The rise of bilaterians

  title={The rise of bilaterians},
  author={Gary P. Freeman},
  journal={Historical Biology},
  pages={114 - 99}
Recently Shen et al. have argued that the Ediacaran faunas from Avalon-Charnwood [580–560 million years ago (MA)], the White Sea-Flinders Range (560–550 MA) and Namibia (550–543 MA) occupied the same morphospace even though these faunas differed in species composition, ecology, biogeography and age. The traits they used to characterise these faunas could not distinguish between important promorphological features such as radial vs. bilaterian and unitary vs. colonial animals. Their… Expand
The rise of bilaterians: a few closing comments
Although Vernanimalcula is a fossil, the purported germ layers of Vern animalcula are of diagenetic origin and there is no morphological evidence in support of its bilaterian affinity, so it is inappropriate to analyse Ediacara fossils using “promorphologies” of extant animals. Expand
The rise of bilaterians: a reply
In the March–June 2009 issue of Historical Biology, Freeman (2009) published a critique of our morphological and phylogenetic analyses of Ediacara fossils (Shen et al. 2008; Xiao and Laflamme 2009).Expand
Ancestral state reconstruction of ontogeny supports a bilaterian affinity for Dickinsonia
This study formalizes the connection between ontogeny in Dickinsonia—which grows by the addition of metameric units onto one end of its primary axis—with terminal addition, defined as growth and patterning from a posterior, subtermial growth zone, and concludes that terminal addition is a synapomorphy of bilaterian animals. Expand
A merciful death for the “earliest bilaterian,” Vernanimalcula
It is concluded that the structures key to animal identity are effects of mineralization that do not represent biological tissues, and that the conclusions of evolutionary studies that have relied upon the bilaterian interpretation of Vernanimalcula must be called into question. Expand
Ecospace Utilization During the Ediacaran Radiation and the Cambrian Eco-explosion
A theoretical ecospace is a multi-parameter system for classifying the ecological properties of organisms; because they are viewed in terms of their ecological and functional capabilities,Expand
Fossilized Nuclei and Germination Structures Identify Ediacaran “Animal Embryos” as Encysting Protists
It is demonstrated using synchrotron-based x-ray tomographic microscopy that the fossils have features incompatible with multicellular metazoan embryos, which represent an evolutionary grade in which palintomic cleavage served the function of producing propagules for dispersion. Expand
Life cycle evolution: was the eumetazoan ancestor a holopelagic, planktotrophic gastraea?
  • C. Nielsen
  • Biology, Medicine
  • BMC Evolutionary Biology
  • 2013
All the available information is strongly in favor of multiple evolution of non-planktotrophic development, and only the terminal addition theory is in accordance with the Darwinian theory by explaining the evolution through continuous series of adaptational changes. Expand
Comment on Xiao et al. (2009), response to: the rise of bilaterians
In this rejoinder to Xiao et al., I will concentrate on two issues: the methodology used by Shen et al. and the assertion that the data supporting the existence of crown-group sponges, cnidarians andExpand


The Avalon Explosion: Evolution of Ediacara Morphospace
A comprehensive quantitative analysis of these fossils indicates that the oldest Ediacara assemblage—the Avalonassemblage (575 to 565 Ma)—already encompassed the full range of Ediacar morphospace. Expand
THE EDIACARA BIOTA: Neoproterozoic Origin of Animals and Their Ecosystems
Present evidence suggests that the Ediacara biota included a mixture of stem- and crown-group radial animals, stem-group bilaterian animals, “failed experiments” in animal evolution, and perhaps representatives of other eukaryotic kingdoms. Expand
Functional and Ecological Aspects of Ediacaran Assemblages
Reference to fossil imprints of soft-bodied Ediacaran metazoans made by Hill and Bonney (1877, p. 757) recorded two of “those curious arrangements of concentric rings which have been supposed to beExpand
The enigmatic Ediacaran (late Precambrian) genus Rangea and related forms
Investigation of the preservation and structure of Rangea indicates that it was probably a colonial octocoral consisting of a large tapering primary polyp, or oozoid, and a number of leaf-shaped, conjoined fronds which bore the feeding polyps; it is suggested to belong to a group of early Ediacaran anthozoans which provide a fossil link between the still living Telestacea and Pennatulacea. Expand
Precambrian animal life: probable developmental and adult cnidarian forms from Southwest China.
The new observations reported in this paper indicate the existence of a diverse and already differentiated cnidarian fauna, long before the Cambrian evolutionary event. Expand
The problems and potential of using animal fossils and trace fossils in terminal Proterozoic biostratigraphy
Abstract Despite the discovery of soft-bodied megascopic fossils of late Neoproterozoic age at numerous localities world-wide, there has been slow acceptance of their potential for intercontinentalExpand
Evolutionary relationships within the Avalonian Ediacara biota: new insights from laser analysis
Abstract: We report new high-resolution laser scanning of the type material for the earliest, complex Ediacaran genera Charnia, Bradgatia, Charniodiscus and Ivesheadia from Charnwood, UK, and compareExpand
Ediacaran Biota on Bonavista Peninsula, Newfoundland, Canada
Abstract Newly found fossils in the Conception and St. John's groups of the Bonavista Peninsula considerably extend the known geographic distribution of the Ediacaran fossils in Newfoundland. TheyExpand
New data on Kimberella, the Vendian mollusc-like organism (White Sea region, Russia): palaeoecological and evolutionary implications
The taphonomic varieties of Kimberella provide new evidence of the animal's anatomy such as: shell morphology, proboscis, mantle, possibly respiratory folds and possibly musculature, stomach and glands. Expand
Abstract Carbonaceous compression fossils in shales of the uppermost Doushantuo Formation (ca. 555–590 Ma) at Miaohe in the Yangtze Gorges area provide a rare Burgess-Shale-type taphonomic window onExpand