Baculites sp weak flank ribs Cody Shale Wyoming

A lower jaw (BHMNH 5331) occurs inside the adoral end of a weathered fragment of a body chamber of Baculites sp. (weak flank ribs) (Fig. 13.15, Table 13.1). The body chamber fragment is 111.0 mm long with a maximum whorl height of 33.8 mm. The long axis of the jaw is oriented at an angle of 70° with the long axis of the body chamber. The anterior end of the jaw points slightly backward against the ventral (?) side of the shell. The jaw is folded along the symphysis so that the two wings are perpendicular to each other, with the right wing splayed out across the opening.

Baculites Smooth

Fig. 13.12 Steinkerns of parts of the body chambers of Baculites sp. (smooth), Pierre Shale, South Dakota, with lower jaws inside. A-C. BHMNH 5496, microconch. A. Right lateral view. XI. B. Dorsal view. XI. C. Close-up of the lower jaw, dorsal side of the shell on top. The radula (arrow) occurs at the anterior end of the jaw between the two wing tips. X1.5. D-F. BHMNH5497, microconch. D. Left lateral view. X1. E. Ventral view. X1. F. Close-up of the lower jaw (arrow), with the left side of the aptychus preserved in the ventral half of the shell, coated. X1.5.

Fig. 13.12 Steinkerns of parts of the body chambers of Baculites sp. (smooth), Pierre Shale, South Dakota, with lower jaws inside. A-C. BHMNH 5496, microconch. A. Right lateral view. XI. B. Dorsal view. XI. C. Close-up of the lower jaw, dorsal side of the shell on top. The radula (arrow) occurs at the anterior end of the jaw between the two wing tips. X1.5. D-F. BHMNH5497, microconch. D. Left lateral view. X1. E. Ventral view. X1. F. Close-up of the lower jaw (arrow), with the left side of the aptychus preserved in the ventral half of the shell, coated. X1.5.

Cody Shale

Fig. 13.13 Steinkerns of parts of the body chambers of Baculites sp. (smooth), Pierre Shale, South Dakota, with lower jaws inside. A-C. BHMNH 5146, microconch. A. Right lateral view. X1. B. Dorsal view. X1. C. Close-up of the lower jaw with the right side of the aptychus preserved, dorsal side ofthe shell on top. X1.5. D-F. BHMNH5495, microconch. D. Left lateral view. X1. E. Ventral view. X1. F. Close-up ofthe lower jaw with the right side ofthe aptychus preserved, dorsal side ofthe shell on top, coated. X1.5.

Fig. 13.13 Steinkerns of parts of the body chambers of Baculites sp. (smooth), Pierre Shale, South Dakota, with lower jaws inside. A-C. BHMNH 5146, microconch. A. Right lateral view. X1. B. Dorsal view. X1. C. Close-up of the lower jaw with the right side of the aptychus preserved, dorsal side ofthe shell on top. X1.5. D-F. BHMNH5495, microconch. D. Left lateral view. X1. E. Ventral view. X1. F. Close-up ofthe lower jaw with the right side ofthe aptychus preserved, dorsal side ofthe shell on top, coated. X1.5.

Table 13.1 Measurements ofthe whorl cross section and lower jaws o/Baculites/Pseudobaculites from the Pierre Shale, Cody Shale, Lewis Shale, Mooreville Chalk, and Niobrara Formation. Abbreviations: M/m = macroconch/microconch; WW = whorl width; WH = whorl height; W = width of wing as measured perpendicular to the symphysis, irrespective of convexity; L = length of wing measured parallel to the symphysis; 2W/L = ratio of jaw width to jaw length; 2W/WW = ratio of jaw width to whorl width; L/WH = ratio of jaw length to whorl height; *=estimate due to poor or incomplete preservation. All measurements in millimeters.

Table 13.1 Measurements ofthe whorl cross section and lower jaws o/Baculites/Pseudobaculites from the Pierre Shale, Cody Shale, Lewis Shale, Mooreville Chalk, and Niobrara Formation. Abbreviations: M/m = macroconch/microconch; WW = whorl width; WH = whorl height; W = width of wing as measured perpendicular to the symphysis, irrespective of convexity; L = length of wing measured parallel to the symphysis; 2W/L = ratio of jaw width to jaw length; 2W/WW = ratio of jaw width to whorl width; L/WH = ratio of jaw length to whorl height; *=estimate due to poor or incomplete preservation. All measurements in millimeters.

Specimen M/m

WW

WH

WW/WH

W

L

2W/L

2W/WW L/WH

Baculites sp. (smooth), Pierre Shale, South Dakota

BHMNH 5143 M

25.8*

33.2

0.78*

11.3

26.0*

0.87*

0.88

0.78*

5144 m

17.8

27.0

0.66

8.4

20.8

0.81

0.94

0.72

5146 m

18.8

28.4

0.66

9.8

25.0*

0.78*

1.04

0.88*

5147 m

22.6

32.4

0.70

10.2

25.2*

0.81*

0.90

0.75*

5148 m

21.9

31.4

0.70

10.2

26.3

0.78

0.93

0.86

5491 M

30.1

37.8

0.80

14.4

-

-

0.96

-

5494a M

28.1

41.1

0.68

13.2

34.5

0.76

0.94

0.87

5496 m

19.1

27.4

0.70

9.2

27.0*

0.68*

0.96

0.98

5497 m

16.0

22.2

0.72

7.8

-

-

0.98

-

5495 m

17.2

25.3

0.68

8.5

21.2

0.80

0.99

0.81

AMNH 47109 M

26.9

36.2

0.74

12.9

37.2

0.69

0.96

1.03

51329 m

22.8

30.4

0.75

9.2*

25.1*

0.73*

0.81*

0.82*

Baculites sp. (weak flanks ribs), Cody Shale, Wyoming

Baculites sp. (weak flanks ribs), Cody Shale, Wyoming

BHMNH 5331 26.6 33.8

0.79

12.5

33.2

0.75

0.94

0.98

Baculites sp. (smooth and weak flank ribs), Mooreville Chalk, Alabama (selected specimens)

BHMNH 5331 26.6 33.8

0.79

12.5

33.2

0.75

0.94

0.98

Baculites sp. (smooth and weak flank ribs), Mooreville Chalk, Alabama (selected specimens)

BHMNH 5406

15.8

38.6

0.82

5407

11.7

27.5*

0.85*

5408

9.9

21.5*

0.92*

5409

13.3

31.5*

0.84*

5410

12.1

27.2*

0.89*

5484

11.8

30.6

0.77

5450

6.4

15.2*

0.84*

5150

17.2

-

-

AMNH 51293

13.3

30.6*

0.87*

51316

13.8

-

-

Baculites sp., Niobrara Formation, Kansas

FHSM 968:1

10.2

20.1*

0.51*

Baculites compressus or B. cuneatus, Pierre Shale, South Dakota

BHMNH 5498

7.9

19.5

0.81

Baculites compressus, Pierre Shale, South Dakota

AMNH 51885

17.2

31.0

0.55

51880

13.9

24.9

0.56

51865

15.5

27.1

0.57

51879

19.6

40.4

0.48

51871

15.7

26.9

0.58

51872

16.3

30.0

0.54

51886

19.3

36.1

0.53

51887

16.1

30.3

0.53

Specimen M/m

WW

WH

WW/WH

W

L

2W/L 2W/WW L/WH

Baculites cuneatus, Pierre Shale, South Dakota

AMNH 51866

24.6

50.2

0.49

51873

16.8

32.4

0.52

50422

15.2

26.2

0.58

BHMNH 5498

25.2

40.6

0.62

Pseudobaculites

natosini,

Lewis Shale, Wyoming

BHMNH 5501

25.8

50.1*

1.03*

AMNH 51328

26.3

59.0

0.89

BHMNH 5502

23.6

52.8

0.89

BHMNH 5500

28.1

-

-

USNM 458243

31.9

87.3

0.36

458241

60.0

141.0

0.43

458239

72.0

152.0

0.48

Some of the rugose ornament of the aptychus is preserved on the left wing. The calcite is approximately 0.4 mm thick. Most of the aptychus is missing on the right wing and there is a dark brown surface comprising the underlying chitinous layer. This layer is broadly convex and is covered with fine ridges spaced at intervals of 300 |im and very fine lines spaced at intervals of 80 |im, both of which parallel the lateral and posterior margins.

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