Tuesday, November 25, 2008

Nothing new under the sun...

I am busy these days. Accordingly I have no time to post some relevant stuff. As I browsed through some pictures, I realised that I tend to wear ridiculous headgear when being in the field.

Friday, November 14, 2008

And now all together: Chirotherium is not an Archosaur!

Actually this one is not really important and I thought about publishing this post altogether. Although it is rather a popular problem than a scientific or academic one, it still teases me. You can find it everywhere: Newspaper, blogs and wikipedia for instance. Trackways of the ichnogenus Chirotherium are constantly mistaken for an Archosaur or related creatures.

For instance, the german Wikipedia article on Chirotherium: Fossilised footprint (ichnite) of the ichnogenus Chirotherium, an archosaur of the Lower Triassic, first found 1833 in Hildburghausen (Thuringia, Germany).

This is just wrong. An archosaur cannot be an ichnogenus.

Unfortunately, Chirotherium literally means something like "hand beast" or "hand animal". However, the term Chirotherium is scientifically used for a certain type of trackway(s), which is found in Sediments with a Triassic age, ranging from Olenikian to Anisian (KLEIN & HAUBOLD, 2007). In fact, Chirotherium is the first scientifically described trackway (KAUPP, 1835) and, by the form of the pes imprints (rear leg) resembling human hands, it animated the early palaeontologists imagination for the mysterious ancient beast that once left its trackway on the wet sand of the vast Triassic plain. In a way the "hand animal" is a chimera of those early days of palaeontological research. From a modern point of (ichno)taxonomic view, the scientific name Chirotherium, however, is attributed to the trace fossil only, although the trace maker most likely was an archosaur of some sort. Yes, you are right, this is scientific quibble but still; it is not correct.
Yours Ichnogeek!

Chirotherium (pes imprint) from the Triassic of Germany.

The "Chirotherium Monument" with a reconstructed "hand beast" (Hildburghausen, Germany)


Kaup, J.J., 1835: Über Thierfährten bei Hildburghausen. Neues Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefaktenkunde. v. 1835, pp. 227-228.

Klein, H., Haubold, H., 2007: Archosaur footprints - potential for biochronolgy of Triassic contintal sequences. In Lucas, S.G., Spielmann, J.A., (eds): The Global Triassic. New Mexico Museum of Natural History and Science Bulletin 41.

Monday, November 10, 2008

Traces First #1: The Cambrian Explosion (CE)

Phew! This is truly the flagship among evolutionary progresses and one single post surely cannot embrace a topic that provides enough material to fill up book shelfs. In the course of writing this post it became more and more apparent that it is by far too simplistic just to tell that the presence of trace fossils proves that complex bilateral animals inhabited the sea floor long before they are found in decent body fossil faunas. Although this statement would be the very essence in order to maintain the idea of "traces first", the comparison of these two archives and stating that one predates the other is like comparing the incomparable. I will, anyhow, try to emphasize the role of the ichnology in this event later but first I need to take a deep breath and one step back to provide a minimum of framework.

The first and most obvious message: The "Cambrian Explosion" is a term describing the sudden appearance of numerous "modern" phyla in the fossil record. Nothing more and nothing less. This statement is, in a way, the lowest common denominator of the CE-research, because it just outlines the plain observation. Some people confuse the sudden appearance with absolute evolutionary progress. This might be true but actually this is just one way to interpret it. Although much research has been devoted, it still remains enigmatic in several concerns. But it has been proven that the appearance of complex organisms in the fossil record is one of the last chain links in a cascade of modifications in the earth system. Steps of such an impact are not "sudden" nor do they result from a single causative event. The Cambrian radiation (I like this term better) has a (even on the geological time scale) long and complex prologue. So when did it really start?

Fig. 1: What has Christmas to do with the Cambrian Explosion?

Deck the hall with boughs of holly, Fa la la la la la, la la la la.
When does Christmas start? Some people may say at first Christmas holiday when the children get up early to receive their gifts. Other (german) people may say: No, it's on Christmas eve already. You see, it is a local phenomena. However, this is not the whole story. You have to go and get a tree, bake cookies, buy and prepare all the food, invite your relatives, tell Santa what to get for your kids, set up the decoration, make everything shiny etc. pp. In Germany, we have all this tradition like the "Weihnachtsmarkt" (Christmas market?), Nikolaus and so on. This stuff probably all belongs to Christmas as same as Santa Claus, presents and the tree at Christmas eve itself, doesn't it? Yes, for sure, but the true point of no return is when your children and all other relatives unwrapped their presents and gifts and everyone is happy with his/her new toy, jewellery, fragrance, shirts, socks, ties etc. The living room is a mess, everyone is drinking wine, the turkey is torn into pieces, your cat is going crazy and over the next days, you will have to go and visit all the other people you missed for the whole year probably. Although these are holidays, everyone is very busy. But as I noted above, there is many stuff going on in the "advent" of this event already. It requires much preparation to make all this happen and if one parameter is missing, it cannot really be Christmas then for some people.

My opinion: If we look at the beautiful fossil lagerstätten like Chengjiang and Burgess Shale, we see the holidays - the very essence of the event, when everyone is busy, has new toys to experiment with and so on. In some concerns this analogue might not be very appropriate but I think it is very instructive and fairly outlines the complexity. From all what we know (and I read), one cannot really say: "here it all started". It was a process.

Fig. 2: Treptichnus cf. pedum from the lower Middle Cambrian of Jordan. This is not a very typical specimen. We found it during the field session in Jordan. Photo courtesy of G. Mángano.

Trace fossils and their role in the "Cambrian Explosion"
So now back to the actual business. What is the role of ichnology here? As I noted above, the most simple message is that some trace fossils are so complex that their creation requires sophisticated nervous systems and locomotory mechanisms as well as some sort of motivation (= behaviour). Accordingly, trace fossils demonstrate that there were animals, which did match all this characteristics, already before some of them passed into the body fossil record. Therefore, the first really complex trace fossil Treptichnus pedum (fig. 2; for taxonomists: some people prefer Trichophycus pedum, originally described as Phycodes pedum, Seilacher 1955) was chosen to define the base of the Cambrian. T. pedum is an array of alternating banana-shaped burrows that have been created within the sediment. To describe it properly, all three spatial dimensions are needed. Thus, it is a true burrow created by a bilateral-symmetrical animal. In other words, the trace maker had a left and a right side, it had a sense for "up" and "down" and it probably possessed an aperture for all incomings and one for the rest. Older trace fossil assemblages from the Ediacaran are characterised by the presence of horizontal traces only. Typical strategies employed by Ediacaran biota are surface scratchings, horizontal (under-)mat mining, rather unspecialised superficial grazings and something like that. Around the Precambrian-Cambrian-transition, the discovery of the third dimension by benthic organisms had tremendous impact on the environment and the whole face of the earth.

Fig. 3. Cartoon illustrating the 'Agronomic Revolution'.
From Fedonkin et al. 2007. Drawing by Peter Trusler.
I think there is an error at the lower right. It should be "phanerozoic mixgrounds".

What has been very instructively termed by Seilacher (1997) as the "Agronomic Revolution" or "Trophic Escalation", illustrates the fundamental changes across the the pC-C-transition (see fig. 3). First of all, there is a new strategy as demonstrated by deep vertical burrows (Skolithos, Monocriterion, Arenicolites, Teichichnus to name a few): Infaunalisation. Animals appreciated to colonise the sediment column, which is in fact really advantageous because it provides protection from abiotic and biotic stress factors. Furthermore they were able to explore new food sources. (1) Infaunal detritus feeding: Think of the wasted resources in the Ediacaran. Plenty of organic matter that just has been buried beneath sticky algal mats. (2) Suspension feeding: No matter how strong bottom currents are, just evert your feeding apparatus and current will do the rest without disturbing you in your nice burrow. (3) Passive predation: Wait in your hole for a prey that strolls along your burrow. All in all a very progressive strategy. This biotic invention didn't change only the ecological conditions significantly. It affected whole chemical fluxes in the entire ocean. All the soluble components like phosphate, calcium, silica, magnesium re-entered the marine chemical cycle by deep and thorough bioturbation at the expense of mat-sealed sediment-water interfaces. The composition of sea water presumably changed completely. This, in turn, most likely made the subsequent biomineralisation event possible altogether. This fundamental modification was in a way the advent of the big party that is recorded by the terminal Lower Cambrian fossil lagerstätten.

Further complication? Here we go: Jensen (2003) subsumed that rise of trace fossil complexity is not just documented from the lowermost Cambrian. He stated, and convincingly demonstrated that the "Neoproterozoic trace fossils represent the initiation of a rapid but gradual build-up of infaunal activity, which increased markedly in the Cambrian". Furthermore he concludes that the presence of some distinct trace fossil (e.g. Spiroraphe) together with Ediacaran forms suggests that the evolution of bilateral animals is already under way. So when did the so called "Cambrian Explosion" start? You know what? I really do n't know.

Some key resources for this topic are: Seilacher (1956), Seilacher (1974), Crimes (1992), Droser et al. (2002) as already noted Jensen (2003), Seilacher et al. (2005). This story is by far not completely told yet and, in fact, the evaluation of trace fossils in connection with the CE is still a hot frontier in geo/biosciences.


Crimes, T.P., 1992: Changes in the trace fossil biota across the Proterozoic-Phanerozoic boundary. J. geol. Soc. London., vol. 149, pp. 637–646

Droser, M.L., Jensen, S., Gehling, J.G., 2002: Trace fossils and substrates of the terminal Proterozoic–Cambrian transition: Implications for the record of early bilaterians and sediment mixing. PNAS, vol 99. no 20, pp. 12572-12576.

Fedonkin, M.A., Gehling, J.G., Grey, K., Narbonne, G.M., Vickers-Rich, P., 2007: The rise of animals. Evolution and Diversivication of the Kindgom Animalia. Johns Hopkins University Press, Baltimore.

Jensen, S., 2003: The Proterozoic and Earliest Cambrian Trace Fossil Record; Patterns, Problems and Perspectives. Integr. Comp. Biol., vol. 43, pp. 219–228.

Seilacher, A., 1955. 4. Spuren und Fazies im Unterkambrium. In: Schindewolf, O.H., Seilacher, A. (Eds.), Beitrage zur Kenntnis des Kambriums in der Salt Range (Pakistan), Akademie der Wissenschaften und der Literatur zu Mainz, Mathematisch-naturwissenschaftliche Klasse, Abhandlungen, vol. 10, pp. 373 – 399.

Seilacher, A., 1956. Der Beginn des Kambriums als biologische Wende. Neues Jahrbuch fur Geologie und Palaontologie, Abhandlungen 103, pp. 155–180.

Seilacher, A., 1997: Fossil Art. Royal Tyrell Museum of Palaeontology, Drumheller, Alberta, 64 p.

Seilacher, A., Buatois, L.A., Mángano, M.G., 2005: Trace fossils in the Ediacaran–Cambrian transition: Behavioral diversification, ecological turnover and environmental shift. Palaeogeography, Palaeoclimatology, Palaeoecology, vol. 227, pp. 323–356.

Friday, November 7, 2008

I highly DO NOT recommend...

...the following book:

Elewa, Ashraf M. T. (ed.), 2008: Mass extinction. Springer

I like mass extinction events. Accordingly, this book catched my eye as I browsed through the shelves of our library. Back home, I started flipping some pages and reading here and there - awfull. Except for the guest authors articles, which are well done, this "book" appears to be cheap joke.
All of the editors articles (9 of 15) are short, badly written and not sufficiantly referenced. For example, the author refers constantly to wikipedia articles or cites for every occasion standard palaeo textbooks that are suited for undergraduate education. The chapters are filled with fuzzy standard statements and do not really help the reader to get into the topic. In fact, most wikipedia articles provide a more profound picture on certain aspects. For instance the chapter about the Permo-Triassic extinction event beggars all description. It barely covers 1.5 pages and provides very blurry general information without presenting any evidence or serious references. A fourth of the article is wasted for comparision of the PT-event with Agatha Christie's "Murder on the orient express".

Just one example from page 129:"One of the mysteries of the history of the Earth is the layer of clay that was deposited around the entire globe approximately 65.5 million years ago. It is also known as the K-T extinction event [...]."

Don't get me wrong - I really don't want to tease the editor, but this is just a very bad book that costs the unhappy purchaser 135 € (170 $). I am still wondering how this book came through the review at Springer. Perhaps they hoped to make some money because most library order books unseen.

Long story short: Please do not buy this book!

Monday, November 3, 2008

Traces First #0: Preface

In this little series, I would like to review selected (may be popular) peculiarities of the fossil record that prove the relevance of trace fossils within earth system science as well as evolution. I hope I will find some time to review some instructive examples from the literature; it appears to be a rule: Evolutionary advances, pioneer colonisation patterns and other "events" or trends within earth history that are known from the body fossil record are frequently predated by findings of trace fossils.

After you have digested this arrogant statement, I will explain some concepts that are essential in understanding the distinctiveness of both archives of fossil record.

(1) The preservation potentials of body and trace fossils are different
In general, the preservation of a body fossil requires by far more lucky coincidences than preserving a track way. First of all, a trace or a track way records a short time span of an individual organism. Walking Reptiles or arthropods may produce thousands of trackways during their life time. Hence, the abundance of potential trace fossil specimens exceeds that of the corresponding trace maker by several orders of magnitude. Furthermore, it is not only a question of sheer probability. To fossilise a whole animal requires more peculiar conditions such as rapid burial, anoxic environment, and no benthic activity, for instance. Trace fossils (just) need to be created. They usually stick to the place where they have been maintained, called "in situ". However, they may be readily altered by subsquent benthic activity. Shallow marine sandstones are frequently thouroughly bioturbated, which actually means that they are full of trace fossils. As you see, to form trace fossils at all, well-oxygenated conditions are required to host a rich fauna. And this, by implication, means that animals itself are not very likely to become fossils. Dead organism would readily become consumed by benthic activity and oxygenation processes. To conclude, preservation potential for both types of fossils is not only different, virtually it is mutually exclusive but for some rare exceptions.

(2) Trace fossils are in situ structures
As outlined above, trace fossils are rarely transported. They are observed at the place where they have been created. The implications for ecology are, thus, more convincing than body fossils that are frequently transported and become buried at a different site.

(3) Similar trace fossils can be created by numerous organisms
In particular, invertebrate traces of the same ichnogenus or even ichnospecies can be produced by a variety of animals, which at a first glance diminishes their utility in palaeontological studies. But as they record principal strategies employed by a number of phyla, they are suited in the tracking of general trends in evolution such as infaunalisation, terrestrialisation etc. For me it does'nt really matter which critter got his feet at first on dry ground. It is more important that someone did it, is'nt it. However, I must admit that the "who done it?" question teases probably everyone.

(4) Trace fossils were created by organisms that otherwise won't have any fossils record
For an animal with no hard parts, it is fairly difficult to become a fossil. Preservation of soft tissues requires special circumstances. E.g. Worms are the main bioturbators in the marine realm. But in comparision to their impact on the ichnologic archive they left virtually no body fossil record.

These are just four concepts that explain the importance of ichnology in earth system science. May be I missed some points. I will keep this post updated if something pops into my mind.

Saturday, November 1, 2008

Volcanic Rocks in Wells Gray Provincial Park

Although, I am not really into non-sedimentary rocks, the lavaflows that are beautifully exposed in Wells Gray Provincial Park (BC, Canada) really attracted my attention. I got there rather coincidentally when visiting my cousin in Summer 2007. He took me out to visit Wells Gray. Awesome place to rearrange the picture I once thought how Canada is like. I spent two months in Saskatchewan before this trip and did not see anything that usually pops into your mind when you think of Canada - just vast plains with nothing but corn elevators and endless roads and rails. Back to Wells Gray. Although i don't like articles from Wikipedia too much, this one about the Wells Gray-Clearwater volcanic field is well written and extraordinarily well referenced. Essentially, i picked the information from the references therein.

This is Pyramid Mountain. Although it looks like a typical cinder cone, it is proven to have been formed beneath a remarkable glacial cover. However, the eruption was presumably vigorous but short. Accordingly, this volcano lacks the flat-topped Tuya-morphology that is expected for subglacial volcanoes. The volcanic activity of this particular region spans from the Pleistocene to the Holocene.

Helmcken Falls. Water that incises basaltic lava-flows.

Cliff of eroded stacks of lava-flows.

Close-up of the same outcrop. The flow dircetion is hardly to identify. In the upper third you see a fairly lenticular body. This might represent a lava flow perpendicular to the cliff-face. However, all "beds" are quite parallel and very regular.

Me being happy with a hard-earned sundae. At my place in Saskatoon, I watched TV sometimes and always got tempted by stupid but effictve (as you see) commercials from Diary Queen. They always showed sundae copulating with fudge, cream, chocolate chunks and so on. Accordingly, I decided that I won't leave Canada without plundering a DQ. What could I say - was worth it.