Functional and Ecological Aspects of Ediacaran Assemblages

Jenkins, Richard

doi:10.1007/978-1-4899-2427-8_5

Cited by 150 publications

(166 citation statements)

References 69 publications

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“…Its preservation was explained by Jenkins (1985, p. 338) as being a result of limited compaction of the sandstone. Pflug (1970a) proposed, andJenkins (1992) followed, a similar way of reasoning, that the Namibian specimens were subject to early diagenetic silicification and it was this that enabled their three-dimensional preservation. Potentially this is possible, but in any event other interpretations are more likely in this particular case.…”

Section: Materials and Taphonomy Of Rangeamentioning

confidence: 95%

Possible ctenophoran affinities of the precambrian “sea‐pen” Rangea

Dzik

2002

Journal of Morphology

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The Namibian Kuibis Quartzite fossils of Rangea are preserved three-dimensionally owing to incomplete collapse of the soft tissues under the load of instantaneously deposited sand. The process of fossilization did not reproduce the original external morphology of the organism but rather the inner surface of collapsed organs, presumably a system of sacs connected by a medial canal. The body of Rangea had tetraradial symmetry, a body plan shared also by the White Sea Russian fossil Bomakellia and possibly some other Precambrian frond-like fossils. They all had a complex internal anatomy, smooth surface of the body, and radial membranes, making their alleged colonial nature unlikely. Despite a different style of preservation, the Middle Cambrian Burgess Shale frond-like Thaumaptilon shows several anatomical similarities to Rangea. The body plan of the Burgess Shale ctenophore Fasciculus, with its numerous, pinnately arranged comb organs, is in many respects transitional between Thaumaptilon and the Early Cambrian ctenophore Maotianoascus from the Chengjiang fauna of South China. It is proposed that the irregularly distributed dark spots on the fusiform units of the petaloid of Thaumaptilon represent a kind of macrocilia and that the units are homologous with the ctenophoran comb organs. These superficial structures were underlain by the complex serial organs, well represented in the fossils of Rangea. The Precambrian "sea-pens" were thus probably sedentary ancestors of the ctenophores.

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Section: Materials and Taphonomy Of Rangeamentioning

confidence: 95%

Possible ctenophoran affinities of the precambrian “sea‐pen” Rangea

Dzik

2002

Journal of Morphology

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“…The holdfast might have acted as a burrowing physa, embedded in the sediment in living condition. The holdfast cavity might have served as a hydrostatic skeleton and antagonist to the body wall musculature, whereas the basal pit might have been used for engulfing mud or sand-an anchoring strategy possibly also used by some Ediacaran (635-542 Mya) organisms (44).…”

Section: Significancementioning

confidence: 99%

Three Cambrian fossils assembled into an extinct body plan of cnidarian affinity

Han

Zhang

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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The early Cambrian problematica Xianguangia sinica, Chengjiangopenna wangii, and Galeaplumosus abilus from the Chengjiang biota (Yunnan, China) have caused much controversy in the past and their phylogenetic placements remain unresolved. Here we show, based on exceptionally preserved material (85 new specimens plus type material), that specimens previously assigned to these three species are in fact parts of the same organism and propose that C. wangii and G. abilus are junior synonyms of X. sinica. Our reconstruction of the complete animal reveals an extinct body plan that combines the characteristics of the three described species and is distinct from all known fossil and living taxa. This animal resembled a cnidarian polyp in overall morphology and having a gastric cavity partitioned by septum-like structures. However, it possessed an additional body cavity within its holdfast, an anchoring pit on the basal disk, and feather-like tentacles with densely ciliated pinnules arranged in an alternating pattern, indicating that it was a suspension feeder rather than a predatory actiniarian. Phylogenetic analyses using Bayesian inference and maximum parsimony suggest that X. sinica is a stemgroup cnidarian. This relationship implies that the last common ancestor of X. sinica and crown cnidarians was probably a benthic, polypoid animal with a partitioned gastric cavity and a single mouth/anus opening. This extinct body plan suggests that feeding strategies of stem cnidarians may have been drastically different from that of their crown relatives, which are almost exclusively predators, and reveals that the morphological disparity of totalgroup Cnidaria is greater than previously assumed.Xianguangia sinica | Chengjiangopenna wangii | Galeaplumosus abilus | ciliary suspension feeder | cnidarian stem group

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“…This end is opposite the front end of the animal during locomotion. Studies of compressed specimens have revealed structures interpreted as an anterior ventral mouth-pharynx that connects to an alimentary canal (the central groove of Shen et al 2008) and paired caecae that extend anterior laterally from the alimentary canal (Jenkins 1992;Dzik and Ivantsov 2002). Some of these fossils show characteristic wrinkles on part of their surface, indicating muscle contractions, muscle is indicative of bilaterian status (Runnegar 1982).…”

Section: Resultsmentioning

confidence: 99%

The rise of bilaterians

Freeman

2009

Historical Biology

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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 inappropriate assignment of symmetry properties led to the homogenisation of morphospace in these different faunas. Another way to examine shifts in morphospace involves sorting out radial vs. bilaterian and unitary vs. colonial genera in terms of their time of first appearance in the fossil record. While genera with both kinds of symmetry properties and unitary and colonial animals were present during the early Ediacaran, there was a large proportional increase in new bilaterian genera and a decrease in colonial genera beginning between 560-550 MA. The increase in bilaterians may have been associated with the ability to exploit food sources in and on the substrate of shallow water environments.

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Functional and Ecological Aspects of Ediacaran Assemblages

Cited by 150 publications

References 69 publications

Possible ctenophoran affinities of the precambrian “sea‐pen” Rangea

Possible ctenophoran affinities of the precambrian “sea‐pen” Rangea

Three Cambrian fossils assembled into an extinct body plan of cnidarian affinity

The rise of bilaterians

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