TABLE 1. Summary of documented Recent xiphosurids with abnormalities.
| Reference and figure number (where given) | Abnormality | Species | Possible Cause |
| Packard (1870, figure 36). Refigured in Bateson (1894, figure 143), and Gudger (1935, no figure number) | Forked telson bifurcating at the last third of the sagittal length | Limulus polyphemus | Not stated |
| Osburn (1911, no figure number). Refigured in Gudger (1935, no figure number) | Double telson bifurcating at opisthosomal joint | Limulus polyphemus | Moulting |
| Gravier (1930, figure 1) | Forked telson bifurcating halfway sagittal length | Tachypleus sp. | Mechanical damaged during early development |
| Gudger (1935, no figure number) | Forked telson bifurcating in the last fifth of the sagittal length | Limulus polyphemus | Moulting |
| van der Meer Mohr (1935, figures 2–4) | Shortened processes, pretarsus and apotele of pushing legs | Tachypleus gigas (Müller, 1785) | Not stated |
| van der Meer Mohr (1935, figure 1) | Slit-like injury to posterior cephalothorax | Tachypleus gigas | Not stated |
| van der Meer Mohr (1941) (not figured) | Shortened processes, pretarsus and apotele of pushing legs | Tachypleus gigas | Predation or mating |
| van der Meer Mohr (1941) (not figured) | Curved telson | Tachypleus gigas | Predation or mating |
| van der Meer Mohr (1941) (not figured) | Removal and recovery of moveable spines | Tachypleus gigas | Predation or mating |
| Bursey (1977) (not figured) | Amputated legs (specific leg not stated) with thickened endocuticle | Limulus polyphemus | Not stated |
| Shuster Jr (1982, figure 14. A) | Double telson bifurcating at the opisthosomal joint | Limulus polyphemus | Mechanical injury |
| Shuster Jr (1982, figure 14. B–D) | Forked telsons. B and C bifurcate halfway along the sagittal length. D bifurcates at the distal section | Limulus polyphemus | Mechanical injury |
| Shuster Jr (1982, figure 14. E) | Enlarged axial spine | Limulus polyphemus | Mechanical injury |
| Shuster Jr (1982, figure 14. F) | Kink halfway along the telson with enlarged axial spine | Limulus polyphemus | Mechanical injury |
| Botton and Loveland (1989) (not figured) | Injured book gills, missing or short telsons | Limulus polyphemus | Predation by gulls, mechanical injury |
| Jell (1989, figure 1) | Left anterior cephalothoracic margin buckled. Left opisthosomal section with two fewer moveable spines than the right | Limulus polyphemus | Mechanical deformation post-moult. Rocks or waves |
| Brockmann (1990, figure 3) | Injured female posterior opisthosoma | Limulus polyphemus | Injuries from mating |
| Schaller et al. (2004) and Schaller et al. (2005) (not figured) | Loss of male pedipalp | Limulus polyphemus | Injuries from mating |
| Schaller et al. (2004) (not figured) | Hole through the dorsal cephalothoracic section | Limulus polyphemus | Predation by gulls |
| Duffy et al. (2006) (not figured) | Decayed lateral eyes, missing or damaged prosomal appendages | Limulus polyphemus | Disease, ageing, mechanical injury |
| Shuster Jr (2009, figure 1) | Butterfly spawning scars on female opisthosoma | Limulus polyphemus | Injuries from mating |
