Climate & Paleo News

Here we will dissect recent publications in the fields of climate and evolution. Our goal is to provide a logical narrative while also picking out the data and importance of each study.

85–75 Million Year Old fossil helps detail evolutionary history of bird skulls and brains

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Cretaceous bird from Brazil informs the evolution of the avian skull and brain

by: Luis M. Chiappel, Guillermo Navalón, Agustín G. Martinelli, Ismar de Souza Carvalho, Rodrigo Miloni Santucci, Yun-Hsin Wu1 & Daniel J. Field

Summarized by Jordyn Dutcher. Jordyn lives in Binghamton, NY, and attends Binghamton University seeking a B.S in Biology. Jordyn works for a local news station editing videos and is particularly interested in science communications. When she’s not out in the woods hiking, she can often be found attending local music shows. 

What data was used? Researchers analyzed the skull of an avian (bird) dinosaur found in a bonebed within São Paulo State in southeastern Brazil and dated to be from the Mesozoic Era in the Cretaceous Period (85–75 mya). Additional skull data (i.e. the shapes and proportions of the skulls), from previous studies, of other birds both from the distant past and modern day was used. 

What was the hypothesis being tested? Researchers used a newly discovered fossil, Navaornis hestiae gen. et sp. nov., to help fill the gap of evolution between the Archaeopteryx (one of the oldest known ancestors of modern birds) and closer known ancestors of modern day birds. More specifically, they were aiming to find the origin of derived skulls and brains which currently exist in birds of today but were not existent in Archaeopteryx.  

Methods: Researchers used the newly discovered bird fossil skull and compared its features to those found both in modern and past avian skulls. This was done by scanning the fossil and then digitally reconstructing the skull using a 3D-imaging software (Blender and VGStudioMax). The researchers analyzed the reconstructed skull of the newly discovered fossilagainst other 3D reconstructions (obtained from CT scans and recreations done in previous studies) of 228 other avian skulls, including both those currently living and older ancestors such as the Archaeopteryx, and plotted them based on their differences and similarities using Principal Component Analysis (PCA) (Fig. 1) which is a commonly used analytical method which takes all the collected measurements and condenses them plot on a 2D graph for comparison amongst different specimens, with the further the plot points are the more they differ in their structure. Using an adapted method from previous studies, the scientists defined “landmark” points of significance in which these fossils either varied or shared similarities which were striking, such as marking various points within the brain cavity of the skull and parts of the beak/rostrum; essentially, all of the landmarks were placed on the same feature on each skull, to capture the variation between the studied specimens in those features. The analysis of the different shapes and features of these skulls allowed the researchers to draw connections about how evolution occurred between these different species and their ancestors based on the full range of variation in their skull shape. 

In this figure, we see a graph depicting a Principal Component Analysis with PC1 and PC3 on the X and Y axis, respectively. This represents degrees of similarity between the inner structure of the skull including the general brain shape of the different species on the graph. Specifically on the Y-axis (PC3) the top represents skulls which had more of an upward tilt in the backside of the skull where the brain resides, with lower points showing more of a downward tilt. On the X-axis (PC1) those to the left had more sleeker/stretched inner skulls in opposition to those which lay on the right which were far less sleek and were in general more circular compared to the more oval like shape on the left. In the middle of this graph we see Navaornis with two clusterings of species to its left and right. On the left of Navaornis are primarily various non-avian theropods (ancestor group of Archaeopteryx, including species such as Citipati, Zanabazar, and an unnamed troodontid) alongside the alligator and Archaeopteryx, whereas on the right are various modern bird species such as Apteryx, Nestor, Chordeiles, Gavia, and Anas.
This figure shows a Principal Component Analysis of the skulls of the new bird fossil, Navaornis, as well as the modern birds and ancestral birds/related species such as the Archaeopteryx and alligator. This graph plots all the variation between the skulls on a 2D axis, so that it is easy to visualize how different the studied skulls are; specifically on each axis are the collected measurements of the specimens condensed on a 2D graph for comparison amongst different them, with the distance between them showing how much they they differ in their structure. On this diagram you can see how these different species varied in the shape of their skulls on a scale of comparative difference with a set baseline, the main characteristic being compared in this graph is the inner structure/size of the skulls. In this diagram Navaornis stands almost squarely in the middle between the modern day birds and their ancestors, showing how it is intermediate in terms of its anatomical features-specifically the two clusters being on the right primarily various non-avian theropods (ancestor group of Archaeopteryx) alongside the alligator and Archaeopteryx, whereas on the right are various modern bird species. 

Results: The discovered fossil plotted differently enough to be named a new genus and species by the researchers; Navaornis hestiae, was found to be a toothless bird belonging to the enantiornithine group, which is an extinct group of most-often toothed birds abundant during the Mesozoic Era which did not give rise to modern birds. This fossil represents one of the first well-preserved skulls found in the enantiornithine group. The skull shape of Navaornis is described by the researchers as an intermediate mix in structure between modern birds and their oldest known ancestor, the Archeopteryx, falling in the middle between the size and shape of the inner ear and brains of these two groups (Fig. 1). However, the enantiornithine group, the group the new fossil belongs to, aren’t genetic ancestors of modern birds and instead co-evolved alongside the group which would lead to modern birds before going extinct.  This means that these similarities were likely convergent and evolved separately in these two groups. This intermediate mixing of prehistoric and modern birds skull structure seen in Navaornis supports the idea that the different parts of the skull were evolving separately and at different rates. 

Why is this study important? This study is important as it defines the new genus and species Navaornis hestiae. which helps to detail the evolutionary history of the brain/skulls of the wildly diverse modern birds of today and their long distant ancestors/relatives. Additionally, this study supported “modular evolution” which is the idea that different anatomical regions of an individual can grow at different rates, which is exactly what was seen in the mixing of more prehistoric and modern features of the Navaornis skull.

Broader Implications beyond this study: Scientists hypothesize that this mixing of features is likely due to some form of evolutionary pressures shaped through their life habits (e.g. feeding, etc.). Prior to the splitting of the two groups, a disparity (difference)  between them existed with the enantiornithine group having significantly narrower skulls compared to the wider and more stout skull seen in the group leading to modern birds. Further research into this topic may be able to help determine what sort of evolutionary pressure may have contributed to this mixing of structures within the enantiornithine group and the group leading to modern birds.

Citation: Chiappe, L. M., Navalón, G., Martinelli, A. G., Carvalho, I. de S., Miloni Santucci, R., Wu, Y.-H., & Field, D. J. (2024). Cretaceous bird from Brazil informs the evolution of the avian skull and brain. Nature, 635(8038), 376–381. https://doi.org/10.1038/s41586-024-08114-4 

Terrestrial ecosystem recovery after the Permian–Triassic mass extinction 251 million years ago

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Refigium amidst ruins: Unearthing the lost flora that escaped the end-Permian mass extinction

by: Huiping Peng, Wan Yang, Mingli Wan, Jun Liu, and Feng Liu

Summarized by: Jenna Allen, an environmental science and biology undergraduate student at Binghamton University. Currently, she is experiencing existential dread regarding her future but enjoys reading and painting in her free time.

What data were used? A team of scientists collected rock samples from the Permian–Triassic Boundary, 251.94 to 251.88 million years ago (Ma), of the South Taodonggou Section in the Xinjiang Province of northwestern China for pollen and spore fossils, also known as palynomorph fossils. Unlike many other organisms, plants do not have bones or teeth, which means they are less likely to fossilize. Fortunately, pollen produced by plants have hard outer layers that increase their preservation potential. Scientists can identify and match the pollen and spores present in a given rock layer to specific plants. Using that information, as well as the type of rock the fossils are found in, they can reconstruct environments from hundreds of millions of years ago. Plant and animal fossils, however rare, are still useful and were collected whenever possible in this study for a total of 129 palynomorph samples, 39 fossilized tree trunks, and 20 animal fossils.

What was the goal of the paper? The Permian–Triassic mass extinction was the worst of the five major mass extinctions in Earth’s history, with 80% of known species going extinct. With this study, scientists aimed to better understand the effect this extinction event had on terrestrial plant communities. They looked at (a) the response of terrestrial plants to changing environmental conditions, (b) the role of isolated plant populations, also known as refugia, and (c) the amount of time it took for terrestrial ecosystems to recover after the extinction event.

Methods: The palynomorph samples were collected across the Permian–Triassic boundary and had to be removed from the sedimentary host rock for identification and dated in order to compare what plants were present before, at the start of, and after the extinction event. To isolate the palynomorphs to study them, the samples were crushed, treated with a chemical solution to remove them from the rock itself, and filtered through a mesh screen. Out of the 129 samples, only 15 of them were well preserved enough for fossilization and identification. Of these 15, only 12 had enough individual palynomorphs to be used in the statistical analysis used to determine the relationship between samples. The samples were dated using a type of radiometric dating called U-Pb (uranium-lead) zircon dating. Radiometric dating is based on known rates of decay, or half-lives, of radioactive elements on Earth. Scientists can measure how much of a certain radioactive element is left within a sample and compare that with the half-life to figure out the age of the rock. The plant and animal fossils that were also collected were dated to reconstruct a timeline from 252.10 to 251.67 Ma, a period 59–160 thousand years before the extinction to 160 thousand years after the extinction.

Results: Scientists, using an analysis that plots data points by similarity, grouped the 12 samples into three assemblages. Each group has a unique composition of plants that represent a specific environment and were named after the plants that produced the most common palynomorphs in the group’s samples. The first is the Cyclogranisporites sp.-Lycopodiumsporites reticulumsporites (CR) assemblage from 212.10 to 252.00 Ma, 59 to 160 thousand years before the mass extinction. Most of the palynomorph fossils were spores for plants called lycopsids. Lycopsids, which include clubmosses, spikemosses, and quillworts, are found in humid lakeplain environments. Just below the CR assemblage, the scientists found a herbivorous mammal-like  Turfanodon fossil, leading them to believe that they were living with the lycopsids before the extinction (Fig. 1). The second group is the Alisporites landianus-Chordasporites australiensis (LA) assemblage from 251.99 to 251.93 Ma, right at the start of the mass extinction. Instead of lycopsid spores, the LA assemblage samples had pollen from seed producing trees and ferns, which are better suited to drier environments. This means that at the start of the extinction event the lake dried up and the plants that could live there changed. The third group is the Klausipollenites schaubergeri (Ks) assemblage from 251.72 Ma, 160 thousand years after the extinction. Similar to the first group, spore fossils make up the majority of palynomorph fossils which indicates a return to humid conditions and a decline in seed producing plants.

Three artistic reconstructions of the terrestrial environment of the South Taodonggou Section in northwestern China during, before, and after the Permian–Triassic mass extinction. Section A: during the Permian–Triassic mass extinction, shows a terrestrial landscape populated with conifers and ferns with little understory growth next to a partially dried up lake. In the background there are mountains and a clear sky. No animals are present. Section B: before the Permian–Triassic mass extinction, shows a terrestrial landscape with trees and dense undergrowth next to a lake. In the background are mountains and a cloudy sky. Three tufanodons, animals that resemble tusked rhinoceroses without horns or pronounced ears, are shown walking in the undergrowth and drinking from the lake. Section C: after the Permian–Triassic mass extinction, shows a terrestrial landscape with trees and tall reedy undergrowth next to a lake. In the background are mountains and a cloudy sky. Five herbivorous lystrosaurs, flat faced pig-like animals with two small tusks, are shown in the undergrowth, while two crocodile-like meat eaters watch from the lake.
Figure 1: Artistic reconstruction of the terrestrial environment of the South Taodonggou Section in northwestern China during, before, and after the Permian–Triassic mass extinction. (A) During the extinction, dry conditions populated by gymnosperms and seed-forests. (B) Before the extinction, humid conditions populated by lycopsids, including clubmosses, spikemosses, and quillworts, with the plant eating turfanodon imaged, too, (C) After the extinction, humid conditions return and surviving animals, including the plant-eating Lystrosaurus, shown grazing in the bottom center, and carnivorous chroniosuchian, an early relative of crocodiles, crawling out of the water, flock to the terrestrial refugia.

Why is this study important? The pattern observed in these samples is different from previous studies of the Permian–Triassic Boundary in nearby regions and more broadly across the world. This study suggests that the region was protected from drastic environmental changes, such as severe drought or excessive rainfall. While the increase in pollen at the start of the extinction event did indicate a shift toward a drier environment, the spores returned within the next 160 thousand years, which is quick in geologic time and means that the drought was neither excessive nor long lasting. Until recently, it was believed that terrestrial ecosystems took millions of years to recover to pre-extinction levels of complexity. This was based on the response of marine ecosystems, which are more likely to fossilize and are therefore more heavily researched and better understood.

Broader Implications of this study: These findings demonstrate a need to reexamine currently held beliefs surrounding the terrestrial response to the Permian–Triassic mass extinction and the importance of isolated plant communities, or refugia, on terrestrial ecosystem recovery. These questions become ever more important as terrestrial ecosystems throughout the world experience changing conditions. Understanding past responses to climate change can help scientists predict what may happen in the future, for plants, animals, and people.

Citation: Peng, H., Yang, W., Wan, M., Liu, J., & Liu, F. (2025). Refigium amidst ruins: Unearthing the lost flora that escaped the end-Permian mass extinction. Science Advances, 11(11), eads5614. https://doi.org/10.1126/sciadv.ads5614

The characteristics that contributed to megafauna extinction in the Quaternary Period (over the last 2.6 million years)

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Phylogenetic Evidence Supports the Effect of Traits on Late-Quaternary Megafauna Extinction in the Context of Human Activity

By: Rhys Taylor Lemoine, Robert Buitenwerf, Sören Faurby, and Jens-Christian Svenning

Summarized by: Hailey Faurot is a senior Environmental Science Ecosystems major at Binghamton University minoring in History. She plans to pursue a career in environmental education and/or wildlife conservation. In her free time, she likes to birdwatch, dance, play music, and spend time with family and friends. 

What data were used? Scientists collected data concerning the extinction status of 548 mammal species, 196 still extant (alive today in the wild), which was compared with the evolution of the absence or preservation of 17 traits that were selected from preexisting datasets. These traits included Paleotropical occurrence, phylogenetic link to the paleotropics (the historically warmer regions of the planet), insularity, body mass, limb morphology (walking style– on their toes (like a dog), their entire foot (like elephants), etc., arboreality (to what degree did they live in trees), molar morphology (tooth variations), guild, fermentation (how did their digestive system work), home range (size of their geographic range), dispersal distance (how far they spread out), native range (size of the area they were originally from), temperature range (what temperatures did they tolerate), precipitation range, activity cycle (nocturnal, etc.), encephalization quotient (how large their brain was compared to their body), and generation time (how long it takes them to produce offspring). These traits fell into the categories of functional, biogeographical, and phylogenetic. 

Results: The researchers found that three of the 17 traits were the most significantly impactful in the risk of extinction. These traits, outlined below, led to greater extinction largely because of their relationship to human hunting techniques and preferential hunting by humans towards animals with these traits. 

  1. The researchers found that modern species that were more closely related to paleotropical species were at a lesser risk of modern extinction 
  2. Plantigrade species, animals who walk on a flat foot, such as bears and elephants were more at risk of extinction 
  3. Island endemic species (those specific to an island location and not found elsewhere) were more likely to go extinct 
  4. Larger bodied species were at a higher risk of modern extinction compared to the other species in the study 
Figure 1 contains four graphs labeled A, B, C, and D. Graph A uses a bar chart with an x-axis labeled to represent the bars “continental” and “insular”, and a y-axis of 0-1 representing a proportion of all species surveyed to show the relationship between Insularity and Extinction, depicting insular species being a greater proportion of extinct species and placing a silhouette of deer above each bar. Graph B depicts nonplantigrade species as being extinct in greater proportion than plantigrade and has a silhouette of a wolf above the “non-plantigrade” bar and a silhouette of a bear above the “plantigrade” bar. Graph C depicts the relationship between phylogenetic distance to paleotropical relative and extinction and depicts an armadillo on the left side of the graph and an elephant on the right side, showing that the majority of extinct mammals have low phylogenetic distance to their paleotropical relative and the majority of extant mammals have high phylogenetic distance to their paleotropical relative. Graph D depicts the relationship between body mass and extinction, the number of extinct and extant species increases with body mass.
Figure 1. Graph A in the above figure depicted the proportion of extinct and extant species of each group of mammals, comparing those that live on mainland continents (continental) and island-dwelling species (insular). Graph B depicts the proportion of extinction of limb morphology, comparing not plantigrade vs plantigrade (flat footed) of each animal. Figure C represents the proportions of extinct mammals and extant mammals that have high and low phylogenetic distance to their paleotropical relative. An example of a modern day mammal and its paleotropical relative would be the modern three-toed sloth and the extinct giant ground sloth. Figure D represents the proportions of extinct and extant mammals by body mass. The axes have been rescaled mathematically for easier visualization.

Why is this study important? This study is important because it helps us understand the traits that extinct species possessed that may have contributed to their extinction or to their survival at the hands of human hunters and other environmental factors throughout the Quaternary Period. Larger-bodied species were disproportionately at greater extinction rates because early humans could hunt them with tools and were likely motivated to do so because of the large amount of meat that could be sourced from these animals. Island endemic species were more prone to extinction by human and other factors because of their limited range size. Lastly, plantigrade species (those that walked on the entire soles of their feet) were able to be exploited by humans because of their slower movement. 

Broader Implications beyond this study: This study’s results have broader implications beyond the field of paleontology, including effects on ecology and wildlife management. If we can specifically pinpoint phylogenetic traits that caused life to go extinct in the past, we can more appropriately manage wildlife in the present, specifically against threats such as poaching and illegal harvesting by humans. 

Citation:  Lemoine, Rhys Taylor, Robert Buitenwerf, Sören Faurby, and Jens-Christian Svenning. 2025. “Phylogenetic Evidence Supports the Effect of Traits on Late-Quaternary Megafauna Extinction in the Context of Human Activity.” Global Ecology and Biogeography 34(7): e70078. doi:10.1111/geb.70078. 

Morphology and feeding stress within tyrannosauroid dinosaurs (such as T. rex)

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Morphological evolution and functional consequences of giantism in tyrannosauroid dinosaurs

By: Andre J. Rowe, Emily J. Rayfield

Summarized by: This article was summarized by Gillian Rohde, who is a senior biology major at Binghamton University. She is on a pre-physician assistant track. Outside of school, she enjoys reading, hiking, and drawing. 

Data: Seven different skulls across six species within the family Tyrannosauroidae were scanned for this study: Raptorex kriegsteini, Bistahieversor sealeyi, Albertosaurus sarcophagus, Alioramus altai, Daspletosaurus torosus, and two Tyrannosaurus rex (one juvenile and one adult). The family Tyrannosauroidae is defined by shared characteristics such as broad skulls, small forelimbs (arms), long legs, and a meat-based diet. However, species of this family vary in size, skull morphology, and ecological niche. The researchers used complete skull specimens from different museums and research institutions. R. kriegsteini is a species defined by a single specimen thought to be a juvenile that measures ten feet long. B. sealeyi as an adult measured 30 feet long and had many unique features including an extra opening above the eyes to lighten the skull. A. sarcophagus measured 30 feet long and are thought to have been apex predators of their environment. A. altai is estimated to have measured 20 feet long and is defined by a low and long skull decorated with crests above the nose. D. torosus measured about 30 feet long and are defined by their fused cranial bones and orbital crests. Finally, T. rex, the most well-known species of the family, was an apex predator that measured over 40 feet long. 

Hypotheses:  Researchers posed two hypotheses. The researchers first proposed that larger tyrannosaurid species experienced higher stresses within their skulls during feeding because of their large size. Researchers thought these larger species would also be able to absorb these higher stresses without breaking. The researchers then proposed an alternative hypothesis that stated smaller-bodied tyrannosaurid species would experience higher feeding stress than larger species, because larger species have more robust skull morphology: wider-set jaws and a deeper upper skull. 

Methods: The researchers scanned the skulls through surface scanning or CT scanning to create 3D models. Surface scanning uses light to measure the surface of an object, and the data collected creates a digital model on a computer. CT scanning uses X-rays to create a 3D model. The scientists used the 3D models from each specimen, used computer programs to perform simulations that would mimic the feeding stresses on the 3D models, and calculated those different stresses. The researchers measured von Mises stresses, which are equivalent values made up of tensile, compressive, and shear stresses. Tensile stress is the force per unit area that a material experiences due to pulling. This measures how much a material (in this case, the skull bones) resists being pulled apart. Compressive stress is the force per unit area that a material experiences due to a force trying to shorten or compress a material. This measures how much a material resists being compacted. Finally, shear stress is the force from per unit area a material experiences due to another material sliding against it, which causes tearing. A larger stress value means that a material has lower resistance to breaking. These stresses all occur during feeding from the upper and lower jaw grinding against each other and the food during chewing across all jawed animals. 

The study also measured principal strain, which is the maximum and minimum amounts of stress a material experiences under load. Load is an external force or pressure applied to an object, causing it to experience stress. The scientists calculated these feeding stresses for the different Tyrannosauroidae skulls at both their actual size and at a size corrected scale. The size-corrected models made it so all the skulls were all the same size, which allowed them to compare the relative stress based solely on skull shape. The actual size model is based on both skull morphology and the size of the skull, which makes it biased towards larger specimens. 

Results: The study found that higher von Mises stresses (i.e., combined stress from chewing) were experienced in midsized tyrannosaurids when measuring skulls at their actual size. This is because larger tyrannosaurids ate larger prey, which required an increased bite force. However, to make up for this increased bite force, large tyrannosaurids had increased resistance to stress due to their wider-set jaws and thicker skull bones. This increased resistance is shown in the “size corrected” scale in Figure 1. When researchers examined the stresses for the size corrected models, the smaller species that had narrower jaws experienced higher stress and thus were more likely to experience breakage during feeding. This lack of stress resistance is why smaller tyrannosaurids ate smaller prey. Max principal strain (from jaws grinding against food) was also the highest in the smaller tyrannosaurid species. These findings support hypothesis one, where larger tyrannosaurids experience higher feeding stress due to the size of their prey, but to make up for this, they have greater stress resistance than smaller species. 

The diagram shows four skulls of the Tyrannosauroidae species of varying sizes, ordered from small to large on two columns. The smallest species is Raptorex, the second smallest is Albertosaurus, the 2nd largest is Daspletosaurus, and the largest is Tyrannosaurus. The left column has an arrow pointing from the largest skull up towards the smallest skull, labeled with increasing stress. This column shows the increasing stress levels experienced when the skulls are size-corrected. The right column has an arrow pointing in the opposite direction from the smaller skulls to the larger ones labeled with increasing stress. This column represents the skulls when they are at their actual size. All of the skulls are colored from blue (lower stress) to red (higher stress) in a gradient. Different parts of the skull experience varying levels of stress, as showcased by the varying colors.
Figure 1: Larger species within the family Tyrannosauroidae experience higher feeding stress in their skulls and jaws, as seen by the “actual size” axis. However, larger species show increased resistance to feeding stress as showcased by the “size-corrected” section. If smaller species and their skulls were the same size as larger specimens, they would experience higher feeding stress and be more likely to experience breakage. 

Importance of the Study: This study is important for learning more about how members of the Tyrannosauridae family fed and what niche each species occupied. A niche is the role that an organism plays in its environment. Smaller species of Tyrannosauridae did not share the same apex predator role that larger species had. Smaller species of Tyrannosauridae would have hunted smaller prey and thus not competed with larger species. The high stress resistance in larger tyrannosaurids may explain their evolutionary success as apex predators. 

Broader Implications Beyond This Study: The methods from this study can be applied to other groups of carnivorous organisms and thus be used to figure out the niches of other species. The feeding stress and stress resistance can be used to infer the size of prey. Larger predators who hunted larger prey would have increased stress resistance.  

Citation: Rowe, A. J., & Rayfield, E. J. (2024). Morphological evolution and functional consequences of giantism in tyrannosauroid dinosaurs. IScience, 27(9). https://doi.org/10.1016/j.isci.2024.110679 

First evidence of Ecuadorian mosasaur (marine reptile) fossils

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First record of a mosasaurid (Squamata: Mosasauridae) from the Upper Cretaceous of Ecuador

By: D. N. Garzon, Paul Arellano, Jorge Toro-Álava, José Luis Román Carrión, Julián Escobar Ordoñez, Pamela Andrade, Carlos Mendoza-Ochoa, Paula Ayala, Mateo Oleas, Anthony Vizcaino, Nelson Mesías Jiménez-Orellana

Summarized by: Erick Morales, who lives in Bedford Hills, NY, and is a senior at Binghamton University studying biology on the pre-physical therapy track. He also plays for the Binghamton University Symphony Orchestra as a violist. In his spare time, Erick loves to spend time with his family and friends and go to the gym. 

What data were used? This whole study is based on one fossil, which is an incomplete upper right jawbone, called the maxilla bone. Scientists identified it as a mosasaurid jaw based on the shape of the maxilla and the seven preserved teeth (Fig. 1). Mosasaurs were large marine reptiles that lived during the Late Cretaceous. This maxilla contains seven preserved teeth that are conical, smooth, and robust, which are key features that help determine it belongs to a mosasaurid. These teeth provided important anatomical evidence, despite the fossil being a fragment. The fossil was discovered in a limestone cave by members of the Rikuna research expedition together with Carlos Cerda, an Indigenous leader from the Tamia Yura community. Scientists also examined the surrounding limestone, marine sediments, and small fossils within the cave’s stratigraphic layers. 

What is the point of this paper since there is no hypothesis? The point of this paper was to document the first ever known mosasaurid fossil in Ecuador and provide geological and evolutionary context to it.

Methods: After the fossil was first recovered, researchers used preparation techniques such as careful acid cleaning to remove the surrounding rock without damaging the specimen. Once the fossil was exposed, they used computed tomography (CT) scanning to create a high-resolution 3D digital model of the jaw. The CT scans allowed the scientists to examine internal structures, such as the tooth roots and ridges , and to confirm the fossil’s identity without physically altering it. To determine the age, the researchers analyzed the stratigraphic layer in which it was found. They used biostratigraphy (i.e. they used fossils with a known geologic time span)  to identify the surrounding limestone and sediments as part of the Middle Napo Formation in the Cretaceous.

Results: From what was gathered, the fossil found consists of an incomplete right maxilla of about 30 centimeters in length, which holds seven teeth. These teeth are conical, smooth, and robust, which are characteristics of teeth that match a mosasaurid. Although the fossil is incomplete, comparisons with a similar species found in Colombia allowed scientists to approximate the length of the skull at about 30 centimeters and the full skeleton at likely 608.7 centimeters (about 6 meters). The fossil was preserved in rocks formed in shallow marine waters, indicating that the region where the Amazon rainforest is today was once covered by warm and coastal waters.

A- Line drawing of a mosasaur skull in side view, showing the jaws and teeth. A shaded section near the middle of the upper jaw highlights the area represented by the fossil described in the study. B- Photograph of the incomplete right maxilla preserved in brown limestone. The fragment is about 30 centimeters long and shows smooth bone surfaces with several teeth. A white scale bar in the lower right corner represents 5 millimeters for size reference.
Figure 1: A. Line drawing of the found mosasaur skull in side view showing the position of the maxilla, with the shaded region indicating the portion preserved in the fossil; the unshaded region is the likely shape of the fossil based on other mosasaurid fossils. B. Photograph of the incomplete maxilla preserved in brown limestone inside the Uctu lji Changa cave in Ecuador. A white 5 mm scale bar is shown for reference. The size and tooth structure indicate it belonged to an average-sized mosasaurid that lived in shallow marine waters during the Late Cretaceous 

Why is this study important? This fossil is the first evidence of a mosasaur in Ecuador, which fills a major gap in South America’s fossil record. Many mosasaurid fossils were found in other parts of South America, but not Ecuador. Its discovery shows that these ancient marine reptiles ranged throughout much of the Cretaceous seas in South America. 

Broader implications beyond this study: Because the fossil was preserved in shallow-marine rocks, it provides direct evidence that the area now occupied by the Amazon rainforest was once part of a warm coastal seaway during the Late Cretaceous. By showing that mosasaurs lived in what is now inland Ecuador, the fossil expands the known range of Cretaceous marine environments in South America. This data helps paleontologists map where ancient coastlines and seaways once existed. Furthermore, it’s possible that the cave system containing the fossil still harbors other fossils, implying that this discovery is just the start.

Citation: Garzón, D. N., Arellano, P., Toro-Álava, J., Román-Carrión, J. L., Ordoñez, J. E., Andrade, P., Mendoza-Ochoa, C., Ayala, P., Oleas, M., Vizcaino, A., & Jiménez-Orellana, N. M. (2024). First record of a mosasaurid (Squamata: Mosasauridae) from the Upper Cretaceous of Ecuador. Spanish Journal of Palaeontology, 39, 1–12. https://doi.org/10.7203/sjp.29179  

Two distantly related trilobite species both evolved the same trait separately

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Parallel Evolution of Unusual ‘Harpiform’ Morphologies in Distantly Related Trilobites

By: James D. Beech, David J. Bottjer, Nathan D. Smith

Summarized by Erich Reineking: Erich lives in Binghamton, New York, but is from Oakdale, New York on Long Island. He is a student at Binghamton University who is pursuing a B.S. in Geological Sciences and a B.A. in Mathematical Sciences. During the summers, Erich is a lifeguard at the beach. In his free time, Erich likes to watch baseball, play golf, play video games, and hang out with his friends.

What data were used? Scientists collected data from around 114 different trilobite species. Out of the 114 trilobite species, 21 were from the one order and 56 from a different family. The remaining 38 species were a mix from different groups, including. The scientists constructed lists of characteristics that were visible across all of these different trilobite species. They identified 112 characteristics (or characters) to use in the experiment. They found out which trilobites had which characters by looking at digital and physical museum specimens, in addition to photographs found in published literature on trilobites.

What was the hypothesis being tested ?  The goal of the paper was to figure out how two two groups of trilobites, the Harpetida order, and the Trinucleioidea family, evolved their ‘harpiform’ brim (Fig 1), which is the wide, flat part that sticks out around the head region, and has many holes in it. Scientists were examining if the two groups are closely related and gained their brim from common ancestry, or did both groups evolve the feature separately.

Methods: Scientists used the 112-character traits in order to perform an evolutionary analysis using parsimony. The parsimony analysis was performed in computer programs, which examines the possible evolutionary paths, and finds the one that has the fewest changes from the beginning to the end of the tree , meaning it is the most likely one to have occurred. The analysis took three main things into consideration, which are believed to be the characters most important in the evolution of the trilobites. The first being the “yoked condition of the libriganae”, which is the piece that makes the front of the head shield look fused together. The second was the placement of the facial suture, which runs along the bottom, around the edge of the trilobite brim. The third was either the appearance, or absence of a well-developed brim. These features can be seen in Fig. 1. The scientists also performed a constraint analysis, which restricted some of the created trees to certain parameters, and was then compared to the other created trees. In other words, the scientists forced specific groups to be more closely related in the analysis so they could compare the total number of changes in the trees of these forced results against the results where no such constraints were enforced. 

Shows four images of trilobite heads. The first one shows a flat semi circular shape, with pointed ends coming out of the back of the head. The second one shows the slight rounding of the head shape. The third one shows the pointed ends becoming longer and also less pointed and more rounded. It also shows the thickening of the outer rim of the head shape. The fourth and final one shows the enlarging of the outer rim, and the outer rim also becoming more circular.
Figure 1. Here shows the progression of the ‘harpiform’ brim that is being studied. Moving from 1 to 4 shows the progression over time, with 1 showing what the ancestor would have looked like, and 4 showing a trilobite with the ‘harpiform’ brim.

Results: The evolutionary analysis inferred a number of most parsimonious trees (i.e., trees with the same number of changes). Scientists created a strict consensus of all of these trees, which only uses relationships found across all of the most parsimonious trees.  The researchers found that the three characteristics mentioned in the above methods section, i.e., the head shield, the edge of the brim, and the development of the whole structure, all showed up many times, in separate and distinct ways between the harpetids and the trinucleids. These data suggest that the harpiform brim was a characteristic that evolved separately between the groups, and not something that made them closely related. It is kind of like how you wouldn’t say an eagle and a butterfly are closely related, just because they both have wings. Tracing both groups back to their last common ancestor shows that it did not have the harpiform brim, which is strong evidence that they arose on their own. These two groups can be referred to as “phylogenetically independent”.

Why is this study important? This study shows a great example of homoplasy, or convergent evolution (Fig. 2). Homoplasy means that similar traits that evolved separately, like the eagle and butterfly example explained above. Scientists studied two distantly related groups of trilobites that share a similar morphology. This study shows ways to use phylogenetic analytical methods to tell the differences between different groups. This helps us to reevaluate the relationships between species, so that scientists can learn how they evolved. Was it environmental, ecological, or other factors that impacted how they evolved over long time periods? Although this wasn’t what was tested, scientists still hypothesized that they could of used the brim as a sort of  snowshoe, as the brim would have spread out its body density and not sink into soft sediment. It also could have been used as a body part that was good at picking up vibrations, letting the organisms know more about their surroundings. Due to the shape of the brim, it also could have been used to filter the food that it was eating. These are all great ideas, but it would take further studies to know the true reason.

Shows 3 different types of evolution on 3 charts. The first one, stasis, shows 2 species that start as a blue and red circle, both pointing to another circle of the same color, again pointing to a third circle of the same color. The second chart shows convergent evolution, the blue species starts as a triangle, then a rounded triangle, finishing as a circle. The red species starts as a square, then a rounded square, also finishing as a circle. The third type, parallelism, has a blue triangle, going to a rounded triangle, then a circle. The second species, a red triangle starts as a triangle, then a rounded triangle, finishing also as a circle.
Figure 2. Here are the different ways that a trait can evolve. 1 shows stasis, which means there is little to no change in traits. 2 shows convergence, different species evolving their trait in their own way. 3 shows parallelism, similar species evolve a trait by similar methods. The study is mainly examining convergent evolution, but it is important to understand other kinds as well. 

Broader Implications beyond this study: By conducting this study, we have learned more about how different groups of trilobites are related. The researcher sexamined species that were thought to have been extremely closely related to each other because of their similar morphology. Often, original groupings of animals were based on what things looked like, and not the possibility that things can look the same but not be closely related–again, even though butterflies and eagles both have wings, it does not mean they are closely related. In this study’s case, their close relationship was believed to be because of their harpiform brims. But in reality, they are not as closely related as we once thought. This raises the question: how many other species could this misunderstanding have happened to? The methods that were used in this experiment can be adopted and used in other similar experiments. This experiment can open the door to the revaluation of many species, which will better help our understanding of the relationships between ancient species.

Citation: Beech, James D., David J. Bottjer, and Nathan D. Smith, ‘Parallel Evolution of Unusual “Harpiform” Morphologies in Distantly Related Trilobites’, Journal of Paleontology, 98 (2024), 732–43 <http://dx.doi.org.proxy.binghamton.edu/10.1017/jpa.2024.47&gt; 

Effect of Mass Extinctions on Crocodile Ancestor Evolution

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For a while, crocodile: crocodylomorph resilience to mass extinctions

by: Keegan M. Melstrom, Kenneth D. Angielczyk, Kathleen A. Ritterbush, and Randall B. Irmis

Summarized by: Emily Rosenberger, a 3rd year undergraduate student studying geology at Binghamton University. In her free time, she enjoys hiking, learning guitar, and reading whatever she can get her hands on.

What data were used? Researchers collected data concerning the skulls of 99 extinct crocodylomorphs, which is the group that includes currently living crocodilians and their ancestors, 20 skulls of modern crocodilians, 81 skulls of mammals, and 47 skulls of reptiles. Traits such as tooth shape, snout and skull length, and jaw size were measured. By comparing the shapes of extinct crocodylomorph skulls to the skulls of animals with known diets and habitats, the researchers reconstructed the diets and habitats of the extinct crocodylomorphs. Researchers also collected data on when each extinct crocodylomorph group was alive and an estimate of how abundant each group was ecologically.  

What was the hypothesis being tested: The goal of the study was to determine what physical characteristics, present in the skull, and ecological traits allowed crocodylomorphs to survive two mass extinctions, the end-Cretaceous and the end-Triassic, which caused all other members of their clade, Pseudosuchia, to die out. 

Methods: Scientists took photos of the top and side of all of the skulls included in the study. After digitizing the images, the researchers were able to compare different measurements from the crocodylomorph skulls, such as eye socket size and snout length to the skulls of the other animals. The similarity in skull and tooth shape between extinct crocodylomorphs and modern animals was used to reproduce the diets and lifestyles of the extinct crocodylomorphs. Researchers created the following five categories separated by diet and habitat: aquatic carnivore, terrestrial hypercarnivore, terrestrial herbivore, semiaquatic generalist and terrestrial generalist, as typically, these diets and habitats are associated with specific traits (e.g. carnivores have sharper teeth than herbivores). Using the five categories they created and the time period each was known to be alive during, the researchers charted during what time periods the categories had more or less species surviving (Fig 1.)

Results: Researchers found that there have been many crocodylomorph lifestyles over the past 200 million years. In this study, crocodylomorphs with similar skull shapes were assumed to have lived similarly (i.e. in their diet, habitat). Crocodylomorphs had very similar skulls during the Late Triassic, which researchers interpreted as having similar lifestyles. During the end-Triassic extinction, the most heavily populated category was the terrestrial generalist category. After this extinction, crocodylomorph skulls showed an increase in lifestyle diversity through an increase in skull shape variety of crocodylomorphs throughout the rest of the Mesozoic. This variation in crocodylomorph lifestyle was highest in the Late Cretaceous. After the end-Cretaceous extinction, only two of the five types of crocodylomorph lifestyles survived. Aquatic carnivores eventually died out, and only semiaquatic generalists survived into modern times. Researchers believed the two categories of crocodylomorphs that survived and thrived after extinction events, first the terrestrial generalists and later the semiaquatic generalists, were able to do so because they did not require as specific of diets as the specialist categories did.

Chart A shows the number of species present across the past 200 Ma in each of the five crocodylomorph niches (aquatic carnivore, semiaquatic carnivore, terrestrial generalist, terrestrial hypercarnivore, and terrestrial herbivore), with number of species on the y-axis and time on the x-axis. The chart emphasizes an extinction event that caused the dominance of aquatic carnivores at 200 Ma and another extinction event at 66 Ma that caused a change from the dominance of aquatic carnivores to the dominance of semiaquatic generalists. Each extinction event is marked by yellow lines parallel to the y-axis. Chart B shows the change in taxon count of crocodylomorphs, shown on the y-axis, over the past 200 Ma, shown on the x-axis. Scientists noted two different extinction events with yellow lines parallel to the y-axis at 200 Ma and 66 Ma. The taxon count increases between 200 Ma to 66 Ma, before declining and flattening out after 50 Ma.
Chart A shows the prevalence of aquatic carnivores during the end-Triassic Extinction. The end-Cretaceous event shows the prevalence of semiaquatic generalists. Chart B shows the taxon count of crocodylomorphs throughout geological time, from the Triassic to modern times.

Why is this study important? Researchers in this study compared skull shape data of crocodylomorphs taken during this study and skull shape data from past studies to create lifestyle categories for extinct crocodylomorphs. Using this lifestyle data, they were able to add to the knowledge about what traits allowed crocodylomorphs to survive mass extinctions and how the current niche of semiaquatic generalists in crocodilians emerged.

Broader Implications beyond this study: Crocodylomorphs used to have many different lifestyles in both land and water. By understanding the past trends of crocodylomorph extinctions, the current threats faced by living crocodilians can be better understood and current conversation efforts can be better focused. Looking at what lifestyles crocodylomorphs were able to fill after the end-Triassic and end-Cretaceous extinctions may provide a view into the overall effect these extinctions had on the ecosystem as a whole.

Citation: Melstrom, K. M., Angielczyk, K. D., Ritterbush, K. A., & Irmis, R. B. (2025). For a while, crocodile; crocodylomorph resilience to mass extinctions. Palaeontology, 68(2), Article 70005. https://doi.org/10.1111/pala.70005

Rebuilding bird mating behavior using footprints from the Miocene (23–5 million years ago)

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Reconstructing Miocene bird mating behavior from a fossil track site

By: Nasrollah Abbassi 

Summarized by: Elizabeth Kolosovskiy is a senior at Binghamton University, majoring in biology and minoring in forensic health. She plans to graduate in December and take a few months off to travel before coming back in May to start the accelerated nursing program at Binghamton University to obtain her second degree. During this time, she plans to continue working at UHS Wilson Memorial Hospital. After earning her degrees, she plans to continue to advance her education to become a CRNA. When she is not working or studying, she enjoys going to the gym and spending time with her family and friends.

Data: Scientists studied a small, fine-grained sandstone slab predicted to be between 7.5 – 17.5 million years old that they found in the Chehr-Abad area, 90 kilometers west of Zanjan, Iran. More specifically, they found the slab 1,256 meters above sea level on the side of a cliff within the Upper Red Formation (URF). The URF is a universally important Miocene rock unit in Northwest Iran, known for its distinctive red color, which is attributed to the presence of iron in the rock. This formation enabled scientists to learn that the Miocene was a warm and dry period characterized by many diverse species that lived in deserts or plains with occasional sources of water, such as rivers, providing a better understanding of how ecosystems changed over time and why. The slab researchers removed contained 70 small tetradactyl (a bird with four fingers on one limb, three facing forward and one backward) footprints left in various patterns based on the different movements that were most likely made during mating dances.

Hypothesis: Behavioral traces do not always fossilize, and if they do, it is difficult to predict what organism created them because the organism that made the trace does not usually fossilize alongside it and can leave more than one type of trace behind. However, these fossilized bird mating prints were distinct and well-preserved. Since modern birds exhibit specific mating behaviors that also leave behind traces, scientists hypothesized that they can gain a deeper understanding of contemporary bird behaviors by drawing parallels between these ancient traces and modern traces.

Methods: Scientists were not able to collect the full sample due to the difficult terrain, so researchers took detailed photos of the remaining slab using a quadcopter (drone with four spinning propellers and a camera). They then combined all the images to measure and shape the footprints and tracks using Adobe and Photoshop software. Researchers identified features of the footprints, such as length, width, angle, pace, stride, and area, to help differentiate between various behaviors. They measured the distance between the left and the right tracks to determine the pace, the distance between a set of two left or two right tracks to determine the stride and measured how far each track was pointing from the line of travel (a straight line down the center of the tracks) to determine the angle of the track. After grouping each track into a behavior type, scientists recorded how often one behavior led to another, excluding a track if it only showed one behavior (Fig. 1). Finally, they used a a statistical test called a Markov chain that assumes that each behavior occurs based on the one that comes before it and compiled these results into a chart that shows how many times a behavior changed and the probability of the change occurring. This helps scientists understand if there is a pattern in the tracks. 

Results: Scientists discovered seven types of behaviors in the fossil tracks: walking, high stepping, stomping in place, short-distance flying, hopping, pecking, and lateral leaping. Walking was the most abundant movement, characterized by a straight line of tracks with a consistent, repeated pattern in stride and pace. High-stepping was the second most common behavior, marked by many newer footprints overlapping the ends of older prints in a dense, repeated pattern, all in one spot. Stomping was the third most abundant movement, characterized by multiple small areas at the beginning, middle, or end of tracks with overlapping, dense footprints similar to high-stepping, but accompanied by digging. Short-distance flying was indicated by short gaps in tracks with no footprints. Finally, hopping was identified by paired footprints, pecking was shown by repeated scratches on the side, beginning, or end of tracks, and lateral leaping was the least abundant behavior, characterized by short lateral jumps and are found within high-stepping tracks (Fig. 5). When analyzing the data they obtained on the transition of behaviors they ruled that there was a relationship between hopping and singing, but that they needed more data from other ancient and modern dances to compare and definitively determine a pattern. However, when comparing the tracks’ shape and patterns to those of modern birds, they were able to definitively state that these footprints represent the same quick movements used by modern avian birds during complex mating tap dances and that multiple animal organs were involved. Since the measured prints were 20 mm long and wide, scientists estimated the birds to be around 6cm tall and believe the tracks and peck marks belong to a species closely related to modern semi-aquatic plover birds, called Gruipeda fuenzalidae.

This figure shows two drawings of the irregularly shaped slab labeled a and b. Drawing A depicts the light yellow slab on top of a lavender background, with all original markings and traces that are not labeled or color-coded. Drawing B presents the slab in black against a light green background, with fossil tracks color-coded by behavior and arrows indicating their directions. Walking is shown in yellow, high-stepping in red, stomping in place in orange, hopping in green, pecking in purple, short flying in grey, and lateral leaping in blue. There are a few circles on the slab that represent actions that occur in one spot, and arrows that indicate movement across the slab and which action leads into the next.
This image shows the slab that was collected in two drawings. Drawing A shows the original slab with all the small tetradactyl fossil tracks unmarked and unidentified, with no arrows, circles, or colors. Drawing B shows all the tracks color-coded based on behavior and the direction of each footprint. Walking is represented in yellow, high-stepping is red, stomping in place is orange, hopping is green, pecking is purple, short flying is grey, and lateral leaping is blue. Circles are used to represent actions that happen in one place, whereas arrows represent movement across the slab.

Significance: This trackway fossil is significant because it is some of the only fossil trace evidence has been found showing bird dances from millions of years ago. This helps scientists understand and track how bird behavior evolved, rather than focusing on the birds’ change in morphology and assuming bird behavior from this. This discovery also led to the creation of a new behavioral fossil classification category, called Goshnichnia, for fossil mating traces.

Broader Implications beyond this study: The discovery of this fossil track and the creation of a new behavioral classification category mean researchers will be able to assess more data for comparison between species and time periods, confidently determine more mating tracks and patterns, and predict how these changes influenced survival, reproduction, competition, and whether there was environmental influence.

Citation: Abbassi N. (2025). Reconstructing Miocene bird mating behavior from a fossil tracksite. Scientific reports, 15(1), 25563. https://doi.org/10.1038/s41598-025-11727-y 

What a Single Tooth Can Tell Us About The Lives of the Largest Animals to Live in the Sea

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A multi-method approach to deciphering the paleobiology of a mosasaur from South Africa

by: Megan R. Woolley, Michael W. Caldwell, Kevin Rey, Romain Amiot & Anusuya Chinsamy

Summarized by: Eli Steingardt is a Philosophy, Politics, and Law major at Binghamton University. Currently, he is a sophomore. He plans to attend law school and advocate in courts on behalf of museums in legal disputes over samples and specimens. In his free time, he plays electric guitar and tutors at Binghamton’s writing center.

What data were used? This study was focused on a tooth discovered as part of a jawbone in South Africa that scientists suspected to have come from a mosasaur called Prognathodon. Mosasaurs were large, aquatic lizards that lived in the Late Cretaceous, between around 95 million years ago and 65 million years ago, when they died along with the non-bird dinosaurs in a mass extinction event caused by an asteroid known as the Cretaceous-Paleogene event. Since mosasaurs lived in marine environments millions of years ago, many different variables–such as depth of the water, the temperature, salt content of the water, and proximity to landmasses–make studying these creatures complex. 

What was the hypothesis being tested? Prior to this study, there was a lack of knowledge on the life habits of mosasaurs. The researchers cast a broad net when thinking of hypotheses to test, using many different exploratory tests to try to find something new about the lifestyle and paleobiology of the newly discovered fossil that they suspected belonged to the taxon Prognathodon. Paleobiology is simply anything relating to the study of extinct animals that are in the fossil record. This includes gaining insight into the animals’ growth, ecology, their closest relatives, and painting a better picture of a world that no longer exists.Some data involving the chemical record of other fossil organisms was also obtained to compare their results to. 

Methods: Scientists subjected the tooth fragment to some non-destructive analyses in order to learn more about it, like micro-CT scanning in order to make a 3-D image of the tooth and its internal structures. They also performed some destructive analyses, like putting a broken-off piece of the tooth under a Scanning Electron Microscope (SEM). They coated the piece in gold so it would show up clearer under the SEM, then scanned a beam of electrons at it in order to      build an image of the interactions between the electrons and the atoms of the sample. The scientists then shot X-rays at the piece in a process called Energy-Dispersive Spectroscopy in order to find out what elements the piece was composed of. The scientists went back to the original tooth, taking small samples and analyzing it for oxygen isotopes, to try to find out how much oxygen was in the tooth, which would tell      them about the environment that the animal lived in while it was still alive. Finally, the scientists coated the tooth in resin, cut it into thin slices, and looked at it under a microscope in a process called a histology to study the preserved internal structure of the tooth          .

Results: The micro-CT scan showed that the tooth had no root but still had some preserved tissue attachments, which suggests that the tooth had been partially shed from the jaw before death but was still slightly attached by gum tissue when it was buried Under the microscope (figure 4), scientists found that the tooth was poorly preserved, with small scratches and lumps on the tooth. This indicated that the Prognathodon probably preyed on hard-shelled animals, like turtles, whose shells would have scratched the teeth They also noted small spherical structures within the tooth, which researchers described as being clumps of calcium carbonate that typically form in warm, shallow water called ooids (which comes from the Greek word for egg or egg-shaped). The Energy-Dispersive Spectroscopy also indicated the presence of calcium carbonate, supporting the hypothesis that these structures are, in fact, ooids. For the oxygen isotope analysis, the scientists were able to find out the surface temperature of the water that Prognathodon swam in because shifts in percentages of oxygen isotopes tell us indirectly about past water temperature. From there, they were able to determine the amount of oxygen isotopes that the Prognathodon itself took in and therefore could infer its body temperature. They compared the data they collected from the Prognathodon to a shark that lived around the same time, Squalicorax. Since the two animals swam in the same ocean, they could be valid subjects for comparison. The scientists were able to determine that the Prognathodon had a body temperature that was warmer than Squalicorax. Since the Prognathodon was warmer than the shark, it was also probably warmer than the ocean around it.

A is a photo of a blunt tooth, cross-sectioned. The upper section is white, made up of several concentric half-ovals that narrow to a point. The base is made up of grey, rocky material. B is a microscopic image of the top of the tooth. It shows several black lines cutting vertically through iridescent, feather-shaped material. C is a microscopic image of one side of the tooth. It shows several varied vertical black lines cutting through a white matrix. D is a microscopic image of the base of the tooth. It shows a spongey, stony material, with many long, porous holes that range from 500 to 1000 μm across.
Figure 4: A, The tooth was cut lengthwise into many thin slices to see its cross-section. This was a slice taken from the middle of the tooth. B, This is a microscopic photo of the outer enamel surface (OES) at the top of the tooth when it was held up to a type of light called polarized light. The light showed the different layers of the enamel and the different structures inside that aren’t visible to the naked eye. The lines represent the different layers. Note the feather-like structures  and black separations in layer 2. In layer 5, look for the black arrowheads that point to small, black, globular structures. C, A section of the inside of the tooth called dentin was also held under polarized light. D, This is sediment at the bottom of the tooth. Note the rod-like structures indicated by the white arrows. They are sedimentary particles. Scale bars: A equals 10 mm; B, C equal 200 μm; D equals 1000 μm.

Why was this study important? Although only one tooth was analyzed, this study remains important. The scientists were able to find out the internal structures of the Prognathodon tooth and hypothesize about the diet (like how it could have eaten turtles) and the body temperature of the animal in life.      

Broader implications of this study: This study establishes that a number of tests can be used to determine the diet and body temperature of ancient animals by just using their teeth. Even without the full fossil, teeth can inform us of many different things about the life of the animal. In the future, even partial samples can be used to analyze aspects of ancient animals’ paleobiology, helping to form a more complete picture of their lives.

Citation: Megan R. Woolley, Michael W. Caldwell, Kevin Rey, Romain Amiot & Anusuya Chinsamy (2024) A multi-method approach to deciphering the paleobiology of a mosasaur from South Africa, Journal of Vertebrate Paleontology, 44:6, e2486069, DOI: 10.1080/02724634.2025.2486069

Characteristics of the front limbs of the flying dinosaur, Microraptor

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Forelimb feathering, soft tissues, and skeleton of the flying dromaeosaurid Microraptor

By: Maxime Grosmougin, Xiaoli Wang, Xiaoting Zheng, Thomas G. Kaye, Matthieu Chotard, Luke A. Barlow, T. Alexander Deccechi, Michael B. Habib, Juned Zariwala, Scott A. Hartman, Xing Xu, and Michael Pittman

Summarized by: Summarized by Brooke Sacks, an undergraduate student pursuing a B.S. in Biological Sciences at Binghamton University. Upon graduation this spring, she will be pursuing a master’s program before heading to law school. When she is not studying paleontology, Brooke enjoys playing golf, tennis, and traveling. 

Data being used: Researchers analyzed the front limbs, or forelimbs (including the bone structure, soft tissue, and feathers), of ten new Early Cretaceous Microraptor specimens from northern China, stored in the Shandong Tianyu Museum of Nature. The researchers obtained measurements of the bone structures, observed the preserved soft tissue, and measured the feathers for classification; this data was  compared to that of  previously studied specimens, including early flying dinosaurs (such as Anchiornis, Archaeopteryx, and Confuciusornis), as well as modern birds. 

What was the hypothesis being tested? The purpose of the paper is to investigate the feathering, soft tissues, and bones of the Microraptor forelimb. The researchers aimed to 1) reconstruct an accurate model of Microraptor forewing feathering, specifically including the layering of the different types of feathers, 2) observe skeletal characteristics (the thickness and length of pectoral girdle, humerus, ulna, radius, carpals, metacarpals, and phalanges- the bones from the arm closest to the shoulder to the wings) that may provide a deeper understanding of the organism’s flight capabilities, and 3) perform tests on forelimb soft tissues to uncover the functionality of the Microraptor forewing. Overall, this study provides insight into avian evolution of flight, which has not previously been fully known due to limited understanding of Microraptor anatomy. 

Methods: In this study, the researchers used white light and Laser-Stimulated Fluorescence, which is a procedure used to cause fluorescence around the surface of the body tissues and illuminate the specimen for visual analysis. Specifically, this was used to illuminate areas of interest on the specimens: the soft tissue, bones, and feathers. The use of Laser-Stimulated Fluorescence allowed researchers to discern otherwise hidden details in feathers which aid in the classification of the different feather layers. Thirty-second time-exposed images were taken using a Nikon D810 DSLR camera to ensure high-quality photos to study, and the photos were processed for review using Photoshop CS6 software. Additionally, scientists took  measurements of bone lengths and feather lengths, as well marked the number of preserved feathers broken down by type. Microraptor specimens and similar early flying dinosaurs  (Anchiornis, Archaeopteryx, and Confuciusornis) were studied in this comparative analysis. These measurements were compared across all species by uniform standards. 

Results: This study further organized previously discovered layers of feathering (called coverts; see Fig. 1 for details about the layers)  by distinguishing these into primary greater, secondary greater, median and lesser coverts, all of which have different roles in the process of flying (Fig. 1). As a result of analyzing its wing structure, it is clear that Microraptor exhibits characteristics consistent with modern birds that fly continuously at high-speeds–its V-shaped wings and lack of wingtip slotting (i.e. the separation of outer feathers that lets air pass through when flying) are commonly associated with reduced drag and prolonged flight capabilities. Regarding the soft-tissue analysis, Laser-Stimulated Fluorescence revealed the outline and surface texture of Microraptor, indicating this species had a strong arm with tissue covering. Taken together with its wing morphology and bony/soft tissue anatomy, it may be supported that this species, Microraptor, was likely an aerial hunter that possessed a diet typical of modern falcons. Researchers also found that the claws of Microraptor were more curved than other related species. 

A figure depicting a Microraptor forelimb facing upward with feathers extending from the forewing outward respectively in layered tiers. Each layer (marginal coverts, lesser/median coverts, secondary greater coverts, secondary feathers, primary greater coverts, and primary remiges) is a different color on a blue-purple scale to depict the distinct layers in this anatomical reconstruction. The dark blue layer closest to the forewing bone and just covering the forearm is the longest layer representing the marginal covert. The next layer, the lesser/median coverts, is two tiers stretching the entire length of the forewing - these feathers are longer in length as compared to the marginal coverts. The secondary greater coverts are positioned closer to the talons while the secondary feathers cover an area closer to the elbow joint. The primary grater coverts and the primary regime layers are both on the outermost portion of the forewing with the long primary regime feathers taking a V-shape. The scale bar represents 50 mm, and the anatomical model is approximately 5 of the scale bars (or 250 mm).
Figure 1. Model of Microraptor forewing feathering by layers. The wing has layers as follows, moving outward respectively: marginal coverts, lesser/median coverts, secondary greater coverts, secondary feathers, primary greater coverts, and primary remiges. These terms are classifications of the layers of feathering on this anatomical model of a forewing. The marginal coverts and the lesser/median coverts makeup the portion of the wing closest to the arm. The secondary greater coverts and the secondary feathers make up the middle tier – these layers contain feathers longer than that of the marginal/lesser coverts. The primary greater coverts and primary regimes are the outermost feathers making up the tip of the wing. The primary feathers form a V-shape, while the secondary feathers projecting from the ulna, which is on the pinky side of this anatomical model, are fan-shaped. The V-shape of the outermost layer (primary regimes) indicates that Microraptor was likely a fast-moving bird of prey because this shape is optimal for reducing drag thus allowing for faster flight. This data is an anatomical reconstruction of Microraptor feather layering derived from the analysis of 14 specimens. The black scale bar is 50 mm.

Why is this study important? This study is significant because it draws connections between anatomical features and functional applications. In this study, the V-shaped primary regimes on the outermost feather layer indicate that this species was likely a fast-flying hunter, which had not been previously known. From this, we can draw conclusions about their diet as likely hunters, and this methodology can be applied to learn more about other avian species. Additionally, because the claws of Microraptor were so curved, researchers think that  this species could have been climbing trees during their lifetime. 

Broader implications beyond this study: By comparing this species of flying dinosaur  to both modern and prehistoric organisms, scientists can gain a deeper understanding of avian evolutionary trends, as well as how this particular species once flew and interacted with their environment. Future studies may focus on how Microraptor hindwings, as opposed to their forewings, compare and contrast to the findings discussed in this study. This study adds to how the process of flying evolved in birds over the past ~ hundred million years.

Citation: Grosmougin, M., Wang, X., Zheng, X., Kaye, T. G., Chotard, M., Barlow, L. A., Deccechi, T. A., Habib, M. B., Zariwala, J., Hartman, S. A., Xu, X., & Pittman, M. (2025). Forelimb feathering, soft tissues, and skeleton of the flying dromaeosaurid Microraptor. BMC Ecology and Evolution, 25(1). https://doi.org/10.1186/s12862-025-02397-5