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.