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Description

Chlanidota (Pfefferia) invenusta,
new species
Figs. 24-26; Table 9

 

Chlanidota densesculpta (partim)—Dell, 1990:183, fig. 306.

 

Description.—Shell (Fig. 23) thick, sol­id, ovate-rounded. Protoconch, 1 ½ upper teleoconch whorls eroded. Teleoconch with ≈ 4 strongly convex whorls. Shoulder rounded. Suture adpressed, deep, wide, nearly channeled. Subsutural rim well pronounced, slightly convex. Spiral sculpture of weak cords (25-40 on body whorl, 5-14 on penultimate whorl) constant in width adapically, of variable width and prominence below shoulder. Axial sculpture lim­ited to fine, often indistinct growth lines. Aperture of moderate height (0.60-0.72 SL), elongate-ovate, deflected from the shell axis by 17-21°. Outer lip thin to thick, evenly rounded, weakly reflected in thick-lipped adults. Outer lip thin and evenly rounded, slightly deflected. Columella short (< ½ AL), straight, with strong, long si­phonal fold, siphonal region slightly elon­gated, inflected in some specimens. Callus narrow, thin to thick overlying parietal re­gion, siphonal fasciole, white when thin, greenish-gray at margins when thick. Si­phonal notch broad, dorsally recurved, with straight columellar, rounded apertural mar­gins forming borders of fasciole. Apertural margin of siphonal notch gives rise to weak ridge margin. Shell color grayish white. Periostracum (Fig. 24D) light-olive, mod­erately thick, tightly adherent to shell sur­face, forming very low, densely spaced la­mellae along the growth lines. Operculum (Fig. 23D, H, J, L) large (0.47-0.62 AL), oval, light to dark brown, apical end round­ed to weakly tapering, nucleus, terminal, ro­tated nearly perpendicular to long axis of operculum, posterior edge smooth (Fig. 23d, J), or with weakly (Fig. 23H) to strongly (Fig. 23L) feathered lamellae.

 

Ultrastructure.—(Fig. 25C) Outer pris­matic layer comprises spiral cords, variable in thickness, ranging from ≈80 μm to ≈140 μm, depending on strength of cord. Middle layer comarginal (≈120 μm). Inner layer radial, reaching ≈50 μm in thickness, is the last layer to be deposited, may not be evident in immature specimens (Fig. 25C).

 

Anatomy.—The gross anatomy of paratype 1 was examined, and found to be sim­ilar in all details to that of C. (P.) palliata with the exception that the animal lacked eyes. Radular ribbon (Fig. 24A–B) long, 13.6 mm (0.54 AL), ≈760 μm wide (0.030 AL), triserial, consisting of ≈80 rows, 6 of which are nascent. Rachidian teeth with arched base, straight lateral sides, 3 large, robust cusps, central cusp slightly larger that flanking cusps. Small intermediate serration present between central cusp and right flanking cusp of one specimen. Lateral teeth with 3 cusps, as in genus.

 

Type locality.—South Georgia Island, 53°31'12"S, 37°50'54"W, in 1267-1599 m (R/V Islas Orcadas, Sta. 7).

 

Type material.—Holotype, USNM 881782, paratypes 1-9, USNM 880280, all from the type locality.

 

Material examined.—South Georgia: R/V Islas Orcadas, Sta. 7, 53°31'12"S, 37°50'54"W, 1267-1599 m, 11 May 1975, Holotype, USNM 881782, paratypes 1-9, USNM 880280, 17 shells, USNM 901684; STa. 27, 53°34.9'S, 36°47.8'W, 448-872 m, 17 May 1975, 1 specimen, USNM 901685; R/V Eltanin: Sta. 731, 53°35'S, 36°28'W, 796-824 m, 11 May 1975, 13 specimens, USNM 896048; Sta. 734, 53°23'S, 37°11'W, 1299-1400 m, 11 May 1975, 4 shells, USNM 870389, 8 specimens, USNM 896049.

 

Distribution.—Known only from the northwestern coast of South Georgia (Fig. 25). Living material was collected at depths ranging from 448 to 1599 m.

 

Etymology.—invenustus (Lat.)—unat­tractive.

 

Remarks.—Chlanidota (Pfefferia) inven­usta may be distinguished from the other species in the subgenus Pfefferia by its more inflated shell, with a stepped rather than conical spire, more numerous and finer spiral cords, a broader, more rounded ap­erture, and an operculum in which the feathering along the posterior edge is much narrower to entirely absent. Some speci­mens superficially resemble Chlanidota densesculpta, but may be distinguished on the basis of their larger operculum, thicker shell, more rounded and stepped spires, and proportionally smaller, more rounded, and more deflected apertures.

 

The nine paratypes collected with the ho­lotype exhibit some variation in shell out­line and the number of spiral cords. Smaller specimens tend to have more rounded shells, while the number of spiral cords does not correlate with shell size. Opercula of the smallest specimens are yellow and translucent, and clearly show that the ter­minal nucleus is coiled, as in Neobuccinum.”

 

(Harasewych & Kantor, 1999:289-291)

 

Table 9.—Measurements of shell characters of the type series of Chlanidota (Pfefferia) invenusta, new species.

 

 

                                                                                                                                                                                                                     
 

Character

 
 

Holotype

 
 

Paratype 1

 
 

Paratype 2

 
 

Paratype 3

 
 

Paratype 4

 
 

Paratype 5

 
 

Paratype 6

 
 

Paratype 7

 
 

Paratype 8

 
 

Paratype 9

 
 

Mean

 
 

σ

 
 

Shell Length (SL)

 
 

38.3

 
 

39.6

 
 

32.6

 
 

38.6

 
 

31.8

 
 

31.0

 
 

36.0

 
 

26.5

 
 

22.2

 
 

19.0

 
 

31.6

 
 

7.1

 
 

Body Whorl Length (BWL)

 
 

31.6

 
 

31.9

 
 

27.3

 
 

30.7

 
 

25.8

 
 

26.3

 
 

30.3

 
 

22.2

 
 

18.7

 
 

16.3

 
 

26.1

 
 

5.5

 
 

Shell Width (SW)

 
 

26.4

 
 

27.2

 
 

23.4

 
 

25.6

 
 

22.9

 
 

22.0

 
 

25.6

 
 

17.4

 
 

16.0

 
 

14.4

 
 

22.1

 
 

4.6

 
 

Aperture Length (AL)

 
 

24.6

 
 

25.0

 
 

21.9

 
 

23.2

 
 

19.0

 
 

20.1

 
 

22.0

 
 

18.2

 
 

15.6

 
 

13.7

 
 

20.3

 
 

3.7

 
 

Operculum Length (OL)

 
 

12.4

 
 

12.2

 
 

10.2

 
 

-

 
 

11.7

 
 

11.7

 
 

10.5

 
 

8.8

 
 

8.0

 
 

7.2

 
 

10.3

 
 

2.0

 
 

BWL/SL

 
 

0.82

 
 

0.81

 
 

0.84

 
 

0.80

 
 

0.81

 
 

0.85

 
 

0.84

 
 

0.84

 
 

0.84

 
 

0.86

 
 

0.83

 
 

0.02

 
 

AL/SL

 
 

0.64

 
 

0.63

 
 

0.67

 
 

0.60

 
 

0.60

 
 

0.65

 
 

0.61

 
 

0.69

 
 

0.70

 
 

0.72

 
 

0.64

 
 

0.04

 
 

SW/SL

 
 

0.70

 
 

0.69

 
 

0.72

 
 

0.66

 
 

0.72

 
 

0.71

 
 

0.71

 
 

0.67

 
 

0.72

 
 

0.76

 
 

0.70

 
 

0.03

 
 

OL/AL

 
 

0.50

 
 

0.49

 
 

0.47

 
 

-

 
 

0.62

 
 

0.58

 
 

-

 
 

0.48

 
 

0.51

 
 

0.53

 
 

0.53

 
 

0.06

 
 

Number of spiral cords

 
 

 
 

 
 

 
 

 
 

 
 

 
 

 
 

 
 

 
 

 
 

 
 

 
 

Penultimate whorl

 
 

15

 
 

14

 
 

16

 
 

19

 
 

12

 
 

11

 
 

?

 
 

8

 
 

8

 
 

5

 
 

12

 
 

4.5

 
 

Body whorl

 
 

32

 
 

26

 
 

25

 
 

40

 
 

24

 
 

29

 
 

29+

 
 

29

 
 

38

 
 

27

 
 

29.9

 
 

5.3

 
 

No. whorls

 
 

3+

 
 

3++

 
 

3+

 
 

3++

 
 

3+

 
 

3+

 
 

3+

 
 

2++

 
 

2++

 
 

2+

 
 

 
 

 
 

Trusted

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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