Drastic variation of cetacean (whale) fossils during the Neogene and Early Quaternary Periods

Stratigraphic Paleobiology of an Evolutionary Radiation: Taphonomy and Facies Distribution of Cetaceans in the last 23 Million Years

Stefano Dominici, Simone Cau and Alessandro Freschi

Summarized by Laura Martins. Laura Martins is a senior geology student at The University of South Florida. She plans to attend a Master program in Geophysics in the spring semester of 2021 out west. She dreams to work in seismological networking. She mostly spends the free days with her son and husband in different adventures such as visiting national parks, springs, Disney, and road trips!

What data were used? The study surveyed over 255 published  papers associated with Neogene (~23-2 million years ago) cetacean (whales, dolphins, porpoises) fossils within a global context (excluding ones found in Southern America, due to a lack of fossil evidence)

Methods: All individual specimens found in the survey were sorted and classified by facies (rock type that represents certain environments) and time intervals (Miocene to Pleistocene Epochs) of deposition. The research also included the number and the preservation quality of bones per skeleton of each example. Even though South American fossils were predicted to have high quality preservation setting due to its hypoxic/anoxic depositional environments, it was set apart because of its lack of even distribution during the Neogene. The study collected a total of 255 specimens with absolute age data and 117 specimens with sedimentary facies data.

Results: The collected data was plotted in two graphs; the first represents the distribution of fossil over time intervals and the second shows the relation between facies (environments) vs time. These illustrations indicate a slight increase of cetacean fossils during the Miocene, followed by a vast increase during the Pliocene. However, by the early Pleistocene, the number of fossils dropped significantly. Consequently, the study conveyed that the highest abundance of cetacean fossils were collected in offshore marine mudstones and sandstones facies, whereas the lowest amount was related to shoreface sandstone facies. It implies that very shallow and very deep waters are not the greatest environments for preservation of these fossils. The study found that offshore mudstone and delta sandstone facies have the highest amount of bones per skeleton, suggesting that these facies are good preservation sites for cetaceans, due to high rates of sedimentation (deltas) and low-pressure settings (offshore) that would minimize decay and scavenging of the organisms. Finally, the research suggests that the remarkable drop off of cetacean fossils in the early Pleistocene might be affected by taphonomy factors (meaning, taphonomy might be making the drop in diversity more severe than it actually was). 

A, Distribution of amount of cetacean’s fossils (%) in a time interval. B, Distribution of amount of cetacean’s fossil (%) over different facies.

Why is this study important? Cetaceans are the largest living marine animals that have ever lived. Through their fossil record, we can understand how their modern and extinct diversity and be explained by variations in taphonomy, taxonomy, loss of habitat, environment, climate and even massive extinction events. The study of this variation on the fossil record allows for the analysis of decay, preservation and environment settings of these large mammals, as well as the relationship of cetaceans with ecosystem changes, enabling the construction of evolutionary pattern trends.

The big picture: The study suggests that the peaks with the highest amount of cetacean fossils during late Miocene and Pliocene are correlated with an optimum climate. The vast drop of fossil localities during the late Pliocene accords with an extinction age. However, it is necessary to highlight that all of the evidence might be affected by taphonomy factors, such as scavengers contributing to loss of tissue and disarticulation.

Citation: Dominici et al. (2018). Stratigraphic paleobiology of an evolutionary radiation: taphonomy and facies distribution of cetaceans in the last 23 million years. Fossilia, Volume 2018: 15-17. https://doi.org/10.32774/FosRep-Pal.20.1810.051517


New Species of Bryozoa discovered in Lake Valley Formation

Bryozoan Fauna of the Lake Valley Formation (Mississippian), New Mexico

By: Andrej Ernst, Karl Krainer, Spencer G. Lucas

Summarized by: Johnathan Cook. Johnathan Cook is a fourth-year undergraduate at the University of South Florida. He spent most of his life involved in missionary work overseas in Argentina. After graduating from an Argentine high school, he returned to the United States to receive his Associates Degree from Hillsborough Community College before transferring the University of South Florida. He is set to graduate in December of 2019 and plans to pursue a career in hydrogeology and water management.

What data were used? Bryozoans (aquatic colonial organisms that survived by filtering nutrients from the water they live in) that had been overlooked in previous studies of the Mississippian-age Lake Valley Formation were re-examined by researchers. They also took a fresh look at the environment they were found in to help gain a better understanding of past climate and how the environment has changed through time. Researchers also looked at the type of sediment and the size of the grains to determine the prevalent geologic processes at the time of its deposition.

Methods: The researchers examined the layers (also called members) of the Lake Valley Formation, noting sedimentary structures and characteristics. Bryozoans specimens were made into thin sections and studied through binocular microscopes to determine the genus and species of each specimen found (which is the only accurate way to determine bryozoan taxonomy).

Results: The study of this area found there to be ten species of Bryozoa in the rock record, one of which had been previously overlooked. The studied samples were taken from two members of the formation and indicate changes in the environment. The older layer, named the Andrecito Member, showed deep marine conditions which were quiet and calm, while the younger layer, named the Tierra Blanca Member, showed shallower conditions with higher energy. The characteristics of these two members are good indicators of environmental conditions present during their creation. The deep conditions of the Andrecito member suggest transgression (meaning sea level was high or rising) and the shallow conditions of the Tierra Blanca suggest regression or sea level falling. The species found in these environments demonstrated physical characteristics in support of this hypothesis. Bryozoans in the calmer environment had thinner branches, whereas those in higher energy were thicker.

A main tool used to help determine the genus and species was
measuring the spacing between structures-the zoaria (individual animals in a single colony) in the bryozoan fossil specimens. This was done under the microscope, as these measurements are quite small.

Why is this study important? This study shows further diversification of a fossil type thought to be well understood, as well as the importance of understanding the stratigraphy in combination with fossils to construct a picture of the processes that formed our continent. These specific species are endemic to North America and can give us an idea of the evolution of climate and its effect on North American rocks.

The Big Picture: The discovery of the diverse fossils along with the sedimentary layers provides a reminder that science is not infallible but often misses details that can alter our understanding or hypotheses of past life. How creatures adapt says a lot about the environment they inhabited and with every new data, we can create a clear and more accurate picture of the past. It is important to remember that a hypothesis is not set in stone but can be edited or even disproved as more data are collected.

Citation: Andrej Ernst, Karl Krainer, Spencer G Lucas. Bryozoan Fauna of the Lake Valley Formation (Mississippian), New Mexico. Journal of Paleontology, 92(4), 2018, p. 577–595.

Understanding and Dating Primate Fossils

100 years of primate paleontology 

By: Richard F. Kay 

Summarized by Ethan Schimpf. Ethan Schimpf is a geology major at USF. He graduates in December of 2019. Upon graduation, he plans to move to Idaho and get a job in the mining field. During his free time he like hunting, fishing, and working on cars.

What data were used? 336 different primate species have been identified through the discovery of fossils as of 2017. Most of these fossils are found in North America and consists of jaws and teeth. 

Methods: This study used amino acid traces left in the fossils to date major changes in primate evolution, like when the split between New World Monkeys and Old World Monkeys occurred and when the split between humans and chimpanzees likely happened. 

Results: Some major traits used to differentiate the two major types (New and Old World) were the shape of the skull and the ability to walk on two legs. This major split occurred around 30 million years ago. With the advancement of technology over the past 100 years, humans are able to study fossils on the molecular and genetic level. The fossils are analyzed for changes in amino acid chains. This allows them to see the evolution of the DNA itself over time. Being able to witness this enables a more accurate timing to be assigned to major changes in primate evolution. In using this process, it was discovered that chimpanzees and humans shared a common ancestor about 5 million years ago. It was also discovered that the genetic molecular evolution rate would slow down as the species grew to a larger body mass as well as a larger brain size.

This graph shows the increase of fossils found within the last 100 years, starting with the first to be described, Adapsis, in 1821. With the abundance of fossils that have been found, scientists have been able to learn a lot more about the evolutionary history of the group that includes humans.

Why is this study important? Over the last 100 years the number of primate fossils being discovered has increased dramatically. The amount of primate fossils is still very low compared to other organisms and the quality of fossils is low. When putting together the evolution of primates through the fossil record, a major distinction was made between Old World Monkeys and New World Monkeys. The New World monkeys consist of shrew and lemur type primates, while the Old world Monkeys included groups like gorillas and chimpanzees. A later a common ancestor was found between humans and chimpanzees. This study allows us to date when major splits occurred during primate evolution. Through the examination of primate fossils major distinctions between common ancestor could be discovered and dated.

The big picture: The geographical distribution of different primates is thought to be due to the changes in sea level over time. At times of low sea level, land bridges formed and allowed primates to travel to different land masses. Then, when the sea levels rose,  primates became stuck in certain areas or separated from other populations of species. The timing of major primate evolution can be dated to similar times of higher seas when species were forced to remain in a particular area. This forced isolation resulted in the gain and loss of traits and, ultimately, new species forming. When dating the different primate fossils, changes in the DNA can be linked to major environment changes due to Earth’s changing climate.

Citation: Kay, Richard F. 100 years of primate paleontology. American journal of physical anthropology 165.4 (2018): 652-676.

Complex Relationships of Pararotadiscus guishouensis in Life and Death

Paleoecological Significance of Complex Fossil Associations of the Eldonioid Pararotadiscus guishouensis with other Faunal Members of the Kaili Biota (Stage 5, Cambrian, South China)

by: Yuanlong Zhao, Mingkun Wang, Steven T. LoDuca, Xinglian Yang, Yuning Yang, Yujuan Liu, and Xin Cheng

Summarized by: Dinah Hunsicker. Dinah Hunsicker is currently an undergraduate senior studying Geology at the University of South Florida.  She will earn her Bachelor’s degree at the end of 2019. She has a passion for science, music, mathematics, and spends much of her time outdoors. She loves to garden and paint, and absolutely loves collecting cool rocks and minerals! (Favorite mineral: azurite).

What data were used? 628 collected fossil specimens from the Kaili Formation, Guizhou Province, South China preserved in association with the Pararotadiscus guishouensis, an organism that has a high likelihood to have shared symbiotic relationships with other groups. P. guishouensis is an eldonid, a medusoid (e.g., like jellyfish) -shaped organism that scientists aren’t entirely sure what groups it belongs to. 

Methods: Associated fossils were classified into 4 types of relationships with P. guishouensis  (symbiosis (interacting with one another), co-burial, attachment of benthic taxa on P. guishouensis carcasses, and scavenging of carcasses after death.

The figure above shows a variety of organisms preserved in the fossil record showing different types of symbiotic relationships with Pararotadiscus guizhouensis. Parts 5 and 6 show the symbiotic relationships between this fossil and brachiopods and how many brachiopods could be found in association on one organism.

Results: I have broken this into the 4 sections defined above. Symbiotic Relationship: brachiopods, trilobites, and juvenile echinoderms in this area were found to have symbiotic relationships with Pararotadiscus guishouensis (P. g.). Benthic (lived on the seafloor): organisms latched onto P. guishouensis, taking advantage of the calmer water current, giving them an opportunity to expand their ecological niche. Co-burial: it makes sense that since many of the previously mentioned critters latch on to P. g, they’ve committed to life and death with their host. Additionally, a variety of fragmented and partial fossils (bits and pieces of trilobites, brachiopods, echinoderms and algae) buried around the same time are also associated with P. guishouensis. Post-Mortem Attachment: the carcass of P. guishouensis was an oasis of solid mass on the soft-sediment seafloor, leading to a multitude of species taking up life habits on the carcasses of P. guishouensis, including colonization by echinoderms. Post-Mortem Scavenging: Among the 628 specimens, 24% are preserved with squiggling traces of surface scavenging, associated with worm-like creatures called Gordia marina. No evidence of any other type of scavenging relationship has been detected.

Why is this study important? This study contributes to the growing body of evidence that the ecology of the Cambrian biosphere was more intricate and complex than previously suspected; originally, scientists assumed the Cambrian had a general lack of ecological diversity. Insights relating to organismal interactions during the Cambrian can help us further our understanding about the inter-complexities of life on this planet through a broad lens of time.

The big picture: This well-preserved group of organisms, such such as brachiopods, trilobites, echinoderms, and a type of ancient sea worm co-habituated and had multi-layered, complex biotic relationships with Pararotadiscus guishouensis at the site of the Kaili Formation in China, giving us insight into the lives of these ancient sea critters, contributing to our conceptions and understandings about Cambrian life.

Citation: Zhao, Y., Wang, M., LoDuca, S., Yang, X., Yang, Y., Liu, Y., & Cheng, X. (2018). Paleoecological Significance of Complex Fossil Associations of the Eldonioid Pararotadiscus guizhouensis with other Faunal Members of the Kaili Biota (Stage 5, Cambrian, South China). Journal of Paleontology, 92(6), 972-981. https://doi.org/10.1017/jpa.2018.41

Understanding the Permian-Triassic transition with fossil data before and after the mass extinction event

Environmental instability prior to end-Permian mass extinction reflected in biotic and facies changes on shallow carbonate platforms of the Nanpanjiang Basin (South China) 

Li Tian, Jinnan Tong, Yifan Xiao, Michael J. Benton, Huyue Song, Haijun Song, Lei Liang, Kui Wu, Daoliang Chu, Thomas J. Algeo

Summarized by: Baron C. Hoffmeister. Baron Hoffmeister is currently an undergraduate senior at the University of South Florida pursuing a degree in Environmental Science and Policy with a minor in Geology. After graduation, he plans to attend a graduate program for environmental management. When graduate school is complete, he plans on working for the National Parks services. Baron is apart of the geology club as well as the fishing club and spends his free time hiking, fishing, and socializing with friends.

What data were used? Fossil taxa found in Southern China carbonate platforms that date back to the Permian-Triassic extinction event, ~251 million years ago. This data sheds light on the mass extinction event that spans the Paleozoic and Mesozoic Eras. 

Methods: Analytical evaluation of fossils present from three separate stratigraphic areas across South China, from before, during, and after the Permo-Triassic extinction event. 

Results: In this study, the fossil data evaluated at each site led to the discovery of common trends. Each formation had similar fossil accumulations, even though the formation would have been located a far distance apart. This means that each location was affected similarly  by the same event for the accumulation of similar fossils to appear in the corresponding strata. This is hypothesized to be the late Permian mass extinction. Another similarity between the three areas was that each section had a foraminifera gap between strata boundaries. At the same time, each boundary represented a different aspect of a shallow marine environment. For example, the Wennga Formation had strata before the extinction boundary that was littered with Permian fauna fossils that occurred in shallow marine environments. Post-extinction boundary strata didn’t possess these fossils. This is another indication of the severity of the mass extinction event. The Taiping section had different types of rock formations with different compositions; the transition of the rock from before the extinction to after showed a rapid die-off of organisms living in this area. Finally, in the Lung Cam section, there were fewer fossils than the other two (most likely due to poor fossil preservation conditions); however, the fossils that were found resembled those in the other sections studied. Further, the Lung Cam section had foram gaps consistent with the other sections.

Skeletal composition within strata at each study section. The three sections had similar organisms preserved in each and even showed similar gaps in fossil occurrences, indicating where the extinction event happened.

Why is this study important? This study strengthens what we know about the Permian-Triassic transition. These fossils, across multiple areas, were present in a shallow marine environment and were greatly affected by environmental instability during this time. The strata at each location, Wengna, Taiping, and Lung Cam, are remnants from the fatal conditions in the marine environment at this time. This can better help us understand and conceive how shallow marine organisms could be affected today during climate change. 

The big picture: This study shows the significant changes in fossils from  before and after the largest extinction event in Earth’s history. There is consistent evidence within and between each section studied, indicating a widespread event that negatively affected shallow marine life during this time.

Citation: Tian, Li, Jinnan Tong, Yifan Xiao, Michael J. Benton, Huyue Song, Haijun Song, Lei Liang, Kui Wu, Daoliang Chu, and Thomas J. Algeo. “Environmental instability prior to end-Permian mass extinction reflected in biotic and facies changes on shallow carbonate platforms of the Nanpanjiang Basin (South China).” Palaeogeography, Palaeoclimatology, Palaeoecology 519 (2019): 23-36. DOI: 10.1016/j.palaeo.2018.05.011

Relationship between Climate Change and Cannibalistic Gastropod Behavior

Indirect effects of climate change altered the cannibalistic behaviour of shell-drilling gastropods in Antarctica during the Eocene

Gregory P. Dietl, Judith Nagel-Myers, and Richard B. Aronson

Summarized by Joseph Ferreira. Joey is a senior at the University of South Florida in Tampa. Joey is pursuing his B. S in geology and is planning on finding a job either in the hydrology or seismology field. He has aspirations of owning his own business one day providing geo surveying services to companies in need of them. In his free time, Joey enjoys playing guitar and hanging out with his friends and family.

What data were used? The samples in this study included nearly 2,000 Naticidae Falsilunatia gastropod (snail) shells that were preserved well enough to show bore holes made from the cannibal snails. These samples were from a time frame in the Eocene that experienced mass cooling event. These samples came from 108 different localities in Seymour Island, Antarctica.

Methods: The prediction made during the start of this study suggested that the cooling temperatures would result in a decrease in the cannibalistic behaviors of these gastropods; meaning,  the colder temperatures would make it more difficult for the mollusk to maintain a productive activity level. To test their hypothesis, each drill hole found on the gastropods (complete or incomplete) was counted and the frequency of cannibalism was found by dividing the number of drilled samples by the total number of specimens in the group. The scientists looked at how frequent the drilled holes were in the specimens and also the body size of each specimen. They connected these specimens to a time either before, during, or after the known cooling event. They then looked to see if there were any significant changes in the frequency of these cannibalistic drill holes.

Figure showing Seymour Island in Antarctica (image A) where the study took place along with (image B) a sample with a perfectly drilled hole and a sample with an incomplete drill hole from another Falsilunatia gastropod. Image C shows one of the cannibalistic snails from multiple angles.

Results: When comparing the number of attacked specimens from before, during, and after the cooling event that occurred nearly 41 million years ago, the frequency of cannibalistic tendencies did not decrease or increase, but they remained stagnant. There was a very slight increase in frequency, but this increase was not statistically significant, meaning the increase was not big enough to cause concern or to blame the temperature change. This result came was a surprise because the way that these naticids drill holes into their prey’s shell involves a chemical reaction to dissolve the carbonate shell. The cooling temperatures were thought to slow down this chemical reaction hence slowing down the rates of cannibalistic tendencies between these creatures. However, this was not the case, the rates of cannibal attacks remained steady during the cooling event.

Why is this study important?  This study is important because it gives us a better understanding of how climate change can potentially affect species’ behaviors and tendencies. Even though the Falsilunatia’s cannibalistic behaviors were not affected by the cooling temperatures, it still shows some insight on how not all creatures are drastically affected by cooling events. Understanding the correlation between climate change and species behavior can help us gauge what we will expect to see in different animals’ behaviors as today’s climate change is in full effect.

The big picture: This study was set out to find the relationship between an Eocene cooling event and the cannibalistic behaviors of Falsilunatia gastropods. Although finding no direct effect from the cooling temperatures, this is still an excellent example of how we can use the behaviors of ancient creatures and their response to global climate alterations to predict how today’s animals will respond to more recent climate change.

Citation: Dietl G.P., Nagel-Myers J., Aronson R.B., 2018 Indirect effects of climate change altered the cannibalistic behaviour of shell-drilling gastropods in Antarctica during the Eocene: Royal Society Open Science, v. 5, 181446. http://dx.doi.org/10.1098/rsos.181446

A fossil-rich rock formation at the Cretaceous-Paleogene Boundary in Mississippi, USA indicates environmental changes before mass extinction

A fossiliferous spherule-rich bed at the Cretaceous–Paleogene (K–Pg) boundary in Mississippi, USA: Implications for the K–Pg mass extinction event in the Mississippi Embayment and Eastern Gulf Coastal Plain

James D.Witts, Neil H.Landman, Matthew P. Garb, Caitlin Boas, Ekaterina Larina, Remy Rovelli, Lucy E. Edwards, Robert M.Sherrell, J. KirkCochran

Summarized by Mckenna Dyjak. Mckenna Dyjak, who is an environmental science major with a minor in geology at the University of South Florida. She plans to go to graduate school for coastal geology; once she earns her degree, she plans on becoming a research professor at a university. Mckenna spends her free time playing the piano and going to the gym.

What data were used? A fossil and spherule-rich rock formation in Union County, Mississippi exposed by construction. The formation contains the Cretaceous-Paleogene (K-Pg) boundary, which marks the end of the Cretaceous and the beginning of the Paleogene, estimated at ~66 million years ago. This boundary is characterized by a thin layer of sediment with high levels of iridium which is uncommon in Earth’s crust, because it is almost exclusively from extraterrestrial sources.  The K-Pg boundary is associated with a mass extinction: a significant, widespread increase in extinction (ending of a lineage) of multiple species over a short amount of geologic time. The iridium indicates that the extinction was likely caused by an extraterrestrial impact; the spherules found support this idea as well, as spherules are formed from ejecta after an impact. 

Stratigraphic (ordered) section of the rock formation showing the rock units, type of
sedimentology (sand, silt, clay), and fossil type. The K-Pg boundary is marked by the horizontal
dashed line. The black arrows point to calcareous nannofossils and the white arrows point to
dinoflagellate cysts.

Methods: The fossils present in the rock formation were identified and compiled into a complete list. In order to find out the composition of the rock formation. 14 sediment samples were collected; these samples were used to construct a biostratigraphic analysis: corresponding relative rock ages of different rock layers to the fossils found within them. The mineral composition and grain size were determined to construct this analysis. The mineral composition (mineral percentages present) of the sediment samples were determined by using a Scanning Electron Microscope (SEM) and a Diffractometer (type of X-ray). The grain size analysis of the sediment samples was determined by using a sieve (mesh strainer) to sort into different sizes. The Carbon-13 levels of the sediment samples were analyzed: Carbon-13 can be used to determine the amount of plants that were present at the time.The data collected was used to construct the stratigraphic section shown in the figure below.

Results: There was a significant decrease in the amount of micro and macro fossils present. Along with the decrease of fossils there was a positive shift of Carbon-13. The positive shift of Carbon-13 indicates that there was an increase in plant matter buried in the rock record. Sedimentary structures such as weak cross-bedding and laminations (indicates flowing water and fluctuating energy levels) An important layer was analyzed: 15–30 cm thick muddy, poorly sorted sand containing abundant spherules (sphere pieces) that were likely a product of  the Chicxulub impact event.

Why is this study important? The findings suggest that there was a quick, local change in sediment supply and possibly sea level due to the significant variation in facies (body of sediment), fossil changes, and different geochemical data that coincided with the extinction event. 

Big Picture: This study helps us understand how different areas were affected locally before the mass extinction event, which can help us understand how recovery from mass extinctions take place. 

Citation: Witts, James, et al. “A Fossiliferous Spherule-Rich Bed at the Cretaceous-Paleogene (K-Pg) Boundary in Mississippi, USA: Implications for the K-Pg Mass Extinction Event in the MS Embayment and Eastern Gulf Coastal Plain.” 2018, doi:10.31223/osf.io/qgaj

Recently excavated human skulls provide insight into human migration from Southeast Asia to Australia

Somewhere beyond the sea: Human cranial remains from the Lesser Sunda Islands (Alor Island, Indonesia) provide insights on Late Pleistocene peopling of Island Southeast Asia

Sofía C. Samper Carro, Felicity Gilbert, David Bulbeck, Sue O’Connor, Julien Louys, Nigel Spooner, Danielle Questiaux, Lee Arnold, Gilbert Price, Rachel Wood, Mahirta

Summarized by: Lisette E. Melendez. Lisette Melendez is a geology major and astronomy minor at The University of South Florida. She is currently a junior, but has her sights set on going to graduate school for planetary Geology. She loves rocks, space, and everything pink.

What data were used? Newly excavated human remains from three test pits in Tron Bon Lei
(Wallacean Islands, Indonesia) are being compared to human remains from Asia and Australia to test for similarities. Other elements that were found in the excavation include shellfish, fish remains, and fish hooks were used to characterize the living environment.

Methods: This study used dating of various elements and observation of skull traits to estimate ages of the cranial remains. The first element studied was the amount of carbon- 14 in the specimen because carbon-14 can date items up to approximately 50,000 years old. Uranium and Thorium are both elements that are preserved in fossilized teeth and those elements were also measured to reinforce the reliability of the age estimates from carbon. Physical traits of the skull fragments were analyzed to estimate the age and sex of the samples. Age estimation was based on how worn down the teeth were and degree of cranial suture closure (tissues that fuse together as you get older).

The human remains recovered from Tron Bon Lei (Wallacean Islands, Indonesia).

Results: The dating measurements of these Wallacean specimens suggest that the skeletons were buried around 11.5 to 13 thousand years ago, at the end of the Pleistocene Epoch. They are smaller than any of the other cranial remains from Indonesia, Australia, and New Guinea, but the small size of these remains are similar in size to Holocene- age remains, supporting the model that southeastern Indonesian populations were isolated.

Why is this study important? This study helps us unravel the environment of southeast Asia and understand living conditions thousands of years ago.

The big picture: This study shows that the Wallacean islands may be an example of island dwarfing, suggesting that these populations may have been relatively isolated, at least up to the late Pleistocene. Island dwarfing typically occurs when there is a scarce amount of resources on an island, which was only exacerbated by the genetic isolation that occurred on this island.

Citation: Samper Carro, S. C. et al. Somewhere beyond the sea: Human cranial remains from the LesserSunda Islands (Alor Island, Indonesia) provide insights on Late Pleistocene peopling of Island Southeast Asia. J. Hum. Evol. 134, 102638 (2019). Online.

Using glacial erratics to study nautiloids in eastern New York

Nautiloid cephalopods from the Rickard Hill facies of the Saugerties Member of the Schoharie Formation, eastern New York, USA (late Emsian, Devonian): A case study in taphonomy 

Martin A. Becker, Harry M. Maisch IV, Rebecca A. Chamberlain, John A. Chamberlain Jr., Christi G. Kline, and Clint F. Mautz

Summarized by Leighanne Haverlin. Leighanne Haverlin is a geology major at the University of South Florida. She will graduate in December of 2019 and plans to enter the workforce in the field of environmental consulting, coastal geology, or geophysics. After some time working, she hopes to further her education and earn a master’s of science in one of the fields previously mentioned. In her free time, she enjoys running, kayaking, and listening to music. 

What data were used? Glacial fragments containing Nautiloid cephalopods found in the Rickard Hill facies (RHf; facies refer to a certain group of rocks that share the same characteristics) of Lower New York and northern New Jersey were compared to outcrops from the Helderberg Mountains near Clarksville, New York. 

Methods: This study used petrographic thin sections (microscope analysis of the rock) along with hand samples to look at chemical and physical erosion to determine depositional environment (the environments in which rocks were formed in) and lifestyle of nautiloids, animals closely related to the octopus today. 129 specimens in glacial fragments from the RHf were examined. 

Results: By studying the nautiloid assemblages, the study determined that the depositional environment was an inner shelf reef. The glacial erratics (rock that is different than the surrounding rock where it lies) that were found in the Lower Hudson Valley of New York were similar to the rock found in the Helderberg Mountains of New York which are approximately 200 km to the north. The erratics contain nautiloid fossils with coiled and orthoconic (long and narrow) shapes. They were physically and chemically weathered when the Laurentide Ice Sheet, the major ice sheet that covered much of northern North American approximately 20,00 years ago) moved. The nautiloid fossils that were found were determined to be assembled after their death in an area that sustained living organisms. This deposition occurred during a sea level regression (a sea level drop). The RHf glacial fragments featured jointed bedding that is also present in the outcrop in Clarksville, NY. For 5,000 years, the nautiloids were eroded during the movement of the ice sheet and experienced dissolution (meaning they and the rock they were contained in began to dissolve over time) which exposed and preserved structures. The study determined that the depositional environment was an inner shelf reef that harvested great biodiversity (a high number of species of animals). To confirm this hypothesis, it was argued that it is uncommon for dead organisms (especially nautiloids) to drift very far distances after death because the shells would sink to the sea floor. It was determined that juvenile nautiloids lived in a different depositional environment than adults, which explains the large size of the nautiloids in the RHf. The nautiloids were continually buried and unburied due to storm events and sea level change. This same hypothesis was used to understand the fossil assemblages of the Wadleigh Formation in Alaska, the Cherry Valley Limestone in NY, and the Trebotov Chotec Limestone in the Czech Republic

Nautiloid casts from RHf glacial erratics. Both orthoconic (long and narrow) and coiled forms are depicted in the image.

Why is this study important? Prior to this study, no research had been conducted that explained the conditions that resulted in the large numbers and sizes of both coiled and long and narrow (orthoconic) nautiloid cephalopods. This study provided evidence that indicates that much of what we thought we understood of cephalopod ecology (where an animal lives and how it interacts with other animals) and preservation needs to be revised. This was also the first study that used glacial erratics and principles of sequence stratigraphy to address the lives of an assemblage of nautiloids which makes this study unique. 

The big picture: This study used a new method of using glacial erratics and principles of stratigraphy to determine the lifestyle of a species. Nautiloid adults and juveniles are not found in the same depositional environment. The glacial erratics that do not belong to the RHf show similar assemblages of nautiloids which can be analyzed using the same method. Overall, the study brought in a new method of studying taphonomy which could be used in future studies.   

Citation: Becker, M.A, Maisch, H.M., Chamberlain, R.A., Chamberlain, J.A., Kline, C.G. and Mautz, C.F.., 2018, Nautiloid cephalopods from the Rickard Hill facies of the Saugerties Member of the Schoharie Formation, eastern New York, USA (late Emsian, Devonian): A case study in taphonomy : Palaeontologia Electronica, 21.3.42. https://doi.org/10.26879/896

How much ice does Antarctica lose during warm times in Earth’s history?

Ice loss from the East Antarctic Ice Sheet during late Pleistocene interglacials
David J. Wilson, Rachel A. Bertram, Emma F. Needham, Tina van de Flierdt, Kevin J. Welsh, Robert M. McKay, Anannya Mazumder, Christina R. Riesselman, Francisco J. Jiminez-Espejo, Carlota Escutia
Summarized by Time Scavengers collaborator Adriane Lam

Figure 1. An elevation map of Antarctica with a) the major regions labeled and b) a zoomed-in view of East Antarctica. The location of the sediment core (named U1361A) is denoted by the pale yellow dot. Image from Wilson et al. (2019).

Brief Summary: Today, sea level rise due to increasing global average temperatures is a huge threat to low-lying, coastal, and island communities. Sea level is rising, in part, from ice that is melting on Antarctica and Greenland. To understand how much sea level may rise in the near future, scientists look to the geologic past, when global temperatures were much warmer than today or close to the temperatures predicted for the coming decades. In this study, scientists looked at how much ice was lost from the Wilkes Subglacial Basin of East Antarctica during a time when global average temperatures were about 2 degrees Celsius warmer than pre-industrial values. They find that during these warmer periods, called interglacials, there was significant ice that melted from East Antarctica, and contributed to sea level rises. Thus, in the future, the ice melting from East Antarctica will contribute more to sea level rise than we previously thought.

Data used and Methods: Sediment from a deep-sea core drilled from the continental margin of East Antarctica was used in this study (Figure 1). From this sediment core, the authors analyzed the different types of sediment contained within the core through time. From the changes in sediments, the scientists could tell how much erosion was occurring. They also looked at the neodymium (Nd) isotopes from the sediments. Nd isotopes are a good way to also trace where the sediments in the core were coming from, so the scientists could determine not only how much erosion was taking place within East Antarctica, but where the eroded sediment was coming from. Increased erosion and a shift in the Nd isotope records indicate increased glacial melt and ice retreat on East Antarctica, thus the authors could tell through geologic time when and approximately how much the ice melted.

Results: Over the past 800,000 years, Earth’s climate has oscillated between cooler (glacial) and warmer (interglacial) periods (read more about this on our CO2 page). During some interglacial periods (times when the climate was warmer), the scientists found that the East Antarctic Ice Sheet began to erode the rock on which it sits and melted significantly. This led to increased sea levels within a world that was less warm than today.

Why is this study important? This study places new approximations on how much melting from East Antarctica could occur in a warming world, and how much that could raise sea level. Climate scientists think that if all the ice on East Antarctica were to melt, it would lead to approximately 53 meters of sea level rise globally! With the data from this study, it will provide new constraints on melting ice in a warming world, which will be incorporated into climate models of the future climate. This data will be given to policymakers to help us best prepare and mitigate the consequences of climate change.

Citation: Wilson, D. J., Bertram, R. A., Needham, E. F., van de Flierdt, T., Welsh, K. J., McKay, R. M., Mazumder, A., Riesselman, C. R., Jimenez-Espejo, F. J., and Escutia, C., 2019. Ice loss from the East Antarctic Ice Sheet during late Pleistocene interglacials. Nature 561, 383-386.