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Fig. 2 in Extreme abundance of ammonoids in mass accumulations from the Late Devonian of the Moroccan Anti-Atlas

Fig. 2. Geological map of the study area, the Tafilalt and Maïder, with indications of the localities and the approximate placing of the basins and platforms (map modified after Frey et al. 2020).

Fig. 3 in Extreme abundance of ammonoids in mass accumulations from the Late Devonian of the Moroccan Anti-Atlas

Fig. 3. Typical ammonoids from lower, middle, and upper Famennian, Anti-Atlas, Morocco. A. Sample PIMUZ 37916, Oum El Jerane. B. Sample PIMUZ 37917. C. Sample PIMUZ 37918. D. Sample PIMUZ 37915. E. Sample PIMUZ 37919. In order to show various aspects of variation, we sometimes display more than one specimen per species. Scale bars 10 mm.

Fig. 5. A in Extreme abundance of ammonoids in mass accumulations from the Late Devonian of the Moroccan Anti-Atlas

Fig. 5. A scheme of shell measurements in Cheiloceras sp. from the lower Famennian of Madene El Mrakib, Anti-Atlas, Morocco (PIMUZ 37923). A. Polished sagittal section with the possible continuation of the ammonoid shown in grey. The photographed specimen is incomplete, parts of the body chamber are missing, and the specimen was probably larger as suggested by the reconstructed area. B. The body chamber shown without phragmocone; dashed lines indicate possible positions of the terminal aperture of the ammonoid. The diameter of the largest complete ammonoid from Madene sample and the diameter of the specimen without the body chamber are shown. C. The cross section showing the way the aperture opening was calculated. The number 4.2 is an average value from measurements of different sized specimens; a, apertural height; b, diameter of previous demi-whorl; conch diameter = a + b.

Fig. 1 in Extreme abundance of ammonoids in mass accumulations from the Late Devonian of the Moroccan Anti-Atlas

Fig. 1. Ammonoid mass occurrence (associated with brachiopods and orthocerids) from the lower Famennian of Madene El Mrakib, Morocco (prepared by Thomas Imhof, Trimbach); PIMUZ 37914.

Fig. 8 in Extreme abundance of ammonoids in mass accumulations from the Late Devonian of the Moroccan Anti-Atlas

Fig. 8. Estimating the number of missing specimens from Madene El Mrakib. A. Diameter plotted in log; the dashed line demarcates the possibly missing data based on the highest count at a diameter of 4 mm. B. Diameter plotted linearly; prepared specimens are marked by the blue field; the black dots mark the sums of prepared and crushed specimens; the orange field adds those specimens, which we might have missed entirely, either because of non-preservation or because they were overlooked during preparation; this is based on the regression line that was moved to the highest point of small specimens.

Fig. 4 in Extreme abundance of ammonoids in mass accumulations from the Late Devonian of the Moroccan Anti-Atlas

Fig. 4. Total volume of each sample and the volume of all ammonoids in the respective samples; including complete ammonoids and small ammonoids destroyed during preparation.

Fig. 8 in Dimorphism in tetragonitid ammonoid Tetragonites minimus from the Upper Cretaceous in Hokkaido, Northern Japan

Fig. 8. Two categories of the preservation pattern of the body chamber of tetragonitid ammonoid Tetragonites minimus Shigeta, 1989, from the Santonian, Yezo Group in the Haboro, Kotanbetsu, and Tappu areas, Hokkaido, Japan. A. MCM-W1549, complete or almost intact specimen, note the interiors of the body chamber filled with sparry calcite. B. MCM-W1555, incomplete specimen. In lateral (A1, B1) and median section (A2, B2) views. Arrowheads indicate the last septum. Scale bars 5 mm.

Fig. 7 in Dimorphism in tetragonitid ammonoid Tetragonites minimus from the Upper Cretaceous in Hokkaido, Northern Japan

Fig. 7. Scatter diagrams of four parameters versus shell diameter (D) of tetragonitid ammonoid Tetragonites minimus Shigeta, 1989, from the Santonian, Yezo Group in Hokkaido, Japan. A. H1/D (whorl height ratio). B. H2/D (ventral whorl height ratio). C. U/D (umbilical width ratio). D. B/D (whorl breadth ratio). Abbreviations: H1, whorl height; H2, ventral whorl height; U, umbilical width; B, whorl breadth.

Fig. 6 in Dimorphism in tetragonitid ammonoid Tetragonites minimus from the Upper Cretaceous in Hokkaido, Northern Japan

Fig. 6. The size distribution in a single horizon: outcrop HR109 (Santonian) in the Horotatesawa Creek of the Kotanbetsu area, Hokkaido, Japan.

Fig. 5 in Dimorphism in tetragonitid ammonoid Tetragonites minimus from the Upper Cretaceous in Hokkaido, Northern Japan

Fig. 5. Characteristics of ratio of numbers and size of dimorphism in tetragonitid ammonoid Tetragonites minimus Shigeta, 1989, from the Yezo Group in Hokkaido, Japan. The specimens treated here were collected from various stratigraphic levels in the Santonian in the Kotanbetsu, Tappu, and Haboro areas. A. The ratio of numbers of dimorphic pairs. B. Compilation of the size distribution in phragmocone diameter (PD). C. Comparative representation of the size of dimorphic pairs with indication of the phragmocone and body chamber.

Fig. 4 in Dimorphism in tetragonitid ammonoid Tetragonites minimus from the Upper Cretaceous in Hokkaido, Northern Japan

Fig. 4. Mature modifications recognised in tetragonitid ammonoid Tetragonites minimus Shigeta, 1989, from the Yezo Group in the Haboro, Kotanbetsu, Tappu, Nakagawa, Soya, and Yubari areas, Hokkaido, Japan. A, B. Changes in the shape of the body chamber: modification appeared at venter (A, MCM-W1591) and umbilicus (B, MCM-W1556). C. Shell thickening in the aperture, MCM-W1560. D. Septal crowding and increase in septal thickness, MCM-W1565; arrowhead indicates the last septum. Scale bars 2 mm.

Fig. 3 in Dimorphism in tetragonitid ammonoid Tetragonites minimus from the Upper Cretaceous in Hokkaido, Northern Japan

Fig. 3. Measurements of the conch geometries of tetragonitid ammonoid Tetragonites minimus Shigeta, 1989, from the Yezo Group in Hokkaido, Japan. A. Measured parameters on the specimens polished along the median plane. B. Measured ontogenetic changes of parameters on the specimens polished along the median plane, followed by the perpendicular plane. Abbreviations: B, whorl breadth; D, shell diameter; H1, whorl height; H2, ventral whorl height; PD, phragmocone diameter; U, umbilical width.

Fig. 1. A in Dimorphism in tetragonitid ammonoid Tetragonites minimus from the Upper Cretaceous in Hokkaido, Northern Japan

Fig. 1. A. Location map around studied areas in Hokkaido, Japan (inset shoving location of Yezo Group deposits). B. Generalized columnar section of the Santonian, Yezo Group in the Kotanbetsu area showing stratigraphic occurrence of dimorphic pairs of Tetragonites minimus Shigeta, 1989, and the selected stage-diagnostic mega-fossils. Double head arrows indicate the areas where the columnar sections were constructed. See Aiba (2019) for details of stratigraphy. Abbreviations: C., Creek; R., River.

Fig. 2 in Dimorphism in tetragonitid ammonoid Tetragonites minimus from the Upper Cretaceous in Hokkaido, Northern Japan

Fig. 2. Photographs of microconch and macroconch in lateral view of tetragonitid ammonoid Tetragonites minimus Shigeta, 1989, from the Santonian, Yezo Group, Horotatesawa Creek (A, outcrop HR001, and B, HR109) the Kotanbetsu area, Hokkaido, Japan. A. MCM-W1560 [m]. B. MCM-W1572 [M].

Fig. 10 in Virtual 3D modeling of the ammonoid conch to study its hydrostatic properties

Fig. 10. Model showing the shell orientation (φ) attained during neutral buoyancy for Maorites seymourianus models. White circle, center of buoyancy; asterisk, center of mass.

Fig. 9. A in Virtual 3D modeling of the ammonoid conch to study its hydrostatic properties

Fig. 9. A. Comparison of the model geometry for Maorites seymourianus defined by the Equation 3, and the closest logarithmic spiral (dotted line) found for these data (radius r = 88.97e-0.12Θ, determination coefficient R2 = 0.988). B. Close up of the initial whorls showing the slow increase in growth rate at the beginning of the ontogeny. The arrows indicate the differences in growth between the polynomial curve (solid arrows) and the logarithmic curve (dashed arrows).

Fig. 7 in Virtual 3D modeling of the ammonoid conch to study its hydrostatic properties

Fig. 7. The final simplified model of the conch of Maorites seymourianus. A. External elements of the conch in lateral view, the smooth areas emulate rectiradiate constrictions; the phragmocone in dark gray, the body chamber in grey. B. Internal elements within the phragmocone; the siphuncle in black, the septa in grey.

Fig. 3 in Virtual 3D modeling of the ammonoid conch to study its hydrostatic properties

Fig. 3. Example of the alignment process using only two specimens. Here it is graphed the radius against the angle showing the curves that describe the geometry of two specimens of Maorites seymourianus. A. The geometry of CPBA 16847 (reference) is defined by a function r = h(Θ) and its domain is [0 rad; 19.90 rad] in black (solid line), the geometry of CPBA 16838 is defined by a function r = i(Θ) and its domain is [0 rad; 20.42 rad] in grey. The normalization process consists of finding the results for an appropriate radius, in this case r = 20 mm (dotted line). Following, the difference in angle must be calculated (ΔΘ = 1.38 rad) and then the domain of the functions is adjusted accordingly. B. Curves after normalization, the difference in angle was applied to the domain of CPBA 16838, the new domain of the function is [1.38 rad; 21.80 rad]. Abbreviations: Θ, angle; r, radius.

Fig. 4 in Virtual 3D modeling of the ammonoid conch to study its hydrostatic properties

Fig. 4. Overview of the segment employed in this modeling method. A. Adoral view of the segment, the contour and measurements for this side were obtained from the CT-scan data. B. Lateral view of the segment showing the segment thickness (sgt = 10 mm). C. Adapical view of the segment. To model this side, the adoral contour was duplicated and then escalated according to the results from the equations in Table 1. Abbreviations: a, result for the angle in the adoral side for Equation (2); ah, aperture height; ad, adpical; ao, adoral; b, result for the angle in the adapical side for Equation (2); r, radius; sgt, segment thickness; wh, whorl height; ww, whorl width.

Fig. 6 in Virtual 3D modeling of the ammonoid conch to study its hydrostatic properties

Fig. 6. Illustrations showing the function of the relative offset and object offset. In this case, the object offset is a cube rotated in the y-axis. Segments are labeled in order of appearance. Note how each segment follows the transformation of the object offset. A. The relative offset has been modified to show each segment as a separate object. B. The relative offset with the correct value forming a unified structure.