ristkülikulaadsed

Ristkülikulaadsed (Rectanguliformes) is a proposed, informal taxonomic grouping of animals that exhibit a predominantly rectangular or elongated body shape. This classification is not recognized within the standard Linnaean system of biological taxonomy but is sometimes used in informal descriptions or discussions, particularly in popular science contexts. Organisms that might be loosely grouped under this term often share a long, narrow, and somewhat flattened physique. Examples commonly cited include various species of worms, eels, and some elongated fish. The defining characteristic is the visual impression of a rectangular cross-section or overall form rather than any specific evolutionary lineage. It is important to note that such a grouping is based purely on morphology and does not reflect phylogenetic relationships. Animals with rectangular-like bodies may belong to vastly different phyla and classes. For instance, annelid worms and certain fish, despite both potentially being described as "ristkülikulaadsed," are evolutionarily distant. The term is primarily descriptive, highlighting a superficial resemblance in body plan that can be advantageous for certain ecological niches, such as burrowing or navigating through narrow spaces. Its lack of formal scientific standing means it is not used in rigorous biological research or classification.