Triassic news February 2014: Origin of vivipary in marine reptiles

Vivipary, the development of an embryo inside the mother’s uterus and eventually leading to live birth, has for marine reptiles traditionally been considered to have developed in the aquatic environment. However, a new open access paper published February 12th 2014 in PLOS One by Motani et al. 2014: “Terrestrial Origin of Viviparity in Mesozoic Marine Reptiles Indicated by Early Triassic Embryonic Fossils” provides evidence that the oldest known marine reptiles belonging to the genus Chaohusaurus (Reptilia, Ichthyopterygia) gave birth to their young through head-first birth posture, in contrast to younger (and more derived) ichtyosaurs who gave birth tail-first, just like modern whales.

Chaohusaurus, the oldest known genus of the Ichtyopterygia, inhabited the oceans during the Early Triassic, som 248 million years ago. Motani et al. 2014 found 80 new fossil skeletons of Chaohusaurus in a quarry in China. One of the specimens shows the partial skeleton of a female Chaohusaurus with three embryos, of which one is in birth position. The beautiful and exceptional fossil is pictured below, but I highly recommend reading the original paper and viewing its high resolution figures!

Figure 2. The maternal specimen with three embryos. Color coding indicates: black, maternal vertebral column, including neural and haemal spines; blue, maternal pelvis and hind flipper; green, maternal ribs and gastralia. Embryos 1 and 2 are in orange and yellow, respectively, whereas neonate 1 is in red. Scale bar is 1 cm. Abbreviations: i-v, metatarsals; 4, fourth distal tarsal; a, astragalus; c, calcaneum; cr, caudal rib; cv, caudal vertebra; d, dentary; fe, femur; fi, fibula; h, haemal spine; il, ilium; is, ischium; pb, pubis; pm, premaxilla; sr, sacral rib; sv, sacral vertebra; and ti, tibia. See fig. S2 for a high resolution image. doi:10.1371/journal.pone.0088640.g002

Figure 2 in Motani et al. 2014. The maternal specimen with three embryos.
Color coding indicates: black, maternal vertebral column, including neural and haemal spines; blue, maternal pelvis and hind flipper; green, maternal ribs and gastralia. Embryos 1 and 2 are in orange and yellow, respectively, whereas neonate 1 is in red. Scale bar is 1 cm. Abbreviations: i-v, metatarsals; 4, fourth distal tarsal; a, astragalus; c, calcaneum; cr, caudal rib; cv, caudal vertebra; d, dentary; fe, femur; fi, fibula; h, haemal spine; il, ilium; is, ischium; pb, pubis; pm, premaxilla; sr, sacral rib; sv, sacral vertebra; and ti, tibia. doi:10.1371/journal.pone.0088640.g002

The authors argue that because one of the Chaohusaurus-babies (1) lies outside the maternal body in the present specimen, this suggests that the mother had already given birth to at least one offspring before it died. They conclude that the mother likely died in labor, and because the rock containing the fossil is marine, birth most likely occurred underwater. Because the skull orientation of the embryos is head-first this suggests that viviparity in Ichthyopterygia most likely evolved in an ancestor on land, where head-first position during birth is the norm.

The authors conclude that both marine reptiles belonging to Ichthyopterygia and also Sauropterygia most likely evolved from viviparous land ancestors in the Early Triassic, at least as early as 248 million years ago. Therefore, viviparity may have already been common among terrestrial reptiles during the recovery phase from the end-Permian mass extinction.



Report from the GSA-meeting in Denver, and the session on the TJ-boundary and end-Triassic mass extinction

Last week I attended the Geological Society of America (GSA) annual meeting and 125th anniversary which was held at the Colorado Convention Center in Denver, Colorado, USA – A multitude of scientific sessions and thousands of geoscientists! As always with large conferences, it is both fantastic and confusing to have so many interesting sessions presented almost simultaneously.

The Colorado Convention Center in Denver with its Blue Bear and the Rockies in the background (view from my hotel window at the Regency Hyatt; Photo: S. Lindström).

The Colorado Convention Center in Denver with its Blue Bear and the Rockies in the background (view from my hotel window at the Regency Hyatt; Photo: S. Lindström).

I participated in the session T238. New insights into Triassic-Jurassic Transition events and end-Triassic Mass Extinction (blue text are links to program and abstracts). This session was graciously hosted by Rowan C. Martindale and Morgan F. Schaller who had put together an interesting programme bringing forth some of the latest research and ideas concerning TJ-boundary research. We who participated got to hear interesting talks on the carbon cycle, specifically on Late Triassic pCO2 variations by Morgan Schaller et al. and on Late Triassic ocean stability and orbital control by Sylvain Richoz et al.  The pedogenic carbonate results of Schaller et al.’s research suggest a long-time (30-million-years) fall in the atmospheric CO2-content from the Carnian to the late Rhaetian prior to the eruption of the Central Atlantic Magmatic Province (CAMP). Richoz et al., on the otherhand, demonstrate a relatively stable marine C-isotope curve from the Norian to the Rhaetian, displaying only a gentle decrease, i.e. possibly an on-going input of light carbon to the atmosphere (increased CO2) during the Late Triassic prior to CAMP eruption. 

Regarding the plant record, Wolfram Kürschner presented some new data indicating environmental mutagenesis in Late Triassic conifers in more equatorial areas, where a sudden size increase in Classopollis pollen may be due to whole genome doubling (polyploidy) as a consequence of environmental stress.  Karen Bacon talked about the fact that many present-day plants get thicker leaves when subjected to increased levels of CO2, and especially if exposed to low O2 at the same time, and put this in relation to findings in the plant records across the TJ-boundary in East Greenland. In one of the solicited talks, Jennifer McElwain presented an extensive review of her and her co-workers palaeobotanical research on the TJ-boundary of East Greenland over the last 25 years. The impact of her research did however, receive some criticism from the next solicited speaker Spencer Lucas who meant that not only is there no palaeobotanical evidence for a global or even regional mass extinction at the end of the Triassic, but not for the terrestrial terapods either! But then Lucas did not seem to acknowledge the palynological support for a floral mass extinction. His critique does emphasize that there is a need of more thorough palaeobotanical work across the TJ-boundary from other parts of the world.

Lucas also presented major criticism on the impact of the cyclostratigraphic scheme for the Newark Basin, which he said had caused “a decade-long miscorrelation” with other TJ-boundary succession. This led to a slightly heated discussion between Lucas and the next speaker, Paul Olsen, one of the researchers behind the Newark Basin cyclostratigraphy. In his talk, Paul Olsen discussed the impact a volcanic winter due to SO2-degassing from the CAMP would have on terrestrial vertebrates. 

After a short break it was finally my turn. My talk, entitled “Supraregional seismites in Triassic – Jurassic boundary strata“, presented widespread evidence of episodic seismic activity in NW Europe during the end-Triassic mass extinction interval. My co-authors and I have found evidence of at least four separate seismic events in the form of soft-sediment deformations within TJ-boundary successions from Sweden, Denmark and Germany, and the implications of these on the CAMP and the end-Triassic mass extinction where discussed during the talk, which was going as scheduled when it was interrupted by a ca 5 minute long false fire alarm. Eventually I could continue and finish my talk but unfortunately with no time for questions.

One of the most interesting talks was that on the Cotham Marble where Yadira Ibarra et al. showed that the calcified microbial mats, containing prasinophycean algal cysts (Tasmanites) and a sparse shelly fauna, must have formed in a calcium carbonate supersaturated environment. The Cotham Marble is synchronous to the so called initial C-isotope excursion. Kathleen Rittersbuch et al. presented new data on earliest Jurassic siliceous sponge dominance based on fieldwork in the Peruvian Andes. Correlations with siliceous sponge records in Nevada, the Austrian Alps and Morocco indicate that this was a globally relevant phenomena.

Aviv Bachan and Jonathan Payne presented modeling of hypothesized carbon cycle perturbation scenarios for the TJ-boundary, focusing on the large positive C-isotope excursion (CIE) following the sharp negative CIE. They found that the modelled scenario most similar to the recorded C-isotope record is that with temporary increase in pCO2 coincident with the volatile release, as well as a temporary decrease in carbonate saturation, indicating that the release of volatiles during the emplacement of the Central Atlantic Magmatic Province could have been the driver of the environmental perturbation.

The final talk of the session was that of Bas van de Schootbrugge et al. who presented our palynological reworking data that indicate increased weathering and erosion, i.e. mass-wasting, synchronous to the terrestrial deforestation during the end-Triassic mass extinction. The massive reworking registered in both Germany, Denmark and Sweden, emphasizes the severity of the environmental impact on the land environment, and it seems likely that increased input of sediment, soil and organic matter to the ocean must have played a part in the extinction scenario.

We celebrated the end of an interesting the session by having lunch at the Rock-Bottom Restaurant in downtown Denver. Good food and great company! :-)

Updates on our TJ-boundary project

The Triassica site has been silent because I have been on vacation and on a great five week fieldwork to North Greenland – which was great except for the fact that I missed out on the apparently best Swedish summer in years, and now autumn is on its way…

Scenery from North Greenland summer 2013 (Photo by Sofie lindström)

Scenery from North Greenland summer 2013 (Photo by Sofie Lindström)

Here are some news from our Geocenter Denmark financed Triassic-Jurassic (TJ) boundary project:

We have published a new paper on the Rhaetian coals of southern Sweden, which amongst all the interesting data also includes a beautiful artistic reconstruction of a Rhaetian forest mire: 

Petersen, H.I, Lindström, S., Therkelsen, J., Pedersen, G.K. 2013. Deposition, floral composition and sequence stratigraphy of the uppermost Triassic (Rhaetian) coastal coals, southern Sweden. International Journal of Coal Geology 116-117, 117-134.

We are now also advertising for a PhD-student for our TJ-boundary project, a collaboration between three institutes within Geocenter Denmark: the Geological Survey of Denmark and Greenland (GEUS), the  the Department of Geosciences and Natural Resource Management (DGN) at Copenhagen University, and the Department of Geosciences at Århus University. The PhD-position is placed at the Department of Geosciences and Natural Resource Management (DGN), and the successful candidate will perform research on high-resolution chemo- and cyclostratigraphic analysis with the goal of deciphering local to global changes of environmental redox and carbon cycle perturbations through the end Triassic (Rhaetian) early Jurassic (Pliensbachian), and assessing the pacing of the ecosystem pertubation. You can read the full description here.

We are looking forward to receiving applications from potential candidates :-)

Hot topics within Earth and Planetary sciences 2012

Every third month Science direct lists the twentyfive hottest articles within a specific field of research. The present Hot topics list is based on number of downloads for each article during the full year of 2012.  However, the list is still a good indicator if one wants to find out what’s hot in geosciences.

Based on the Science Direct list for 2012, I have compiled the three hottest topics within Earth and Planetary sciences, and these are:

  1. Fresh water treatment/resources 6/25
  2. Ecology/Palaeoecology/Evolution 5/25
  3. Climate change/ocean acidification 5/25

Compared to the last published list the research focus of 2012 based on the most downloaded papers from Science Direct have changed somewhat. The most downloaded papers are now within Fresh water treatment/resources and three of these papers deal with reverse osmosis desalination. Reverse osmosis is one of the main technologies for producing fresh water from saline water and other wastewater sources. Fresh water shortage has become an important issue affecting the economic and social development in many countries, but there are still many challenges with reverse osmosis, as discussed by Kang & Kao (2012) and Pérez-Gonzaléz et al. (2012).

Papers on Ecology/Palaeoecology/Evolution and Climate change/ocean acidification have also attracted a lot of attention of the research community during 2012. The two subjects are tightly linked as exemplified by one of the most downloaded papers (nr 10 of 25), a review paper by Leslie Hughes from 2000: Biological consequences of global warming: is the signal already apparent?

Interestingly, the top downloaded paper within Earth and Planetary Sciences 2012 is a paper demonstrating the potential of microbial U(VI) reduction as an alternative technology to currently used physical/chemical processes for treatment and recovery of uranium in the nuclear industry (Chabalala & Chirwa, 2010). Perhaps this signals an increasing global need to find new methods in order to retreive natural resources that were previously considered to costly and technologically challenging?

To me, the 2012 hottest topics list signals increasing awareness within the research community that climatic and environmental changes, pollution and exploitation of natural resources presents new challenges in a world with increasing population pressure and demand of economic development!

Open letter to the President and to the Vice-President of the European Geosciences Union

Sofie L.:

Gender equality within the European Geosciences Union? Apparently not…

Originally posted on Barbara Wohlfarth:

Vienna, April 9, 2013

Dear colleagues,

It has been a few years since I last attended the EGU General Assembly, which has always been an excellent forum for me to catch up on latest research results, to learn more about new research directions, and of course to meet colleagues. This year I am attending the EGU General Assembly again, mainly because the Earth Science Women’s Network had invited me to give a lecture.
Having lived in Sweden for the past 20 years, gender and gender biases are no longer very big issues, because we employ (at least at universities and in research) the principle of an even gender balance at all levels. 15 to 20 years ago, when fewer women had high academic positions, it was sometimes a bit difficult to find enough qualified women to fill the 50%, but given the focus on and awareness of the problem, concerted…

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A new three-year project on the Triassic-Jurassic boundary :-)

Me and my colleagues at the Geological Survey of Denmark and Greenland (GEUS), the Department og Geography and Geology (IGN) at Copenhagen University, and the Department of Earth Sciences (IG) at Århus University, have received a large strategic research grant from Geocenter Denmark to continue our research on the Triassic-Jurassic boundary. This three-year project will focus on the Danish Basin, where we are fortunate enough to have preserved not only a thick marginal marine to fully marine TJ-boundary succession in the subsurface of southern Sweden and Denmark,  but also marginal marine to terrestrial strata outcropping in Scania (S Sweden) and on the Danish island Bornholm.


Wintery scenery from our latest fieldwork session in March 2013 (Photo: G.K. Pedersen).

The new project is partly a continuation of our three-year (2010-2013) starting grant from Geocenter Denmark which also dealt with the TJ-boundary of the Danish Basin, the results of which were published in Lindström et al. 2012 in Geology and Petersen and Lindström 2012 in PlosOne, and participated to Richoz et al. 2012 in Nature Geoscience.

By joining forces, our team now incorporates sedimentology, palynology, micropalaeontology, isotope geochemistry, inorganic and organic geochemistry, organic petrography, magmatic petrography and diagenesis.

We are delighted to be able to continue our research on the TJ-boundary and the events leading up to, and succeeding the end-Triassic mass extinction.

Closing in on Jurassic Park

Several years ago, while I was still working at Lund University, one of my colleagues Dr Johan Lindgren came to me one day with a microscope slide and asked me if I could help him check if there was anything in it. The only things we found were very small (ca 10-15 μm) spiny oval things, definitely not something palynological but most likely something organic of some sort.

Johan Lindgren showed me a paper by Mary Schweizer et al. (2007) which depicted small spiny cells from soft-tissue preserved inside bones from three different dinosaurs Tyrannosaurus rex, Triceratops horridus and Brachylophosaurus canadensis.

These cells were believed to be osteocytes, small star-shaped cells that reside inside bones and which can live as long as the organism itself and are capable of bone deposition and resorption.

The small spiny oval things that Johan Lindgren had in his slide definitely looked similar, although they did not come from a dinosaur but from a 70 million year old Mosasaur.  Because this bone came from a marine reptile, a creature that had lived and died in the ocean, Johan Lindgren was determined to rule out that contamination from sea-sediment or other organisms was the source of the small spiny cells, and after years of research he finally published his results in the highly acclaimed open-access journal PLos One: Lindgren et al. 2011: Microscopic evidence of Cretaceous Bone Proteins. The photographic plate below from the Lindgren et al. (2011) paper shows the tiny spiny osteocytes still looking amazing after 70 million years!! :-)

Fig. 1. from the Lindgren et al. (2011) paper showing the spiny osteocytes in photos A-F.

Fig. 1. from the Lindgren et al. (2011) paper showing the spiny osteocytes in photos A-F.

Research performed on soft-tissue preserved in fossil bones are bringing us closer to the plot of Stephen Spielberg’s 1993 motion picture “Jurassic Park”, after a novel by Michael Crichton. Mary Schweitzer and her colleagues have just published a new paper in the journal Bone: Schweitzer et al. (2013): Molecular analyses of dinosaur osteocytes support the presence of endogenous molecules, in which their data are the first to support preservation of multiple proteins and to present multiple lines of evidence for material consistent with DNA in dinosaurs.

You can read more about this study on: ScienceDaily

However, there is still a long way to go before anyone can genetically modify frog-DNA and recreate Tyrannosaurus rex or any other dinosaurs like they did in “Jurassic Park”.

Jurassic Park logo, borrowed from the official website:
Check it out!