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Spondyloarthropathy is the term applied to a form of arthritis with sentinel alteration of the spine, in the form of syndesmophytes and zygapophyseal joint erosions.1–3 Although a single zygapophyseal joint can be damaged by pyogenic or rarely by a granulomatous infection, the only known cause of multiple zygapophyseal joint erosions is spondyloarthropathy,1,2 as previously documented in the sauropod dinosaur Camarasaurus.4 Species susceptibility to spondyloarthropathy of the reactive arthritis variety has been clearly documented in non-human primates, identical in character, infectious agent involvement, and response to treatment to that found in humans.5
Observation of syndesmophytes and zygapophyseal joint fusion in cetacea (for example, dolphins)6 stimulated a systematic survey of cetacean collections for evidence of spondyloarthropathy. That survey exposed a blue whale (Balenoptera musculus) at the American National Museum of Natural History (Washington, DC) (USNM 124326) with erosions of zygapophyseal joints of vertebrae 11–14 (fig 1). This specimen, collected in Newfoundland, Canada by F Leucas, contrasts with another sign of spondyloarthropathy,1,2,7 sacroiliac joint fusion, present in the mouse-like marsupial Antechinomys laniger (common name, kultarr) at the Center for Biodiversity, Illinois Natural History Survey (Champaign, IL) (UIMMH 39301).
The phylogenetic spectrum of spondyloarthropathy is now extended from the largest mammal (weighing up to 190 000 kg) that ever lived to one of the smallest, the latter weighing in at less than a twentieth of a kilogram. With apologies to Walt Disney, A whale of a tale and its all true.
Appreciation is expressed for facilitation of collection access by Charles Potter and Jeff Saunders.