The (Now Older) Age of Fishes: New bony fish from the Silurian of China | PLOS Paleo Community

This is a blog post I wrote for the PLOS Paleo Community, and was published in March 2017. I am archiving it here on my personal website. The text has been slightly modified. You can see the original post here.

For all of the love and popularity that the “Age of Dinosaurs” receives, we wouldn’t be where we are without evolutionary innovations that occurred during the “Age of Fishes.” The Devonian Period (419.2–358.9 million years ago) witnessed a great increase in global abundance and diversity of jawed vertebrates. But a recent study presents evidence that early jawed fishes may have evolved earlier, in the Silurian Period (443.7–419.2 million years ago), with China at its epicenter.

The study, published in PLOS ONE by Brian Choo from Flinders University, Australia, with colleagues from the Institute of Vertebrate Paleontology and Paleoanthropology, China, describes a new fossil from the Kuanti Formation of Yunnan, southwestern China. The fish, dubbed Sparalepis tingi, is based on a beautifully-preserved and articulated partial specimen, and supports the idea that this area of Asia may represent an early boom of diversification of bony fishes, long before the Devonian “Age of Fishes.”

sparalepis fossil
The holotype of Sparalepis ting (V 17915), from Choo et al. 2017.

The Kuanti Formation (~423 Ma) is rich in marine fossils: corals, molluscs, trilobites, as well as several various groups of fishes, including placoderms, acanthodians, and osteichthyans. Only until recently, however, the knowledge of fishes from this formation was based on highly fragmentary material. For example, one bony fish from the Kuanti, Naxilepis gracilis, is based solely on isolated scales. Another osteichthyan, Megamastax amblyodus, is large but fragmentary.

Then in 2009, Min Zhu (second author in this study) and colleagues described Guiyu oneiros, the oldest articulated bony fish with a mosaic of gnathostome characteristics, including some characteristics that were once attributed solely to placoderms. In 2013, Zhu et al. then published Entelognathus, a maxillate placoderm. These taxonomic studies are based on fantastically-preserved specimens from the Kuanti Formation, and with this study (published in 2017), Sparalepis becomes the third articulated specimen from the Kuanti Formation, and only second known articulated Silurian osteichthyan.

sparalepis scales
Diagrammatic reconstruction of Sparalepis, and examples of scales preserved. From Choo et al. 2017

Sparalepis is named after the Sparabara infantry during the Persian Empire due to the similarity of the shape of the scales of the fish to the shape of the wicker sheilds carried by the Sparabara. The scales are particularly tall, thick, and narrow with distinct interlocking articulation mechanisms. Sparalepis is represented by a partial postcranium, body scales, and some fin elements. The pectoral girdles bear large fin spines, as well as large dorsal fin spines beautifully preserved in the holotype.

A lot of these characters observed in Sparalepis are shared with Guiyu, in particular the spine-bearing pectoral girdle and placoderm-like, dermal pelvic girdle. These articulated specimens from the Silurian helped the researchers solve another fishy mystery, by helping them definitively identify isolated elements from the Devonian Xitun Formation in Yunnan, attributing them to the enigmantic taxon Psarolepis. (Zhu et al. 2012)

So what sets Sparalepis aside from Guiyu and Psarolepis as a distinct species? Sparalepis possesses prominent linear ridges and pore openings on the dermal surfaces of all of the larger bones and median scutes are unique to Sparalepis and lacking in Guiyu. The scale ornament of Sparalepis and Guiyu are similar to each other, and different of that seen in Psarolepis.

What is important to note about these fishes is that they display characteristics that were once thought to be isolated to placoderms. The mosaic of characters seen in Sparalepis and Guiyu has caused questions regarding previous evolutionary hypotheses of relationships between placoderms, sarcopterygians, and actinopterygians.

The team sought to address the relationships of these enigmatic fishes, and provided a dataset to test their phylogenetic hypothesis. Their results suggest that Sparalepis is closely related to Guiyu, Achoania, and Psarolepis; this group is recovered at the base of Sarcopterygii, in a clade that this study is putatively calling “psarolepids.” This study also provides additional support to the hypothesis that the ancestral species to gnathostomes likely possessed a placoderm-like bodyplan, and that characteristics seen in stem sarcopterygians like Sparalepis are likely plesiomorphic conditions.

So this study is helping to narrow a wide morphological gap in the early history of jawed vertebrates. And with the evidence provided by this study, we now know that that history began earlier than we thought. Thanks to Sparalepis and Guiyu, we can see that the “Age of Fishes” arrived early during the SIlurian in China.

sparalepis recon
Life restoration of Sparalepis tingi (foreground) and other fauna from the Kuanti Formation. Also in the scene are numerous conodont animals, a pair of the maxillate placoderm Entelognathus (middle distance) and two examples of the osteichthyan Megamastax (background), the largest known Silurian vertebrate. Illustration by Brian Choo, released under Creative Commons Attribution Licence CC BY 4.0, 2016.


Choo B, Zhu M, Qu Q, Yu X, Jia L, Zhao W (2017) A new osteichthyan from the late Silurian of Yunnan, China. PLoS ONE 12(3): e0170929. doi:10.1371/journal.pone.0170929 

Zhu M, Zhao WJ, Jia LT, Lu J, Qiao T, Qu QM (2009) The oldest articulated osteichthyan reveals mosaic gnathostome characters. Nature 458: 469–474. doi: 10.1038/nature07855

Zhu M, Yu XB, Ahberg PE, Choo B, Lu J, Qiao T, et al. (2013) A Silurian placoderm with osteichthyan- like marginal jaw bones. Nature 502: 188–193. doi: 10.1038/nature12617 PMID: 24067611 

Zhu M, Yu XB, Choo B, Qu QM, Jia LT, Zhao WJ, et al. (2012) Fossil fishes from China provide first evi- dence of dermal pelvic girdles in osteichthyans. PLoS ONE 7: e35103. doi: 10.1371/journal.pone. 0035103 PMID: 22509388 

via The (Now Older) Age of Fishes: New bony fish from the Silurian of China | PLOS Paleo Community

Alamosaurus: how this massive titan’s neck is impacting relationships of titanosaurs | PLOS Paleo Community

This is a blog post I originally wrote for the PLOS Paleontology Community blog, and am archiving it here on my personal website. You can find the original post here.

Remember the Alamo? Well, it’s easy to forget when you are staring at this massive dinosaur. It makes that Tyrannosaurus look like a puppy in comparison.

Alamosaurus on display at the Perot Museum. Photo by Sarah Gibson, taken during the SVP opening reception, October 2015.

At least that was how I felt when seeing the Alamosaurus on display at the Perot Museum of Nature and Science. I, along with hundreds of paleontologists at the 2015 Society of Vertebrate Paleontology meeting in Dallas, got to admire this beautiful behemoth at the opening social. Alamosaurus has a great and complex history to match its size, and now, with a new study by Ronald S. Tykoski and Anthony R. Fiorillo published open access this week in the Journal of Systematic Paleontology, Alamosaurus now comes with a more complete anatomical and morphological description, and a new hypothesis of how Alamosaurus relates to other titanosaurs.

“Giant sauropods like Alamosaurus have amazed people since the 1800s.  Their sheer size boggles the mind, and they have forced scientists to re-think the physical limits of land-living animals,” said Tykoski.  “The fossils described in our paper reveal new details about the last sauropods in North America, which helps us better understand who Alamosaurus was related to and how this species made it to southern North America by 67 to 66 million years ago – just in time to go extinct at the end of the Cretaceous!”
The Ojo Alamo Trading post circa 1911, before Alamosaurus was even discovered. Bones be out there, somewhere… Image courtesy the Farmington Museum

Now, Alamosaurus was not named after the THAT Alamo. Rather it was named for the Ojo Alamo trading post in New Mexico, where bones of the sauropod were first discovered in the 1920s. Since then, other remains have been discovered in Utah, Texas, and New Mexico. Most of these discoveries, however, were incomplete sections of the dinosaur, and so the whole picture remained elusive and its relationship to other titanosaurs was difficult to interpret.

In 1997, a joint team of paleontologists from the University of Texas at Dallas (UT-D) and the Perot Museum of Nature and Science found additional remains of Alamosaurus in Big Bend National Park. The scientists and volunteers were excavating a site that produced parts of several immature sauropods when Dana Biasatti, then a student at UT-D, came upon the remains of an adult titanosaur a few hundred yards away. The team was stunned. The nine cervical (neck) vertebrae were the first articulated series of adult Alamosaurus neck bones ever found. The fossils of Alamosaurus from Big Bend National Park currently represent the biggest dinosaurs discovered in Texas.

It would be another four years before they were able to excavate the remains, however. Working with the National Park Service and a helicopter service, several blocks, some weighing over a ton, were airlifted out to a flatbed truck about a mile away, and then transported over 500 miles to the Perot Museum in Dallas. The bones have been prepared and are now on display under the reconstructed Alamosaurus in the museum, which spans over 25 feet.

Airlifting the remains of Alamosaurus out of Big Bend National Park. Image courtesy the Perot Museum of Nature and Science.

“This remarkable discovery illustrates the importance of America’s public lands as places where scientists have access to perform research that benefits everyone,” said Cindy Ott-Jones, Superintendent of Big Bend National Park. “While Big Bend National Park is a place that many people enjoy for its scenery and recreational opportunities, visitors should know that a tremendous amount of scientific research is also performed in the park.”

Because of the new anatomical and morphological information provided in the study, the authors were able to propose a a more robust hypothesis of evolutionary relationships of Alamosaurus to other sauropod dinosaurs. And the results of the phylogenetic analysis were novel; the researchers recovered Alamosaurus to the Lognkosauria clade, which includes the genera Futalognkosaurusand Mendozasaurus, both massive titanosaurs from the Cretaceous of Argentina. This new proposed relationship is supported by three shared derived characters—all characters based on the morphology of the cervical vertebrae, made possible by this discovery.

This study also has paleobiogeographical implications, mainly in why Alamosaurus is where it is at the time it is. Tykoski and Fiorillo (2016) discuss several scenarios depending on different studies, and in one scenario suggest a northward dispersal by the ancestors of Alamosaurus from South America—a hypothesis which matches their phylogeny, as its closest relatives proposed by this study are found in Argentina, it is likely their common ancestor was also from South America.

This paper is significant, and has been years in the making. The new data provided by Tykoski and Fiorillo (2016) illuminates possible evolutionary relationships of titanosaurs, and gives Alamosaurus a place on the family tree.


Ronald S. Tykoski & Anthony R. Fiorillo (2016): An articulated cervical series of Alamosaurus sanjuanensis Gilmore, 1922 (Dinosauria, Sauropoda) from Texas: new perspective on the relationships of North America’s last giant sauropod, Journal of Systematic Palaeontology, DOI: 10.1080/14772019.2016.1183150

This post was modified from materials provided by the Perot Museum of Natural History and Science

via Alamosaurus: how this massive titan’s neck is impacting relationships of titanosaurs | PLOS Paleo Community

Track Makers in Southern Utah: The St. George Dinosaur Discovery Site | PLOS Paleo Community

Featured image: Megapnosaurus model on display in front of Grallator-type dinosaur tracks at the St. George Dinosaur Discovery Site at Johnson Farm. Photograph by Sarah Gibson.

This is a post that I originally wrote for the PLOS Paleontology Community blog in May of 2016. I am archiving it here on my website, so some of my references to the 2016 SVP meeting in Salt Lake City are a bit outdated. Nevertheless, you’ll get the gist about this awesome site. You can find the original blog post here.

UPDATE August 22, 2016: It is with great sadness that we announce the passing of Dr. Sheldon Johnson last week from leukemia. You may find his obituary here, and please consider donating to the DinosaurAh!Torium Foundation, which helps fund research and preservation of tracks at the St. George Dinosaur Discovery Site at Johnson Farm.

When it comes to absolutely amazing paleontological resources, Utah arguably reigns supreme within the United States (I may be a bit biased). And with the upcoming Society of Vertebrate Paleontology meeting taking place in Salt Lake City, paleontologists and paleo enthusiasts will be flocking to the Beehive State to discuss and share the latest breakthroughs in the field. To those coming to the meeting this October, one thing I cannot stress enough: do not miss what Utah has to offer in terms of spectacular fossil sites and museums. It will be difficult to avoid, as the SVP host committee this year is offering up eleven (eleven!!!) field trips to different parts of the state to see everything from the Triassic-Jurassic transition to Mesozoic dinosaurs to Eocene fishes to Pleistocene shorelines, and more.

If you’d rather go rogue and visit some places on your own, you are greeted with a plethora of options: at least a dozen museums, five national parks and many more national monuments, and some beautiful in situ fossil localities open to visitors. I recently visited one of the more recent additions of paleo places to visit in Utah, and it’s one of my favorites as well because, well, I worked there for two years! Let me make the case for why you should consider a jaunt down to St. George, Utah and view some of the most spectacularly preserved dinosaur tracks in North America.

Dr. Sheldon Johnson pictured with one of the dinosaur track blocks in 2000. Image courtesy Andrew R. C. Milner.

Located at the southwestern tip of the state, the St. George Dinosaur Discovery Site at Johnson Farm(hereafter called SGDS) was only very recently discovered in 2000, when landowner and retired optometrist Sheldon Johnson was clearing some land for development. Overturning some large sandstone blocks, he observed natural casts of dinosaur footprints that were so detailed, he initially thought he had an actual dinosaur preserved in the rock with its foot hanging out. As he moved and overturned more blocks, he quickly realized he was looking at exquisite dinosaur trackways.

Now, here is where Dr. Johnson did a wonderful thing. Rather than destruction of the tracks in order to develop the land, he called local geologists and paleontologists, who quickly came and assessed the site. They found more of the tracksite in situ, and realized that they were dealing with multiple layers of dinosaur tracks, as well as invertebrate traces, body fossils, stromatolites, plants, and more. The City of St. George hired Andrew R.C. Milner to document and preserve the site, along with help from a dedicated group of volunteers, the Utah Friends of Paleontology, over the next few years. And working with the City of St. George, the Johnsons donated the land to preserve the site, and a museum was built over the bulk of the tracksite in 2005, still in its original location on the Johnson property.

Sixteen years since the initial discovery, the SGDS is operating better than ever, with over 38,000 visitors per year, according to Liz Freedman-Fowler, the Executive Director of the SGDS. The museum is now autonomous and is managed by the non-profit Dinosaur Ah!Torium Foundation. Andrew R.C. Milner continues to research, curate, and preserve the tracksite and associated fossils as the the Site Paleontologist and Curator. And the Utah Friends of Paleontology continue to support the site the site, with 37 active volunteers who have provided over 6600 volunteer hours per year.

The museum has undergone many changes in the past eleven years. When I worked there from 2006–2008, the in situ tracksite was difficult for visitors to view; the sandstone, as resilient as sandstone can be, was still very delicate after being exposed, and thus patrons were not allowed to walk out onto the surface. However, in the years since, the SGDS has blocked out large windows, built a brand-new raised wooden platform over the tracksite, and provided proper illumination to make the dinosaur tracks and other traces visible to every visitor.

The brand new raised walkway over the track surface allows visitors to view the tracks in place. Image by Sarah Gibson.
Eubrontes track on display. Image by Sarah Gibson.

So, what will you see when you visit the SGDS? Yes, you will see dinosaur tracks, but this site offers so much more than just tracks. This site represents a 200 million year old snapshot of a ecosystem: an ancient shoreline of a large lake that, during the Early Jurassic, was surrounded by vast desert and dunes. Dinosaurs, early crocodylimorphs, fishes, all came here to drink and thrive. Thus far, the trace fossils have been identified to several ichnogenera: Eubrontes, Grallator, Anomoepus, Kayentapus, and Batrachopus, to name a few examples. By far, Grallator-type tracks are the most abundant, made by a small theropod dinosaur, possibly Megapnosaurus. Larger Eubrontestracks are also prominent, made by a larger theropod, such as Dilophosaurus. Eubrontes tracks are also represented by some of the most well-preserved natural casts at the site, allowing you to see details down to the claws and toe pads.

The tracks can tell us so much about the behavior of organisms: speed has been calculated on several of the trackways, as well as the size of the the organisms. One particular trackway told us a lot about theropod stance, posture, and behavior. The trackway was discussed and published in PLOS ONE in 2009, by Andrew R.C. Milner et al. The trackway preserves a moment where, a theropod dinosaur crouched in the mud as it emerged from the water of the lake, scooted forward a bit (creating two overlapping crouching impressions). The impression of the ischia is visible, as is the tail mark behind the dinosaur. In addition, the “heels” are well-preserved, telling us that this animal crouched in a manner similar to birds. Hand impressions are also visible, showing that the palms of the animal faced inwards.

The crouching dinosaur trace, one of only six in the world.
The crouching dinosaur trace, one of only six in the world. Image by Sarah Gibson.

We can follow the path of this dinosaur as it stood up from crouching in the mud, and began walking across the surface. A beautifully reconstructed Dilophosaurus model is visible in the end of the trackway as it is preserved, allowing visitors to imagine the dinosaur itself, walking out of the lake and through the mud.

A reconstruction of Dilophosaurus, placed in the trackway of the crouching dinosaur. Image by Sarah Gibson.

With the renovations to the museum, this spectacular crouching trace and subsequent trackway, along with thousands of other tracks and traces, are now easily visible to every visitor of the site, along with hundreds of blocks showcasing some of the SGDS’s finest tracks. Mud cracks, ripple marks, swim tracks, skin impressions, are all visible to the naked eye.

Can dinosaur tracks be cute? Image by Sarah Gibson.

The site also boasts body fossils, with isolated dinosaur teeth and a vertebra recovered, as well as fossilized remains of sharks and ray-finned fishes, including some articulated fishes likely belonging to the genus Lophionotus (whom yours truly described). In the nearby area, coelacanth and lungfish remains have also been discovered. Numerous plants have also been found at SGDS.

The largest single block of tracks at the tracksite, featuring several distinguishable Grallator trackways, possibly made by Megapnosaurus. Image by Sarah Gibson.

Overall, it’s pretty hard to find a better moment in time of an ecosystem preserved, and it really is thanks to the Johnsons, who had the foresight to preserve and protect the fossils for future generations. And with the beautiful preservation  of the tracksite, protected within the SGDS museum, this site will continue to provide evidence of a time 200 million years ago, when some thirsty dinosaurs found some solace in a lake among the desert. Its a spectacular locality well worth your time and patronage. If you are interested in more information, Jerry Harris, paleontologist and professor at Dixie State University in St. George, along with Andrew R.C. Milner, have recently published a book chronicling the science and history of the site. See the links below for information!

Restoration of Early Jurassic environment preserved at the SGDS, with the theropod Dilophosaurus wetherilli in bird-like resting pose, demonstrating the manufacture of SGDS.18.T1 resting trace. By Heather Kyoht Luterman.
Restoration of Early Jurassic environment preserved at the SGDS, with the theropod Dilophosaurus in bird-like resting pose. By Heather Kyoht Luterman. From Milner et al. (2009).

And happy tracking!

Read more:
Harris JD, Milner ARC (2015) Tracks in Deep Time: The St. George Dinosaur Discovery Site at Johnson Farm. University of Utah Press.

Milner ARC, Harris JD, Lockley MG, Kirkland JI, Matthews NA (2009) Bird-Like Anatomy, Posture, and Behavior Revealed by an Early Jurassic Theropod Dinosaur Resting Trace. PLoS ONE 4(3): e4591. doi:10.1371/journal.pone.0004591

It’s a Hard-Knock Life for an Ichthyosaur | PLOS Paleo Community

Bone is a fascinating thing. It holds our bodies up, supports our organs, allows us to move, gesture, and talk, and even provides our muscles with the necessary calcium and phosphate to function and obtain energy. But bones can be brittle; they can’t withstand everything we throw at them (sometimes literally), and they can break. For anyone, like me, who has broken a bone or two (or five!), we count ourselves lucky that bones can also heal themselves. And this is not just through the miracles of modern medicine; bone has the capacity to repair itself, and has done so for millions of years.

We know this because we see the evidence written all over dozens and dozens of fossils. Sue the T. rexis a quintessential example, with numerous broken and subsequently healed ribs, vertebrae, and limbs, as well as evidence of infection and disease. Paleontologists love examples like Sue, because they illuminate things we can’t otherwise see in the fossil record (outside of trace fossils)—they give us evidence of a life lived. Pathologies can tell us about competition among organisms, they can tell us who was prey (or a predator), and ultimately they tell us who survived a traumatic event and lived to tell the tale through their bones. It’s like showing off your scars and bragging about the crazy events in your life, but through the fossil record instead.

I’ve talked about paleopathology on the blog before (looking at you, Dilophosaurus!), and now I want to highlight a new study published last week in PLOS ONE, by authors Judith M. Pardo-Pérez, Benjamin P. Kear, Heinrich Mallison, Marcelo Gómez, Manuel Moroni, and Erin E. Maxwell. Their study focuses on a more understudied group, when it comes to paleopathology—ichthyosaurs.

Temnodontosaurus sp. (UMH). Posidonienschiefer Formation, middle Toarcian. a. Skull in right lateral view indicating the pathological areas of the lower jaw illustrated in b-e. b. Concavities observed at the ventrolateral margin of the dentary and surangular. c. Bony overgrowth at the anterior end of the right angular. d. Tissue remodeling observed at the dorsal margin of the angular. e. Fibre remodeling on the lateral surface of the dentary, dorsal to the concavity. From Pardo-Pérez et al. (2018), CC-BY.

Speficially, Pardo-Pérez et al (2018) examined 39 specimens of Temnodontosaurus, an Early Jurassic ichthyosaur from southern Germany. The goal of this study was to provide an atlas of pathological evidence in large ichthyosaurs that can be used and translated across other taxa.

The study is thorough, even going through specific examples that are not pathologies; for example, some broken bones do not show evidence of healing; the authors contribute these to post-mortem taphonomic processes such as scavenging, erosion, compression, etc.

However, the key evidence of pathological bone modification is fiber remodeling or callus development; clear evidence that the organism survived the traumatic event and healed.

Healing process of bone. From Pardo-Pérez et al. (2018). CC-BY.

Of the 39 specimens the team examined in collections throughout Germany, 21% showed osteological pathologies. Some individuals contained multiple pathologies within different regions of the body. When breaking down the anatomical placement of pathologies among specimens included in this study, 23% were found in the skull region, followed by dorsal ribs (21%) and pectoral girdle and forefins (11%). Most of the pathologies observed are attributable to simple trauma with evidence of healing, rather than infectious or articular disease.

This study highlighted a reporting bias in previous studies of Temnodontosaurus. Previous studies have mostly noted only broken ribs, whereas according to Pardo-Pérez et al (2018), pathologies are present throughout the body and skull.

Temnodontosaurus nuertingensis (SMNS 13488). Numismalismergel Formation (lower Pliensbachian). a. Skull in dorsal view indicating the pathologies in the premaxilla in b, c and d. b. Right premaxilla showing two areas of fibre remodeling (inset: magnified view). c. Lateral surface of the right premaxilla indicating five small areas of fibre remodeling. d. Dorsal view of the right and left premaxillae, indicating areas with fibre remodeling. e. Skull in left lateral view indicating pathological areas on the left premaxilla (f) and left dentary (g). f. Three small areas with fibre remodeling on the left premaxilla. g. Fibre remodeling on the ventrolateral margin of the left premaxilla and the lateral surface of the left dentary. h. Skull in ventral view, showing the location of the pathologies illustrated in i-n. i. A posteroventral to anterodorsally oriented concavity in the right angular. The arrows indicate slight fibre remodeling at the ends. j. A rugose protuberance with fibre remodeling on the right splenial. k. Pathological area between the left angular and surangular demarcated by dotted lines. l. A small area with callus development on the left angular. m. Three small protuberances with fibre remodeling on the lateral margin of the left angular. n. A teardrop concavity between the left angular and left surangular with fibre remodeling at its dorsal and ventral corners. From Pardo-Pérez et al. (2018), CC-BY.


Pardo-Pérez et al. (2018) gives insight into what might have caused the pathologies observed in Temnodontosaurus. For example, one specimen, UM-O no. 4 shows some evidence of bone trauma and healing in the premaxilla and dentary, something that has been observed in other marine animals, such as the plesiosaur Pliosaurus. The authors suggest that a misalignment of the upper and lower jaws could have caused some occlusal stress that lead to this injury. Another specimen, UM-O no. 14, shows a similar pathology but with evidence of infection, leading the authors to believe that this ichthyosaur may have suffered from an abscess.

Other specimens, however, indicate that they may have been victim to an attempted attack. One specimen (SMNH 15950) shows ten circular areas separated by a few centimeters on its snout, clearly indicating that another large marine reptile, possibly another ichthyosaur or a crocodylomorph like Steneosaurus, attempted to take a bite out of this fella.

But what about the fractured ribs? Well, Pardo-Pérez et al. (2018) suggests several possible explanations. Obviously, one could assume that ichthyosaurs might have aggressive confrontations with other ichthyosaurs for a number of reasons—mating, niche competition, territory, etc. But other, less considered, options have been suggested by other studies. It could be possible that the ichthyosaur breached itself on a reef, or collided with a reef or rock. It’s also been suggested by previous studies that changes in atmospheric pressure as the ichthyosaur dove deep into the sea could lead to broken ribs. However, Pardo-Pérez et al. (2018) reject this last idea, noting that the lack of physiological evidence (avascular necrosis) suggests that these ichthyosaurs were not partaking in any abyssal adventures.

What is confirmed to be low in number are pathologies attributable to joint disease, which are more common in other aquatic organisms, particularly in the vertebral column. Plesiosaurs, mosasaurs, and even cetaceans all indicate a higher rate of infections in the vertebral column compared to ichthyosaurs like Temnodontosaurus. The difference in distributions of this type of pathology may have other implications with regard to types of movement among these animals. Likewise, avascular necrosis, a type of pathology that would indicate these organisms were moving into deeper depths, are also absent in this study. The authors note only one example of avascular necrosis that was reported in a specimen of Temnodontosaurus from England, so if this is truly the case, the geographic differences may indicate preservational differences, or more significantly may indicate different lifestyles in geographically distinct populations of Temnodontosaurus.

Whatever the case, ichthyosaurs had their own shares of battles in the Jurassic seas, and thankfully, we have their bones that bear the scars and tell the tales.

Reference: Pardo-Pérez JM, Kear BP, Mallison H, Gómez M, Moroni M, Maxwell EE (2018) Pathological survey on Temnodontosaurus from the Early Jurassic of southern Germany. PLoS ONE 13(10): e0204951.

Featured image: Temnodontosaurus trigonodon. (GPIT/RE/1491/13), Complete skeleton in dorsal (skull) and ventral view (postcranium). From Pard0-Pérez et al. (2018), CC-BY.

This post was original posted on the PLOS Paleontology Community website and is being archived here by the author. You can read the original post here.

Munching and Migrating Megabeasts: Sauropod teeth illuminate migration patterns between Europe and Africa

When someone studies migration patterns of different organisms, one may consider many lines of evidence. For modern organisms, that is easy: visual and audio cues, tracks, feces, etc. In the fossil record, it can be a bit trickier to establish what may be a possible migration behavior in a landscape and habitat that is much different today, with a limited set of data preserved in the fossil record. The best a paleontologist can hope for is some kind of pattern or link that unites fauna across different spatial zones.

recent study published in PeerJ has found one such line of evidence for a charismatic group of organisms: Cretaceous sauropods. The study, lead by Femke Holwerda from the Faculty of Geosciences at Utrecht University in The Netherlands, has provided possible evidence for faunal connections through an unlikely source of information—their teeth. I asked Femke a few questions relating to this exciting study.

How did this study come about?

I was supervising a bachelors student from Utrecht University while he undertook a short research project in the collections of the Palaeontological Museum of Munich, Germany, on a sauropod tooth sample from the Kem Kem beds, Morocco. Verónica Díez Díaz [co-author of the study] and I decided to expand on these results, using an additional tooth sample from the same beds from the Palaeontological Museum in Zurich, Switzerland. Verónica realized the tooth sample morphologically matched some Cretaceous tooth morphotypes of Spain and France from her previous research. Finally, we got a colleague from Munich, Alejandro Blanco, on board to help with the statistical analysis. So the project has been quite an international one, with Spanish and Dutch researchers working on material from German and Swiss collections!

It seems like sauropod material should be fairly conspicuous (i.e., large and obvious!), but your paper points out that the sauropod material preserved in this region is almost exclusively teeth. Why aren’t large sauropod bones recovered in these regions? Why just teeth?

We are not entirely sure why there are so many more theropod skeletal remains from this area, and relatively few sauropod ones. As the major herbivorous components of most Mesozoic vertebrate ecosystems, you’d expect many more sauropods! One explanation is that the arid, riverine ecosystem of the Cretaceous of Northwest Africa supported a food web consisting of many predators and not so many herbivores (Läng et al., 2013). Still, sauropods were around, as their teeth got preserved. The handy thing about sauropod teeth is that they are relatively abundant in the fossil record, as sauropods shed their teeth continuously (unlike us humans, for example, who only shed teeth once in our lives). These teeth are covered in enamel, a hard substance which survives fossilization pretty well, and therefore can be used in species diversity studies.

You suggest that this region of study represents migratory routes for sauropods, but the deposits suggest and area somewhat devoid of vegetation. What would the environment have been like for these large animals? How would they have survived?

Our idea is that these large sauropods were able to migrate distances, which were quite far, in order to get enough food in. Sauropods were massive feeding machines and would have needed quite a bit of plant food, and perhaps they had to travel a distance to get enough sustenance in an arid region. A previous study (Fricke et al., 2011) demonstrates this for Jurassic sauropods, and we see no reason that these Cretaceous ones couldn’t do the same. Besides, the Mediterranean area in the Cretaceous was far more of a shallow sea with sand banks, which would provide coastal routes from one continent to the other. Europe was also a collection of island back then, and still similar sauropods have been found across, for example, Spain and France (Díez Díaz et al., 2018).

 Images of various sauropod teeth in apical view, basal view, labial view, lingual view, distal view, and mesial view. The scale bar equals 1 cm. Images taken by FH. From Holwerda et al. (2018). CC-BY.

You are able to compare morphological similarity of teeth to various genera of sauropods. How would you say your study possibly changes or improves what we know regarding sauropod diversity and geographical distribution?

Several previous studies (e.g. Dal Sasso et al., 2016; Díez Díaz et al., 2018; Sallam et al., 2018) showed skeletal morphological similarities between North African and Southern European vertebrates, amongst others crocodylomorphs, theropods, sauropods and other smaller vertebrates. However, to our knowledge, no larger sauropod tooth morphological study has been done. We think this study confirms and builds upon the theory of faunal connections and possible landbridges between North Africa and Southern Europe.

Were there any surprises in your study?

I think this research started out as a small morphological study; but neither of us could anticipate that it would become a far broader study into possible migration routes, faunal connections or even landbridges! This was definitely very exciting to dig into, and to build on previous research on this (see for instance Csiki-Sava et al., 2015; Rabi 2015).

 Examples of enamel wrinkling. From Holwerda et al. (2018). CC-BY.

Can you explain the importance of enamel wrinkling? Does it have any functional significance?

Heavy wrinkling on enamel surface seems to be a special development for herbivory, although it is found not just in sauropods, but also in ornithopods (Chen et al., 2018) for instance. The specific functional significance is not entirely understood, but probably it has to do with the mechanical endurance of the enamel for heavy use (i.e., not munching on tender pieces of meat, but on heavy fiberous plants and stalks). As sauropods did not chew their food, but rather used a grip-and-pull motion to shear off vegetation, their teeth had to be pretty tough! In sauropods, so far, it seems that enamel wrinkling is species specific, and thus very useful in diversity studies (see e.g. Holwerda et al., 2015; Carballido et al., 2017).

You mention that some of this material is scarce. Any intention to follow up with more collections-based research or fieldwork to increase sample size?

Yes, definitely! It seems these type of sauropod teeth are quite common in collections, as they are usually found in batches and then distributed from Morocco to museums all over the world. We are expecting to follow up on this study, and perhaps go into an in-depth morphological study on Cretaceous sauropod teeth, perhaps using geometric morphometrics to better quantify similarities and differences in tooth shapes better. Stay tuned for this!

What is your favorite part of your research on sauropods?

Sauropods are the largest vertebrates to ever have walked the earth. No terrestrial animal ever got that big again. This is fascinating to us, because it’s still not entirely clear how they could get so big! Also, they were immensely successful; we find their remains in every continent throughout the Mesozoic. There is still plenty left to learn about them, which is why they are my favorite type of dinosaur.

Anything else you’d like to share?

This is only the tip of the iceberg! Several studies are currently being developed; redescribing and analyzing the Cretaceous sauropod faunas from Africa and Europe from a systematic and palaeobiogeographic point of view. So, in the next few years, we probably will have more information about the migratory patterns of this huge animals.

Thanks, Femke and colleagues for this great work! Find the paper online at PeerJ.


Carballido JL, Holwerda FM, Pol D, Rauhut OW. 2017An Early Jurassic sauropod tooth from Patagonia (Cañadón Asfalto Formation): implications for sauropod diversityPublicación Electrónica de la Asociación Paleontológica Argentina 17:50-57

Chen, J., LeBlanc, ARH, Jin, L., Huang, T, Reisz, RR. 2018. Tooth development, histology, and enamel microstructure in Changchunsaurus parvus: Implications for dental evolution in ornithopod dinosaursPLoS ONE 13(11):e0205206

Csiki-Sava Z, Buffetaut E, Ősi A, Pereda-Suberbiola X, Brusatte SL. 2015Island life in the Cretaceous – faunal composition, biogeography, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelagoZooKeys 469:1-161

Dal Sasso C, Pierangelini G, Famiani F, Cau A, Nicosia U. 2016First sauropod bones from Italy offer new insights on the radiation of Titanosauria between Africa and EuropeCretaceous Research 64:88-109

Díez Díaz V, Garcia G, Pereda Suberbiola X, Jentgen B, Stein K, Godefroit P,Valentin X. 2018The ttitanosaurian dinosaur Atsinganosaurus velauciensis (Sauropoda) from the Upper Cretaceous of southern France: new material. Phylogenetic affinities, and palaeobiogeographical implicationsCretaceous Research 91:429-456

Fricke HC, Hencecroth J, Hoerner ME. 2011Lowland-upland migration of sauropod dinosaurs during the Late Jurassic epochNature 480:513-515

Holwerda FM, Pol D, Rauhut OWM. 2015Using dental enamel wrinkling to define sauropod tooth morphotypes from the Cañadón Asfalto Formation, Patagonia, ArgentinaPLOS ONE 10:e011810

Holwerda FM, Díez Díaz V, Blanco A, Montie R, Reumer JWF. 2018 Late Cretaceous sauropod tooth morphotypes may provide supporting evidence for faunal connections between North Africa and Southern EuropePeerJ6:e5925

LängEBoudadLMaioLSamankassouETabouelleJTongHCavinL. 2013.Unbalanced food web in a Late Cretaceous dinosaur assemblagePalaeogeography, Palaeoclimatology, Palaeoecology 381–382:26-32

Rabi M, Sebök N. 2015A revised Eurogondwana model: Late Cretaceous notosuchian crocodyliforms and other vertebrate taxa suggest the retention of episodic faunal links between Europe and Gondwana during most of the Cretaceous.Gondwana Research 28:1197-1211

Sallam HM, Gorscak E, O’Connor PM, El-Dawoudi IA, El-Sayed S, Saber S, KoraMA, Sertich JJ, Seiffert ER, Lamanna MC. 2018New Egyptian sauropod reveals Late Cretaceous dinosaur dispersal between Europe and AfricaNature Ecology & Evolution 2:445-451

This post was originally published on the PLOS Paleontology Community website, and is being archived here by the author. You can view the original post here.

Pregnant Plesiosaurs and Baby Bones: Bone histology reveals ontogeny in polycotylid plesiosaurs — PLOS Paleo Community

Pregnancy in the fossil record is an exciting find. Setting aside the sad fact that an unfortunate mother met her demise while carrying a baby, these one in a million specimens provides some key insight into the behavior and lifestyle of organisms unlike any living today.

One such specimen is on display at the Natural History Museum of Los Angeles County. It reveals that a species of plesiosaur, Polycotylus latipinnus, was in fact pregnant when it died, revealing information about reproduction and birth in these marine reptiles. But a new study is looking closer at this specimen, in part to to confirm this miracle mother and its baby, but also to address further questions and hypotheses about maternity in marine reptiles.

According to the study, published in the journal Integrative and Comparative Biology by co-authors Dr. Robin O’Keefe, research associate of the Natural History Museum of Los Angeles County and professor at Marshall University; Martin Sander, professor at Bonn University in Germany; Tanja Wintrich, Ph.D. candidate at Bonn University; and Sarah Werning, assistant professor at Des Moines University, new evidence obtained via bone histology supports the hypothesis that plesiosaurs gave birth to live young, and that these young animals went through rapid growth that might have hindered their swimming performance.

According to O’Keefe, “Our study…reaches the novel conclusion that plesiosaur fetal bone grew extremely quickly, sacrificing bone strength for growth rate. Plesiosaur babes may have needed maternal care for protection.”

And these babies weren’t just growing quickly, they were already born large! The data obtained in this study shows that at least some plesiosaurs gave birth to live young that were about 40% the length of the mother, the equivalent of a human mother birthing a six-year old.

Co-author Tanja Wintrich takes research samples from the pregnant plesiosaur on display at the Natural History Museum of Los Angeles County. Image Courtesy NHMLA.

The team sampled the Pregnant Plesiosaur by drilling directly into the specimen on display and obtaining samples suitable for a histological analysis. These were compared it to histological samples of juvenile specimens of closely-related plesiosaur, Dolichorhynchops bonneri, to illustrate possible ontogenetic changes in plesiosaurs and gain a bigger understanding of bone development in this marine reptiles.

I had a chance to ask lead author Robin O’Keefe some questions related to the paper, and he provided some great additional insight into this exciting research!

PPC: First of all, tell me a little bit of the background on this paper. Who first suggested that the LACM specimen was pregnant, and who thought of utilizing histological methods?

FRO: Because the LACM mother is so complete, and because most of the fetus is there, it was obvious when the specimen was collected in the 1980s that it might be mother and child. It is a spectacular fossil. But preparation was never finished and no paper written until Luis Chiappe decided to include the specimen in the then-new displays at the Natural History Museum in L.A. Luis brought me in to advise on the mount and to write up the fossil (O’Keefe and Chiappe, 2011); that paper received a lot of attention. But there was a little backlash at the time; people made a valid point that the fossil was a single occurrence and so could be some random event.

Good science is repeatable, and makes predictions, and this got me thinking: how could the notion that plesiosaurs gave birth to large, live young be tested? I discussed this at SVP with Hans Larsson, and he suggested looking for birth lines and other histological evidence for ontogeny. The LACM fetus would not have a birth line, but other juveniles might. So I identified a good growth series from a single species and made sections. Meanwhile, my colleagues Sander and Wintrich sampled the histology of the LACM specimen. We we able to use these data from the fetus to make predictions about the other material. And everything checks out: our young juvenile has a clear birth line and is about 40% of maternal size. It is great in science when you come at a question from another direction and get the same answer. It gives you confidence in your findings.

Why are young polycotylid fetuses so large? 40% of the maternal length seems massive, wouldn’t that be more of a danger to the mother when birthing?

As to why plesiosaurs in general, and polycotylids in particular, had such large babies is a difficult inference. The evolutionary tradeoff between making many cheap offspring vs. a single expensive offspring is complex and has different drivers in different species. It probably had something to do with how dangerous the ocean was (and is); most whales and other marine mammals have single progeny, while that is not the case with all terrestrial mammals. That’s a suspect comparison because mammals are so different physiologically, but we know from analogy with other reptiles that have large, single young that they tend to have maternal care. As to the size of the fetus being a danger to the mother, that is less of a concern than it might seem. The Solomon Islands skink, a lizard, can have single progeny that are over half the length of the mother when born. It sounds nuts, but they pull it off. Also, the hip bones in plesiosaurs are reduced because they are aquatic. So there was plenty of room for the baby to make it out. Humans are actually quite unusual in that birth is so constricted; because we are bipedal, there is a great evolutionary pressure for the hips to be close together, while at the same time there is great evolutionary pressure for increased head size. Birth is much more dangerous in humans than most other animals; in a quadrapedial animal the hips can get wider to accommodate larger offspring.

You reference Kastschenko’s Line frequently in the study. What is that?

Kastschenko’s Line is a histological feature that delineates the two zones of ossification in a developing limb bone. The bone begins as a cartilaginous precursor that then ossifies; at the same time this is happening, additional layers of bone are being deposited around the ossifying cartilage. So you have a cortex deposited around a medulla, and Kastschenko’s Line is the boundary between the two. The cortex is deposited from this line outward, giving a record of bone deposition over ontogeny.

As you mention in the study, the propodials of the LACM fetus are not preserved, and so you used the scapula as a proxy. Is there any concern that the histology of the scapula of the specimen might be misleading regarding the histology of the distal portion of the flipper?

There is some concern. It is a valid criticism. I would be more concerned if the histology was vastly different from a limb bone; however, it is very similar, with identical bone types. Also the scapula is still a limb bone and has the same development pattern as a humerus or femur. This is not true of vertebrae or ribs and I would not make that comparison.

The microstructure of a newborn plesiosaur bone in polarized light. Differences in color show differences in bone fiber direction, deposited rapidly around canals for blood vessels. The small black dots are individual bone cells.

What did you find surprising or most interesting in this study?

The histology indicates that the fetus grew extremely rapidly in utero. I think that is very interesting; where did the energy come from? The high growth rate probably required a high body temperature, and possibly full warm-bloodedness, to support it. This is in accord with isotopic data that suggest that plesiosaurs were warm-blooded. So I think we we are really starting to flesh out a picture of plesiosaurs as active, warm-blooded animals that lived in social groups and cared for their young. A good modern analog would possibly be an orca.

How applicable/accessible are histological methods to other researchers?

Very. Paleohistology is really exploding right now, and its methods are being applied across all vertebrate clades. The insight it can give us about growth biology in extinct animals is unprecedented. We have a long way to go, this research in plesiosaurs is just beginning, and we don’t understand as much as we would like about growth in plesiosaurs in general.

It is interesting that so much info regarding aquatic locomotion can be elucidated histologically. Have you learned anything else about these specimens by examining histological data?

We are learning it right now. There is a lot of histological variability among plesiosaur clades, and patterns might be linked to lifestyle, phylogeny, or both. I am working on a bunch of elasmosaur data right now and they look like they are doing something different; stay tuned for more.

Where does this project go from here? Do you have more plans to sample similar specimens?

See above; we’ve got to document the similarities and differences among plesiosaur clades to understand how their life cycles varied.

Anything else you’d like to share to the PLOS Paleo Community?Thanks!!

Thank you Robin!


O’Keefe FR, Chiappe LM. 2011. Viviparity and K-selected life history in a Mesozoic marine plesiosaur (Reptilia, Sauropterygia). Science 333:870–3.

O’Keefe FR, Sander PM, Wintrich T, Werning S. 2019. Ontogeny of Polycotylid Long Bone Microanatomy and Histology. Integrative Organismal Biology 1(1):oby007.

Featured Image: Visitors to the Natural History Museum can see the pregnant plesiosaur on display in the Dinosaur Hall. The specimen is 15.5 feet wide and 8 feet tall. It is the only pregnant plesiosaur fossil ever discovered. Image courtesy NHMLA.

This post was originally posted on the PLOS Paleontology Community Website on January 17, 2019 and is being archived by the author here. You can find the original post here.

Stepping Out: New Ornithomimosaur from Arkansas Described | PLOS Paleo Community

This is a blog post I recently wrote for the PLOS Paleontology Community Blog. I am archiving it on my personal website. You can access the original article here.

Enter Holotype cast of Arkansaurus fridayi, pictured in front of the Broadway Bridge, Little Rock, Arkansas. Image courtesy R. Hunt-Foster, used with permission.a caption

Last week, a new species of dinosaur was described in the Journal of Vertebrate Paleontology. The dinosaur, Arkansaurus fridayi, is an ornithomimosaur the Early Cretaceous of Arkansas, and represents the first dinosaur to be described from that state. In fact, it’s now be honored as the State Dinosaur of Arkansas.And although the paper itself is not Open Access, the data is Open Access and can be found online at MorphoSource!

The specimen of Arkansaurus was discovered over four decades ago, and I sensed an interesting story behind this discovery. So I asked lead author ReBecca Hunt-Foster, a paleontologist for the Bureau of Land Management, a few questions regarding this dinosaur decades in the making.

The specimen was discovered quite a while ago! I’m guessing there’s a unique story behind the journey of this specimen, would you care to elaborate?

The fossils were discovered in 1972 by Mr. Joe B. Friday on his land near Locksburg, Arkansas, following an earthmoving project. Mr. Friday showed the fossils to Doy Zachary, then a student at the University of Arkansas (and now geology professor emeritus at the University of Arkansas), who then showed them to Dr. James Quinn [posthumous second author]. Mr. Friday donated the fossils to the University of Arkansas, and the fossils are named also in his honor and in honor of the state in which they were discovered – “Arkansaurus fridayi”, a name first unofficially proposed by Quinn.

In 1973, the remains were initially described by Quinn at the South-Central Section meeting of the Geological Society of America in Little Rock, Arkansas. Dr. Quinn’s tragic and untimely death in 1977 left the fossils without an official scientific description. The fossils waited in the collections at the University of Arkansas museum until I first began working on the project as an undergraduate in the geology department at the University of Arkansas in 2002. Forty-five years after Quinn began his research, I gave a presentation on the remains at the recent 2018 South-Central Geological Society of America meeting in Little Rock.

Hunt-Foster working on the specimen, circa 2003. Image courtesy R. Hunt-Foster, used with permission.

When I first began my work in the early 2000’s there was little in the way of published research for me to compare the Arkansaurus specimen too. I completed my initial research in 2003, and came back to the project in 2016, when I reexamined the fossils and was able to compare them the additional new fossils that had been described in the scientific literature. This allowed me to do a more complete description of the remains. The fossilized remains were also recognized by the State of Arkansas in 2017 as the official State Dinosaur of Arkansas.

The specimen was found on Mr. Friday’s private land, and you’ve honored him with the specific epithet fridayi. Was there an effort to find any other material in the area or in the same formation elsewhere? Were any other fossils from other organisms found alongside this specimen?

Around 2002 I visited Mr. Friday with my mentor, Dr. Leo Carson Davis, and he took us to the site where the fossils were discovered. Mr. Friday had searched since the initial discovery for additional bones. Only weathered and rounded fragments had been discovered, and were given to me in 2002 to work with, although no additional data was gained from them. No other fossils were recovered from the original discovery site itself.

Arkansaurus, along withNedcolbertia, now represent some of the oldest remains of ornithomimosaurs in North America. How is this discovery changing our global understanding of the biogeography and evolutionary history of ornithomimosaurs?

Paleontologists have recently found other animals, such as the sauropod dinosaur Mierasaurus, that lived alongside Nedcolbertia, in the Cedar Mountain Formation of Eastern Utah. These dinosaurs have ancestors that suggest they originated in Europe, rather than from the North American Jurassic sauropod lineages, and immigrated to North America across a European land bridge during a time of lower sea levels during the Early Cretaceous, as the two continents began to move away from one another. It is reasonable to hypothesize that North American ornithomimids also immigrated during this time, and spread across North America during this time. There were no large geographical boundaries to keep them from moving back and forth, and the Skull Creek Seaway had not yet descended entirely from the north, which later bisects the continent into Laramidia to the west and Appalachia to the east. Arkansaurus helps us fill in the ornithomimid family tree, especially in North America, as most of the specimens known from North America are only known from the Late Cretaceous. I am also currently studying ornithomimosaur specimens collected from the Arundel Clay of Maryland and the Cloverly Formation of Wyoming, which are also Early Cretaceous in age, to compare to Arkansaurus and Nedcolbertia, and we presented our early findings at the Society of Vertebrate Paleontology meeting in 2017.

Ornithomimid fossils are often usually identifiable by their necks and heads, and aren’t often recognized by their feet. What is it about this specimen that gave it away as an orninthomimid?

I started with the metatarsals. I first started by comparing them to other known forms from North America, including Nedcolbertia and Ornithomimus velox. From there I continued to look into the published descriptions of other known ornithomimosaurs, and was surprised at the volume of material that has been published since 2003, as well as the variety and inconstancies seen in the metatarsals across geologic time. Some of these inconsistencies might become more clear as geologic dating methods are improved, when additional and more complete specimens are discovered,  and when existing undescribed specimens are published on (there are quite a few from the Early Cretaceous globally we are still waiting on!). The metatarsals I found to be the more diagnostic elements, and are more similar to what we see in the Arundel Clay material and in Nedcolbertia, than to any other ornithomimosaurs.

Let’s talk artwork. You commissioned Brian Engh for the fantastic reconstructions ofArkansaurus, and we’ve featured Brian here at PLOS Paleo beforeHow did you guide him towards the look of the animal, as well as its environment?

Reconstruction of Arkansaurus in its natural habitat. Artwork by Brian Engh, used with permission.

I love working with Brian! He puts a TON of research into his pieces, and ask amazing questions, which I really appreciate. I gave Brian information on similar ornithomimosaurs, and some information on soft tissue has been published, so there was at least some information to help him get started. After that, I let Brian do what he does—a ton of additional research as well as observing modern animals—and then we work to tweak any of the fine features. You can check out more about his art process for the Arkansaurus pieces here:

Arkansaurus is named after the state of Arkansas, where this dinosaur was discovered. But Arkansas isn’t usually renown for their dinosaur discoveries, making this a pretty special find! Do you have plans to further explore this area for more dinosaur or other fossil material?
Yes! I am working with Celina Suarez, Joseph Fredrickson, Rich Cifelli, Jeff Pittman, Kristy Morgan, Mason Frucci and Randy Nydam to study some fossils that were discovered from a different site in the Trinity Formation within the same county by Jeff Pittman in the 1990s. These remains include theropod, sauropod and ankylosaur dinosaurs, along with crocodiles, turtles, a lizard, a mammal and a bird. Celina and I have plans to revisit this discovery site, and hopefully a few other exposures to search for additional material.
Anything else you’d like to share?
Dinosaur fossils are so rare from Arkansas, and other surrounding states like Louisiana, Oklahoma and Alabama, that it is really great when we are contacted by local members of the community who may have potentially discovered fossils. There is often the misconception that people are not allowed to have these remains or that they will be “taken away” from them. This is not true. As long as the remains were collected legally from your private land, you have the right to collect and keep these fossils. Due to the rarity of these types of fossils, it is wonderful when people reach out to us, and ask us to identify fossils for them, donate them so they can be studied, or can help us locate additional remains. The public really are our eyes on the ground, and paleontologists can not visit every outcrop. In our case with Arkansaurus, Mr. Friday was kind enough to donate the specimens to the University of Arkansas, where they have been carefully stored and are available for paleontologists to study. I was happy that we could officially name these remains in his honor, and I am forever indebted to the Friday family for their important contribution to paleontology!






R. Hunt-Foster with the holotype of Arkansaurus. Image

Thank you, ReBecca, for sharing your insight on this discovery! Welcome, Arkansaurus!

Reference:Hunt RK and Quinn JH (2018) A new ornithomimosaur from the Lower Cretaceous Trinity Group of Arkansas, Journal of Vertebrate Paleontology, DOI: 10.1080/02724634.2017.1421209

Shell Shock! Can morphometrics distinguish fossil turtle species? | PLOS Paleo Community

This is an article I wrote for the PLOS Paleontology Community blog on March 8, 2018. I am archiving it here on my personal website. View the original post here.

A big component of paleontological work revolves around identifying morphological characters that diagnose distinct species in the fossil record. But therein lies an unavoidable problem: where is the line between variation among separate species and variation within a species? With modern taxa, this problem can be addressed using other lines of evidence: dimorphism can be solved by observing morphological trends between males and females; morphological differences due to age and maturity can be addressed by examining development; or if dealing with potential subspecies or cryptic species, genetics and genomics can help delineate intraspecific variation.

But what about when we are dealing with fossils? Fossil taxa represent just a snapshot of the possible biodiversity that existed in their respective ancient ecosystems, and fossil detectives are left examining what few clues we have in order to deduce the bigger picture. We often can’t tell from the fossil whether the organism represented a male or a female, a juvenile or an adult, etc. So the million dollar question is, when we think we have a new species, do we really have a new species? Or are the differences in size and shape that we have observed due to sexual dimorphism, age and maturity, or just simply variance in a population?

A new paper was published yesterday in PLOS ONE, by Natasha Vitek, a PhD candidate at the University of Florida. Vitek’s research focuses on Eastern Box Turtles, and her aim is to address some of the concerns that I mentioned above, using shell morphology of extant and extinct Eastern Box Turtles, Terrapene carolina, as an example to test variation within species, with the hopes that guidelines for diagnosing new species can become even clearer.

Modern-day representatives of T. carolina display a lot of variation among individuals within the species. These turtles are a terrestrial North American taxon with a historically widespread distribution. In order to effectively demonstrate the intraspecific variation, most biologists that work on them have separated T. carolina into several subspecies, usually parsed out over geographical ranges with some intergrades. (Subspecies come with their own bag of contention that I won’t get into here, but are an especially difficult biological unit to justify in the fossil record).

Within the fossil record, what was once several described species of Terrapene have more or less been synonymized over the years with T. carolina, with most of the morphological distinctions boiling down to subtle differences in size, shell width, and other variation in shape. Most researchers in this group have come to the conclusion that the variation in the fossil record reflected the same patterns of variation that are observed in modern biota. But is that correct? Are we looking at fossil subspecies, or are we looking at dimorphism or changes across different age levels? This is what Vitek wanted to test.

Using geometric morphometric software, Vitek examined and measured 435 extant specimens and 57 fossil specimens of T. carolina. 

Diagram of landmarks and semilandmarks used to study the shape of the carapace of Terrapene carolina. Open circles represent landmarks. Smaller, closed circles represent semilandmarks. (A) Dorsal view. Carapace drawn based on UF 21176. (B) Lateral view. (C) Posterior view. Carapace in B and C drawn based on UF 151664. From Vitek (2018). CC-BY.

When it came to determining maturity, size cannot be a dependable factor. Instead, Vitek determined that features such as growth rings, ossification within the carapace, and skeletal changes are better at determineing the approximate age of a specimen.

As far as sexual dimorphism, what was previously used as a skeletal feature for determining sex of a turtle turned out to be unreliable feature, according to Vitek. With plastron indentation, which has been used as a sexually dimorphic feature in previous studies, many errors were found where males or females were misidentified in museum collections. In living box turtles, this is not a problem because many soft tissue features, such as head coloration, are reliable in distinguishing male and females. Size is also not reliable to distinguish between males and females. Vitek points out, based on her research, that there is little support for determining sexually dimorphic characters in the fossil record at this point.

In terms of subspecies, Vitek concludes, based on her study of extant and extinct Eastern Box Turtles, that the subspecies system is not a reliable way to represent the variation that is seen in carapace shape in T. carolina. Her study shows that there is a lot of overlap in carapace shape, and she is unable to corroborate the hypothesis that there are diagnosable differences in the shapes of carapaces of the four subspecies. However, Vitek does support that geographical variation or size variation more closely ally with subspecies diagnoses that carapace shape.

Geographic representation of the two spatial eigenvectors (SEs) that account for subspecific differences in shape and shape differences predicted by those SEs in carapaces of modern T. carolina. Predicted mean shapes show maximum and minimum values of (A) SE2 and (B) SE3 in (C, F) dorsal, (D, G) lateral, and (E, H) posterior views, respectively. Line drawings indicate hypothetical carapaces consistent with each landmark configuration and are not exact predictions of all sulcus locations. From Vitek (2018), CC-BY.

What about the fossil record for these turtles? Vitek is able to conclude that, overall, the interpretation of intraspecific variation in fossilized T. carolina is reflective of the variation in modern T. carolina. However, some morphological characters, such as size in some of the fossil populations, do not follow the predicted trajectory of the analysis and may represent something more than just extra growth. In addition, some of the fossil specimens that differ greatly in the shell morphology could possibly be misdiagnosed as T. carolina, and could possibly belong to T. putnami, another problematic species that is known from a portion of a plastron that wasn’t examined for this study.

What is important about this study is that it shows that paleontologists should not work in a bubble of extinct taxa only. The variation in fossil taxa could have easily been (and at one point was) misconstrued as several distinct species, when in fact it represented intraspecific variation. But taking into account patterns of variation seen within living representatives of the group helped shed light on a more accurate interpretation of the extinct biota.

Reference:Vitek NS (2018) Delineating modern variation from extinct morphology in the fossil record using shells of the Eastern Box Turtle (Terrapene carolina). PLoS ONE 13(3): e0193437.

Featured Image: Eastern Box Turtle (Image Credit: Andrea Janda/Flickr/CC BY-NC-ND 2.0)

Source: Shell Shock! Can morphometrics distinguish fossil turtle species? | PLOS Paleo Community


Top 10 Open Access Fossil Taxa of 2017: Eekaulostomus cuevasae | PLOS Paleo Community

This is an article I wrote for the PLOS Paleontology Community blog, and am archiving it here. The original post was published on December 28, 2017, and can be accessed here.

With the end of the year comes the end to our countdown of the winners of the Top 10 Open Access Fossil Taxa of 2017. We appreciate everyone that took the time to read all of the contenders this year and to vote in the contest!

At Number 1 is the armored trumpetfish Eekaulostomus cuevasae from the Paleocene of Chiapas, Mexico! Published in the Open Access journal Palaeontologia Electronica by authors Kleyton Magno Cantalice and Jesús Alvarado-Ortega, this unusual fish is related to modern-day trumpetfishes and represents the oldest-known representative of the acanthomorph fish superfamily Aulostomoidea.

Artistic rendition of Eekaulostomus cuevasae, art by Brian Engh (

I asked the lead author of this study, Dr. Kleyton Magno a few questions about this remarkable fish. Dr. Magno is currently a postdoctoral researchers at the Universidad Nacional Autónoma de México (UNAM).

PLOS Paleo: Tell me about the discovery of this fossil!

KM: In reality, this species was collected by Mr. Alberto Montejo, a local quarry worker and owner of the Belisario Dominguez paleontological site. In the annual expedition to Chiapas in 2010, he gave this specimen to Drs. Jesús Alvarado and Martha Cuevas, as a donation to the Paleontological National Collection (housed into the Instituto de Geología, Universidad Nacional Autónoma de México). This single specimen was found just at the end of a hard fieldwork day, when a tropical storm was about to start. Then, Mr. Montejo noted a shining small part of this specimen on a place away from the work area, where the unwanted flagstones are accumulated; it was almost covered by the fallen leaves of the rainforest jungle in Chiapas. A desperate search was undertaken to find the counterpart of this specimen; however, the force of rain and the night denied such a possibility.

At first glance, Dr. Alvarado though that this fish was an extinct representative of the seahorses or pipefishes due the armored trunk. He was ready to prepare and describe this fossil when I entered the scene. My involvement in this discovery began in 2016, when I joined the Instituto de Geología of Universidad Nacional Autónoma de México as postdoctoral researcher. The aim of my work is to describe the spiny fishes of different Mexican localities, manly those from the Paleocene outcrops near Palenque City. When I first saw this specimen I immediately identified some characteristics that could resemble a syngnathid, however, by its body shape and configuration of the unpaired fins it seemed more likely to be a  member of the group that includes cornetfishes and trumpetfishes (Superfamily Aulostomoidea). During this study, we began to discover the remarkable features of this fish, some of them never been seen in this group, such as two stout, paired spines on the dorsal and anal fins, few soft rays on fins, and the body and snout covered by rigid star-like scales.

As we went deeper into the study I felt very excited; this was my fist fossil fish described, and it was already revealing itself to be an important clue to understanding the natural history of the aulostomoids, as it extends the fossil record of the group up to the Paleocene. Extant aulostomoids members are easily distinguished from their relatives (i.e., shrimpfishes, pipefishes, and seahorses) by the absence of rigid dermal scutes on the external surface of the body, as well as other features, such as a long body with parallel dorsal and anal fins, and a somewhat deep caudal peduncle. However, our aulostomid fossil was entirely covered with stout scutes. The inclusion the new species Eekaulostomus cuevasae in a morphological phylogenetic analysis, previously proposed by Keivany and Nelson (2006) for extant groups corroborates our hypothesis that this species is the oldest member of the Superfamily Aulostomoidea. This evidence and the comparison of E. cuevasae with other fossil aulostomoid allow us to infer new insights about the evolutionary history of the Superfamily Aulostomoidea.

Eekaulostomus cuevasae, holotype specimen and reconstruction. From Magno and Alvarado-Ortega (2017)

What does this fish tell us about the evolutionary history of Aulostomoidea?

Firstly, the Paleocene age of Eekaulostomus cuevasae represent an increment around 15 Ma on the origin and early diversification of aulostomoids, since the oldest forms were found in the middle Eocene of Europe (Pesciara of Monte Bolca, Italy). Furthermore, its geographical position is the first evidence of the Caribbean origin of aulostomoids with posterior diversification and currently worldwide distribution on tropical seas that still needs to better understood.

Eekaulostomus cuevasae is in the stem-group of aulostomoids. This allow us to say that the loss of dermal scutes, as well as stretching and tapering body, and the increment in the numbers of dorsal and anal soft rays are important morphological changes through the aulostomoid evolutionary history. We believed that these changes are morphological improvements on locomotion, buoyancy and adaptations to peculiar predatory behaviors present on extant aulostomoid species. The living species Aulostomus chinensis, for example, has the strategy to make reverse movements or maintain its body statically on the horizontal position, camouflaging between corals to opportunistically catch the prey.

What was the habitat and lifestyle of these fish? With their unusual heads, what did they feed on?

Unfortunately, little can be inferred about the habitat and lifestyle of this fish. Other fossils from the same locality of Eekaulostomus cuevasae are crabs, coprolites, fragments of turtles, carbonized plants, and a singular fauna of fishes that indicates a marine environment with some freshwater influence; however, more details about the paleoenvironment are still required. For now, what we can say is that E. cuevasae probably was a bad swimming, marine species that lived on marine shallow water, feeding on some crustaceans and small fishes using the peculiar method of prey suction through its feeding apparatus composed by small jaws and extreme elongated snout, like as in living aulostomoids forms.

The scales/scutes if this fish are really bizarre, and don’t look like fish scales at all! How did you recognize what you had? Do any other fish have scales like these?

As I mentioned previously, although living aulostomoid species do not have rigid body coverage, all close relatives have them. Nevertheless, the body coverage on these groups are composed of parallels bony plates that are quite distinct from the star-like scutes present on Eekaulostomuscuevasae. Its generic name is based on the shape of the scutes on this species. The prefix “Eek”, is a Mayan word that means “star” and, together with the word “aulos” (a kind if flute in Greek) and “stoma” (mouth in Latin) composes Eekaulostomus, in reference to a flute mouth fish with star-like scales.

The scutes of Eekaulostomus.

Anything else you’d like to share with us about this fish?

We decided to honor our colleague Dr. Martha Cuevas Garcia naming this fish as Eekaulostomuscuevasae because of her initial impulse that allowed us to perform several of the paleontological projects that are currently developing in Chiapas. Although she is an archaeologist who has spent years of work on different archaeological themes related to the Palenque Maya site, after work together in the paleontological prospection works in the southeastern part of Mexico, now she claims her love for fossils.

Congratulations to the UNAM team on this fantastic discovery of this fantastic fish Eekaulostomus and being chosen as the #1 Open Access Fossil Taxa of 2017!


Cantalice KM and Alvarado-Ortega J (2017) Eekaulostomus cuevasae gen. and sp. nov., an ancient armored trumpetfish (Aulostomoidea) from Danian (Paleocene) marine deposits of Belisario Domínguez, Chiapas, southeastern Mexico. Palaeontologia Electronica 19.3.53A: 1-24.

Keivany Y and Nelson JS (2006) Interrelationships of Gasterosteiformes (Actinopterygii, Percomorpha). Journal of Ichthyology, 46:S84–S96.


Top 10 Open Access Fossil Taxa of 2017: Websteroprion armstrongi | PLOS Paleo Community

This is an article I wrote for the PLOS Paleontology Community blog, and am archiving it here. I was originally published on December 5, 2017. You can see the original post here.

We listened to your feedback from last year’s Top 10 OA Fossil Vertebrates contest, and we agreed. Non-vertebrates needed representation, too! So of the 45 nominees we included in the contest this year, 1/3rd represented various plants, algae, insects, crustaceans, etc.

And as we continue the countdown of the winners of the PLOS Paleontology Top 10 Open Access Fossil Taxa of 2017, I am pleased to feature our first representative of an invertebrate taxon. Coming in at #8 is the fossil bobbit worm Websteroprion armstrongi, from the Devonian Kwataboahegan Formation of Ontario Canada. Described by authors Mats Eriksson, Luke Parry, and Dave Rudkin and published in the Open Access journal Scientific ReportsWebsteroprion represents the oldest bobbit worm (about 400 million years old), and a giant bobbit worm at that!

An artistic reconstruction of Websteroprion amrstrongi attacking an acanthodian fish. Art by James Ormiston.

Now if you are unfamiliar with bobbit worms, then you are in for a terrifying treat. These unusual polychaete worms are still living today and are vicious predators, laying in wait buried in the ocean sediment, their jaws poised like a bear trap, springing to life the minute a hapless fish swims idly by, only to be sucked into the sediment, becoming a meal for an unusual creature. Just watch this video below, courtesy the Smithsonian Channel on Youtube, to see a living bobbit worm in action.

These organisms are mostly soft-bodied, with the exception of their mouthparts, known as scolerodonts. So in the fossil record, often only the scolerodonts are preserved, and they usually aren’t that big. It was the size of the scolerodonts of Websteroprion that caught the eye of the authors. Mats Eriksson, lead author on the study, described to me the discovery of the specimens in the collection of the Royal Ontario Museum (ROM):

“Luke Parry [second author and then a PhD student at the University of Bristol, UK] was doing guest research on full-body polychaete fossils at the ROM back in 2014, and Dave Rudkin [third author on this study and now-retired museum curator at the ROM] showed him the specimens. So, Luke took a quick photograph and sent it to me, knowing that I am an expert on this fossil group.”

Scolerodont fossil impressions of Websteroprion armstrongi. Courtesy Luke Parry Twitter.

Dr. Eriksson continues, “I was quite disappointed when I first laid eyes on the photographs. The state of preservation was far from exceptional and mainly representing negative casts, or imprints, in the rocks. At first I even concluded that it was not worthwhile pursuing since it was ‘just another’ new species without any exciting story to unveil. That is until I asked about the size! Since the original image did not come with a scale bar I had simply assumed that the specimen was of “standard” millimetre size. I did ask Luke, who said that they were in fact pretty big, and provided the scale. That is when I strongly suspected that these must be by far the largest fossil jaws ever reported in the published literature, and a hunch which subsequent research confirmed. Now, this certainly wet my wormy appetite!”

Websteroprion armstrongi CT-scanning reconstructions of scolerodonts in specimen  ROM 63120. Modified from Eriksson et al (2017). CC-BY.

For bobbit worms, these are pretty massive, and for a polychaete worm in the Devonian, even more impressive. With the jaws wide open, they would have spanned about 2 cm across. The body, though not preserved, is estimated by the authors to be over 1 m (3 feet) in length, compared to the body proportions of extant bobbit worms. “I would not say they are necessary bigger than the jaws of extant bobbit worms,” Dr. Eriksson explains to me, “but it was surprising to find such large specimens in 400 million-year-old rocks!”

As Eriksson explains further, “Gigantism in animals is an alluring and ecologically important trait, usually associated with advantages and competitive dominance. It is, however, a poorly understood phenomenon among marine worms and has never before been demonstrated in deep time based on fossil material in this group of animals. The new species demonstrates a unique case of polychaete gigantism in the Palaeozoic, some 400 million years ago.

“Our study also shows that gigantism in jaw-bearing polychaetes was restricted to one particular evolutionary branch within the Eunicida, but has evolved many times in different species in this order of worms. However, while representing an ancient ‘Bobbit worm’ and a case of primordial eunicidan worm gigantism, the specific driving mechanism/s for W. armstrongi to reach such a size remains ambiguous.”

Would Websteroprion have been an ambush predator like its modern-day relatives? “We have little (in fact no) empirical evidence of its diet,” Dr. Eriksson explains. “As we are lacking soft parts we do not have access to preserved gut contents. And there are no coprolites found that can be directly linked to the animal. Inferring the diet of extinct worms (even jaw-bearing ones) is difficult. Especially considering that there are jaw-bearing extant forms that, despite looking like ‘fierce’ carnivorous predators, have proven to have a wide range of feeding habits. With that being said, given its size and compared to its closest modern relatives, I would assume that W. armstrongi had a similar mode of life and feeding habit as the modern bobbit worms. So, perhaps the Devonian fish and cephalopods were not safe from this critter.”

As mentioned previously, Websteroprion specimens caught the eyes of the authors in the collection of the ROM, but were actually collected over 20 years ago.

“The fossil specimens were collected over the course of a few hours in a single day in June 1994, when Derek K. Armstrong of the Ontario Geological Survey was dropped by helicopter to investigate the rocks and fossils at a remote and temporary exposure in Ontario,” Eriksson explains. “Sample materials, from what proved to belong to the Devonian so-called Kwataboahegan Formation, were brought back to the Royal Ontario Museum in Toronto, Canada, where they were stored until they caught the eyes of us authors.”

He adds, “Our study is an excellent example of the importance of looking in remote and unexplored areas for finding new exciting things, but also the importance of scrutinising museum collections for overlooked gems.”

And Websteroprion being a large and possibly terrifying creature wasn’t badass enough, it has a pretty stellar namesake as well. Lead author Mats Eriksson, in addition to being a professor at Lund University, moonlights as a Metal musician, complete with a paleo metal band Primoridal Rigor Mortis. In naming Websteroprion, Eriksson chose to honor a fellow metal musician, Alex Webster, bassist for Cannibal Corpse. And in true Metal fashion, Eriksson recently commissioned an iconic painter for Metal albums, Joe Petagno, to fashion Websteroprion in a dark and fantastical scene worthy of a album cover. The art, which can be seen here, will be part of an upcoming exhibition, Rock Fossils, which will be in Luxembourg in June 2018.

Congratulations to Websteroprion and the team that described it for making the PLOS Paleo Top 10 OA Fossil Taxa of 2017


Eriksson ME, Parry LA, Rudkin DM (2017) Earth’s oldest ‘Bobbit worm’ – gigantism in a Devonian eunicidan polychaete. Scientific Reports 7:43061. DOI: 10.1038/srep43061

Source: Top 10 Open Access Fossil Taxa of 2017: Websteroprion armstrongi | PLOS Paleo Community