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?

Gibsonlogoblank
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.”

203365_5658200934_o.jpg
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.

19468274508_d8c26579d2_o
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.

USNM V 23425A_MERGED_0
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:

GWW_nav1
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.

salute.jpg
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.

steed.jpg
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.

lucky.jpg

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

References:

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.

SaveSaveSaveSave

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.

References:
[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:http://dx.doi.org/10.1098/rsos.150189

[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. http://dx.doi.org/10.1098/rspb.2015.1628

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