Showing posts with label crayfish. Show all posts
Showing posts with label crayfish. Show all posts

Sunday, January 30, 2011

Why Eat a Rock? Gastroliths (‘Stomach Stones’) as Trace Fossils



During the past 30 years or so, trace fossils – such as tracks, burrows, nests, toothmarks, coprolites (fossil feces), and so on – have been steadily gaining more respect and recognition in paleontology. I would like to think this is a direct result of my dedicated “ichnoevangelism,” in which I have attempted to convert The Great Unwashed who fail to see the paleontological truth inherent to trace fossils, but the world of paleontology is much bigger than the Church of Ichnology (so far). Nonetheless, despite this overall increase in enlightenment, one type of trace fossil still causes some recalcitrant non-believers to turn gazes elsewhere and ignore their scientific worth. Those would be gastroliths, otherwise known as “stomach stones.”
Gastroliths extracted from the interior of a Cretaceous elasmosaur (a large, long-necked marine reptile) in central Queensland, Australia. Specimens are at the Stonehouse Museum and collected by “Dinosaur” Dick Suter in Boulia, Queensland. I know, they just look like a bunch of rocks, not trace fossils. Please read on, and prepare to learn.

Saturday, November 13, 2010

Cretaceous Worlds of Queensland, Part III: Hughenden, on the Edge of the Cretaceous


If you want to visit the former locations of the Cretaceous seaway that cut through Australia 100 million years ago, as well as its coastal and landward environs, the easiest way to do this is to fly into Townsville, Queensland (mentioned in last week’s entry), rent a car, and drive west.


This is the point in the narrative where someone might invoke the cliché, “Go west, young man,” but I do not qualify as “young” any more, plus my wife - Ruth – was with me on this journey. Thus inclusivity, as oppposed to ageism and sexism, negate my saying that phrase. Regardless, I try to avoid clichés like the plague, but your mileage may vary, depending on how you roll the dice. (After all, no matter where you go, there you are.)


A paleogeographic map of northeastern Queensland 100 million years ago, during the Cretaceous Period; map from the Museum of Tropical Queensland. Arrow points to Hughenden, the subject of this post. Notice how that area was coastal then (the white part represents the inland sea). Also note the inconvenient lack of roads during the Cretaceous.


Renting a car in Townsville for going into the Australian outback can be a bit tricky, as rental agencies frown on their vehicles going onto unsealed surfaces, including dirt roads. In sympathy with rental agency employees, who probably have a litany of horror stories about crazy foreigners destroying life, limb, and (most importantly from their perspective), property, I certainly understand the “off-road” restriction for a car that does not have four-wheel-drive, roll bars, exhaust pipe running above the roof, Kevlar tires, and other battle-ready accoutrements that many Australians advocate for driving in their continental interior. But to me, it seems too cautious to keep perfectly fine all-wheel-drive (AWD) cars off dirt roads that are marked clearly on a standard road map and government maintained.


So for the sake of privacy and not wanting to offend the agency that so kindly rented us a vehicle, please consider any mentions of driving on dirt roads as pure fiction.


The sport “ute” (utility vehicle) used for field work in Victoria, Australia during The Great Cretaceous Walk in May-June 2010, courtesy of the Museum of Victoria. This is the type of field vehicle you need to take for dealing with the harsh Australian outback, although a good number of Australians in recent years have been using them for just driving to Woolie’s to stock up on vegemite and VB. Alas, we lacked such a vehicle in Queensland, yet we somehow survived.


We did take one serious precaution that many of our Australian friends suggested, which was to keep lots of water in the car. This safeguard is in case you get a flat tire or otherwise break down several hundred kilometers from the next town, as help might be a long time in coming and you should have plenty of drinking water on hand. Fortunately, Townsville has many grocery stores that stock 20-liter jugs of water, so we purchased two of these and kept them in the “boot” (or “trunk,” for all you Yanks out there). Incidentally, these jugs rode several thousand kilometers with us and ultimately returned unused to Townsville, which we donated to our hotel before departing. Oh well: better safe than thirsty.


Properly stocked with our sloshing supply of dihydrogen monoxide (the deadliest substance known to humankind), we left on the morning of June 30, and drove southwest for about three hours – passing through only a few pub-hotel “towns” along the way – before arriving at the first paleontologically significant town, Hughenden. I had visited Hughenden about three years previously (2007) during a whirlwind weekend trip from Townsville to the outback (and back), and was looking forward to seeing it again. Of course, I was also curious how it might have changed during the intervening time.


What to see in Hughenden, and why stop there, especially if someone is eager to make it to Winton? Well, how could a dino-phile avoid pausing for a visit after being greeted by a life-sized replica of the ornithopod dinosaur Muttaburrasaurus langdoni? This prodigious example of paleo-statuary is hard to miss, and is easily spotted on the right side of the road as you drive into town, located next to an old-fashioned outback pub hotel (sadly closed).


The large and very friendly Cretaceous ornithopod dinosaur Muttaburrasaurus, a roadside icon for Hughenden. Look at the size of this beauty! Photo by Ruth Schowalter.


Hughenden also has a very nicely arranged display of local fossils and some information about the local natural and human history, housed in the Flinders Discovery Centre. For only $3.50 (AUD) admission, you can see a short film about the geologic history of the area (which actually was quite good), walk and gawk through the display to your heart’s content, take as many photos as your digital-memory card can hold, and otherwise enjoy learning about the rich natural history of central Queensland. The star of the display, though, is a mounted cast of a Muttaburrasaurus skeleton.


If you didn’t like the Disney version of Muttaburrasaurus pictured earlier, here’s the Tim Burton one, which can be viewed in all of its awesomeness in the Flinders Discovery Centre.


This dinosaur, besides having what is probably the most fun-to-say dinosaur name (other than Micropachycephalosaurus), is the largest known ornithopod in Australia, which was apparently overrun with smaller, “hypsilophodontid” dinosaurs, especially in Victoria. Also unlike the Cretaceous dinosaurs of Victoria, this dinosaur is known from a nearly complete skeleton, including a skull. It derived its colorful name from a small town south of Hughenden near where it was found – Muttaburra – which in turn is named after an indigenous word, meaning “meeting of the waters.” This is a very insightful appellation, reflecting how this now-dry (almost desert) area did indeed meet a Cretaceous seaway 100 million years ago.


Other fossils are in the Flinders Discovery Centre, most of them Cretaceous, and most of them local, thus showcasing the paleontological importance of this area for understanding Cretaceous life in Australia. In fact, bones from some of the Cretaceous marine reptiles, giant clams (Inoceramus), and ammonites were recognized in this area during the mid 19th century. Many such fossils – most of them real – were out in the open, allowing for unfettered photography, and those below glass in cabinets also beckoned for a close look. (And just as a curmudgeonly aside, I love these smaller, local museums for putting real fossils on display, eschewing the “bells-and-whistles” virtual-reality displays embraced by so many other museums in recent years.)


Wow, look, real Cretaceous fossils! In this case, ammonites of all shapes and sizes, with a modern Nautilus thrown in for contrast and scale.


This beautiful fossil decapod, simply labeled as “Crayfish,” is most likely a marine species, and not a freshwater crayfish (“yabby”) for which Australia is famous. Its label also says it is from the Cretaceous, so it would be nice some day to know its exact taxonomic affinity. After all, I have a keen fondness for Australian freshwater crayfish from the Cretaceous.


And you just knew this ichnologist was not going to neglect mentioning trace fossils, and the center had a few displays about those, too.


Cast of a large Australian theropod dinosaur track, which was labeled as “Allosaurus footprint,” but is probably not from that genus, which is North American. (Close enough, as it certainly was made by a large, Allosaurus-sized theropod, though – so no harm done.)


Branching invertebrate burrows preserved in a limestone as natural casts. These burrows are what most ichnologists would call Thalassinoides, trace fossils that are normally associated with crustacean tracemakers.


Ruth was delighted with the artistic portrayals of dinosaurs in the center, some of which would no doubt evoke snickers, chuckles, chortles, and outright guffaws from some of my paleontologically oriented friends because of their postural and chromatic inaccuracy (the dinosaurs, that is, not my paleo-friends). Nonetheless, we enjoyed seeing these included in the display area too, and appreciate all of the local effort that went into constructing these homages to all things dinosaurian.


Kitschy dinosaur-inspired sculptures in the Flinders Discovery Centre, which I think are of an ornithopod (left) and sauropod (right). And if you don’t like them, make your own bloody dinosaurs!


And if that isn’t enough to satisfy any artistic yearnings, metal sculptures of a dinosaur and pterosaurs adorn public spaces outside the center, lending some whimsy along with the well-deserved local pride.


It’s not Truckasaurus, but it’s pretty close. Nicknamed “Darby the Dinosaur,” this sculpture was inspired by Muttaburrasaurus, then conceived and made in 1998 by local artists Terry Lindsay and Sam Brown. They put together whatever spare parts they could find, set their creation in concrete, and garnished it with real Cretaceous fossils (below "Darby").


This would be the last thing you would see if a pterosaur became a Transformer. (Yes, I know, big “if.”) The sculpture is nicknamed “Leanneosaur," and coincidentally, one of the artists (Shane Rogers) who created this metallic menace has a wife named Leanne. The other artist was Terry Lindsay, also partially responsible for “Darby,” and the piece was completed in 2004.


So Hughendgen is a great place to visit for paleo- and art-nerds alike (Ruth and I qualify as both). In fact, we liked Hughenden and the Discovery Centre so much, we made a point of stopping there on our way back to Townsville nearly a week later. That is when Ruth and I purchased a dinosaur hand puppet (a theropod, of course), which was put to good use in a dinner-theater performance only a few days later. (Digression? No, foreshadowing.)


So Ruth and I spent one night in Hughenden, then were off in the morning to our next stop on the “Dinosaur Trail,” which was Winton, a town that lives off past lives of the Cretaceous, as well as the much more recent past. Why? Tune in next week, when I’ll talk about Winton and its connections to paleontology, the unofficial national anthem of Australia, bush poetry, and beer (and perhaps not in that order).


Tuesday, May 25, 2010

Luck, Preparation, and Opportunity: Part II


"You won't find anything."


This assurance came from Tom Rich as he drove, and me as his sole passenger on a quick trip to the Victoria coast. At his invitation, we were traveling together to Flat Rocks, the Dinosaur Dreaming dig site near Inverloch, Victoria. It was late February 2006 and the last weekend of the dig season there. It was a privilege for me to witness the closing of yet another successful field season and meet some of the people associated with Dinosaur Dreaming. But at the same time I was entering an intellectual unknown.



Dinosaur Dreaming, February 2006


I had been in Australia for less than three weeks, on a sabbatical from Emory University for the first time in 16 years. The primary reason for my being there was to work with Patricia (Pat) Vickers-Rich on a geoscience-education project, but I was open to any other opportunities that might arise. So when Tom asked me if I would like to come with him to the coast, I emphatically said “yes,” albeit with a blend of awe, excitement, and trepidation. The last of these feelings stemmed from my being in a new place, with new people, and new rocks (an example of how “old” becomes “new” in geology). The still-healing fractured tibia in my right leg, the result of a biking accident only a month before, also reminded me to take it slowly, and I had brought a walking stick with me to help with traversing the flat platform of rock. (Yes, the person who first named “Flat Rocks” must have had a lack of imagination that day.)


Flat Rocks, near Inverloch, Victoria.


Tom’s pessimistic statement came in response to my observing that in 14 years of work at the Flat Rocks site, a source of some major paleontological discoveries, no trace fossils had been detected, yet I expressed hope that I would find some there. His pessimism, though, was based on what was known then. The only trace fossil described from Early Cretaceous rocks both east and west of Melbourne was a single, small dinosaur track from the Otway Group, in rocks dated at about 106 million years ago and from Knowledge Creek. Pat and Tom found this track in 1980, during their only time to Knowledge Creek, a place they swore they would never visit again because of its remoteness and difficult access.


No fossil burrows, not even those of invertebrate animals – such as insects or crayfish – had been reported from kilometers of expansive Cretaceous outcrops. Invertebrate trace fossils, especially burrows, are normally the most common trace fossils in any given sedimentary rock sequence, and I thought it was unusual that none had been described after more than 100 years of geological research in this area.


Fortunately for both of us, Tom was wrong. I found two isolated large theropod dinosaur tracks the first day, the first such tracks discovered from this site, then found fossil crayfish burrows the day after that.


Fossil crayfish burrows at Flat Rocks, Strzelecki Group, 115-120 million years old. Burrows were filled with a differently colored sand while the surrounding sediment was still soft, and both sediments later cemented to form sandstones. Photo scale = 10 cm (4 inches).


I promptly celebrated this discovery by sitting on them.


Me sitting on Cretaceous fossil crayfish burrows: photo by Gerry Kool.


Although the dinosaur tracks were nice to find, I actually was more excited about the second day’s discoveries, for reasons explained later. The fossil crayfish burrows led to a paper that took nearly two years to write and publish, but one that was well worth it for its contributing to the solution of a 130-year-old evolutionary puzzle first posed by famed evolutionary scientist Thomas Huxley.


This new knowledge thus alerted future dig crews to start looking for more trace fossils, and especially dinosaur tracks. Sure enough, the next year, in February 2007, an undergraduate student, Tyler Lamb, found a third large theropod track, only 5 meters (16 feet) from the dig site.


Large theropod dinosaur track, preserved as a sandstone fill of an originally concave feature, and weathered out in bold relief. Yup, same photo scale as in the previous picture.


The humbling realization for everyone after this find was that hundreds of volunteers and professional paleontologists had walked across this track for nearly 15 years, unknowingly putting their feet on the same spot where a dinosaur had stepped 120 million years earlier. Hence my own luck, preparation, and opportunities enabled others to make their own discoveries, using the same winning combination of fortune, knowing what to look for, and circumstance.


Tomorrow, Tom and I leave together for Inverloch and will walk over the same rocks, more than four years ago, with both of us expecting to be surprised by what we find. The next post should be about our progress, but also be looking for one that explains why the fossil crayfish burrows were more important to science than the dinosaur tracks, and how these were connected to Mr. Huxley.