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Re: New Ediacaran quilted organism? (OT)



This was presented last month at the North American Paleontology Convention in 
Halifax. The implication is that the organic part is the walls, which allowed 
water to flow through the open parts, perhaps doing something like filter 
feeding, and that the whole structure was only one layer deep. But all in all, 
it's Ediacara and it's weird. People were scratching their heads, but they 
seemed to be taking it seriously. 

At 9:26 AM +1200 7/20/05, Christopher Taylor wrote:
>Not dinosaurs, but I was wondering if anyone would like to comment on this
>out today:
>
>Xiao, S., B. Shen, C. Zhou, G. Xie & X. Yuan. 2005. A uniquely preserved
>Ediacaran fossil with direct evidence for a quilted bodyplan. Proceedings of
>the National Academy of Sciences of the USA 102: 10227-10232.
>
>"Ediacara fossils are among the oldest known macroscopic and complex life
>forms. Their bodyplan, ecology, and phylogenetic affinities have been
>controversial. On the basis of taphonomic observations, Seilacher
>[Seilacher, A. (1989) Lethaia 22, 229-239] proposed that the core elements
>of the Ediacara biota, the vendobionts, were constructed with serially or
>fractally arranged quilts or tube-like units. However, anatomy of quilt
>walls has been rarely reported, because most Ediacara fossils are preserved
>as casts and molds in siliciclastic rocks with inadequate morphological
>resolution. Here, we report an Ediacara form, uniquely preserved in situ and
>in three dimensions with its organic walls cast by early diagenetic calcite,
>from bituminous limestone of the 551- to 542-mega-annum Dengying Formation
>of South China. Despite diagenetic tampering, serial sections show that the
>Dengying form consists of biserially arranged, tube-like quilts, each with
>two vertical side walls, a floor, a roof, and an open distal end.
>Three-dimensional morphological complexity of the Dengying form excludes a
>microbial interpretation but is broadly consistent with vendobionts. Unlike
>classic frondose vendobionts sensu Seilacher, however, the Dengying form
>probably lacked a smooth margin and had distally open quilts. It probably
>lived procumbently at or near the water-sediment interface and shows
>evidence for substrate utilization. Despite its uncertain phylogeny,
>ontogeny, and functional biology, the Dengying form adds to Ediacaran
>biodiversity, places key constraints on the ecology and extinction of
>Ediacara organisms, and points to the need to explore an alternative
>taphonomic window for Ediacara biology."
>
>It's those 'open distal ends' that are bothering me. The 'quilts' are filled
>with exactly the same sediment as the surrounding matrix, and the authors
>interpret them to be hollow, with just the 'struts' comprising the actual
>organism. To be honest, the figures look a heck of a lot like inorganic
>structures to me, but the authors argue against it on the basis of their not
>overlapping, and adjacent branches not encroaching on one another.
>Any thoughts?

-- 
Jeff Hecht, science & technology writer
jeff@jeffhecht.com
Boston Correspondent: New Scientist magazine
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