October 2003
Did Methane Cause the End Permian Extinction?
Two recent reports propose that a massive release of methane gas could have caused the extinction of much of life 250 MYA. They do however believe in different mechanisms. It has been thought that one problem at the P/T border was climate warming perhaps caused by volcano eruptions. As the oceans warmed methane gas seeped out of the oceans forming carbon dioxide and speeding the warming trend along. Not all believed that the warming could have done all the damage by itself. Gregory Ryskin from Northwestern believes that the methane welled up from the sea and incinerated everything on the land when it exploded by lightning. It could have then brought about more global warming or a nuclear winter. The death of 1,800 villagers near Lake Nyos in Cambodia in 1986 was caused by a cloud of carbon dioxide from the lake and this led Ryskin to this theory. However, there is no sign of this great fire storm in the rocks. The other theory is from Gregory Retallack of the University of Oregon who was not able to find strong evidence of a climate change at this P/T boundary. He believes that the increase in carbon dioxide would have affected the marine animals and also those on land. On land it was because it would have lowered the relative amount of oxygen available suffocating some animals with less efficient respiratory systems. Lystosaurus is one of the survivors was a burrower with a barrel chest. Amphibians also survived because they could burrow into lakebeds. The theories have met with mixed reactions so far.
Where Did Western Sediments Come From?
190 MYA Utah was covered with sand dunes. This is the Navaho Sandstone formation of today that covers an area the size of Texas and it can be as thick as 750 meters in some areas. Where did all that sand come from? Researcher Peter Reiners at Yale has radioactively dated small mineral grains called zircons from the formation. Using lasers they can determine when the mineral crystallized. They found that two thirds of them had cooled between 400 million and 250 million years ago. This corresponds with the rise of the Appalachian Mountains and the formation of the rocks from which they grew. How did they get to Utah? They must have eroded from the rocks of these new mountains and traveled west. Ripple marks in the sandstone formations in Utah indicate that the winds were from the south and southwest. They believe that there had to be a massive river system from the eastern mountains to the west carrying these sediments. Another study of the western sands at several sites indicate that about half of them came from the Appalachians and about a quarter of them came from central Canada. This confirms that the Utah dunes were supplied from far away.
Crinoid-Gastropod Interaction in Fossil Record
A well known biotic interaction found from the Middle Ordovician until the end of the Permian is the infestation of camerate crinoids by platyceratid gastropods. There are many fossils that show the firm attachment of the gastropods over the anal vents of the crinoids. One theory often given to explain this is that the gastropods were simply coprophagous (fed on excrement) and did not damage their hosts.
In order to test this idea the researchers (Gahn & Baumiller in Lethaia, Vol. 36) studied two groups of crinoids, one with 436 Gennaeocrinus variabilis from Michigan (30 infested) and a group with 188 fossils of Corocrinus calypso from Ontario (25 infested). The length and volume of the specimens were measured and it was found that the infested fossils were significantly smaller than those uninfected. They believe that this is caused by a parasitic relationship with nutrient stealing from the host.
The authors conclude that the short length of the parasite’s proboscis and the short gut length of the host allowed this relationship to work with smaller crinoids. Thus the larger ones appear to be less suitable with a longer tube to the anus. Looking at related Mississippian crinoids showed that they indeed had longer anal tubes to prevent this parasite’s access. In a few crinoids that did become infested it was found that the parasite had actually drilled a hole down to the base of the anal tube (in response to the crinoid’s evolutionary change?). So this relationship indeed looks like a parasite host situation that may also have created evolutionary change by both participants over the years.
Horner’s Museum Gets Big Dino Grant
A big $2 million grant has been given to the Museum of the Rockies to expand their dinosaur exhibit. It is from Tom Siebel the chief executive of Siebel Systems a software maker. He and his wife have two ranches in Montana and enjoyed their visit to the friendly museum with their two children. I wonder if Siebel has ever been to Chicago’s fine natural history museum?
Horner Names Top Predator
Horner gave his talk at the Natural History Museum in London at the opening of the new Predator/Scavenger Exhibit. He was asked if the T. rex was not the top predator of it’s time, what was? He answered raptors-really big raptors!! Boy I can’t wait until he finds some of their bones!!!
Exciting New Soft Bodied Fauna from Nevada
Burgee Shale type fossil sites are few and far between. Now there is a new one located in the United States. It is from the Lower-Middle Cambrian in the Comet Shale Member of the Pioche Formation in Lincoln County, Nevada (north of Las Vegas). It was reported in the July Journal of Paleontology in an article by Bruce Lieberman of the University of Kansas. It is a few million years older than the Burgess Shale but somewhat younger than the Chinese Chengjiang site. The specimens are replaced by hematite and are seen as iron staining in contrast to the Burgess Shale clay mineral replacements. The taxa found get through the Lower Cambrian-Middle Cambrian extinction while olenelloid trilobites did not. Some believe that this trilobite extinction occurred because each of the 100 species of Early Cambrian trilobites was confined to a small geographic area (craton), while the other soft bodied animals were geographically more widespread. This broader distribution may have saved them from extinction. They found one species of Canadaspis perfecta (also in Burgess) with carapace (about an inch long), parts of limbs (5 of 10 known limbs) and an abdomen with a probable alimentary canal. Another less complete specimen could be Perspicaris dilatus (which is very similar to Canadaspis) but it is less certain. Three species of Tuzoia were found. And two species of the top predator Anomalocaris were identified but these were based on incomplete specimens (90% of material found is disarticulated front appendages). One preserved body showed 9-10 paired body flaps and traces of a gut. They are tentatively identified as A. pennsylvanica (could be A. canadensis) and A. cf saron. A priapulid Ottoia was also found.
Did Dung Help Human Migration?
In an article in Science News (August 9) researchers were trying to determine how early human immigrants into North America around 14,000 YA could survive the trip through Beringia. Speculation was that with no wood for heating and cooking it would have been too difficult. However, they know that there were large herds of bison, mammoths, horses and wooly rhinoceroses that could have provided an ample supply of dung for burning. It is true that today people like some Tibetans rely on yak dung for their cooking needs in a climate that may approximate that of Beringia.
Oldest Spider Silk Found
BBC News reports that researchers have found spider silk within Lebanese amber that is dated to 120 MYA in the Early Cretaceous. This is 80 to 90 MY earlier than the previous spider thread found. There are small globules of sticky glue for catching prey still visible on the thread. As is often the case, this specimen was found in 1969 but its importance has just come to light. It is 4 mm long and resembles the silk in webs of the current day spiral web spinning garden spiders.
The oldest known spider in amber (Cremygale chasei) was recently found in on the Isle of Wight and is dated to 125 MYA. However, earlier fossil spiders have been found as early as the Devonian (350-420 MYA). Some of these early fossils also show the spinnerets of the spiders.
Bakker’s Book is Out – “Raptor Pack”
I got a copy of this new book. Bakker had technical help from Phil Currie and well known theropod specialist Tom Holtz. The drawings are great because they are by Michael Skrepnick. The book is geared to five year olds so I had to struggle through it. I have to say that it is well done with some narrative but lots of technical research to back it up. He has a group of Deinonychus after Tenontosaurus herds. He has the adults feeding the young that he says is proved by finding adult and baby teeth at the site of plant eater prey. He also had a new one – he said that Deinonychus would eat meat and bone, but would then upchuck the bones like owls do in pellet form. He says that he has found many of these theropod pellets in his digs. I don’t remember hearing about these in the technical journals!? Does anyone else?
Karen Nordquist, ESCONI Paleontology Study Group
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