Synonymy of Neomorphaster forcipatus

Neomorphaster forcipatu s Verrill 1894 is herein argued as a synonym of Neomorphaster margaritaceus (Perrier in Milne-Edwards 1882). Neomorphaster forcipatus was distinguished from Neomorphaster eustichus Sladen (= Neomorphaster margaritaceus) based on numerous pedicellariae scatted over the surface, a greater number of papulae, transverse arrangement of abactinal spinelets, and having elongate and slender, furrow spines. Clark and Downey (1992) later refined the differences between the two species to papular number, differences in spinet shape (clavate versus granuliform), and oblique versus parallel actinal spines. All three of these characters show high levels of variation which erodes the morphological distinction between the two species. Papulae number per pore for example, varies between a 1 to 5 per pore, in some cases on a single individual (Fig. 1C). The holotype for N. forcipatus (USNM 14859) shows weakly visible but single pores, in addition to the 3–5 pores summarized by Clark & Downey (1992) with the holotype and one paratype both showing between 1 to 3 papular pores. Similarly, the distinction between granuliform versus clavate granulation varies between specimens, sometimes on the same specimen (e.g. USNM 1016059). Combinations of these characters is similarly inconsistent between species and muddled with other character types. For example, granuliform spinelets, which characterize N. forcipatus, are present on individuals with only one or two papular pores. The third character outlined by Clark & Downey (1992), is arrangement of actinal spines relative to the furrow spines as oblique or parallel. Examination of paratypes and additional specimens reveals that actinal spines are not inflexible and that orientation is more varied than what was observed in the type specimens and thus, not a consistent character difference between the two species.

Neomorphaster margaritaceus is here considered a wide-ranging Atlantic species, present in the east Atlantic at a depth of 400–5410 m but known from the west Atlantic side from 513–2000 m. New occurrences of this species show Neomorphaster present in the Bahamas to Angola in the South Atlantic.

In situ Observations

When observed in situ, Neomorphaster in the western North Atlantic are abundant for a given region but are widely dispersed from one another (at least 0.5 to 1.0 m between individuals) along hard and soft substrata (Figs. 1A–B). In most instances, the animal appears to have disc and arms appressed onto the surface (Fig. 1B). Spines around the oral region are numerous and elongate, directed away from the deeply recessed mouth region (Fig. 1D). Furrow spines are similarly elongate, large, thick and blunt with adjacent actinal spines similarly if not more thickened than the furrow spines with weakly clavate tips. All spines are directed ventrally suggesting interaction with the substrate.

Based on the observation of foraminifera within the gut cavity of USNM E18509 (Fig. 1E) it is argued that these feed in a fashion analogous to Zoroaster sp. utilizing body posture and spines appressed into the sediment to feed.

Anecdotally, individuals were observed in highest abundance within the canyons and in regions adjacent to the North American continental shelf. No Neomorphaster were observed during EX2104 to the Corner Rise and North Atlantic Seamount chains.

Distribution/Occurrence

East Atlantic. Azores (Fig. 1A), Hebridean Slope, Rockall Trough, SW Ireland, Morocco, Faroe Islands, Aviles Canyon (Bay of Biscay), 400–5410 m.

West Atlantic. Laurentian Canyon to Hudson Canyon, 1400–2000 m

New Occurrence. Bear Seamount, Lydonia Canyon, McMaster Canyon, Retriever Seamount (Fig. 1B), Bahamas to Cachalote Guyote, Kai Ridge. Angola (South Atlantic). 513–1888 m

Material Examined

Holotype. USNM 14859, SW of Nantucket Shoals, Massachusetts, North Atlantic. 39.7167 -70.4833, 1811 m. Coll. NMFS Albatross, 16 July 1886. 1 dry spec. R = 8.5 cm r= 1.6 cm.

USNM E 15957, West of Luanda, Angola, South Atlantic. -9.08 12.28, 1427–1643 m. coll. R /V Atlantis II, 23 May 1968. 1 dry spec. R = 6.9 cm r= 1.1 cm.

USNM E 18509, South of Pinders Point, Grand Bahama Island, Bahamas. 26.2833, -78.6833, 513– 715 m. Coll. R /V. Gerda, 3 March 1965. 1 dry spec. R =9.0 cm, r= 1.8 cm.

USNM E 30706 Lydonia Canyon, Georges Bank, 40.2992 -67.6647, 1443 m. Coll. DSR/V Alvin, 15 Sept. 1982. 1 dry spec. R =8.0 cm r= 1.4 cm.

USNM 1016059 Bear Seamount, North Atlantic, 39.9414 -67.3891, 1132–1888 m. Coll. R /V Delaware II, 19 May 2003, 7 dry specs. R = 7.2 cm r= 1.3 cm, R = 4.7 cm r= 0.9 cm, R = 5.3 cm r= 1.1 cm, R = 5.5 cm r=1.0 cm, R = 6.6 cm r= 1.2 cm, R = 6.3 cm r= 1.2 cm, R = 6.7 cm r= 1.1 cm.

Images Observed

SE of the Azores, North Atlantic 38.1592, -26.236331, 2098 m

EX2206_IMG_20220807T140030Z_ROVHD.jpg

Retriever Seamount, North Atlantic

EX1404L3_IMG_20140925T162554Z_ROVHD_ASR.jpg

Kai Ridge, North Atlantic, 38.755764, -30.461309, 1824 m

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