Know thy namesake: the story of Gordon W. Weir and fossil fishes

The fossil fish Hemicalypterus weiri was named after Gordon Weir. But who is Gordon Weir?

This Saturday, November 11, the U.S. celebrates Veterans Day, a holiday in which we honor and remember veterans who have served and protected our country (as opposed to Memorial Day, which honors those who specifically died in combat). I have been kicking the idea for this post around in my head for a year now, and the timing seems appropriate to coincide with this year’s Veterans Day.

But, what exactly does paleontology have to do with Veterans Day?

Hemicalypterus weiri reconstruction.

Let’s digress for a bit of context. Last year I published a paper in PLOS ONE redescribing an unusual deep-bodied from the Triassic Chinle Formation. The fish, Hemicalypterus weiri is unusual for several reasons, most obvious being its partially scaled body (the anterior half being covered by thick, enameled scales; the posterior half being scaleless, which likely aided in flexibility). Hemicalypterus also possessed unusual teeth that resemble small forks, which were most likely used for a herbivorous feeding behavior, using the multicuspid teeth to scrape algae off of a rocky substrate, similar to modern algae-scraping cichlids. I published a paper in the journal The Science of Nature detailing the multicuspid teeth of Hemicalypterus, and also wrote about it on my blog.

Schaeffer tablecloth copy
Bobb Schaeffer, curator of Fossil Fishes at the AMNH, pictured here with the famous “Woodward Tablecloth” (a story for another day)

Hemicalypterus weiri was originally described by Bobb Schaeffer, the former curator of fossil fishes at the American Museum of Natural History in New York City. His work on the Triassic fishes of the American southwest has been a guiding force in my own career. Schaeffer described several species of fishes from the Chinle, but his description of Hemicalypterus was based on few, incomplete specimens, all of which were lacking articulated jaws and teeth. Schaeffer did not recognize or describe the multicuspid teeth, and it was only as I was preparing newly collected specimens of Hemicalypterus that I found complete jaws on several specimens, displaying the unique tooth morphology that is found in almost exclusively herbivorous fishes in both marine and freshwater habitats.

But Hemicalytperus itself isn’t the point of this post. The point is its specific epithet, Hemicalypterus weiri. As it says in the footnotes of Schaeffer (1967): “For Gordon W. Weir.”

A fresh-faced young graduate student perusing Gordon Weir’s geological notes at the U.S.G.S. Field Records collection library.

I had come across Gordon Weir’s name before, several years ago when I was perusing the archives at the U.S. Geological Survey Field Records collection in Denver, Colorado. Looking for more information regarding early fossil collections in the Chinle Formation in Utah, I found all of Gordon Weir’s field notes, government reports, stratigraphic columns, and notes on fossils he had discovered in the region, notably, articulated fossil fishes.

The handwritten cover on Weir’s report on Fossils from southeastern Utah, amongst reports on uranium deposits. From the USGS Field Collection Records archive.

Weir, along with Y. W. Isachsen (who at the time worked for the Atomic Energy Commission), had discovered fossil fishes while they were surveying southeastern Utah for uranium. As Schaeffer (1967) writes, “It is an interesting comment on the Atomic Age that the search for uranium minerals led to the discovery of abundant and diversified fishes.”

Weir and colleagues reported their findings, as well as some specimens, to the National Museum of Natural History in Washington, D.C.  in 1953. David H. Dunkle, who was curator of fossil fishes at the time, collected additional specimens in 1954, and later brought on Bobb Schaeffer from the AMNH to collect in the region and, ultimately, to describe the fishes recovered from the Triassic deposits.

For Weir’s significant contribution with regard to Triassic stratigraphy, fossil localities, and geology of southeastern Utah, Schaeffer honored Weir with a namesake: Hemicalypterus weiri.

Holotype of Hemicalypterus weiri.

As I examined new and old specimens of Hemicalypterus weiri for my research, I became  familiar with every aspect of this unassuming little fossil fish: its anatomy, morphology, abundance in the fossil record, localities, etc. Everything but its name. And it felt odd working so intimately on an organism that I did not name; one that already had a name, a name honoring a man I did not know, but to whom I owe a lot.

So when I googled “Gordon W. Weir,” I didn’t expect much. I anticipated some geological papers or reports, and not much else. What I didn’t expect was this:

Lt. Gordon W. Weir, WWII Pilot. Circa 1944

As it turns out, Gordon Weir was a lot more than a geologist for the U.S. Geological Survey. Gordon Weir was a decorated World War II veteran, a pilot in the Army Air Corps in the 861st Squadron, 493rd Bomb Group, and 8th Air Force. He served 30 flight missions in Europe in 1944 and 1945.

Weir died in 2011, and according to his obituary, Weir did not discuss his time in the Air Force for decades. His son later found three silver navigator’s medals in the bottom of a drawer and was unaware of much of his father’s war history.

Gordon Weir, circa 1943, on base in Nebraska.

Thankfully, Weir later became active in the 8th Air Force Historical Society, and has also left a legacy of his time in the War via an online memoir, which I invite everyone to check out, because his time in the Air Force during WWII is absolutely fascinating. He flew in over 30 missions in Europe in 1944 and 1945. When the war ended in 1945, he was training to serve in the Pacific Theatre. In one of his missions in Europe, his plane was one of only two of the twelve planes that returned to England.

Gordon Weir, circa 1945.

Weir’s memoir documents as much as he was able to recall 50 years after the events, but is laced with photos, documents, anecdotes, humor, and honest insight. He talks about everything from navigating a war-wrecked London, boating on the Cam in Cambridge, and flying in a B-17 bomber into German skies. He talks about the deaths of his friends, and the reality of the war. It’s a candid and fascinating read, and I am glad that it persists on the internet even after his recent passing, just shy what would have been his 89th birthday.


After WWII ended in 1945, Weir enrolled in UCLA to study geology, after which came his long career in the U.S.G.S. in which he, as he put it, “[tried] to comprehend the history of the Earth.”

In addition to his work in Utah, Weir also conducted geological research in Kentucky, Arizona, and Indonesia.

His son described him as “intelligent, caring, and interesting.” And I would agree. I am glad that I got to know him a little vicariously through his online memoir. He was truly a fascinating person, and I wish I had met him in person. But it’s truly an honor to be able to work on his namesake, Hemicalypterus weiri.

Read Gordon Weir’s WWII Online Memoir

Gordon Weir’s obituary


Gibson, S.Z. 2016. Redescription and Phylogenetic Placement of †Hemicalypterus weiri Schaeffer, 1967 (Actinopterygii, Neopterygii) from the Triassic Chinle Formation, Southwestern United States: New Insights into Morphology, Ecological Niche, and Phylogeny. PLoS ONE 11(9): e0163657. doi:10.1371/journal.pone.0163657

Gibson, S.Z. 2015. Evidence of a specialized feeding niche in a Late Triassic ray-finned fish: evolution of multidenticulate teeth and benthic scraping in †Hemicalypterus. The Science of Nature — Naturwissenschaften 102:10.

Schaeffer, B. 1967. Late Triassic fishes from the western United States. Bulletin of the American Museum of Natural History 135: 289–342.


The “Slasher” Ray: An extinct fish with a saw-like nose — PLOS Paleontology Community

Are the “teeth” on a sawfish snout really teeth? A fossil might shed light on the question.

This post was originally written by me and published on the PLOS Paleontology Community Blog on October 30, 2015. The original post can be accessed here.

Happy Halloween everyone! Still looking for a Halloween costume? Instead of dressing as a serial killer with a chainsaw, might I suggest dressing as a sawfish? Maybe not as scary as Leatherface, but just as deadly…if you are a fish.

Click on me! Watch out, "Jaws".... there's a new killer in town
Click on me! Watch out, “Jaws”…. there’s a new killer in town
So, about those teeth along the snout of a sawfish, are they really “teeth”? I have taken the origin of teeth for granted, and it’s a lot more complicated than I thought. A talk I saw in the Fishes Session at the recent Society of Vertebrate Paleontology (SVP) meeting in Dallas, Texas showed me just that, and the talk wasn’t about teeth…exactly. Or was it? That’s what Dr. Charlie Underwood from Birkbeck University, London, is trying to find out, along with colleagues Dr. Zerina Johanson from the Natural History Museum, London and many others (Monique Welton, Brian Metscher, Liam Rasch, Gareth Fraser, Moya Meredith Smith, Alex Riley, Jürgen Kriwet, and Cathrin Pfaff). Underwood’s talk presented an unusual fish from the Late Cretaceous (72–66 million years ago) of Morocco. Called Schizorhiza, it is a relative of extant rays, and had a 1.5-meter-long nose with large, pronounced teeth on the lateral edges, similar to modern-day sawfishes and sawsharks.

Reconstruction of Schizorhiza stromeri, image courtesy of Charlie Underwood.
Reconstruction of Schizorhiza stromeri, image courtesy of Charlie Underwood.
A sawfish (Anoxypristis cuspidata) rostrum from Welten et al. 2015 [2], showing the large, consistently spaced and sized saw-teeth, and their insertion into the rostrum.
A sawfish (Anoxypristis cuspidata) rostrum from Welten et al. 2015 [2], showing the large, consistently spaced and sized saw-teeth, and their insertion into the rostrum.
Okay, before I go any farther (because I had to get this right myself), Sawfish/Sawshark 101: what’s the difference? Sawfish are a family (Pristidae) of rays (Batoidea), characterized by a long snout with pronounced “saw-teeth” on each side of the snout, resembling a saw, hence the name. This description is also true for sawsharks of the family Pristiophoridae, which are true sharks (Selachii). Distinguishing these two groups comes down to more specific details: sawsharks have barbels on their saw and their “saw-teeth” alternate in size between small and large, whereas sawfish have pretty consistent large “saw-teeth” and lack barbels.
Sawfish have their gills on their ventral surface (like rays), whereas sawsharks have gills on the side of their body (like sharks). There are other details, but for brevity’s sake these are some simple ways to tell them apart. They are both cartilaginous fishes but are not closely related to each other, and each independently evolved these really cool (in my opinion), saw-like snouts for the purpose of prey-capture and feeding.
Two species of sawsharks (Pristiophorus nudipinnis a-c and Pristiophorus cirratus d-g) from Welten et al. 2015 [2], showing the barbels and saw-tooth size variation and placement along the snout laterally and ventrall, and along the skull. Two species of sawsharks (Pristiophorus nudipinnis a-c and Pristiophorus cirratus d-g) from Welten et al. 2015 [2], showing the barbels and saw-tooth size variation and placement along the snout laterally and ventrally, and along the skull.
Two species of sawsharks (Pristiophorus nudipinnis a-c and Pristiophorus cirratus d-g) from Welten et al. 2015 [2], showing the barbels and saw-tooth size variation and placement along the snout laterally and ventrally, and along the skull.

Now that you have those two groups down, let’s add a third, the Sclerorhynchoidea. These are Mesozoic forms that include Schizorhiza, and are closely related to rays. As I mentioned before, sclerorhynchids like Schizorhiza also have elongated snouts with “saw-teeth.” They are a wholly extinct group, present in the Cretaceous and Paleogene in epicontinental seas.

In fact, the rostrum saw evolved at least 5 times in different groups of sharks and rays [2]. But what do sawfishes, sawsharks, and Schizorhiza have to do with actual teeth?

Ever had the chance to touch a shark or ray?  They’re skin is not scaleless, but covered in minute, hook-shaped denticles (placoid scales). If you brush your hand away from the head, the skin feels smooth, but if you reverse and brush towards the head, your skin will catch on these tiny hooks, like velcro. The internal structure and composition of these hooks is not dissimilar to that of teeth, and it has been long hypothesized that in the earliest jawed vertebrates these denticles migrated into the jaw region, and eventually evolved into oral dentition. I was taught this “outside in” hypothesis, that teeth are a specialized, derived form of those dermal denticles that cover the skin of sharks, rays, and other cartilaginous fishes. But this hypothesis has been called into question by several researchers, including Underwood and his colleagues. They have published a series of papers (linked below) that have been testing and comparing how teeth develop during ontogeny, and how that compares to they way dermal denticles and “saw-teeth” develop.

So far, the team has examined the morphology of teeth and denticles and several cartilaginous fishes, as well as the genetic controls that dictate the order and development of oral dentition, and they have determined that dermal denticles and oral dentition may not have the same evolutionary origin. Chondrichthyans are polyphyodonts, meaning that their teeth are

Examples of unusual batoid jaws from Underwood et al. 2015 [1], showing clear morphological differences. The batteries of teeth rotate from inside the mouth to outside as the rays age.
Examples of unusual batoid jaws from Underwood et al. 2015 [1], showing clear morphological differences. The batteries of teeth rotate from inside the mouth to outside as the rays age.

continuously replaced in a “many-for-one” style of replacement, and sharks and rays are noted for their batteries of teeth, which develop lingually and move to the functional surface (i.e., the mouth margin for munching on prey) and, if not lost, will continue to rotate outside of the functional surface. Batoids also often display a variety of unusual morphologies to exploit different food sources [1].

In contrast, denticles do not follow this ordered pattern of replacement seen in the dentition. Rather, denticles develop as space becomes available (i.e., as the organism grows), and are only replaced as denticles are lost, in contrast to chondrichthyan teeth that grow regardless if its predecessor is lost or not.

So, does “saw-tooth” development resemble what is observed in dermal denticles or oral dentition? Welten et al. [2] examined this and noted two differences between sawfishes, sawsharks, and sclerorhynchids. Sawsharks and sclerorhynchids share a similar pattern, despite not being closely related: the saw-teeth develop under the skin of the embryo before “swinging” laterally into place along the rostrum, and are only replaced when the predecessor is lost. In sawfish, however, the prominent saw teeth fit into sockets within the rostrum and grow continuously. If a saw-tooth is lost, it is not replaced (bad luck, sawfish). The development of saw-teeth is associated with rostrum growth, and replacement is space-dependent, thus “saw-teeth” aren’t teeth, at least in the classical sense, and are more comparable to dermal denticles.

We’re back to Schizorhiza, the unusual ray from the Cretaceous of Morocco that was the subject of Underwood’s talk at SVP.

When I asked Underwood about collecting specimens of Schizorhiza, he told me, “The specimens all came from the phosphate mining area near Khouribga, Morocco. In this area sedimentary phosphorites form a unit about 10 meters thick but representing maybe 15–20 million years from latest Cretaceous to Early Eocene. The whole rock, including fossils, is ground up to make fertilizer, but locals, mostly the quarry workers, try to collect larger fossils as they emerge, especially mosasaurs in the Cretaceous and crocodiles, turtles, and large sharks in the Paleocene and Eocene. In the process, some rare specimens are collected, such as pterosaurs, birds, land mammals and Schizorhiza. These fossils are purchased by local wholesalers who prepare the fossils and sell them on to museums and collectors. Whilst a lot can be said against commercial trade in fossils, this is really a rescue operation, and it only happens because there is a market for the fossils.”

Mosasaur fossils in a warehouse in Morocco, still in their plaster jackets.
Mosasaur fossils in a warehouse in Morocco, still in their plaster jackets.
Schizorhiza fossils provide a high amount of developmental data, which is unusual for a fossil and beneficial for testing the relationship (or lack thereof) between the development of teeth, dermal denticles, and saw-teeth.

A complete rostrum from Cretaceous Schizorhiza stromeri (specimen NHMUK PV P.73625), with close-up images of the alternating saw-teeth and their deeply lobed roots. From Smith et al. 2015 supplement [3]
A complete rostrum from Cretaceous Schizorhiza stromeri (specimen NHMUK PV P.73625), with close-up images of the alternating saw-teeth and their deeply lobed roots. From Smith et al. 2015 supplement [3]

Multiple specimens were examined via volume-rendered and segmented micro-CT scans and histological thin sections. The saw-teeth of Schizorhiza differ from what is observed in sawfish and sawsharks; the saw-teeth form a continuous battery of staggered structures to create a functional saw-edge, with smaller teeth nearer the far end of the snout but not reaching the very tip of the rostrum. Each tooth has a small crown and a root with four deep lobes that would have extended into cartilage along the rostrum edge. New saw-teeth develop internally at the rostrum edge and point towards the skull, and as they develop they rotate laterally and finally end up in below older teeth, within the root space left by the older teeth. These teeth would then remain there waiting to replace their predecessor, a process that is more common in bony fishes but otherwise unknown in chondrichthyans.

Micro-CT scans of the rostrum of Schizorhiza stromeri (specimen NHMUK PV P. 73626), color coded to show the difference in different ages of files of teeth.
Micro-CT scans of the rostrum of Schizorhiza stromeri (specimen NHMUK PV P. 73626), color coded to show the difference in different ages of files of teeth, and showing in (a) that new teeth point caudally (green), rotate laterally (purple), and then point outward (red). (d and f) show how newer teeth reside in the root cavity of older teeth. From Smith et al. [3]
The origin of development of rostrum saw-teeth appears to begin at the symphyseal (center) tip of the rostrum, which is similar to the way that the oral dentition develops in sharks and rays. Schizorhizacreates a bit of a paradigm, with saw-tooth development that resembles the way teeth develop in sharks and rays, though the study concluded that the method of development is merely convergent, and that the saw-teeth in Schizorhiza are modified skin denticles, as what is shown in sawfishes and sawsharks.

Schizorhiza provides a great example of why scientists should continuously question and test ideas that are long taken for granted. The specimens are absolutely stunning and allow Underwood, Johanson, and their team to demonstrate that the origin of saw-teeth, oral teeth, and dermal denticles in sharks and rays, don’t represent as “cut and dry” a story as we all have assumed. Read their papers below and follow along as they continue to research the mystery of the “saw-slashing” fishes.

[1] Underwood CJ, Johanson Z, Welten M, Metscher B, Rasch LJ, Fraser GJ, Smith MM (2015) Development and Evolution of Dentition Pattern and Tooth Order in the Skates and Rays (Batoidea; Chondrichthyes). PLoS ONE 10(4): e0122553. doi:10.1361/journal.pone.0122553

[2] Welten M, Smith MM, Underwood C, Johanson Z. (2015) Evolutionary Origins and Development of Saw-Teeth on the Sawfish and Sawshark Rostrum (Elasmobranchii; Chondrichthyes) Royal Society Open Science 2: 150189. doi:

[3] Smith MM, Riley A, Fraser GJ, Underwood C, Welten M, Kriwet J Pfaff C, Johanson Z. (2015) Early Development of Rostrum Saw-Teeth in a fossil ray tests classical theories of the evolution of vertebrate dentitions. Proceedings of the Royal Society B 282: 20156128.

Source: The “Slasher” Ray: An extinct fish with a saw-like nose | PLOS Paleo Community


Laser-Stimulated Fluorescence in Paleontology — PLOS Paleo Community

A new technique can be used to examine even the tiniest of details on fossils.

This is a blog post I wrote for the PLOS Paleo Community on October 4, 2015 and am archiving here on my website.  The original post can be accessed here.

On Wednesday, October 7, 2015, PLOS Paleo hosted a redditscience ‘Ask Me Anything’ on  laser-stimulated fluorescence (LSF) in paleontology. [Here’s a link to the completed AMA.]

Our featured paleontologist for this AMA was PLOS author Thomas Kaye, a Research Associate at the Burke Museum in Seattle, Washington. Kaye and co-authors (Amanda R. Falk, Michael Pittman, Paul C. Sereno, the late Larry D. Martin, David A. Burnham, Enpu Gong, Xing Xu, and Yinan Wang) have developed a pretty impressive, non-invasive technique to examine fossils in ways we might not have really considered, using equipment that is readily accessible to any paleontologist. Let’s discuss…

For decades paleontologists have used and manipulated different modes of lighting to examine fossils. Something as simple as moving a flexible arm lamp so that it casts light across a specimen laterally rather that directly down upon it can make surface features of a fossil “pop” — and pretty common when, like me, you work on flattened specimens like fish fossils and are desperate for some surface topography. Paleontologists also use fluorescence to examine specimens by casting UV light upon a fossil, causing some minerals, such as hydroxyapatite or fluorite, to absorb UV wavelengths and emit light in a different wavelength. This produces those lovely bright colors that make the fluorescing fossil stand out from the darker rock matrix, and thus allowing the scientist to recognize morphological characters that are otherwise unseen in normal light with little contrast against the matrix.

Still these traditional methods are limited for some specimens, particularly if you have fossils that don’t fluoresce under standard UV light or your are trying to examine soft-tissues or details that are fairly close in color to the matrix or obscured by matrix. Kaye et al.’s paper describes a next-generation technique using stronger laser tools to look for characteristics in a fossils that would have otherwise remained unseen using older techniques. As for the specifics of LSF, I am not an expert and I urge you to read the paper yourself, but let’s talk about some of the great case studies that this paper provided, giving paleontologists and paleoanthropologists all kinds ideas for using LSF.

An unidentifiable specimen from a Liaoning rock slab containing a Microraptor specimen.
An unidentifiable specimen from a Liaoning rock slab containing a Microraptor specimen.

I spoke with one of the paper’s co-authors, David Burnham, the Fossil Preparation Lab Manager at the University of Kansas (KU), and he gave me a little backstory about his involvement with LSF. He and Larry Martin, the late Curator of Vertebrate Paleontology at KU, had found a mystery fossil on a slab containing a Microraptor, but the visible bones were small and identification proved difficult.

Martin had known Kaye and the techniques he had been developing, so they sent the slab to Kaye to analyze, and using this newly-developed LSF technique, they were able to identify the specimen as a fish, and even were able to recognize teeth, scales, and other bones that would have remained invisible to Martin and Burnham without the use of lasers.

Specimen under (A) White light photo and (B) fluorescence with a 457 nm blue laser. LSF showed fish teeth (indicated by arrows), bones, and scales nearly invisible under white light.
Specimen under (A) White light photo and (B) fluorescence with a 457 nm blue laser. LSF showed fish teeth (indicated by arrows), bones, and scales nearly invisible under white light.

Likewise, Amanda Falk, a Visiting Assistant Professor of Biology at Centre College in Danville, Kentucky and co-author on the paper, needed a better way to decipher primitive bird plumage on a fossil and began working with Kaye. Other techniques, such as scanning electron microscopy (SEM) really only detail surface topography, and to better see the barbs and barbules of the feather, Kaye and Falk use LSF in a different way by shining the laser on the fluorescent carbonaceous matrix, thus ‘backlighting’ the feathers.

Feather structure comparison using white light (A), polarized (B) and laser illumination (C), showing how LSF provides a silhouette of the feather barbules by backlighting the specimen.
Feather structure comparison using white light (A), polarized (B) and laser illumination (C), showing how LSF provides a silhouette of the feather barbules by backlighting the specimen.
“I think it [LSF] has excellent utility in a variety of lab situations,” Burnham said, “I have used the laser on rock samples as well with very good luck. The laser illuminated the volcanic constituents in the sediment really well so it was helpful to illustrate the amount of that material and how it was distributed in the rock.” LSF can also be used to sort microfossils, and this technique is laid out wonderfully in the paper. Kaye and co-authors were even able to automate the process with success.

A mid-Holocene-aged Gobero skeleton of a small girl preserved wearing an arm bracelet.
A mid-Holocene-aged Gobero skeleton of a small girl preserved wearing an arm bracelet

LSF is not limited to geochemical and paleontological studies. Paleoanthropoligsts can take advantage of the LSF technique to examine sensitive specimens. The Kaye et al. paper outlines a case where a mid-Holocene female skeleton had a bracelet around her upper arm, but removing the bracelet was impossible without destruction to the skeleton.

A laser was scanned over the artifact, and revealed details that allowed the scientists to determine that the bracelet was made from a hippopotamus tusk.

Bracelet under normal light (A), and fluorescing under a hand-scanned laser (B). The cracking pattern in the upper left corner is only visible under fluorescence and aided in the identification of the bracelet material as hippopotamus tooth.
Bracelet under normal light (A), and fluorescing under a hand-scanned laser (B). The cracking pattern in the upper left corner is only visible under fluorescence and aided in the identification of the bracelet material as hippopotamus tooth.

Interested in this technique for your own specimens? Lucky for you, the equipment and lasers are relatively inexpensive and available. A cheap, everyday laser pointer won’t cut it, though. “We found that the power of the laser was important, so everyday laser pointers were not enough,” Burnham told me.

“I used [a] 400 mW laser pointer,” Falk added, “The trouble with the laser pointer is that it can only be used for about five minutes before you need to turn it off and cool it down. If you want continuous use of the laser then you need a lab-grade laser. We bought a 300 mw one, which [cost] about $500 and not that bad. These are really affordable…in short you can get a working [LSF] system in your lab for less than a thousand dollars. The more powerful the laser, the brighter the fluorescence. Just remember to buy eye protection, too!”

Burnham echoed his sentiment about lab safety, “…One should use caution as the lasers can damage your eyes, and correct protection (safety glasses matched to laser type) must be used. I think the only other drawback is getting the specimen in a room with no light.”

Source: Laser-Stimulated Fluorescence in Paleontology | PLOS Paleo Community

Oldest direct evidence of humans in the Americas? — PLOS Paleo Community

A discovery in an underwater cave in Mexico may indicates the earliest human settlers of the Americas.

This is a blog post I wrote for the PLOS Paleo Community on August 30, 2017. The original post can be accessed here.

Featured Image Credit: Nick Poole and Thomas Spamberg, Liquid Junge Lab. CC-BY.

When did humans really arrive in the Americas? It has been a subject of a lot of debate by archaeologists and paleoanthropologists, For decades, it was generally accepted by most that around 13,000 years ago, the Bering Strait opened up enough (as in, became ice-free) for humans to traverse across from Asia into North America before spreading southwards. But as more and more pre-Clovis archaeological remains were discovered, paleoanthropologists came to a consensus that human arrival in the Americas could have been as early as 22,000 years ago. A more recent study published earlier this year in Nature gave a new oldest estimate that is 100,000 years older than all previous estimates placing human presence in the Americas, but is based solely on markings on mastodon bones and not on actual human bones. Critics of that study suggest that the markings cannot be definitively attributed to humans and could have been made naturally by rocks or other erosional processes.

Regardless, the oldest claims for humans in the Americas is based on tools, artifacts, scraps, and very little is based on osteological remains. When bones are found, they are often very fragmentary. A new paper, published today in PLOS ONE by Stinnesbeck et al., discusses some well-preserved human remains that were discovered in a submerged cave system in the Tulum area of southern Mexico.

The remains were first brought to the attention of the researchers in 2012 through social media. From the photographs of the site, it was clear that about 80% of the skeleton remained intact and partially articulated, including a skull and limbs. Unfortunately, about a month after first publicized on social media, the site was vandalized, and most of the bones were stolen, leaving only about 10% of the skeleton, mostly scrappy parts that were inaccessible to the vandals.

A) The skeleton in situ prior to its theft and vandalism; B and C) photographs showing bones before and after the theft, the orange arrow indicates the stalagmite growing out of the pelvis used for dating the skeleton. From Stinnesbeck et al. (2017). CC-BY.

The researchers were able to reconstruct the position of the skeleton based on interpretation of the photos. And visiting the site, they were able to collect many bones and bone fragments. Of particular note is a part of the pelvis that was firmly attached to the substrate due to the growth of a stalagmite.

It was this stalagmite that became important in dating this skeleton. Other human remains have been discovered previously in Tulum, and were carbon-dated to about 10,976±20 y BP to 11,670±60 y BP. However, this new study suggests that the bioapatite used for previous studies should be used with caution, as it is susceptible to contamination.

Different views of the Chan Hol II pelvis within the CH-7 stalagmite. Arrow in Fig A points to the CH-7 stalagmite prior to the robbery of the skeleton. From Stinnesbeck et al. (2017). CC-BY.

Instead, Stinnesbeck et al. (2017) used U-series techniques to date the skeleton. The U/Th samples were taken from the stalagmite that was growing through the pelvic bone, with samples taken adjacent to the bone both above and below. Using mass spectrometry, the data indicates that the skeleton from the Chan Hol underwater cave is approximately 13,000 years old, thus representing one of the oldest ages of a human present in the Americas, based on definitive direct osteological evidence.

At the time during the Late Pleistocene, this cave would have been dry and accessible, with the sea level more than 100 meters below its current level. This skeleton, along with other remains found in the Chan Hol cave system, could represent an early human settlement along the sea. The karst labyrinth of caves were later flooded, thus preserving the archaeological and paleoanthropoligcal remains inside.

Though it is unfortunate that the site was looted, the results of this study based on what was left behind give clear evidence and possibly a new understanding of the earliest settlements in Mesoamerica.


Stinnesbeck W, Becker J, Hering F, Frey E, González AG, Fohlmeister J, et al. (2017) The earliest settlers of Mesoamerica date back to the late Pleistocene. PLoS ONE 12(8): e0183345.

The Man on the Hill: A Geologic Mystery Solved over Breakfast

A historic photo from my hometown opens up a mystery of geologic proportions.

This is an old post that was found on my previous website. I am archiving it here, it was originally published in December 2015.

This morning, while enjoying my breakfast, drinking coffee, and reading my hometown newspaper, The Nephi Times-News, I was intrigued by an old photo of an unidentified man, wearing dusty overalls and standing on an outcrop of rock in the foothills of a mountain. Behind him, a large “N” emblazoned on the hill. The photo was ran by the newspaper as part of their “Blast from the Past” feature, essentially a #ThrowbackThursday featuring vintage images of people and the area brought in by members of the community. (As a sidenote that really has nothing to do with this post other than the fact that I’m still reading my hometown paper, the Times-News has been run by my family for ~5 generations, my father and sister are currently the Publisher and Editor, respectively.)

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The photo caught my eye. It is a captivating image in itself. I’ll never know who the man is. But the geologist in me is wondering where he is and what he is doing. So, I poured myself another cup of coffee and decided to chase this little mystery.

I grew up in Nephi, Utah (a small community of around 5,000 people), in the shadow of Mount Nebo. Mt. Nebo is the southernmost and also the tallest mountain of the Wasatch Range (at a modest elevation of 11,928 ft/3,636 m above sea level). I’d recognize Nebo anywhere, having spent a lot of time hiking its lower slopes, playing in its canyons, and admiring its geology and wilderness. Nebo is like an old friend that never changes (well, incrementally changes over geologic time, anyways).

The mountain in the far background of the image is Nebo’s southern slope, and is what is most visible to the residents of Nephi (the actual peak is farther north, closer to Mona, Utah).

Now, non-westerners might be wondering, what’s up with the “N” on the hill? Something that was so common to me growing up in Utah is like some wacky mystery to others not from a mountainous region (this is based upon my experience in the midwest). So, to give a quick and dirty explanation: in most cases in Utah, the letters represent the nearest highest-level school. For example, if you find yourself in Provo, Utah, the highest-level school is Brigham Young University, symbolized by a giant “Y” on the hill. In Nephi, the highest-level school is the local high school. It’s just some way of establishing territory/dominance/school pride by the local community.

The current “J” on the hill for Juab High School, Nephi, Utah

According to The Times-News, the “N” stands for Nephi High School, which was the name of the school until 1932, when it was changed to Juab High School (for Juab County), my alma mater. (Go Wasps!) So that gives this image a minimum age of 1932. Mystery 1 solved, sort of. I’m sure someone could analyze his clothing or hairstyle, or the type of film used to figure out a more precise age of the photo, but out of my realm.

Mystery 2: the placement of the “N.” What was most obvious to me is that the “N” is in the wrong place. Now, of course the “N” isn’t there anymore; when it changed to JHS obviously the letter on the hill was changed to a “J” where still today the seniors of the high school give it a fresh coat of paint each year during homecoming week. But the “J” is on a much lower hill, closer to the freeway. This “N” seems higher, and doesn’t feel right to me. Where is it exactly? Enter Google Earth. Using the shape of Nebo and the foothills, and exposed geologic outcrops, I figured it out. Although the image is in black and white, there is a obviously change in the texture and color along the lower left of the hill and it’s lower slopes. The “N” is obviously on the that flattened/smooth part of the hill spur, far away from where the current “J” is! Mystery 2: solved definitely!

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Mystery 3: Where is the man and why is he so dusty? My first inclination is that he’s mining gypsum. At the mouth of Salt Creek Canyon (which runs east of Nephi, through the mountains south of Nebo and into Sanpete Valley), there is a gypsum mine that has been operational since its discovery in 1889. However, this man is not at the large gypsum mine, but at some small outcrop north of the mine in the canyon. I pinpointed my guess of his location below.

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Thankfully, the Utah Geological Survey provides interactive topographical geologic maps, so one I had used Google Earth to approximate his location, it was very easy to see that he was standing in a smaller, northern exposure of the same gypsum deposits, which are in the Arapien Shale. The Arapien Shale is middle Jurassic in age, and comprises mudstones, shales and some limestones rich with evaporites, such as salt and gypsum. Pioneers that first settled the area noted the salty creek (hence Salt Creek Canyon), and traced the origin of the salt back to some of these salt deposits in the Arapien, where they are also mined in addition to the gypsum.

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The interesting thing about the Arapien Shale is that it was severely deformed and twisted during the Sevier Orogeny (mountain-building) event that created the Wasatch mountains during the Cretaceous and Tertiary. Some of the thrusting and folding (yes, I am aware of all of the geologic innuendo!) caused the Arapien Shale to break and be thrust upon itself, causing some repeated sequences that were then uplifted and exposed, thus creating the lucrative mining operations for the Nephi community and mining companies.


Likely this guy was a miner for one of these salt or gypsum operations in the early 1900s. Maybe he was exploring some of these northern deposits, in hopes of staking a mining claim of his own? As far as I know, the gypsum is really more lucrative on the south side of the canyon, and I’m unaware of any mines to the north of the canyon in the southermost foothills of Nebo, though I do know that there are some other mines on the western slopes of Nebo (because I went sledding there as a kid).

So that’s that. A seemingly simple photo of a man, but teeming with geological conundrums, Utah pioneer history, and an answer that seems obvious to any Nephite that might be reading this post. But it was fun to solve anyways.

Back to my coffee.

New Paper: Evolution of multicuspid teeth in a Triassic fish from Utah

An enigmatic holostean from the Triassic of Utah possesses an unusual tooth morphology. What was the purpose of these teeth?

This is an old post I am archiving here on my website. It was originally posted on the KU Biodiversity Institute blog in February 2015.

Just yesterday, my newest paper was published online in the journal The Science of Nature: Naturwissenschaften about a rather unusual fish from the Upper Triassic Chinle Formation of southeastern Utah. The fish, Hemicalypterus weiri, was a deep-bodied, disc-shaped fish, with enameled ganoid scales covering the anterior portion of its flank, and a scaleless posterior half, which presumably aided in flexibility while swimming. Although Hemicalypterus was first described in the 1960s (Schaeffer, 1967), recent collecting trips recovered many new specimens of Hemicalypterus, and I decided to reinvestigate this enigmatic fish as part of my dissertation research.

Holotype of Hemicalypterus

While cleaning specimens of Hemicalypterus at the University of Kansas Vertebrate Paleontology prep lab, I noticed rather unusual teeth on the lower jaw that I had exposed from the rock matrix. These teeth look like a mouthful of little forks, and there were at least six individual teeth on the lower jaw. As I prepared other specimens, I found that these teeth were also on the premaxillae. Each tooth has a long cylindrical base and a flattened, spatulate edge with four delicate, individual cusps. I hadn’t seen anything like this before in other fossil fishes, and so I started searching the literature and talking to other ichthyologists.

Multicuspid teeth of Hemicalypterus

Well, as it turns out, this tooth morphology has evolved multiple times in several independent lineages of teleost fishes, and quite often fishes with similar dentition scrape algae off of a hard substrate. These teeth indeed act like little forks (or “sporks” might be more appropriate) for these herbivorous/omnivorous fishes. Examples of extant fishes with similar teeth include freshwater forms such as the algae-scraping cichlids and characiforms, as well as many marine forms that are key in controlling algae growth in coral reef environments, such as acanthurids (surgeonfishes, tangs) and siganids (rabbitfishes). Of course, these modern-day fishes also feed on other things (e.g., phytoplankton), but algae is often the primary staple, and these fishes use this specialized dentition for a specific feeding behavior.

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Multicuspid teeth of Labeotropheus, an algae-scraping cichlid.

So while it is impossible to prove definitively what a species of fish that lived over 200 million years ago fed upon (without gut contents being preserved….or a time machine), it is still safe to infer that Hemicalypterus occupied an ecological niche space similar to algae-scraping cichlids or other modern-day herbivorous fishes and may have scraped algae off of a hard substrate, based on this unusual tooth morphology and its similarity to modern forms.

This discovery also extends evidence of herbivory in fishes clear back to the Early Mesozoic, whereas prior to this discovery it was assumed that herbivory evolved in the Middle Cenozoic in marine teleost fishes. Frankly, there was no evidence to say otherwise, as most Mesozoic fishes have general caniniform or styliform (peg-like) teeth, or they have heavy crushing or pavement-like teeth consistent with crushing hard-shelled organisms. The teeth of Hemicalypterus are very delicate, and wouldn’t really do well with durophagy. This is the first potential evidence of herbivory in the Mesozoic, and in a non-teleost, ray-finned fish.

Original Source: Gibson, S.Z. 2015. Evidence of a specialized feeding niche in a Late Triassic ray-finned fish: evolution of multidenticulate teeth and benthic scraping in †Hemicalypterus. The Science of Nature — Naturwissenschaften 102:10.

Also cited: Schaeffer, B. 1967. Late Triassic fishes from the western United States. Bulletin of the American Museum of Natural History 135: 289–342.

Behind the Research: Identifying a New Species of Fossil Fish

How does a paleontologist identify a new species?

This is an old post I am archiving here on my website. It was originally posted on the KU Biodiversity Institute blog in October 2014.

A fundamental part of being a scientist is publishing your research. Scientists ask questions, formulate hypotheses, rigorously test these hypotheses, and publish their research and their results. Other people can then read these results and build off of these studies, either to question or refute the findings, or to use the findings to ask other questions. It is how science grows and evolves.

What almost all scientific publications lack, however, is the flair, the backstory, and general behind-the-scenes action that is part of everyday research. Scientific publications are whittled down to the most concentrated version, filled with the jargon of the discipline, and stripped of any extraneous behind-the-scenes anecdotes. So while any given scientific paper can be exciting to a scientist who wants to learn more about the organism or the methods addressed, they can be a bit unfriendly to a general reader.

So for fun, I have decided to tell some behind-the-scenes stories of the research I do, in the context of my published papers. Hopefully I give you a sense of what it is really like to be a paleontologist, and the work that is involved.

I’ll begin with my two solo-authored papers that I published in 2013. The papers can be found here and here, and if you cannot access those journals, please contact me and I will send you a PDF.

These two papers establish a new genus and two new species of fishes within a group called semionotiforms. Semionotiforms are an extinct group of fishes, but are closely related to living gar, and like gar, their bodies were covered with thick enamel scales (ganoid scales). Semionotiforms are found in geologic deposits worldwide, and range in age from Middle Triassic (~237 million years ago) to Early Cretaceous (~145 million years ago). A lot of variety occurs in semionotiforms in the shape of the body, the characteristics of the skull, the teeth, etc., and part of my research is to figure out what makes these particular fishes different from other species that have been described in the literature by other scientists. So you could say that my hypothesis for these studies is that these fishes represent new species, and I am testing that hypothesis by comparing the anatomy and morphology of these fishes to other semionotiform fishes to see if my hypothesis is correct or incorrect.

Some of the fossil specimens I work on are from museum collections, such as the American Museum of Natural History (AMNH) and the Smithsonian and were collected in the 1950s and 1960s, yet remained in these collections unstudied and undescribed for decades. I began working on these fishes in 2006, when I worked at the St. George Dinosaur Discovery Site (SGDS) as an undergraduate student intern and later as the prep lab and collections manager. The crew of staff and volunteers from SGDS had just gone out to a site in southeastern Utah and collected hundreds of fossils (outlined in Milner et al., 2006), but most of these fishes were not identified. So as I started cleaning the fossils (fossil prep—to be discussed in a later blog!), I started looking for characteristics that defined them as either new or belonging to a described species of semionotiform fish. While I worked on the new specimens, I looked at older literature, in particular a (1967) paper by an AMNH paleontologist Bobb Schaeffer, who mentioned collecting many semionotiforms from the same area but didn’t describe them or give them names. So, in 2008, I went to the collections of the AMNH to look at those old specimens collected decades before and reexamined them, seeing which of them could be the same species as the new specimens the SGDS crew had just collected. I identified at least two different species, though there are likely more than that.

Now, identifying a new species is more than just a “Eureka!” moment. A scientist cannot know what is new unless he/she knows what already exists, and so scientists have to be very familiar with other scientists’ work in the field. An inordinate amount of any scientist’s time is spent reading books and papers, and I spent months pouring over scientific literature, some as old as 1820, to find the characteristics of other semionotiforms. As I looked at each bone on the fossil fishes from the AMNH and those newly collected from SGDS, I compared it to the same bones in other semionotiform fishes, and I had to look for similarities and differences. Eventually, I found a suite of anatomical and morphological characters that distinguished these fishes from all other semionotiform fishes, and I had enough to publish two papers on two distinct species. In these papers, I had to give an exhaustively detailed description of every single bone, and I mean EVERY bone (these fishes have hundreds of bones, dozens in their skull alone!) that I could see on the specimens, because other scientists, when trying to identify new species of their own, may turn to my work for comparison, and so my papers have to be provide as much anatomical detail as possible!

Next time….naming a new species!!


Gibson, S.Z. 2013a. A new hump-backed ginglymodian fish (Neopterygii, Semionotiformes) from the Upper Triassic Chinle Formation of southeastern Utah. Journal of Vertebrate Paleontology 33: 1037–1050. 

Gibson, S.Z. 2013b. Biodiversity and evolutionary history of †Lophionotus (Neopterygii: †Semionotiformes) from the western United States. Copeia 2013: 582–603.

Milner, A.R.C., Mickelson, D.L., Kirkland, J.I., and Harris, J.D. 2006. Reinvestigation of Late Triassic fish sites in the Chinle Group, San Juan County, Utah: new discoveries. In: A Century of Research at Petrified Forest National Park: Geology and Paleontology (Eds. Parker, W.G., Ash, S.R., and Irmis, R.B.). Museum of Northern Arizona Bulletin 62: 163–165.

Schaeffer, B. 1967. Late Triassic fishes from the western United States. Bulletin of the American Museum of Natural History 135: 289–342.