Novocrania lecointei (Joubin, 1901)

Novocrania lecointei (Joubin, 1901) View in CoL

Stratigraphic range: late Middle Eocene–Recent (Robinson in press)

1901: Crania lecointei Joubin, Sci. Exped. Antarct. Belge, p. 9–11, pl. 2., figs. 13–15.

1902: Crania patagonica Dall, Proc. United States Nat. Mus., 24, p. 562.

1918: Crania joubini Thomson, Aust. Ant. Exp. Sc. Rep., Ser. C, p. 10, pl. 16, fig. 18–19. 1965: Crania antarcticaensis Hatai, JARE 1956–1962 Sc. Rep., Ser. E, 26. p. 2, figs. 1a–5b. 1986: Neocrania lecointei (Joubin), Lee & Brunton, Bull. Nat. Hist. Mus. (Geol.), 40 (4), p. 152. 2001: Novocrania lecointei (Joubin), Lee & Brunton, Bull. Nat. Hist. Mus. (Geol.), 57 (1), p. 5.

1940: Crania valdiviae Helmcke, Wissen. Erge. Deutsch. Tiefsee Exp., 1898–1899, 24 (3), p. 234, text fig. 4a –d. 1986: Neocrania valdiviae (Helmcke), Lee & Brunton, Bull. Nat. Hist. Mus. (Geol.), 40 (4), p. 152.

2001: Novocrania valdiviae (Helmcke), Lee & Brunton, Bull. Nat. Hist. Mus. (Geol.), 57 (1), p. 5.

Synonymy. Joubin (1901) first described this species from Antarctica. Scientific expeditions to Antarctica by Australia / New Zealand, Germany and Japan resulted in several synonymous names being given to this species. Foster (1974, p. 43) stated “there is only one highly variable species of Crania extending through the Antarctic and South American areas”, synonymized C. patagonica , C. joubini and C. antarcticaensis with Crania lecointei and noted that C. valdiviae Helmcke, 1940 from Saint Pauls Island, southern Indian Ocean, might also be a synonym but adequate published figures or topotypes were not available. Cooper (1973a) listed C. valdiviae as present in the Indian Ocean. Digital images of the holotype (ZMB Bra 196) and two paratypes (ZMB Bra 197) of Novocrania valdiviae were examined and this species is placed in synonymy under N. lecointei .

Localities. N. lecointei has previously been known as a species found only in the Southern Ocean; from Antarctica and southern South America (Foster 1974), and off Macquarie Island , south of New Zealand (Zezina 1980). More recently specimens have been found off Taranaki , New Zealand (Robinson & Lee 2007) around northern New Zealand and Lord Howe Island , Australia . Lord Howe Island , Australia (Robinson & Lee 2011), the Galapagos Islands and Japan (Cohen et al. 2014). Localities are shown in Figure 3 and includes localities of material examined ( Table 6) and published localities (Appendix 4).

Stratigraphic range. Robinson & Lee (2011) and Robinson (in press) figured late Middle Eocene (Kaiatan, 39.1– 36.7 Ma) specimens from North Otago, New Zealand, assigned to N. lecointei .

Type material and type locality. The location of the type specimen of N. lecointei is unknown (Foster 1974), the type locality is in the Bellinghausen Sea, Antarctica, 70.383°’S, 82.783°W (Joubin 1901).

Material examined. Recent specimens were examined from the Ross Sea and the Weddell Sea, Antarctica, from west of Cape Taranaki , New Zealand and seamounts to the west and north of New Zealand, from Lord Howe Island , Australia and Japan ( Table 6). Digital images of N. valdiviae were provided by Carsten Lüter of the Museum für Naturkunde, Berlin .

Description. The dorsal valves vary in outline from sub-circular to sub-oval to sub-quadrate to sub-pentagonal ( Figs. 10A–H) and from rounded to strongly conical ( Fig. 10I –K), the apex position varies from central to near the posterior. The largest specimen examined was 12 mm long, 15 mm wide and 4 mm high ( Fig. 10B, Ross Sea, Antarctica). Most populations examined have a range of valve ornament. Specimens within a single population may vary from being strongly spinose to lacking spines (for example Fig. 10E, F, off Chiba, Japan) and from having strong to weak concentric growth lamellae to being smooth. The dorsal valve exterior is usually white or grey, a specimen from Japan ( Fig. 10F) was white and brown.

The spines may be oriented vertically to sub-vertically to sub-horizontally, they are usually placed randomly but occasionally in radial rows, and are less common on the valve posterior. The specimens from Taranaki (dredged up in-situ on a boulder from 400m) have long (~500 µm), delicate, hollow spines ( Fig. 10G, J). The Taranaki specimens grew in crevices, which may have protected them from current driven debris or grazing predators, and allowed the full growth and preservation of the spines. Specimens from other populations examined have stubby, broken spine bases ( Fig. 10A, K–L, Antarctica; Fig. 10C, Lord Howe Island; Fig. 10D seamounts off New Zealand) or more robust short spines ( Fig. 10E, Japan).

The dorsal valve inner surface is densely punctate. The posterior adductor muscle scars are sub-round to suboval in outline ( Fig. 11A–I View FIGURE 11 ) and they may be slightly concave, flush with the valve surface or slightly convex and have punctae scattered across their surface. The anterior adductor slow-muscle scars are variable, they may be reniform or U-shaped ( Fig. 11A–I View FIGURE 11 ) and the quick-muscle scars form dimples on the concave side. The support structure scars are commonly raised and slope medially ( Fig. 11H View FIGURE 11 ) and may be connected to ( Fig. 11D, E View FIGURE 11 ) or separated from ( Fig. 11F–I View FIGURE 11 ) the anterior adductor muscle scars. The small anterior muscle scars may be widely to narrowly separated ( Fig. 11G, E View FIGURE 11 respectively) or be side by side ( Fig. 11H, I View FIGURE 11 ) and may be slightly raised ( Fig. 11H, I View FIGURE 11 ) or flush with the valve floor.

The ventral valve of N. lecointei is a very thin, transparent, organic membrane ( Fig. 11J, K View FIGURE 11 ). The posterior adductor muscles attach to organic pads and the anterior adductor and oblique internal muscles attach to an organic rostellum ( Fig. 11J–L View FIGURE 11 ).

NHMUK—Natural History Museum, London, NIWA—National Institite of Water and Atmospheric Research, Wellington, New Zealand ; NMNZ—Te Papa Tongarewa, National Museum of New Zealand, Wellington ; OU—Geology Museum, University of Otago, Dunedin, New Zealand ; UMUT—Tokyo University Museum, Tokyo, Japan .

Abbreviations: juv —juvenile specimen, sut —suture.

Ecology. In the Southern Ocean N. lecointei is found “attached to rocks ranging from pebble to boulder size” (Foster 1974, p. 45; Fig. 10H), in Antarctica it has a known depth range of 358–1670 m ( Table 6). This species was found attached to a soft, fissured sandstone off the coast off Taranaki (Robinson & Lee 2007). In the waters to the east, west, north-east and north-west of New Zealand and off Lord Howe Island , Australia, N. lecointei has a known depth range of 157–1000 m ( Table 6). In Japan it has a known depth range of 135–351 m ( Table 6) . At Saint Pauls Island in the Indian Ocean specimens were collected from 672 m (Helmcke 1940). The specimen in Fig. 10G has a tiny juvenile attached; from my observations this is rare in craniids.

Remarks. The formation of the hollow spines of N. lecointei is described in detail in Robinson & Lee (2011).

NHMUK—Natural History Museum, London, NIWA—National Institite of Water and Atmospheric Research, Wellington, New Zealand ; NMNZ—Te Papa Tongarewa, National Museum of New Zealand, Wellington ; OU—Geology Museum, University of Otago, Dunedin, New Zealand ; UMUT—Tokyo University Museum, Tokyo, Japan .

Abbreviations: aaq —anterior adductor quick-muscle scar, aas —anterior adductor slow-muscle scar, oi —oblique internal muscle scar, pa —posterior adductor muscle scar, rop —rostellum pad, sam —small anterior muscle scar, ss —support structure scar, pap —posterior adductor organic pad, ovv —organic ventral valve.