Tetraneuralia is a proposed clade of spiralian

bilaterian Bilateria () is a large clade of animals characterised by bilateral symmetry during embryonic development. This means their body plans are laid around a longitudinal axis with a front (or "head") and a rear (or "tail") end, as well as a left–r ...

s uniting the

phyla Phyla, the plural of ''phylum'', may refer to: * Phylum, a biological taxon between Kingdom and Class * by analogy, in linguistics, a large division of possibly related languages, or a major language family which is not subordinate to another Phy ...

Mollusca Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

and

Entoprocta Entoprocta (), or Kamptozoa , is a phylum (biology), phylum of mostly Sessility (zoology), sessile aquatic animals, ranging from long. Mature individuals are goblet-shaped, on relatively long stalks. They have a "crown" of solid tentacles whos ...

. belonging to Lophotrochozoa that groups

mollusks Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The num ...

, entoprocts and the extinct family Cupithecidae. The clade is supported by several morphological similarities between the two and has turned out to be important for evolution of

. It has been proposed by malacologists and zoologists when they observed that several morphological characteristics of entoprocts were clearly similar to those of mollusks. Both mollusks and entoprocts share a similar muscular system, the cuticle is the same in both, the hemolymph of the circulatory system is very similar, they have a tetraneuro nervous system with two pedal or ventral nerve cords. From this last characteristic the clade takes its name "tetraneuralia". Finally, entoprocts present similarities in the larval phases, they have a type of unique trochophore larva called "polyplacophora" and a complex larval apical organ.4 Molluscs are coelomate animals, in some cases equipped with shells, while entoprocts and cyclophores are acoelomates in habit. sessile. Although the synapomorphies are strong, few molecular studies have been able to support it, until a recent molecular study has been able to strongly support it and therefore this relationship could be correct. The Tetraneuralia clade constituted the most basal clade of Lophotrochozoa according to molecular analyses. First proposed in 2009 based on similarities between entoproct larvae and polyplacophoran molluscs,Wanninger A. (2009). Shaping the things to come: ontogeny of lophotrochozoan neuromuscular systems and the tetraneuralia concept. The Biological bulletin, 216(3), 293–306. https://doi.org/10.1086/BBLv216n3p293 it was recovered in 2019 in a

phylogenomic Phylogenomics is the intersection of the fields of evolution and genomics. The term has been used in multiple ways to refer to analysis that involves genome data and evolutionary reconstructions. It is a group of techniques within the larger fields ...

study by Marlétaz et al.

Phylogeny

In the most recent study, Tetraneuralia was recovered at the base of

Lophotrochozoa Lophotrochozoa (, "crest/wheel animals") is a clade of protostome animals within the Spiralia. The taxon was established as a monophyletic group based on molecular evidence. The clade includes animals like annelids, molluscs, bryozoans, and brach ...

References

Controversial taxa Bilaterian taxa Lophotrochozoa {{protostome-stub