ecdysozoa

An alternative concept, most widely accepted today, is the so-called Ecdysozoa hypothesis.

However, they show a number of important differences, and the arthropods are now placed separately among the Ecdysozoa.

Adoutte and coworkers were among the first to strongly support the Ecdysozoa.

The Ecdysozoa (also called cycloneuralia) are a grouping of protostome animals.

This group has been named Ecdysozoa.

The Ecdysozoa are protostomes, named after the common trait of growth by moulting or ecdysis.

All members of the Ecdysozoa are direct developers without a trochophore, and the cycloneuralians have terminal mouths.

Tardigrades form the phylum Tardigrada, part of the superphylum Ecdysozoa.

The non-panarthropod members of Ecdysozoa have been grouped as Cycloneuralia but they are more usually considered paraphyletic.

Nielsen has suggested that a possible solution is to regard Ecdysozoa as a sister-group of Annelida.

Besides arthropods and velvet worms, the priapulids are the only members of the Ecdysozoa which are relatively large in size.

On the other hand genetic studies place them as close relatives of the Platyhelminthes, the Ecdysozoa or the Lophotrochozoa.

This Ecdysozoa hypothesis is generally accepted today as the best supported evolutionary hypothesis for annelids and arthropods.

Furthermore, no distinctive apomorphies of Ecdysozoa are known; even moulting has recently been confirmed to occur outside the presumed clade.

The phylum is placed along with the Ecdysozoa clade of moulting organisms that include the Arthropoda.

In that study, Ecdysozoa also was not significant, using any method, when the flatworm sequence was included [ 3 ] .

Chaetognatha, Ecdysozoa, ichnofossils.

Before Ecdysozoa, one of the prevailing theories for the evolution of the bilateral animals was based on the morphology of their body cavities.

If nematodes cluster basally because of long-branch attraction, then the strongest support for Ecdysozoa should be obtained with the slowest evolving proteins.

They have also been described as a sister-group to the ecdysozoa, although as more characters are described a position closer to the priapulids becomes most probable.

Arthropods are now regarded as members of the Ecdysozoa ("animals that molt"), along with some phyla that are unsegmented.

The names alone - Tetraconata, Amoebozoa, Ecdysozoa, Oomycota, Neomeniomorpha - were overwhelming.

Current research in phylogenetics is uncovering the relationships between phyla, which are contained in larger clades, like Ecdysozoa and Embryophyta.

This sampling showed that the moulting animals form a clade, called the Ecdysozoa, a second protostomian superphylum sister to the Lophotrochozoa.

Originally, they were considered to be closely related to the annelids, grouped together as the Articulata, but newer studies place them among a group called the Ecdysozoa.