The second area where Middle Ypresian sediments are preserved and serration development can be seen, is north of the Emba River, in northwestern Kazakhstan.

This is a most beautiful, but inhospitably arid area of grasslands and seasonally-dry salt lakes. Cretaceous chalk and Tertiary marls are exposed in long cliff sections. The Early Eocene (Ypresian) marls contain laterally traceable bands of grey organic-rich clays with fish debris — mainly coprolites and bones, but with some sharks teeth.

Fig. 6 - Chronostratigraphy

One of the authors (DJW) visited this area and was able to collect the clay horizons, bed by bed. These are labeled 1 to 5 on the section and these arbitrary designations will be referred to as 'Bed' or 'Level' during this discussion⁸. The results (Fig 7 & 8) were that three different morphologies of Otodus/Carcharocles were found.

Fig. 7 & 8 - Kazakhstan Laterals From left to right O. obliquus, O. obliquus var. mugodzharicus and C. aksuaticus

In Bed 1, only teeth of Otodus obliquus were found. Beds 2 and 3 yielded few teeth, but Bed 4 yielded Otodus teeth with fine, indistinct or irregular serrations, herein termed O. obliquus var. mugodzharicus. In Bed 5, all the Otodus/Carcharocles teeth were serrated, perhaps excepting the tip of the crown. These we are calling C. aksuaticus.

All the Otodus/Carcharocles teeth collected were fairly small. These are smaller (50-60% the size) than, and complement, those from the Potomac, where a few, very slightly serrated teeth, are found, but cannot be comfortably ascribed to O. o. mugodzharicus at this time.

Interestingly, the most common sharks' teeth in the assemblage were from the usually rare species -- Xiphodolamia. This is probably a specialized cephalopod predator, suggesting a rather "strange" paleoenvironment. Batoids are very uncommon, furthur suggesting fairly deep water (mid/outer shelf).