"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’

Evolution and extinction of Maastrichtian (Late Cretaceous) cephalopods from the López de Bertodano Formation, Seymour Island, Antarctica

One of the most expanded records to contain the final fortunes of ammonoid cephalopods is within the López de Bertodano Formation of Seymour Island, James Ross Basin, Antarctica. Located at 65° South now, and during the Cretaceous, this sequence is the highest southern latitude onshore outcrop containing the Cretaceous-Paleogene (K-Pg) transition. We present comprehensive new biostratigraphic range data for 14 ammonite and one nautiloid species based on the collection of >. 700 macrofossils from high-resolution sampling of parallel sedimentary sections, dated Maastrichtian to earliest Danian in age, across southern Seymour Island. We find evidence for only a single, abrupt pulse of cephalopod extinction at the end of the Cretaceous when the final seven ammonite species disappeared, consistent with most evidence globally. In the lead up to the K-Pg extinction in the James Ross Basin, starting during the Campanian, ammonite diversity decreased overall, but the number of endemic taxa belonging to the family Kossmaticeratidae actually increased. This pattern continued into the Maastrichtian and may be facies controlled, linked to changes in sea level and seawater temperature. During the early Maastrichtian, ammonite diversity dropped significantly with only two species recorded from the basal López de Bertodano Formation on Seymour Island. The subsequent diversification of endemic taxa and reappearance of long-ranging, widespread species into the basin resulted in an increase in ammonite diversity and abundance during the mid-Maastrichtian. This was coincident with an apparent period of warming temperatures and sea level rise interpreted from palynology and sedimentology, perhaps reflecting a high latitude expression of the Mid-Maastrichtian Event. Late Maastrichtian diversity levels remained stable despite reported climatic and environmental variation. Ammonite diversity patterns during the Maastrichtian parallel those of microfossil species such as nannofossil and planktonic foraminifera, suggesting that dynamic climatic and environmental changes affected many planktonic and nektonic organisms during the latest Cretaceous. However, we suggest that these perturbations had a minimal effect on overall diversity prior to the catastrophic extinction event at the K-Pg boundary

Body size trends and recovery amongst bivalves following the end-Triassic mass extinction

Fossils in the immediate aftermath of mass extinctions are often of small size, a phenomenon attributed to the Lilliput Effect (temporary, size reduction of surviving species). There has been little attempt to study size trends during subsequent recovery intervals nor has the relationship between size, diversity and environmental controls been evaluated. Here we examine the recovery following the end-Triassic mass extinction amongst bivalves of the British Lower and Middle Lias. Three distinct phases of size change are seen that are independent of other recovery metrics: initially bivalves are small but the Lilliput Effect is a minor factor, the majority of small taxa belong to new species that undergo a later within-species size increase (the Brobdingnag Effect) throughout the subsequent Hettangian Stage. New species that appeared during the Hettangian were also progressively larger and Cope's Rule (size increase between successive species) is seen – notably amongst ammonites. The size increase was reversed during the Sinemurian Stage, when bivalves once again exhibited small body sizes. During the Pliensbachian Stage another phase of size increase occurred with further evidence of the Brobdingnag Effect. These three phases of size change are seen across all suspension feeding ecological guilds of bivalve but are not expressed among deposit feeders. Local environmental conditions explain some aspects of size patterns, but factors such as temperature, marine oxygenation and sea level, do not correlate with the long-term size trends. The Brobdingnag Effect may reflect increased availability/quality of food during the recovery interval: a factor that controlled bivalve size but not evolution

Hard substrate communities across the K–Pg boundary

This thesis compares the ecologies of hard substrate communities across the K–Pg boundary. As suspension feeders, hard substrate fauna are expected to be particularly susceptible to the hypothesised photosynthesis crash at this time. Encrusting organisms from K–Pg sections in the SE USA, Denmark, the Netherlands and the Antarctic are utilised, in order to examine trends across the mass extinction in different regions

The Lilliput Effect in Colonial Organisms: Cheilostome Bryozoans at the Cretaceous–Paleogene Mass Extinction

Consistent trends towards decreasing body size in the aftermath of mass extinctions – Lilliput effects – imply a predictable response among unitary animals to these events. The occurrence of Lilliput effects has yet to be widely tested in colonial organisms, which are of particular interest as size change may potentially occur at the two hierarchical levels of the colony and the individual zooids. Bryozoans are particularly useful organisms in which to study colonial size response as they have well-defined zooids. Additionally, a number of analyses of present-day bryozoans have shown that zooid size reflects local environmental conditions, most notably seawater temperature and possibly also food supply. Following the hypothesised decline in primary productivity at the Cretaceous–Paleogene (K–Pg) mass extinction, it is predicted that bryozoan zooid size should decline in the early Paleogene, resulting in a Lilliput effect. To test this prediction, zooid size was compared across the K–Pg boundary at the assemblage level and also within 4 surviving genera. Analysis of 59 bryozoan species from assemblages on either side of the K–Pg boundary showed no significant change in zooid length. Zooid size was also measured in 98 Maastrichtian colonies and 162 Danian colonies belonging to four congeneric species. Only one of these genera showed a significant size decrease across the K–Pg boundary, the other three maintaining constant zooidal lengths, widths and areas. Additionally, the sizes of 210 Maastrichtian colonies and 163 Danian colonies did not show consistent size decrease across the K–Pg boundary in these same species, although maximum colony size did decline in three out of four genera. Furthermore, this lack of consistent size change is uniform between two distinct biogeographical regions, Denmark and the southeastern USA

"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’

Biogeographical and ecological patterns in bryozoans across the K-Pg boundary: implications for the phytoplankton collapse

The hypothesized collapse in primary productivity associated with the Cretaceous-Paleogene (K-Pg) mass extinction would have been particularly severe on suspension feeders dependent on phytoplankton. Previous research on the ecological dynamics of erect bryozoans in the Danish Basin supported the phytoplankton crash hypothesis in showing a major postextinction increase in the skeletal biomass of cyclostome bryozoans relative to the more nutrient-demanding cheilostome bryozoans. New data on the ecological dynamics between these two bryozoan clades across the K-Pg boundary are provided to determine whether the postextinction cyclostome spike is also evident in encrusting bryozoans and over a greater geographical area. Changes across the K-Pg were quantified in encrusting bryozoans using three metrics: (1) abundance of colonies; (2) area of substrate covered; and (3) colony form. Data from the southeastern United States were added to those from Denmark to control for regional factors. Our analyses indicate a globally uniform change among encrusting bryozoans but without the strong postextinction cyclostome spike seen previously in Danish erect bryozoans. An increased proportion of sheet over runner cyclostome colonies was found in the lower Danian of Denmark and the southeastern United States, despite the expectation that runners with widely dispersed zooids should fare better in low nutrient conditions. Furthermore, weighed samples of erect bryozoans from the basal Danian of Maastricht (Netherlands) and the southeastern United States failed to reveal a strong cyclostome spike. These findings question the phytoplankton crash hypothesis, or at least the extent to which this kill mechanism influenced suspension feeders during the K-Pg mass extinction

‘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’

The Lilliput Effect in Colonial Organisms: Cheilostome Bryozoans at the Cretaceous–Paleogene Mass Extinction

<div><p>Consistent trends towards decreasing body size in the aftermath of mass extinctions – Lilliput effects – imply a predictable response among unitary animals to these events. The occurrence of Lilliput effects has yet to be widely tested in colonial organisms, which are of particular interest as size change may potentially occur at the two hierarchical levels of the colony and the individual zooids. Bryozoans are particularly useful organisms in which to study colonial size response as they have well-defined zooids. Additionally, a number of analyses of present-day bryozoans have shown that zooid size reflects local environmental conditions, most notably seawater temperature and possibly also food supply. Following the hypothesised decline in primary productivity at the Cretaceous–Paleogene (K–Pg) mass extinction, it is predicted that bryozoan zooid size should decline in the early Paleogene, resulting in a Lilliput effect. To test this prediction, zooid size was compared across the K–Pg boundary at the assemblage level and also within 4 surviving genera. Analysis of 59 bryozoan species from assemblages on either side of the K–Pg boundary showed no significant change in zooid length. Zooid size was also measured in 98 Maastrichtian colonies and 162 Danian colonies belonging to four congeneric species. Only one of these genera showed a significant size decrease across the K–Pg boundary, the other three maintaining constant zooidal lengths, widths and areas. Additionally, the sizes of 210 Maastrichtian colonies and 163 Danian colonies did not show consistent size decrease across the K–Pg boundary in these same species, although maximum colony size did decline in three out of four genera. Furthermore, this lack of consistent size change is uniform between two distinct biogeographical regions, Denmark and the southeastern USA.</p></div

Nested ANOVA results for zooid area.

<p>*  = <i>p</i><0.05; **  = <i>p</i><0.01; ***  = <i>p</i><0.001.</p>a<p>Negative estimates of variance components associated with non-significant F-ratios were assigned zero values in keeping with standard practice <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0087048#pone.0087048-Taylor1" target="_blank">[26]</a>.</p>b<p>Denominator of the F-test is zero.</p