Newly discovered hatchling sea turtle fossil track marks allow paleontologists to compare ancient sea turtle breeding ranges and climate conditions compared to that of the modern day

New fossil sea turtle trackway morphotypes from the Pleistocene of South Africa highlight role of ichnology in turtle paleobiology

Martin G. Lockley, Hayley C. Cawthra, Jan C. De Vynck, Charles W. Helm, Richard T. McCrea, Ronel Nel

Summarized by Sophia Gutierrez, who is majoring in geology at the University of South Florida. She is currently a senior and plans to pursue some experience in the field before continuing to further her education with a graduate program majoring in sedimentary geology. When she’s not studying geology, she enjoys walking in nature and listening to music.

What data were used? Three coastal sites, showing never before seen fossilized sea turtle hatchling track marks were discovered on the south coast of South Africa originating from the late Pleistocene (~100,000 years ago). Two species of sea turtles were ultimately identified from their trace fossils at the sites as loggerhead (Caretta caretta) and leatherback (Dermochelyis coriacea) sea turtles. Some track marks showed multiple “footprints” coming out of a centralized area that could possibly represent the ancient nesting location.

The three coastal S. African sites with never before recorded sea turtle hatchling fossil traces (A) Site 1, 3 loggerhead hatchling track marks, Australochelichnus agulhasii. The 2 track ways on the right show overlap. (B) Site 2, a leatherback turtle hatchling curved trackway, Marinerichnus latus, with red marks to show the lengths of the inner and outer sidelines. (C) Site 3, the long arrows show two sets of loggerhead trackways, Australochelichnus agulhasii, from different hatchlings. The shorter arrow shows an uncertain trace, but this may signify the remains of a nest in the center where the circle is.

 

Methods: This study used two dimensional (2D) and three dimensional (3D) photographed images of the trackways in track sites 1 and 2, not far from each other, showing the sea turtle hatchling trails that were preserved in the large slab of rock. Tracing diagrams were then drawn to illustrate detailed trackway patterns of the two hatchling species. Site 3 fossils were found on a portable boulder. The boulder was photographed and taken to be preserved and studied at a separate location.

Results: After the fossil traces had been properly examined, it was concluded that the sets of tracks found in site 1, on a large slab of rock that had fallen off the side of a cliff, were those from hatchling loggerhead sea turtles. Site 2 is positioned close to site 1 in a narrow cliff pass filled with fallen rock slabs and boulders. One of those slabs holds fossilized hatchling leatherback sea turtle tracks. The final track site was found about 100 km (~62 miles) away from the other two, on a portable boulder that showed newborn loggerhead tracks appearing suddenly from the ground, likely representing the moment the hatchlings traveled out of their nest in the sand. Site 3 is especially interesting because it shows two sets of track marks emerging from the sand but paddling in opposite directions, 180° from each other. Site 2 also shows indications of the hatchling emerging suddenly from the sand but in this case, it’s unclear to say if this suggests a nest or shows signs of inadequate trace fossil preservation. These fossilized loggerhead and leatherback hatchling sea turtle tracks have never been documented before and are fairly distinct from other marine and terrestrial turtle track sites recorded. Due to these reasons, the paleontologists who discovered these tracks may assign these ichnotaxa (a taxonomic group based on the trace fossils of an organism) new, original names: Australochelichnus agulhasii for the hatchling loggerhead tracks and Marinerichnus latus for the hatchling leatherback tracks. These ichnotaxa provide us with copious information about ancient sea turtle breeding ranges, given that both loggerheads and leatherbacks nest in very specific conditions. This gives an insight on how the climate conditions in the late Pleistocene may have been in this area where temperatures were calculated to be about 25° to 35° C with a water level up to 6 meters (20 ft) higher than they are today. The presence of the Marinerichnus latus tracks made by leatherbacks (site 2) so close to the Australochelichnus agulhasii tracks made by loggerheads (site 1) in the area they were found in suggests that the breeding areas for the leatherback were twice as extensive in the Pleistocene than they are today.

Why is this study important? This study allows scientists to combine what is known about modern sea turtle hatchings with what was discovered from fossil tracks from about 100,000 years or so ago. The location that the trace fossils are preserved in can reveal to scientists the environmental and climatic conditions of the late Pleistocene, which could broaden the understanding of naturally changing climates of the past and the rapidly increasing climate change in the present day. Along with that, due to the close range of the leatherback and loggerhead turtle fossil nest sites in sites 1 and 2, this study demonstrated that modern breeding ranges of both leatherback and loggerheads have been halved in the past 100,000 years.

The big picture: This paper studied the ichnological evidence (the trace fossils made by an organism at the time it is alive) made by two distinct species of hatchling sea turtles. Scientists related the breeding ranges of modern sea turtles to the ancient breeding ranges they observed at the fossil sites and suggested the climate of the late Pleistocene ranged from 25° to 35° C and had sea levels up to 6 meters (20 ft). As of 2021, loggerhead sea turtles are endangered and leatherback sea turtles are vulnerable species. This study could potentially help future populations of these species due to the new knowledge of ancient breeding ranges relative to the specific nesting conditions.

Citation: Lockley, M. G., Cawthra, H. C., De Vynck, J. C., Helm, C. W., McCrea, R. T., Nel, R. 2019. . Quaternary Research 1–15. https:// doi.org/10.1017/qua.2019.40

Scavenging, Cannibalism, and Survival in Jurassic Utah

High frequencies of theropod dinosaur bite marks provide evidence for feeding, scavenging, and possible cannibalism in a stressed Late Jurassic ecosystem

Stephanie K. Drumheller, Julia B. McHugh, Miriam Kane, Anja Riedel, Domenic C. D’Amore

Summarized by Reynolds Hansen. Reynolds Hansen is an undergraduate geography major / geology minor at the University of South Florida. With a lifelong passion for paleontology instilled from an early age, Reynolds always knew the academic path ahead had a singular destination. Along the way, he picked up equal affinities for history and geography, and by the time he was in college, he worried he might have to choose one over the others. With the help of the university’s esteemed academic professionals and resources, he shifted focus with the goal of becoming a science communicator, telling the story of our world from the formation of the earth to the modern day as an interconnected narrative. Reynolds is set to graduate in the spring of 2021, after which he wishes to seek a post-graduate degree in paleontology, and a career as an educator. His academic focus is utilizing GIS to research paleoecological phenomena.

Methods: The study collected fossil data from the Upper Jurassic Mygatt-Moore Quarry in Utah, USA (MMQ). Out of 2,368 found specimens, 684 specimens positively displayed some damage resulting from contact with theropod dinosaur teeth. These damages were categorized into broad categories- pits, punctures, scores, and furrows (Fig 1.) The dimensions of these features, along with spacing between them, measured from raking light (light shone upon an object at a low angle in order to more easily observe details on its surface) and low magnification, helped the team to determine the species responsible for the damages. The marks here were also compared to identical features left by large, modern mammalian predators to determine intent- where on the body the animal was removing material, and whether this was done during predation of scavenging. These marks are considered in relation to ‘low’ and ‘high’ economy regions- meaning, the parts of prey animals that provide low or high nutritional benefit respectively. The goal of these methods was to determine the extent of scavenging behaviors among theropods- a group of mostly carnivorous, bipedal dinosaurs with hollow bones and three-toed limbs. The theropods in question in this region were primarily Allosaurus and Ceratosaurus.

A. Striations produced by teeth on Allosaurus claw. B. ‘Score’ left on an Allosaur vertebral centrum. C. ‘Score’ left on Apatosaurus rib fragment. D. Group of ‘furrows’ on an Apatosaurus pubis (part of the hip). E. ‘Puncture’ (white arrow) and ‘pit’ (yellow arrow) on an Allosaurus caudal (near the tail) vertebral centrum. F. dense group of ‘furrows’ on an Apatosaurus ischium (part of the hip). All scale bars are equal to 10mm.

Results: As in many cases, predation behavior is often dictated by environmental conditions. In the MMQ, sediment suggests an environment with low deposition rates, allowing for animal remains to be exposed for longer periods of time, which consequently allows for remains to be scavenged repeatedly. Tooth striations on the formation’s fossils suggests typical theropod behavior was targeting soft tissues near high-economy regions (regions that provide the most nutritional benefit). However, just less than half of all marks on herbivores are also located in low-economy regions, indicating that remains were stripped of any possible material by large theropods. These statistics flip when tooth marks are found on theropod remains, where more than half of the tooth marks are found in low-economy regions. Together, these findings may suggest that aside from remains being present for longer periods of time, the region may have also been prone to periods of nutritional hardship, leading to cannibalism among theropods when scavenging, and possibly even predation. For any of the theropods present in this ecosystem (Allosaurus, Ceratosaurus, and possibly Saurophaganax or Torvosaurus), these occurrences would mark the first recorded cases of cannibalism for these species, implying a need that is situational in times of hardship, rather than a trait reserved to specific species.

Why is this study important? The importance of this work is twofold. In the first manner, it provides insight into an area that is integral to understanding an extinct carnivorous animal: how it eats. The paper mentions on a couple of occasions that, to date, the conventional understanding of how theropods acquire nutrition was by focusing primarily, maybe even exclusively, on soft-body materials- the aforementioned ‘high economy’ zones. There had been little evidence up to this point for scavenging behavior among theropods, aside from some works regarding this behavior in tyrannosaurs, although even this was at least partially inferred to the development of osteophagy (the ability to eat and derive nutrients from bones) in these animals. So too with cannibalism, where Majungasaurus represented the only known case, again, for tyrannosaurs. With this study, theropods appear to resemble something more within the norm of how we understand most carnivores to behave: opportunistic consumers who take advantage of ‘free’ scavenge-able meals where they could get them, and who are none too picky in troublesome times. The second point of importance, and perhaps light criticism, from this piece is the allusion to the practice of fossil collection by institutions. The question is raised by the paper: if this behavior were to be commonplace, why is there so little evidence of it? The MMQ had recently undergone a transition of collection practices, from selective collecting to a more total method, taking in as many specimens as possible without too much scrupulousness for overall quality. The team cites this change as a likely reason for the abundance of tooth-marked fossils in the study, since they were not tossed aside preemptively for not being ‘aesthetically pleasing’, ‘good quality’ fossils.

The Big Picture: This paper does as much to reflect on paleontological research practices as it reveals about theropod behavior. On one hand, its revelations of how theropods survive difficult times by extensively scavenging every possible resource- and apparently from any source- is certainly a tremendous leap in this field for dinosaur behavior. The other side of the coin is that this study may not have had such diverse results if it were not for size and breath of the MMQ’s sampling. The commentary from the paper is subtle but cautionary: that we should aim to eliminate bias at every opportunity in research, but also in our very initial collection efforts.

Citations: 

Drumheller SK, McHugh JB, Kane M, Riedel A, D’Amore D. 2020. High frequencies of theropod bite marks provide evidence for feeding, scavenging, and possible cannibalism in a stressed Late Jurassic ecosystem. PLOS ONE 15(5):e0233115

Rogers, Raymond R.; Krause, David W.; Curry Rogers, Kristina (2007). “Cannibalism in the Madagascan dinosaur Majungatholus atopus”. Nature. 422 (6931): 515–518

Examining Cryolophosaurus: Shedding Light on a Little-Known and Important Jurassic Dinosaur

An enigmatic theropod Cryolophosaurus: Reviews and comments on its paleobiology

By: Changyu Yun

Summarized by Ohav Harris, a geology major at the University of South Florida and is currently a junior. He plans to pursue a doctorate degree in paleontology and become a paleo-educator in some capacity, either working in a museum or a university. In his free time, Ohav enjoys collecting Pokémon cards, reading manga, and fishing.

What data were used? The author, Yun, used many previously published peer reviewed papers to review and evaluate the ideas that exist regarding Cryolophosaurus’s evolutionary relationships, or phylogenetics. The only known fossil data for this dinosaur are hip fragments, various vertebrae, rib fragments, femurs, part of its foot, and the holotype (the fossil that the description of the genus/species is based on), which include the skull and neck vertebrae – all of which were found in Antarctica. The sparse remains of Cryolophosaurus make it difficult to make definitive statements of its relationship to other theropods (bipedal dinosaurs that are primarily carnivorous), though researchers are confident that it is a theropod. Yun includes an array of possibilities from various sources that attempt to answer the question of this dinosaur’s phylogeny and examines what fossil data of Cryolophosaurus there are to make comments on its ecology and biology.

Methods: Yun analyzes Cryolophosaurus’ anatomy and geographical placement, makes comparisons to better known dinosaurs, and references scientific papers that discuss this Cryolophosaurus to draw conclusions regarding its possible phylogeny, ecology, and biology. Certain features of this animal, like the shape of its skull, the structure of its feet, and the purpose of its skull crest, are discussed and used to support Yun’s claims of the nature of Cryolophosaurus.

Reconstruction of Cryolophosaurus by Daniel Goitom. The defining crest is boldly colored, so as to attract the attention of a mate. Cryolophosaurus’s primitive, needle-like feathers would have been an excellent source of thermal insulation in the Antarctic climate in which it lived.

Results: While the exact phylogeny of Cryolophosaurus is tricky, and not yet fully understood, there are a few things that can be said about it. The skull of Cryolophosaurus has features of tetanurans, dinosaurs that are more closely related to modern birds, like Allosaurus, and earlier, more primitive therapods like Ceratosaurus. Tetanurans and Ceratosaurus are closely related, but took different evolutionary paths. The tetanurans are made up of two groups, carnosaurs and coelurosaurs, which contain a majority of the most famous therapods like Allosaurus and Tyrannosaurus respectively, and all modern birds (descending from the coelurosaurs). Because Cryolophosaurus’ skull has both features of tetanurans and earlier theropods, it can be inferred that it is a transitional fossil that links the first theropods in the Jurassic and all subsequent therapods and modern birds. It is also likely that, based on its shared features between both theropod groups, Cryolophosaurus is an early tetanuran. This possibility is briefly discussed in the paper. It was also determined that Cryolophosaurus was an apex predator in its Antarctic environment, able to make swift movements and out-speed its prey to capture them. This is based on the animal’s astragalus (the bone in the foot between the shin and tarsals) and calcaneum (the bone just under the astragalus that forms the heel) being fused through ossification, or the growth of new bone material. Because dinosaurs walked on their tiptoes, this would not affect their stability as it would for humans. Additionally, those two bones are located right next to each other in dinosaur feet, which means that Cryolophosaurus only had one “ankle” bone where it would usually have had two. Taphonomic evidence (relating to the processes a body undergoes after death, including fossilization), supports the idea of Cryolophosaurus being an apex predator, as herbivore teeth have been found in its stomach. Sauropods, the long-necked dinosaurs, have also been found in the same formation as Cryolophosaurus, which could suggest they were also potential prey. Interestingly, the Cryolophosaurus holotype was found disarticulated with shed teeth nearby. These teeth are believed to have belonged to another Cryolophosaurus, suggesting that this dinosaur may have had cannibalistic tendencies. The characteristic crest of the dinosaur (Fig. 1) is believed to have been used as a display for attracting mates, with differences in bodily characteristics between males and females.

Why is this study important? Cryolophosaurus is an important dinosaur for theropod evolution because it is likely a transitional fossil connecting the earliest therapods to the tetanurans that came after. Understanding this dinosaur’s place in the phylogeny of theropods is important because it can elucidate various unknowns about their evolution. Cyrolophosaurus’ environment was also unique, being the only therapod yet discovered in Antarctica, which was a colder climate than what other dinosaurs in the Jurassic were living in. This provides a new perspective into dinosaur ecology, particularly through the lens of dinosaurs adapted for colder climates.

The big picture: Dinosaur paleontology is generally regarded by the public as being centered around the most popular Late-Cretaceous genera like Tyrannosaurus, Triceratops, and Velociraptor without much consideration for their ecology or even other dinosaurs from different periods. This study sheds light on one such lesser-known dinosaur, Cryolophosaurus, and states its importance to the phylogeny of theropod dinosaurs as well as its ecological role. Understanding the “niche” and lesser known dinosaurs is extremely important to the understanding of dinosaur paleontology, as those dinosaurs often provide much insight, not only into their evolution and development, but also to the unique nature and attributes of dinosaurs as a whole.

Citation: Yun, Changyu, 2020. An enigmatic theropod Cryolophosaurus: Reviews and comments on its paleobiology. VOLUMINA JURASSICA, 2019, XVII: 103–110

Reconstructing South Korea’s Cretaceous with the First Evidence of Crocodilian Tracks Found

First reports of Crocodylopodus from East Asia: implications for the paleoecology of the Lower Cretaceous

By: Martin G. Lockley, Jong Deock Lim, Hong Deock Park, Anthony Romilio Jae Sang Yoo, Ji Won Choi, Kyung Soo Kim, Yeongi Choi, Seung-Hyeop Kang, Dong Hee Kim, Tae Hyeong Kim.

Summarized by: Noel J. Hernandez G., a current geology senior undergraduat et at The University of South Florida. He plans to continue his education in paleontology by going to graduate school. He is hoping to eventually get his PhD in paleontology and become a professor that performs research throughout the world. He is also known as a video game enthusiast and enjoys science more than any person realistically should.

What data were used? The first samples of Crocodylopodus fossil footprints in the Cretaceous-age Jinju formation of South Korea, and previous samples of other kinds of crocodilian prints from the Mesozoic Era.

Methods: This study was conducted and made possible by many different organizations and study groups all working on the same project on the Jinju formation in South Korea. There were a multitude of samples gathered from four different dig sites, but this study focuses on the best-preserved samples. These samples were photographed using specialized 3D cameras and run through different software to create comprehensive elevation maps that could clearly show the indentations of the prints on the shale rock. Then, each visible print was studied and measured to identify possible the tracks that these animals made, this way, their walking patterns could be identified and matched with existing data to find the proper classification for them.

Results: There are many different kinds of prints that animals can leave behind as fossils. This could be due to different movement behaviors, different feeding methods, or even resting positions; we call fossils of these preserved behaviors, like these prints, ichnofossils. Crocodylopodus is one such type of footprint ichnofossil that was left behind by crocodile-like animals millions of years ago, though there are other kinds of common crocodile ichnofossils, such as Batrachopus and Hatcherichnus. In this study, these other common crocodile ichnofossils are used to compare these new samples of Crocodylopodus found with pre-existing data to try and understand what these tracks means for the organisms that produced them. The study finds that these prints are complete enough to reassemble the possible way that these animals walked. From this information, they found sufficient evidence to say that these crocodilians probably walked on land more than previously thought, unlike Hatcherichnus that demonstrate swimming. Crocodylopodus demonstrates walking in all of the samples found at these sites because of the types of sediments that they were imprinted on, representing shallow rivers and floodplains. Swimming tracks usually have small footprints with tail traces along with them, but Crocodylopodus does not show tail traces.

This changes the idea that most crocodilians in Eastern Asia during the Mesozoic were mostly aquatic animals, and this finding suggests that the trait of being aquatic or terrestrial primarily has been dependent on the kind of environments these animals lived in, as similar ichnofossils from different parts of the world show different habits in varying ecosystems.


Why is this study important? This study is part of a bigger ongoing study of a brand-new region of the world that has not been thoroughly studied for paleontology; specifically, the Jinju Formation is an area of South Korea that has not been heavily studied in the past. Many new species and recurrences of previously known species are coming up as more and more ichnofossils are uncovered. The more studies that are done on these samples, the closer we get to understanding how the paleoecology (i.e., how ancient animals interacted with each other and their environment) functioned there.

Slab with Crocodylopodus and other small mammal ichnofossil. A. Draw representation showing where each trace is located and the direction of the tracks. B. Low exposure picture of the actual fossil assemblage. C. Elevation imaging of the slab to show impression.

The big picture: These assemblages of trace fossils (ichnofossils) had not only the traces of crocodile-like animals, but they also had other kinds of trace fossils made by other organisms. There were many small animal prints and other kinds of reptile and amphibian prints as well, Crocodylopodus was only a part of the active biological community that existed in this area during the Cretaceous. Seeing how these crocodilians moved and lived among all of these other animals helps us understand the region better.

Citation: Martin G. Lockley, Jong Deock Lim, Hong Deock Park, Anthony Romilio, Jae Sang Yoo, Ji Won Choi, Kyung Soo Kim, Yeongi Choi, Seung-Hyeop Kang, Dong Hee Kim, Tae Hyeong Kim, 2020, First reports of Crocodylopodus from East Asia: implications for the paleoecology of the Lower Cretaceous, Cretaceous Research, Volume 111, 104441, ISSN 0195-6671, https://doi.org/10.1016/j.cretres.2020.104441

A new decapod species in Morocco gives insight into ancient Atlantic connections

First report of Early Eocene Decapods in Morocco: description of a new genus and a new species of Carpiliidae (Decapoda: Brachyura) with remarks on its paleobiogeography

by: Àlex Ossó, Julien Bailleul, Cyril Gagnaison

Summarized by: Haley Coe (she/her), a senior geology major at the University of South Florida. She plans to attend graduate school with a focus on paleoclimatology, with future hopes of becoming a research professor. She loves dancing, biking, being outdoors, and hanging out with friends. 

What data were used? All living organisms can be classified by the taxonomic rank. This system groups together individuals with increasingly broader likeliness through classifications of species, genus, family, order, class, phylum and kingdom. This article centers around a newly discovered species belonging to the order Decapoda– which include crustaceans such as crabs, lobsters, and prawns. 

This new genus and species, given the name Maurocarpilius binodosus (Figure 1), was discovered in Eocene-aged rocks from Northern Morocco. This discovery is important because the new species resembles other Eocene-age decapods from Portugal, Spain, and Italy. This resemblance suggests a possible connection between ancient waterways at the time of their existence. The authors of this article hypothesize that this new fossil is a physical link between the ancient Tethys Sea (located between modern-day Africa, Asia, and Europe) and the Atlantic-driven Bay of Biscay (located north of modern-day Portugal and Spain). This waterway could have allowed for easy migration of the decapod species. 

Methods: The discovered decapod fossils were found in a tectonically compressed fold-and-thrust belt (a mountainous area that occurs near certain plate tectonic boundaries) near Ouarzazate, Morocco. Through two fieldtrips by geologists of the UniLaSalle Institute in Beauvais, France, scientists discovered various specimens of this new species within the 400m thick interval of Eocene-age rock.

Scientists then categorized the recovered specimen based on physical differences. The newly discovered species, Maurocarpilius binodosus, had an interestingly oval-like, downturned, smooth, wide shell, among other unique qualities. This distinctive physical shape prompted scientists to propose an entirely new genus, Maurocarpilius. Despite the new classifications, the new Moroccan species showed very interesting similarities with decapods from other locations, such as those found in Portugal, Spain, and Italy.

Figure 1: This figure shows different views of three individual specimen of Maurocarpilius binodosus from the early Eocene of Morocco, with a scale bar of 10 mm.

Results: It can be estimated that Maurocarpilius binodosus is related to other decapod species found in northern Italy and the Iberian Peninsula in southwestern Europe. Both decapod populations decreased simultaneously, prompting scientists to wonder how the populations were physically connected.  It was assumed that the ancient landmass containing modern day Corsica and Sardinia (i.e., the Corso-Sardinian Continental Block) separated the Atlantic Ocean from the Tethys Ocean during the Eocene, which would have blocked any migration or exchange between the two regions. However, overwhelming similarities between decapod populations have encouraged scientists to forgo past assumptions and support the idea of an ancient waterway that linked the Atlantic to the Tethys. This connection most likely stretched along what is now the Iberian Peninsula. Modern coastlines, locations of decapod populations, and a proposed waterway connection can be seen in Figure 2.

Figure 2: This figure is a possible reconstruction of a connection between the Atlantic Ocean and the Tethys Sea during the early Eocene. Paying attention to (7) the present-day coastlines, (8) the discovery of Maurocarpilius binodosus, and (9) and (10) discoveries of related decapods, it is easy to imagine the proposed connection through the Corso-Sardinian Continental Block.

Why is this study important? This study is important because the presence of this new species increases the number of recorded decapod species. Morocco is less studied than other regions around the world, such as North America, and any new information considerably adds to knowledge of the geologic record. This discovery also helps paleontologists better understand how organisms may have migrated across oceans in the geologic record. If decapods were able to expand their geographic range due to this ancient waterway connection, other organisms were also likely to utilize it for migration. 

The big picture: Any advancement in paleontology is an advancement for science as a whole. Identifying an error in previous geographic reconstructions can influence future paleontologists, biologists, and scientists in general. This article is just a piece in the puzzle that is the geologic record, beyond just decapods. Paleontology has a broad influence on the understanding of plate tectonics. Discovering geographically separate populations of the same species, or closely related species, can give insight on how the Earth’s tectonic plates were once connected.

Citation: Ossó, À., Julien Bailleul, and Cyril Gagnaison (2020). First report of Early Eocene Decapods in Morocco: Description of a new genus and a new species of Carpiliidae (DECAPODA: Brachyura) with remarks on its paleobiogeography. Geodiversitas, 42(4), 47. doi:10.5252/geodiversitas2020v42a4

Comparing Diatom Paleo-Assemblages to Determine How Different Environments Affect Diversity in the Geological Rock Record

Comparison of Diatom Paleo-Assemblages with Adjacent Limno-Terrestrial Communities on Vega Island, Antarctic Peninsula 

By: Marie Bulínová, Tyler J. Kohler, Jan Kavan, Bart Van de Vijver, Daniel Nývlt, Linda Nedbalová, Silvia H. Coria, Juan M. Lirio, and Kateřina Kopalová

Summarized by: Dani Storms, a senior undergraduate student at the University of South Florida seeking to earn a degree in Geology with a concentration in geophysics. Dani changed her major from English to Geology her sophomore year after taking an Introduction to Earth Science class taught by Dr. Sarah Sheffield. Dr. Sheffield played a significant role in helping her discover a love and curiosity of how geology shapes our everyday lives. She is interested in furthering her education by attending graduate school to earn a master degree in the field of natural hazards, preferably landslides or avalanche control. She hopes to eventually obtain a PhD as well. Dani has loved being in the outdoors her whole life. In her free time, she enjoys hiking, camping, biking, crocheting, and spending quality time with her pup, Zion. 

What data were used? Diatoms are extremely abundant microfossils that are composed of silicon dioxide (SiO2) and can be used to reconstruct different environments through the rock record (i.e., paleoenvironments). This study used statistical analysis to discover if there was a significant difference of diversity within diatom assemblages from core samples derived from two Antarctic lakes, both with varying habitats. Core samples contain sediment that was deposited in paleoenvironments and obtained by drilling into the earth, and these can give insight into how climate has changed over time. The lakes were on Vega Island, in Devil’s Bay (Lake Anónima) and Cape Lamb (Lake Esmeralda). 

The samples were viewed under 100x magnification in order to determine diatom species. The species were then categorized into sub-Antarctic, Maritime Antarctic, and Continental Antarctic groups to determine their biogeographic distribution. Samples were taken from ponds, streams, mosses, and steep habitats to compare the core samples to modern day environments. However, not enough data could be collected from the stream, mosses, and steep habitats for a fair comparison. Therefore, the comparison of habitat differences on different sides of the island was restricted to only ponds.

In order to determine if there was a significant difference between the distributions, the study considered relative abundance, species richness and evenness in relation to diatom counts. Relative abundance refers to the percentage of diatoms found in each sample, richness is the number of species found in the sample, and evenness is comparison of the relative abundance of each individual species. 

Results: Overall, diatom assemblages varied in composition significantly, most likely due to the differences in waterway connections between sites and due to some sites being isolated. Between the categories, Maritime Antarctic Region contained the greatest number of species. Nearly 43% of the taxa found on Vega Island were Antarctic in distribution, while only 6% were found within the Antarctic Continent. Sub-Antarctic accounted for 3% and less than 1% were contributed by the Antarctic Region. The study then addresses the most abundant genus and species within Lake Esmeralda and Lake Anónima. Between the 132 species observed, 100 were found within Lake Esmeralda and only 32 species were found in both lakes. This means that Lake Esmeralda has a greater richness since it contained more species. 

Lake Anónima was found to be most similar to modern environments with the most noteworthy similarities being derived from streams on Devil’s Bay. However, there were several species found only within the core sample containing the paleo-assemblage. The paleo-assemblage consisted primarily of pond and stream species. For Lake Esmeralda, many of the taxa were not found within the modern environment at all. The taxa not found in the modern environment contained both aquatic and terrestrial species of diatoms. 

The authors of the study hypothesize that the connectivity of waterways and habitat type contributed to the difference in diatom assemblage structures. Lake Esmeralda is hydrologically disconnected, meaning it does not have connections to other bodies of water. The disconnect would result in less carbon being funneled into the lake from an outside source, which could alter the chemical makeup of the lake, allowing only certain species to survive as pH levels change. There is also a possibility that Lake Esmeralda might have had a higher preservation rate that allowed for a clearer comparison of paleo-assemblages versus modern, which would explain the higher amounts of diversity between the two. 

However, Lake Anónima is the complete opposite. It is well-connected to a stream that allows for the transportation of diatoms. It also has underground drainage that connects it to other lake-systems and surface streams. The study notes that even if the transport of diatom valves were to not occur, the connection of waterways would result in similar hydrochemistry between the connected water and lakes. This could have led to less viable conditions for preservation that could result in the lower amounts of diversity found. 

Figure 3: These boxplots visualize the comparison of species richness (S), Shannon Diversity (H’), and evenness (J’) between Esmeralda Lake and Anónima Lake core samples. The thicker black lines display median values.

Why is this study important? Looking at the conditions in which modern diatoms are found compared to that of paleo-assemblages can help construct a model, or standard, that can be applied to diatoms in the fossil record. This would allow us to reconstruct paleoclimates and trends associated with how they are affected by waterway connectivity. The differences in diatom-assemblages and species could be used as indicators of climate change. The different modern species that were found to be specific to ponds, mosses, and streams could give insight to what type of habitat fossilized diatoms would have been found in. 

The big picture: As the climate begins to warm and ice melts away, the connection between waterways will more than likely increase, this would cause a more uniform distribution of diatom assemblages and loss of diversity due to the similar chemical compositions of the water. The concept of creating a model that can be applied to the differences of diatom assemblages in modern and paleo-environments could essentially allow for paleoclimate and hydrological connectivity reconstruction. For instance, if we found a more uniform distribution in a general area, we might be able to determine if there was more connectivity between body of waters at some point in the geological record. Another example would be how on average, modern-day dry mosses contain fewer species of diatoms than wet mosses. Knowing this, we could analyze fossilized mosses to give insight into whether they would have been dry or wet. We could also use the findings of this study to determine what bioregion ancient diatoms would have been in based off species type and the diversity of the assemblage. 

Bulínová M, Kohler TJ, Kavan J, Van de Vijver B, Nývlt D, Nedbalová L, Coria SH, Lirio JM, Kopalová K. Comparison of Diatom Paleo-Assemblages with Adjacent Limno-Terrestrial Communities on Vega Island, Antarctic Peninsula. Water. 2020; 12(5):1340. https://doi.org/10.3390/w12051340

A Model of Sea Star Locomotion Using Tube Feet

Sea star inspired crawling and bouncing

by: Sina Heydari, Amy Johnson, Olaf Ellers, Matthew J. McHenry, and Eva Kanso

Summarized by Max Botwin, a geology major at the University of South Florida. He is currently a senior and will be graduating in Summer 2021. He is planning to move to Texas in May and looks forward to learning more about the world of geology as he works in the field. In Max’s free time, he enjoys playing with his dog Nilla and exploring the local trails around USF’s campus.

What data were used? The model was created by the researchers using parameters that were observed and measured from Asterias rubens sea stars, such as tube foot length during extension or contraction, density of water, buoyancy, and others.

Methods: To effectively model the locomotion of sea stars, the researchers adhered to what they called “hierarchical control laws”, which was the idea that the sea star controls the direction of movement for all of its tube feet, but the power and the recovery from a contraction is determined by each tube foot at an individual level. The researchers observed sea star movement and created a mathematical model to encompass as many parameters involved with tube foot locomotion as possible, including buoyancy of the feet, density of water, extension of tube feet, etc. Researchers were also able to quantify the pull of tube feet from extending and push from contracting using length of tube feet. Researchers were able to use their model and the data they collected to run many simulations with varying numbers of tube feet over different terrain to test the speed, stability, coordination, and overall effectiveness of tube feet locomotion. Examples of the simulations run by the researchers can be found in the link here.

Results: From this study, researchers have found that sea stars give a general command to the tube feet to move in a certain direction, but the power and the recovery from a contraction of the tube feet is controlled by the individual tube feet. This allows for a crawling movement from the sea star which allows it to travel across most terrain underwater and even swim. Tube feet are only effective underwater, since they work through jet propulsion where the tube foot will extend and fill a vacuole with water, then contract and squeeze out that water to propel themselves. The tube feet on sea stars are only related to one another by their attachment to the sea star and nothing else; there is no communication between the tube feet. Despite this, tube feet seem to fall into coordinated movements, where some tube feet are angled backwards and push forwards and some are angled forwards to “pull” the sea star forward. This pseudo coordination of movement is not limited to tube feet that are adjacent to one another, which means that tube feet can fall into the same locomotion “group”, even though they are not located near one another. When this occurs, the sea star goes from crawling to a bouncing gait which is much faster, but also requires more energy and was therefore found to only be useful under certain circumstances. Researchers saw that sea stars preferred to “pull” when moving vertically and pushing when moving horizontally.

Figure 2 from Heydari et al. (2020). (a) Common sea star used in the study called Asterias rubens. (b) Image of tube feet on Asterias rubens. (c) Image showing the bouncing gait of Asterias rubens. (d) Cross section of Asterias rubens to show the parts of its nervous system. (e) The anatomy of tube feet for mature sea stars. (f) The different actions that tube feet can undertake to perform locomotion. (g) This is a schematic of the mechanical rendition of a sea star including tube feet to help model sea star movement. (h) A flow chart to describe the hierarchical motor control used to command the tube feet in the mechanical sea star.

Why is this study important? This study is important because of the versatility that sea stars have in their movement across most surfaces underwater. If this locomotion can be accurately modeled, it can be recreated for robots, vehicles, or other such applications. The ability to traverse underwater terrain can have impactful applications in many industries that need to do work on the bottom of a body of water. Imagine a vehicle that is able to remain submerged and move along the ground while underwater to repair a bridge or to clean the bottom of a lake- the possibilities are endless!

The Big Picture: This study has shed light on unknown factors involved in how tube feet are controlled by the sea star and researchers were able to study and simulate sea star locomotion but were not able to match the complexity of real sea star locomotion. Answers beget more questions and that rings true here as well; the researchers were able to answer some of the “how” for sea star locomotion but were unable to explain the “why” behind it. This study can be used as a base for future models of the same type and can go further in detail using new parameters and improve their models to better depict the movement of tube feet on sea stars.

Citation: Heydari S, Johnson A, Ellers O, McHenry MJ, Kanso E. Sea star inspired crawling and bouncing. J R Soc Interface. 2020;17(162):20190700. doi:10.1098/rsif.2019.0700

Comparing humans and dogs: how two species in close communities relate

Trabecular bone in domestic dogs and wolves: Implications for understanding human self-domestication

by: Habiba Chirchir

Summarized by Maraley Santos. Maraley is an undergrad geology major at the University of South Florida. After graduating high school at the turn of the century, Maraley did what any student with an aptitude in science does when listening to others’ advice. She went to business school! After discovering a dislike of markets and business she put her college career on pause and reassessed life. Understanding her distaste of business but a love for data and science she decided to go back to school and major in her passion, earth science. Maraley believes it is never too late to learn, and this is the mantra she repeats to herself during all those restless nights of studying. She is supported by her wonderful partner in life Jeremy, their awesome daughter Leia, and her loyal pup Charlie. In her free time, she is an aquarist, hiker, rock collector, bassist, and is learning to build things that will work.

What data were usedSamples of the adult femoral head, highest point of the thigh bone, and distal bones, the ankles, of Canis lupus (gray wolf) and the largest Canis familiaris (domestic dog) breeds were acquired from the American Museum of Natural History (AMNH) in New York City, the Field Museum of Natural History (FMNH) in Chicago, and the National Museum of Natural History (NMNH) Smithsonian Institute in Washington D.C.. The 3D image results obtained from CT scans of these samples were analyzed and the qualitative results were summarized using numerous statistical methods. 

Methods: The robustness of bone, or trabecular bone fraction (TBF), was examined in this study to test the difference, if any, between grey wolves and their relatives, the domestic dog. The femora of both species were scanned using an X-ray CT at two separate facilities at the University of Texas (UT) and the University of Chicago (UC) while the distal tibiae (lower leg bone) were scanned using another type of CT scanner. The researchers hypothesized that domestic dogs have a more gracile, or delicate, bone structure their grey wolf relatives and they  scans hypothesized that the scans would show this. 

Results: TBF analyzation in the proximal (top part) femora and the distal tibiae of the domestic dog (C. familiaris)and the wolf  (C. lupus) revealed that the average TBF of these bones in wolves is greater than in domesticated dogs. Statistical analysis showed minimal error and boxplots helped visually assess the significant differences between the robustness of the bones in wolves and dogs, with wolves showing significantly thicker bones. Wilcoxon rank-sum tests (which essentially show if two populations show differences between them or not) showed the proximal femora (figure 1) and the distal tibia (figure 2) of the wolves showed greater TBF than of those in domesticated dogs. 

Figure 1 – proximal femora trabecular bone fraction

Why is this important? The analysis done in this study was used to test the hypothesis that domestic dogs have lower TBF (a more gracile or delicate bone structure) than their wolf ancestors due to self-domestication. In other studies, we see this pattern of gracility in human bodies when comparing it to our ancestors- our bones have also seen a trend of lower TBF through time. The ability of a dog to self-domesticate was due to their propensity of pro-sociality, or friendliness, with humans. This pro-sociality was reciprocated by humans, and the close relationship we see today between these two species is evident. As two species that domesticated alongside each other and live in close communities, we can study the effects of domestication in both species and make comparisons that can help us understand that process in humans. Unlike dogs, humans do not have such close living ancestors, so using relevant examples can help build that understanding.

Figure 2 – distal tibia trabecular bone fraction

The big picture: This study adds to the literature understanding self-domestication, a process that is not only behavioral, but also biological. Research has shown that self-domestication among most species lends to smaller body sizes, decrease in skeletal robusticity and possibly a decrease in bone density. Another hypothesis that is being studied is the effect domestication has on sedentism, the reduction of the need for a species to move long distances for survival (hunting for food and water resources), staying in one place. Studying domestication and understanding humans as being domesticated animals will help identify the long-term effects of sedentary lifestyle on our bodies, diseases that may arise of a lifestyle that isn’t compatible to our biology, and help expose the effects of extreme selection pressures among our best friend, the dog.

Citation: Chirchir, H. (2021). Trabecular bone in domestic dogs and wolves: Implications for understanding human self‐domestication. The Anatomical Record304(1), 31-41.

First signs of bird extinction from 40,000-1,700 years ago on Timor-Leste

First record of avian extinctions from the Late Pleistocene and Holocene of Timor Leste 

Summarized by Julie Sanchez, a senior at the University of South Florida who is majoring in Geology. She plans to graduate with her Bachelors of Science in summer of 2021 and wishes to continue her studies in graduate school, focused in petroleum geology. Outside of her academics, she loves to embrace her crafting side by painting or designing ceramic pieces. She also loves to walk trails and observe the beautiful rocks around her. 

What data were used? The researchers collected fossil birds from excavated sites in Timor Leste and then used collections of bird skeletons from the Smithsonian Institution’s National Museum of Natural History in Washington D.C. and Bergen University Museum in Norway to identify the newly found fossils. Here, the researchers were able to obtain information on what kinds of bird skeletons were resided in Timor, as well as bird skeletons that may have migrated to Timor. Research from a previous study of these skeletons provided useful information on the taphonomy of birds in Timor that added to the understanding of the results in this article.  

Methods: Researchers set up two locations of excavation in Timor: one in Jerimalaj and the second in Matja Kuru, both of which are located on the northeast part of Timor Leste (Figure 1).  Using mesh screens, the researchers were able to wet the screens and expose the bone/fragments found. As the fossils began to appear, they were measured with a digital caliper. The texture and porosity levels of the fossilized skeletons were also noted, to  help differentiate and categorize the juvenile bird bones from the mature bird bones. Radiocarbon dating was used to determine the ages of the bones/fragments found. 

This image shows the location of Matja Kuru and Jerimalai in Timor-Leste, where the fossils were excavated.

Results: The researchers recovered 416 bird bones from Jerimalai and Mataja Kuru. Throughout the excavation, there were more species found in Jerimalai than in Matia Kuru. Unfortunately, 65% of the fossils were not distinguishable. The reason for this was because most of bones were fragments, which only allowed them to narrow it down to being just a bird fossil. With the residual 147 identifiable fossilized specimens, it was determined that there were 29 bird species across 16 families. It was found that quails and buttonquail birds were more prominent at Maja Kuru, though they are considered rare in the city of Jerimalai today. There was also a crane species found that is extinct today. This represents the first known extinction event of birds in Timor. Their research also determined that although quails and buttonquails are morphologically similar, 29 different specimens were distinguished because of differences in bone structure. The results featured only a single fragment of Blue-breasted quail, S. chinensis, which was found in Jerimalai. Six specimens found in Jerimalai were determined as Metallic Pigeons. All of this information helps researchers better understand the modern day bird populations in this area/ 

Why is this study important? For about two hundred years, researchers have been studying the birds in this area. In spite of their research, the is still a big gap in regard to what kind of birds lived in Timor. This study allows the public to observe another perspective that was once “not there.” With the addition newly discovered bird species, it allows researchers to use this information in future studies of bird biodiversity, as well as understand what bird species coexisted during the Late Pleistocene and Holocene. 

The big picture: Knowing what types of birds existed on Timor can gives us insight about the environments the birds lived in, as well as climate change, and the relationships these animals could have had with other organisms. By understanding what bird species were once there, we can better understand what Timor was like during the Late Pleistocene and Holocene. We can also use this information to better understand global sampling, as many areas of southeast Asia are still underexplored for fossils. 

Citation: Meijer, Hanneke J. M., et al. “First Record of Avian Extinctions from the Late Pleistocene and Holocene of Timor Leste.” Quaternary Science Reviews, vol. 203, Jan. 2019, pp. 170–184. EBSCOhost, doi:10.1016/j.quascirev.2018.11.005.

A call for unifying methods within taxonomy of Tardigrada (the water bears)

Systematics of Tardigrada: A reanalysis of tardigrade taxonomy with specific reference to Guil et al. (2019)

by: James F. Fleming and Kazuharu Arakawa

Summarized by Joshua Golub, a senior at the University of South Florida in the department of geosciences. His specific interests in geology are geophysics and the use of near surface geophysics to gain a better understanding the physical aspects of observing earth processes. While attending the University of South Florida, Joshua has worked full time in the geotechnical engineering industry. Working in the geotechnical engineering industry in soil analysis has given him a perspective on soil properties, as well as utilizing these skills for government projects.  

What data were used? The data that was used came from several sources including from the recently published paper Guil et al. (2019), which was partially criticized by the authors of this paper for having incomplete data to determine taxonomic orders within tardigrades (Figure 1). Authors used the data from all of these sources to re-analyze and understand tardigrade taxonomy. Authors used a type of analysis called BUSCO to uncover the genetic patterns of highly conserved genes (i.e., genes that don’t change for a long period of time) of the species used in this study; BUSCO is a type of analysis that helps determine the full completeness of genes within groups of tardigrades. 

Figure 1: A picture of a Tardigrade (water bear). These organisms are generally 1mm long. Image: Schokraie et al., 2012.

Methods: Evolutionary trees can be constructed with two types of data; morphological data and molecular data. Morphological data comes from the specific external shape of the organism, whereas the molecular data is collected using the DNA of the organism. Often, researchers do not have both the molecular and morphological data to construct these evolutionary trees, but when researchers do have both, it can lead to much more accurate results. This paper tries to determine if the evolutionary relationships of tardigrades are better uncovered by using both molecular and morphological data. Recent articles used primarily morphological means to determine tardigrade taxonomy, so this article set out to see how adding molecular data would change the results. Authors in this paper tested to see if using only morphological data could negatively affect the branch lengths of an evolutionary tree, which explains when certain species diverge and become independent of one another (Figure 2). One specific hypothesis that the authors tested was from a previous paper, which used morphological evidence to elevate a group within Tardigrada to Apotardigrada. This paper included an analysis of genes to determine if the findings in Guil et al. (2019), the previous paper in question, had merit to make these major changes to the taxonomy of Tardigrada. They went about this by including several additional methods to the study, including genome sequencing (uncovering the patterns of DNA in each species tested), BUSCO, and a topology analysis, which is used to determine the branch lengths and when the common ancestors of certain tardigrade groups diverged (i.e., became separate populations). 

Figure 2: This figure shows the taxonomic tree for the four tardigrade orders, the branch lengths are inserted with each branch showing the results from each particular part of the data. Each color represents a particular method of data collection that was used. These numbers determine branch length, which helps determine when specific groups of tardigrades split and became distinct species.

Results: The authors had some parts of their assessments that agreed with Guil et al., the paper that used only morphological data, but the authors determined that their analyses don’t support establishing Apotardigrada as a formal taxonomic grouping. The assessment of this paper is that a consensus has not been met when approaching the organization of Tardigrada. Among all the additional analyses that the authors introduced into the discussion of Tardigrada taxonomy, what they make abundantly clear is that there needs to be a reanalysis in how we classify and name subdivisions of Tardigrada and unite a consensus of nomenclature (the names and terms that we use to discuss the group) that can avoid leading to further confusion into the research of these organisms. 

Why is this study important? There is a vast lack of consensus on how to properly organize the taxon of Tardigrada. The proposals that the authors make is for a unification of terms and research to further advance the research of a fairly mysterious organism, but in a way that will be the most accurate. 

The big picture: This call for action, to standardize nomenclature and research methods, is one that can be utilized in all fields of science. Depending on the region of the world, research can get stuck in echo chambers, creating their own terms that are not properly shared with the rest of the scientific community so that anyone who wants to study a particular subject, like Tardigrades, can do so effectively. The authors of this paper state that these holes that sometimes lie within research creates a hindrance on the study of the subject and calling for a consensus in any field of science is always a better route than tackling a topic on your own and exempting others’ research. 

Citation: Fleming, James F., and Kazuharu Arakawa. “Systematics of tardigrada: A reanalysis of tardigrade taxonomy with specific reference to Guil et al.(2019).” Zoologica Scripta (2021).