Fossils and Glitter

I found a thought-provoking juxtaposition of fossils and that ubiquitous element of children's art - glitter - in a recent edition of the daily newsletter from Nature (Nature Briefing, October 14, 2025).  This issue highlighted the magnificent dinosaur trackways recently discovered in the United Kingdom.  Toward the end of the newsletter, the "Quote of the day" (a frequent feature) had the following statement:

A glitter container is never really empty.

A pretty sure way to grab this reader's attention.  The source of that quotation was an article about Edwin Jones, a forensic scientist well versed in the crime-solving attributes of glitter.  As we all know, glitter, once let loose, contaminates nearly everything and everybody.  Turns out, that can be quite helpful in linking individuals and objects to a crime scene.

Putting those two stories together reminded me of a passing comment I'd made long ago relating criminal forensic science to paleontology, specifically the subfield called ichnology, the study of trace fossils.  (See the post titled Ichnofossils and Old Home Movies, November 8, 2009.)  

It's useful to consider what we mean by forensic as an adjective and forensics as a noun.  The Latin root of forensic means of, or related to, the Roman Forum or with the courts of law.  (Oxford English Dictionary.  Sorry, it hides behind a paywall.)  The adjective was first used in English in 1647 and, in keeping with the Latin root, was applied to something associated with court proceedings or appropriate for use in court.  In the 1800s, the noun forensics was applied to the kind of rhetoric intended to argue or assert a point in a law court or in debate (particularly collegiate debate).  In the late 1800s, forensic science began to take on the meaning that, as a rabid consumer of TV shows featuring crime scene investigations, would expect of it (first use in print in 1893):

The provision of scientific evidence and testimony in legal proceedings; (in later use) spec. the application of scientific techniques and knowledge to the investigation of crime.  (OED.)

The article cited by Nature for the "Quote of the day" was written Jacqueline Detwiler-George.  It's a fascinating introduction to Jones and the role of glitter in forensic science.  (Inside the Glitter Lab, Popular Mechanics, September 26, 2025.  This article also resides behind a paywall.)   The article's hook is a fairly graphic account of the rapes committed by the Simi Valley rapist and the role Jones and glitter played in securing the death penalty for the perpetrator.  The investigator determined that glitter in the hair of a murdered victim was rather unique and he was able to trace it to the perpetrator's truck.

Detwiler-George identifies an important distinction in forensics between trace analysis and DNA analysis (forensic biology).  Of trace analysis, she writes:

In reality, it can include analyzing an absurd variety of materials.  It could be flame accelerant, explosives, cosmetics, carpet fibers, tree bark, hairs, shoe prints, clothing dirt glass fragments, tape, glue and, yes, glitter.

The latter, forensic biology, has come to dominate the field, relegating the former to the sidelines, partly because trace analysis requires expensive tools while DNA analysis has, I would surmise, such probative value.

It is trace analysis that really gave forensic science its original impetus.  Detwiler-George quotes the late Robert Blackledge, a forensic chemist with the Naval Criminal Intelligence Service (NCIS):  "Trace evidence analysis is the oldest kind of scientific crime-solving technique in existence."  One of the foundational beliefs for criminal forensics is the principle first enunciated by Frenchman Edmond Locard (1877-1966):  "Every contact leaves a trace."  I may be easily impressed, but I find that the Locard Principle profound and applicable well beyond crime scenes.

Having read about the glitter expert Jones before reading stories about the newly found dinosaur trackway, I found myself focusing on the steps being undertaken by the paleontologists to reconstruct the scene as it was in deep time.  Not a crime scene, I will admit, but, still, the impulse to reconstruct the events of so long ago, is, I think, akin to that undergirding criminal forensics.

I don't believe I am taking it too far to suggest that a variant of Locard's principle is at play in ichnology which works with fossilized evidence of ancient activity.  The fossil trackways described in the Nature newsletter are really spectacular examples of ichnofossils, which, in this case, date from some 166 million years ago.  (The link in the Nature article was to Rebecca Morelle, et al., How a Huge Dinosaur Trackway Was Uncovered in the UK, BBC News, October 14, 2025. See, also, Will Triggs, New Dinosaur Highway Dig Reveals Record-Breaking Footprints, EarthSky, October 15, 2025, and Oxford Researchers Return to the Jurassic Highway, University of Oxford, News, October 14, 2025.)

Clearly, the present day scene of the trackways (a quarry in Oxfordshire, United Kingdom) has been changed beyond recognition over the millennia, but the Locard principle - that contact leaves traces - still applies.  Not only were the tracks squished into the mud of the lagoon traversed by dinosaurs in the Late Cretaceous and then fossilized and preserved, but other traces of life and elements in the environment from deep time have also been retained at the scene.  Instructed by the glitter forensics article, I was particularly attentive to how the paleontologists uncovering, preserving, and analyzing the trackways took a broad view of the scene.  In this instance, they were not solving a crime, rather, they were reconstructing the events at a scene, and doing so without any eyewitnesses.  As a result, they have, as would good forensic scientists, to determine what messages the objects and traces found at the site could tell them about the events that had occurred here.

The trackways were found at the Dewars Farm Quarry and they are quite amazing, the longest stretching for 220 meters or 721 feet - the length of nearly 2 1/2 football fields.  They are the tracks of multiple individual Cetiosaurus dinosaurs, a massive herbivore, joined by a single trackway of a Megalosaurus, a large bipedal carnivore.  Certainly, paleontologists have experience with dinosaur tracks and can identify the likely animals that made them.  Still, unless the fossilized remains of the animal are found in conjunction with the fossilized traces, there's always some room for misidentification.

The paleontologists are attempting to reconstruct what the scene 166 million years ago was really like and, broadly, what happened here.  Duncan Murdock, one of the leaders of the project working on the trackways, has noted:

Unlike fossil bones, finds like these tell us about the behavior of extinct animals.  The size, shape and position of the footprints can tell us how these dinosaurs moved, their size and spreed.  And where trackways cross, we get a glimpse of the potential interactions between different species . . . .  (Triggs, EarthSky, emphasis added.)

The scientists determined the direction in which the animals were heading by careful study of the footprints.  At the front of each print is a protrusion which was left as the animal shifted its weight to the front of its foot when taking a step, squishing out some of the mud in which it was traveling.

Based on the number of footprints, Murdock observed that were "tens of individuals" crossing the muddy lagoon and, if, as is possible, they were present at the same time, what was captured by the trackways was herding behavior.  (Triggs, EarthSky.)

The single Megalosaurus track intersects the track of one of the Cetiosaurus dinosaurs leading to some speculation about the context and meaning of this interspecies encounter.

Reconstructing the scene has required looking for, and analyzing, evidence beyond the prints, and that evidence is emerging.  The paleontologists have found fossils from marine invertebrates, plants, and part of a crocodile jaw, and work is ongoing to analyze the content of the sediments under and in the prints.  (University of Oxford News.)  Murdock captures well the objective:

Along with other fossils like burrows, shells and plants we can bring to life the muddy lagoon environment that dinosaurs walked through. (Triggs, EarthSky.)

In the end, I wonder if ichnology, in general, might be termed a form of forensic paleontology?  At a minimum, it seems to be a field in which some of the methods of forensic science are applied to fossils in an effort to describe and, perhaps, explain the behavior behind fossilized traces of activity.  In other words, to reconstruct a scene and the events that took place there.

For a fascinating look at how some paleontologists have applied the analysis methods used in forensic entomology, I would recommend the article by paleontologist Kenneth S. Bader and colleagues describing their analysis of a cache of dinosaur bones from the Jurassic found in Montana.  (Bader, et al., Application of Forensic Science Techniques to Trace Fossils on Dinosaur Bones from a Quarry in the Upper Jurassic Morrison Formation, Northeastern Wyoming, Palaios, Volume 24, 2009, p. 140.)  We're all familiar with the forensic scientist on TV extracting a beetle larva from a corpse and announcing how long the body had been exposed to the elements.  That's forensic entomology at work, bringing to bear on a crime scene the understanding of when and how insects and other arthropods will work on the flesh and bones of dead animals, what evidence they leave of their presence, and what that evidence says about the environment in which the body lay.

Based on the evidence gathered by using these forensic techniques, the authors describe in wonderful detail a scene from millions of years ago:

These events were initiated during the dry season, and were likely part of a prolonged drought, based on our interpretation of the levels of articulation for each of the sauropod skeletons, bone modification features found on those skeletons, and previous interpretations of the Late Jurassic paleoclimate recorded by the Morrison Formation [citations omitted].  The evidence suggests that sauropods were drawn to this area for its water availability over an extended period of time.  Fossils of turtles, fish, crocodiles, snails, and bivalves support the notion of a relatively permanent body of water.  A prolonged drought is thought to have occurred based on the different conditions of the sauropod skeletons, which suggest that the area was not resubmerged with differential burial of the skeletons.  Only after all the sauropod skeletons accumulated, the soft tissue decomposed, and the bones were bored, did the drought end and the accumulation of skeletons was buried.  A short duration of pedogenesis [the formation of soil] took place before additional sediments covered the area of the skeletons likely through a period of regular succession of wet-dry seasonal climates.  (p. 156)

All that's missing is an explanation of the glitter found at the scene.

Concrete Sidewalk Impressions: What's A Fossil?

In which I, once again, may be accused of obsessing about issues involving trees while missing the spirit of the forest.

For a reason that now escapes me, I ended up on the Nova Scotia Museum’s website blog, specifically on the post for March 25, 2020, the one titled Urban Geology.  The post deals with the impressions captured by chance in concrete sidewalks, specifically, those imprints left by plants (mostly leaves) and animals (often birds or humans) in the concrete when it was still wet.  The author (Tim Fedak, I think) labels these as urban fossils with no explanation as to why they are fossils.  The post includes photographs of sidewalks showing interesting random traces of the passing natural scene.  Since I am easily sidetracked and entertained, I spent the next few of my local outings in search of these delicate and evocative sidewalk impressions.  Here are a few of my finds discovered while I, once again, spent time staring at the ground where the paleontologist’s gaze is so often fixed.  I provide no identifications for the images of leaves, given no likely suspects standing in the immediate vicinity or, at least, not ones I could identify.

It was an enjoyable time fritter.  By the way, the last picture shows various impressions of the treads of running shoes.

The Nova Scotia Museum’s blog post steered me to retired middle school science teacher Kenneth Fuller and his Science Can Be Fun! website.  Here Fuller lays out various science activities for students and their teachers, including a paleontology unit that focuses on these sidewalk impressions, which he calls Sidewalk Fossils.  These are potentially engaging activities that, as he structures them, might instill some worthy habits in student participants, ranging from close observation of phenomena to recording what is observed to fashioning hypotheses about the origins of these phenomena.

Significantly, though, he asserts that concrete impressions in sidewalks are actually fossils.  He writes:

By definition a fossil is any remains or trace of a living thing preserved in rock.

He then states that the concrete impressions of leaves and animal tracks meet that definition:

The concrete of which a sidewalk is made is rock. . . .  Since the concrete is rock, remains or traces of living things preserved in the concrete are fossils.  Since such fossils are most often seen in the concrete of sidewalks, we refer to them as "sidewalk fossils" wherever we find them.

Posit an erroneous definition and all sorts of mischief can ensue.  The central error of his definition is made clear below.  Further, there is an unsettling note of authority in this.  Who’s the “we” calling them sidewalk fossils?  “Scientists” is the implication, I think.  He later distinguishes these fossils from natural fossils with no attempt to explain the differences.  I also don’t know what to make of his suggestion on another page of his website that, when teachers fashion a definition of fossil with their students, that they have “some real fossils to show [which] would help at this time.”  Real?  As opposed to what?  Sidewalk fossils?  More than a bit confused.

Later I read an entertaining piece by science writer Jessica Leigh Hester on the Atlas Obscura website titled Fresh Concrete Turns Paw Prints and Bird Tracks Into Urban Fossils (September 18, 2020).  At times she refers to them as fossils, modern trace fossils, and concrete impressions, and notes they have “prehistoric counterparts.”  The article profiles Carl Mehling, a specialist in paleontology at the American Museum of Natural History, who has had a longstanding interest in these sidewalk impressions, amassing a collection of several hundred photographs of them, particularly, of animal tracks.  The photographs included in Hester’s piece are quite beautiful.  Of the origins of his interest, Mehling says that, as a second-grader, he came upon a leaf impression in a sidewalk.  “I regarded it as a fossil, and was scheming about getting a hammer and busting it out.”  

Hester posits that animal trackways preserved in concrete pose questions of interpretation like those that bedevil paleontologists working with trace fossils (ichnofossils) of dinosaurs and other ancient animals.  Among the questions raised by both kinds of trackways are:  What animal made these marks?  What was it doing?  How many were involved?  Were all of these marks made at the same time?  She writes, “It’s a slippery task to try and draw too many conclusions from the trackways – which actually makes them similar to prehistoric prints, Mehling says.” 

Though pursuit of concrete sidewalk impressions makes for an enjoyable hunt, the literature I've cited clearly troubles me.  Do these authors believe these are actually fossils or am I missing the gentle joke here?  Is the label fossil in these texts applied with a touch of whimsy or poetry and a gentle wink to let the reader know quotation marks surrounding the word are implied?  I would have let slide their use of fossil in this context had any one of them explained that the trace fossils studied by paleontologists are somewhat similar to, but critically different from, say, a bird’s trackway captured in wet concrete.  They don't.

Hester's article is the one that puzzles me the most.  With a paleontology professional at hand, she never once quotes Mehling weighing in on whether the label fossil is appropriate for the concrete trackways whose pictures he has amassed.  I’m sure he could have opined knowledgeably on the subject.

A discussion of what the common or scientific definitions are of fossil seems appropriate at this juncture.  Regarding common usage, my Compact Oxford English Dictionary (revised 2003) provides, as its first definition: 

the remains or impression of a prehistoric plant or animal embedded in rock and preserved in petrified form.

Certainly of no help to the Nova Scotia Museum, Fuller (despite the emphasis on rock), or Hester.  The use of the adjective “prehistoric” categorically disqualifies concrete impressions.  (The second definition is “an antiquated person or thing” which also doesn’t come to their aid.)

Turning to how the word is defined in the science devoted to the study of fossils, I will cite paleontologist Richard Fortey whose definition is more succinct and broader than the OED's:

Fossils are the remains of prehistoric animals or plants.

He immediately adds: 

Usually they are some hard part of an extinct organism, resistant to decay, that has been preserved enclosed in sediment – past life that has been buried in the rocks and entombed inside them.  Fossils could equally be the record record of activity of animals:  fossil footprints, perhaps, or the tubes and trails of soft-bodied worms that otherwise leave no trace.  (Fossils:  The History of Life, 4th edition, 2009, p. 8.)

Fortey’s definition starts with that succinct statement and then acknowledges the complexity of what is embraced in that terse phrasing.  Of most importance for my purposes is that telling adjective “prehistoric.”  Again, this precludes these sidewalk markings and trackways as being fossils.

Anyone who has had the briefest exposure to paleontological literature will realize that the challenge in defining what is a fossil lies in the many ways in which science explains that animals and plants (and traces of their activity) become fossils, that is, are fossilized.  Fortey covers all of the outlier processes with the adverb usually.  Indeed, several of those ways do not involve being "preserved in rock."  Sorry, Mr. Fuller.

Although I could rustle up other contemporary paleontologists’ definitions of fossil and see if concrete impressions might fit into one of those definitions, it would mostly be a fool’s errand.

Mehling himself makes that abundantly clear in an essay he wrote for Fossil News:  The Journal of Avocational Paleontology titled Collecting My Thoughts:  A Paleontologist Ruminates on What Makes a Fossil a Fossil (Volume 20, Number 1, Spring 2017).  This is a fascinating, albeit meandering and very long, exploration of the various definitions of fossil that have been employed over time.  In the course of this essay, Mehling describes a host of different ways in which animals and plants generate fossils, and suggests that any satisfactory definition should embrace as many of these fossilizing processes as possible.  He acknowledges that a fixed, rigid, “bullet-proof” definition is likely to be counterproductive and certainly not universally embraced.  Besides, our understanding of what is a fossil has evolved over the past several centuries as our knowledge has grown.  As a result, definitions have changed.

Mehling takes the reader through many definitions and the multitude of things that have at one time or another been called fossils (of note, sidewalk impressions are not among them).  He highlights the utility and, more importantly, the deficiencies of these definitions, and finally comes to rest (well, mostly) on a definition satisfying many of his concerns:

For now, here’s a useful definition:  “fossils are evidence of life that is at least 10,000 years old.”  That conforms reasonably well to a hazy intuition, leaving a few loose ends and poetic traps.  While increased qualifications may fortify definitions, they may also merely dilute the intent of the word into oblivion.  (p. 38)

He notes that a definition resting on an age distinction (such as “prehistoric” or “at least 10,000 years old”) “incorporates more of what are most commonly considered fossils and excludes those that make most paleontologists grimace and shake their heads.”  (p. 34)

Certainly, Mehling would dismiss the notion that sidewalk impressions are real fossils.  They fail the age test.  Still, he would understand the impulse to attach the word fossil to them, an impulse reflected in how often the word has been co-opted in the past.

In closing, I must cite the clearest definition Mehling considers, one nestled in the last footnote of the essay:

My sister Ellen offers the following definition:  “Old bones and shit like they have in the museum.  You know, dinosaur bones!  You know what I mean.”  I guess I should’ve checked with her first and saved myself all of this trouble.  (p. 38)

Name Game Revisited

I am fascinated by the process through which fossils, including tracks and other traces, are named and, often, renamed. I wrote on this previously in a couple of posts (What's in a Name? Part Un, and What's in a Name? Part Deux), but, as a paleontology newbie, I keep encountering other aspects of the process that intrigue and challenge me. Forgive me in advance if I’m wrong about something below (a gentle comment to that effect is welcome).

Duplicate Names Forbidden

Raymond C. Moore and his colleagues in their classic volume entitled Invertebrate Fossils (1952) described some of the basic rules that apply to the naming of fossils. Among those rules is the following:

“An important requisite of the scientific names of animals, whether of genera or of species, is that none shall duplicate another. Obviously, confusion and error are unavoidable if identical names may refer to different kinds of animals. . . . Homonyms (identical names applied to different things) are not allowed, and if, as has happened frequently, such names for genera or species appear in print, the later-published name is invalid.”

Duplicate names are forbidden – supremely logical.

A series of recent posts in a great blog – Dinochick Blogs – illustrates this rule at work. In this instance, at issue is the name to be applied to the dinosaur that for over 100 years was known as Diceratops. Seems that an inhabitant of the insect world already had legitimate claim to that name – the name was “preoccupied” (wonderful use of the word). So, apply the rule and come up with a new name.

Two researchers, independent of each other, each recently applied a new name to the Diceratops: (1) Diceratus – this name, derived from Greek, means “two-horned” or (2) Nedoceratops – the apparent derivation of the name is from “nedo,” a Russian prefix meaning “insufficient” or “incomplete” or “not quite” (well, that’s what my reading on the Web turned up for “nedo”), and from “ceratops,” from Greek for “horned face.” Nedoceratops was proposed in a publication that came out before Diceratus. Because prior publication prevails, Nedoceratops it is.

Logical rule, but, in this case, not a pleasing result for many. There are those who find Nedoceratops an insulting name for the dinosaur. Though one may acknowledge that, over all of these years, this dinosaur has been identified on the basis of a single specimen (not unprecedented), the name earns low marks in the politic or tact category. It’s almost as though the prevailing researcher (reportedly an entomologist) deliberately snubbed the dinosaur itself. A variant of paleontological one-upsmanship (see earlier post) at work? “I picked an irritating name because I can.” I don’t know, but the thought occurred to me.

Ichnotaxon, Ichnogenus

There’s another bit of impressive logic in the naming process. After a recent visit to a collection of dinosaur tracks outside of Hartford, Connecticut (Dinosaur State Park in Rocky Hill), I registered the facts, without really thinking about them, that the tracks had a genus name, Eubrontes, but no bones had been found to identify the animal that might have made them.



The speculation is that the tracks recorded passages of a kind of dinosaur similar to the carnivorous Dilophosaurus, whose fossilized remains have been found in Arizona.

Later, in a moment of mental clarity (rare for me, though I don’t think this quite qualifies as an epiphany), I saw the compelling logic of naming tracks or other “trace fossils” (see below) separately from the animal making them. I know this must fall into the “so what” category for those who have lived paleontology. What follows is this neophyte’s take on it.

A track or group of similar tracks may well be the sum of what we have; and, there is no certainty about what made those tracks. So, the tracks, independent of their creator, may be named. After all, we want to be able to talk about the tracks and, at a minimum, a name certainly simplifies things. Such a name is being applied to an “ichnotaxon,” a classification unit “based on the fossilized work of an organism, including fossilized trails, tracks or burrows (trace fossils) made by an animal.” (International Code of Zoological Nomenclature, see Glossary) In the case of the tracks at Dinosaur State Park, Eubrontes is the “ichnogenus” for these tracks, a name that lives independently of the still unknown creatures that made them.

It doesn’t take much to impress me, I guess.