Examining the types of Devonian trilobites in North Africa

Trilobite biodiversity trends in the Devonian of North Africa

Bault, V., Crônier, C., Allaire, N., & Monnet, C.

Summarized by Tom Shea, a fourth-year geology major at the University of South Florida. After completing his degree, he plans on going to graduate school to study seismology. Outside of class, Tom likes to go to USF games and spend time at the beach. 

What data were used?  1,171 trilobite fossils of 556 different species found in 168 locations throughout Northern Africa.

Methods:  This study ranked the trilobite samples by taxonomic rank (i.e., species, genus, family, etc.) to find ranks which were unique to Northern Africa and then used that information, called taxonomic richness, to show the biodiversity trends over the course of the early Paleozoic. This experiment focused heavily on trilobite genera (plural of genus).

Results: The data show that the biodiversity of trilobites varied significantly from the late Silurian Period through the Devonian Period. During the late Silurian, specifically during the Ludfordian and Přídolí Epochs (~427-423 MA and ~423-419 MA, respectively), biodiversity of trilobites declined steeply until there were eventually zero trilobites in the entire region (figure 1; also refer to figure 1 for the geologic time scale terminology used throughout this summary). The biodiversity of trilobites started rising again once the Devonian Period began.

Figure: A graph showing the biodiversity of trilobite genera in the late Silurian Period and the entire Devonian Period. The x-axis represents time, running from the Ludfordian Epoch to the end of the Devonian Period. The y-axis represents the number of genera, running from 0 to 60. Four lines are plotted on the graph: one for shareholder quorum sampling for 70 samples, one for sampled in bin index, one for range-through diversity, and one for boundary-crosser diversity. Each of the four plots show that the population of trilobites in this area started at nearly none at the end of the Silurian, but then exploded during the first few epochs of the Devonian before crashing back down near zero once again in the mid to late Devonian.
Figure 1: This graph shows that the number of different trilobite genera peaked in the Emsian Epoch of the Devonian Period after a few million years of rapid growth, followed by the population crashing right back down to near zero. The different curves indicate different measures of diversity, but all follow the same overall trends of the highs and lows of diversity.

During the early to mid-Devonian, and particularly in the mid to late Pragian Epoch within the mid-Devonian (~410-407 MA), trilobite diversity rose rapidly, from around 10 different genera in an interval to around 40 in only 1.5 million years. Once the Pragian gave way to the Emsian Epoch (~407-393 MA) though, the trilobite numbers in North Africa began sharply decreasing once again. This decrease continued until around halfway through the epoch, when the trilobite biodiversity suddenly and rapidly rose once again. The trilobites in North Africa eventually peaked with roughly 60 different genera sampled in a single interval near the end of the Emsian. After the peak, the number of genera began rapidly falling, a fall which became even steeper when the Emsian became the Eifelian Epoch. The event became known as the Choteč Event, which was relatively minor to most creatures for an extinction event but was absolutely devastating to trilobites in North Africa; this was caused by water becoming much deeper and causing extinction in shallower water trilobites. Trilobite numbers continued falling until there was not a single genus of trilobite living in this part of North Africa, which happened shortly after the Frasnian Epoch of the Devonian (~383-372 MA) began. Some genera of trilobites would return to North Africa later in the Frasnian, and these trilobites in the area fared better than many other creatures would in the Kellwasser mass extinction (~372 MA, the boundary of the Frasnian and Fammenian epochs of the late Devonian), which was one of the largest mass extinction events in history. Three of the five remaining orders of trilobites went extinct due to the Kellwasser event, severely limiting the chance of trilobite biodiversity in North Africa being anywhere near what existed prior to the Choteč Event.

Why is this study important? This study is important because it revealed a lot about the history of the past ocean, now part of Morocco, and the chronostratigraphy of that area, meaning the types of rocks in relation to the time period. This study ties sea level change and hypoxia (i.e., low levels of oxygen) to biodiversity in trilobites. For example, the sea level rise of the Choteč Event caused extinctions in shallow water trilobites; since trilobites were unusually hard-hit during the Choteč, this allowed scientists to see a different view of this geologic event. The Kellwasser extinction showed increasing hypoxia that led to extinction as well. With such a great fossil record like the trilobites seen here, we can get extremely detailed pictures of how certain groups responded to extinction events.

The big picture:  This study shows that by looking at the fossil record, you can tell a lot about the geologic history of an area. It is also important to note that this study helps us understand more about extinction events and biodiversity trends in the Paleozoic of Africa, as most paleontological studies have focused on data collection from Europe and North America that tend to bias our understanding of global events. 

Citation: Bault, V., Crônier, C., Allaire, N., & Monnet, C. (2021). Trilobite biodiversity trends in the Devonian of North Africa. Palaeogeography, Palaeoclimatology, Palaeoecology, 565, 110208–. https://doi.org/10.1016/j.palaeo.2020.110208

From Lichen Trees to Woody Trees

Ordovician-Devonian lichen canopies before evolution of woody trees

Gregory J. Retallack

Summarized by Saraiyh Newton, an undergraduate geology student at University of South Florida.

What data were used? Nematophyte fossil data was collected from the Silurian-age Bloomsburg and Ordovician-age Juniata formation (in Pennsylvania and Tennessee, USA respectively); ancient layers of soil called paleosols, that encases the fossil nematophytes, were also used in this study. Nematophytes are a loosely defined grouping of organisms such as algae and lichen found in the Silurian to the Devonian period that were able to form large canopy- like structures (similar to tall trees in modern forests); in this study, the nematophytes are the lichen canopies the title alludes to. The researcher used various data from modern plants to calculate estimated heights of the fossil lichen canopies. 

Methods: This study illustrates the presence of these nematophytes that created canopies, which has components that could have nurtured early land plants that grew under it, which would eventually allow woody trees to thrive. First, the study identifies where the nematophytes are through various methods, like visual surveys of the paleosols for features such as extensive fungi-like root traces.

Brownish bedrock with white, clay cracks lines covering the bedrock (these lines are root traces) on this bedrock is a rock hammer on the right of the picture for scaling and multiple arrows along the top of the image to indicate where the root traces are purposes. Total image is about 2 hammers high.
Evidence of nematophyte root structures (white arrows) in paleosols of the late Silurian Bloomsburg Formation. Hammer for scale.

After finding the nematophyte remnants, the study author calculated the possible height that the nematophytes might have grown to when they were alive. Plant height is calculated by using an allometric growth equation, which is the relative change in proportion of a part compared to its body, based on 670 modern species of trees. This equation uses the trunk’s diameter at about 1.4 meters above the trunk’s base, or breast height, to calculate the height of the tree. With the calculated height, Retallack calculated the possible density of plants per square meter to create a picture of what forests may have look like with these nematophytes. 

Results: The calculated density and spacing between the trees (which is also found within the paleosols) illustrates a dense cluster of the nematophytes within ancient forests. Since these nematophytes were most likely densely clustered all over forest during the time, these organisms might have nurtured and created an environment where vascular plants, like woody trees, would be able to thrive in the future (later Devonian to present, when trees became extremely widespread). This could have happened because the nematophyte fungi-like roots had an extensive reach in the soil and this fungi network could have nourished environments to the point where plants would have thrived.

Why is this study important? This topic is quite interesting because when we look at modern lichen, they are mostly flat, low growing organisms. They usually do not grow very tall, but they can spread over different surfaces in the forest. So, knowing this about modern lichen species and learning that there was once lichen species that were big enough to have canopies could show how forest ecosystem and species changes over time. 

The big picture: These nematophytes can illustrate how a dominating species in a region can create an environment that allows newer species to thrive in the future. These nematophytes made a good environment for woody trees to thrive in and woody trees eventually became a dominate plant grouping, so we may be able to study how woody trees might be facilitating the evolution of other organisms, too. Learning about how species affect the world around them can improve our knowledge on how ecosystems can change over time. 

Citation: Retallack, G., 2022. Ordovician-Devonian lichen canopies before evolution of woody trees. Gondwana Research, 106, pp.211-223.

Ancient saber-tooth cats may have been more social than we thought

Computed tomography reveals hip dysplasia in the extinct Pleistocene saber-tooth cat Smilodon

Mairin Balisi, Abhinav Sharma, Carrie Howard, Christopher Shaw, Robert Klapper, Emily Lindsey

Summarized by Nicole Christensen, a senior geology major at the University of South Florida. She went to community college for her Associates’ degree, and initially started working on a degree in Environmental Engineering before pursuing geology instead. She likes many different fields in geology and isn’t yet sure what she would like to specialize in, but she knows she’d like to get her Master’s degree someday. In her spare time, she likes to play music, draw, and knit.

What data were used? The pelvis (hip) and right femur (upper leg bone) of a saber-tooth cat were found in the Rancho La Brea asphalt seeps in California. The pelvis was an unusual find, as it is asymmetrical, with a build-up of bony growth on the right side. The disfigured right hip socket is shallow and oval-shaped, rather than the circular shape of a healthy socket. This disfigurement was originally thought to be due to an infection when the animal was alive; however, further disfigurement is seen on the later-found matching right femur, which bears a flat head instead of a typical rounded one, to fit the shallow hip socket.

Methods: All fossils were collected from the same deposit to limit the range of time represented in the study. Dr. Balisi and her team then observed the surface of the pelvis and femur, comparing their characteristics to other deformed bones from different specimens of the same species. A 3D scan was taken using an Artex Space Spider, which is a type of 3D scanner that produces high-resolution color scans. They then used CT scans to capture images of the internal structure of the bones and allow the 3D models to be cross-sectioned. The cross-sections allowed them to determine cause of the deformations. Since the bone lacked fractures, calluses, or healing markings and the bones did have the presence of arthritic degeneration, researchers were able to narrow down the causes, explained in the results. In order to estimate body size, they measured the pelvis length and femur circumference in question, as well as other deformed and non-deformed femurs and pelvises of other specimen from the same location as a comparison. 

Four different angles of the deformed pelvis on white background, each to show off the extent of the deformation clearly. The right hip socket where the femur would fit is much shallower and larger than the non-deformed left hip socket. The left hip socket has a ridge to keep the femur in place, which the right hip socket is missing. The pelvis is asymmetrical; the right side is smaller with thick bony growths, while the right side is smooth.
Figure 1: The recovered deformed pelvis of a saber-tooth cat. A) The right-side view, showing deformation of the hip socket. B) The left-side view, showing a non-deformed hip socket, but with extra bone growth around the edge. C) The top view and D) bottom view, showing that the pelvis is asymmetric.

Results: The deformations seen in the femur and pelvis, shown in Figure 1, are consistent with hip dysplasia, a condition that the Smilodon in question was born with, rather than due to an injury later in life. The femur wasn’t fully developed, and so it didn’t properly fit into place against the pelvis. This would have led to pain when walking, causing the cat to not bear weight on its right leg. Researchers ruled out possibilities that the cat could have had an injury, infection, or degeneration over time. If the cause was injury or infection, the femur and pelvis would have been fully developed before the degeneration began, and so the top of the femur would not have been affected. However, the femur of this study has a deformed head, indicating the hip socket was not properly developed. In the same area that the studied pelvis and femur were found, there were several other pelvises that showed signs of deformation similar to the pelvis of this study.

Why is this study important? Saber-tooth cats are ambush predators. They wait until the right moment to leap at their prey and then drag it to the ground. It would have been very difficult for one to reach adulthood without being able to use one of its hind legs effectively. Based on the size of the pelvis and femur, the studied Smilodon lived to adulthood. Hip dysplasia begins to affect animals from a young age. This means it is likely that saber-tooth cats lived in communities, which provided both food and protection from predators to those who could not take care of themselves.

The big picture: Evaluations of bones and their markings can lead to discoveries about the lifestyle and behavior of extinct animals, even ones as well-known as Smilodon. Many living species of cats do not show social behavior, making this an advancement in understanding the behavior of Smilodon. Modern technology, such as CT scans, can bring about new methods of evaluating bones past their surface appearance. In this study, CT scans showed evidence of degenerative arthritis in the right hip socket, as well as markings on the top of the femur. Both of these indicate the deformation results from hip dysplasia. CT scans could also build a paleopathology dataset for reference in future studies. 

Citation: Balisi, M. A., Sharma, A. K., Howard, C. M., Shaw, C. A., Klapper, R., & Lindsey, E. L. (2021). Computed tomography reveals hip dysplasia in the extinct Pleistocene saber-tooth cat Smilodon. Scientific reports11(1), 1-12. https://doi.org/10.1038/s41598-021-99853-1

 

Crab Population Decline Since the Late Pleistocene

Predation Scars Reveal Declines in Crab Populations Since the Pleistocene

Kristina M. Barclay, Lindsey R. Leighton

Summarized by Nicholas Stanton, a geology major at the University of South Florida. Nicholas is a Navy veteran who went back to school to follow his passion in the study of Earth’s history. Nicholas has worked for USGS for 2 years as a hydrographer, continuing his love for all things science.

Data that were used: The number of customers that visited Joe’s Crab Shack in a month was the determining…. JOKING. The data that was used in determining if there was a decline in crab populations is quite fascinating and it starts with snails. The Tegula funebralis to be specific, but to make it a little easier these can be referred to as a black turban snail. These snails are extremely helpful, telling stories of the past by their healing attributes. They leave remarkable healing scars after attacks from predators, also known as predation scars.

Methods that were used: So, we just count how many snails have predation scars and that accounts for how many crabs there are in the ocean right? Well, there are a few other factors that need to be eliminated before we can equate these two pieces of information. For example, can the failure of crab attacks account for fewer scars due to the snail shell never being penetrated to create a scar in the first place? Or, can the size of the snail and the size of the crab determine the amount of predation scars found? Well, it is a good thing science rules and we have a bunch of cool scientists that have already conducted studies to help in answering these questions. Other studies have inadvertently shed light on this by answering these questions, even though the purpose of their study was not to calculate crab populations. This other study ended up showing that a change in the success of crab predation is not an explanation for a change in repair frequency. Instead, it is likely that the change in repairs is caused by the change in crab population. In the study summarized here, fossil and modern specimens were collected to compare and determine the crab abundance dating back from the Pleistocene to present day, with the maximum geologic age for the fossils extending to 120 ka (thousand years). Most of the fossils were taken in southern California, specifically the Palo Verdes Hills and the San Diego area. The modern specimens also came from these same areas as to reduce biases in the study. A total of 712 fossil specimens were gathered, 261 from the Palos Verdes Hills area and 451 from the San Diego area. The modern specimens came from seven locations in the same two areas previously listed. Collecting these modern samples was tedious to ensure certain biases did not enter the study. Researchers would walk up and down in symmetrical lines spaced two meters apart collecting around ten to twenty snails on each line. This was done until a total of 1,152 snails total were collected.

A dark colored snail with a cone shape that gets narrower as it extends upward. There is scar, which is a jagged vertical scar that covers 2/3rds of the cone shaped shell on the side. This scar was caused by predation from a crab. Left is a side view, right is a bottom view of the snail
Figure 1: These are examples of predation scars on the black turban snail. In box A the red arrow is pointing to a typical repair scar seen in these snails. Box B shows the size of the snail being taken at the time of attack. This helps show the size at which the snail was and the success of the attack. A snail with a high conical shape and a large groove covering nearly 2/3 of its body shows signs of repair from predation scars.

Results: It was discovered that modern black turban snails have fewer scars than those fossils dating back to the Pleistocene. It was concluded from the study that changes in the frequency of repairs since the Pleistocene is indicative of a change in the number of attacks. The maximum size of repairs between the fossils collected and modern samples were similar, showing crab strength had not changed much over the years. This helped eliminate the thought that lower predation scars were due to the lower success of attacks. This tells the researchers that the crab population has declined since the Late Pleistocene, due to the decline in predation scars in snails.

Why is this study important? Paleontology is crucial for understanding the story book of Earth’s past. It is a nice guide in determining questions about Earth’s future, as well. Fisheries have poor data and little money to invest in expensive research on how to maintain their fishing numbers in the ever-declining industry. Overfishing is playing a huge part in the decline of not only crab population, but thousands of species of marine life. For example, Somalia was once a successful fishing port, but due to larger countries overfishing those waters, the economy collapsed. This is a devastating notion that an entire country’s economy can be significantly affected due to overfishing.

The big picture: This study has mapped an entire population of crab, and this can inform fisheries on how to sustain a healthy number, without depleting the entire species. Things such as climate change, long line fishing, and pollution are wiping out our marine diversity swiftly. Paleontologists, as well as all other scientists, understand the effects of climate change and pollution on Earth’s ecosystem. These scientists are on the front lines combating these realities with knowledge, with evidence, and with SNAILS! 

Citation: Barclay, K. M. & Leighton, L. R. (2022). Predation scars reveal declines in crab populations since the Pleistocene. Frontiers in Ecology and Evolution. https://www.frontiersin.org/articles/10.3389/fevo.2022.810069/full 

The Youngest Pangolin Species Originating From Europe Has Been Found in Romania

The youngest pangolin (Mammalia, Pholidota) from Europe

Claire E. Terhune, Timothy Gaudin, Sabrina Curran, Alexandru Petculescu

Summarized by Isabelle Snowball, a fourth-year geology student at the University of South Florida. She has a particular interest in GIS. In her free time, she enjoys various forms of art and spending time with her friends.

Key Terms: Pangolin – an armadillo-like mammal with scales covering its body, a long snout, long tapered tail, and long tongue which it uses to catch and eat insects; humerus – the bone in the upper arm of an organism; synapomorphy – a characteristic shared exclusively by a species and its descendants.

What data were used: Scientists in Graunceau, Romania uncovered a pangolin humerus–the youngest ever found in Europe. Specimens from this fossil collection are estimated to be from the Villafranchian age, a period of time ranging from the Late Pliocene to Early Pleistocene in an area scientists think represented a woodland environment. This dates the specimen to be around 1.8-2.2 million years old (Ma). The specimen is stored at the ISER (Institute of Speleology, Bucharest, Romania). Data from currently surviving species of pangolin were used to compare other humeri measurements to those of the Smutsia olteniensis humerus, the fossil central to this study.

Methods: The pangolin humerus (Fig. 1) was appropriately photographed and cataloged, which included creating a 3-D model by scanning the specimen with an HDI 120 Blue Light scanner. The humerus was compared to data collected from the humeri of twelve other pangolin specimens—specifically examining measurements for length and width of a number of  shoulder, arm, and leg bones. 

Figure 1: A 3-D Model of Smutsia olteniensis humerus

Results: Scientists determined that the newly found specimen had all of the features of a modern pangolin, or Pholidota. Specifically, this specimen is more closely related to modern species of pangolin. Still, it boasted enough unique traits to earn its place as a new species of pangolin, Smutsia olteniensis. Given the woodland environment of the Graunceau site, we know it is possible that Smutsia olteniensis was open-adapted, meaning it preferred open woodlands as opposed to the tropical environments modern pangolins prefer.

Why is this study important? Little is known about the fossil record of the pangolin. They are believed to have emerged in Europe during the Eocene and disappeared from the European geologic record during the Miocene, potentially in search of warmer, more tropical environments. Up until now, the only evidence of pangolins’ existence during the Plio-Pleistocene came from Africa.

The big picture: With this newfound specimen dating back to the early Pleistocene, it appears that not only did pangolins stick around Europe longer than previously thought, but that they may have occupied a wider geographic range as well. Scientists have concluded two possibilities—the first being that pangolins may have remained in Europe as late as the Pleistocene, and the second being that they did migrate to Africa, but eventually made their way back to Europe by the Pleistocene. 

CitationsClaire E. Terhune, Timothy Gaudin, Sabrina Curran & Alexandru Petculescu (2021) The youngest pangolin (Mammalia, Pholidota) from Europe, Journal of Vertebrate Paleontology, DOI: 10.1080/02724634.2021.1990075

Lorenzo Rook, Bienvenido Martínez-Navarro, Villafranchian: The long story of a Plio-Pleistocene European large mammal biochronologic unit, Quaternary International, Volume 219, Issues 1–2, 2010, Pages 134-144, ISSN 1040-6182, https://doi.org/10.1016/j.quaint.2010.01.007. (https://www.sciencedirect.com/science/article/pii/S1040618210000170)

Northern Florida bear fossils reveals new species of Indarctos in North America

Coexistence of Indarctos and Amphimachairodus (Carnivora) in the Late Early Hemphillian of Florida, North America

Qigao Jiangzuo · Richard C. Hulbert Jr.

Summarized by Eric Kastelic, who is a geology major at The University of South Florida. Currently, he is a senior. Starting in Fall 2022, he will be pursuing graduate studies in hydrogeology focusing on groundwater recharge and once he earns his degree, he plans to work as a research hydrologist or become a research professor. When he’s not studying geology, he loves to go on walks with his friends and explore nature!

What data were used? ~ 7.5–6.5 million year old Indarctos fossils from the Withlacoochee River 4A Formation in Northern Florida, USA. These fossils were compared to previously collected specimens from elsewhere in the United States and China. 

Methods: This work descriptively compared ~ 7.5–6.5 million year old  Indarctos fossils form Northern Florida with corresponding Indarctos fossils from formations in Kansas, Texas, Oregon, California and Nevada. Additionally, fossils from Northern China were reviewed to connect a possible ancestral relationship.  

Results: This study investigated at least four Indarctos individuals found in the Withlacoochee River 4A Formation of Florida. As it is uncommon to find numerous individuals in one site, this fossil find marks one of the most comprehensive groupings of Indarctos fossils in in North America. These four individuals made it possible for the researchers to compare jaw, dental, neck, pelvic, and heel properties between the specimens at the formation and other Indarctos fossils worldwide. The similarities in dental characteristics between Indarctos of the Withlacoochee River 4A formation and I. oregonensis, a species of Indoarctos, paired with differences in slenderness of postcranial bones between the Florida specimens and I. oregonensis (skeleton excluding the skull) shows a at least two variations of postcranial bones in North America. What does this mean about the Florida Indoarctos? Is it a new species? This works makes no definite support or rejection of the Indarctos of the Withlacoochee River 4A Formation being a previously unknown species, but acknowledges the need for further research to determine this. 

 Photo of bear skull fossil from two differing areas with similar shape and size. The Indarctos skull fossils from the Withlacoochee River 4A in northern Florida is approximately 30 cm in length, yellow in color, has teeth with two prominent front teeth, and the piece of the skull between the top of the skull and nose is missing. The I. zdanskyi from Baode in North China is about 40 cm in length, white in color, has four prominent front teeth, and is missing the bone supporting the left side of the face.
Figure 1: Top, bottom, and side views of a Indarctos skull fossils from the Withlacoochee River 4A in northern Florida (A1-3) and a I. zdanskyi from Baode in north China (B1-3).

Why is this study important? This study shows a possible unique species of Indarctos that hasn’t previously been identified. Indarctos throughout North America show a differing type of bone robustness, despite not being geographically separated. This work documents that Indarctos may have ancestors in northern China, showing a possible movement to North America from Eurasia in the geologic past. This work, paired with fossils of other fauna (animals) and climatic data, may be able to show shifts in ecosystems as a driver in the migration of Indarctos.

The big picture: New fossil finds strengthen understandings of how organisms moved across the globe in geologic time. The information gained form comparing Indarctos fossils provides insight into how other mammals may have moved.

Citation: Jiangzuo, Qigao, and Richard C. Hulbert. “Coexistence of Indarctos and Amphimachairodus (Carnivora) in the Late Early Hemphillian of Florida, North America.” Journal of Mammalian Evolution 28.3 (2021): 707-728.

The relationship between arm shape and lifestyle of brittle stars

The evolutionary relationship between arm vertebrae shape and ecological lifestyle in brittle stars (Echinodermata: Ophiuroidea)

Mona Goharimanesh, Fereshteh Ghassemzadeh, Barbara De Kegel, Luc Van Hoorebeke, Sabine Stöhr, Omid Mirshamsi, and Dominique Adriaens

Summarized by Emma Nawrot, who is a geology major at The University of South Florida and is currently a senior. Once she graduates, she plans on pursuing a career in Volcanology and Igneous Petrology. In her free time, she enjoys playing video games, hiking, and going to the beach!

What data were used? This study examined species of Ophiuroidea (brittle stars) that were specifically chosen to cover a large range in both species type and lifestyles that corresponded to distinct functions of their arms. Samples were gathered from fossils of the Persian Gulf and Oman between December 2017 to March 2018 and were classified based on their lifestyle and joint type. 

Methods: This study used a 3D analysis of a range of brittle star species to determine the structural relationships of their arm vertebrae (here, meaning the distinct pieces of their arms). Species were carefully chosen to cover a range of operational lifestyles associated to different usage of their arms. This included prehensile (grasping) and non-prehensile (non-grasping) species. At minimum, one specimen per species was utilized, across to seven families throughout the broader groupins within the ophiuroids. To obtain a better resolution of the structures, portions were removed from the middle and outer part of one arm per sample of brittle star for CT scanning. Every sample was CT-scanned using a HECTOR scanner. The vertebrae were digitally segmented from the CT scans produced and 3D models were created using a software called Amira. The acquired 3D model of each arm skeletal piece was then transformed into data that the computer could use to determine the differences in shapes between each of them. 

On the left is a diagram of a phylogenetic tree that displays the twelve different species used in the study and their relationships to one another as they have evolved through time. To the right of this tree are the 3D shapes of their arm skeletal pieces and joint types shown from two different perspectives: distal is shown on the left and proximal is shown on the right. The names of the joints are listed in grey and yellow boxes to the right of the shapes, with the grey representing the distal viewpoint and the yellow representing the proximal. The different species on the phylogenetic tree are highlighted in pink, yellow, and green depending on their lifestyle. Epizoic or living on another animal, are highlighted in pink. Endozoic or living within another animal are highlighted in yellow and epiphytic or growing on the surface of a plant are in green.
Phylogenetic tree of the 12 species used in this study and corresponding arm shape and life habits.

Results: The study showed that there was a significant amount of variability found in the arm vertebrae of different species of brittle stars. The results reflect how these structural differences represent specific adaptations, such as having the ability to hold onto other objects and creatures. Furthermore, unique shapes of arm vertebrae in brittle stars were found to be directly correlated to their functional and environmental lifestyles. It was observed that some species that were not strongly related, still converged to a comparable design in arm shape. Perhaps the most remarkable results that came from the study were the patterns of how the shape of brittle star vertebrae is directly associated to unique evolutionary adaptations. For example, the species Ophiura sarsii has longer distal arm skeletal pieces than Ophiocamax vitrea, which is a non-prehensile organism, meaning it cannot grasp onto objects. Ophiura sarsii is known to take part in significantly more hunting behaviors than Ophiocamax vitrea, and these longer arm skeletal pieces create a greater yielded force. This is an indispensable factor for its hunting activities as an active predator. 

Why is this study important? This study sheds light on the intricate nature of shape deviations in brittle stars and how these changes relate to their distinctive adaptations. It is the first study to connect morphological attributes of brittle stars to their modes of life using 3D modeling of their vertebrae. Through this modeling, insight was gained on the unique functional and ecological lifestyles of different species of brittle stars. Without understanding this relationship, we can’t begin to understand how these organisms changed over time and the evolutionary patterns they show. 

The big picture: Ultimately, this study will be extremely helpful in the future for inferring information that we can apply to the fossil record. For example, paleontologists often find disarticulated bits of ophiuroids where it’s difficult to ascertain their origins and morphological traits, so this could be helpful for researchers in pinpointing these patterns when there’s not much other data to go on.

Citation: Goharimanesh, M., Ghassemzadeh, F., De Kegel, B., Van Hoorebeke, L., Stöhr, S., Mirshamsi, O., & Adriaens, D. (2021). The evolutionary relationship between arm vertebrae shape and ecological lifestyle in brittle stars (Echinodermata: Ophiuroidea). Journal of anatomy.

Understanding the Fossil Record of Tiger Sharks

Evolution, diversity, and disparity of the tiger shark lineage Galeocerdo in deep time

Julia Türtscher, Faviel A. López-Romero, Patrick L. Jambura, René Kindlimann, David J. Ward, and Jürgen Kriwet

Summarized by Austin Crawford, a senior obtaining a Bachelor of Science in geology at the University of South Florida. Austin’s current career interests involve several fields in hydrology/hydrogeology, engineering geology, geologic/environmental consulting, geophysics, mine geology, oil and gas (OG), and geomatics. Aside from education, Austin enjoys spending time outdoors, riding his motorcycle, watching sports, listening to music, and spending time with family and friends. 

What data were used? 569 isolated teeth of both extinct and the extant (still living) tiger shark were examined for the basis of determining the geometric morphometrics, which is a method used to quantify shape of the teeth and disparity, which indicates differences between teeth of Galeocerdo. The ages of the teeth were also recorded. 

Methods: The 569 teeth samples (Figure 1) were each photographed with a labial aspect representation, which is the surface towards the lips. In addition, 18 published illustrations were included to compensate for more complete representation. The specimens were analyzed using a two-dimensional geometric morphometric system using landmarks. This means that the same 64 locations on each tooth were marked in a computer program (tpsDIG2). These landmarks were analyzed using a Generalized Procrustes analysis (GPA), which compared the differences in shapes across all of the teeth and summarized how different each of the shapes were. These data were analyzed using a Principal Components Analysis (PCA), which plots all of the variables’ differences into a 2D plane for easier analysis. Qualitative shape analysis by the researchers was also considered in the later portion of the study to describe features that weren’t included in the prior study, such as serrations in the teeth that are key identifiers for species within the genus Galeocerdo. 

Results: The conclusion of the procedure yielded three identified genera: Galeocerdo, Hemipristis, and Physogaleu and two unclear species, G. acutus and G. triqueter . The three genera and two species groupings were identified from the PCA, which showed the three distinct genera plotted on the graph. From the original 23 identified species of tiger shark, researchers here determined only 16 were legitimately considered because seven lacked illustrative characteristics. The distribution of these 16 species of Galeocerdo was made using the same processes used for the broader classification of all 569 shark teeth. The disparity through time for the tiger sharks falls into geologic time spans of Paleogene and Neogene-Quaternary. The PCA showed groupings of sharks by time spans, too. Paleogene sharks (G. clarkensis, G. eaglesomei, and G. latidens) occupy a distinct area of the principal components chart, indicating they are similar in shape. Tiger sharks within the Neogene-Quaternary are notably different in shape. 

The descriptions for all Galeocerdo species teeth are in lingual view (side of the tongue) with the distal side on the right and medial side on the left (away from the center of the mouth and toward it, respectively). Galeocerdo aduncus (A) is tan in color, smooth and is the smallest specimen of the six, coming close in size only to Galeocerdo clarkensis holotype (C). A contains rounded root lobes, strong serrations along distal side, strong notched distal edge, and very fine serrations along one side. Galeocerdo capellini (B) has a darker tan combined with some orangish and red tone, considerably rough texture, and is the largest of the six samples in size. Specimen B has the most rounded root lobes, conjoined rounded serrations, weakly notched distal edge, and medium sized with rounded serrations along the mesial side. Galeocerdo clarkensis holotype (C) is the roughest textured tooth of all six species, relatively small compared to the others, and has a combination of colors in green, grey, and brown. The morphology of C is the most abnormal compared to that of the remaining five shark tooth samples. The specimen has a poor notch at the root, rounded root lobes, a small number of wide serrations, strong distal edge, and curved side with poor serrations. Galeocerdo cuvier (D) is most noticeable by its cleft. The boundary marks the change between dark color and extremely smooth textured surface to a light, rough region of the root lobe. Galeocerdo cuvier (D) is large in size compared to the holotype of Galeocerdo clarkensis (C). Sample D has a square-like root lobe, fairly notched distal edge and prominent serrations on both sides. Galeocerdo eaglesomei (E) holotype is the easiest to recognize shark tooth of the six specimens. E is black in color, smooth texture, and medium sized. The resemblance of Galeocerdo eaglesomei (E) is close to that of the general shark tooth one might think of. It has three strong points in a triangle form with the two-edged root lobes and fine point in the apical region, no distal notch, and contains well-formed serrations along both the mesial and distal sides. Galeocerdo mayumbensis (F) is medium in size, contains some texture, and is mainly tan with some darker areas near the root lobe. Sample F is highly convex and has square root lobes, very weak distal notch, and rolled serrations along both sides.
Different morphology (like serrations, the sharp projections), color, texture, and size of the six significant tiger shark species teeth samples. Scale bars= 10 mm.
A: Galeocerdo aduncus. B: Galeocerdo capellini. C: Galeocerdo clarkensis holotype. D: Galeocerdo cuvier. E: Galeocerdo eaglesomei holotype.F: Galeocerdo mayumbensis

Why is this study important? Evolution, diversity, and disparity of the tiger shark lineage Galeocerdo in deep time serves an important part within the paleontology of Galeocerdo as a whole. The simple acknowledgement is beneficial to the genus. The authors state that this shark has been neglected compared to the other apex shark genera. The article is important to both the diversity and disparity between those diverse species of Galeocerdo throughout the Cenozoic. In doing so, the paleobiology of Galeocerdo can help with knowing phenotypes (the physical expressions of the genetic makeup) of the extant tiger shark today as well as its trend in the future.

The big picture: Apex sharks such as Galeocerdo serve an important purpose in the Earth’s oceans as they maintain the population of other prey. This results in an ecosystem balance for the plenty of other organisms that they feed off. Evidence shows that oceanic sharks and rays have been in decline globally since 1970 meaning a deteriorating diversity of higher order ocean species. Consideration of scientific studies on shark evolution is a way we as humans can protect the future of shark ecology.  

Citation: Türtscher, J., F. A. López-Romero, P. L. Jambura, R. Kindlimann, D. J. Ward, and J. Kriwet. 2021. Evolution, diversity, and disparity of the tiger shark lineage Galeocerdo in deep time. Paleobiology, 47:574–590.

Alyssa Anderson, Geologist

Tell us a little bit about yourself. My name is Alyssa Anderson, and I am an undergraduate student at the University of South Florida studying for a Geology and Environmental Policy B.S. I was born in New Jersey, but since Florida’s been my home since I was four years old, I consider myself more a Floridian. Outside of science, I enjoy world-building, writing, sewing, and reading. I think that’s part of why I enjoy geology so much, because I love creating worlds and making them geologically and scientifically accurate! But not completely, because I am a big fan of fantasy and fiction novels, so a little magic is fun, too. 

A white woman with short dark hair stands in front of a stream filled with large, flat rocks, smiling up at the camera. She is dressed for hiking and stands in the stream on a sunny day.
Figure 1: Hiking through the mountains in North Carolina, overjoyed at finding a stream filled with wonderful rocks.

What kind of scientist are you and what do you do? My path as a scientist leads me towards geology and the environment. Some of my major interests are hydrology and oceanography, but I am also very interested in other roles such as GIS and policy work. I am also beginning an internship managing climate change and climate data in some Florida counties, which fits in with my goal of being an environmental scientist.

What is your favorite part about being a scientist, and how did you get interested in science? My favorite part about being a scientist is the discovery. I love learning and being able to apply the knowledge I’ve learned into real-world applications is gratifying. I could study most any science field and be as happy as a clam because there is always something new for me to discover. 

A group of students pose near some rocks, two girls and a guy. The girl in the middle is white with short dark hair. The field surrounding the rocks is wide and open, with mountains in the distance.
Figure 2: On a geology field trip with some Mineralogy and Petrology friends, near part of the Appalachian Trail in Virginia. I am the dashing figure in blue posing by the rocks.

How does your work contribute to the betterment of society in general? My work in my current internship will benefit the Florida county I am assisting with, as it strives to understand and manage climate change impacts. It also gets students and staff involved in their local environment and brainstorming ways on how to solve some of the major environmental issues of our generation, i.e., climate change. Plus, it encourages more students to get into science and policy and I believe having a science background in a policy related field is extremely important for more well-informed laws and regulations.

What advice do you have for up and coming scientists? My advice for new scientists is this: spending some of your free time on hobbies you enjoy is a good thing. Sinking all of your effort and energy into studying without breaks will lead to burnouts and breakdowns. So, please, do take your time and don’t think that more work will lead to more results if you aren’t resting in between!

Ohav Harris, Undergraduate Geology Student

Ohav sitting in gravel in a museum exhibit under a T. rex.
Me with Stan the Tyrannosaurus rex at my internship at the Wyoming Dinosaur Center.

Tell us a little bit about yourself. Outside of science I enjoy reading manga, collecting Pokémon cards, and playing video games.

Describe what you do. I am an undergraduate researcher. I recently finished a project which involved entering geographic information of echinoderms (animals like and including sea stars, sea lilies, sea cucumbers, etc.) into a database so that we could analyze their biogeographic patterns (how the animals moved through time and space) in the geologic record.

I have done class visits with groups of fourth graders as a part of the Scientists in Every Florida School program to teach them about geology.

Discuss your path into science. I used to want to be a lawyer for as long as I can remember, but on my 17th birthday, I visited the American Museum of Natural History and was smitten with their dinosaur exhibits! After leaving, I was unsure if I wanted to continue pursuing a career in law, so I did some basic research of how much I could expect to make as a paleontologist (to make sure I could still support myself and a family) and decided to commit to the switch. After that, I have been pursuing dinosaur paleontology as best I can!

A dinosaur skull in rock with the sclerotic ring highlighted in purple.
The sclerotic ring (highlighted in blue) is a bony structure found in the eye of some dinosaurs and all modern-day birds. I am very interested in studying what those rings did for dinosaur eyes and how they developed. (source: ecomorph.wordpress.com)

Discuss other scientific interests. I’m very interested in birds and reptiles, specifically snakes. If I couldn’t study nonavian (non-bird) dinosaurs, I would study one of those groups of animals in the fossil record. I’ve also become quite attached to crinoids since starting my undergraduate degree, so they would be my invertebrate pick!

How does your work contribute to the betterment of society in general? Hopefully, with the echinoderm geographic data that I’ve collected, we can better understand of echinoderm evolution through time as well as how they dispersed across the world over time. 

I hope that I’ve convinced the classes I’ve visited that geology is a science that rocks! More than that, I also hope that I’ve made them more curious about how our world works, and to keep asking amazing questions and finding equally amazing answers.

Fossil sea lilies embedded in rock.
A crinoid fossil. I have been researching the geographic distribution of these ancient sea lilies and other echinoderms, like sea stars, and I thought this was a very nice fossil to show how neat they are! (source: fossilera.com)

Is there anything you wish you had known before going into science? Mainly, what classes I would have to take. In my case, I had multiple major options, but didn’t look too far into them. I’m very happy where I am now, although I’m sure there is an alternate universe version of me that is going down the biology route. 

Have you received a piece of advice from your friends/mentors/advisors that has helped you navigate your career? I’ve gotten good advice about grad school. In particular, I should be reaching out to professors I would like to work with a good while before applications are due.