Environmental change prior to the K–T boundary inferred from temporal variation in the morphology of cheilostome bryozoans

O’Dea, Aaron; Håkansson, Eckart; Taylor, Paul D.; Okamura, Beth

doi:10.1016/j.palaeo.2011.06.001

Cited by 20 publications

(12 citation statements)

References 84 publications

(111 reference statements)

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“…It is also possible that zooid sizes prior to the K–Pg event were smaller than ‘normal’. Pre-extinction dwarfing has previously been observed in other taxa [51], [52], and an observed shift to smaller bryozoan zooid size prior to the K–Pg boundary in Denmark was attributed to a change in temperature [18]. These results imply that ‘unfavourable’ environmental conditions affected zooid size leading up to the mass extinction, potentially ‘re-setting’ size trends prior to the K–Pg boundary rather than across the K–Pg boundary itself.…”

Section: Discussionsupporting

confidence: 54%

“…In the case of bryozoans, this post-extinction size decrease can be expected at both the colony- and the zooid-level. Decreases in zooid size and colony size have been observed in cheilostome bryozoans during the latest Maastrichtian in Denmark and are thought to represent unstable and unfavourable environmental conditions, with low planktonic productivity, prior to the K–Pg boundary [18]. The study here extends this analysis across the K–Pg boundary to establish whether size reduction continued into the early Danian.…”

Section: Introductionsupporting

confidence: 54%

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

2014

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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.

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Section: Discussionsupporting

confidence: 54%

Section: Introductionsupporting

confidence: 54%

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

2014

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“…O'Dea et al . () also concluded that environmental changes occurred prior to the boundary in a study of bryozoans from Nye Kløv, which may also be related to the local relative changes in sea level.…”

Section: Discussionmentioning

confidence: 95%

Crossing the boundary: an elasmobranch fauna from Stevns Klint, Denmark

Adolfssen

Ward

2013

Palaeontology

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The chondrichthyan faunas from the Danish Maastrichtian chalk and the K/T boundary clay, the Fiskeler, are described for the first time. The rich and diverse fauna discovered in the late Maastrichtian chalk experienced a massive drop in diversity prior to the boundary. However, the fauna started to recover immediately after the deposition of the impact layer during earliest Danian times and had regained much of its diversity during the first few millennia after the bolide impact. Precision sampling has made it possible to document the recovery of the fauna, which did not suffer an extinction event of the same magnitude, as apparently observed in Morocco. At Stevns Klint, only 33 per cent of the chondrichthyan fauna became extinct compared with the 96 per cent in Morocco. The drop in diversity before the boundary is attributed to a sudden change in sea level. Among the sharks found in the chalk and Fiskeler are rare species such as Parasquatina and Echinorhinus and the first representative of Nebrius in Europe.

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“…Of relevance to GW effects, several studies have shown that colony growth and zooid size are both affected by changes in temperature (Stebbing, ; Menon, ; Winston, ; Pätzold et al ., ; Okamura & Bishop, ; Hunter & Hughes, ; Barnes, ; O'Dea & Okamura, 1999, 2000 a , b ; O'Dea & Jackson, ; O'Dea, ; Taylor, ; Amui‐Vedel, Hayward & Porter, ; O'Dea, Rodríguez & Romero, ; Knowles et al ., ; O'Dea et al ., ). Calcification rate, skeletal carbonate mineralogy and geochemistry may also co‐vary with temperature (Smith & Key, ; Bader & Schäfer, ; Barnes, Webb & Linse, , ; Lombardi et al ., , ; Smith, ; Schäfer & Bader, ; Kuklinski & Taylor, ; Knowles et al ., ; Loxton et al ., ; Fortunato, Schäfer & Blaschek, ).…”

Section: The Futurementioning

confidence: 97%

Biomineralization in bryozoans: present, past and future

2014

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Many animal phyla have the physiological ability to produce biomineralized skeletons with functional roles that have been shaped by natural selection for more than 500 million years. Among these are bryozoans, a moderately diverse phylum of aquatic invertebrates with a rich fossil record and importance today as bioconstructors in some shallow-water marine habitats. Biomineralizational patterns and, especially, processes are poorly understood in bryozoans but are conventionally believed to be similar to those of the related lophotrochozoan phyla Brachiopoda and Mollusca. However, bryozoan skeletons are more intricate than those of these two phyla. Calcareous skeletons have been acquired independently in two bryozoan clades - Stenolaemata in the Ordovician and Cheilostomata in the Jurassic - providing an evolutionary replicate. This review aims to highlight the importance of biomineralization in bryozoans and focuses on their skeletal ultrastructures, mineralogy and chemistry, the roles of organic components, the evolutionary history of bimineralization in bryozoans with respect to changes in seawater chemistry, and the impact of contemporary global changes, especially ocean acidification, on bryozoan skeletons. Bryozoan skeletons are constructed from three different wall types (exterior, interior and compound) differing in the presence/absence and location of organic cuticular layers. Skeletal ultrastructures can be classified into wall-parallel (i.e. laminated) and wall-perpendicular (i.e. prismatic) fabrics, the latter apparently found in only one of the two biomineralizing clades (Cheilostomata), which is also the only clade to biomineralize aragonite. A plethora of ultrastructural fabrics can be recognized and most occur in combination with other fabrics to constitute a fabric suite. The proportion of aragonitic and bimineralic bryozoans, as well as the Mg content of bryozoan skeletons, show a latitudinal increase into the warmer waters of the tropics. Responses of bryozoan mineralogy and skeletal thickness to oscillations between calcite and aragonite seas through geological time are equivocal. Field and laboratory studies of living bryozoans have shown that predicted future changes in pH (ocean acidification) combined with global warming are likely to have detrimental effects on calcification, growth rate and production of polymorphic zooids for defence and reproduction, although some species exhibit reasonable levels of resilience. Some key questions about bryozoan biomineralization that need to be addressed are identified.

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Environmental change prior to the K–T boundary inferred from temporal variation in the morphology of cheilostome bryozoans

Cited by 20 publications

References 84 publications

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

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

Crossing the boundary: an elasmobranch fauna from Stevns Klint, Denmark

Biomineralization in bryozoans: present, past and future

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