Ediacaran Reorganization of the Marine Phosphorus Cycle 

Thomas A. Laaksoa, Erik A. Sperling, David T. Johnstona, and Andrew H. Knoll

Summarized by Makayla Palm

What data were used? The purpose of this study was to measure if changes in the phosphorus cycle were linked to changes in the chemical composition of ocean water hundreds of millions of years ago. The phosphorus cycle is the study of the element phosphorus as it travels from deep-sea storage and rock formations into organic life, and back to the seas again. Why study phosphorus in the first place? Phosphorus is essential to life because it is an important component in DNA and RNA structure. Specifically, at the end of the Ediacaran (~625–542 million years ago or mya), there was a jump in complexity in the fossil record (i.e., life became more complex) found in the transition from the Ediacaran to the Cambrian (~542–485 mya); it may be the case that this change in phosphorus can help us understand the changes to life on Earth during this time. Previously collected phosphorite samples (rocks with a high phosphorus content) and newly found samples from the Doushantuo Formation (Ediacaran, China) were used in this study. These phosphorite samples were examined for the following: evaporite volume, strontium isotope ratios, and content of phosphate. Changes in these samples’ ratios and concentrations allow researchers to hypothesize the impacts on water and life during the Ediacaran. Originally, scientists thought the changes may have been due to increased weathering of rocks, but researchers in this study hypothesized that there may have been more to the story. 

Methods: Researchers from this study hypothesized that a change within deeper Ediacaran ocean chemistry may be the cause for the phosphorus cycle change. They tested this hypothesis by using the variables collected (e.g., isotopes) in an equation that measures the possible effects of the phosphorus evaporite remineralizing into phosphorite (typically how phosphorus is stored in the ocean) This equation measures the amount of phosphorus taken out of the storage bank by measuring the fraction of total organic phosphorus that is removed in relation to the amount of phosphorus that reverts back to its original form in the storage bank. 

Results: The changes in ocean chemistry can be found on the atomic scale, where there are electron acceptors (also known as oxidizers) and electron donors (or reducers). The ocean, having been in a state of consistent reducing reactions, may have shifted to have more oxidizers, which would have increased remineralization – specifically, phosphorus remineralization. This remineralization would explain the difference that eventually modified the Ediacaran phosphorus cycle to the modern-day phosphorus cycle. In order for phosphorus to reduce, something needs to accept its electron. In the absence of oxygen (which early Earth was lacking in for billions of years), research indicates sulfate may be a suitable candidate. Samples of sediment did not indicate a change in phosphorus content, so the hypothesis was not supported. This means that the phosphorus was likely staying within the same system and being removed. The phosphorus cycle, similar to the water cycle or carbon cycle, describes the formation, use and recycling of phosphorus from the oceans, to land, and back to the ocean. The data from this study indicate that upwelling, the mixing of nutrients from the bottom of the ocean back to the top, is the reason for increased phosphorus. Upwelling can be caused by deep water currents coming into contact with continents, where cold, nutrient rich water is propelled closer to the surface and warms. The increased upwelling makes sense in the phosphorus cycle because of the extra circulation happening, which would explain the increased presence of phosphorus without an added source of the element. 

Why is this study important? This study aims to see why the change in phosphorus occurred to better understand the geologic context that precedes a big change in the fossil record. There is a large jump in complexity from Ediacaran to Cambrian organisms, and ocean chemistry (changes in phosphorus levels in this case) may have had something to do with that. The cycling of phosphorus because of upwelling, influenced by continental placement, could have been a driving reason behind these big changes, ecological and evolutionary. 

Big Picture. This study proposes a mechanism for the change in the phosphorus cycle that is observed between the phosphorus cycle today and the phosphorus cycle of the Ediacaran as we know it. Many questions still exist as to how oceans have changed through geologic time and this study provides an important piece to the puzzle. Understanding changes in ocean chemistry, too, better helps scientists understand how life evolves in response. 

Citation: Laakso, Thomas A., et al. “Ediacaran Reorganization of the Marine Phosphorus Cycle.” Proceedings of the National Academy of Sciences, vol. 117, no. 22, 2020, pp. 11961–11967., https://doi.org/10.1073/pnas.1916738117. 

Synchronized Moulting Behavior in Trilobites from the Cambrian Series 2 of South China

Alejandro Corrales-García, Jorge Esteve, Yuanlong Zhao,  and Xinglian Yang

Summarized by Makayla Palm

What data were used? Slabs of trilobites found from Cambrian-age rocks in South China were discovered in large clusters of several hundred individuals. There were several species represented within these clusters. Were these full trilobites? These fossils did not have a cephalon, or a protective head “shield” that concealed sensory organs, indicating they were molts, or leftover exoskeletons that had been shed off after a molting cycle (much like modern lobsters and tarantulas, which belong to the same phylum as trilobites, Arthropoda). All of the trilobite specimens were measured; scientists planned to use this data to test the hypothesis that these specific taxa, or groups of trilobites, had the same molting patterns as other members of Arthropoda. 

Methods: Scientists recorded measurement data to estimate average specimen size for each species. Researchers performed other data analyses, as well, such as: if different species were clustered together (or not), the orientation of the trilobites, or the way they were facing (e.g., – dorsal, or back, up or down) to learn more about how they were buried, and how differently the exoskeletons had molted, by observing how they deviated from a typical, complete trilobite.

Results: The sizes for all the species were all relatively small, which is evidence to support the idea they had gathered to molt for protection. If they had clustered together for reproduction, various sizes would have been found together. The smaller sizes indicate these may have been juveniles that stuck together for strength in numbers, which is observed in modern-day arthropods. The researchers observed all of the previous molting patterns found in other trilobites in these four trilobite species, confirming a wide variety of species molted in similar ways. They also observed that each species was clustered together and they had not intermixed with one another. The fact that these species did not intermix implies group synchronization, which is found in extant species of arthropods as a defense mechanism. It is inferred that these trilobites coordinated their molts in order to protect themselves during the vulnerable process of molting, which leaves their softer insides more exposed to predation until their new exoskeleton hardens.

Why is this study important? Several different trilobite types in Cambrian strata were found clustered together, but the fossilized remains weren’t complete trilobites. These were molts or leftover exoskeletons they had outgrown and shed. Molting is a common behavior in living arthropods today, and there are certain ways these creatures can molt. Several of these molting patterns have been described and documented previous to this study in other trilobites, and this study expanded on knowledge of molting patterns. This study also shows evidence that trilobites may have worked together in synchronized molting as a protection mechanism.  

The big picture: Fossils like these preserved here, along with modern analogs, can help us understand more about the behavior of long-extinct organisms.  Evidence from extant species of arthropods today has shown groups of species molt together as a defense mechanism, and the hypothesis of this paper was that the four tested groups of trilobites did the same thing. By finding the different species separated in different groups with various molting patterns, the researchers were able to conclude these trilobites likely synchronized, or coordinated molting together in groups. 

Citation: Corrales-García, A., Esteve, J., Zhao, Y., & Yang, X. (2020). Synchronized moulting behaviour in trilobites from the Cambrian Series 2 of South China. Scientific reports, 10(1), 1-11.

Locomotory Behaviour of Early Tetrapods from Blue Beach, Nova Scotia, revealed by microanatomical analysis

Kendra I. Lennie, Sarah L. Manske, Chris F. Mansky and Jason S. Anderson

Summarized by Makayla Palm

What data were used?  Previous research has analyzed possible moving mechanics for the first tetrapods that lived on land (i.e., a four-limbed vertebrate), but most of the conclusions were made in inference, like by analyzing footprints. The researchers of this study aimed to find more direct evidence of how these early reptiles like Tiktaalik or Ichyostega moved in order to determine what lifestyles new fossils from Blue Beach, Nova Scotia had (aquatic/land). In order to test their hypothesis, they studied the limb bones of the new fossils and living creatures like cats and platypi in order to observe how these limb bones adapted to the stresses of gravity and hitting solid ground. The scientists used 3D scans of bones from both the modern and the fossil tetrapods; the living ones had a range of lifestyles from aquatic to terrestrial, for better comparison to the fossils.

Methods: The researchers took 3D scans and measured the volume of limb bones from eight extant (or living species) and five extinct species (the fossils from Blue Beach, Nova Scotia). This information would give them the ability to tell how, or if, these creatures walked. The extant species were studied in order to observe how and where muscles were stressed during walking (and what clues that left behind in bone) in living creatures to find what patterns to look for in the fossil specimens; this created what is called a compactness profile. The compactness profile summarizes how the different tissues in the bones react to stress over time by observing the amount of trabecular tissue in a certain part of the limb bone. Trabecular bone is a kind of bone tissue that is made of tiny plates meshed together. The trabecular tissue arranges itself where the bone experiences the most stress; this is the pattern being observed in the compactness profile. The bones from each specimen were digitally sliced in a cross-section to observe the internally visible trabecular bone. The researchers observed the trabecular bone in extant species first because their moving mechanics are known. Once they established the pattern of where the trabecular bone was in extant species, they applied it to the extinct species to determine their moving mechanics.  

Results: The trabecular bone’s location shows where the most stress is being absorbed in the bones (think of swimming and the different muscle groups used in contrast to walking- a long walk and a long swim will leave one sore in different ways.) The study shows different stress in the trabecular bone across taxa, depending on if the creature was aquatic or land-living. They concluded that the aquatic species had trabecular bone in the midshaft, or middle of the bone because they would pump their legs while swimming. Terrestrial, or land-based tetrapods, had trabecular bone around the two ends of their femurs, indicating they walked. Some of the fossil tetrapods had less dense trabecular bone than some of the extant species, but it was at the ends of the limb bone; researchers concluded these fossils would have lived a semi-aquatic life (a modern alligator is semi-aquatic, for example). Based on the results of this study, it is likely that the Blue Beach tetrapods represented a range of different lifestyles, from fully aquatic, and semi-aquatic, to fully terrestrial, as all of the patterns of trabecular bone described above were found in the different taxa. 

Why is this study important? The study of tetrapod locomotion, or movement mechanics, reveals how the earliest known walking creatures lived and moved. Previous research used proposed ideas on locomotion by inferring muscle and ligament placement on the limb bones of the tetrapods. This study uses direct evidence by looking at how the limb bones react to stress to determine how these creatures moved in various environments. 

The big picture  Researchers are using tissue evidence in order to better understand how the earliest walking tetrapods walked. The tissue, or trabecular bone, helps researchers see direct evidence of walking, rather than relying on inferred information about soft tissues. The analysis of trabecular bone is direct evidence for locomotion because it is re-arranged by stresses from gravity. The ability to observe these changes in soft tissue depending on lifestyle is a definitive classification of lifestyle for these early risers. Rather than saying “these creatures had the ability to walk”, the researchers are saying, “these creatures did walk.”

Article Citation: Lennie, K. I., Manske, S. L., Mansky, C. F., & Anderson, J. S. (2021). Locomotory behaviour of early tetrapods from Blue Beach, Nova Scotia, revealed by novel microanatomical analysis. Royal Society open science, 8(5), 210281.

The megaherbivore gap after the non-avian dinosaur extinctions modified trait evolution and diversification of tropical palms

Renske E. Onstein, W. Daniel Kissling, and H. Peter Linder

Summarized by Makayla Palm

What data were used? Qualitative data from modern palm tree fruit, phylogenetic data, and palm tree fossils are used in order to observe changes over time in the taxon Arecaceae, or the palm tree, from the Paleogene Period. After the end-Cretaceous extinction that wiped out the non-avian dinosaurs, mega-herbivores, or any herbivore larger than 1,000 kg ( ~2200 lbs), were nowhere to be found. For the most part, small mammals were left foraging for food, and angiosperms (flower-bearing plants) were able to catch a break. The combination of mammalian seed-spreaders and lack of large herbivores preying on angiosperms (palms in this case) meant that the plants were able to increase in numbers without worrying about defenses. These furry seed-spreaders (small animals that pooped out their seeds) were still spreading, allowing plants to grow and didn’t evolve many defense mechanisms like rough leaves or spines. The researchers hypothesized that they would observe three things about palm diversity in the fossil material from this time: the origin of plant armature (or defense structures like spikes) in the Cretaceous Period because of many large herbivores, the decrease in armature during the Post-Cretaceous Paleogene Megaherbivore Gap (PMHG), and the change in fruit size over time as the plants were able to diversify. 

Methods: Measurements of the palm tree fruit fossil material were taken in order to compare how fruit size changed over time within the megaherbivore gap and observations were made on when these changes in size happened, which supplemented the phylogenetic analysis. Living palms were observed in modern habitats, as were  their interactions with larger herbivores of modern times to better understand how the fossil palms may have interacted with herbivores from the Paleogene.

Results: The hypothesis that the first armature appeared in the Cretaceous was confirmed by fossil material, which indicates an increase in defense likely due to megaherbivores. The armature of plants with larger fruit decreased over time, which also supports the hypothesis of losing these defense structures over time with less predation. Despite the disappearance of megaherbivores in the end-Cretaceous, fruit size stayed relatively large (above 4cm). Plants with larger fruit diversified on a constant scale over time, whereas plants with smaller fruit decreased in diversity, counter to the second hypothesis. Overall, some hypotheses were supported, and some were not. 

 Why is this study important? A lot of end-Cretaceous Period studies focus on the end of the dinosaurs, what caused the mass extinction, and how the age of mammals began. This study shows a different perspective on a well-studied time period by using a combination of paleobotany and vertebrate paleontology, and observing how the absence of large herbivores affected how ancient palm trees changed ecologically. This documented diversity opened new doors for angiosperm evolution and led to an increase in forests, setting the stage for the next era of geologic time in North America, the Cenozoic. 

The big picture: The Paleogene megaherbivore gap is a time in geologic history where the absence of large herbivores after the non-avian dinosaur extinction greatly affected ecosystems and the change in the landscape to more dense forests. The lack of large herbivores to eat plants allowed plants to evolve fewer defensive structures and larger fruit, which allowed them to spread farther distances and in greater numbers, because of the increase in seeds. 

Article Citation: Onstein, R. E., Kissling, W. D., & Linder, H. P. (2022). The megaherbivore gap after the non-avian dinosaur extinctions modified trait evolution and diversification of tropical palms. Proceedings of the Royal Society B, 289(1972), 20212633.

A European Giant: a large spinosaurid (Dinosauria, Theropoda) from the Vectis Formation, (Wealden Group, Early Cretaceous) UK. 

Chris T. Barker​,  Jeremy A.F. Lockwood, Darren Naish, Sophie Brown, Amy Hart, Ethan Tulloch, and Neil J. Gostling

Summarized by Makayla Palm

What data were used? Fossil remains of a new theropod dinosaur from Southern England were discovered and excavated over several months’ time. These bones consisted of post-cranial fragments, or the parts of the skeleton below the skull. Most of the vertebrae, parts of the pelvis, and some ribs were identified from this specimen, also known as the White Rock spinosaurid. Measurements were taken of the fragments, and an evolutionary (phylogenetic) analysis was inferred to see where this theropod may fit on an evolutionary tree. 

Methods: Scientists measured these new bone fragments, and over 1,000 characteristics of the fragments were cataloged in a computer and compared to other theropods in a character database. This database categorizes dinosaurs by the features found within their bones, and accounts for the smallest of variations to be as specific as possible. These features also help place the theropod on a family tree by using computer programs that arrange all of the characters to identify which dinosaurs are closely related to one another.  

Results: This theropod’s size and other morphological features indicate that it is likely closely related to Spinosaurus, but may or may not be in the genus Spinosaurus. There is a lot of weathering of the fossil remains, which makes more specific categorization not possible at this time. The presence of canals within the bones suggests that post-death, something began to eat away at the theropod’s bones. Scientists have seen very similar features before in other Cretaceous theropods, and the canals are likely due to beetle pupae that dug their way through these bones after the dinosaur had died. The phylogenetic tree did not provide enough resolution to confirm a more specific group that this specimen belongs to, but the likelihood that it represents a new type of spinosaurid is high. This specimen is not only the first of its kind found in this geological location, but its size rivals all of the known specimens in Europe. 

Why is this study important? This study provides insight into the geologic history of Southern England with the presence of the first known large theropod. First, the Lower Cretaceous geological formations of western Europe have been defined as the origin of the spinosaurids. Secondly, the White Rock spinosaurid appears in the fossil record later than any known spinosaurid on the Island, indicating the presence of spinosaurids to last longer than before. The size of this spinosaurid may have warded off other predators, which might explain why fossils of other theropods have been found this late in other known Spinosaurus– bearing locations. This specimen is classified as a spinosaurid and not a Spinosaurus, because its bones were not preserved well enough to confirm a new taxon of Spinosaurus. More phylogenetic analysis, and the discovery of new material, will provide future insight into its taxonomic placement. 

The big picture: A new theropod has been discovered in Southern England, and its large size and location implies it is not only a new spinosaurid, but also one of the largest theropod dinosaurs in Europe to date. Its presence improves the known range of spinosaurids and may provide new insight into taxonomic variation within the spinosaurids. 

Citation: Barker, Chris T.,  Lockwood, Jeremy A.F., Naish, Darren, Brown, Sophie, Hart, Amy, Tulloch, Ethan, Gostling, Neil J.   “A European Giant: A Large Spinosaurid (Dinosauria: Theropoda) from the Vectis Formation (Wealden Group, Early Cretaceous), UK.” PeerJ, vol. 10, 2022, https://doi.org/10.7717/peerj.13543.

Silurian-Devonian Granites and Associated Intermediate-Mafic Rocks along the Eastern Kunlun Orogen, Western China: Evidence for a Prolonged Post-Collisional Lithospheric Extension

Jinyang Zhang Huanling Lei Changqian Ma Jianwei Li Yuanming Pan 

Summarized by Makayla Palm 

What data were used? The goal of this study was to gain insight into how the Kunlun mountain formation and surrounding area were initially formed. The Kunlun Mountain range primarily has an intermediate and mafic composition, with felsic granite intrusions, or dikes. Dikes are intrusions of magma that cut across previously formed layers and are an indicator of a secondary formation process. Depending on the mineral composition, or silica content, of these dikes (or intrusions) they will be either felsic, intermediate, or mafic, with felsic rocks containing the most silica. There are several kinds of secondary igneous rock formations found in the Kunlun called dikes. If the composition of the dike is different from the surrounding rock, this will provide insight into how the dikes formed in the Kunlun and how it can be explained using plate tectonic theory. 

Granite is a commonly found felsic rock in the Kunlun and is formed intrusively (or underground). The mineral contents of the granite can tell the researchers how fast or slow the magma cooled, which will ultimately help answer the question of how the dikes formed. Within the granite, there were zircon crystals present with radioactive uranium decaying into lead. These ratios were recorded in order to estimate ages within the mountain range to determine when the different magma-cooling events took place. To summarize, this paper uses physical samples of the igneous rocks in the area to study mineral composition and isotope data from these rocks, too. 

Methods: The samples that were collected from different rock types in this area were studied under a microscope in order to observe the composition and individual mineral grains. In plate tectonics, there are two kinds of plates: continental plates and oceanic plates. Granite (felsic) comprises less dense continental plates, while basalt (mafic) comprises a denser oceanic plate. In the Kunlun, the researchers observed several granite inclusions surrounded by mafic rock. The isotope ratios of uranium to lead were recorded and radiometrically dated. These data determine if the different intrusions formed at the same time, or if they formed during several events. This would help support or reject the hypothesis they posed that when the continental and oceanic plates collided, creating the Kunlun Mountains, the edge of the oceanic plate broke while bending under the continental plate (the oceanic plate always goes underneath a continental plate, due to higher density).

Results: The radiometric dating of the granite inside the intrusions (the magma formations added after the formation of the surrounding rock) indicated four different formation events, with the earliest taking place 427-414 million years ago (mya) and the latest from 373-357mya. (For more about how radiometric dating works visit Geologic Time.) The variation in the composition of the rocks (felsic, mafic, etc) indicates a complicated tectonic history; along with the multiple events of granitic intrusions, scientists also found ophiolites (oceanic crust that was pushed onto land during an oceanic- continental plate collision), which indicates that a piece of the oceanic plate was pushed up and broken off during the collision. 

Why is this study important? This study looked to test the hypothesis of a broken oceanic plate’s impact on the formation of the Kunlun mountain range and gain more specific knowledge of its origin. By taking inventory of its intrusive rock formations, getting radiometric dating for these intrusions, and noting the differences in mineral compositions, they were able to confirm their hypothesized four magma events. These events represent different periods of magma formation, which confirms the researcher’s hypothesis about oceanic plate breakage during a collision. 

The big picture: Clues from igneous geology, such as large crystal size, rock type, and mineral composition can give researchers details on how large formation events took place. Isotopes within radiometric dating were used to separate events from one another and place them in chronological order. This particular study answered questions about the origin of the Kunlun Orogen, or mountainous landscapes.

Citation: Zhang, Jinyang, Huanling Lei, Changqian Ma,  Jianwei Li,  Yuanming Pan. “Silurian-Devonian Granites and Associated Intermediate-Mafic Rocks along the Eastern Kunlun Orogen, Western China: Evidence for a Prolonged Post-Collisional Lithospheric Extension.” Gondwana Research, vol. 89, Oct. 2021, pp. 131–146., https://doi.org/10.1016/j.gr.2020.08.019.

Male Mastodon Landscape Use Changed with Maturation (late Pleistocene, North America)

Joshua H. Miller, Daniel C. Fisher, Brooke E. Crowley, Ross Secord, and Bledar A. Konomi

Summarized by Makayla Palm 

What data were used? The tusks from a single male mastodon specimen (the “Buesching” mastodon, housed in the Indiana State Museum) that died in its early thirties were analyzed in two stages of its life (teenage and adult) in order to understand how, as a bachelor, it moved away from its herd and interacted with other adult mastodons in what was likely a breeding ground. The skull and tusks of this particular specimen have scratches, dents and markings likely caused from fighting with other males over potential female mates. These marks inspired researchers to focus on mating behavior; they hypothesized that the place where the mastodon fossils were found was the same location as its summer breeding ground. Scientists also examined modern-day relatives like elephants, which added insight into the following data: isotope changes in both oxygen and strontium and the growth “rings” of the tusks during teenage and adult years, which shed light on how the mastodon might have moved seasonally. 

Methods: In order to test the hypothesis of the mastodon’s seasonal moving in his later years, scientists examined and compared changes in tusk growth throughout its life. The exterior damage on the tusks was observed and recorded to factor into results. The mastodon tusks grew each year by depositing a ring of dentin, which is dense tissue that is bony, similar to what makes up teeth. By looking at the differences in the rings, scientists can determine changes in lifestyle. In particular, to learn about where the mastodon traveled, two different isotopes were measured: one to determine seasonal temperature changes (an oxygen isotope) and the other for change in environment and age (a strontium isotope).

Results: The visible damage observed on the mastodon’s skull is consistent with a hypothesis scientists proposed of males fighting for territory and mates. This happened in seasonal periods of musth, an annual event where male mastodons experienced extra fighting based on increased aggression while on the search for a mate, leading to increased clashing tusks in the height of mating season. The dentin growth deposits show evidence of low nutrition value in the same growth years the male would be expected to separate from the herd. There was also a noticed abundance of nutrients a couple of years later, inferring it had become successful on its own as an adult. Oxygen and strontium isotopic changes in the tusk show that the mastodon traveled to a warmer location around the same time each year; the two isotope ratios indicate a pattern of more frequent visits to its summer ‘bachelor pad’ (or breeding ground) and as the mastodon got older, it was able to travel further from its typical location. 

Why is this study important? A male mastodon perished after fighting to the death for a mate. Its tusks were analyzed for growth patterns and changes in trace isotopes to better understand where the mastodon went, its pattern of seasonal travel, and its behavior throughout its lifetime.

The big picture: This story sheds light on the behavior of mastodons as they matured over time, as well as male behavior displayed during mating season. The quality of the preserved tusks allowed researchers to learn about this mastodon’s teenage and adult life and compare the differences over time. 

Citation: Miller, Joshua H.,  Fisher, Daniel C., Crowley, Brooke E., Secord, Ross and Konomi, Bledar A.  “Male Mastodon Landscape Use Changed with Maturation (Late Pleistocene, North America).” Proceedings of the National Academy of Sciences, vol. 119, no. 25, 2022, https://doi.org/10.1073/pnas.2118329119.

Digital 3D Models of Theropod Dinosaurs for Approaching Body Mass Distribution and Volume

by: Matías Reolid, Francisco J. Cardenal , Jesús Reolid

Summarized by: Makayla Palm 

What data were used? This study picked physical dinosaur models from eight different genera, or groups of dinosaur species, to scan and create 3D computer models. These models were used, alongside measurements collected from previous studies on each genus, in order to infer how these dinosaurs may have hunted, moved, and lived. The eight genera in the study were: Coelophysis, Dilophosaurus, Ceratosaurus, Allosaurus, Carnotautus, Baryonyx, Tyrannosaurus, and Giganotosaurus. 

Methods: Each model was scanned by a 3D printer in order to make a digital image. After the eight models were scanned, data on body length, collected in other studies, was added to the models. information was used in order to calculate body mass, volume, and skull length. These calculations were then used to make three ratios: skull length/body length, surface area/volume, and length/mass. 

Results: The three ratios calculated, skull length/body length, length/mass, and surface area/volume reveal information about these genera that wouldn’t be easily found by just observing the fossils, such as metabolism, eating habits, and overall roles in the ecosystem. The study first looks at the skull length/body length ratio. The larger a skull the dinosaur had, the larger and more expansive their jaws were. This is directly correlated to a higher demand for energy and higher body mass; a large skull was required to take down enough prey to fulfill energy demands. . If a dinosaur had a smaller skull, it was less equipped to take down larger prey, so this limits the kind of prey it had access to. In the case of Coelophysis, the oldest and smallest genus in the study, its skull/body length ratio infers that its small jaws were suited to smaller prey on land, but also small fish. In contrast, the larger theropods, Tyrannosaurus and Giganotosaurus, had the ability to hunt larger prey because of their large skull/body ratio. 

The next ratio observed was the length/mass ratio. This ratio considers differences in body plan that the skull/body length ratio does not. For example, Carnotaurus had a short skull in comparison to the other genera in the study, so it is the outlier in the group. However, the length/mass ratio accounts for its build, which recognizes its ability to hunt larger prey. Similarly, Baryonyx has one of the largest skull/body length ratios, but its long snout shape, similar to modern crocodiles, suggests it fed exclusively on fish and other swimming organisms, rather than large land-living prey. This ratio also sheds light on locomotion possibilities for these theropods. Allosaurus, a mid-size theropod, had longer arms than most other large dinosaurs like Tyrannosaurus. This suggests it may have used its arms when taking down large prey unlike its larger theropod comparisons, which are famous for their seemingly useless arms. 

The final ratio observed in this study is the surface area/volume ratio. This was used to study the efficiency of the dinosaurs to release excess heat, which has strong implications for metabolism. If an organism can release heat efficiently, it can have a higher metabolism, because high-metabolism organisms need that heat release. Researchers found that the smaller the dinosaur, the higher heat release, therefore a high metabolism and vice versa. This is consistent with the study’s findings on feeding habits. Coelophysis preyed on smaller organisms, but was probably able to do so more frequently. Tyrannosaurus hunted larger prey, but most likely needed to rest in between for significant periods of time because of its slower metabolism. 

Why is this study important? This study allows observations of theropod dinosaurs to be made that would not be possible from studying just the bones. This data strengthens previous ideas about theropod behavior, such as larger dinosaurs need more energy and need to hunt larger prey. Therefore, their body structure is reflective of a creature able to take down the kind of prey it needs. This study also provides new information previously not available because of new data about metabolism and body surface area, such as a surface area/volume ratio, which indicates what dinosaur metabolism may have been. 

The big picture: This study of 3D scans of theropod dinosaurs infer information from new data by scanning to scale models. These data allow researchers to compare new measurements like surface area and volume to better understand what dinosaur metabolisms and body plans may have been like, which may confirm or reform what we already know about their roles in their respective environments. 

Citation: Reolid, Matías, et al. “Digital 3D Models of Theropods for Approaching Body-Mass Distribution and Volume.” Journal of Iberian Geology, vol. 47, no. 4, 2021, pp. 599–624., https://doi.org/10.1007/s41513-021-00172-1.