Archive

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.

• Read more about Crossing the boundary: an elasmobranch fauna from Stevns Klint, Denmark

Based on the quantitative community analysis using species-level identifications, we track the restoration of benthic ecosystems after the end-Permian mass extinction throughout the Lower Triassic of the western USA. New data on the palaeoecology of the Thaynes Group and Sinbad Formation are provided, which fill a gap between the recently studied palaeoecology of the Griesbachian–Dienerian Dinwoody Formation and the Spathian Virgin Formation.

• Read more about Recovery of benthic marine communities from the end-Permian mass extinction at the low latitudes of eastern Panthalassa

Community evenness has recently received much attention, either because it is related to ecosystem functioning or because it may affect estimation of diversity. Temporal and environmental trends in diversity and evenness of trilobite communities during the Late Cambrian – Early Ordovician of the Cordillera Oriental (north-western Argentina) are here analysed. Richness and evenness increase through time in both deep subtidal (between fair-weather and storm wave base) and offshore (below storm wave base) communities.

• Read more about Evenness and diversity in Upper Cambrian – Lower Ordovician trilobite communities from the Central Andean Basin (Cordillera Oriental, Argentina)

In the largest early tetrapod clade, the temnospondyls, ontogenies were diverse and quite distinct from the life cycles of extant amphibians. Three well-studied clades exemplify the diversity of these long-extinct ontogenies, here analysed with respect to their bearing on developmental plasticity, reaction norms and evolution. Sclerocephalus readily adjusted by means of developmental evolution to different lake environments. In addition, plasticity (reaction norm) played a significant role, apparent both morphologically and by altered developmental traits.

• Read more about Life cycles, plasticity and palaeoecology in temnospondyl amphibians

Placoderms, representing phylogenetically more inclusive jawed vertebrates and successive sister taxa to crown-group gnathostomes, are critical to our understanding of character evolution within the crown-group (chondrichthyans + osteichthyans), including developmental characters. Early ontogenetic stages of placoderms are generally poorly known, although some exceptional faunas preserve both embryonic (e.g. from the Gogo Formation, Western Australia) and post-embryonic individuals (the Miguasha Formation, Canada; Lode Formation, Latvia; Merriganowry Formation, Gogo Formation, Australia).

• Read more about Fossilized ontogenies: the contribution of placoderm ontogeny to our understanding of the evolution of early gnathostomes

The shell of marine gastropods conserves and reflects early ontogeny, including embryonic and larval stages, to a high degree when compared with other marine invertebrates. Planktotrophic larval development is indicated by a small embryonic shell (size is also related to systematic placement) with little yolk followed by a multiwhorled shell formed by a free-swimming veliger larva. Basal gastropod clades (e.g. Vetigastropoda) lack planktotrophic larval development.

• Read more about Larval ecology and morphology in fossil gastropods

Research this century has greatly improved our knowledge of the origin and early radiation of dinosaurs. The unearthing of several new dinosaurs and close outgroups from Triassic rocks from various parts of the world, coupled with improved phylogenetic analyses, has set a basic framework in terms of timing of events and macroevolutionary patterns.

• Read more about The origins of Dinosauria: much ado about nothing

Phylogenomics reconstructs an arthropod tree in which a monophyletic Arthropoda splits into Pycnogonida + Euchelicerata and Myriapoda + Pancrustacea. The same chelicerate–mandibulate groups are retrieved with morphological data sets, including those encompassing most taxa known from Palaeozoic Konservat-Lagerstätten.

• Read more about Origins and early evolution of arthropods

The new ichnospecies Celliforma curvata is described to include curved fossil bee cells from Argentina, Uruguay and the USA. The upper part of the cell (neck) of the new ichnospecies is curved, and accordingly, it can be attributed to bees of the subfamily Diphaglossinae (Colletidae). The oldest record of C. curvata, from the early Eocene of North America (52–49 Ma), provides a minimum age for the appearance of this subfamily, in accordance with an already proposed calibrated phylogeny.

• Read more about Curved fossil bee cells as tools for reconstructing the evolutionary history and palaeogeographical distribution of Diphaglossinae (Apoidea, Colletidae)

The tommotiid Paterimitra pyramidalis Laurie, 1986, is redescribed based on well-preserved material from the lower Cambrian Wilkawillina, Wirrapowie and Ajax limestones of the Flinders Ranges, South Australia. The material shows that the scleritome of Paterimitra pyramidalis includes three sclerite morphotypes (S1, S2 and L).

• Read more about Paterimitra pyramidalis from South Australia: scleritome, shell structure and evolution of a lower Cambrian stem group brachiopod