Category Archives: News

Stop the Press!! – Making the Hag’s Face

Oisi, Y., Ota, K. G., Kuraku, S., Fujimoto, S. & Kuratani, S., 2013: Craniofacial development of hagfishes and the evolution of vertebrates.
–Nature: Vol. 493, #7431, pp. 175-0 [doi: 10.1038/nature11794]

http://dx.doi.org/10.1038/nature11794

Abstract:
Cyclostomes, the living jawless vertebrates including hagfishes and lampreys, represent the most basal lineage of vertebrates. Although the monophyly of cyclostomes has been supported by recent molecular analyses, the phenotypic traits of hagfishes, especially the lack of some vertebrate-defining features and the reported endodermal origin of the adenohypophysis, have been interpreted as hagfishes exhibiting a more ancestral state than those of all other vertebrates. Furthermore, the adult anatomy of hagfishes cannot be compared easily with that of lampreys. Here we describe the craniofacial development of a series of staged hagfish embryos, which shows that their adenohypophysis arises ectodermally, consistent with the molecular phylogenetic data. This finding also allowed us to identify a pan-cyclostome pattern, one not shared by jawed vertebrates. Comparative analyses indicated that many of the hagfish-specific traits can be explained by changes secondarily introduced into the hagfish lineage. We also propose a possibility that the pan-cyclostome pattern may reflect the ancestral programme for the craniofacial development of all living vertebrates.

–Mikko

Multis made it through, but most of the squamates scurried and slithered off…

New study looking at squamate (lizard and snake) extinction patterns across the K-Pg boundary. (It’s a really neat study, but they should have put ‘dinosaur’ in the title and it would have been a guaranteed Nature/Science hit!):

Longrich, N. R., Bhullar, B. A. S., & Gauthier, J. A. (2012). Mass extinction of lizards and snakes at the Cretaceous–Paleogene boundary. Proceedings of the National Academy of Sciences, 109(52), 21396-21401.

The Cretaceous–Paleogene (K-Pg) boundary is marked by a major mass extinction, yet this event is thought to have had little effect on the diversity of lizards and snakes (Squamata). A revision of fossil squamates from the Maastrichtian and Paleocene of North America shows that lizards and snakes suffered a devastating mass extinction coinciding with the Chicxulub asteroid impact. Species-level extinction was 83%, and the K-Pg event resulted in the elimination of many lizard groups and a dramatic decrease in morphological disparity. Survival was associated with small body size and perhaps large geographic range. The recovery was prolonged; diversity did not approach Cretaceous levels until 10 My after the extinction, and resulted in a dramatic change in faunal composition. The squamate fossil record shows that the end-Cretaceous mass extinction was far more severe than previously believed, and underscores the role played by mass extinctions in driving diversification.

Ian

Stop the Press!! – Ediacaran Life, on land!

Retallack, G. J., 2013: Ediacaran life on land.
–Nature: Vol. 493, #7430, pp. 89-92 [doi: 10.1038/nature11777]
http://dx.doi.org/10.1038/nature11777

Abstract:

Ediacaran (635–542 million years ago) fossils have been regarded as early animal ancestors of the Cambrian evolutionary explosion of marine invertebrate phyla, as giant marine protists and as lichenized fungi. Recent documentation of palaeosols in the Ediacara Member of the Rawnsley Quartzite of South Australia4 confirms past interpretations of lagoonal–aeolian deposition based on synsedimentary ferruginization and loessic texture. Further evidence for palaeosols comes from non-marine facies, dilation cracks, soil nodules, sand crystals, stable isotopic data and mass balance geochemistry. Here I show that the uppermost surfaces of the palaeosols have a variety of fossils in growth position, including Charniodiscus, Dickinsonia, Hallidaya, Parvancorina, Phyllozoon, Praecambridium, Rugoconites, Tribrachidium and ‘old-elephant skin’ (ichnogenus Rivularites). These fossils were preserved as ferruginous impressions, like plant fossils, and biological soil crusts of Phanerozoic eon sandy palaeosols. Sand crystals after gypsum and nodules of carbonate are shallow within the palaeosols, even after correcting for burial compaction. Periglacial involutions and modest geochemical differentiation of the palaeosols are evidence of a dry, cold temperate Ediacaran palaeoclimate in South Australia. This new interpretation of some Ediacaran fossils as large sessile organisms of cool, dry soils, is compatible with observations that Ediacaran fossils were similar in appearance and preservation to lichens and other microbial colonies of biological soil crusts, rather than marine animals, or protists.

Cheers!

–Mikko

Making sense of palaeoclimate sensitivity

Making sense of palaeoclimate sensitivity

A new approach for evaluating past climate sensitivity data has been developed by scientists to help improve comparison with estimates of long-term climate projections developed by the Intergovernmental Panel on Climate Change (IPCC).

http://www.bris.ac.uk/news/2012/8965.html

Paper can be found here:

http://www.nature.com/nature/journal/v491/n7426/full/nature11574.html

– Laura