Using Modern Rainforests to Study Fern-Insect Interactions in the Fossil Record

Fern-Arthropod Interactions from The Modern Upland Southeast Atlantic Rainforest Reveals Arthropod Damage Insights to Fossil Plant-Insect Interactions

Summarized by: Haley Vantoorenburg is a geology major at the University of South Florida. Haley currently researches encrusting organisms on Paleozoic brachiopods and plans to work closely with fossil preparation and preservation studies in the future.

What was the hypothesis being tested (if no hypothesis, what was the question or point of the paper)? Ferns were some of the first plants to have evolved broad leaves (fronds) in the fossil record (the earliest known records are about 360 million years old). These broad leaves allow large areas of insect damage from insects present while the plant was alive to be preserved. Modern and fossil ferns can be compared against one another to understand what insect interactions were present throughout geologic time, and the ways these interactions have either changed or remained constant. 

What data were used?: This study examined 17 types of damage (grouped into categories by the method used to cause the damage or by the area of the leaf affected; see Methods below) caused by insects, using both fossil ferns from multiple collection sites and modern ferns from a rainforest in southern Brazil. Ferns were chosen because, as opposed to other plant types, their broad leaves increase access for insect predation and modern broad-leafed ferns are very similar to some of their fossil relatives. Ferns became abundant in the Carboniferous (359.2–299 Mya). In the Carboniferous, records of arthropod (spider and insect) damage to plants also became more frequent. While insects are often not preserved with the fossil ferns, the types of damage that prehistoric insects caused are very similar to the damage types observed today, even if we don’t know if the types of insects that made the damage are or aren’t similar. Because fossil ferns are so similar to their living relatives, and because ferns are one of the first broad-leaved plants, scientists can use modern ferns as models to study the oldest plant-arthropod interactions. 

Methods: This study used an area of rainforest with high humidity, many fern species, and high fern density to study modern ferns. A census of the ferns present and any records of insect-fern interactions were collected over a transitional area from the lower broad-leaf forest to the upland grassland. The damage type, richness per leaf, and damage size were recorded using hand lenses, calipers, and macroscopic and microscopic photography. Functional feeding groups (FFG) were made to categorize the types of insect damage. Damage from egg-laying and traces were also recorded. Damage was recorded using a damage type guide that described 413 different damage types. This was compared to compiled fossil fern data from many sites. 

Results: Even with 413 pre-established damage types, one new damage type was discovered in this study. This new damage type is a sub-type of surface feeding that features a series of rounded damage marks that was observed in both modern ferns and in multiple fossil ferns. Some types of damage were found rarely in modern ferns, but never in fossil ferns (hole feeding – the creation of separate holes in the leaf tissue – and galling – the development of waxy or swollen layers). Margin feeding (consuming only the edges of a leaf) was found in both fossil and modern ferns and included the most common damage types (46% of the damage observed). Surface feeding (damaging but not completely breaking through the leaf tissue) was recorded on both fossil and modern ferns (10%). Some types were found in modern and fossil plants, but some types were only found in angiosperms (i.e., flowering plants) in the fossil record and not fossil ferns (piercing and sucking, small points of damage or swollen leaf sections, 15%, and mining, creating subsurface damage, 8%). 

A bar chart with the number of observed instances on the left y-axis to match the bars and the types of functional feeding groups on the x-axis. It is overlain by a line representing the cumulative percentage. From left to right: Margin feeding, 220 instances and 46% of the total. Piercing-and-sucking, 73 instances, the cumulative total 61%. Hole feeding, unlabeled but about 52 instances, 72% the cumulative total. Surface feeding, 50 instances and 83% of the cumulative total. Mining, unlabeled but around 40 instances, 91% of the cumulative total. Hole feeding, 34 instances, 98% of the cumulative total. Galling, nine instances, 100% of the cumulative total.
Figure: A bar chart of the recorded damage types by functional feeding group, showing the dominance of margin feeding in the modern ferns in the Sao Francisco de Paula National Forest, municipality of Sao Francisco de Paula, Rio Grande do Sul, southern Brazil.

Why is this study important?: This study showed that modern ferns can provide a better understanding of the marks that different insect feeding methods cause and of the fossil record of these marks on similar ferns. Researchers found that the levels of precipitation impacted the amount and types of fern-insect interactions in modern ferns. This means that studying modern ferns can create models for studying past environmental conditions using fossil fern data. Additionally, there are fossil and modern instances of insect interactions that show a specialized association with specific ferns.

Broader Implications beyond this study: The similar rates of predation by insects on both modern and fossil plants show that ferns were important to herbivorous (plant-eating) arthropods throughout history. All FFGs identified in the fossil record were found in modern ferns, so understanding interactions in modern environments can be used to determine the environmental conditions of different fossil assemblages, such as the projected precipitation level of their environment. The prevalence of fern-arthropod interactions throughout history means that it can be used to study changes in these fern-arthropod relationships in geologic time and we may be able to use them to model the influence of climate change. 

Citation: Cenci, R., & Horodyski, R. S. (2022). Fern-Arthropod Interactions from the Modern Upland Southeast Atlantic Rainforest Reveals Arthropod Damage Insights to Fossil Plant-Insect Interactions. Palaios, 37(7), 349–367.

How the ability to swim affects crinoid arm regrowth rates

Ability to Swim (Not Morphology or Environment) Explains Interspecific Differences in Crinoid Arm Regrowth

Biography: Delaney Young. She is an undergraduate student at the University of South Florida. She is currently working on her geology B.S. and will graduate in the summer of 2023. She then plans to obtain her geology M.S. starting in the Spring of 2024. 

Point of the Paper: The main point of the paper was to determine how arm regeneration rates of feather stars (occurring after injuries), a kind of crinoid, vary. Scientists examined the swimming ability of crinoid species, available food supply, severity of the injury, water temperature, number of regenerated arms, and the total number of arms in order to understand what drives differences in regeneration rates. The authors of this study found that the swimming crinoids regenerated arms up to three times faster than non-swimming crinoids. 

What data were used? 123 adult feather starts from eight different species were collected at depth in the ocean during two sessions (December 2016 – April 2017 and June – October 2018) in Malatapay, Negros Oriental, Philippines. The respective maximum arm length, the maximum number of arms, and the arm regeneration were compared. 

Methods. To study the rates of arm regeneration amongst swimming and non-swimming crinoids, the animals were collected at depths ranging from 5 to 35 meters. In the 2016 expedition, the individuals were captured and had a few arms removed by researchers. The researchers would pinch a feather star’s arm until it was voluntarily released as a means for amputation. The mechanism of voluntary release is used as protection for the crinoids. Researchers caused the crinoids to amputate an average of 3–5 arms, but some amputated up to ten arms. The animals were brought back to their original habitat after they amputated their arms and scientists measured their regrowth rates. In the 2018 expedition, the animals were caught and put in bamboo cages with mesh material on every side. The mesh allowed food particles to enter the cage, and the cage dimensions allowed the feather stars with the longest arms to extend them to the fullest. To mark a starting point for every animal, the measurements of maximum arm length and maximum arm number were taken for each feather star. The swimming or non-swimming ability of eight species from Malatapay, Negros Oriental, Philippines, was recorded and compared to the respective maximum arm length, the maximum number of arms, and the arm regeneration rate. 

Results. Of the eight tropical feather stars collected in Malatapay, Philippines, the rate of arm regeneration ranged from 0.29–1.01 mm/day (Figure 1). The species included two swimming and six non-swimming feather stars. The swimming feather stars experienced regeneration rates of 0.89–1.01 mm/day. The lower of the two rates (0.89 mm/day) was higher than the highest non-swimming arm regeneration rate. The impacts of total arm number and total regenerating arm number on rates of regeneration were larger in non-swimmers than in swimmers. There was no notable relationship between the number of removed arms and the rate of regrowth.

Image showing a graph of arm regeneration rates by color-coded species of feather star, with regenerating arm length on the y-axis and time on the x-axis. The image shows the arm length (millimeters) over time (days) and the mean regeneration rate of eight tropical feather stars. The six non-swimming feather stars of Family Comatulidae (Anneissia bennetti, Capillaster multiradiatus, Clarkcomanthus mirabilis, Comaster nobilis, Comatella nigra, Phanogenia gracilis) are shown in shades of blue. The one swimming family Mariametridae (Oxymetra cf. erinacea, Stephanometra indica) is shown in shades of red, orange, and yellow. The 95% confidence interval of each curve is shown in gray. Oxymetra cf. erinacea and Stephanometra indica show higher rates of growth.
Figure 1: Modified from Stevenson et al. (2022). This graph depicts the arm regeneration rates per species used in this study. Swimming crinoids showed higher rates of regeneration than non-swimming crinoids.

Why is this study important? The researchers found that swimming ability alone best explains the differences in arm regeneration rates amongst the swimming and non-swimming feather stars. Swimming ability in feather stars is thought to be an adaptation from the need to escape predators that live on the seafloor. Feather stars that lost limbs while escaping predators would need to regrow limbs quickly, as having missing limbs would negatively affect the animal’s ability to escape predators in the future. The rate of regeneration, while controlled primarily by swimming ability, is still affected by temperature, but to a lesser degree. In cold water, biological processes slow down, so crinoids in cooler waters with other forms of protection would have had better chances at survival. Scientists could relate this to the way that fossilized crinoids look to help understand the environment they lived in.

Broader implications. This paper can be related to paleontology because knowing if a crinoid was swimming or non-swimming can inform scientists of the likely regeneration rate of arms of organisms in the fossil record. Knowing these pieces of information can potentially give researchers more clues about the predation pressures that a fossil crinoid may have faced. We could hypothesize, for example, that crinoids in cooler waters may have had other forms of protection or retrieval, as a survival mechanism for the slowed biological processes caused by cooler water. The results of this paper could be compared to fossilized crinoids, so researchers can understand the ancient marine environments and ecology of crinoids. 

Citation: Stevenson, A., Corcora, T. C. Ó., Harley, C. D. G., & Baumiller, T. K. (2022). Ability to Swim (Not Morphology or Environment) Explains Interspecific Differences in Crinoid Arm Regrowth. Frontiers in Marine Science, 8. 

How evolutionary analysis results in bowfins show species diversity and lineages of a ‘living fossil’

Phylogenomic analysis of the bowfin (Amia calva) reveals unrecognized species diversity in a living fossil lineage

Summarized by Colton Conrad, a proud geology major at the University of South Florida. He is a senior who is as a geologist at ASRus (Aquifer Storage Recovery). Colton’s life revolves around fishing, hunting, exercising, and creating things out of metal. He is a great taxidermist and a fine creator of swords and shields.

Hypothesis: The purpose of this paper is to categorize bowfins into evolutionary groups by collecting samples to determine their diversity and evolutionary history.

Data: The data here is a collection from 94 individual bowfins found from the eastern United States. From phylogenetic analysis, which is a way of understanding species evolution from genetic data, the researchers involved with this project were able to find and sort out genetic variations in the DNA of the bowfin known as SNPs (single nucleotide polymer) to determine which species were most closely related. The sorting of SNPs is finding nucleotides that have changed but are still found in the population. They used specific lengths of DNA to define changes in the four nucleotides (adenine, cytosine, guanine, and thymine (A, C, G, and T)) in bowfin lineages and to find diversity among the population. 

Methods: Scientists ran the data using evolutionary tree computer programs to find the most supported configurations of bowfin relationships. Figure 1 shows the evolutionary reconstructions and the genomes from bowfins after comparing the phylogenetic population structure in bowfins. The researchers also ran a bootstrap analysis to test the likelihood of their results. Bootstrapping means that the analysis is re-run multiple times and the number of times the original answers are returned is counted as a percentage (e.g., the bootstrap support is 100% when the same tree structure is returned 100 times). 

Figure one is a circular chart showing the relations and patterns in the bowfin as an evolutionary tree. The four different colors red, blue, green, and yellow show the different species clusters. The larger dots colored green represents 100% bootstrapping, and the descending gray dots represent the percentage getting lower.


Results: The results of this study have revealed species diversity of bowfins populations (Figure 2). By analyzing SNP of the bowfins from all the locations the study revealed diversity in the population by showing the molecular and genetic data collected from these species can be traced back to two species of prehistoric fossil bowfins. This means that at least two bowfin species from this study are quite similar to the fossil forms and are considered ‘living fossils’

Why this study is important? This study is important because it gives us insight into what prehistoric fish species were like and how other species may have evolved to give us the diversity we see today. 

Broader Implications beyond this study: This study has added an deeper perspective to the DNA variations found in bowfin to help understand evolutionary adaptations found in soft ray fined fish, helping in our understanding of modern fish and terrestrial species. 

Figure two is a picture of the diversity of bowfins collected from the study. The bowfins in this figure vary in color based on environmental surroundings. Species A is a lighter brown color with reddish fins and a white belly. Species B is darker brown with a tan belly. Finally, species C is a blackish green color with a lime-colored belly. The fins, gills, and body types are all the same. The dorsal fins of the bowfin are a long soft ray design with a large, rounded tail. The pectoral fins are small compared to the body’s size and are rounded shape much like the other fins. This image shows what a bowfin looks like and gives a visual into the diversity of bowfin.

Citation: Wright, J., Bruce, S., Sinopoli, D., Palumbo, J., & Stewart, D. (2022). Phylogenomic analysis of the bowfin (Amia calva) reveals unrecognized species diversity in a living fossil lineage. Scientific Reports, 12, 1–10. 

Species distribution models and predictions tend to skew data trends and create bias predictions in biodiversity

Using species distribution models only may underestimate climate change impacts on future marine biodiversity

Summarized by Stephanie Sanders, a Geology major at the University of South Florida. She is currently a senior. Stephanie plans to attend Graduate school in paleobiology and once she graduates would like to work in the marine conservation field with a concentration in geographic information system (GIS) for mapping marine species. Outside of her studies, Stephanie enjoys the outdoors, drawing, and fostering kittens. 

Main point of paper: Anthropogenic (human-caused) climate change has affected a various number of species. We are seeing shifts in geological range, population counts, and environmental conditions. Species distribution has been affected due to these changes. Species distribution models (SDMs) are used to assess geological insight and predict distributions across different landscapes and time. SDMs use observations and estimates to make predictions on species occurrence and location. Many of these modeling software has ready-to-use generic software that is globally accessible. This ease of use has created databases that may not consider a wide range of important data sets that are crucial in interpreting the data. Some of these data sets include predation, species interaction, competition, and adaptation. This additional information that is excluded from many SDMs has created data bias. These biases include overestimating gains in data and underestimating losses in data. When only looking at the SDMs, we are losing vital data and creating data sets that may not accurately represent the species data. By only using SDMs data we may be overestimating the number of species present in certain times and locations which lead to distortion in data and predictions for future marine biodiversity. The consequences of this can be inadequate data for conservation efforts of species. The authors ask in this paper: Is generic SDM data enough to correctly predict future biodiversity or are additional data sets required to accurately represent species changes from anthropogenic climate change?

What data were used: Data from 100 species of various vertebrates and invertebrates from the Mediterranean Sea were used, downloaded from different online databases. Both a hybrid SDMs model of multispecies modeling and a hybrid OSMOSE-MED modeling (explained below), which allows for key life processes such as population growth, reproduction, and morality, were considered. 

Methods: The Mediterranean Sea served as a perfect spot for a comparison because it has a rare mix of biodiversity and is a global change hotspot. SDMs data is compared to other data modeling such as OSMOSE-MED. OSMOSE-MED allows for additional data sets to be considered (Figure 1). One hundred marine species such as fish, invertebrates and gastropods from the Mediterranean Sea, collected from the Global Biodiversity Information System (GBIF), the Ocean Biogeographical Information System (OBIS), the Food and Agriculture Organization’s Geonetwork Portal, and the FishMed database were compared with both SDMs modeling and OSMOSE-MED modeling. Two data sets were compared, a present day (2006-2013) and a future prediction (2071-2100). 

Results: Under the 100 species comparing SDMs to OSMOSE-MED, the following results were found: more species were found to have an increased geographical range in the SDMs model than the OSMOSE-MED model. Fewer species were found to have a decreased geographical range in the SDMs model than the OSMOSE-MED model, and three more species were projected to become extinct in the OSMOSE-MED model then the SDMs model. When using SDMs alone, a more optimistic projection of species distribution is observed. Without the inclusion of key life process data to predict future trends, the SDMs data alone could predict inaccurate data.  When we compare the two data sets, there is a clear discrepancy. SDM overestimates the positive data and underestimates the negative data. When looking to SDM alone, without the addition of extra relevant data sets, we can get a bias determination on future conservation data. This can include area prediction of where species are now inhabited or the number of species that are alive within a certain species. This can lead to improper protection areas or conservation efforts for a certain species. 

The figure above is a conceptual representation of a SDMs model showing the limited layers of species richness and dissimilarity index compared to the OSMOSE-MED model that allows for extra parameters to be added to fine tune the model to allow for more accurate representation of the model. OSMOSE-MED allows for more layers and is represented by a picture of those layers such as growth, morality, predation, and reproduction.
Conceptual representation of SDMs model vs. OSMOSE-MED model to accurately represent data and the projections that are compiled depending on the inclusion of extra data sets. OSMOSE-MED allows the addition of additional datasets that can more accurately represent the data of biodiversity that generic SDM data cannot.

Why is this study important?: Anthropogenic climate change is affecting a variety of species constantly. Many of these species will encounter a dramatic loss in population and even extinction. In order to put protective measures in place to help the longevity of threatened species, correct data is critical. If present and future studies are only utilizing generic models that don’t consider vital variables like predation, location predictions, and taxonomies. we may lose accurate calculations. The real-world implications of skewed data can be present in inaccurate locations of species, inaccurate population counts, and misinformation of vital data needed in the protection of threatened species. 

Broader Implications beyond this study: This specific study of SDMs vs. more in depth distribution models focuses on 100 species in the Mediterranean Sea. However, tracking anthropogenic climate change and the effects on species distribution is a global effort. In order to create accurate data sets, a global and local collaborative database is essential for comparative analysis of biodiversity. There are potentially major issues with inconsistent taxonomic standards applied when using SDMs data only. As the climate crisis begins to affect more species, additional data to create a global standard will be required. If we are to effectively create conservation efforts for threatened species, these standards need to be adapted and used regularly. 

Citation: Moullec, F., Barrier, N., Drira, S., Guilhaumon, F., Hattab, T., Peck, M. A., & Shin, Y.-J. (2022). Using species distribution models only may underestimate climate change impacts on future marine biodiversity. Ecological Modelling, 464, 109826. 

200-million-year-old fossil poop reveals ecosystem and critters of the past in India

Bone-bearing coprolites from the Upper Triassic of India: ichnotaxonomy, probable producers, and predator–prey relationships

Summarized by Sarah Arias Madrigal, a third-year geology student at the University of South Florida. She plans to one day become an earth science teacher. She enjoys dancing and playing spike ball in her free time.

Point of the paper: Coprolites (fossilized feces) from the Late Triassic (237–201 million years ago), from the Tiki Formation of India were studied to understand who made the feces, using ichnotaxonomy (i.e., classifying an animal based on trace fossil, in this case coprolites), their diet and feeding behavior, selection of prey, physiology, and their paleoecosystem (the prehistoric environment in which an ecological community lived).

What data were used?: Coprolites were collected near the village of Tiki, India. The most common body fossils in this area, among other animal bones, were an extinct group of amphibians called Metoposaurus. They were mostly aquatic with flattened heads). Fossils of this animal were found with a mix of other animal bones. 170 coprolites were examined, of which 30 were spiral coprolites (feces produced by prehistoric fish that pass through spiral intestines) and 140 were non-spiral coprolites.

Methods: The coprolites were examined both macroscopically (by hand) and under a microscope. Many coprolites were sectioned to examine the internal morphology (i.e., the structure, shape, form of an animal or plant). Thin sections were also made (thin slice of rock placed on glass) and examined using scanning electron microscopy (SEM).

Results: The external and internal details of the coprolites were important in identifying its producer. The composition of the coprolite and undigested pieces included in it directly reflected the food material the producer ate, which in turn helps in identifying the producer of the poop.. Fish scales were visible on the surface of the spiral coprolites, indicating that it ate fish. The components of the non-spiral coprolites varied drastically within each different specimen where undigested food, waste matter, gas escape structures and cracks were present. By knowing the body fossils present in the fossil beds of the Tiki Formation, scientists matched the coprolites to these fossils as being the probable poo producers. The spiral coprolites seemed to have come from elongate streamline fishes (called saurichthyids) and lungfishes, as well as extinct sharks. The turn counts (meaning, the number of spiral turns in the coprolite caused by the shape and muscle action of the intestine) of the spiral coprolites can tell scientists the depth of where each fish likely lived. Fish that lived in open ocean waters, nearer to the surface (pelagic), typically show higher turn counts. Fewer turn counts indicate the fish likely lived in deep waters at the sea bottom (benthic). However, using turn count is difficult since coprolites can be found broken or incomplete. The non-spiral coprolites seem to have come from tetrapods (four-limbed animals, like vertebrate land animals today). Specifically identifying the exact species to a non-spiral coprolite is difficult, as many different tetrapods can produce very similar coprolites. The best approach in identifying the coprolites produced by tetrapods was by looking at the cross-sectional geometry of a coprolite which is unique to an animal’s anal structure, also called a cloaca. Most of the non-spiral coprolites contained calcium phosphatic skeletal fragments, suggesting they were carnivorous. Calcium phosphate is what makes up the teeth and bones of all animals with backbones, or vertebrate. Carnivores eat vertebrate, therefore when remains of calcium phosphate fragments are found, this is indicative of an animal that eats other animals. Cross sectional geometries of the coprolites, along with the shape of the coprolites, whether the coprolite experienced shrinkage/cracking, and the state of the undigested pieces found in the coprolite allowed for conclusions of the animals that made the the non-spiral coprolites. These include prehistoric reptiles closely related to crocodilians, dinosaurs, and birds. 

The figure is sectioned into 7 microscopic images, labeled A through F, each showing different types of inclusions in spiral coprolite samples. Images A,B, and C depict fish scales imbedded within the surface of an orange-colored coprolite. This reveals the diet of the producer of this coprolite as well as their role within the prehistoric ecosystem. Image D depicts a black and white SEM image with a circled cluster of fish scales lined up parallel to each other. This a characteristic of spiral coprolites, where inclusions are usually aligned parallel to coprolite layers. Image E shows a black and white SEM image of a coprolite with arrows pointing at 2 mucosal folds. The folds are notable as sectional ridges running parallel to each other within the coprolite. Image F shows the last black and white SEM image with an arrow pointing to a singular tooth imbedded within a spiral coprolite. This is another example of how inclusions reflect the food material the producer ate and its diet. The last image has arrows pointing towards skeletal fragments and remains imbedded within an orangish coprolite. Scale bars represent 0.5 millimeters for A-C, 500 micrometers for D, 1 milliliter for E,G and 100 micrometers for F.
Different types of inclusions in samples of spiral coprolites. A–C, clusters of fish scales on the external surface of coprolite. D–F, SEM images of inclusions: D, cluster of fish scales (circled); E, mucosal folds (arrows), which are folds within the lining of an animal’s intestine with is reflected on a coprolite. ; F, an isolated tooth (arrow); G, skeletal remains (arrows) on the external surface. Fish scales and bones in coprolite reveal the coprolite producers’ diet and role in the food chain. Scale bars represent 0.5 millimeters for A-C, 500 micrometers for D, 1 milliliter for E,G and 100 micrometers for F.

Why is this study important?: Studying extinct fish, reptile, and amphibian coprolites of the Triassic Tiki Formation further reveals the intestinal and anal structure of these animals, each animals’ digestive strategy for survival, feeding behavior, and habitat they likely lived in. Undigested food remains in the coprolites also provide a look at the food chain and predator-prey interaction at that time. Without the soft tissue preservation of these prehistoric animals, coprolites allow for a reconstruction of the intestinal structures of aquatic animals. 

Broader Implications beyond this study: Studying older coprolites can reveal the time in which fish evolved a spiral intestinal valve, and what factors, such as palaeoecological, paleoclimatic, etc. that drove particular fish species to develop and retain it to this day.

Citation: Rakshit, Ray, S., & Marchetti, L. (2022). Bone‐bearing coprolites from the Upper Triassic of India: ichnotaxonomy, probable producers and predator–prey relationships. Papers in Palaeontology8(1). 

Comparing Late Pleistocene hyena species with living species by looking at the wear and tear of their teeth

Diet and ecological niches of the Late Pleistocene hyenas Crocuta spelaea and C. ultima ussurica based on a study of tooth microwear

Summarized by Saddie Fortner,  a senior geology major at The University of South Florida. She plans to attend graduate school in volcanology and pursue her PhD afterwards. She plans to work as a professor at a university and continue doing research. Her hobbies include playing video games, painting her nails, and crocheting.              

What was the hypothesis being tested (if no hypothesis, what was the question or point of the paper)? The purpose of this study was to compare the feeding habits two extinct species of hyenas, Crocuta spelaea and C. ultima ussurica, by comparing the scratches and pits on their fossilized teeth, also called microwear. Environmental roles, such as predator and scavenger, were determined. Feeding differences of juveniles and adults were also tested using tooth microwear.

What data were used?:  Tooth specimens of Crocuta spelaea were collected from Crimea and eastern Kazakhstan (Figure 1). Tooth specimens of C. ultima ussurica were collected from eastern Russia. Teeth from the living species of Crocuta were used as a comparison. Bones of hyenas’ prey were collected from the caves.                                                                      

Methods: Features such as small and large pits, scratches, gouges, and puncture pits, also called microwear, were counted. The two extinct species’ teeth were compared to extant species’ teeth to determine their feeding habits and environmental roles. This was done by comparing the amount of microwear on the extant hyena’s teeth to the extinct hyena’s teeth. Since the feeding habits and environmental roles of living hyenas is known, the fossil teeth that are similar to the extant hyena’s teeth likely would have had similar feeding habits and environmental roles. Bones of the hyenas’ prey were also collected, as they contained teeth marks from gnawing juveniles and evidence of ingestion by the hyenas.

Results: The microwear patterns on the teeth of Crocuta spelaea and C. ultima ussurica suggest that the extinct hyena species had a similar diet and role in the environment to the extant spotted hyenas. The teeth from Crimea and Russia contained a high number of gouges, small pits, and coarse scratches, which is similar to the extant spotted hyenas who are known for cracking the bones of their prey in extreme ways. The number of scratches found on the teeth from Russia exceed those from the extant spotted hyena and more closely resemble those of a present-day lion. This is supported by the long length of the upper molar found in Russia. The two extinct species do not have similar microwear to the two extant hyenas, striped hyenas and brown hyenas. This is because the striped hyenas live on a diet of meat and bone, but less bone than the spotted hyena. The brown hyena ingests not only meat and bone, but also fruit. The adult and juvenile microwear patterns of all the collected fossil teeth had similar quantities of pits and scratches. The only difference was the absence of cross scratches on the juvenile teeth. This could be due to the greater proportion of meat to bone that juveniles would have consumed compared to adults. Conclusive results could not be drawn due to the small quantity of juvenile fossil samples. The specimens from eastern Kazakhstan were not included in this assessment due to the small number of specimens.

There are two close-up pictures of fossilized teeth. Each picture shows an area 2 mm long and 1.8 mm high. The top picture, A, is of a Crocuta spelaea tooth. The tooth has many coarse scratches of different lengths. The coarse scratches are going diagonally from the top right to the bottom left. There are two gouges. One is at the top left and the other is at the bottom right of the picture. Both gouges are about 1 mm in length. The gouges are in the same direction as the coarse scratches, but are steeper. The bottom picture, B, is of a Crocuta ussurica tooth. The tooth has many coarse scratches. The scratches have lengths ranging from .1 mm to 1.8 mm and no shared orientation. This tooth contains many small pits. The pits are sub-circular and have diameters ranging from .1 mm to .05 mm.
Figure 1: Close-up image of a tooth from (A) Crocuta spelaea and (B) Crocuta ussurica. The Crocuta spelaea tooth shows many scratches and some gouges. The Crocuta ussurica tooth shows many coarse scratches and small pits.

Why is this study important?:  The study shows how we can recreate the behavior of extinct hyenas by looking at something as simple as teeth. By comparing the tooth wear of extinct hyenas to extant hyenas, whose diet and behavior we know, we can determine what the extinct hyenas ate, how they ate, and how they fit into the environment in which they lived. The study also found bones of the Late Pleistocene hyenas’ prey in the caves where the teeth were found. This provides further information about the type of wildlife that was found in their environments, which could be used to determine many other species’ historical range. A species’ historical range is the area in which a species used to live. An example of this would be the lion. The lion’s historical range was Africa, southern Europe, and western Asia. The lion’s current range is only a small part of Africa.

Broader Implications beyond this study: Tooth microwear is not limited to hyenas. The study can be applied to many other carnivorous species such as the famous saber-toothed cats, also known as Smilodon, or the lesser-known American cheetah that lived during the Pleistocene. It might be interesting to see how the American cheetah’s and the Modern cougar’s tooth microwear differ from each other, considering the two species are closely related. Furthermore, this study could be adapted to herbivores to study their diets and the vegetation that occurred during their time.

Citation: Rivals, F., Baryshnikov, G., Prilepskaya, N., & Belyaev, R. (2022). Diet and ecological niches of the Late Pleistocene hyenas Crocuta spelaea and C. ultima ussurica based on a study of tooth microwear. ScienceDirect. 601, p.111125.


Morphological study of the ancient shark Cretodus crassidens

Morphology and paleobiology of the Late Cretaceous large-sized shark Cretodus crassidens (Dixon, 1850) (Neoselachii; Lamniformes)

Summarized by Mila Carter, a senior at the University of South Florida, majoring in Geology with a minor in Geographic Information Systems. After graduation, Mila plans to attend grad school to study climate science and would like to eventually work as a research technician. Some of Mila’s hobbies include going to the beach, hiking outdoors, reading, and spending time with friends and family. 

What was the hypothesis being tested (if no hypothesis, what was the question or point of the paper)?: The point of this paper was to learn more about the growth and lifestyle of newly-discovered ancient shark species Cretodus crassidens.

What data were used?: The data that was used consisted of a partial skeleton (including 101 teeth, 86 vertebral centra, and pieces of mineralized skull cartilage) found in an 85 million year old rock formation in Veneto, Italy called the Scaglia Rossa (a limestone rock formation from the Late Cretaceous), and a deformed tooth set, one vertebral centrum, a disarticulate set of teeth, and many single teeth found in a rock formation in southeast England called the Chalk Group (a limestone formation from the Upper Cretaceous).

Methods: Researchers took measurements of the specimens using photographs imported into a software called ImageJ. To estimate the original number of vertebral centra the shark had, a mathematical analysis method called a ‘least square linear regression’ was used. The size of the teeth was used as a parameter to determine the total length of the shark. The growth pattern of the shark was assessed using a growth function that models average length of the specimen versus its age, known as the von Bertalanffy growth function. The vertebrae were cut in half to observe the growth rings of the shark (approximately one ring of growth per year) to determine the shark’s age at death, which was 23 years (the average lifespan of this shark species was 64 years).

Results: The shark was determined to be larger in size (9 to 11 meters in length) and macropredatory, meaning it was a relatively large carnivore. Based on its length, this species of shark falls into a category of gigantic fish, as it is more than 6 meters in length. Its calculated adult size of 9 to 11 meters makes it more similar in size to Otodus (an extinct giant mackerel shark from the Cretaceous). The fossils suggest that the shark had a wide mouth and head along with a stout body. The shark also likely swam at moderate speeds and lived near the shore based on its teeth measurements (figure 1). We know this as scientists have found that there is a correlation between the tooth measurements of existing fish and their tendencies to be fast or slow swimming and their tendencies to live nearshore or offshore. This same principle can be applied to extinct fish to learn about their lifestyle, as it was in this case. Based on the fossils found in Veneto, Italy, the shark was found to have fed on large marine turtles. Along with the teeth and vertebrare of this shark being preserved in life position, there were also broken pieces of turtle shell deposited in a cluster next to the aligned vertebrae (where the shark’s stomach once was), leading the researchers to assume that the turtle was the last meal of the shark and was in its stomach when it died.

This graph shows mean ridge distance of shark teeth (measured in micrometers) plotted on the x-axis on a scale of 0 to 135 versus mean scale crown width of shark teeth (measured in micrometers) plotted on the y-axis on a scale of 0 to 675. Known shark species are plotted as points on this graph based on their tooth measurements. These points are grouped into two categories, fast swimming pelagic taxa and moderate swimming and nearshore taxa. The shark species points that fall toward the left side of the graph are grouped into the fast-swimming pelagic taxa category, and the shark species that fall to the right side of the graph are grouped into the moderate swimming and nearshore taxa category. Cretodus crassidens falls into the moderate swimming and nearshore taxa based on the data analysis conducted in this study.
Figure 1: This is a graph showing the mean ridge distance of shark teeth versus the mean scale crown width of shark teeth. The mean ridge distance refers to the average length of a particular feature on the tooth called the ridge, and the mean scale crown width refers to the average width from one point to another of a particular part of the tooth called the crown. Different shark species are plotted on this graph based on their tooth measurements. The light gray group is labeled as ‘fast swimming pelagic taxa’, meaning any shark in this group is known to be fast swimming and lived in the open ocean. The dark gray group is labeled as ‘moderate swimming and nearshore taxa’, meaning any shark in this group is known to swim at a moderate speed and live near the shore. Based on the measurements taken of the Cretodus crassidens teeth, this species was determined to fall into the ‘moderate swimming and nearshore taxa’ category.

Why is this study important?: Prior to this study, the information that scientists had about the genus Cretodus was mostly based on isolated tooth fossils (fossil shark teeth that were found on their own with no other accompanying remains from the shark). Within the genus Cretodus, there are five species, and among these five species, only one (Cretodus houghtonorum) has evidence of a partial skeleton. For an almost complete skeleton to be found for Cretodus crassidens is a great discovery for scientists wishing to find out more about this genus and this species.

Broader implications beyond this study: This study helps us to more thoroughly understand evolutionary patterns as we now know more about the morphology and lifestyle of an extinct species of shark. From this information we can perhaps derive why it became extinct and draw connections to the environmental and ecological conditions in the oceans at that time. Understanding the evolutionary history of large oceanic predators is critical today, especially, because many sharks are threatened due to human activity today.  

Citation: Amalfitano, J., Dalla Vecchia, F. M., Carnevale, G., Fornaciari, E., Roghi, G., & Giusberti, L. (2022). Morphology and paleobiology of the late cretaceous large-sized shark Cretodus Crassidens (Dixon, 1850) (Neoselachii; Lamniformes). Journal of Paleontology, 96, 1166–1188. 

Reviewing the relationship between the molars of small mammals and climate change during the Paleocene-Eocene transition (~55.5 million years ago)

Evaluating the responses of three closely related small mammal lineages to climate change across the Paleocene–Eocene thermal maximum

Summarized by Matthew Eisenson, a geology major at the University of South Florida (USF) at the Tampa campus. Currently, he is in his third year. He plans on attending graduate school to earn his PhD in volcanic hazards. From that, he plans on working on different volcanoes and examining their hazards so that he can help the people in those areas during times of natural disasters caused by volcanic eruptions. He may potentially become a university professor after working in the field for a few years. When he is not studying for school, he likes to play tabletop roleplaying games with people or play games with friends.

What was the hypothesis being tested? The main hypothesis that was being tested in this study was whether abiotic- climate change (driven (i.e., nonliving variables like temperature, precipitation, salinity, and humidity) can be traced in the dental molars of three mammalian species: cf. Colpocherus sp , Macrocranion junnei, and Talpavoides dartoni. These are all small mammals that were rodent-like in appearance. 

What data was used? The data used in this study were fossils of the three most common species of stem erinaceids (the group containing hedgehogs) that were alive during the Paleocene-Eocene Thermal Maximum (PETM), listed above. As the name suggests. The Paleocene-Eocene Thermal Maximum, the climate warmed drastically on Earth. From these, this study looked at the teeth (molars) of these animals. They got the specimens used for this experiment from the Florida Museum of Natural History (FMNH), Gainesville, FL., and National Museum of Natural History (USNM), Washington, D.C. These teeth were taken from a range of time surrounding the PETM: early, mid, late, and post. The three teeth belonging to each species can be seen in Figure 1. 

Methods: This study used several methods to study changes in the molars of the listed species through time. One method used was done by measuring the size change of the molars. This was done by calculating the log transformed crown area (length × width). The other strategy used was measuring the shape change of the molars. This was done by looking at three-dimensional model analysis of the shape change with dental topographic metrics and 3D geometric morphometrics. The shape change was also measured by univariate parameters (or based on one attribute) created from the linear and angular measurements (Figure 1).

Results: This experiment had results that neither supported the hypothesis that abiotic change as a direct driver of altered dental morphology or the null hypothesis that biotic change as a direct driver of altered dental morphology. This came as a surprise, as previous studies have shown that molar teeth can change due to a changing climate. Much of the data was limited by sample size, making most seen changes fall within an error range (i.e., that the size changes are not significant enough to indicate true change). Even though there were changing climates during this period, there were no significant changes in these animals’ molars. 

The figure above shows the way the researchers broke down the measurements for the molars. Shown are three views of the tooth with the measurements marked on them (A= top down view; B= side view; C= angled view). First, they measured the crown area by doing the natural log of the length times the width. Next was the relative talonid by dividing the width by the length. Next, they measured the relative metaconid length by dividing the metaconid length by the length. They also measured the relative metaconid-entoconid intercusp by dividing the metaconid-entoconid intercusp by the length. They measured the relative hypoconid−hypoconulid intercusp distance by dividing the hypoconid−hypoconulid intercusp distance by the length. Finally, they measured the relative trigonid height by diving the trigonid height by the length.
Figure 1. This image shows how the researchers did their linear and angular measurements to get their univariate parameters. This was done by measuring several parts of each molar and putting it through a code to get a univariate parameter that could be used. Each tooth was measured 3 separate times. The acronyms are CA, crown area; HHID, hypoconid−hypoconulid intercusp distance; L, length; MEID, metaconid−entoconid intercusp distance; ML, metaconid length; R-, relative; TH, trigonid height; TW, talonid width; W, width. A= top down view; B= side view; C= angled view

Why is this study important:  This study is important to look at because it showed contradicting data from what has been found before. As stated, these species seemed to have been minimally affected (at least in their molar shape and size) by climate change, while other studies on other species have shown far larger effects from climate change. More thought, analysis, and retesting is needed in this area for a more correct answer to be brought forth.

Broader Implications beyond this study?  The broader implications for this study all relate to climate change. As this study looks at relating certain characteristics across time and climate change, there is an implication about using it to better understand our geologic past, by using data gathered here to correlate molars with climate change. Another implication is looking at current climate change and how mammals will/are responding to it. Looking at how mammals may respond to the current global climate change can give us a lot of information. We can also see how past events predict what are seeing with current climate change and use that information for conservation purposes. 

Citation: Vitek, N. S., Morse, P. E., Boyer, D. M., Strait, S. G., & Bloch, J. I. (2021). Evaluating the responses of three closely related small mammal lineages to climate change across the Paleocene–Eocene thermal maximum. Paleobiology, 47(3), 464-486.

New Fossil Evidence Reveals How Killer Whale And Other Hunting Whales’ Feeding Preferences Evolved

The origins of the killer whale ecomorph

Summarized by Lara Novalvos, a senior at the University of South Florida, majoring in Marine Biology and with a double minor in Geology and Environmental Science and Policy. After graduation, she expects to earn a Ph.D. in Oceanography. In her free time, she enjoys traveling, reading, and working out.

What was the hypothesis being tested: Scientists in this study are testing the hypothesis that hunting mammals is a trait that evolved more than once in whales and dolphins. The killer whale (Orcinus orca) and the false killer whale -a species of dolphin that resembles killer whales in feeding habits- (Pseudorca crassidens) are the only cetaceans (the group that contains whales and dolphins) that hunt marine mammals, a trait that was thought to have evolved once.

What data were used?:  A cetacean partial skeleton fossil found on Rhodes, Greece. The fossil skeleton preserved (among other bones) was its mandible (lower jaw), some teeth, and otoliths (“earstones”) belonging to fish that were eaten as the whale’s last meal.

Methods:  Morphological traits of the discovered species Rododelphis stamatiadisi were compared to those of other extinct and extant cetaceans (especially teeth count, size, and shape and upper jaw size) to build and infer an evolutionary tree that shows how the killer whale, the false killer whale, and the newly discovered Rododelphis stamatiadisi are related.

ResultsRododelphis stamatiadisi, the species found on the beach in Greece, is an extinct whale from the Pleistocene (2.59 million years ago – 11,700 years ago) that fed on fish. The results of the evolutionary (phylogenetic) analysis indicates that Rododelphis’ skull morphology is more closely related to that of false killer whales, placing them as sister taxa on the tree. However, another fish-feeding whale fossil previously discovered, Orcinus citoniensis, is considered killer whales’ closest relative. Researchers analyzed the teeth, jaws, and size of many cetaceans, extinct and extant, and concluded that delphinids (small whales with teeth such as dolphins, killer whales, pilot whales, and close relatives) evolved in six different lineages, half of them having many small teeth, and three of them having bigger, fewer teeth. From one of the lineages with few big teeth, killer whales evolved; false killer whales also appeared in a lineage of whales with big few teeth but not from the same one killer whales evolved.. These results indicate that the trait of feeding on other marine mammals appeared twice in the evolutionary history of whales, rather than having a single origin.

The figure above displays different delphinid species and its relationship based on morphological and molecular analysis. The phylogenetic tree shows a group of branches towards the middle of the tree colored in orange; these represent the lineage where the present killer whale evolved and its closest known ancestors. Towards the bottom of the tree, branches containing today’s false killer whale and its known lineage are colored in purple. The most closely related species to Orcinus orca is Orcinus citoniensis, while the most closely related species to Pseudorca crassidens is the recently discovered Rododelphis stamatiadisi; both extinct species fed on fish, whereas both killer whales species feed on other mammals, suggesting that the trait evolved in two separate instances.
The evolutionary tree containing extant killer whale and false killer whale. Orange branches show species in the killer whale’s lineage; purple branches show the false killer whale’s ancestors and lineage. Killer whales belong to a lineage that evolved before the false killer whale’s lineage did. Rododelphis stamatiadisi is more closely related to false killer whales than it is to killer whales; moreover, false killer whales are more closely related to Rododelphis stamatiadisi than to killer whales.

Why is this study important?: This study provided an opportunity to revise the evolutionary groups of the whale group. It focused on how different feeding habits evolved within the group, allowing for a deeper understanding on how the different species adapt to new environments, food abundance, or even climate change. Whaling has caused killer whales to switch to smaller prey, allowing us to observe how these whales adapt their feeding habits to different food abundance.

Broader Implications beyond this study: Research suggests that the coexistence of many large predators lead to the selection for even larger creatures; this study suggests that marine mammal predation can be correlated with whale’s gigantism. Both Orcinus orca and Pseudorca crassidens feed on marine mammals, but their most common ancestors did not.  Although the exact origin of why whales became so large is still unknown, it has been hypothesized that gigantism drove these two killer whales to develop their particular feeding preference.

Citation: Bianucci, Geisler, J. H., Citron, S., & Collareta, A. (2022). The origins of the killer whale ecomorph. Current Biology, 32(8), 1843–1851.e2.  

The diversity of 85-million-year-old European freshwater snails was influenced by global climate change

Onset of Late Cretaceous diversification in Europe’s freshwater gastropod fauna links to global climatic and biotic events

Summarized by Jordan Orton. Jordan Orton is a geology major at the University of South Florida. Currently, he is a senior. He plans to work for the water management district to help protect and preserve the aquifer system to ensure we have plenty of safe water to drink and use. When he’s not studying geology, he loves to watch movies, garden, play board games, and go on little adventures. 

What was the hypothesis being tested? The hypothesis of this paper is to determine which factors influenced the rate of speciation (the rate that new distinct species evolve from a common ancestor) to increase so rapidly. Was it because of annual precipitation, average temperature, geographic distance, or continental area (which is determined by the sea level)?

What data were used? Data for this study was collected previously by the same authors and includes estimates of temperature, precipitation, and other variables by geographic location. Their data set also included taxonomic records of 3,122 species of snails represented in this fossil record.

Methods: They compared the results of a birth-death model (a statistical model of how the population of a species changes over time) and a multivariate birth-death analysis (a more complex statistical model to estimate population changes over time that takes into account several contributing factors) with shifts from a 10-million-year timeframe before the peak in speciation of snails to a 10-million-year timeframe after the peak in speciation of snails in order to determine which of the four variables in the hypothesis most affected the rate of speciation.

Results: The researchers analyzed four factors that may have contributed the most to this increase in diversity of snails: annual precipitation, mean annual temperature, geographic distance, and continental area (which is a function of sea level rise and fall). According to the results of the analyses and models, the factors that had the most influence for so many species of snails evolving was a reduction in continental area (i.e., sea level rise) and an increase in geographic distance. 

A reduction in continental area means that sea levels rose and flooded parts of the continent, creating new niche habitats that are brackish (slightly saline) to freshwater. This allows species that can tolerate the less salty waters have a place to flourish and escape predation from marine organisms. This coincided with the Cretaceous Terrestrial Revolution, a bloom in diversity of flowering plant life, and high global water surface temperatures, which also increased marine animal diversity. The creation of these new habitats allowed multiple species to develop and feed from varying types of new flowering plants that were also diversifying in the new habitats. Over time, these organisms evolved into new species that specialized which plants they consumed (similar to the example of Darwin’s finches). The secondary factor that allowed for this increase in diversity of snails is that there was a greater distance between continents, so there was more habitable area for the snails to spread out into. Because the snails venture out further apart, they don’t have the opportunity to intermingle with each other as much, which causes more species to develop

The rate of extinction of snails was consistent through each of these 10-million-year windows, so the rate of extinction wasn’t particularly affected by these four factors. It is likely that there was a decline in the rate of speciation from 85 Mya to 80 Mya due to interspecies competition. Interspecies competition is when there are too many different species competing for a limited resource, so there is a decline in population.

This figure consists of four bar graphs: speciation rate from 95-85 Mya, speciation rate from 85-75 Mya, extinction rate from 95-85 Mya, and extinction rate from 85-75 Mya. The x axis is a range from -7.5 to 2.5 and the y-axis is the time period for that graph. Each graph has 5 factors that are correlated to rate of speciation or extinction: diversity, annual precipitation, mean annual temperature, geographic distance, and continental area. The factors that correlate most with increasing the rate of diversity from 95-85 Mya are an increase in geographic distance and a decrease in continental area, the factor that correlates most with the decline of the rate of speciation from 85-75 Mya is diversity. The rate of extinction from 95-85 Mya was not correlated to any of the factors, and the rate of extinction from 85-75 Mya was correlated to a decrease in continental area. The other variables: annual precipitation and mean annual temperature had a small effect on the data.
This figure shows the correlation strength of the four variables from the hypothesis plus the effect diversity has on the rate of speciation and extinction in the time period 95-85 Mya and 85-75 Mya. The factors that correlate most with influencing the rate of speciation in the period of 95-85 Mya are a decrease in continental area and an increase in geographic distance, while the factor that correlates most to influencing the rate of speciation in the period of 85-75 Mya was diversity. The rate of extinction was not heavily influenced by any of these variables from 95-85 Mya, but the drop in extinction rate from 85-75 Mya was influenced by a decrease in continental area.

Why is this study important? This study is important because there hasn’t been much research into the factors that drove the diversity of species of European freshwater snails; the marine and terrestrial snails are more studied and better understood.

Broader Implications beyond this study: Sea levels and average annual temperature are rising today. If we want to understand what sort of impact human activity is having on the increasing and decreasing rates of speciation of snails, we need to understand how they were affected by the paleoclimate (historical climate). We need to see how snails reacted to these conditions in the past to have a baseline that we can compare to how they react now to the same conditions (which are now being driven by humans).  Scientists can then determine how human activity (habitat destruction, nutrification, etc.) is affecting their rates of speciation. 

Citation: Neubauer, T. A., & Harzhauser, M. (2022). Onset of late cretaceous diversification in Europe’s freshwater gastropod fauna links to global climatic and biotic events. Scientific Reports, 12, 1–6.