The three "A. dunkeri" back vertebrae from Sussex have about thirty-five centimetres high neural spines or "processus spinosi", about as relatively tall as those of "Ichthyovenator". These show irregular rugosities on the upper third part. According to Ralph Molnar the two spines closest to the skull are ankylosed or fused. The single closest spine is only about two-thirds the height of the others and looks as it has broken off, while the spine behind partly overgrows the gap. This Molnar explained as a result of injury to a back frill, the wound later closing from behind. In 2003, Darren Naish gave a different interpretation, suggesting the gap was natural. He denied that the front two vertebrae were ankylosed but observed that the spines of eleventh and twelfth vertebrae were joined at the top. The spines are also transversely expanded above, with a width of about fifty-five millimetres. Naish also pointed out that Owen had noted the large depressions on the neural arch sides and had explained them as a result of pneumatisation, the first time this phenomenon would explicitly have been observed with a dinosaur. In 2006 however, it was reported that in 1837 Christian Erich Hermann von Meyer already had commented on this phenomenon with the Saurischia in general. The discovery of a back crest incorporating only two high vertebrae in "Concavenator", in 2010 provided corroboration that the short anterior "Altispinax" spine may be complete.