Blue Candle, Blue Myrtle Cactus, or Garambullo (Myrtillocactus geometrizans) is a large, white-flowered, columnar, treelike cactus native to Mexico. Because of their attractive, blue-green coloration, Blue Candle cacti are popular additions to cactus and xeriscape gardens here in Arizona. One of the smaller and definitely weirder-looking cultivated forms available in nurseries is M. geometrizans crest 'Dinosaur Back'.
Like other plants and cacti, Blue Candles can suffer from fasciation, abnormal proliferative growth of the apical meristems (growing tips) causing cresting and other bizarre growth forms.
The narrow crests of crested Blue Candles do look a little bit like a dinosaur's back, especially like that of a Stegosaurus (Stegosaurus spp.), but I think that these strange-looking, crested cacti look even more like some type of blue-green coral.
The landscape designers at Quail Botanical Gardens in Encinitas, California cleverly used the crested Blue Candle's coral-like appearance in their truly remarkable Under the Sea Garden, an all cactus and succulent recreation of a coral reef.