Early Cenozoic evolution of the latitudinal diversity gradient

We are beginning to appreciate that the huge radiations of both marine and terrestrial taxa in the aftermath of the K/Pg mass extinction event were concentrated largely, but not exclusively, in the low-latitude and tropical regions. This in turn means that significant latitudinal diversity gradients were developed well before the onset of global cooling at the Eocene/Oligocene boundary. Net rates of evolutionary radiations were significantly higher through the Early Paleocene – Middle Eocene interval (i.e. ~62–42 Ma) in the tropics than at the poles but this may be due as much to their retardation in the latter regions as to their acceleration in the former. At least in the marine realm, polar assemblages are characterised by the phenomenon of high dominance/low evenness, and it is thought likely that this is due to the extreme seasonality of primary production at the base of the food chain. Many modern polar marine organisms are de facto trophic generalists and occupy significantly broader ecological niches than their tropical counterparts. Although we cannot dismiss the roles of both temperature and area in promoting tropical diversity, it could well be that LDGs are just as much the product of a latitudinal gradient in the seasonality of primary productivity. Such a gradient would have operated in both greenhouse and icehouse worlds

The bivalve Anopaea (Inoceramidae) from the Upper Jurassic-lowermost Cretaceous of Mexico

In Mexico, the Upper Jurassic to lowermost Cretaceous La Casita and coeval La Caja and La Pimienta formations are well-known for their abundant and well-preserved marine vertebrates and invertebrates. The latter include conspicuous inoceramid bivalves of the genus Anopaea not formally described previously from Mexico. Anopaea bassei (Lecolle de Cantú, 1967), Anopaea cf. stoliczkai (Holdhaus, 1913), Anopaea cf. callistoensis Crame and Kelly, 1995 and Anopaea sp. are rare constituents in distinctive Tithonian–lower Berriasian levels of the La Caja Formation and one Tithonian horizon of the La Pimienta Formation. Anopaea bassei was previously documented from the Tithonian of central Mexico and Cuba, while most other members of Anopaea described here are only known from southern high latitudes. The Mexican assemblage also includes taxa which closely resemble Anopaea stoliczkai from the Tithonian of India, Indonesia and the Antarctic Peninsula, and Anopaea callistoensis from the late Tithonian to ?early Berriasian of the Antarctic Peninsula. Our new data expand the palaeogeographical distribution of the high latitude Anopaea to the Gulf of Mexico region and substantiate faunal exchange, in the Late Jurassic–earliest Cretaceous, between Mexico and the Antarctic Realm

Origin of the tropical-polar biodiversity contrast

Aim: The aim was to investigate the evolutionary origins of the striking biodiversity contrast between high- and low-latitude regions in the present day. Is this a relatively recent phenomenon, causally linked in some way to the greenhouse–icehouse transition and onset of global cooling c. 34 Myr ago, or does it have deeper temporal roots and thus other potential causes? Location: Early Cenozoic fossil assemblages from two tropical and one polar region, and modern counterparts from various tropical localities and Antarctica. Time period: The Cretaceous–Palaeogene (K/Pg) mass extinction event, Early Cenozoic (Palaeocene–Eocene) and the present day. Major taxa studied: Shelf-depth marine Mollusca; the four richest modern benthic clades: Imparidentia, Pteriomorphia, Neogastropoda and Littorinimorpha. Methods: The K/Pg mass extinction and subsequent recovery was compared between two tropical and one polar region at four distinct stratigraphic intervals. Taxa were identified to species level and assigned to principal families within the four largest benthic molluscan clades. Taxon counts were compared between the three regions at each level and also compared with standardized tropical and polar modern faunas. Results: The mass extinction was followed by a distinct 25 Myr phase of evolutionary radiation, during which the tropical–polar contrast in the taxonomic composition of all four clades was strongly enhanced; as the global molluscan fauna expanded, it differentiated into distinct low- and high-latitude components. Main conclusions: A marked differentiation of tropical and polar molluscan faunas occurred in the immediate aftermath of the K/Pg mass extinction; it is likely that, at least for the two bivalve clades investigated, this differentiation was initiated well within the Mesozoic era. The greater antiquity of the tropical–polar split suggests that it was not the product of any single controlling factor during the Cenozoic

The Paleocene of Antarctica: dinoflagellate cyst biostratigraphy, chronostratigraphy and implications for the palaeo-Pacific margin of Gondwana

The Paleocene (66–56 Ma) was a critical time interval for understanding recovery from mass extinction in high palaeolatitudes when global climate was warmer than today. A unique sedimentary succession from Seymour Island (Antarctic Peninsula) provides key reference material from this important phase of the early Cenozoic. Dinoflagellate cyst data from a 376 m thick stratigraphical section, including the Cretaceous–Paleogene boundary, is correlated with biozones from New Zealand, the East Tasman Plateau and southeastern Australia. A detailed age model is suggested for the López de Bertodano (LDBF) and Sobral (SF) formations based on dinoflagellate cyst biostratigraphy and U-Pb dating of zircons, supported by correlated magnetostratigraphy and strontium isotope values from macrofossils. The top of the LDBF is confirmed as latest Maastrichtian to earliest Danian (~ 66.2–65.65 Ma) in age. The overlying SF is mostly Danian in age, with an inferred hiatus near the top overlain by sediments dated as? late Thanetian. Rare Apectodinium homomorphum first appear in the uppermost SF; the first in situ record from Antarctica. The distribution of marine and terrestrial fossils from uppermost Cretaceous to Eocene sediments in Patagonia, Antarctica, New Zealand and Australia required both sea and land connections between these fragments of Gondwana. Fossil evidence and reconstructions of Antarctic palaeogeography and palaeotopography reveals evidence for persistent embayments in the proto-Weddell and Ross Sea regions at this time. We conclude that a coastal dispersal route along the palaeo-Pacific margin of Gondwana could explain the fossil distribution without requiring a transAntarctic strait or closely spaced archipelago. A region in the West to East Antarctic boundary zone, elevated until the early Paleogene, perhaps acted as a site for high elevation ice caps. This supports fossil, geochemical and sedimentological evidence for cold climate intervals and significant sea level falls during the Maastrichtian and Paleocene

Essential Oils and Their Principal Constituents as Antimicrobial Agents for Synthetic Packaging Films

Spices and herbal plant species have been recognized to possess a broad spectrum of active constituents that exhibit antimicrobial (AM) activity. These active compounds are produced as secondary metabolites associated with the volatile essential oil (EO) fraction of these plants. A wide range of AM agents derived from EOs have the potential to be used in AM packaging systems which is one of the promising forms of active packaging systems aimed at protecting food products from microbial contamination. Many studies have evaluated the AM activity of synthetic AM and/or natural AM agents incorporated into packaging materials and have demonstrated effective AM activity by controlling the growth of microorganisms. This review examines the more common synthetic and natural AM agents incorporated into or coated onto synthetic packaging films for AM packaging applications. The focus is on the widely studied herb varieties including basil, oregano, and thyme and their EOs

The early origin of the Antarctic Marine Fauna and its evolutionary implications

The extensive Late Cretaceous – Early Paleogene sedimentary succession of Seymour Island, N.E. Antarctic Peninsula offers an unparalleled opportunity to examine the evolutionary origins of a modern polar marine fauna. Some 38 modern Southern Ocean molluscan genera (26 gastropods and 12 bivalves), representing approximately 18% of the total modern benthic molluscan fauna, can now be traced back through at least part of this sequence. As noted elsewhere in the world, the balance of the molluscan fauna changes sharply across the Cretaceous – Paleogene (K/Pg) boundary, with gastropods subsequently becoming more diverse than bivalves. A major reason for this is a significant radiation of the Neogastropoda, which today forms one of the most diverse clades in the sea. Buccinoidea is the dominant neogastropod superfamily in both the Paleocene Sobral Formation (SF) (56% of neogastropod genera) and Early - Middle Eocene La Meseta Formation (LMF) (47%), with the Conoidea (25%) being prominent for the first time in the latter. This radiation of Neogastropoda is linked to a significant pulse of global warming that reached at least 65°S, and terminates abruptly in the upper LMF in an extinction event that most likely heralds the onset of global cooling. It is also possible that the marked Early Paleogene expansion of neogastropods in Antarctica is in part due to a global increase in rates of origination following the K/Pg mass extinction event. The radiation of this and other clades at ~65°S indicates that Antarctica was not necessarily an evolutionary refugium, or sink, in the Early – Middle Eocene. Evolutionary source – sink dynamics may have been significantly different between the Paleogene greenhouse and Neogene icehouse worlds

"Business as usual": Drilling predation across the K-Pg mass extinction event in Antarctica

A survey of 759 predatory drill holes in Late Cretaceous and Paleogene molluscan and serpulid worm prey from Seymour Island (Antarctica) has allowed exploration of the effects of the K-Pg mass extinction on predator-prey dynamics at this high latitude site. Circular holes (0.62 - 6.41 mm in diameter), suggesting a large gastropod predator, most probably “Vanikoropsis” arktowskiana, occur throughout the study interval. Analysis suggests that the driller was a catholic predator capable of attacking a range of prey types, showing some degree of size and stereotypic handling behaviour. Although there were changes in prey choice across the extinction event, these reflect changes in available prey, and in particular limited options immediately post extinction. There were no significant changes in failure rate (Prey Effectiveness) over the mass extinction. Our findings suggest that at this site, for this particular predator, aside from menu choice, predation dynamics post-extinction was ‘business as usual’

Antarctic geoconservation: a review of current systems and practices

The prohibition of commercial mineral resource extraction through the Antarctic Treaty System has removed one significant source of potential damage to Antarctica's geological and geomorphological values. However, given the on-going increase in Antarctic tourism and scientific footprint, some high-quality geological features may be vulnerable to human impact, such as damage due to the construction of logistical facilities, unregulated collection of geological specimens or oversampling for scientific purposes. The Protocol on Environmental Protection to the Antarctic Treaty puts in place a framework for the protection of Antarctica's environmental, scientific, historic, wilderness and aesthetic values. However, the Antarctic Protected Area system is still immature and further implementation of existing management tools may be required to protect the diverse range of vulnerabilities, qualities and spatial scales represented in the geology and geomorphology of the continent. At sites where high-quality mineralogical or palaeontological specimens exist in limited quantities, considerations of how best to prevent oversampling and manage access to remaining material may be supported by assessment of cumulative impacts. Examination of the level of Antarctic specimen loans from a selection of national geological collections suggested that existing publically accessible geological collections could be better utilized, which could reduce environmental impact and oversampling at vulnerable Antarctic sites

Antarctic geoconservation: a review of current systems and practices

The prohibition of commercial mineral resource extraction through the Antarctic Treaty System has removed one significant source of potential damage to Antarctica's geological and geomorphological values. However, given the on-going increase in Antarctic tourism and scientific footprint, some high-quality geological features may be vulnerable to human impact, such as damage due to the construction of logistical facilities, unregulated collection of geological specimens or oversampling for scientific purposes. The Protocol on Environmental Protection to the Antarctic Treaty puts in place a framework for the protection of Antarctica's environmental, scientific, historic, wilderness and aesthetic values. However, the Antarctic Protected Area system is still immature and further implementation of existing management tools may be required to protect the diverse range of vulnerabilities, qualities and spatial scales represented in the geology and geomorphology of the continent. At sites where high-quality mineralogical or palaeontological specimens exist in limited quantities, considerations of how best to prevent oversampling and manage access to remaining material may be supported by assessment of cumulative impacts. Examination of the level of Antarctic specimen loans from a selection of national geological collections suggested that existing publically accessible geological collections could be better utilized, which could reduce environmental impact and oversampling at vulnerable Antarctic sites

Seafloor depth of George VI Sound, Antarctic Peninsula, from inversion of aerogravity data

George VI Sound is a ~600 km long curvilinear channel on the west coast of the southern Antarctic Peninsula separating Alexander Island from Palmer Land. The Sound is a geologically complex region presently covered by the George VI Ice Shelf. Here we model the bathymetry using aerogravity data. Our model is constrained by water depths from seismic measurements. We present a crustal density model for the region, propose a relocation for a major fault in the Sound and reveal a dense body, ~200 km long, flanking the Palmer Land side. The southern half of the Sound consists of two distinct basins ~1100 m deep, separated by a ‐650 m deep ridge. This constricting ridge presents a potential barrier to ocean circulation beneath the ice shelf and may account for observed differences in temperature‐salinity (T‐S) profiles