Origins of nocturnal habits in modern-day birds: how did modern birds become both diurnal and nocturnal creatures?

Evolutionary Origin of Nocturnality in Birds

by Yonghua Wu

Summarized by: Ana Jimenez Bustos is a geology undergraduate student at the University of South Florida. She plans to attend graduate school in a field related to volcanology, possibly planetary geology. Once she has her degree, she would like to teach and continue to do research in volcanology or planetary geology. Outside of school, she enjoys eclectic, noisy music, her dog Miranda, and loves reading and learning about birds and parrots. 

What data were used? This study compiled data from scientific literature that analyzed genomes, physical characteristics such as eye sizes, ear structure, and anatomy of fossils of ancient and modern birds. Molecular, genetic, morphologic, and evolutionary data was used to determine whether the origin of these nocturnal habits (or the habit of being active at night) was based on a common ancestor or if it evolved along the way. The active and inactive genes (genes that are ‘turned on’ or ‘turned off’ in creatures’ bodies) of eyes involved in light reception and transport were used to try to understand when birds began to live, hunt, and forage in the dark. The study analyzed the compilation of these articles’ conclusions to try to determine whether nocturnality in birds was a trait inherited from a common ancestor or if it evolved side by side in different bird species.

Methods: This study used an array of existing scientific literature to study the evolutionary origin of nocturnality in extant bird species. By analyzing existing scientific literature, the study drew conclusions regarding ancient and modern bird habits.  

Results: It is likely that the nocturnal habits of birds evolved from a common ancestor, representing some of the earliest birds. This hypothesis is supported by the morphology of existing birds, such as large eye to body ratio when compared to other vertebrates because larger eyes allow more light into the retina for clearer nocturnal vision. In addition, these birds have a relatively advanced hearing apparatus that could have evolved from the need to communicate in the dark. The lack of certain organs like the parietal eye in crocodilians and birds (today found only in lizards), which is a light sensitive organ connected to the part of the brain responsible for hormone regulation, suggests that birds had a nocturnal origin, as this organ would have been rendered useless in the dark; the ancestors of birds lost this organ millions of years ago. 

In addition, certain genes that are related to detecting movement (specifically, GRK1 and SLC24A1) are thought to have been present in the common ancestor of birds. These genes would have helped to avoid predation in low-light conditions and support the hypothesis that their ancestor was at the very least both diurnal and nocturnal. 

Activity of birds and phylogeny based on reviewed and published studies. Taxa in red present species with true nocturnality, while taxa in green contain species with occasional nocturnal habits.

Specific adaptations to nocturnal life present in modern birds likely evolved independently from each other. Owls’ asymmetric ears, for example, evolved to precisely locate prey in the dark. This trait was likely not preset in the owls’ ancestors. The deactivation of specific genes related to color vision in nocturnal birds was also likely an evolutionary adaptation to the lack of need for color vision in birds that hunt and forage in the dark. This mutation is present in owls, kiwis, and nocturnal parrots. Some modern birds such as nightjars (Caprimulgiformes) have also evolved a tapetum, which is an extra layer in the back of the eye that reflects light back into the retina. This structure often gives eyes a “shiny” look when flashed with bright lights and can help to give animal clearer vision at night. 

Genetic and morphological evidence suggests that it is possible that birds evolved nocturnal habits in parallel to each other, but it is still possible that the common ancestor of all modern birds was both diurnal and nocturnal. Since the activity patterns of modern birds’ ancestors are still mostly unknown more analysis is needed to understand the habits of ancestral birds. 

Why is the study important? Nocturnality of mammalian creatures is largely understood to have evolved to avoid competition and predation from creatures that lurked during the day, but the origin of nocturnality in birds is not so well understood. Did ancient avian (bird) ancestors also have diurnal and nocturnal habits or was it a trait that was picked up along the evolutionary road? Did this nocturnality evolve in several different species or was it inherited from a single ancestor? Studying extant nocturnal birds and birds that have a combination of diurnal and nocturnal habits may help shed light on the evolutionary history of these behaviors. Understanding these behaviors in birds (or avian dinosaurs) can also help understand the behavior of non-avian dinosaurs like other theropods such as Tyrannosaurus rex the distant past. 

The big picture: This study addresses the origins of nocturnal behavior in birds. It suggests that these habits were present in extremely distant relationships going all the way back to the time of the non-avian dinosaurs. Understanding the habits of modern-day bird ancestors can help understand how ancient birds, and even dinosaurs like Tyrannosaurus or Velociraptor, lived in the past. Previous studies have been absolutist in their approach by classifying ancient birds and their ancestors as either nocturnal or fully diurnal, but the complete story may be significantly more complex and requires more studies to fully understand. Analyzing molecular, morphological, and phylogenetic relationships together can provide a better picture of the origin of these behaviors.  

Citation: Wu, Y. (2020). Evolutionary origin of nocturnality in birds. ELS, 483-489. doi:10.1002/9780470015902.a0029073

Oldest preserved DNA gives new insight on mammoth evolution and speciation

Million-year-old DNA sheds light on the genomic history of mammoths.

By: Tom van der Valk, Patrícia Pečnerová, David Díez-del-Molino

Summarized by: Amanda Gaskins, a senior at the University of South Florida studying geology and astronomy. After she graduates, she plans on continuing her education and obtaining her master’s degree in Geological Oceanography, where she hopes to find ways to combat the effect of global warming on coral reefs. In her free time, she loves to spend time in nature and read mystery novels.

What data were used? A team of scientists made paleogenetic (i.e., studying the DNA preserved in fossils) history by extracting what turned out to be the oldest genome data from the molar teeth belonging to three different mammoth species. 

Methods: To reveal the age and makeup of the mammoth’s genetic data, the authors isolated the DNA from molars found in the Siberian permafrost. Fortunately, the cold temperatures of Siberia reduced the effects of DNA break down throughout time. From there, they used methods that maximized the restoration of short fragments of DNA. The authors utilized biostratigraphy, a branch of stratigraphy that involves correlating and assigning the relative ages of rock strata by using the fossil fauna captured within them, in order to gain an idea of when the mammoths lived. They did this by correlating the fossil remains found at the Siberian site with fossils at locations where absolute dates are available. Moreover, in order to observe how these species of mammoths adapted to their cold environment in Siberia, the authors compared the genomes of the woolly mammoth descendants with those of the ancient specimens. 

Results: Through their experiments, the authors were able obtain ages for each of the three mammoths under speculation; each mammoth specimen is discussed here using a nickname given to them by researchers. The youngest of the mammoth group, nicknamed Chukochya, lived approximately 680,000 years ago. By examining the nuclear DNA that is contained within every cell nucleus of a eukaryotic organism, the team was able to construct a phylogenetic (evolutionary) tree (Figure 1) and discovered that Chukochya actually shares a common ancestor with the wooly mammoth. This confirms the hypothesis that Chukochya was a representative of an early form of the woolly mammoth. Adycha is the second-oldest mammoth of the group, whose life span aged back 1.34 million years ago amidst the early Pleistocene. It lived before Chukochya but is an ancestor to the woolly mammoths. The oldest mammoth of the bunch was dubbed Krestovka, with mitochondrial genome (DNA found only in the mitochondria in the cell) dating confirming that it roamed the earth 1.65 Mya in the early Pleistocene.

Figure 1. This figure is a visual of mammoth evolution throughout time. The three points on the timeline represent the three species of mammoths (represented here by their nicknames) that the authors have sequenced the DNA from.

Why is this study important?: This study provides an excellent example of the potential that ancient paleogenomics have to help uncover the mysteries of evolutionary processes like speciation, in which populations evolve and develop into distinct species. Not much research has been done on deep-time paleogenomics with respect to speciation, as it would require a sample with a long range of genome time sequences, ranging at least a million years old, which the vast majority of fossils do not preserve. The previous oldest genomic data on record was recovered from a horse specimen dating back only 780-560 thousand years ago. The experiment also gives insight on the potential of utilizing DNA as a component of biostratigraphy to help correlate the ages of the rocks and fossils contained within them.

The big picture: Overall, this study shed light on the evolution of mammoths while breaking records in paleogenomic history by uncovering the most ancient DNA sample ever analyzed, pushing our knowledge of genomics all the way back into the Ice Age. The ideas and methods displayed in this experiment will be beneficial in future studies regarding temporal data.

Citation: van der Valk, T., Pečnerová, P., Díez-del-Molino, D. et al. Million-year-old DNA sheds light on the genomic history of mammoths. Nature 591, 265–269 (2021). https://doi-org.ezproxy.lib.usf.edu/10.1038/s41586-021-03224-9

Was it possible for trilobites to live in brackish water?

Were all trilobites fully marine? Trilobite expansion into brackish water during the early Palaeozoic

By: M. Gabriela Mángano , Luis A. Buatois, Beatriz G. Waisfeld, Diego F. Muñoz, N. Emilio Vaccari and Ricardo A. Astini

Summarized by: Abby McAleer, a senior at the University of South Florida.  She is majoring in geology with a minor in geographic informational systems. After graduation she plans to get a job in conservation or become an elementary school science teacher. In her free time, Abby loves to hike and travel with her friends. 

What data were used? Trilobite trace fossils (meaning, the marks left behind by an organism, separate from a body fossil) from the early Paleozoic were used along with stratigraphic sections from four ancient estuary (an area where fresh and sea water mix) sites. The specimens were found in sediment structures located in Northwest Argentina.  

Methods: The methods used in this study were a combination of ancient estuary outcrop identification, analysis of the different sediment types from these outcrops, and an analysis of the tracks, burrows, and trace fossils of the trilobites to compare fully marine trilobite fossils to fossils of trilobites found in brackish waters. The ancient estuary sediments were identified by dividing the valley systems of the Paleozoic Northwest Argentina Basin into 3 estuary zones; inner fluvio-estuarine (closer to the river), middle estuarine, and outer estuarine (closer to the ocean). The ancient estuary sediments were examined in a stratigraphic log, which describes the vertical changes of sediments from bottom to top in a particular area. Additionally, an analysis of how the fossil record of trilobites was altered by sedimentary processes was preformed to create a connection between paleobiology and the stratigraphic layers of the outcrops. Lastly, body fossil analysis was preformed on the trilobites to compare characteristics of offshore and onshore assemblages (deeper and shallower water, respectively). 

Results: The presence of trilobite fossils in ancient estuary environments supports the hypothesis that trilobites could handle a change of salinity and still survive. Although the presence of these fossils in the ancient estuary fossil record does not mean that the trilobites permanently inhabited these regions, it leads us to believe that trilobites migrated to these areas for food and possibly a safe place to nest and spawn. It is likely that the realization that tidal influenced estuaries were not fully marine environments helped us come to this conclusion. Figure 1 illustrates the 4 stratigraphic logs that were taken from the ancient estuaries. In this figure, we can see the expansion of the trilobites from marine to brackish water. 

Figure 1. This diagram represents the four stratigraphic logs of the ancient estuaries. In this figure, we can see the expansion of the trilobites from marine to brackish water through the column.

Why is this study important? This study helps us understand that trilobites made evolutionary changes to be able to handle the salinity change to survive, unlike other strictly marine invertebrates, like echinoderms. We can use the findings of this study to better understand the lifestyles of other marine organisms that lived during this time. 

The big picture: Previously, it was believed that trilobites could not handle salinity changes.  After this study, it has been indicated that trilobites were able to migrate to areas with fluctuating salinity for evolutionary advantages. This has helped scientist understand that assumptions of an organism’s tolerance for salinity may need to be reevaluated to limit future biases in paleontological studies.  

Citation: Mángano MG, Buatois LA, Waisfeld BG, Muñoz DF, Vaccari NE, Astini RA. 2021 Were all trilobites fully marine? Trilobite expansion into brackish water during the early Palaeozoic. Proc. R. Soc. B 288: 20202263. https://doi.org/10.1098/rspb.2020.2263

Molecular phylogeny of an elephant-like species

A molecular phylogeny of the extinct South American gomphothere through collagen sequence analysis

By: Michael Buckley, Omar P. Recabarren, Craig Lawless, Nuria Garcia, Mario Pino

Summarized by: Stormie Gosdoski a student at the University of South Florida. She will be receiving her Bachelor of Science in Geology this December, 2020. After school she plans to join the scientific community and put her degree to good use. 

Data: Phylogenetic trees are created to determine the closest possible relationships between species, like a family tree. The phylogenetic tree containing gomphotheres, a group related to modern elephants, was created by analyzing molecular differences across species and determine the relationships between gomphotheres and true elephants and mammoths. One of the most informative ancient biomolecules that scientists can use for this type of study is collagen, which is the most abundant protein in bones and teeth. 

The scientists sampled four different gomphothere fossils belonging to a genus called Notiomastodon from South America. To reduce extraneous variables that could be present in the dataset, all the fossils were taken from the same location: the Pilauco Site in Osorno, Chile. They were also taken from the same layer of sediment. The layers of sediment on Earth can be read like a book, if no other geologic event has altered their positions. The ability to read each layer like a book gives scientists the ability to date the specimens; 13,650 ± 70 years ago to 12,372 ± 42 years ago. The fossils collected from this site included two root molars, a piece of rib, and a skull fragment.

Methods: The bones had fragments removed from them using a diamond-tip Dremel drill. They were then demineralized in hydrochloric acid (meaning, the scientists removed the minerals from the bones). The collagen was extracted from the solution. It was analyzed by a machine called a Matrix Assisted Laser Desorption Ionization Mass Spectrometry Time-of-Flight Mass Spectrometry (MALDI-ToF-MS). This type of equipment is used specifically to find the protein fingerprint of cells (which, just like our fingerprints, are unique to specific groups). The data collected from these methods were compared and searched for on the Swiss-Prot database for any potential matches to the primary protein sequences that are present in the collected data. This database is a protein sequence database. A potential match in the database would mean the species are more closely related. Once the analysis was complete, the scientists then performed a phylogenetic analysis of the data collected. Meaning, they compiled this information and ran the phylogenetic analysis using these new specimens and animals belonging to the closely related proboscideans, the group including elephants and mammoths, in the database as well, to determine relationships of the organisms in question.

Results: The protein fingerprint spectra of the four specimens collected in this study compared to the spectra of woolly mammoth and American mastodon was determined to differ from one another. The collagen fingerprints were similar, but there were three variations observed in the data (figure 1). At this point, using parsimony, Bayesian analysis, and maximum likelihood (the three methods of determining evolutionary relationships) a range of phylogenies was generated. This range compared three extinct proboscideans (Mammuthus, Mammut (the American mastodon), and Notiomastodon) and other closely related mammals. The results of these comparisons showed a closer relationship between Notiomastodon and Mammut. Meaning, the South American gomphothere has a close relationship to the American mastodon (figure 2).

Figure 1 This figure is the mass spectrometry of the three species. (Top to bottom) gomphothere (green), mastodon (blue), and woolly mammoth (red). This shows observed peak difference in the spectra between the three species.

Importance: This determination of the relationship between gomphotheres and mastodons can change how scientists interpret the relationships of other species in phylogenetic studies. Are there other relationships that need to be changed? How accurate can the scientific community get with the relationships of species? How does this affect our relationship to other species? How can we use this type of analysis to track our own evolution through time? This relationship is but one small portion of a larger question and we can use this to refine what we already know about ancient and present species.

The Big Picture: As scientists, we cannot rely on what our eyes are seeing to determine the relationships between species. Using molecular analyses can give a better idea of how closely related species are to one another. This type of analysis can also show how elephants have evolved and changed through history. This can give scientists a better understanding of the biology of elephants. Who knows- maybe it could lead to predictions of how the species will evolve in the future?

Figure 2 This is the phylogenetic tree that was generated from the analysis with ancient ancestor Paenungulata at the bottom (yellow) and the branch containing the common ancestor at the focus of the study, Proboscidea (pink). The South American gomphothere (green) is the sister taxon to the American mastodon (blue). It further shows the relationships of the other species. On the left is the geologic time scale, which shows when each species was alive.

Citation: Buckley, M., Recabarren, O. P., Lawless, C., García, N., & Pino, M. (2019). A molecular phylogeny of the extinct South American gomphothere through collagen sequence analysis. Quaternary Science Reviews, 224, 105882.

Specifying past climate change through analysis of sand

Paleoclimate and Holocene relative sea-level history of the east coast of India

Study Conducted By: Kakani Nageswara Rao, Shilpa Pandey, Sumiko Kubo, Yoshiki Saito, K. Ch. V. Naga Kumar, Gajji Demudu, Bandaru Hema Malini, Naoko Nagumo, Rei Nakashima, Noboru Sadakata

Summarized by: Scott Martin, a student studying geology at the University of South Florida that will be graduation with a bachelor’s in early December. He plans on working in a government water management position or as a private contractor at an IT firm. He enjoys camping, kayaking, and playing music in his free time.

What data were used: Data from specific kinds of particles, carbon dating, and results of analysis of ancient pollens found within sand columns.

Methods: First, columns of sand were collected from the Kolleru Lake in India. Then, the chemical composition of the sand was identified, carbon dating was done on some of the plant samples and shells within the sand, and the pollen samples within the sand columns were identified. 

Results: It was found that the bottom of the core, which represents about 18,400 years ago, shows signs of being a dried freshwater body that most likely became more arid (i.e., drier) due to a dry spell in the area around that time. We can assume this because in the sand cores, authors found pollen spores from plants that live in arid environments and rocks that are only able to be found in areas where salt water evaporated. The freshwater lakes would have become saltier as they evaporated and eventually start leaving behind evaporite (i.e., rocks and minerals formed during evaporation) deposits. Then, around 8,000 years ago, the climate in the area changed to that of a tidal zone. This is an area that is underwater when the tide is high and above water when the tide is low. The evidence that as found that points to the area being a tidal zone is the color of the sand itself, shells of mollusks that live in tidal areas, and pollen from mangrove trees. At around 4,900 years ago the area changed again and shows evidence of being a completely freshwater area as it is today.

This figure shows the area being studied in relation to the rest of India. The yellow lines are the depth underwater in that spot, so anywhere the line labeled 5 is touching is 5 meters below sea level. The star labeled KK, the triangle labeled DP, and the dots labeled MW and PN are all locations in which sand columns were taken for this study. Note that the yellow lines are not past coastlines but show depth below the current waterline.

Why is this study important?: This study deepened our understanding of the climate of the past in India as well as how the sea level changed in the area as the global climate did. Understanding more of the specifics of how sea level changes with climate allows for more preparation to be done in coastal cities globally. The change in climate that was analyzed during this study is the Earth’s natural cycle of climate change that is in place due to the slight changes in its tilt and path around the sun.

The big picture: The results from this study will allow for climate models being used in the future to be more accurate since the data that was collected covered thousands of years. This allowed for the study of climate change throughout time as well as the potential causes and effects that the changes in climate had on the area. While this study looked at how natural climate change affected the area, human-induced climate change is altering that cycle and the data on how climate change from the past affected specific rehions could better prepare us to handle to affects of the human-driven climate change that is occurring today.

Citation: Nageswara Rao, K., Pandey, S., Kubo, S. et al. Paleoclimate and Holocene relative sea-level history of the east coast of India. J Paleolimnol 64, 71–89 (2020). https://doi.org/10.1007/s10933-020-00124-2

The Change in Tanystropheus Species Due to Resource Availability

Aquatic Habits and Niche Partitioning in the Extraordinarily Long-Necked Triassic Reptile Tanystropheus

By: Stephan N.F. Spiekman, James M. Neenan, Nicholas C. Fraser, Vincent Fernandez, Olivier Rieppel, Stefania Nosotti, Torsten M. Scheyer

Summarized by: Sarah Kreisle, a geology major at the University of South Florida minoring in GIS. She is a senior planning to graduate December 2020. Afterwards, she plans on staying local to further her knowledge in Florida geology and seek a job or internship offering experience in the field. In her free time, she enjoys hiking and kayaking.  

What data were used? Researchers used fossilized remains of Triassic reptiles Tanystropheus hydroides and Tanystropheus longobardicus, most of which were found at the Besano Formation of Monte San Giorgio, Switzerland. 

Methods: Using digital modeling, both T. hydroides and T. longobardicus were re-created virtually, using dislodged and deformed parts from the original skull. After virtual re-construction, these specimens were analyzed for similarities and differences. Additionally, records of stomach contents and skeletal were used to compare and reconstruct diet and environments.

Results: After examination, the two species were found to have similarities between the shapes of their skulls, but diverged in their dietary patterns, evidenced by slight morphological differences in the skull, and skeletal size. In T. hydroides and T.longobardicus they found that its jawbone curved and allowed for the nasal area to sit on the top side of the body. The snout was very flat and plate-like, which is a similar feature to the present-day crocodile. In T. longobardicus, the snout still sits on top of the skull, but is less prominent than T. hydroides. When looking at the shape of skulls in both T. hydroides and T.longobardicus, the snout was curved and flat with their breathing capability on top, in order to swim more efficiently. It was very likely that these creatures were shallow water dwellers since their nasal cavities were not built to endure pressure at great depths. Due to their lengthy necks, they were likely to pounce on food rather than chase after it. A long neck made it much harder to move around with ease. The long necks of the T. hydroides were able to give them an advantage when stalking prey and causing less obvious movements that might alarm the prey. Using the re-creation of the skull, it is observed that the teeth of T. hydroides were more likely to snap at food, rather than suck food from a shell. Scientists can tell from the fang-like teeth, that it was grabbing and holding its prey. In past specimens, there has been evidence of squid-like creatures and fish scales collected from the stomach contents. Conversely, T.longobardicus was more likely to use its shorter teeth for eating soft shelled invertebrates or plants. Their teeth are tricuspid teeth (i.e., teeth with three cusps), which are also present among animals that eat both plant and animal matter. Though T. hydroides is very similar to T. longobardicus, the biggest difference between them is their size. T. longobardicus was less than half the size of T. hydroides. Likely, these creatures were eating different resources available over time, changing the amount of energy they required to survive. It is possible that these two species lived together in the same aquatic environment and deviated from each other in order to survive on available food sources. 

Figure 1 Both species in this picture are depicted to be different structurally, which could mean different food source and possible early competition for food. The skull of T. hydroides shows long curved teeth that would have gripped prey, whereas the skull of T. longobardicus had the short, tricuspid teeth. The tricuspid teeth are much easier to grind food, in both plants and meat. The skeleton of T. hydroides shows a significant size difference from T. longobardicus. The picture in the bottom right corner depicts that the small skeleton of the T. lonobardicus was mature due to the growth lines seen.

Why is this study important? This study is important because it displays niche partitioning, or natural selection driven by resource use. In examining these two species’ tooth alteration, stomach contents, and size difference, we see how very closely related organisms have evolved in different paths due to resource needs. This shift in consumption patterns may also indicate a time period in which competition for food sources was high. We can therefore hypothesize that while these species could have been descended from a recent common ancestor, they have since changed physically and behaviorally due to their environments. 

The big picture: Many other species have been defined by the process of niche partitioning and will most likely continue in the future as our environment readily changes. These changes further cause increased competition in the food web. Change in size of the Tanystropheus could have been due to the amount of energy available to them in food. Teeth and other characteristics of the genus Tanystropheus can explain features of animals in existence today. Learning about Tanystropheus will help us learn more about creatures during the Triassic and surrounding periods. 

Citation: Spiekman, S. N. F., Neenan, J. M., Fraser, N. C., Fernandez, V., Rieppel, O., Nosotti, S., & Scheyer, T. M. (2020). Aquatic Habits and Niche Partitioning in the Extraordinarily Long-Necked Triassic Reptile Tanystropheus. Current Biology30(19), 3889. https://doi-org.ezproxy.lib.usf.edu/10.1016/j.cub.2020.07.025

The increasing rate of extinction today and how it affects our future

Vertebrates on the brink as indicators of biological annihilation and the sixth mass extinction

By: Gerardo Ceballos, Paul R. Ehrlich, and Peter H. Raven

Summarized by: Melody Farley, an undergraduate geology student at the University of South Florida in her final semester. Her goal is to use her degree at the Southwest Florida Water Management District to help with the management of water resources in Florida’s systems. She plans on attending graduate school in a few years, after gaining some work experience to determine what she wants to specialize in. When she is not studying geology, she loves to kayak, hike, and enjoy nature with her fiancé.

What data were used? Data was collected from the International Union for Conservation of Nature (IUCN); specifically, the number of individuals in each vertebrate species, as well as the number of species whose endangerment status has been studied was used here.

Methods: This study used the database material from the IUCN to help classify the species studied based on geographical range and number of individuals. From this, they determined the number of vertebrate species with fewer than 1,000 individuals, excluding extinct species. 

Results: 515 vertebrate species were discovered to have fewer than 1,000 individuals, indicating that they are “on the brink” and very susceptible to extinction. This comprises 1.7% of the total terrestrial vertebrate species. Of the 515 vertebrate species on the brink, more than 50% of these species have fewer than 250 individuals, meaning that there are much closer to extinction. Species on the brink are found to be concentrated in regions with higher human interaction. 543 species have gone extinct since 1900. If the 515 species were to join the 543 species that have already gone extinct, the total extinct species in a 150-year span would be 1,058 vertebrate species. Given the last 2 million years’ background rate of extinction, 9 species would be expected to go extinct in this 150-year period. So, the extinction rate would be 117 times faster than previous background rates.

Figure SEQ Figure \* ARABIC 1: This figure shows the population sizes of 5 groups – Mammalia, Aves, Reptilia, Amphibia, and Vertebrates from left to right, with Vertebrates being an aggregation of the first 4. They are categorized by the number of individuals left in the species. Here, you can see that in all 5 groups, at least 50% of the on the brink species have fewer than 250 individuals.

Why is this study important? This study is important because it illustrates the effects that humans are having on different populations around the world. Extinction rates are much higher now than in geologic history, mostly since the development of agriculture approximately 11,000 years ago. Many of the extinction rates have increased even more since the 1800s as human civilizations have become more advanced, showing that an increased competition for resources have expedited the extinction rates in recent history. 

The big picture: Earth’s systems are all part of an important balance. When a species goes extinct and disappears from an ecosystem, simple maintaining services of this ecosystem can be disturbed. If this happens enough times, we could have the collapse of ecosystems that we rely on for survival. Humans require several things to survive: a stable climate, fresh water, crop pollination, and more. Many of these are made possible by healthy and sustained ecosystems. With the continued risk of climate change, species extinction is a bigger problem now than ever, and it is important for humans to consider the effects of their development, and what this means for the future of civilizations.

Citation: Ceballos, G., Ehrlich, P.R., Raven, P.H., “Vertebrates on the Brink as Indicators of Biological Annihilation and the Sixth Mass Extinction.” Proceedings of the National Academy of Sciences, vol. 117, no. 24, 2020, pp. 13596–13602., https://doi.org/10.1073/pnas.1922686117

Examination of abnormal trilobites across the Paleozoic in China

Abnormalities in early Paleozoic trilobites from central and eastern China

By: Rui-Wen Zong

Summarized by: Matthew Ray, a geology major at The University of South Florida. Currently, he is a senior. He plans to attend graduate school following one to two years of internships in order to further his understanding of Florida geology and desire to make connections. When he is not actively studying geology, he is a fan of sketching and tennis.

What data were used? Researchers used ten trilobite samples with abnormal features and deformations that were located in the eastern and central locations of China dating back to the Cambrian, Silurian, and Ordovician periods. This is notably the first recorded evidence of trilobite deformations belonging to the Ordovician Period that has been documented in China.

Methods: Each of these samples were examined for abnormalities within the pygidia and thoraxes region, otherwise known as the back end and middle portions, respectively. After documenting variables such as rib overlap, breakage shape, and rib retention of these specimens, researchers hypothesized that these features were the results of: genetic malformations,  predatory attacks, or damage self-inflicted through the molting process.

Results: Trilobites are among the world’s most ancient arthropods and are a staple of the Paleozoic Era (542-241 million years ago), during which they flourished. These organisms have three main components: their head, in which most of the essential organs were kept, a mid-torso, and tail piece, named the cephalon, thorax, and pygidium, respectively. Abnormalities are common for trilobites, as seen in many fossilized specimens. Out of the samples discussed in this article, the three most notable abnormalities were: an absence of organs on the exoskeleton, morphological alterations in which ribs either overlapped, fused together, or were stretched, and the presence of breakage patterns in a ‘U’ or ‘V’ shape, suggestive of a predation event. Out of the ten trilobites, six displayed breakages on the outside of the thorax and/or pygidia which are reminiscent of markings inflicted by additional arthropod and cephalopod predation. These attacks are noted to have been non-lethal due to signs of regeneration and shell (see Figure 1). Two of the trilobites are hypothesized to have had genetic deformations, as evident by a stunted rib formation and the unusual arrangement of the surrounding ribs due to overlapping and/or fusion. The remaining two trilobites display issues with these ribs as well; however, these exhibit a large amount of rib retention on their back end (i.e., pygidium) which is considered to be a sign of breakage by tearing during the molting process. That is, their tail pieces were severed from the rest of the body in an attempt to rid itself of the old shell. These results allow a glimpse into the frequency of predation survival in addition to evidence pertaining to preexisting genetic developments and molting “errors” that result in a trilobite’s altered appearance.

Figure 1: 3 Well-preserved Cambrian trilobites (A, D, and G) that have show predation events. Boxes B, E, and G display close-up predation marks made by other organisms leaving a ‘U’, ‘V’, and ‘V’-shaped abnormality respectively. Box C displays a computer-generated model of the ‘U’- bite dimensions and layout. These marks can be used to establish exact predators if bite patterns are recorded and hypothesize community interactions. The black arrow on H depicts evidence of healing.

Why is this study important? This study succeeds in not only showcasing how trilobites can be born with abnormalities, but how some alterations can be formed due to a failure to properly molt or surviving predation events from other organisms. This in turn gives vital information concerning the trilobite’s lifestyle and overall survival rate, as these organisms were able to survive despite these morphological variations within specific regions of the body. The importance of maintaining more crucial body parts is here reinforced as trilobites with abnormalities on the pygidia and thorax were more likely to heal and prosper longer than trilobites that sustained injuries or had genetic deformations to their head, in which their more vital organs are held. Community relationships can be established, too, as the breakage patterns that were able to heal can be compared to those of organisms within the region at that geologic time, thus forming an understanding of feeding habits for others.

The big picture: Overall, this study adds to the information that researchers have about how organisms were able to survive predation attacks and how common genetic mutations occurred in organisms in the past (and how many of these were survivable). While trilobite knowledge across all of the documented times is enhanced, global data referring to the Cambrian Period was a crucial find as these samples were so well preserved, a trend which is unfortunately difficult to see around the world at this time.

Citation: Rui-Wen Zong , Abnormalities in early Paleozoic trilobites from central and eastern China, Palaeoworld (2020), doi: https://doi.org/10.1016/j.palwor.2020.07.003

Argyrolagus – An Extinct Marsupial May Be Different Than We Thought

Paleobiology of Argyrolagus (Marsupialia, Argyrolagidae): An astonishing case of bipedalism among South American mammals

By: María Alejandra Abello & Adriana Magdalena Candela

Summarized by: Mason Woods

Mason Woods studies geology and landscape photography; currently, he is a senior. He is a budding naturalist, finding purpose through a wide range of interests, including paleontology, biology, hydrology and philosophy. When he isn’t studying, he’s sharpening his skills in diving, climbing and hiking, leaving no stone left unturned on his path to understanding and experiencing the natural world.

What data were used?: Two scientists examined multiple specimens of Argyrolagus, a mouse-like marsupial who lived in deserts of Argentina, in order to determine the way that early marsupials might have interacted with the world and evolved. They are potentially one of the first marsupials to have assumed an upright stance and move on two legs instead of four.

Methods: These scientists studied the shape and positioning of the bones to compare this species to other marsupials still alive today in order to determine the true function of the body parts of the animal, through a process called morphofunctional analysis. If the animal moved on four limbs, its body structure would compare to other animals alive today who also move on four limbs. There are clear differences in the length, density, and structure of an animal’s body, depending on how they adapted to interact with their surroundings.

Results: The upper half of Argyrolagus appears to be that of a digger, an animal who burrowed for food, or perhaps to create shelter. Its humerus is short, with muscles that seem to have been allocated towards arm retraction, which indicates it had a strong digging ability. The elbow joint is compact and stable, indicating an adaptive response to the pressures placed on the body when jumping. The forearm bones have muscle attachments which are like that of other digging mammals, and scarring from muscles related to digging, providing further evidence of a burrowing lifestyle . The digits – what we would call fingers – on the animal’s body are like that of other mammals which also were known diggers. The evidence points to the animal moving around by jumping, and probably using its robust upper body for digging as well.

The lower half seems to be that of a jumper. The pelvis is not exactly screaming “jumper” but it does have some adaptations that would help in digging with powerful hip flexion. The hip joint is the clearest evidence, with restricted motion in certain directions, creating a stabilized joint. The femur is adapted well for digging. The knee joint is stable and is shaped for pulling action, like other leaping animals. The ankle joints are strong and with restricted motion, to assist with stability in leaping. Restricted motion prevents injury and the need for muscles to stabilize certain positions and allows the animal to put more energy towards increasing the strength of necessary muscles. 

The leg bones of Argyrolagus. Note the size of its tiny bones . These bones are adapted to a bipedal, digging lifestyle.

Why is this study important?: If we can demonstrate that these animals were likely bipedal, it’s possible that we can determine the evolutionary origin of bipedalism in marsupials, which helps us to complete the picture of how descendants of this animal came to be. We can also use this information to better inform evolutionary analyses and draw conclusions about the close relatives of Argyrolagus. 

The big picture: Argyrolagus was likely a bipedal jumper, which is an atypical gait for most mammals. Jumping has been shown to be efficient for animals of this size, which would have adapted the animal well for life in an arid environment, allowing them greater ranges of motion to escape predators in areas with less vegetation in which to conceal themselves. Each piece of the puzzle gets us closer to seeing the big picture of how evolution really affects life on Earth, answering questions such as: how gradual is evolution? How much can we learn from our ancestor and what does that tell us about the future?

Citation: Abello, M. A., & Candela, A. M. (2019). Paleobiology of Argyrolagus (Marsupialia, Argyrolagidae): an astonishing case of bipedalism among South American mammals. Journal of Mammalian Evolution, 1-26.

Paleobiological analysis of the first record of redfieldiiform fish found in Korea from the Late Triassic

The first record of redfieldiiform fish (Actinopterygii) from the Upper Triassic of Korea: Implications for paleobiology and paleobiogeography of Redfieldiiformes

By: Su-Hwan Kim, Yuong-Nam Lee, Jin-Young Park, Sungjin Lee, Hang-Jae Lee

Summarized by: Jonathan Weimar

Jonathan Weimar is a geology major at the University of South Florida. Currently he is a senior and is very interested in space and natural hazards. After he obtains his degree, he plans to research the possible careers that coexist with his interests. Aside from geology, he loves making music and has a dream of becoming a professional music artist. 

What data were used? A new well-preserved fossil of redfieldiiform , a type of ray-finned fish, has been discovered from the Triassic Amisan Formation in South Korea. The fossil slightly differs from the regular morphology of redfieldiiform taxa and therefore, represent a new taxon called Hiascoactinus boryeongensis. 

Methods: The Amisan Formation reaches depths of up to 1000m thick and is broken up into three different sections: the lower member, the middle member, and the upper member. By looking at the floral assemblage of the Amisan Formation, scientists were able to date the depositional age of these fossils to be of the Late Triassic (about 237 million years ago). 

Results: The redfieldiiform fish belongs to the larger group called the ray-finned fishes, which make up the majority of fish in today’s oceans. While there have been many discoveries of the redfieldiiform fish in various continents such as North America and Australia, this is the first valid record of the ray-finned fish in Asia. Even though there have been previous records of the redfieldiiform fish in China, Siberia, and Russia, they have been inaccurate, and therefore the specimen in this article found in Korea is notably the first valid record of redfieldiiform fish in Asia. The redfieldiiform fish has many distinguishable characteristics that include: anal and dorsal fins with membranes between the rays,positioning of the anal and dorsal fins, a single-plated ray, and a spindle shaped body covered with scales. The official name given to the discovered fossil is Hiascoactinus boryeongensis. The genus name“Hiascoactinus” is Greek and Latin- based and refers to the unique dorsal and anal fins, while the species name “boryeongensis” refers to the city of Korea, Boryeong. The fossil has a length of 138mm and a width of 38mm. Almost all of the fossil is intact, except some parts of the caudal fin, furthest from the head, as well as parts of the skull and stomach region. Morphologically, there are differences between the new taxon Hiascoactinus boryeongensis and the redfieldiiform fish that have been scientifically researched. For example, there is a difference that focuses on the dorsal and anal fins of the fish. These fins are what help the fish directionally and are very important. A lot of ray-finned fish erect their fins to quickly get away from predators and go after prey as it helps with turning maneuvers. The dorsal and anal fins of the Hiascoactinus boryeongensis, however, are not fully connected between rays, unlike other closely related fish. This would have made it harder for them to complete turning maneuvers. Because of this, it is suggested that the species was slow swimming predators and went after prey that was inactive.

This figure shows us the specimen of the Hiascoactinus boryeongensis and a recreation of the fossil providing more detail of the structures. Parts of the caudal fin furthest from the head, parts of the skull, and parts of the abdomen are missing. That is an artistic representation of what the specimen could of looked like.

Why is this study important? This study is important for many reasons. Firstly, this fossil is well-preserved, which means that it has the greatest potential of revealing information about its physiology, morphology, and taxonomy. It allows for the study of the redfieldiiform group and provides information about how this species may have lived million years ago (e.g., the structures of the fins could indicate its swimming capabilities). Lastly, it shows that global sampling of fossils can reveal new evolutionary adaptations and biogeographic patterns of different species.   

The big picture: This study provides insight on the redfieldiiform fish and shows us how we can use morphological differences to define a new species. This article also shows us the importance of reevaluation of scientific evidence. The previous records of the ray-finned fish found in Russia and China were inaccurate and provided inaccurate biogeographic information on the redfieldiiform fish record. It was with this study and the well-preserved fossil founded in Korea that shows us the first true record of one of these fish in Asia.  

Citation: Kim, S., Park, J., Lee, S., & Lee, H. (2019). The first record of redfieldiiform fish (Actinopterygii) from the Upper Triassic of Korea: Implications for paleobiology and paleobiogeography of Redfieldiiformes. In 1011400475 778507242 Y. Lee (Ed.), Gondwana Research (Vol. 80, pp. 275-284). Amsterdam, Netherlands: Elsevier. doi:https://www.sciencedirect.com/science/article/pii/S1342937X19303211