SiS: 8" Chinle ARIZONA CRYSTAL FOREST Petrified Wood Round - Crystalloxylon!

Description

This may be the single most interesting and collectible of all of the magnificent Arizona petrified wood slabs that we've offered this year!  The high contrast black with coffee colored preservation shows clear rays and rings and reveals an attractive, well polished and beautifully shaped cross section from an ancient conifer.  The specimen is lovely by any measure, but the real fascination in this piece is the story it has to tell.  It comes from an exposure in the vast southwestern US petrified wood deposits from the Chinle Formation dubbed the Crystal Forest.  The petrified wood exposed in the deposits in and around what is now the Petrified Forest National Park was first described scientifically over a century ago, creating one of the better known debates within the scientific community of paleobotanists!  I'll share a bit of that story further into the description, but the short version is that the famed petrified Araucaria has turned out to be several different species that better science and better tools now recognize.  My belief is that this specimen best conforms to one of the Crystalloxylon specimens described by Savidge in his survey paper published a few years ago (see below).  The name means "rock crystal wood" and is inspired by the Crystal Forest where the holotype still lies.  This same layer (just above the famed "rainbow" layer) is exposed in other valleys in the area on farms and ranches that still have small diggings that supply these pieces to collectors.  I'm including a microphoto that shows the well ordered structure of the radial files with relatively rounded tracheids and lumens which are the less than definitive criteria I can easily observe but do generally set Crystalloxylon apart from other conifers found in this vast forest.  But the truly distinguishing feature of Crystalloxylon requires even higher magnification to search for the characteristic "abundant display of mostly bi-seriate radial wall bordered pits".  While I have little doubt that the preservation in this exceptional specimen is more than fine enough to reveal them if they are there, my microscope won't zoom in that far which leaves the final confirmation in the hands of the new owner.
Due to a combination of procedural errors and failure to discern distinctions between different species, the name A. arizonicum is now considered nomen superfluum by scientists (a problem that gets all the more complicated since it is the legally adopted name of the state fossil of Arizona!)  Now, through more recent research, the Black Forest logs are called Pullisilvaxylon.  I have since found specimens that I believe are P. arizonicum due to the intercellular spaces I could observe in polished speicmens, which kind of makes it the closest thing to the original Knowlton A. arizonicum that exists and is a likely candidate for what the Arizona legislature may or may not get around to renaming one day for the state fossil!  If you're a species collector then I'd strongly encourage you to study this specimen and compare it to the 2007 paper by R. Savidge and draw your own conclusions.  This is actually the second log I have cut from this site and the distinguishing features in this one are not as easily spotted as they were in the first log so this may well be one of the other species he documents.   While the formalized debates are held in hallowed halls, my humble little shop takes pride in knowing this specimen is presented in it's full glory to tell its story to you and all who study it in the future.  The mirror finish coaxed from this nicely preserved and reasonably well silicified wood extends even to the characteristic mineral veins found in most Chinle specimens.  It's a fascinating and beautiful specimen sure to be a prized member of any collection!
While I am an educated scientist, I never pretend to be anything more than an amateur collector that loves working with these fascinating stones and I certainly would never try to pass myself off as a paleobotanist!  But I do enjoy a taste of the scientific side of a hobby that I'm primarily drawn to for the aesthetics.  I love the art at least as much as I do the ancient genetic story that each piece represents.  But sometimes the scientific story becomes sordid enough to overshadow the art, and this is one of those times!  In 1889 Frank Knowlton published a paper describing some black fossil logs recovered from Arizona.  He called the species Araucarioxylon arizonicum.  Two of the three pieces he used were housed in The Smithsonian while a third was lost to time.  Scandalously, when the research and specimens were examined more closely (presumably with better microscopes) the three pieces turned out to be different species.  As none was ever labeled to be the holotype (single reference specimen) for the new species Knowlton was describing, the pieces became syntypes of equal weight which means you can't really have A. arizonicum hanging around in the hallowed halls of academia because, well, the syntypes aren't actually the same thing!  The most comprehensive recent paper that tries to address and clean up the confusion was published by Rodney Savidge in 2007.  His paper attempts to explain and re-organize what is known of the now many species that have been identified in this vast forest of giant fossil trunks in the Arizona petrified forest.  One of the original three pieces was a Black Forest log that, in an apparent attempt to leave some naming credit with Knowlton, was called P. arizonicum.  While it is admittedly dangerous to try to identify a conifer based on cross section detail alone, the fact that it comes from the Black Forest combined with the intercellular spaces you see in the most zoomed in microphoto makes it uniquely match this conifer in Savidges summary paper.
The paper's title is something only a real paleobotanist could come up with:
"
Wood anatomy of Late Triassic trees in Petrified Forest National Park, Arizona, USA, in relation to Araucarioxylon arizonicum Knowlton, 1889
".
And you thought Sticks in Stones descriptions were wordy!!
The paper is easy to find online and provides good reference microphotos.  My identifications can never be considered definitive because I'm usually only studying them in cross section.  To truly distinguish closely related species it is sometimes necessary to prepare specimens cut from three different directions in the trunk (think of the faces of a cube).  While this level of analysis is rarely interesting (or practical) to the hobby collector, the paper does show how it becomes important to distinguish some of these ancient conifers and the confusion that can result when the analysis is spotty in the formal description of a species.  I'm relying on a couple of distinguishing features from the specimens Savidge describes to arrive at my conclusion (the black forest location and the intercellular spaces) but you are undoubtedly now armed well enough to begin your own exploration with this fascinating and exquisitely preserved fossil to see if you share the opinion!
If you're new to our shop the one thing you should expect is to see an unexpectedly glossy finish on each stone we prepare.  This complete round is a wonderful example of our work. It's been cut with a diamond saw and flat lapped on equipment I built myself to produce a mirror perfect polish unmatched by any of our many would-be imitators. The detail captured and revealed through the highly polished surface is just immaculate in most wood, slightly less dramatic in this variety. It's easily some of the most interesting wood to be found anywhere and we've prepared it to be all that it can be! It's a truly special find and we won't likely have a lot more so get a piece for your collection while it's available!
This is a slab from the center of the log and measures about 8 3/8" x 6 3/4" across the polished face and is cut about 0.42" thick.  Weight is 1.44 lbs.
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