neuroanatomy and the body plan paradox.
"We think that as an early deuterostome
this may represent the primitive beginnings of a very diverse range of species, including ourselves," study co-author Simon Conway Morris from the University of Cambridge, said in a (http://www.cam.ac.uk/research/news/bag-like-sea-creature-was-humans-oldest-known-ancestor) statement .
The four new laboratory sequences (Mga lab, Oed lab, Sma lab, and Vpu lab) presented three residues that are characteristic of PG-1 proteins in deuterostomes
and protostomes, Ala29, Asn41, and Thr43 (Fig.
A newly described group of primitive soft-bodied deuterostomes
, called vetulocystids, bears similarities to some of the bizarre early echinoderms.
Most animal phyla belong to one of two groups of bilaterians: the protostomes or deuterostomes
. Their distinguishing characteristic is whether, during gastrulation, the invagination of the gut eventually will become the mouth (protostomes) or the anus (deuterostomes
From the basic bilaterian plan, two developmental groups of organisms evolved namely deuterostomes
(echinoderms and chordates) and the protostones (almost everything else).
For example, humans are included in the following nested clades (using the informal names): eukaryotes, animals, deuterostomes
, vertebrates, gnathostomes, tetrapods, amniotes, mammals, eutherians, primates, monkeys, apes, and great apes (see Dawkins, 2004 for more information on the ancestry of humans).
Could it be that the ancestor of the deuterostomes
was a bottom-feeding dweller in the dark?
Despite the geographic and chronological distance, both sites have some genera in common and were dominated by arthropods; differing mainly in the rarity of deuterostomes
(a chordate and a crinoid have been found recently, H.X., pers.
In protostomes, as well as in deuterostomes
, the first cleavages initially result in the separation of the cells of the presumptive ectodermal and endodermal germ layers.
Acoelomorph flatworms are deuterostomes
related to Xenoturbella.
coronarius has a body that is symmetric and is characteristic of deuterostomes
-- the ancestor of all creatures in the animal kingdom's major group.