Implications of Spare Parts

A fossil skeleton cast of the house-cat-sized mammal Didelphodon vorax graces the new exhibit at the Smithsonian’s National Museum of Natural History.

The subject of a previous post, this exhibit, titled The Last American Dinosaurs, offers a glimpse of the flora and fauna that were part of the complex ecosystem of the Hell Creek Formation during the last couple of million years of the Cretaceous period.  D. vorax, the largest mammal living at the time, was a member of the most diverse and abundant of mammalian groups in Late Cretaceous North America – the metatherians.  This group, originally named by Thomas Huxley in 1880, includes “all mammals more closely related to living marsupials (such as kangaroos and opossums) than to living placentals (such as humans and hedgehogs) and monotremes [egg-laying mammals].”  (Thomas E. Williamson et al., The Origin and Early Evolution of Metatherian Mammals:  The Cretaceous Record, ZooKeys, Volume 465, 2014, page 8.)

As I’ve learned about metatherians in the Cretaceous, some questions about this skeleton cast and, by extension, all such casts, have bubbled to the surface.  More on that in a bit.

Paleontologist Thomas Williamson and his colleagues have written a comprehensive article on metatherians in the Cretaceous (see citation above).  They consider in detail the evolutionary development of the metatherians, review the fossil record of these animals, describe the ecological environment within which they lived, and hypothesize about the impact of the extinction event at the end of the Cretaceous Period on these organisms.  Their treatment of these subjects is surprisingly accessible to a general reader, though, certainly, my interest in one of the metatherian species helps.

Blogger Brian Switek (Laelaps) posted a good overview of the main findings of Williamson’s piece.  Short of reading the article itself, his post serves nicely.

Perhaps the key aspect of the article for me, and the one that started me wondering about the Didelphodon skeleton cast, is how often Williamson and his colleagues come back to that fundamental reality for mammalian fossils in the Cretaceous and earlier, and for the metatherians in particular:  their fossils are few and very fragmentary, nearly always just isolated teeth and pieces of jaws.

Here are but two of the many instances in the article when they allude to the nature of these fossils:

Most Mesozoic mammal fossils consist of fragmentary jaws and teeth, which largely explains the intense emphasis that paleontologists place on the evolution of the mammalian dentition.  (p.6)

The crania and postcrania of Cretaceous metatherians are poorly known.  Most taxa are represented only by teeth and jaw fragments.  (p. 24)

Coincidentally, in recent weeks, I’ve been engrossed in paleontologist Michael Novacek’s memoir titled Time Traveler:  In Search of Dinosaurs and Ancient Mammals from Montana to Mongolia (2002).  It’s quite a rip-roaring account of one paleontologist’s life (including serious injuries and illnesses) in the field, from New Mexico to Montana to Chile to Mongolia – with some additional stops.  All in all, a great read.

At one juncture in a description of his paleontological work in the Gobi desert, Novacek observes that the truly important finds by the paleontologists there might not have been dinosaur remains, but small mammal skulls.

Some of these skulls were no bigger than an almond, but they were extremely important. Up to that time very little was known about mammals of the Cretaceous that lived alongside dinosaurs, and most of the evidence hailed from the American West, from Wyoming and Montana, where these tiny creatures left their remains as enigmatic fragments of teeth and jaws – as we call them, “spare parts.” (p. 283)

Spare parts!  What a brilliant characterization, but what a sobering one as well.  There is precious little beyond “spare parts” for Cretaceous metatherians.  Williamson et al. caution that in all of the research literature, “[o]nly two specimens that include articulated and partial skeletons have been described:  the stem marsupialiform Asiatherium from the Campanian of Mongolia and the early-diverging metatherian Sinodelphys from the Early Cretaceous (Barremian) of China.”  (p. 24)

The implications of this reality of metatherian fossils?  Paleontologists have to rely almost exclusively on metatherian teeth to glean insight into the shape, size, and life of these creatures.  Williamson and colleagues stress, “Reconstructing the postures, locomotor abilities, and habitat preferences of most fossil metatherians is exceedingly difficult, because most extinct taxa are known only from isolated jaws and teeth.”  (p. 45)

But wait, there’s a very specific implication of this dearth of articulated fossils . . . what about that beautiful Didelphodon skeleton cast?  Fabricated solely on the basis of just teeth and fragments of jaws?

Well, it turns out, no.  Some exploration of the information presented in the label for the skeleton cast makes that clear.

(Note that it's the cast that has had a Natural History Museum identification number assigned to it.)

The collector, Mike Triebold, is a commercial fossil hunter and preparator.  He is founder of the Rocky Mountain Dinosaur Resource Center and president of Triebold Paleontology, Incorporated.  According to the description on its website, TPI is a full-service company for vertebrate fossils, from collecting to preparing to mounting fossil skeletons.  I take it that the Smithsonian’s cast is one made by TPI, and based on a specimen found by Triebold and held in the RMDRC’s collection.

This specimen is more than teeth and jaw fragments.  RMDRC’s description states that the fossil discovered by Triebold constitutes some 30 percent of the entire skeleton.  In this context, that’s a remarkably large portion.  Indeed, RMDRC asserts, “This is the only North American mammal skeleton ever found from the late Cretaceous period.”

But, to date, as far as I can determine, this D. vorax skeleton has not yet been the subject of a formal published description.  Williamson et al., as quoted above, observe that there are only two articulated, partial, metatherian skeletons described in the literature, neither of them a Didelphodon.

So, the skeleton standing in the case at the Natural History Museum’s exhibit is based on a specimen that is about a third complete.  What are the implications of that?  For me, it reinforces my inclination to approach this cast, and, by extension, all casts, with a questioning attitude.  For this specific skeleton, I’d really like to know how the full skeleton was “fleshed out.”  Did the preparators have access to enough isolated fossil bones from other disparate D. vorax individuals to assemble an accurate full skeleton?  A reading of Williamson et al. would suggest they perhaps did not, but I don’t know.  To what extent did extinct or living analogues serve as models for the casts of specific bones missing from the fossil record?  I assume that occurred.  When did informed and educated assumptions about aspects of the skeleton enter into the equation?

Further, when the label (as in this case) for a skeleton cast identifies who collected the original specimen (a nice piece of information), would it not make sense to state what portion of the displayed skeleton is actually based on that fossil find?

These aren’t questions intended to convey skepticism of the validity and value of casts.  I embrace their use.  Rather, I am in search of a fuller picture of how any skeleton cast reflects the reality of its fossil record, particularly when that record is composed primarily of spare parts.

Dinosaurs: Surprising Candor at Discovery

In which the blogger discovers that the Discovery Communications Corporation exhibits surprising candor about its dinosaurs, despite what one might expect given much of the TV programming on its myriad networks.

These days, a visitor in search of mounted dinosaur skeletons will come away disappointed by the Smithsonian’s National Museum of Natural History.  As I’ve noted previously, the Fossil Hall is closed for renovation and the interim display, The Last American Dinosaurs display, which will feature a few dinosaur skeletons, wont be unveiled until this November 25th.  For dinosaur lovers, the couple of dinosaur skulls one can find in public nooks and crannies of the museum really don’t count or satisfy.  So, what’s a person in the D.C. area to do?

Well, if you define “nearby” relatively broadly, there are a number of great sites nearby to satisfy that dinosaur itch.  One might start with the places identified by Joe Bruns in an article in the Washington Post.  (Joe Bruns, You Don’t Have to Roam For More Dinosaurs, Washington Post, April 19, 2014.)  His list includes the following:

• the Maryland Science Center in Baltimore (for a great review of this exhibit, I would recommend the one Ben wrote for his Dinosours! blog),
• the Delaware Museum of Natural History in Wilmington,
• the Academy of Natural Sciences of Drexel University in Philadelphia,
• the Carnegie Museum of Natural History in Pittsburgh, and
• the American Museum of Natural History in New York City (I recently reviewed it in my usual idiosyncratic way).  

I have a quibble with Bruns’ list because he clearly assumes that, in the quest for these beasts, all roads lead north from D.C., which is wrong.  For example, one can head south to the Virginia Museum of Natural History (in Martinsville, Virginia) which offers dinosaurs in its Hall of Ancient Life.

Also, more recently, a Spinosaurus skeleton mount went on display in the National Geographic’s Museum in D.C.  According to the review Ben posted on his blog, this is a worthwhile exhibit describing the historical context for the dinosaur and explaining quite frankly the nature of the skeleton on display (a cast of bones from several individuals).

If an isolated, fossil skeleton mount of a dinosaur does the trick, then there’s the lobby of the Discovery Communications’ world headquarters in Silver Spring, Maryland.

Perhaps it’s not surprising or illogical for Discovery Communications to have dinosaurs in the lobby.  After all, this global, pay-television-programming behemoth claims to be guided by “passionate curiosity.”  (2013 Annual Report.)  Of its extensive TV programming, Discovery avers:

Our content spans genres including science, exploration, survival, natural history, technology, docu-series, anthropology, heroes, paleontology, history, space, archeology, heath and wellness, engineering, adventure, lifestyles, crime and investigation, civilizations, current events and kids.

That does give me pause, though.  What a curiously constructed list of “genres.”  It’s a hopeless mélange of fields of science and elements of pop culture.  Frankly, that list isn’t surprising if one considers the programming that the Discovery Communication’s various networks spew forth.  A reasonable conclusion is that, for Discovery, “passionate curiosity” is joined (or perhaps displaced) by a passionate search for ratings and earnings.

Among the many, many programs broadcast by Discovery’s various networks are numerous so-called “reality TV” shows, including such gems as Naked and Afraid in which, for each episode, two stark naked strangers (a male and a female, of course) are dropped into some wild area with minimal equipment and followed as they try to survive for 21 days, or Amish Mafia which features the doings of a handful of Amish who purport to be the local enforcers in the Amish community of Lancaster County, Pennsylvania.

(In the interest of full disclosure, I’m not opposed to reality TV per se.  I’ve been known to watch a few reality TV shows, such as Top Chef and Storage Wars (neither of which is part of the Discovery family).)

Discovery Communications’ programs have often taken their lumps from the critics.  Though the premises may be laughable or cringe-worthy, it’s Discovery’s lack of candor about the reality of reality TV that troubles me the most.  For instance, the New York Times reviewer of the Amish Mafia when it debuted, observed, “An early credit warns of ‘select re-enactments,’ and since we’re never later told whether we’re watching staged scenes, it’s fairly safe to assume that everything is staged. (A closing credit clarifies that ‘re-creations are based on eyewitness accounts, testimonials and the legend of the Amish Mafia.’)”  (Mike Hale, The Dirty Work for the Clean, New York Times, December 11, 2012.)

And, hey, when Discovery’s annual TV feast known as Shark Week can be taken to task for lying to its audience by Wil Wheaton (yes, that Wil Wheaton of Wesley Crusher fame), among others, one has to believe ratings may not have just displaced passionate curiosity, but honesty as well.  Here’s Wheaton on the opening episode of Shark Week in 2013:

Discovery Channel started Shark Week with a completely fake, completely made-up, completely bullshit “documentary” and they lied to their audience about it.  They presented it as real.  (Wil Wheaton dot Net, August 5, 2013.)

Joining in, science writer George Johnson dismissed the “science” content on the Discovery Channel as not even “good fiction.”  (Not Just Sharks – The Junk That Passes For Science on the Discovery Channel, Fire in the Mind blog on Discover Magazine’s website, August 6, 2013.)

So, with that as context, it wasn't unreasonable to be curious about how Discovery would present the dinosaurs housed in the lobby of its world headquarters.  First things first:  the hours that it's open to the public aren't obviously displayed anywhere.  I gained admission during the work week, after having failed on a Saturday afternoon.

Once inside the lobby, I found it hard to draw myself away from the fascinating piece of kinetic artwork by George Rhoads which greeted me (it was operating when I entered).  But, yes, there are dinosaurs in the lobby:  a mounted Tyrannosaurus rex skeleton, a very small mounted Bambiraptor (the creature was small in life; indeed, the holotype is probably a juvenile), and a Triceratops skull.

I was surprised and impressed that, for the most part, the signs for each are richly detailed and informative.  In general, they describe with refreshing candor what is being shown to visitors, including background information on how these display specimens came to be.

For example, though its wording is convoluted and unfortunately conflates casts and molds, the display sign for the T. rex makes it clear that the visitor is not seeing fossil bones:

Discovery Rex is not an actual skeleton. . . . What you see here is a mold of the bones, captured in painstaking detail by a process called casting. . . . Institutions are using a variety of silicon rubber products to produce scientifically accurate molds that can capture such minute detail as the serration in a T. rex tooth.

The sign also notes that the actual fossil skeleton is nicknamed “Stan” after its discoverer and that it resides at the Black Hills Institute of Geological Research.

Hmmm, that means that this Stan has a twin that will grace the Last American Dinosaur exhibit which will open shortly at the Natural History Museum.  Perhaps it was just the lighting, but I found the Discovery cast of Stan to be more impressive than the Smithsonian’s cast of Stan, at least as it was displayed for years in the Fossil Hall.  Somehow Smithsonian Stan is no longer so special.

[Later edit:  Casts of Stan are actually widespread.  In a post titled "The Stan Gallery" on Dinosours!, Ben explores the phenomenon, illustrating it with pictures of a subset now on display in 14 different venues, mostly museums, but including the Discovery headquarters and a Best Western.]

The Triceratops skull is very nice and open to close inspection.  It was found on a private ranch in North Dakota in 1994, and, if I interpret the sign correctly, what is on display is some 85 percent fossil bone.  The cast material appears pretty obvious on the skull.

The Triceratops sign notes that Geolinea Paleontological Laboratories handled the prep of the remainder of the skeleton.

Well, the mention of Geolinea undoes a bit of the good vibe I had from this dinosaur display.  Geolinea, now known as Geoworld, was the source for the fossils that were auctioned off in August, 1999, through a collaboration between Discovery Communications and Amazon.  (Judith Graham, Scientists Harden Position on Selling Fossils, Chicago Tribune, October 24, 1999; Keay Davidson, Online Fossil Sales Worry Scientists, San Francisco Examiner, October 4, 1999.)  The whole thing greatly stirred up the paleontological world, prompting the Society of Vertebrate Paleontology to pass a resolution in October, 1999, expressing alarm about the auction:

We are deeply concerned by the on-line, auction sale of vertebrate fossils, as the nature of the process cannot assure that scientifically significant fossils are deposited into not-for-profit scientific and educational institutions.

 I don’t know how this specific story played out in the intervening 15 years with these players.  A brief search didn’t turn up anything.  But, getting into bed with Amazon to auction off fossils doesn’t seem out of character for Discovery Communications (however scary it seems to me).  And, even if the Geolinea reference hadn’t been enough to remind me of the nature of the corporation in question, what appears in a corner of the lobby, behind Stan, would have.  There they are:  real (I assume) motorcycles and cardboard cutouts of stars of the now defunct Discovery Channel’s reality TV show, American Chopper.

Apart from the dinosaurs, I was quite taken with the mammoth material that is also on display in the lobby – real teeth and hair, a model of a baby, and a quite beautiful, very real tusk with blue-green stains from the cobalt and copper in the soil which held it all these years.  Some 15,000 to 18,000 years old, it was found in Alaska in 1996.

There are, I think, at least two kinds of truth one might look for in fossil skeleton displays.  One, and perhaps the more important, is whether aspects of the complex reality of where, when, and how that ancient life existed are represented, based on current scientific understanding.  Mounted skeletons in isolation like those on display at Discovery Communications don’t demonstrate that truth, nor do they seek to.

Another truth comes from the disclosure of whether what’s on display is fossil bone, a cast, some combination of the two, and whether this display comes from a single specimen or is some amalgam of pieces from different individuals.  Discovery Communications' lobby display seems to me to handle that truth quite well.  It’s a matter of candor.

One final note (and a segue from the Discovery mammoth material), the Natural History Museum is apparently just learning the truth about the mammoth skeleton that had been on display in its now-closed Fossil Hall.  As the skeleton is being “deconstructed” by a team of experts, we are now coming to understand that this skeleton is a composite of skeletal pieces from perhaps as many as 70 individuals and not necessarily all from the same species of mammoth.  (A Mammoth, But Careful Restoration At Smithsonian, Associated Press, Washington Post, October 21, 2014.)  No, it’s apparently not what would be done today - one Smithsonian scientist is quoted as saying, “Mixing species is a strange thing to do in a modern exhibit.”  Well, if such a skeleton mount were to be on display today, one hopes for some candor.

A Different Way to See Fossil Skeleton Mounts

Memorandum
To:  Myself
Subject:  Fossil Skeleton Mounts

Next time you are in a natural history museum (one with its fossil halls not undergoing renovation, so, forget the Smithsonian’s National Museum of Natural History), approach a fossil skeleton mount (that sine qua non of natural history museums), and try your damnedest to get beyond that initial awe-inspiring view.  Move as close as you’re allowed and look for those telltale signs of how that skeleton is being held together, how it’s holding its pose.  Look for the armature, that construct of metal that keeps the bones in place.  Yes, some armatures are internal, but a glimpse of a bit of metal sneaking through joints, from inside one bone into another, might be had (unless the joints are filled in with plaster).  An external armature might be as obvious as that holding up the neck and torso of the Apatosaurus skeleton dominating the Peabody Museum of Natural History’s Great Hall,

or it might be mostly hidden on the backside of the bones.

Look carefully at the bones.  Try to identify which of the skeleton’s bones are real fossils and which are casts.  Museums seem to be doing a better job these days of ensuring that fossil bones and casts can be distinguished from each other.  On older mounts this may not be so easy given that fossils and casts were often painted the same color.

If fossil bones can be distinguished from casts, consider the fate of those real fossil bones in such a mount.


It’s not clear when I’ll be able to follow the guidance in this memo.  [Later edit:  I will be able to follow the memo a lot sooner than I thought.  In the original version of this post, I wrote that "there are no fossil skeleton mounts on display, at the moment, at the NMNH (my natural history museum home)."  That's wrong.  There's at least one on display in the Sant Ocean Hall, a Basilosaurus, which is an ancient whale.  See Addendum at end.]  “Hatcher,” the cast of a Triceratops, which had been the sole dinosaur standing publicly in the museum after the Fossil Halls shuttered their doors earlier this year, is now behind temporary walls on the third floor as a new Late Cretaceous display takes shape around it and “Stan,” the museum’s T. rex cast.  When it opens in late November, this display will be up for five years as the Fossil Halls undergo their total makeover.

It’s not a coincidence that my interest in the process and consequences of including real fossils in skeleton mounts has taken flight just when the NMNH Fossil Halls are off-limits.  Most folks would be interested in the construction of the new NMNH displays, but, in my contrarian (perhaps better read “perverse”) fashion, I have become focused on the flipside of that, that is, on the dismantling of the myriad mounts that graced the Fossil Halls for the past century.

Some wonderful pictures of aspects of this deconstruction can be found in various postings in the Smithsonian blog Digging the Fossil Record:  Paleobiology at the Smithsonian.  To date, primarily featured in these posts is the taking apart and moving of the casts of “Hatcher” and “Stan” (cast mounts really aren't my concern here).

Visitors to the NMNH can witness some of that fossil mount deconstruction if they visit the museum’s FossiLab on the second floor and look in through the windows and watch the volunteers at work.  A recent entry in the Digging the Fossil Record blog highlighted the reopening of the FossiLab (which had briefly been shielded from public view in its previous location down in the Fossil Halls) and noted that some volunteers in the lab will be engaged in taking mounts apart and creating storage containers for the disarticulated bones.  The blogger (sadly, anonymous) comments that:

Dismantling skeletons is challenging.   Some of the mounts were built a long time ago and, since mounting techniques have changed a lot over time, nearly every mount was constructed in a different way.  Add in the problem that some of the bones are extremely fragile, and it can take some puzzling to figure out how to tease the mounts apart safely.  Once the bones are free of the armature they are photographed, logged into our collections database, and placed in archival storage where they will be preserved for scientific study and, perhaps, remounting for a future exhibit.

What happens to fossil bones when they are included in such mounts, particularly those “built a long time ago”?  There is literature out there about that.  A particularly depressing account comes from Robert L. Evander, senior principal preparator at the American Museum of Natural History, in a 2009 piece titled Armature Damage to a Mounted Specimen (this full-text link is listed on the Society of Vertebrate Paleontology’s Preparator’s Resources site).

The fossil mount in question is the skeleton of a glyptodont, a large (some were car-sized), armored, armadillo-like mammal, that dates back to at least the Miocene (23 to 5 million years ago) and which went extinct about 10,000 years ago.  Evander basically reverse-engineered the mount because the American Museum of Natural History’s Adam Hermann, who prepared the mount from the fossil bones in 1916 – 1917, left no detailed account of how that particular mount was constructed.  This was the final fossil skeleton he mounted, so, it may reflect the best of Hermann’s work.  Writes Evander,

Adam Hermann’s free mounts are deceptive.  The bones appear to be gently mounted upon cleverly-hidden external armatures closely shaped to the bones.  The few visible drill holes seem to be attaching individual bones to this external armature.

How did he achieve this deception?  Well, he drilled some 100 holes lengthwise into articulated fossil bones in order to run wires through them as part of the internal armature.  Spaces in joints were filled with plaster.  The external armature was shaped on the basis of plaster casts of the bones and was then attached to the fossil bones by more drilling through the bones, and the insertion of many more nuts and bolts.  Here’s an illustration of parts of this method from a piece Hermann wrote explaining his fossil preparation and mounting techniques; the caption tells the story (Modern Laboratory Methods in Vertebrate Palæontology, Bulletin of the American Museum of Natural History, Volume XXVI, 1909, p. 318):

Evander discovered that, because the armatures are harder than the bones, the points at which the armatures are screwed or bolted to the fossil bones are places where cracks and breaks have developed.

Conclusion?  Disaster.  Writes Evander of this fossil skeleton and others mounted by Hermann a century ago,

In some measure, Hermann’s mounting has adversely affected scientific access to these specimens, which will never be freely available to study in the disarticulated state.  Individual postcranial elements cannot be extracted easily.  Realistically, these mounts are permanent.

It is ironic (from our perspective a century later) that in the same 1909 piece of his, Hermann cautioned,

I therefore say, that a beginner in a palæontological laboratory never ought to be trusted with a delicate and rare specimen.  In my experience, I have seen irremediable damage done on account of poor judgment.  (p. 331)

Because Hermann-like treatment of fossil bones in mounted skeletons continued well into the 20th century, Evander finishes with a word for us frequenters of natural history museums:

Thus the mounted specimens seen in the museums of the world may be more fragile than they appear.

Though the doors to the NMNH’s Fossil Halls are shut, I wondered whether photographs I’d taken previously of its fossil skeleton mounts might show something about the mounting process employed.  One entry in Digging the Fossil Record includes a couple of pictures of the work on dismantling the museum’s Irish Elk with its massive antlers.  This particular mount, which went on display in 1872, was the Smithsonian’s first mount utilizing real fossil bones.  (A post on the superb blog Dinosours! [sic] discusses this skeleton mount.)  That prompted me to look at pictures I’d taken of the Irish Elk for a previous post on my blog.  The picture below (looking head on) shows the animal’s left antler and the wiring that holds up.  A couple of seemingly benign metal supports appear to cradle the antler from its ventral side.

But, the following picture (taken from behind the animal) suggests that all is not so benign.  The “cradling” arms are apparently bolted through the antler to a metal plate on the backside of the antler.  Further, part of a metal armature can be seen coming from the skeleton up onto the antler.  This too is apparently bolted to the antler.  I have marked several of these bolt heads.

I found a bit more in my collection of photos.  A set of photos of the NMNH’s Brontotherium hatcheri (taken for a blog posting about this rhinoceros-like herbivore related to horses that lived some 40 million years ago) may also be revealing.  Unfortunately, I cannot be certain when this mount was created (the fossil bones were discovered by John Bell Hatcher in 1887) nor exactly which of the bones in this skeleton are real.  But, the Smithsonian’s Collections Search Center describes this specimen as including the following fossil bones:  “skull elements, lower jaw, Axial element, thoracic vertebra, Appendicular elements, pelvic girdle, phalange.”  Here’s a picture of the rump of the specimen.  I’ve marked two places that particularly drew my attention.

The lower arrow points to part of the external armature, where it is bolted onto the skeleton.

Do these go into fossil bone?  I don’t know.  I’d love to be able to see this skeleton again.

The upper arrow points to part of the pelvic girdle (which is listed as fossilized bone but perhaps not all of it is) where a bolt head is obvious.

I assume this bolt attaches to the external armature which runs behind the bone, and I believe that this bolt runs through fossil bone, not plaster.  Of interest is the crack that radiates from the bolt head.  Evander would probably not be surprised.

Despite all of this, I’m not prepared to let the other shoe drop, the one that signals opposition to inclusion of any actual fossils in free standing skeleton mounts.  That’s a major bone (pun intended) of contention in paleontological circles where there is concern, not just for the damage done in the mounting process, but the potential damage incurred by being in such a mount for the long term, subject to changes in temperature and humidity, vibrations, and other harmful stresses.  Though mounting techniques have changed for the better, I may still be heading in the direction of advocating for nothing real in free-standing mounts (I would not be alone in holding that position).

For the time being, memo writer, I will consider such mounts from that different perspective and with a great deal of concern.

ADDENDUM

Ben, author of the blog Dinosours!, commented on this posting (see below) and asked my reaction to more "gentle" mounting techniques.  In my response, I referred to Digging the Fossil Record and a post there by Matt Carrano, Smithsonian Curator of Dinosauria, in which he stated that mounts in which fossil bones were drilled into were a thing of the past.  He included a photo of some of the sternum bones of an ancient whale currently on display at the NMNH; these bones were cradled in metal supports.  When I went back to his post, I was dismayed on two counts:  first, I should have quoted Carrano in my original post (I do in my response to Ben), and, second, I had completely overlooked the fossil skeleton mount of the ancient whale in the Sant Ocean Hall (which allowed me to make the erroneous assertion that, with the closing of the Fossil Halls, there weren't any still on display - indeed, there may still be others, my search continues).  I've had a chance to take a look at that whale skeleton (which includes real bones) and, though I tried, I found it difficult to really observe how all of it was mounted (sorry, memo writer) because the whole thing floats high overhead, suspended from the ceiling (and accompanied by two cast mounts).  Clearly, the sternum bones are being supported without drilling, as apparently are the vertebrae.  Also, real bone and cast are easily distinguishable, a good practice.  But, I cannot be so sure that some bolts aren't still penetrating real bone.  Unfortunately, I cannot get close enough to be sure.  Here is a picture of a few of the ribs and a flipper (real bone is darker and rougher).  Perhaps I'm just inclined to see it, but it does look to me as though some real bone may have been drilled into.