Synchotron Radiation Tomography Illuminates Hidden Bugs

http://news.bbc.co.uk/2/hi/science/nature/7324564.stm

We've all seen pictures of ancient insects trapped in the golden, honey-like transparency of amber. Amber is fossilized tree resin, that when it was formed, trapped and preserved the form of insects and other small animals that it flowed over. But much amber is cloudy, and short of breaking it open, there's not been anyway to look inside to see what fossils might be found within. Now, scientists at the European Synchotron Radiation Facility in Grenoble, France have used high-intensity X-ray radiation to peek inside the amber and through computerized tomography (the same method as CT scans used in medicine) reconstructed 3-D images of fossils found in the amber. This was previously not possible with conventional X-ray sources. What's even neater - they use a method called 3D printing to produce a plastic resin scaled up model of the fossils in the amber, so palaeontologists have something tangible to manipulate and observe, rather than just pictures on a screen. Really amazing!

Horseshoe crabs now date back to 445 MYA

"A remarkable new fossil horseshoe crab, Lunataspis aurora gen. et sp. nov., from recently discovered Upper Ordovician (c. 445 Ma) shallow marine Konservat-Lagerstätten deposits in Manitoba (Canada)."

See Rudkin, DM, GA Young & GS Nowlan, 2008. The oldest horseshoe crab: a new Xiphosurid from late Ordovician Konservat-Lagerstätten deposits in Manitoba, Canada. Palaeontology, 51(1): 1-9. and "Oldest Horseshoe Crab Fossil Discovered," by Jeanna Bryner. LiveScience.com, 28 Jan 2008.

This pushes back evidence for the mysterious horseshoe crabs by almost 100 million years, from 350 million to 445 million years ago. Having survived multiple extinction events during its geological existence, but habitat loss and marine pollution have seen significant localised loss of population numbers in some countries.

Present day horseshoe crabs appear to be similar to such fossils and we refer to them as "living fossils". In Singapore, Mandai mangroves appear to be a significant refuge for them. Let's hope we can extend their impressive record a little longer.

Giant fungus

The Devonian fossil Prototaxites, long a puzzle thought to be a vascular tree species, may actually be a fungus.... C. Kevin Boyce of the University of Chicago and co-workers used isotopic ratios to show that it was more likely to be a heterotroph than an autotroph, and based on its anatomy it was most likely to have been a fungus.

Journal reference: Geology, May 2007; v. 35; no. 5; p. 399–402; doi: 10.1130/G23384A.1

Giant Sea Scorpion!

We usually think of invertebrates as small animals, and arthropods in particular as being limited by the structural engineering of an exoskeleton, which is less capable of supporting large body sizes than an endoskeleton. A new fossil discovery however should creep out anyone who thinks that crabs and lobsters are already bigger than a decent invertebrate should be.

From a 43 cm long claw of the fossil eurypterid (sea scorpion) species Jaekelopterus rhenaniae found in Germany, researchers extrapolated the length of the animal's body to be between 233 to 259 cm, using claw size to body length ratios from other sea scorpinons. Eurypterids are members of the extinct subclass Eurypterida within the class Merostomata of the subphylum Chelicerata, i.e. they were chelicerates (like spiders and scorpions) most closely related to the horseshoe crabs.

Eurypterids were aquatic and the buoyancy conferred by water may help explain structurally their large size, but what about the problem of gaseous diffusion to tissues? They presumably had an open circulatory system like other arthropods which is less efficient than the closed circulation of vertebrates. The authors hypothesise that the higher oxygen levels in the atmosphere in the past could have helped them attain their large size, or that it was driven by an evolutionary arms race with their prey.

Some questions to think about:

• Why is extrapolation using data from other sea scorpions a valid means of predicting the body length of the animal from only its claw?
  
• Among the extant (still living) chelicerates, how do the methods of gas exchange differ between the aquatic and terrestrial groups?
  
• What can we infer about its mode of feeding and possible prey?
  
• How can we explain why such giant arthropods are no longer extant today?