Lagerstatte Research Articles

Home on the range: A multi-isotope investigation of ungulate resource partitioning at Ashfall Fossil Beds, Nebraska, USA

During the Miocene (ca. 23.0–5.3 Ma), North America's Great Plains were a broad mosaic of savanna-woodlands inhabited by a diverse ungulate fauna. We investigated resource partitioning among ungulates at Ashfall Fossil Beds State Historical Park (henceforth “Ashfall”) in north-central Nebraska to establish how taxa shared the landscape. This mid-Miocene (11.86 ± 0.13 Ma) site preserves a watering-hole filled with volcanic ash that entombed hundreds of skeletons of medium- and large-bodied ungulates. We analyzed carbon (δ13C), oxygen (δ18O), and strontium (87Sr/86Sr) isotopes in enamel from seven species: the rhinoceros Teleoceras major (n = 13); three horses (Cormohipparion occidentale, Pliohippus pernix, and Pseudhipparion gratum; n = 3 each); two camels (Procamelus grandis and Protolabis heterodontus; n = 1 each); and one small ruminant artiodactyl (Longirostromeryx wellsi; n = 3). Carbon isotope data indicate that all seven ungulates foraged in open habitats dominated by C3 plants (enamel δ13CVPDB range from −9.6‰ to −6.9‰) with little to no evidence of C4 plant consumption. The overall range in δ18OVPDB values is ca. 6‰ (−7.6‰ to −1.3‰), while the range for 87Sr/86Sr is narrow (0.70864–0.70898). Horses have significantly higher δ18O and 87Sr/86Sr than T. major, which we suggest indicates horses foraged in relatively dry habitats, while T. major inhabited wet habitats with different strontium sources. Both camels isotopically resemble horses, and Longirostromeryx wellsi has intermediate 87Sr/86Sr and wide-ranging δ18O values. Plotting Teleoceras and co-occurring ungulates in a model that tests for semi-aquatic behavior using δ18O suggests that T. major from Ashfall was semi-aquatic; ecology and behavior may have varied among Teleoceras species living in different places at different times. This study exemplifies how 87Sr/86Sr data complement δ13C and δ18O analyses when reconstructing ancient environments; they can provide nuanced ecological information even in landscapes with homogeneous bedrock.

New paleofloristic and geochronological U–Pb zircon data in late Paleozoic deposits of the Matzitzi formation in southern Mexico

The fossil flora of the Matzitzi Formation, is a fluvial unit of late Paleozoic age exposed in southern Mexico, has been studied since the last century; however, the discovery of new plant elements during the last decade imposes a reevaluation of two aspects that have always been the subject of debate: the depositional age of the unit and the taxonomy of its paleoflora. The objective of the present work is to report new paleofloral records from two areas of the Matzitzi Formation as well as their chronological implications. The study sites are named Carretera and Coatepec. Nineteen genera and 11 species have been identified in beds from the Carretera site, whereas 23 genera and 16 species in beds from the Coatepec site. The analysis of floral assemblages of both sites shows that they share 49% of taxa. Ovopteris, Lesleya, Lobatopteris, and Trigonocarpus are unique to the Carretera site, while Coatepec is characterized by the presence of cf. Bjuvia, Schizoneura, and Velascophyllum. When analyzing the greatest ranges of the paleoflora awareness for the Carretera site indicates that deposition of these beds took place in a time interval that may span between Pennsylvanian and lower Permian. On the other side, the floral assemblage recovered from the Coatepec site indicates that the hosting beds were deposited in upper Permian time. U–Pb detrital zircon geochronology indicates that the maximum depositional age of the fossiliferous beds at the Carretera and Coatepec sites are of 276 ± 15 Ma and 254 ± 11 Ma, respectively. The integration of the paleontological and geochronological data obtained in this work suggests that the analyzed floral assemblage recovered from the Carretera site is of Kungurian age, whereas the one from the Coatepec site is of Lopingian age. Alternatively, we explore the possibility that deposits that are presently grouped within the Matzitzi Formation could be the vestiges of different fluvial cycles associated with different tectonic settings. Finally, the work on this unit has not finished, since there are still localities where its flora and age are still unknown.

And now for something completely random: spatial distribution of Dickinsonia on the Ediacaran seafloor

The oldest evidence of motile complex benthic multicellular organisms is found in Ediacaran aged rocks. At Nilpena Ediacara National Park (NENP), South Australia, one of the most iconic of such organisms, Dickinsonia, are found in abundance, with over 500 individuals preserved across the site's 33 in situ, fossiliferous beds. These beds vary in mat type and maturity, community diversity and population size. Here, we investigate six beds using spatial point pattern analysis (SPPA) to compare Dickinsonia spatial distributions between populations. Five populations were best-fit to a completely spatially random pattern, with a single outlier (TC-MM3) exhibiting signs of environmental heterogeneity. When distributions were examined in relation to other taxa, no indication of spatial competition was detected. Univariate and bivariate spatial distributions imply that Dickinsonia was generally not impacted by competition with other taxa, meter-scale environmental heterogeneity, or other external factors. These patterns hold when analyses were split between populations of large and small individuals, and these two size cohorts had no measurable effect on each other's spatial distributions. Additionally, we find no indication of intraspecific competition for Dickinsonia or any change in the preferred resources or habitats with growth. These results suggest that the anactualistic environmental conditions produced by ubiquitous organic mats present across Ediacaran seafloors at NENP provided such abundant nutrients that Dickinsonia did not have to compete for resources at the meter scale. These results further inform community-scale dynamics of Earth's earliest complex ecosystem.

Eocene mafic alkaline volcanism in north Central Iran; Signatures of development and subsequent melting of a pyroxenite mantle source

Volcanic rocks from the Miami-Davarzan area are basalts to trachyandesites interlayered with fossiliferous beds and bear significant implications on the Eocene geodynamic evolution of northern central Iran. The rocks constitute two distinct groups, a low-Nb and a high-Nb suite. The least evolved low-Nb suite includes clinopyroxene-olivine phyric samples and is characterized by higher CaO and lower Al2O3 as compared to peridotite partial melts. The high-Nb suite includes more evolved plagioclase-clinopyroxene phyric samples. Fractional crystallization modeling using least-squares mass balance calculations for major elements suggests that the high-Nb suite was formed from a low-Nb parental melt by differentiation of a clinopyroxene-dominated mineral assemblage. The Miami-Davarzan volcanic rocks are characterized by significant large ion lithophile elements (LILE) and light rare earth elements (LREE) enrichment and high field strength elements (HFSE) depletion, which are typical signatures of subduction-related settings. Immobile, highly to moderately incompatible elements such as NbTa, LaCe, PrNd are higher in the Miami-Davarzan volcanic rocks as compared to the typical magmatic arcs, which is an indication of slab melt involvement and metasomatism of the mantle source. The Sr-Nd-Pb isotopic data also confirm a common mantle source involving the addition of subducted sediments into a depleted mantle source for both the low-Nb and high-Nb suites. The geochemical characteristics such as high CaO, low Al2O3, and the isotopic data can be best explained by derivation of the low-Nb suite parental melt from a pyroxenite mantle source. The pyroxenite mantle source was probably developed as a result of interaction between shallow depleted mantle and slab plus sediment-derived melts. It is suggested that the extensional phase that dominated the northern central Iran during the Eocene prompted partial melting of a pyroxenite mantle source.

The research history of the Middle Triassic fishes of Monte San Giorgio: getting out of the shadow of aquatic reptiles

Around the middle of the nineteenth century, Italian palaeontologists began to investigate fossils of fishes and reptiles from the Middle Triassic outcrops in the vicinity of Monte San Giorgio (Canton Ticino, Switzerland). In 1924, researchers from the University of Zurich started their scientific excavations on the Swiss side. The many fish fossils found since then have often stood in the shadow of the more spectacular and mostly larger fossils of various aquatic reptiles. Beginning around 1980 the fish fossils in the collection of the Palaeontological Institute and Museum of Zurich University have subsequently been brought out of this shadow. The picture presently emerging is that of a species rich fish fauna located in six different fossiliferous beds of Anisian and Ladinian age with a few chondrichthyan, some coelacanth and a wealth of different actinopterygian taxa, many of them well preserved. The ongoing work not only results in taxonomic and systematic novelties, but gives also new insights into their palaeobiology, palaeoecology and palaeobiogeography.

The Falls of the Ohio River: America's First Fossil Bed

Abstract The Falls of the Ohio is a world-renowned geoheritage site of palaeontological and geological importance that also played key roles in the cultural and historical development of America. Studied by geologists for over two centuries, over 600 species of fossils are known from the site, hundreds of which were first described here. Beyond geology, the Falls of the Ohio can also be considered the origin and ending of the Lewis and Clark expedition, as well as an important location for naturalists and educators. A treasure of natural and human history and a National Natural Landmark, this spectacular 220 acre (89 ha) expanse of fossiliferous bedrock is worthy of ongoing study and protection.

A new mayfly subfamily sheds light on the early evolution and Pangean origin of Baetiscidae (Insecta: Ephemeroptera)

The family Baetiscidae Edmunds & Traver, 1954 is recognisable among mayflies due to its bizarre larvae, equipped with a robust and spiked thoracic notal shield covering part of the abdomen up to sixth segment. Originally being described as extant species from the USA and Canada, Baetiscidae were later found in the fossil record as well, specifically in Cretaceous of Brazil and Eocene Baltic amber. An enigmatic piece of fossil evidence are two larvae from the Early Cretaceous Koonwarra Fossil Bed in Australia, which have been presumed as attributable to Baetiscidae and briefly discussed in previous studies. In the present contribution, we reinvestigate these fossils and confirm their attribution to the family Baetiscidae. These larvae are depicted and described as Koonwarrabaetisca jelligen. et sp. nov. and Koonwarrabaetisca duncanisp. nov. For both Cretaceous genera Protobaetisca Staniczek, 2007 and Koonwarrabaetiscagen. nov. we establish a new subfamily Protobaetiscinae subfam. nov. within the family Baetiscidae, based on the presence of markedly shortened thoracic sterna. The phylogenetic position of newly described subfamily is clarified using a cladistic analysis; Protobaetiscinae subfam. nov. forms a monophyletic clade, sister to Baetiscinae. The confirmation of the distribution of Baetiscidae in the Cretaceous of Australia suggests almost worldwide distribution of this family in the deep time. Given their limited dispersal abilities, this distributional pattern can be best explained by the Pangean origin for this family, moving the time of their origin at least to the Early Jurassic. The larvae of Koonwarrabaetiscagen. nov. exhibit the same ecomorphological specialization as the rest of Baetiscidae, that supporting with a high probability their lifestyle similar to extant Baetisca Walsh, 1862. The larvae probably lived in the flowing water with stony substrate densely covered by filamentous algae, and in the places of accumulation of dead plant and algae matter during the last instars. Thus, Koonwarrabaetiscagen. nov. could be the allochthonous component in mayfly fauna of the Koonwarra paleolake.

Updating conservation techniques for paleontology collections associated with Florissant Fossil Beds National Monument

Updating conservation techniques for paleontology collections associated with Florissant Fossil Beds National Monument

Mazon Creek fossils brought to you by coal, concretions and collectors

Abstract The late Carboniferous (Middle Pennsylvanian, ∼307 Ma ago) Mazon Creek Lagerstätte found in northern Illinois, USA, is unique for its exceptional biotic diversity as well as the human endeavours, both professional and avocational, that brought vast numbers of fossils and new species to science. In 1997, the Mazon Creek Fossil Beds, exposed along the Mazon River near Benson Road, Morris, IL, became a National Historic Landmark. The fossils are preserved in siderite (iron carbonate, FeCO 3 ) concretions within the lower 3–8 m of the Francis Creek Shale Member of the Carbondale Formation, and often retain outlines of original soft tissues. The Mazon Creek biota includes over 465 animal and 350 plant species representing more than 100 orders, which is attributed to the preservation of organisms from multiple habitats and the large number of specimens collected. That phenomenon was made possible by coal extraction bringing concretions to the surface and highly motivated amateur collectors pursuing them. Some of the formerly mined areas continue to draw collectors and are preserved as part of the Mazonia-Braidwood State Fish and Wildlife Area. The fossils, fossil collectors and collection sites are a significant part of the cultural and scientific geoheritage.

The first troodontid (Dinosauria: Theropoda) from the Upper Cretaceous Baruungoyot Formation of Mongolia

ABSTRACT Among non-avian dinosaurs, troodontids are relatively rare but diverse. The Nemegt Basin in the Mongolian Gobi Desert, which incorporates three of the most fossiliferous beds in the world, is one such region with high troodontid diversity and has also produced eight troodontid taxa until now. The diversity of troodontids is biased towards the two formations, Nemegt and Djadochta. Despite its rich vertebrate fossil record, no troodontids have been described from the Baruungoyot Formation. This faunal absence is perplexing as the Baruungoyot Formation has often been considered intermediate between the other two units in stratigraphy and paleoenvironment, but there are no definite troodontid materials that could fill this ‘gap.’ Here, we report a new troodontid, Harenadraco prima gen. et sp. nov., from the Baruungoyot Formation in Hermiin Tsav, Mongolia. It is represented by an incomplete skeleton that mainly consists of partially articulated left hind limb elements. Harenadraco is small and lightly built like other troodontids, but its tarsometatarsus exhibits extreme slenderness comparable only to Philovenator among cursorial non-avian maniraptorans. It also implies high cursoriality that could be an adaptation of Harenadraco to its environment where potential prey animals like mammals and predators such as eudromaeosaurs were likely to be agile. The discovery of Harenadraco confirms the presence of troodontids in all three formations in the Nemegt Basin. http://zoobank.org/urn:lsid:zoobank.org:pub:0981D708-986B-4B81-8809-E239DF9E8444

The Zambia Rift Valley research project: Exploring human evolution at the crossroads of Africa

Key evolutionary events in hominin evolution occurred between 3.5 and 2.4 Ma, including the origins of flaked tool technology and the first appearance of the genera Homo and Paranthropus. This period remains poorly understood, however, because deposits of this age are rarely exposed across Africa. The Luangwa River Valley of eastern Zambia is part of the southernmost extension of the East African Rift System; a fossil femur from South Luangwa, identified as Theropithecus cf.darti, hints at the presence of fossiliferous beds of this age in the Luangwa Valley. Additionally, Middle Pleistocene fossils and Early and Middle Stone Age artifacts have also been recovered in sediments adjacent to the Luangwa River. Fossils from these deposits could contribute data on the diversification of hominins and mammals that occurred during the Plio-Pleistocene. The Luangwa River also supports a rich modern mammalian community that represents a critical analogue for reconstructing hominin paleoenvironments. However, no systematic ecological characterizations of living or past mammalian communities of the Luangwa River Valley have been completed. The newly initiated Zambia Rift Valley Research Project (ZRVRP) will analyze the ecology of modern and fossil Luangwa River mammalian and human communities using dental microwear, enamel and collagen isotopic composition, the distribution of bones, fossils, and vegetation on the landscape, and archaeological materials. Patterns of paleoenvironmental change, climatic seasonality, and hominin landscape use over time will provide important comparative context for other Plio-Pleistocene sites. Here, we describe the goals, methods, and community engagement of the ZRVRP, and some challenges involved in launching new paleoanthropological field research.

Large euarthropod carapaces from a high latitude Cambrian (Drumian) deposit in Spain.

Deposits preserving non-biomineralized tissues and animals provide an unrivalled opportunity to study the evolution and radiation of early animal life. Numerous sites of Cambrian age are known from North America (Laurentia) and South China (East Gondwana), which provide a high resolution picture of the fauna at low latitudes. By contrast, our knowledge of Cambrian animals from higher latitudes is relatively poor. This patchiness in our knowledge of animal life during the radiation of animals in the Cambrian period limits our ability to understand and detect palaeogeographic trends and does not provide a full appreciation of animal diversity at this time. Here we report a new middle Cambrian (Drumian) site preserving lightly sclerotized euarthropod carapaces, sponges and palaeoscolecids near the village of Mesones de Isuela in the Iberian Chains (Spain). We describe three bivalved euarthropod carapace morphs, two comparable to those described from the only other high latitude Drumian deposit, the Jince Formation (Czechia), and one distinct from previous discoveries. These new findings highlight the importance of high latitude Gondwana Konservat Lagerstatten for understanding the palaeogeographical aspect of the radiation of early animals and suggest that bivalved euarthropods at high latitudes were larger than those at lower latitudes during the Cambrian.

A chronostratigraphic and biostratigraphic framework for the Yanliao Biota of northeastern China: Implications for Jurassic terrestrial ecosystems and evolution

The terrestrial Yanliao Biota in northeastern China represents a Jurassic biodiversity hotspot. Abundant and diverse fossils include the oldest known representatives of several groups of plants, invertebrates, and vertebrates that thrived in a forest ecosystem under a humid and warm climate. Since the early 21st century, discoveries associated with the Yanliao Biota have significantly improved our understanding of Jurassic terrestrial ecosystems. However, a robust chronostratigraphic framework is required to calibrate the biota with key evolutionary events and to improve understanding of possible links between evolution and tectonism. In this paper, we report novel 40Ar/39Ar ages for two tuff layers (161.4 ± 0.8 Ma and 161.6 ± 0.6 Ma) positioned directly above the less-studied but salamander fossil-rich beds in Reshuitang, near Lingyuan, Liaoning Province, China. These new age data improve knowledge of the timing of diversification of early salamanders. We also review all reported age data and summarize significant fossils from classic Yanliao outcrops. Our study indicates that the Reshuitang fossil beds were deposited slightly later than the well-known Daohugou fossil beds situated ∼15 km away in Inner Mongolia and somewhat earlier than the Linglongta fossil beds in western Liaoning Province. These findings advance understanding of the Jurassic world during an episode of pronounced climatic warming.

Fossil leaves, woods, gastropods, and a crocodile tooth: Is the Amagá Formation worth exploring?

We have generated a spatial framework for macrofossil searching based on the current knowledge of fossil localities and fossil beds reported for the Amagá Formation in the northwestern Andes in Colombia. Our results show that twenty-three fossil localities and ninety-five fossil beds are distributed along this sedimentary succession. Preservation potential is higher in the Lower Member, given the high accommodation space and the dominance of a meandering fluvial system, compared with the Upper Member, where there was less accommodation space with a braided fluvial system controlling it. Our findings show that even though paleontological studies are null in this area, there are several options to find terrestrial macrofossil assemblages that will allow us to investigate the possible biological role of global climatic changes and regional tectonics in the Neotropical biomes based on the Amagá Formation.

Facies character and evolution of a mixed carbonate–siliciclastic shelf: Upper Triassic–Lower Jurassic succession in the eastern Northern Calcareous Alps (Stumpfmauer, Austria)

Western Tethys sedimentary successions constitute fundamental archives of Late Triassic–Early Jurassic environmental, carbonate production and tectonic changes. During the Late Triassic, the Northern Calcareous Alps (Austria) belonged to the Western Tethys passive margin, characterised by the deposition of the early-dolomitized peritidal Hauptdolomit (Norian) adjacent basinward to the Dachstein carbonate shelf and passing upward to the mixed carbonate–siliciclastic Kössen Formation (Upper Norian–Rhaetian). The Kössen Fm. was subdivided into the lower shallow-water Hochalm Member and the upper Eiberg Member, accumulated in an intraplatform basin coeval to shallow-water carbonates (Upper Rhaetian Limestone). The Eiberg Mb. and overlying Jurassic strata were extensively studied as a continuous marine record across the Triassic/Jurassic boundary. In contrast, shallow-water successions, time-equivalent to the Eiberg Mb. and Upper Rhaetian Limestone, located North of the Eiberg Basin, are poorly investigated. This study focusses on the approximately 350 m thick Norian to Lower Jurassic succession cropping out in the eastern Northern Calcareous Alps (Stumpfmauer). The 32 distinguished lithofacies compose seven, vertically superimposed, sedimentary units (A–G), belonging to the Hochalm Mb. of the Kössen Fm. (Unit A peritidal cyclothems, Unit B claystone/marlstone with fossiliferous beds, Unit C coral boundstone to floatstone), Upper Rhaetian Limestone (Unit D subtidal cyclothems with claystone), shallow-water carbonate strata transitional to Lower Jurassic (Unit E ooidal coated grain peloidal grainstone with basal transgressive lag, Unit F bivalve-rich, microbialite and oncoidal lithofacies, previously attributed to the Upper Rhaetian Limestone) and Hettangian–Sinemurian Kalksburg Fm. (Unit G cross-laminated coated grain peloidal grainstone with quartz and chert). The detailed lithofacies characterisation presented in this study contributes to the knowledge on the Northern Calcareous Alps stratigraphy and depositional environments across the Triassic/Jurassic boundary. The identified sedimentary units can be framed in the evolution of Western Tethys and share similarities with depositional systems from the Western Carpathians, Transdanubian Range, Southern Alps and Dinarides suggesting coherent sedimentary response and environmental, climate and tectonic controls in different palaeogeographic domains.

Did the Late Ordovician mass extinction event trigger the earliest evolution of ‘strophodontoid’ brachiopods?

Abstract‘Strophodontoid’ brachiopods represented the majority of strophomenide brachiopods in the Silurian and Devonian periods. They are characterized by denticles developed along the hinge line. The evolution of denticles correlated with the disappearance of dental plates and teeth and were already present when the clade originated in the Late Ordovician. Specimens ofEostropheodonta parvicostellatafrom the Kuanyinchiao Bed (early–middle Hirnantian, uppermost Ordovician) in the Hetaoba Section, Meitan, Guizhou Province, South China, display clear fossil population variation, during a process of loss of dental plates and the development of denticles. Three phenotypes ofE. parvicostellataare recognized in a single fossil bed, likely heralding a speciation process. Non‐metric multidimensional scaling (NMDS) based on five key characters of genera of the Family Leptostrophiidae shows a much wider morphospace for Silurian genera than for those in the Devonian. Phylogenetic analysis of the Family Leptostrophiidae supports the NMDS analysis and mostly tracks their geological history. The fossil population differentiation inE. parvicostellatadiscovered between the two phases of the Late Ordovician mass extinction event (LOME) linked to a major glaciation, suggests a Hirnantian origination of the ‘strophodontoid’ morphology, and links microevolutionary change to a macroevolutionary event.

Frond orientations with independent current indicators demonstrate the reclining rheotropic mode of life of several Ediacaran rangeomorph taxa

AbstractFossils from the deep-sea Ediacaran biotas of Newfoundland are among the oldest architecturally complex soft-bodied macroorganisms on Earth. Most organisms in the Mistaken Point–type biotas of Avalonia—particularly the fractal-branching frondose Rangeomorpha— have been traditionally interpreted as living erect within the water column during life. However, due to the scarcity of documented physical sedimentological proxies associated with fossiliferous beds, Ediacaran paleocurrents have been inferred in some instances from the preferential orientation of fronds. This calls into question the relationship between frond orientation and paleocurrents. In this study, we present an integrated approach from a newly described fossiliferous surface (the “Melrose Surface” in the Fermeuse Formation at Melrose, on the southern portion of the Catalina Dome in the Discovery UNESCO Global Geopark) combining: (1) physical sedimentological evidence for paleocurrent direction in the form of climbing ripple cross-lamination and (2) a series of statistical analyses based on modified polythetic and monothetic clustering techniques reflecting the circular nature of the recorded orientation of Fractofusus misrai specimens. This study demonstrates the reclining rheotropic mode of life of the Ediacaran rangeomorph taxon Fractofusus misrai and presents preliminary inferences suggesting a similar mode of life for Bradgatia sp. and Pectinifrons abyssalis based on qualitative evidence. These results advocate for the consideration of an alternative conceptual hypothesis for position of life of Ediacaran organisms in which they are interpreted as having lived reclined on the seafloor, in the position that they are preserved.

A fossil beech fern (cf. <i>Phegopteris</i> (C. Presl) Fée) from Driftwood Canyon Provincial Park, British Columbia

Ferns are important components of the biodiversity of wet forests across Canada, and the fossil record offers insights into the origins of fern diversity and biogeography. In 1967, Driftwood Canyon Provincial Park in north-central British Columbia was declared an Eocene Epoch plant, insect, fish, bird, and mammal fossil site of national scientific significance to preserve the Driftwood Creek fossil beds. The fossil plants from this important fossil site remain largely unknown. Here, a first record of a beech fern from the Eocene of British Columbia—morphologically comparable to the Phegopteris connectilis group—is illustrated, further revealing the past biodiversity of ancient British Columbia. The absence of sori and other key anatomical characters prevents definitive identification. Today, the circumpolar to temperate species Northern Beech Fern (Phegopteris connectilis) is widespread across British Columbia, occurring in wet coniferous forests; other members of the P. connectilis group also occur in temperate climates.

Tropical Arctic

Tropical Arctic asks us to imagine the Arctic as a lush, green paradise (think Miami) through the story of an expedition to Greenland and the subsequent analysis of the fossils collected there by a team including an artist, botanist, and paleobotanist. The expedition team was specifically interested in a mass extinction event that occurred during a period of catastrophic climate change 200 million years ago between the Triassic and Jurassic periods. The team targeted particular fossil beds to help them find the answers they were looking for. They collected more than a metric ton of fossils and used the data to put together a picture of what the ancient Arctic ecosystem looked like by determining which plants were dominant and which were rare both before and after the mass extinction. They then used the fossils to create three-dimensional models to increase their understanding of the plant characteristics. This provided insight into which plants were resilient in the face of change and which characteristics might have contributed to that resilience. The team coupled this evidence with laboratory evidence on extant plants that measured their response to conditions similar to ancient Earth’s.What was a dense forest canopy in the Triassic transitioned to lower-growing plants that had to survive harsh atmospheric conditions in addition to frequent fire in the early Jurassic. When conditions stabilized, those plants able to survive could thrive. The team hypothesized that the slow rate of change of Earth’s conditions contributed to the plants’ ability to migrate, essentially germinating where conditions were favorable. Certain species were better adapted for conditions on one side of the boundary. The book ends with lessons for the future, pinpointing the magnitude of temperature change associated with a reduction in biodiversity and loss of species and what it might mean for Earth’s future.While the photographs and illustrations are beautiful, I found the story hard to follow. At the end of the book, I wished some of the information presented in Chapter 4 had been presented earlier. I was less motivated to learn about the expedition and all of the fossils collected because I didn’t know the story of the conditions on Earth that led to and followed the mass extinction. Had that context come first, it would have provided framing for the expedition, sparking curiosity about what the team found. I found myself wanting a map or a timeline to help me track Earth’s history both spatially and temporally.It may be beyond the scope of this book, but I was left wondering about the conditions in the Arctic that allowed all that plant life to grow in the first place. How does the 40,000-year cyclical change in the Earth’s tilt play into the story of energy and matter in the Arctic? Does that explain why it was lush there once but cold and icy there now? And how will the anthropogenic changes we have made to Earth’s system interact with that natural cycle?Today, many high school biology teachers are tasked with integrating Earth and space science standards into their curricula. Using historical events that caused changes to Earth’s system as phenomena can help students understand the flow of energy and matter and provide a context for understanding why the mechanisms of photosynthesis and cellular respiration are so important. Tropical Arctic is a beautiful text and illuminates a part of Earth’s history that I knew little about. On its own, it is missing necessary pieces to spark the interest of someone who lacks expertise in the field, but it would be a worthwhile complement to other texts on the topic.

Fossil marsh beetle larvae (Scirtidae: Coleoptera) from the Lower Cretaceous (Aptian) Koonwarra Fossil Bed of Victoria, Australia

The well-preserved fossils of larval Scirtidae (Coleoptera) from the Lower Cretaceous (middle to upper Aptian) Koonwarra Fossil Bed of South Gippsland in Victoria, Australia, were examined and compared with larvae of modern species. The discernible diagnostic features of the fossils conform to the extant genus Nektriscyphon. This is the earliest known evidence for scirtids in the fossil record, and suggests that little morphological change has taken place in these still water-dwelling (lentic) larvae over the last ca 120 million years. Key character states of the fossil Nektriscyphon are compared and the palaeoecological implications discussed. Chris H. S. Watts [chrisw@samuseum.sa.au] and Howard Hamon [howard@hamon.id.au], Entomology Section, South Australian Museum, Adelaide, 5000, Australia.