Figure 12. Sequential micro CT slices through penetrative and non-penetrative Karethraichnus on costal fragments. All scale bars are 5 mm. (1) Karethraichnus that penetrates ~80% of the bone. This boring triggered a systemic response resulting in new bone growth and thickening of the shell beneath the boring.Top of each slice is the external (dorsal) surface. Base of each slice is the outer (ventral) surface (2). Karethraichnus that penetrates fully through the bone with a spur of new bone growth in a ring surrounding the boring on the inside surface. In each slice the area above the dashed line consists of bone that grew in response to the penetration of the parasite. In this example, the hole was not fully healed such as is the case in other examples such as in Figure 11.1. All scale bars 1 mm.
through the bone and into the healed patch form compound borings/bioclaustration structures (sensu Palmer and Wilson, 1988) and, to our knowledge, are unique within bone-hosted
trace fossils. The bioclaustration component is not part of the diagnosis or description of any ichnotaxon described herein because bioclaustration structures are pathological systemic