Bathycrinus aldrichianus Thomson, 1876

Eléaume, Marc, Bohn, Jens-Michael, Roux, Michel & Améziane, Nadia, 2012, Stalked crinoids (Echinodermata) collected by the R / V Polarstern and Meteor in the south Atlantic and in Antarctica, Zootaxa 3425, pp. 1-22 : 3-4

Bathycrinus aldrichianus Thomson, 1876

Figure 1 ; Table 1 .

Synonymy: Bathycrinus aldrichianus Thomson, 1876: 47 –51, fig. 1; Bathycrinus campbellianus P. H. Carpenter, 1884: 238 –240, fig. 15; Bathycrinus serratus A.H. Clark, 1908b: 205 –207, fig. 1; Bathycrinus aldrichianus Gislén, 1938: 15 –16; 1951: 51–52, pl. (figs 1–2, 5); Macurda & Meyer, 1976: 647–667, figs. 1–5; pl. 1–5; A.M. Clark, 1977: 159–162, fig. 1g; Mironov, 2008: 143; Hess, 2011a: T153, fig. 75 (1m –n).

Material examined. Specimens from Pillsbury expedition, 1965, station P-292 ( Table 1 ), housed in the collections of the Smithsonian Institution, Washington D.C., catalogue number USNM E17896 .

Complementary description of stalk articulations. In B. aldrichianus , the transition from relatively rigid mesistele to flexible dististele is rapid and restricted to the distalmost stalk. The ratio of columnal height to maximum diameter is>2.8 (up to 3.6) in the mesistele and <1 in the dististele. The branched distal rootlike radix is adapted to anchoring into soft sediment. Macurda & Meyer (1976) were the first to describe the stalk articulations using SEM in a specimen from the Gulf of Guinea. From the same sample, we give additional information on their ontogeny ( Fig. 1 ). In mesistele columnals of small juveniles, the proximal articular facet is flat and circular, whereas the distal facet has a ligamentary pit on each side of the wide rudimentary fulcral ridge ( Fig. 1 A). In middle-sized specimens, ligamentary depressions become deep and the fulcral ridge has concave lateral sides ( Fig. 1 B–D). In large stalks, synarthries are rounded oval in middle and distal mesistele with the longest diameter perpendicular to the fulcral ridge ( Fig. 1 E), which remains very wide (1/3 of diameter) and is covered by vermiculated syzygial stereom. A similarly wide fulcral ridge was observed in B. gracilis ( Roux 1987: fig. 15E) confirming that the two species are very closely related. As usual in bathycrinids, dististele synarthries are strongly oval with the longest diameter corresponding to a narrow fulcral ridge and wide ligamentary depressions ( Fig. 1 F). The axial canal separates the fulcral ridge into two segments with sharp inner ends, and with dense calcite and regular rows of small crenulae (up to 15–18 on each segment) along their axes.

Occurrence. B. aldrichianus is known from NW, central and SW Atlantic at depths ranging from 3317 to 5850 m, possibly from 3305 to 5860 m ( Table 1 ).

Figures

FIGURE 1. Stalk articulation in Bathycrinus aldrichianus (USNM E 17896). A – B: proximal synarthries, C: mid mesistele synarthry, D – E: distal mesistele synarthries, F: dististele synarthry, A: small juvenile, B – D: medium-sized specimen, E – F: large specimen.

Tables

TABLE 1. Sampling stations of Bathycrinus aldrichianus Thomson, 1876.

Cruise/Station	Location	Depth (m)	Reference Remarks
Challenger Exped./106 Albatross/2226	01°47’N–24°26’W 37°00’N–71°54’W	3382 3739	Thomson, 1876 Holotype (crown) A.H. Clark, 1908b 1 crown B. serratus
Albatross/2713	38°20’N–70°08.3’W	3398	A.H. Clark, 1908b 1 distal stalk
Atlantis/1948	34°53’N–46°24’W	4625	A.H. Clark, 1949 2 stalks
Swedish Deep-sea Exped./329	09°38’N–26°20’W	5600–5610	Gislén, 1951 1 small crown
Swedish Deep-sea Exped./371	24°12’N–63°23’W to 24°28’N–63°18’W	5850–5860	Gislén, 1951 1 stalk
Pillsbury, 1965	00°12’N–05°11’E	3595	Macurda & Meyer, 12 specimens 1976
Chain/50	37°59.2’N–69°26.2’W	3834	A.M. Clark, 1977 1 small armless
Atlantis II cruise 60/259A&D	37°13’S–52°45’W	3305–3317	A.M. Clark, 1977 2 crowns