The early history of the metazoa—a paleontologist’s viewpoint

  title={The early history of the metazoa—a paleontologist’s viewpoint},
  author={Andrey Yu. Zhuravlev},
  journal={Biology Bulletin Reviews},
  • A. Zhuravlev
  • Published 14 October 2015
  • Geography, Environmental Science, Biology
  • Biology Bulletin Reviews
Successful molecular biology, which led to the revision of fundamental views on the relationships and evolutionary pathways of major groups (“phyla”) of multicellular animals, has been much more appreciated by paleontologists than by zoologists. This is not surprising, because it is the fossil record that provides evidence for the hypotheses of molecular biology. The fossil record suggests that the different “phyla” now united in the Ecdysozoa, which comprises arthropods, onychophorans… 

Origin and the Early Evolution of the Phylum Mollusca

  • P. Parkhaev
  • Geology, Geography
    Paleontological Journal
  • 2017
The paper gives an overview of the modern hypotheses on the origin of the phylum Mollusca and the formation of its main classes. The Cambrian stage of molluscan evolution is characterized based on

Early cephalopod evolution clarified through Bayesian phylogenetic inference

It is proposed that using a posteriori pruned maximum clade credibility trees help in assessing support for phylogenetic relationships among a set of relevant taxa, because they provide clade support values that better reflect the phylogenetic signal.

Renewed perspectives on the sedentary-pelagic last common bilaterian ancestor

The present review compares the main existing models and reconciles the sedentary model of an urbilaterian and the model of a larva-like lcba with a unified sedentary(adult)-pelagic(larva) model of the lCba.

The two phases of the Cambrian Explosion

Two phases are proposed of the Cambrian Explosion separated by the Sinsk extinction event, the first dominated by stem groups of phyla from the late Ediacaran to early Cambrian stage 4, ~513 Ma, and the second marked by radiating bilaterian crown group species of phylas from ~513″Ma and extending to the Ordovician Radiation.

Branching archaeocyaths as ecosystem engineers during the Cambrian radiation

The rapid origination and diversification of major animal body plans during the early Cambrian coincide with the rise of Earth's first animal‐built framework reefs. Given the importance of

Morphology and relationships of the enigmatic stenothecoid pan-brachiopod Stenothecoides—New data from the middle Cambrian Burgess Shale Formation

Bulk sampling of middle Cambrian carbonate units in the lower Burgess Shale Formation (Wuliuan) and the upper Wheeler Formation (Drumian) in Utah have yielded abundant silicified stenothecoids.

Ontogeny, morphology and pedicle attachment of stenothecoids from the middle Cambrian of North Greenland (Laurentia)

  • J. S. Peel
  • Environmental Science, Geography
    Bulletin of Geosciences
  • 2021
fossils in the Cambrian, but the adaptation to enclose the soft parts within two articulating shells is widespread in the Cambrian biota. Amongst arthropods, bradoriids and phosphatocopines are also

Sherry Xu EPS Senior Thesis

Major aspects of the Earth system, including climate, atmospheric oxygen, the strength of the biological pump, and export productivity from plankton communities, have varied dramatically through

Mitochondrial Genomes of Kinorhyncha: trnM Duplication and New Gene Orders within Animals

Gene order analysis reveals that gene arrangement specific of Priapulida may be ancestral for Scalidophora, Ecdysozoa, and even Protostomia.



The earliest history of the deuterostomes: the importance of the Chengjiang Fossil-Lagerstätte

The known diversity of Chengjiang deuterostomes are reviewed and it is argued that the vetulicolians and yunnanozoans represent very primitive deuterOSTomes, as well as new data to indicate that the yunncozoans are unlikely to be any sort of chordate.

A Supra-Ordinal Classification of the Brachiopoda

A new classification of the Brachiopoda is proposed to take into account recent advances in understanding of the anatomy, shell morphology, ontogeny and phylogeny of the phylum, and is divided into three subphyla, each typified by Recent species with early Palaeozoic ancestors and defined by easily identifiable synapomorphies.

Poriferan paraphyly and its implications for Precambrian palaeobiology

It is demonstrated, in accordance with previous molecular studies, that sponges are paraphyletic, and that calcisponge are more closely related to eumetazoans than they are to demosponges.

Are palaeoscolecids ancestral ecdysozoans?

It is concluded that previous interpretations in which palaeoscolecids occupy a deeper position in the ecdysozoan tree lack particular morphological support and rely instead on a paucity of preserved characters, bears out a more general point that fossil taxa may appear plesiomorphic merely because they preserve only plesiomorphies, rather than the mélange of primitive and derived characters anticipated of organisms properly allocated to a position deep within animal phylogeny.

Origin of the metazoan phyla: molecular clocks confirm paleontological estimates.

This work has analyzed 18 protein-coding gene loci and estimated that protostomes (arthropods, annelids, and mollusks) diverged from deuterostomes about 670 million years ago, and chordates from echinoderms about 600 million years old, consistent with paleontological estimates.

The phylogenetic position of the comb jellies (Ctenophora) and the importance of taxonomic sampling

The reconstructed topology is considered to represent the current best hypothesis of the interrelationships of these old lineages and morphological features supporting alternative hypotheses are discussed in the light of this result.

A Pikaia-like chordate from the Lower Cambrian of China

A single specimen of a Lower Cambrian chordate, Cathaymyrus diadexus, new genus and species, that is similar to Pikaia but predates it by about 10 million years (Myr).

Resolving the evolutionary relationships of molluscs with phylogenomic tools

Molluscs (snails, octopuses, clams and their relatives) have a great disparity of body plans and, among the animals, only arthropods surpass them in species number. This diversity has made Mollusca

How to make a protostome

Almost all new information about morphology and embryology fits the trochaea theory, and the predicted presence of a perioral loop of the blastoporal nerve ring has now been demonstrated in two annelids.

Cnidarian milestones in metazoan evolution.

It is suggested that paedomorphic events in descendants of this ancestor led to the array of diversity seen in the main extant animal phyla and can provide an integrative test of hypotheses of homologies and independent evidence of the evolutionary relationships among extant taxa.