Editing Phosphatization (section)

== Phosphate-only fossils==
In phosphatic fossils, the preservation is so fine that even some cellular structure has been preserved. The phosphatic microfossils of the [[Doushantuo Formation]], a fossil-rich [[Lagerstätten|lagerstätte]] of the [[Ediacaran]] period, about 590–565 Ma (megaannua; million years ago), display some of the most spectacular cellular-level preservation known from the geologic record. The fossils include what may be [[metazoan]] [[blastula]]s, possibly animal embryos at an early stage in cell division.

The Doushantuo Formation presents a classic example of phosphatic fossilization:{{long quote|date=February 2023}}
:'This high-resolution fossil bed is about 30% phosphate, present as the mineral [[fluorapatite]] [Ca<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>F]. Phosphatic beds within this deposit are [[grainstone]]s composed of 1- to 5-mm phosphoclasts. These derive from a phosphatic surface that formed on the sea floor, in the process of recrystallizing existing surface sediments. In addition to replacing carbonate sediments, soft tissues of metazoan embryos, larvae, adults, and algae also appear to have been mineralized. The phosphatized sediment crust was then broken into small fragments by heavy current activity and then redeposited and mixed in with adjacent lime muds.<ref>{{cite journal  |vauthors=Chen JY, Oliveri P, Li CW, etal |title=Precambrian animal diversity: Putative phosphatized embryos from the Doushantuo Formation of China |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=97 |issue=9 |pages=4457–62 |date=April 2000 |pmid=10781044 |pmc=18256 |doi=10.1073/pnas.97.9.4457 |url=http://authors.library.caltech.edu/9385/1/CHEpnas00.pdf |doi-access=free }}</ref> Careful acid baths etch away the limestone matrices, by slowly dissolving the carbonates, and reveal the phosphates that have replaced organic structures, in the manner that Dr. Chen describes. There are other means of fossilization represented in the Doushantuo Formation as well.

A refinement to viewing the internal structure of fossilized embryos uses specialized microscopic three-dimensional [[X-ray computed tomography]], a kind of micro CAT scan.<ref>{{cite journal  |vauthors=Donoghue PC, Bengtson S, Dong XP, etal |title=Synchrotron X-ray tomographic microscopy of fossil embryos |journal=Nature |volume=442 |issue=7103 |pages=680–3 |date=August 2006 |pmid=16900198 |doi=10.1038/nature04890 |bibcode=2006Natur.442..680D |s2cid=4411929 }}</ref><ref>[http://www.spacedaily.com/news/life-02zs.html X-ray computerized tomography application to phosphatic microfossils.]</ref>

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File:Sula figueroae holotype & paratype.jpg
File:Selected soft-bodied arthropods from the Spence Shale.jpg
File:Brachydelphis mazeasi specimen MUSM 887 (1).jpg
File:Aetomylaeus sp. from Bahía Inglesa Formation (4).jpg
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