doubt.

Occurrence Bransfield Strait, Clarence Island , King George Island, Southern Ocean. 229 –426 m.

Description

Body shape stellate (R/r=1.4–1.7), body arched, disk thick, actinal surface concave, interradial arcs weakly curved to straight ( Fig. 1A View FIGURE 1 ).

Abactinal plates thin, scalar, imbricate with a curved external free edge ( Fig. 1C View FIGURE 1 ). Larger round, polygonal plates proximally with two to three series of plates extending along the radial arm regions. Interradial plates elongate, in distinct series extending from radial abactinal plates to the superomarginal plates. Abactinal plate surface covered with evenly spaced truncate granuliform spinelets, 3 to 6 ( Fig. 1B View FIGURE 1 ). Spinelets with fine tips, 4–6. Papular pores single present around proximal arm region and to approximately midway along the arm in single series, approximately 16 in the specimens examined (12 in the holotype). Madreporite quadrate to triangular, flanked by approximately four adjacent abactinal plates.

Marginal plates 42–48 at R=1.4 and 1.8 respectively, imbricate. Superomarginals oval to quadrate with rounded edges in shape in 1:1 relationship with inferomarginals. Superomarginals approximately twice to three times wider than inferomarginals, at least when viewed from the abactinal surface ( Fig. 1C View FIGURE 1 ). Inferomarginals, teardrop to ovate sitting at an oblique angle to the superomarginals ( Fig. 1F View FIGURE 1 ). Both marginal plates imbricate arrangement forming a crenulated outline around the lateral edge of the body. A shallow trench formed at contact between superomarginal and inferomarginal series. Superomarginals and inferomarginals with 5–12 granuliform spinelets with fine tips, 4–6 similar to those on the abactinal plates.

Actinal plates in regular oblique transverse series, approximately 42–48, each corresponding to inferomarginals and the adambulacral plate. Actinal plates with short, thorn-like spinelets, 2 to 5 ( Fig. 1D, F View FIGURE 1 ).

Furrow spines thorn-like, webbed 2 to 5 (6 indicated on the type) with spine number decreasing distally. Subambulacral spines, 2–5, webbed, arranged as an oblique comb relative to the furrow spines ( Fig. 1D, F View FIGURE 1 ). Oral plates with 9–12 webbed furrow spines, 8 cited the holotype description. Oral plate with raised ridge, each half bearing 3–4 thorn-like spinelets (6 total per interradius). Central fissure wide.