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.

A new fossil freezes a dinosaur and mammal mid-fight

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An extraordinary fossil captures the struggle for existence during the Mesozoic

By: Gang Han, Jordan C. Mallon, Aaron J. Lussier, Xiao-Chun Wu, Robert Mitchell, and Ling-Ji Li

Summarized by: Julia Zottola is a junior undergraduate student majoring in biology with a double minor in Spanish and geochemistry at Binghamton University. After graduation, she plans to attend graduate school for paleobiology and evolutionary biology. Once Julia earns her graduate degree, she plans to conduct research for a museum or to become a professor at a university. When not studying, Julia enjoys reading, knitting, and cheering for Scuderia Ferrari’s Formula One team.

What data were used?: The article is based on two fossils found in a Lagerstätte, or a place with unusually high levels of fossil preservation, in the Yixian Formation (a formation is a mappable rock layer with similar characteristics) in China. The fossils, a mammal and a dinosaur that were buried together, were determined to be from the Mesozoic Era, which lasted from 251 million years ago to 65.6 million years ago. To determine the specimens’ ages, the femur (upper leg bone) length was measured, along with the progress of bone fusion (as mammals age, the separate growth plates in the leg fuse to end growth) in the case of the mammal. Bone fusion was also used in an equation to establish body mass of Psittacosaurus lujiatunensis (the dinosaur) and Repenomamus robustus (the mammal). The body mass (in grams) was then used in an analysis of predation style and predator-prey body mass comparison. Further bone analysis of P. lujiatunensis and the positions the two specimens were discovered in were used to determine if  mammal R. robustus was scavenging or was fighting with the intent to prey on dinosaur P. lujiatunensis.         

What was the hypothesis of the article? This article focuses on predation relationships between dinosaurs and mammals, especially on how mammals may have actively preyed on dinosaurs, rather than solely scavenging. The fossils of the two animals that were discovered tackles the previously published idea that mammals stayed out of dinosaurs’ way during the Mesozoic and that mammals were mostly a source of prey for dinosaurs.

Methods: The dinosaur and mammal fossils that scientists identified as P. lujiatunensis and R. robustus, were found in Lujiatun Member in the Yixian Formation, central China. In order to establish the ages of the two specimens at the time of their death, femur lengths were used in a equation from another scientific article, Erikson et al. (2009), as the paleontologists who wrote this study were not able to take samples for the preferred method, skeletochronology (the process of aging a skeleton using the bones’ annual growth lines). The ages that were calculated were age ranges, not specific ages (e.g. teenager or adult). The dinosaur, P. lujiatunensis, walked on two legs when alive, so scientists used published equations for determining body mass from femur length for other two-legged non-avian (non-bird) dinosaurs. To take potential error from the estimations into account, the scientists performed statistical analyses to determine the range of error, and used the calculated body sizes with the least estimated errors. To determine if the mammal was a pack or solitary hunter, four statistical models/graphs were plotted comparing these calculated body masses in grams of both of the fossil species of other known predators (solitary and pack hunters) and their prey (Figure 1).

The fossil is shown, with the larger dinosaur, P. lujiatunensis, on all fours and the smaller mammal, R. robustus, on the dinosaur’s back. The mammal’s left paw is wrapped around the dinosaur’s jaw while it is biting one of the dinosaur’s ribs. What seems to be a predation attempt is supported by the four graphs that used statistical body mass data from living predators and their prey to determine if the mammal was preying on the dinosaur and, if it was, whether it hunted in packs or on its own (the X axis of the graph was the log-transformed mass of predators, while the Y was the log-transformed mass of prey). Based on the data, three of the four graphs show strong support for the hypothesis that the mammal was a predator of the dinosaur, though the mammal’s hunting strategy was not able to be determined.
On top, the fossil is pictured, with the larger dinosaur. P. lujiatunensis underneath the smaller mammal, R. robustus. Four different types of statistical models (A through D) were used to construct the most probable hunting tactic the mammal species used by comparing the calculated body masses (in grams) of the two species in the fossil. This comparison is shown by the red dot. The mass comparison between R. robustus and P. lujiatunensis is also compared against predator-prey body mass relationships, which are the blue and green dots. The blue dots are solitary predators while the green are pack hunters. The red dot falls in the blue and green shaded areas. These areas are the confidence intervals, which are the degree of certainty a calculated value has of being correct. The red dot is in the 95% confidence intervals, showing a high degree of certainty that the mammal, R. robustus, was in fact a predator of P. lujiatunensis, as was hypothesized from the fossil. This was based on known predator-prey relationships seen in the present, though it was not determined whether or not R. robustus hunted by itself or in packs.

Results: Analysis of the rock in which the fossils were found indicate that it was created by a volcano; paleontologists currently hypothesize that the two animals were swept up in a hot mudslide of debris caused by a volcanic eruption, called a lahar. P. lujiatunensis’s complete skeleton was found intact, with it crouched on its legs and with the mammal on its left top side. It appears to have been an adult, between 6.5 to 10 years of age, and is estimated to have weighed approximately 10.6 kg at its death. R. robustus was a subadult, or a teenager, which was determined by the bone fusion methods mentioned in the previous section. The mammal weighed approximately 3.43 kg, at the time of its death. Scientists determined that R. robustus was preying on P. lujiatunensis at the time of their death. The mammal’s position on top of the dinosaur seems to have been used to subdue the prey; the mammal also died biting two of the dinosaur’s ribs, which is evidence of its role as predator. Due to the lack of bite marks on the dinosaur’s other bones and the entangled position of the two specimens, it seems that this wasn’t a scavenging attempt on a previously dead P. lujiatunensis, but an active attempt to prey on the animal.     

Why is this study important?: This is the first known fossil example that shows active dinosaur-mammal predation interactions. While past specimens have included mammalian fossils with dinosaur bones in their abdominal cavity and vice versa, this fossil is the first discovered “fight to the death” between the two groups. This helps paleontologists learn more about species interactions during the Mesozoic Era (251 to 66.5 million years ago).

Broader implications: Paleontologists can learn more about species’ interactions during the Mesozoic. This fossil discovery also refutes a common misconception about species interactions during what is often called the “Age of Dinosaurs”: that mammals were just small, skittish prey for the dinosaurs to consume. While this is not the first evidence of mammals eating dinosaurs, this is seemingly the first snapshot of clear predation, rather than speculation or scavenging. Predation during that time seems to have gone both ways, rather than placing the role of predator entirely on dinosaurs and that of prey on our mammalian ancestors.

Citation: Han, G., Mallon, J.C., Lussier, A.J. et al. An extraordinary fossil captures the struggle for existence during the Mesozoic. Sci Rep 13, 11221 (2023). https://doi.org/10.1038/s41598-023-37545-8

Extra works cited:

  1. Campione, N. E., Evans, D. C., Brown, C. M. & Carrano, M. T. Body mass estimation in non-avian bipeds using a theoretical conversion to quadruped stylopodial proportions. Methods Ecol. Evol. 5, 913–923 (2014).
  2. Erickson, G. M., Makovicky, P. J., Inouye, B. D., Zhou, C.-F. & Gao, K.-Q. A life table for Psittacosaurus lujiatunensis: Initial insights into ornithischian dinosaur population biology. Anat. Rec. 292, 1514–1521 (2009).
  3. Myhrvold, N. P. Problems in Erickson et al. 2009. Anat. Rec. 298, 489–493 (2015).

New species of spinosaurid dinosaur identified by its vertebrae and upper jaw bone

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A new spinosaurid dinosaur species from the Early Cretaceous of Cinctorres (Spain)

By: Andrés Santos-Cubedo, Carlos de Santisteban, Begoña Poza & Sergi Meseguer

Summarized by: Michael Holowiak. Michael lives in Putnam Valley, New York, and is a student at Binghamton University who is currently pursuing a B.S. in biology. He works in a psychiatric hospital in White Plains, New York. One of Michael’s favorite activities is to go country line dancing every week.

What data were used? Researchers used a newly found dinosaur bones that were found in Cinctorres, Spain from the Early Cretaceous period (145 million to 100.5 million years ago)..  Researchers also modified a dataset from a previous research study (Sereno et al. (2022)) that originally contained 120 cranial (skull) and post cranial (vertebral) features (e.g. orientation, grooves, outlines and shape of bones) of different spinosaurid species and compared their evolutionary relationships. Spinosaurids are large bipedal dinosaurs (heavier than Tyrannosaurus rex) with large arms and long narrow skulls that resemble crocodiles. They are all carnivores, with many features adapted to feed on fish. Researchers in this study added in the missing vertebral characters of Baryonyx walkeri (a spinosaurid species in the Baryonychinae subfamily) and compared 25 cranial and post cranial characters of the new fossil to the dataset. The characters were identified from the preserved bones (vertebrae/upper jaw bone) (Figure-1).  

What was the hypothesis being tested? This study focused on the identification of a new spinosaurid species based on character comparison of the new fossils (vertebrae and upper jaw bone) to known information of others in the clade, specifically those in the Baryonchinae subfamily, which scientists hypothesized the new species may belong to. 

Methods: The fossils of the new spinosaurid were recovered by a separate team within the Arcillas de Morella Formation, which contains rocks deposited during the Lower Cretaceous Period and exposed near Cinctorres, Spain. Scientists created a modified dataset to add in missing information of other species in the Baryonychinae subfamily (like Baryonyx walkeri) to compare the new fossils to. Phylogenetic (evolutionary) analyses were conducted wherein cranial and post cranial characters from specimens in the dataset were matched with 25 characters of the new fossil to identify synapomorphies (shared traits, e.g. synapomorphies of mammals are mammary glands and hair/fur) and autapomorphies (unique traits no other species has) within the tree. Scientists identified the most parsimonious tree amongst all of the trees inferred; the most parsimonious tree would be the one with the simplest explanation of evolutionary relationships (i.e. the least amount of convergent evolution, where features evolve independently in many groups).

Results: The new fossil was determined to be a new species and they named it Protathlitis cinctorrensis. Phylogenetic analyses resulted in over 9.3 million potential trees regarding the relation of the clade, and researchers narrowed these down to find the most parsimonious one. From that tree, researchers identified  the new fossil’s most closely related relatives within the spinosaurids (these were spinosaurids Baryonyx, Ceratosuchops,and Suchominus). Protathlitis cinctorrensis was identified to be a part of the Baryonychinae clade (subfamily of spinosaurids) due to the unique feature of its upper jaw bone; a depression in the antorbital fossa (i.e. the area towards the back of the upper jawbone behind the opening in the skull and in front of the eye socket). However, it was differentiated from other species within Baryonychinae by its combination of unique characters in its caudal vertebrae (the vertebrae of the tail). 

Diagram of Protathlitis cinctorrensis. It has a long crocodile-like skull followed by a large body and long tail. The arms and legs are both large and the size of the dinosaur resembles that of a Tyrannosaurus rex. There is a one-meter scale bar and it suggests they were 10-12 meters in length. The two bones of interest (upper jaw bone/vertebrae) are both highlighted within the skeleton (four vertebrate past the legs towards the tail and upper jaw bone). The phylogenetic tree is also shown. The outgroup (most distantly related) Ceratosaurus is sister to two clades, one containing Allosaurus and the other containing the rest of spinosaurids. One half of the second clade consists of two smaller groups that are both sister taxa (most closely related) to each other; Dubreuillosaurus and Afrovenator (sister taxa), and Torvosaurus and Eustreptospondylus (sister taxa). These four are sister taxa to another clade that consists of Camarillasaurus and 2 more smaller clades. The first consists of Protathilitis cinctorrensis (new species) who is sister taxa to Baryonyx by itself, and Ceratosuchops and Suchomimus (sister taxa). The second smaller clade that is sister to Camarillasaurus consists of Ichthyovenator who is sister taxa to Vallibonavenatrix by itself, and Spinosaurus and Irritator (sister taxa).
Figure 1: The figure shows the bones from the new fossil (Protathlitis cinctorrensis) central to the study highlighted in red at the top; upper jaw bone (maxilla, far left) and vertebrae (on right). The figure also shows the most parsimonious phylogenetic tree generated during data analysis. Protathlitis cinctorrensis (bolded) has one sister taxa clade that contains three species (Baryonyx, Ceratosuchops, Suchomimus) and is a part of the Baryonychinae subfamily. Figure modified from original article.

Why is this study important? This study is important because the discovery of a new species (especially in a group where mostly full skeletons are rarely found) can provide insight into the origins and evolutionary history of the clade. New discoveries can fill in gaps and extend the known phylogenetic tree allowing for a broader understanding of what the time period looked like. The discovery of the new species confirms that spinosaurids had appeared during the Early Cretaceous in Laurasia (the ancient continent consisting of parts of North America, Europe, and Asia).

Broader Implications beyond this study: Finding more fossils of new species in areas that have been researched before enforces the idea that scientists really haven’t scratched the surface of what is out there and that the fossil record is very incomplete. There have been two species of spinosaurid taxa that have been found within the Arcillas de Morella Formation, but there are likely more to be discovered with time that will continually fill in gaps of knowledge of Earth’s past, especially in parts of the world that have been searched less for fossils. 

Citation: Santos-Cubedo, A., de Santisteban, C., Poza, B., & Meseguer, S. (2023). A new spinosaurid dinosaur species from the Early Cretaceous of Cinctorres (Spain). Scientific Reports, 13(1), 6471. https://doi.org/10.1038/s41598-023-33418-2

Stable isotope analysis of Argentinian mammals associated with the paleoenvironment and paleoecology during the Neogene Period (23–2.58 million years ago)

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Paleoenvironment and paleoecology associated with the early phase of the Great American Biotic Interchange based on stable isotope analysis of fossil mammals and new U-Pb ages from the Pampas of Argentina

By: Dánae Sanz-Pérez, Claudia I. Montalvo, Adriana E. Mehl, Rodrigo L. Tomassini, Manuel Hernández Fernández, Laura Domingo

Summarized by: Sophia Licata is an environmental science and geology double major, who has also taken on a minor in biology at Binghamton University (SUNY). She is currently a senior at the university and plans to attend graduate school to study geological sciences. After obtaining her degree, she plans on pursuing environmental consulting as a career. In her free time, she loves playing volleyball with friends, journaling, and spending time outside.

What data was used? Stable isotope data was collected from different fossil mammalian species, including rodents, anteaters, rhinoceroses, camels, and capybaras from Central Argentina during different parts of the Neogene Period (23.03 – 2.58 million years ago (Mya)). Samples were collected from two locations: the Cerro La Bota location and the Arroyo Chasicó location. Zircon mineral samples from these areas were also collected to obtain radiometric ages of the rocks.  

What was the hypothesis being tested? By studying the stable isotope analysis of these mammalian species during the Neogene in Central Argentina, it is possible to gain a better understanding of climatic changes that occurred based on the presence of C3 and C4 plants (C3 and C4 have different photosynthetic pathways, which are indicative of the climatic conditions of their environment. C3 plants are indicative of temperate climates with regular precipitation. C4 plants are indicative of more arid climates that are warmer with little precipitation. In this study, different terms are used to identify geologic stages and ages: “Chasicoan” refers to the Early Miocene (23-16 Mya), “Huayquerian” refers to the Late Miocene – Early Pliocene (11.6-3.6 Mya), and “Montehermosan” refers to the Early Pliocene alone (5.3-3.6 Mya). By identifying the diets of mammalian species during these times, and obtaining the abundances of C3 and C4 plants present then, better conclusions can be drawn about the paleoenvironment and paleoclimate of Central Argentina during the Neogene. 

Methods: U-Pb dating of zircons, which come from sediment that has been eroded and weathered from pre-existing rocks, took place at the LA.TE. Andes laboratory in Argentina. Uranium-238/Lead-206 and Uranium-238/Lead-207 radiometric dating was performed to determine and confirm the maximum and minimum depositional age range of the deposits being studied to ensure that the rocks and fossils being examined are within the Neogene Period. When studying mammals at the order and genus levels, the stable isotope data obtained specifically focused on carbon-13 and oxygen-18 isotopes, and the ratios of the isotopes that were present in the carbonates and phosphates found in tooth enamel samples of various mammals. The ratios of carbon and oxygen isotope allow us to determine what kinds of plants were part of their diets (either C3, C4, or a mix of both). This information provides insight into the presence of different plant species, especially if a region was dominated by C3 or C4 plants, by the amount and types of oxygen and carbon isotopes that were present in the environment at the time. 

Results: After obtaining information about the presence of carbon isotopes in mammals, there is strong evidence that taxa had mixed C3 and C4 diets in the Chasicoan Stage (the earliest), C3 diets in the Huayquerian Stage, and an increase in C4 diets in the Huayquerian-Montehermosan Stages (the latest). More simply put, there seems to have been a change from C3 plant presence in diets to C4 plants, which may indicate changes in climatic conditions through the studied time interval. In the Huayquerian Stage, where C3 plants dominate more, it can be assumed that there were cooler temperatures with generally moderate amounts of precipitation. This would be different from the Huayquerian-Montehermosan Stage where C4 plants seem to dominate. This would suggest that temperatures had become warmer and precipitation levels have decreased. 

Two separate charts adjacent to each other displaying the differences in species based on their diets. Differences in diets are determined by comparing the ratios of Oxygen-18 isotopes to Carbon-13 isotopes. The left chart (A) represents species from the Cerro La Bota location and the right chart (B) represents species from the Arroyo Chasicó location including capybaras, rodents, anteaters, hippopotamuses, camels, and armadillos. Shades of pink, orange, purple, blue, and green are used to represent different species, as well as different shapes for each. Three gray bars of different shades run vertically along the middle of each chart representing the diet enrichment for different species.
Fig. 1. These charts show the different isotopes found in the tooth enamel of different species, which correspond to the type of plant they were eating, C3 or C4. At the top of each chart, the types of C3 and C4 plants are included, with C3 plants on the left and mixed C3 and C4 plants on the right. Chart A (left) represents the Cerro La Bota location, and Chart B (right) represents the Arroyo Chasicó location. The gray bars represent the C-13 values that cut off between a diet dominated by C3 plants and a diet that is a mix of C3 and C4 plants. The darkest gray bar indicates C-13 values for diet enrichment for camels and rhinoceroses, the intermediate gray indicates C-13 values for rodents, and the light gray indicates C-13 values for anteaters and other xenarthrans. In Chart A, all the species seem to be plotting in the same area, in between C3 and C3/C4 diets and showing little diversity. In Chart B, there is more diversity spread between the variation in diets, with capybaras showing some deviation towards a C3 diet.

Why is this study important? This study is important because it provides detailed insight to the past climate and environmental conditions in Argentina during the Neogene. By comparing carbon and oxygen isotopes, it allows us to understand the temperature and precipitation conditions of the region based on which isotopes are more concentrated in the samples.   

Broader implications beyond this study: Studying the diets of different species of different time periods can tell us about the paleoenvironment and paleoclimate. Comparisons can be made about the conditions of the paleoclimate based on what types of plants and fauna were present at the time, like the presence of C3 and C4 plants. Understanding the paleoclimate of this region can help to understand current trends in climate. When the climate in a region changes rapidly, it can be difficult for species, especially mammals, to evolve quickly enough to adapt to a new environment.

Citation: Sanz-Pérez, D., Montalvo, C. I., Mehl, A. E., Tomassini, R. L., Fernández, M. H., & Domingo, L. (2023, November 26). Paleoenvironment and paleoecology associated with the early phases of the Great American Biotic Interchange based on stable isotope analysis of fossil mammals and new U–Pb ages from the Pampas of Argentina. Retrieved September 10, 2024,. 

New fossil discovery reveals the origin of small penguins

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Pliocene fossils support a New Zealand origin for the smallest extant penguins

By: Daniel B. Thomas, Alan J.D. Tennyson, Felix G. Marx, and Daniel T. Ksepka 

Summarized by: Michelle Yu is a biological sciences major with a Korean studies minor at Binghamton University. Currently, she is a senior and plans to attend dental school in the hopes to become a future dentist. Outside the classroom, she can always be found in the dance studio dancing with her hip-hop and K-pop dance teams!

What data were used? Scientists discovered two new penguin fossils from New Zealand that dated from approximately three million years ago (during the Pliocene). The new fossils were found to be smaller than the smallest known penguins today, leading to an investigation to uncover if these new fossils represented a new species of small penguin. To do so, the skull measurements of the newly found fossils were taken and compared to the skull measurements of two existing small penguin species: the New Zealand small penguin species (Eudyptula minor minor) and the Australian small penguin species (Eudyptula m. novaehollandiae).

What was the hypothesis being tested? Although current data shows New Zealand as the likely origination point of the small penguin genus, Eudyptula, its sparse fossil record makes it difficult to confirm its origins and how it may have evolved in the past. Previous to this study, the scientists had found evidence of small penguins dated approximately 126,000 years ago (during the late Pleistocene). However, the new small penguin fossils found in this experiment show that small penguins existed almost three million years ago in New Zealand, marking a significant finding in the history of small penguins and where they may have evolved. To fully explore the evolution of the small penguin genus, this experiment tested the evolutionary and ancestral relationships of the new specimens and living small penguins to confirm their New Zealand origins and how they may have changed over time. 

Methods: Scientists recorded the skull measurements of the newly found small penguin fossils and specimen of the existing small penguin species (some of the major measurements included were: overall skull length/width, nose bridge distance, eye socket length/width). Collected measurements were then used in a program called PAUP* (Phylogenetic Analysis Using Parsimony) which analyzed the evolutionary relationships between the new fossils and existing small penguins to ultimately determine whether the newly found fossils were of the same species as the existing small penguins or if they represented a new species. 

Results: The two new fossils discovered were determined to be a new species of the little penguin genus and were named Eudyptula wilsonae by the scientists who discovered them. The new fossil species was found to have a significantly slenderer skull when compared to the existing small penguin species. However, other characteristics of the skull such as overall shape, size, and other anatomical skull features were found to be almost identical to the existing small penguin species, supporting the idea that they are closely related (Figure 1). Furthermore, because the new fossil specimens were found in New Zealand rocks that are three million years old, the discovery of the new small penguin species marks the earliest date small penguins have been found anywhere, supporting the idea that small penguins likely originated from New Zealand. 

The figure compares the shape of a New Zealand small penguin skull to the newly found small penguin skull fossil. Section 1 displays the skull diagram of an adult New Zealand small penguin with the important parts dotted and labeled, such as the temples, eye sockets, and tip of the beak. Section 2 shows the top and side views of three skulls: 1) adult New Zealand small penguin, 2) newly found adult little penguin fossil, 3) newly found juvenile little penguin fossil. The same corresponding locations of measurements in section 1 are marked on each skull, respectively with colored dots. The dots on each skull are connected with lines to create a point-line map of their skull shape. Section 3 displays the three point-line maps overlapped with one another to show which measurement points of the newly found fossil are similar and different to the New Zealand small penguin. Each skull is around 60–80 mm in length.
Figure 1. This figure compares the skull of an adult New Zealand small penguin with the adult and juvenile skulls of the newly found fossil small penguin. (1) Top and side view of the New Zealand small penguin with significant skull features labeled. (2) Side-by-side view of the adult New Zealand small penguin and the adult and juvenile skulls of the new small penguin fossil. Each skull is dotted with the same corresponding features and are connected to create a skull outline of the measurements. (Yellow = adult New Zealand small penguin, Purple = newly found adult small penguin fossil, Blue = newly found juvenile small penguin). (3) Homologous point diagram: overlapping image of the corresponding feature measurements (i.e. the same feature on each skull) of the three skulls to depict how they compare between the specimens. 

Why is this study important? The importance of this study lies with the discovery that the skull shape and body size of little penguins have not undergone significant changes for at least three million years, despite the immense changes the environment has undergone over time. By comparing environmental data from three million years ago to today, scientists hypothesized that small penguin body sizes had already evolved by this time, with the ability to survive in waters warmer than today. This is significant because it suggests that the evolutionary trait to handle a wide range of temperatures in a small body had developed in small penguins for millions of years. This is important because the maintenance of these traits can further reveal the reasons behind the evolution of character traits such as these not only in small penguins, but also other marine animals.  

Broader implications beyond this study: The findings from this study can aid scientists in uncovering how birds may have evolved during warmer periods, and subsequently, how scientists relate it to what type of features certain marine species may have had during the same time that the new small penguin fossil was alive. Specifically, this finding could aid in the studies of seabirds and how they had adapted to the environment in the past and how they may adapt in the future. 

Citation: Thomas, D. B., Tennyson, A. J.D., Marx, F. G., & Ksepka, D. T. (2023). Pliocene fossils support a New Zealand origin for the smallest extant penguins. Journal of Paleontology, 97(3), 711-721. doi: 10.1017/jpa.2023.30

Why do frogs have the ability to jump?

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Frog limbs in deep time: is jumping locomotion at the roots of the anuran Bauplan?

By: Celeste M. Pérez-Ben, Andrés I. Lires, and Raúl O. Gómez

Summarized by: Ali Waleed is a biology major on the pre-med track at Binghamton University. When he isn’t studying, he likes to train in martial arts or go on hikes.

What data were used? They gathered limb data from both fossilized and modern frogs. For the sampling, they used 826 adult specimens. This comprised 48 species which are extinct. and 411 species which are alive today. They had a variety of living species in order to get an idea of the variation today in locomotion between different species of frogs. 

What was the hypothesis being tested? The goal of this paper was to retest a popular hypothesis which stated that the frog’s modern anatomical structure had evolved specifically for the frog to be able to participate in jumping locomotion. In order to test this, they attempted to construct what the original body plan of the ancestral frog species would have looked like, and then see how that body plan adapted to different environments requiring different modes of locomotion. They decided to revisit this hypothesis because of recent studies which have challenged the jumping hypothesis.

Methods: There was one outlier species that had limb proportions which were different enough from the other frogs for them to remove it from the study. For collecting the data, they measured the limb proportions of each frog. Specifically, they collected measurements on the lengths of the bones of the leg (i.e. the humerus, radio ulna, femur, tibia fibula, and proximal tarsals, as well as the metacarpal and metatarsal arches). The limb proportions themselves were relative to the total length of all of the fore and hind limb bones from each frog species. In the cases where they had multiple individuals representing a species, they took the average of the measurements between the individuals from each species. 

The measurements themselves were taken using a digital caliper, as well as digital photographs with a program called Screen Calipers. Using these measurements, they conducted an evolutionary analysis on the frogs by using the different measurements to determine the overall differences between the species used. Scientists produced an evolutionary tree showing how the major groups are related to one another (Fig. 1). The results of this analysis indicated that among modern living species, there are three categories of locomotion: jumpers, swimmers, or walker-hoppers. The researchers explained that these are generalizations of the many varied modes of locomotion found between different frog species and they assigned each species in the analysis to one of these categories. 

Results: They found that walker-hoppers and jumpers were different in terms of the size of their forelimbs and hindlimbs. The swimmers had limbs of an intermediate size. They found a lot of overlap overall with the swimmers in terms of limb size compared to the other two modes of locomotion. Out of the classifications for different modes of locomotion, they didn’t find one mode in particular which the ancestral frog body plan would have had. The statistical analyses the scientists used in the evolutionary analysis indicated that jumping appeared to be the most likely mode of locomotion for frog ancestors.

This image shows the major groups of anurans (Latin name for frogs). It was shared in the article because it shows evolutionary changes and speciation events between different frog species throughout time. This figure depicts an evolutionary tree, with time periods on the x axis and the different species of anurans (Latin name for frogs) on the y axis. The x axis covers the time periods Triassic, Jurassic, Cretaceous, and Paleogene, from 250 million years ago to the present. The tree begins in the Triassic period with Salienta, the common ancestor on this chart. From there it branches off into Triadobatrichus and the “Frog-like Bauplan” mentioned in the article. It also branches off into Anura at this point which are frogs. From Anura, there are further splits in the tree which are represented by Leiopelmatoidea, and Coatata. In the Jurassic period, the ancestral frog body plan branches off into Prosilarus, Nothobranchius, and Viarella. Also in this period, there are further branches within the Anuran tree depicting the species of Rhadinosteus, Rhinophynidae, Pipidae, Anomocoela, and Neobatrachia.
Fig. 1 The evolutionary relationships frog species through different geological periods. It depicts how modern-day frogs are related to the ancestral frog body plan. It shows where different speciation events occur as well, where the branches occur. Most of the speciation shown on this figure depicts it happening during the Jurassic and Triassic periods. It depicts when certain species are thought to have gone extinct by the length of the branches, as well as various species which are known to still exist today.

Why is this study important? This study was important because scientists can learn about how certain limb proportions in animals can help achieve certain tasks. Perhaps having a certain size of hind-leg is indeed greater for jumping: this would help us identify jumpers from the fossil record more easily.

Broader Implications beyond this study: Overall, they found a variety of modes of locomotion within the various species of frogs, and so they couldn’t state that any mode was used by the ancestral frog body plan. The scientists  hypothesized that this was due to repeated homoplasy, meaning independent evolution of traits over time rather than receiving traits from an ancestral species. Because of this, they suspected that there may not have been a particular mode of locomotion such as jumping which set the ancestral frog body plan apart from other organisms. They conclude the article by saying that future studies should start considering other hypotheses on what set the ancestral frog body plan apart from other organisms at the time. 

Citation: Pérez-Ben, C. M., Lires, A. I., & Gómez, R. O. (2024). Frog limbs in deep time: is jumping locomotion at the roots of the anuran Bauplan? Paleobiology, 50(1), 96–107. doi:10.1017/pab.2023.23

New Australian hopping-mouse fossil could be an insight into mammal conservation everywhere

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Conservation implications of a new fossil species of hopping-mouse, Notomys magnus sp. nov. (Rodentia: Muridae), from the Broken River Region, northeastern Queensland

By: Vakil, V., Cramb, J., Price, G. J., Webb, G. E., and Louys, J. 

Summarized by: Mena Coles-Carruthers is a senior biological science major and environmental studies minor at Binghamton University. Mena is interested in ecology and evolution and enjoys learning new things about science every day. She loves to cook, bake, sing in choir, and hike in upstate New York. She can’t wait to pursue a career in biology and hopes to contribute to our collective knowledge of organisms and how they interact with their environment.

What data were used? Scientists have discovered new Australian hopping-mouse fossils from the genus Notomys. Five jaw and molar samples were found in the Tripot and Beehive Caves in the Broken River Provence of northern Australia. Researchers compared their data from these specimens with descriptions of other hopping-mouse species and museum specimens (from the Australian Museum, the Melbourne Museum, and the Queensland Museum), primarily examining the differences in the teeth, jaws, and body size between the specimens. 

What was the hypothesis being tested (if no hypothesis, what was the question or point of the paper)? The main point of this paper was to determine whether the new fossils were a novel species of Notomys, and to assess what this meant for the conservation of other hopping-mice and mammals all across Australia.

Methods: Rock samples were collected from the cave, then acid-digested in dilute acetic acid and wet-sieved through mesh to recover vertebrate fossils and separate them from the surrounding rock. Researchers extensively described the morphology of the jaw and molars and compared their fossils with museum specimens and descriptions of other species of Notomys available in published scientific research. They also used a regression equation to estimate organisms’ body mass based on their mean upper molar row length (the combined length of three molars), using published data on six Notomys species, along with measurements of the N. magnus samples.

Results: The researchers have determined that the discovered fossils are, in fact, a new species of the Australian hopping-mouse Notomys called Notomys magnus. This novel extinct species likely had a temporal range spanning the mid-Pleistocene to the early Holocene (~781,000–ad10,000 years ago). At an estimated mass of 83.2 g, N. magnus is considered to be a larger-bodied Notomys and is more massive than four of the six species with estimated body masses in this study. N. magnus falls into the critical weight range for mammals, meaning it is particularly susceptible to extinction. Since N. magnus was discovered alongside arid (desert)-adapted taxa, and most Notomys live in dry or desert-like climates, the new species is thought to be arid-adapted or open-habitat adapted. This means it likely had the ability to hyper-concentrate its urine so that it required less water, along with other helpful adaptations.

Two jaw bone fossils side-by-side, each with three molars. The specimen on the left has well-developed buccal cusps compared to the specimen on the right, meaning the cusps on the side closest to the cheek, and this is pointed out in white lettering. The background is black, and white lettering indicates the specimen as “A” and “B.” Scale bars are also provided in white, as well as lines pointing to the teeth, reading “T8-T9.” The total size of the jaw bones is approximately ~15 mm in length.
Comparison of the jaws of the novel species Notomys mangus (A) and Notomys longicaudatus (B). N. magnus has relatively well-defined pits on the molars, while N. longicaudatus has relatively narrow ridges. Scale bars = 1mm.

Why is this study important? Of the ten discovered species of Australian hopping-mouse, eight are considered extinct, vulnerable, near-threatened, or endangered. The newly discovered fossil mouse provides additional evidence that modern Notomys species may be at risk of extinction. The specific reason for the decline of many species of Notomys in the late Holocene (i.e. modern times) is not yet completely understood. This gap in information could be a hindrance on conservation efforts for modern hopping-mouse populations, as well as other mid-size mammals. Scientists are trying to gain as much knowledge as they can using the data they have available, and they are constantly using new information they learn about the past to inform our understanding of the present and future state of mammal conservation. The discovery of this new extinct species has further narrowed the organisms of concern to be larger bodied Critical Weight Range mammals, so researchers can use this to direct funding and research where it may be more needed. Additionally, the finding of this new species has highlighted a gap in knowledge about arid-adapted mammals in northern Australia.

Broader implications beyond this study: Critical Weight Range (35-3500g) mammals of Australia, especially those that are ground-dwelling, are thought to have declined the most rapidly in the last few hundred years. These critters are of mid-range body weight and are especially abundant during the late Quaternary Period. They are thought to be at higher risk of extinction due to the prey preferences of some introduced invasive predators. Some recently found extinct species in this category include organisms such as the Christmas Island Pipistrelle and the Bramble Cay melomyses. This newly discovered species (N. magmus) further validates the idea that Critical Weight Range species are most susceptible to extinction and may broaden the range of previously thought at-risk populations to the tropical north of Australia. 

Scientists think many extinct species of Notomys may have gone extinct due to European colonization of Australia as a response to pressures such as the introduction of non-native predators (like cats and red fox), loss of habitat, and a changing climate. This knowledge, when combined with ecological and genetic studies, could aid in conservation efforts on Australian mammals. However, if conservation efforts are not put in place for Australia’s other mid-sized mammals and rodents, they could also go extinct when they face similar pressures due to recent changes in environments, habitat, and climate. 

Citation: Vakil, V., Cramb, J., Price, G. J., Webb, G. E., & Louys, J. (2023). Conservation implications of a new fossil species of hopping-mouse, Notomys magnus sp. nov. (Rodentia: Muridae), from the Broken River Region, northeastern Queensland. Alcheringa: An Australasian Journal of Palaeontology, 47(4), 590–601. https://doi.org/10.1080/03115518.2023.2210192

Crinoid ecology changes during the Mesozoic Marine Revolution

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Intact stalked crinoids from the late Aptian of NE Spain offer insights into the Mesozoic Marine Revolution in the Tethys

Summarized by: Randolph Kruman. He is a biology major and a sophomore at Binghamton University. He plans to graduate from Binghamton and attend dental school. He loves plants and has many houseplants.

What Data Were Used: Researchers found fossils in the Oliete Formation in northeast Spain’s Maestrazgo Basin. The area contains Aptian-age rocks, an Early Cretaceous age from about 121–113 million years ago. Researchers discovered a bed of 20 intact crinoid fossils (Fig. 1), which is rare because crinoids are made up of thin and fragile parts that break off easily and are held together with soft tissue that often decay before fossilization occurs. The orientation of the crinoid fossils as they were found in the rocks was recorded. Researchers collected the crinoids and coated them in ammonium chloride, NH4Cl, which was used to highlight the detailed features of the crinoids for better study. They also collected oyster shells from the same layer to perform isotope analyses. 

What was the hypothesis being tested: Scientists tested the hypothesis that crinoids shifted their habitat as a result of predation, and not salinity shift, during the Mesozoic Marine Revolution (MMR). The MMR was a huge shift in ecology and types of marine organisms, occurring over the Mesozoic Era, during which many new predators with adaptations like shell crushing emerged. 

Methods: Researchers analyzed the position of the crinoid specimens that they were found in in order to determine information about their death and environment. Also, researchers analyzed crinoid specimens for evidence of predation (by determining if they had any regenerated body parts). They also analyzed the oyster shell remains to determine stratigraphic location and level of abrasion. as well as being analyzed using strontium isotopic analysis, a radioactive isotope, in order to determine information about the environment and piece together factors of why the crinoids stopped living at shallow depths. This is because strontium levels can indicate levels of salinity in paleoenvironments. The presence of well-preserved sponge spicules was noted. They also analyzed the data on water and environmental levels of the Oliete formation to determine the environment and piece together why the crinoids left after the beds were deposited.

Results: Scientists found numerous instances of regenerated or injured arms within the specimens, indicating they were being preyed on. The crinoids were preserved with their bodies in three different arrangements: “starburst-up” (mouth pointed up), “starburst-down” (mouth pointing down), and on the side. A sub position within on the side is the “shaving brush” position, where the arms fold together away from the calyx, which would typically form as a response to high-flow currents. Eleven are in the starburst-up position, two are in the starburst-down position, and eight are on their side (among them, one in the shaving brush position). Analyzing where and how the crinoids were found can say a lot about their environment. For example, the “shaving brush” position is similar to other crinoids, both living and fossil, responses to fast current and sediment-laden conditions, implying the eight on their side were buried alive in a storm and died. Starburst-up also implies they were buried alive and tried to crawl out because that’s how they crawl. These crinoids could crawl, an ability only seen in some fossil crinoid groups. 

Other lines of evidence, besides the crinoids’ positions, point to a storm-dominated area. The crinoids and sponges are well-preserved, even the sponge spicules, implying being buried alive in either low energy muddy environment or high-energy waters. The oyster shells are all broken and abraded, implying high energy constant energy like waves, in contrast to the well-preserved crinoids and sponges. The shells probably came from nearby, meaning waterflow and direction was changing frequently, or storms transported them, again pointing to an unstable environment.

Strontium isotopic analysis on oyster shells indicated high levels of strontium, which is connected to lower salinity levels than was expected by the scientists, suggesting that salinity fluctuations and periods of low salinity was common. In the Oliete formation, sedimentological data from another study by the same researchers indicates that there was a shallow marine environment where crinoids lived in the form of a lagoon connected to the ocean. Notably, though, is that connection to the ocean was on the east side of the lagoon, where coral meadows prospered in the stable environment and low energy lagoon water, but on the other side, farthest from marine circulation, the lagoon was a less stable, high stress, peritidal habitat with frequent fluctuations in salinity, temperature, water flow, and waves, again evidenced by the broken oyster shells. It would not make sense that salinity change was the sole factor that caused the bathymetric change (marine depth change) in crinoids, because even though salinity levels steadily decreased during the Mesozoic, there is evidence that they were adapted to salinity fluctuations. This contradicts the commonly held hypothesis that crinoids shifted their habitat to the deeper ocean to escape the change in salinity. However, these crinoids from the Oliete formation have regenerated/injured arms, meaning they were preyed upon by predators. Other fossils found in other studies in the deeper ocean do not have the same predation evidence, the deeper sections of sea probably were a safer environment for crinoids to live in, meaning deep-water crinoids survived at higher rates than shallow-water crinoids, eliminating shallow-water crinoids entirely given enough time. It is plausible that predation drove the crinoids bathymetric shift, as a part of the Marine Mesozoic Revolution.

Image of two graphs and a data table. Graph on the left, Figure A, is a stratigraphic diagram showing strata (geologic beds that stack on top of each other with time) thickness and superposition (where the beds are relative to each other vertically) pointing out where the two oyster sample groups and crinoid samples are located. The vertical scale goes from less than 60 meters down on the bottom to more than 75 meters down at the top, and all the strata are drawn next to the scale to show thickness and relative position to the nearby beds. The crinoid bed is pointed out, labeled Lagerstätte (site with abundant fossils), as well as the two oyster beds above and below it. The table, Figure B, shows the levels of isotopic strontium in those oyster samples and the two sample groups’ averages. The columns are which oyster sample, level of strontium, standard error, and average for the two groups of oysters (above and below the crinoid bed). The graph (Figure C) on the right plots normal/expected isotopic strontium level for each time period. Horizontal scale is time, from 113 million years ago on the left to 119 million years ago on the right. Vertical scale is strontium isotope level, from 0.707150 at the bottom to 0.707350 at the top. A line depicting expected isotopic values through time is shown, including standard error buffer area around it, going from the bottom left to top right, showing increasing strontium levels through this time period. Two points are shown, the two averages of strontium levels from the oyster beds, below and above the crinoid bed, are shown, and they are not near the expected values line, being in the top left corner.
Figure A depicts the two locations of the two oyster samples in the Oliete Formation strata. OYS-1 is below/before the crinoid beds, and OYS-2 is above/after the crinoid beds (OYS= oyster). Figure B depicts the levels of strontium isotope in those oyster samples. The numbers are shown in the table as well as in the graph. Its relation to the expected values of strontium isotopes for that time range is far above the expected range. Because higher strontium levels indicate lower salinity, the time of when the crinoid specimens lived had lower salinity levels than normal.This provides evidence against the hypothesis that crinoids fled to deeper waters to escape the salinity lowering during the Mesozoic.

Why is this study important? This study is important because it is a piece of evidence that contradicts the common hypothesis that salinity change and stress from the changing environment is the reason why crinoids left shallow marine environments and are only found in deeper waters today. 

Broader Implications Beyond Study: This study’s findings also contributes to a greater understanding of the Mesozoic Marine Revolution, including information on how widespread predator organisms were, how they affected ecosystems, and how organisms respond to change in general. While crinoids ended up abandoning shallow seas for deeper seas, likely, at least in part, because of predation, other species reacted differently during this time. 

Citation: Álvaro García-Penas, Tomasz K. Baumiller, Marcos Aurell, Samuel Zamora; Intact stalked crinoids from the late Aptian of NE Spain offer insights into the Mesozoic Marine Revolution in the Tethys. Geology 2024;; 52 (8): 594–599. doi: https://doi-org.proxy.binghamton.edu/10.1130/G52179.1

Analyzing the evolutionary relationship between fossil and living billfish

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“Phylogenetic patterns in fossil and living billfishes (Istiophoriformes, Istioiphoridae): evidence from the Central Mediterranean” 

By: De Gracia, C., Villalobos‐Segura, E., Ballen, G. A., Carnevale, G., & Kriwet, J.

Summarized by Cianna Geni: Cianna Geni is a biology major at Binghamton University. She is a senior and plans to graduate in May of 2025. She is currently involved in research with Decker College on fall prevention for older adults in Broome County. When she is not working on her schoolwork, she likes to listen to live music, go out to eat with her friends, and dance. She is involved in the Binghamton University dance club where she performs 5 styles of dance: ballet, modern, lyrical, jazz, and contemporary. 

Purpose of the paper: This study looked at six billfish species from the Mediterranean Sea during the Late Miocene, which was about seven million years ago. The fossil fish were found in southern Italy. The purpose of the paper is to understand the diversification patterns of billfish through time by looking at the evolutionary relationships between fossil and living billfishes. 

Data that were examined: Billfish fossils were collected from the southern part of the Salento Peninsula, province of Lecce, Italy, which is in the south of Italy. This work presents new as well as previously published species. The fossils were studied using linear and cross-sectional measurements of the billfish’s long, sword-like bill, known as the rostrum (Figure 1). The measurements were taken at half (0.5L) and one quarter (0.25L) of the total rostral length (L). The skull, jawbones, and back bones were also measured using previously established methods. To understand how the shape of billfish evolved, the earliest known billfish, known as the Hemingway sarissa, was used as a comparison group. The dataset was previously constructed by De Gracia et al. (2020). It includes information on the physical traits of 105 living billfish from five species, as well as 21 fossils. 

Methodology: A Principal Component analysis (PCA) was conducted on 13 rostral variables to examine the data. A principal component analysis is a statistical technique that reduces the dimensions of a large dataset to make a dataset easier to analyze and understand the total variation between the data. The results from the first PCA were used to estimate the straight-line distances between all specimens. To evaluate the similarity between the fossil specimens with living species. the distance from the fossil and each living individual of the same species was measured. A second analysis was done using the same method, using the 0.5 L region of the billfish’s bill. An interactive Bayesian phylogenetic analysis was conducted to examine the billfish. A Bayesian phylogenetic analysis is a statistical method that tests different possible family trees to determine how species are related to one another. Data on physical characteristics and genetic information was usedfor both living and extinct species. DNA sequences for three genes were used for 13 different living species. A total of 55 physical characteristics were included for all of the species in the genetic dataset, as well as 15 extinct species. 

Results: The scientists analyzed the differences across species using two points on the billfish’s bill, 0.5 L and 0.25 L. A second analysis was run with just the 0.5 L measurements to include specimens that were missing the tip of the bill. The results did not change when the 0.25 L measurements were removed, indicating that the billfish can be examined using only the anterior half of the rostrum. However, if only the 0.5 L measurements are used, some major shape differences are missed. Through the analysis performed, six different billfish species were identified from the fossils found in southern Italy. Four species were new, Pizzikoskerma salentina, Sicophasma macrocanalata,, Makaira adensa, and Makaira cyclovata. It was found that Pizzikoskerma salentina shares traits with marlins and sailfish. Sicophasma macrocanalata was found to have a completely different bill shape that has never been seen in any living or extinct species. The physical characteristics of Makaira adensa were found to be associated with the blue marlin, with a large, oval bill. In contrast, Makaira cyclovata has a robust, depressed bill that changes to a round shape. The phylogenetic analysis used revealed that the billfish family had several distinct groups. They found that some features appeared in early billfish. These features included a round bill, a slim body, and long dorsal fin. Traits like a larger body size, 13 tail bones, and well-developed tail muscles evolved later and are specific to giant marlins. The results suggest that billfish adapted to become larger, and different billfish species can be grouped together based on bill shape.

This image consists of three labeled images. The first image is labeled Image A and shows the skeletal structure of an extinct billfish species. The image is marked with measurements including “TL” for total length, “VSPM” for vertebral span, and “LJFL” for lower jaw fork length. The bottom images are labeled image B and image C. Both images show the fossil skull and long bill of the billfish. Image B shows the skull from the left lateral view, while image C shows the skull from the dorsal view. Various anatomical features are labeled on image B and image C. The features are labeled using abbreviations that point to the location of each feature.
FIG. 1. Image A shows a representation of an adult skeleton of an extinct species of billfish. The linear measurements that were used to calculate the body length and weight of the billfish fossils are shown. Image B shows the fossil skull and rostrum in a left lateral view. Image C shows the fossil skull and rostrum in a dorsal (back) view. The gray shaded bones shown in image A are a representation of the preserved bones in image B. Scale bar= 10 cm.

Why is this important? This study significantly contributed to the understanding of the evolution of the billfish. It is seen in the results of this study that billfish have adapted to become stronger predators. There have been major changes in their overall size, backbones, and muscles, all making them larger and more fit for hunting prey. Understanding the evolution of these traits can give scientists a better understanding of the role that billfish played in past ecosystems and the role they may currently play in the ecosystem. 

Broader Implications: Understanding how the billfish adapted to their environment can help predict how they might respond to future environmental changes, offering insights on their conservation needs. Knowing how the billfish species may adapt and respond to climate change and habitat destruction, for example, can allow for the appropriate conservation efforts to be made. In addition, studying evolutionary adaptations of billfish in relation to other marine species can help us understand the broader evolutionary patterns of marine species. By understanding how other marine predators have adapted to their environment, we can better understand the role environmental factors play in their evolution. This addresses the interconnected roles that marine species have we one another, which can aid in protecting marine biodiversity.

Citation: De Gracia, C., Villalobos‐Segura, E., Ballen, G. A., Carnevale, G., & Kriwet, J. (2024). Phylogenetic patterns in fossil and living billfishes (Istiophoriformes, Istiophoridae): evidence from the Central Mediterranean. Papers in Palaeontology, 10, e1559.

Unique 3D perspective of trilobite anatomy preserved by rapid burial

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Rapid volcanic ash entombment reveals the 3D anatomy of Cambrian trilobites
by: Abderrazak El Albani, Arnaud Mazurier, Gregory D. Edgecombe, Abdelfattah Azizi, Asmaa El Bakhouch, Harry O. Berks, El Hafid Bouougri, Ibtissam Chraiki, Philip C.J. Donoghue, Claude Fontaine, Robert R. Gaines, Mohamed Ghnahalla, Alain Meunier, Alain Trentesaux, and John R. Paterson.

Summarized by Erin Potter: Erin lives in the Binghamton, NY area. She is a lecturer in the Geography Department at Binghamton University, where she hopes to also pursue her Ph.D. in Earth Sciences. Erin holds a Master’s degree in geosciences with a concentration in teaching, as well as a Masters in atmospheric science. She has one daughter, a scientist in the making, and knows the importance of being a role model and a representative of women in science.

What data were used? The authors examined trilobites, which are extinct creatures that lived from 521 to 252 million years ago. They primarily lived in ocean environments and are related to things like the pill bugs alive today. Two trilobite species were retrieved from volcanic ash in Morocco. Authors collected the ash as well. The species are Protolenus (Hupeolenus) and Gigoutella mauretanica which are both from the Cambrian Period, about 538 to 485 million years ago.

What was the hypothesis being tested? The goal of this study was to examine the specific processes of fossilization of trilobites from rapid cooling of volcanic ash as it entered a shallow marine environment, preserving fine details of trilobite anatomy. 

Methodology: The authors used a type of X-ray imaging to capture internal structures from the two species of trilobites. They also assessed the fossilization process of the volcanic ash and the minerals in the ash responsible for the preservation. Three-dimensional images created by the X-ray imaging were analyzed to show the fine anatomy preservation.  

Results: Several intricate features were found, many previously unknown for these species (Figure 1). Among these anatomy features found were antennae and the related appendages (much like other arthropods, like insects have antennae). Appendages for moving and feeding were clearly visible in the X-ray images, including claws. The digestive system–such as the esophagus, intestines, and digestive glands– is preserved with great detail in one of the species. The mouthparts (called the hypostome and labrum) were examined in the 3D imagery. The Gigoutella mauretanica specimen was found to have been preserved with smaller organisms attached to the hard exoskeleton. The rapid burial allowed for these small organisms, called brachiopods (two shelled organisms that were common 538 to 252 million years ago), to be preserved attached to the trilobite specimen. Even soft tissue, like the pedicle (the fleshy attachment structure on the brachiopod) can be seen on the preserved specimens. The ash that was studied showed various sizes and mineral composition. Grain size ranged from larger grains called lapilli to very fine-grained ash. The organization of grain sizes indicated a single event was responsible for this volcanic rapid burial. Minerals that made up the volcanic material included quartz/silica, calcite, and chlorite. The mineral composition around the trilobites (quartz/silica, albite, and iron chlorite) shows evidence of an interaction of the volcanic material with the shallow marine environment that the trilobites would have lived in. 

Panel A depicts the underside of the Protolenus (Hupeolenus) specimen with a long antenna extending from the head. There is a 1 mm scale bar on the image, so the total length is about 10 mm. The head appears as a shield with pointed end extending to half its body length. The body is made up of many segments decreasing in size to the tail. Each segment has a spike-like feature on either end and 2 pointed legs. Panel B shows the underside of the Gigoutella mauretanica specimen. There is a 3 mm scale bar on the image, so the total length is about 18 mm. The head appears as a shield with pointed ends extending to about a quarter of its body length. The body is made up of many segments decreasing in size to the tail. Each segment has a spike-like feature on either end and 2 pointed legs. Panel C is the side view of the Protolenus (Hupeolenus) specimen with the segments and legs decreasing in size to the tail here. Certain features are highlighted in colors here. A blob curving up to the specimen’s back and running from the head to the tail across the top is the digestive system shown in blue. A smaller blob of green is found within the head where the digestive system meets, this is the hypostome and a smaller orange spot behind that is the labrum, both mouthparts. Panel D is the top view of the Protolenus (Hupeolenus) specimen showing the highlighted colored features. The digestive system shown in blue running down the middle of the back. The head contains the green and orange highlighted mouthparts. Panel E is a top angled view of the Gigoutella mauretanica specimen with a 4 mm scale bar. Highlighted in blue are small (slightly less than 1 mm) brachiopods attached to the trilobite, one on the top right side of the specimen and the other 3 on the edge of the left side. Panel F is a zoomed in view of panel E with the 3 closer brachiopods. The 1 mm scale bar indicates these shelled organisms are slightly smaller than 1 mm. The blue highlighted image shows the shell and the fleshy pedicle that attaches to the trilobite.
Figure 1: Trilobite reconstructions showing high resolution, complex features of the anatomy. A, C, and D show different views of the Protolenus (Hupeolenus) specimen. Panels B, E, and F show the Gigoutella mauretanica specimen. Shown are 3D paired appendages, the digestive system and glands (C and D shown by colors), and brachiopods attached to the organism (E and F).

Why is this study important? There is limited information on the internal anatomy of creatures that existed during the Cambrian, 538 to 485 million years ago. The researchers described the fine, soft tissue features of the organisms, something so rare in the fossil record. Typically, the hard parts of an organism, like shells and bones, are what get preserved in greater detail in the fossil record. Animal fossils from this time are often incomplete. This research fills in the gaps of the soft-anatomy features of trilobites in the Cambrian. These preserved features were previously undescribed for these particular species, adding to the current knowledge of trilobite anatomy. 

Broader Implications beyond this study: The way these soft parts of the body have been preserved so well by rapid volcanic ash leads to the possibility of exploring this type of fossilization process further. Perhaps more can be learned about other organisms by looking for other fossils in this source. Ash is known to preserve well, as it does not crush the organism. Volcanic events like the one in this paper involve a pyroclastic flow, typical in large stratovolcanoes. These flows are fast and hot, and result in various sized grains like the researchers describe. This leads to the rapid burial and the ash acts like cement for the organisms trapped. This has been noted in other research papers for other organisms, like an ancient vulture found near Rome, Italy (Dawid et al.). By documenting these cases in volcanic regions, future research can look to these areas for more examples of fine-detailed, soft-body anatomical feature preservation.  

Citation: Abderrazak El Albani, Arnaud Mazurier, Gregory D. Edgecombe, Abdelfattah Azizi, Asmaa El Bakhouch, Harry O. Berks, El Hafid Bouougri, Ibtissam Chraiki, Philip C.J. Donoghue, Claude Fontaine, Robert R. Gaines, Mohamed Ghnahalla, Alain Meunier, Alain Trentesaux, and John R. Paterson.  Rapid volcanic ash entombment reveals the 3D anatomy of Cambrian trilobites. Science 384,1429–1435(2024).DOI:10.1126/science.adl4540

Dawid A. Iurino, Luca Bellucci, Danielle Schreve, Raffaele Sardella. Exceptional soft tissue fossilization of a Pleistocene vulture (Gyps fulvus): new evidence for emplacement temperatures of pyroclastic flow deposits. Quaternary Science Reviews, 96, 180–187 (2014). DOI: 10.1016/j.quascirev.2014.04.024.

New information obtained through analysis of a juvenile fossil reveals that early mammals had a longer life history than modern mammals of similar size.

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Jurassic fossil juvenile reveals prolonged life history in early mammals

By: Elsa Panciroli et al.

Summarized by: Thomas Smith, Senior at Binghamton University

What was the hypothesis being tested? Mammaliaformes were the immediate predecessors of modern mammals. Scientists believed they had a life history that included rapid juvenile growth, early maturation into adulthood, and relatively short lifespans, like modern mammals of that size (156 grams or less). However, examination of two newly found hyrax-like Krusatodon kirtlingtonenesis fossils from the Jurassic Period revealed that this species, and possibly all mammaliaformes did not follow the life history of their modern equivalents. Scientists tested this hypothesis in this study by reconstructing the growth stage and life history of these new fossils. 

What data were used? The two fossils studied in this experiment were of the species Krusatodon, resembling modern shrews, but were likely closer to modern hyraxes, small mammals with elongated front teeth. Despite being a 166-million-year-old Jurassic fossil, an adult Krusatodon fossil was 95% intact; a juvenile fossil (between 7 and 24 months old at time of death) at around 40% intact was also examined for this study. Both samples had their dentition (teeth) preserved well enough to study. The discovery of the juvenile fossil finally allowed researchers to examine the growth patterns and life histories of mammaliaformes, and to compare it to modern mammals.

Methodology: Researchers used an imaging technique called propagation phase-contrast synchrotron radiation x-ray micro-computed tomography to create highly detailed digital, 3D models of both the juvenile and adult skeletons (Figure 1). Researchers compared the adult and juvenile skeletons to each other, and to modern mammals. Researchers also studied the skulls of the samples to determine the stages of dental eruption (the point in which “baby teeth” are replaced by “adult teeth”) that each exhibited.

Results: The juvenile fossil had a partial eruption of its adult teeth at the time of its death. The first two molars on both the upper and lower jaw had erupted, with one of the upper molars in the process of erupting. The remaining teeth were either first generation teeth (i.e. baby teeth) or were unable to be classified. The presumed-adult fossil displayed full permanent dentition, confirming the maturity of the sample. Comparing the eruption status of the juvenile Krusatodon fossil to modern mammals of the same size and age, scientists determined that the Krusatodon developed slower, and matured into its adult form later on into its life; mammals are typically fully matured by the time their last permanent tooth erupts, so the lack of complete dental eruption in the juvenile fossil indicates that even at its relatively older age, it was still far from adulthood. Additional comparisons between the timing of the dental eruption and jaw length suggest that the Kusatodon’s growth patterns are proportional to modern mammals, just at a slower rate. All of these results together indicate that the Krusatodon had a longer life cycle than would be expected of modern mammals in their size range.

The image shows four models of skulls. The bones are color coordinated across all four models. All of the bones are labeled, with arrows pointing from the label to the bone. The dentition on both samples is visible but is unlabeled. Both samples have multiple large canine teeth near the front, with several molars near the back of the jaw. Scale bar of 10 mm is present and suggests that the juvenile skull is approximately 25-30 mm long, and the adult is 40-45 mm long.
The digital models of the juvenile (A/C) and adult (B/D) skulls. A/B are digital scans of the preserved fossils, while C/D have been manipulated for clarity. The juvenile fossil is partially incomplete, but the general shape of the skull is still clearly suggested.

Why is this study important: The typical pattern that mammals follow in terms of life histories, is that as body mass increases, the time to reach sexual maturity and lifespan extend, with longer juvenile phases and a slower metabolic rate. The results of this study disrupt this pattern, with the relatively small Krusatodon having a relatively long youth and lifespan. A species’ growth pattern and life history strategy plays an important role in its survival, both at the organism and population level. This study indicates a massive shift in the knowledge base, suggesting large chunks of information about Jurassic mammals and their life history strategies could be incorrect. 

Broader Implications beyond this study: This finding might indicate that the life histories of other early mammals need to be reexamined. More research on other Jurassic mammal species is needed to determine if this discovery was species specific or if it applies to more Jurassic mammals, but this study could alter what scientists know about the evolution of this pattern in life histories. 

Citation: Panciroli, E., Benson, R. B., Fernandez, V., Fraser, N. C., Humpage, M., Luo, Z.-X., Newham, E., & Walsh, S. (2024). Jurassic fossil juvenile reveals prolonged life history in early mammals. Nature, 632(8026), 815–822. https://doi.org/10.1038/s41586-024-07733-1