Our Cenozoic Mammalian Cousins (continued) (November 26 – 30)

Please review the links from last week as we continue discussing the Mammalian Radiation in the Cenozoic.

One of the interesting questions in the history of Earth’s climate is why the planet began a precipitous cool-down in the middle Eocene, about 49 million years ago. You know that the most likely answer is that carbon dioxide levels were reduced, lessening the Greenhouse Effect and leading to global cooling. How would that happen? One strong hypothesis is that the rapid growth of an usual fern, Azolla, in the Arctic Ocean drew down carbon dioxide levels and then, by dying and being buried in ocean sediments, sequestered that carbon away from the atmosphere. This is called the Azolla Event. Azolla is still very much with us today. Maybe it can help with our current global warming problem?

Here is the Fall 2018 Final Exam description. (Test seating: Students with last names starting with A through L in Room 205; M-Z in Room 216.) You’ll want to start studying. Those superquizzes will be your encouragement!

The review session this Friday will be 3:00 – 4:00 pm in Scovel 205. (I have a 4:00 pm meeting.)

Mammoth tooth surface (Pleistocene of Ohio).

Geology in the News –

The hemimastigophorans are a strange group of organisms currently classified at the phylum level. Recent genetic studies show that they are radically different from animals, protists, fungi and plants, meaning they represent a branch of life at the ‘supra-kingdom” level. There is still so much we don’t know about life, let alone life’s history.

A 31-kilometer-wide impact crater has been discovered under Greenland’s shrinking icecap. So far it has been dated to be sometime in the Pleistocene, but there is much speculation that is is connected to the Younger Dryas climate event. For an excellent review of the topic, see Dr. Crawford’s recent blog post.

A cuddly little therapsid named Kayentatherium has been found preserved with 38 tiny babies. This discovery has implications for mammal evolution because this clutch size is more reptilian than mammalian.

 

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Our Cenozoic Mammalian Cousins (November 19)

We had our introduction to mammals back in the Triassic. They were ratty little critters then, but now that the non-avian dinosaurs are gone our mammals have become very serious and prolific.

So many mammal groups appeared in the early Cenozoic that we cannot cover them all in this course, or even mention many of them. That diversity dilemma is actually part of the story of the extraordinary adaptive radiation of the mammals. Note that the three-part division of mammals we see today (monotremes, marsupials and placentals) began in the Cretaceous. You may also want to refer to the mammal evolution site on Wikipedia, which is very well updated.

Again, the webpages from Berkeley will be highlighted here because they are organized in the most useful ways for us. You will want to look at their short rodents page. Now jump WAY up to the proboscidean (elephants, mammoths, mastodons) page just to delight in the wondrous variety in modern mammals. There are many sites devoted to mammoths, mastodons and other “Ice Age” mammals, including the Pleistocene exhibits at the Russian Paleontological Institute. Carnivores are always interesting, and are in themselves highly diverse. They include wolves, dogs, cats, raccoons, bears, weasels, hyenas, seals, and walruses. A hero to your cat is the ancient sabretooth, highlighted in special exhibits this year at Berkeley and the Illinois State Museum. (Watch an old school animation of a sabretooth from the BBC.) You can now make another mammal diversity leap to our unlikely cousins the cetaceans (whales and dolphins; here’s an Eocene whale found a few years ago in Egypt). The ungulates, or hoofed mammals, are an excellent group to use in a study of evolutionary patterns. The artiodactyls (cloven-hoofed mammals) include the prosaic sheep, goats, camels, pigs, cows, deer, giraffes, and antelopes (and now whales!). Their relatives the perissodactyls (“odd-hoofed” mammals) include rhinos, horses and tapirs today, but they were much more diverse in the past. The evolution of the horse is a classic story, told well at the “Fossil Horses in Cyberspace” site at the Florida Museum of Natural History.

Here is the Fall 2018 Final Exam description. (Test seating: Students with last names starting with A through L in Room 205; M-Z in Room 216.) Even though the final is about a month from now, you’ll want to start studying. Those superquizzes will be your encouragement!

Remember: Review sessions every Friday, 3:30 – 4:30 pm, in Scovel 205.

Mammoth tooth from the Pleistocene of Ohio.

Geology in the News –

There is an interesting argument that the Late Cretaceous asteroid hit just the right spot to cause the global extinctions. The hypothesis is that striking an area rich in petroleum injected massive amounts of soot into the atmosphere that further cooled climate. There will be debates soon over this.

Here is an excellent BBC article on saving coral. Are we willing to make the change to ensure the survival of coral reefs and thus oceanic ecosystems? So far the answer is a grim no.

The search for Oort Clouds around other stars has yielded surprising results, with some evidence suggesting they go back to the early days of the Universe.

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Catastrophe: The Cretaceous Mass Extinctions (November 12-16)

The story of the Cretaceous Mass Extinctions is amazing. The “Impact Hypothesis” was developed at the University of California, Berkeley, in 1980 when I was there as a graduate student (to my great fortune, even if I had nothing to do with it). It seemed a real stretch at the time, but now we know it as one of those intellectual breakthroughs which changed our perspective on the History of Life. The Wikipedia page on the Cretaceous Extinctions is very good and kept updated by experts. The Sam Noble Museum has a good executive summary of the extinctions. In 2010 an Independent Study student (Megan Innis) and I had a great time at the Cretaceous-Paleogene boundary in Alabama and Mississippi.

We will emphasize the Impact Hypothesis in this course because I think it is the one best supported by the evidence. If you like your extinctions via YouTube, watch these Discovery Science videos, part 1 and part 2. The volcanic hypothesis is still alive, although on life support. Here is a nice summary of the most recent attempts to link volcanoes to the Cretaceous extinctions. In contrast with these reasonable (more or less) disputes, there are many more exotic ideas about dinosaur extinctions specifically, some tallied here and here. Let’s not forget, though, that the basic scenario of the impact hypothesis is supported by most scientists.

Remember: Review sessions every Friday, 3:30 – 4:30 pm, in Scovel 205.

The view of it here in The Netherlands, though, is far different. We explored it from below in the Maastrichtian tunnels at Geulhemmmerberg (N50.86692°, E5.78357°).

Geology in the News –

The end-Cretaceous asteroid impact may have had an even more dramatic effect on climate than we thought (and that was pretty bad). I notice here that the asteroid is now expanded from 10 to 12 km in diameter. Here’s a BBC account of the same research.

Mount Etna, Europe’s most active volcano, is slowly sliding into the sea. The fear is it could catastrophically collapse, producing massive tsunamis. (I’ve been on its slopes, by the way. Fantastic place.)

Check out this story (and book) about the illegal trade in dinosaur bones. I’m pleased to see there are serious penalties for stealing from the public — and from science itself.

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The Greening of the Earth: Evolution of Plants (November 9)

Remember: No classes on Monday and Wednesday this week. I’m in Indianapolis with a large contingent of Wooster Earth Scientists at the annual meeting of the Geological Society of America. I’ll be giving this talk on Wednesday afternoon. Wish me luck.

We’ll start Friday with a review of your second test results, then begin our discussion of early plants.

Plants have been in this course for awhile as a leafy background to tetrapod evolution, but now it is time to take them seriously. The best place to start a general survey of our very distant green cousins is with the summary Tree of Life page on land plants (embryophytes). There are lots of links there. Berkeley’s fossil plants range chart may be especially useful, although we won’t be using most of the names given there. The most detailed plant website is the University of California on-line paleobotany lab. The diagrams and hierarchical systems of detail here are impressive. You may want to scan these pages for the beautiful line drawings alone. If you want professional detail of fossil plant systematics and distribution, click the homepage of the International Organisation of Palaeobotany.

Here’s a ginkgo webpage for everything you want to know about this beautiful tree common on our campus (although it is hardly the only “link between the lower and higher plants”). What is the tallest plant and where is it? A redwood in California measures an astonishing 379 feet.  Check out the oldest living plant — an impressive 13,000 years of life as a clone. It’s also in California. Finally, a short video clip of stomata in action.

The evolution of angiosperms (flowering plants) is a bit contentious these days. Most paleontologists agree that the first definite angiosperm fossil is Cretaceous, but genetic and molecular studies suggest they evolved sometime in the Jurassic. There are disputes over what the fossil record really shows.

Now that you’ve accumulated quite a bit of life’s history, you might appreciate this deep-time clock. I can’t guarantee that all the dates will be correct, but the order of events is good. The main thing you will gain from this page is an appreciation for the scale of geologic time.

Here is a copy of the Fall 2018 second test you took last week. We’ll go over it in class. The average score was 82%, with a high grade of 99%. The breakdown: 90s (10 students), 80s (10 students), 70s (6 students), 60s (2 students), below 60 (3 students).

Merycoidodon skull, left side (Oligocene of Nebraska).

Geology in the News –

The End-Permian Extinction happened much more rapidly than we previously thought. In fact, from this study, it was geologically instantaneous. Life was doing OK until quite suddenly a tipping point was reached to throw it into catastrophe. Implications, people, implications.

The ornithischian dinosaur Pachycephalosaurus may have eaten meat, according to a recent paper. It has been found with sharp front teeth typical of a theropod. I think this is a stretch, though, because some plant eaters have sharp teeth.

A Cretaceous bird in, you guessed it — China, has its lungs preserved as a carbon film. This is a critical piece of evidence for our theories of bird flight.

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Part II of The Evolution of Reptiles; early mammals (October 29 – November 2)

This week we will continue with dinosaurs, so please see the links and prose from last week. We will then explore the development of flying vertebrates, emphasizing pterosaurs. Remember that we have no classes on November 5 and 7 because I am at a meeting of the Geological Society of America in Indianapolis. We may thus start working ahead in lectures this week.

Mammals evolved so gradually from the reptiles that it becomes difficult to say when the first mammal appeared. (A familiar story that you’ve heard with the fish, amphibians, dinosaurs, and “birds”.) The Wikipedia page on the evolution of mammals is quite good, and the related page on the cynodonts (a type of therapsid which includes the mammal ancestors) is useful. We will talk in detail about the various innovations which characterize the mammal-like reptiles and the early mammals. (And we won’t use all the terms in these pages, of course.)

Your second test will be on Friday, November 2. Our review session is on Thursday, November 1, 3:30 – 4:30 p.m. Here are the Fall 2017 second test answers for your study. Your test, of course, will be different. Those student answers are not optimum, just good enough for full credit. As with all sample tests, our current class has covered somewhat different material. Test seating: Students with last names starting with M through Z in Room 205 (our regular room); A-L in Room 216 (across the lobby). Test doors open at 7:50 a.m.; all tests due at 8:50 a.m.

Here again is our Classification of the Phylum Chordata used in this course. It is a list edited just for you. Yes, you do need to know all these names.

Gigandipus, a dinosaur footprint in the Lower Jurassic Moenave Formation at the St. George Dinosaur Discovery Site at Johnson Farm, southwestern Utah.

Geology in the News –

Climate change is producing an insect apocalypse. Many ecosystems have experienced a profound loss of insect diversity and abundance over the past decades. As budding ecologists you know this has many serious knock-on effects, including loss of pollinators and insectivores. My treasured Joshua trees of the Mojave Desert are dying out because their pollinating moths are disappearing.

We’ve known that the Earth’s inner core is solid from calculations and formulae, but now we have direct evidence of its nature. Solid but a bit squishy. And really hot.

Chemists have found a recipe to build all four nucleotides of RNA in a way that could have happened on the surface of the early Earth. This is a biological breakthrough that could show a theoretical pathway to the RNA World. Very cool.

I’ve given you so much bad news this semester about climate change (and we know plenty of other anxieties going on now too!) that you need a set of charts and maps with how much better we have it than our ancestors.

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Jurassic Park, etc.: The Evolution of Reptiles (October 22-26)

This week we return to those wonderful reptiles, finally covering the dinosaurs. As you may imagine, the Web is rich in sites about these beasts. Some of these pages are excellent, some are horrible, most are tolerable (and long). The American Museum of Natural History has an excellent dinosaur website. Their dinosaur facts page is good too. You want YouTube dinosaurs? Click away and spend hours. Other impressive dinosaur websites include that of Paul Sereno, one of the most productive dinosaur paleontologists in the world and virtually an industry to himself. I can vouch for the accuracy, more or less, of the Wikipedia page on dinosaurs. The Dino Directory from the Natural History Museum in London is useful and current. The LiveScience site has the latest dinosaur news.

Your second test will be on Friday, November 2. Our review session is on Thursday, November 1, 3:30 – 4:30 p.m. Here are the Fall 2017 second test answers for your study. Your test, of course, will be different. Those student answers are not optimum, just good enough for full credit. As with all sample tests, our current class has covered somewhat different material. Test seating: Students with last names starting with M through Z in Room 205 (our regular room); A-L in Room 216 (across the lobby). Test doors open at 7:50 a.m.; all tests due at 8:50 a.m.

Here again is our Classification of the Phylum Chordata used in this course. It is a list edited just for you. Yes, you do need to know all these names.

The link to this week’s update on the Permian Extinction.

Girl and dinosaur at the Creation Museum in northern Kentucky. For this to make any sense, you’ll want to read my Wooster Geologists blog entry about our visit. (Click to expand the image.)

Geology in the News –

At least one Cretaceous shark (Squalicorax) ate one pterosaur (Pteranodon) based on a chewed-up wing bone. Must have been quite a scene at the time!

Here’s a provocative new idea: Mesozoic mammals went through a “nocturnal bottleneck” since they were easy prey for dinosaurs during the day. The result of our night-time habits is that we lost a genetic toolkit for repairing our DNA when it is damaged by solar radiation. Thus the headline saying we need sunscreen because of dinosaurs. Interesting.

A terrifying essay on climate change is now making the rounds. Grim, grim, grim. Our leaders have completely failed us on the most important issue in our history.

A scientific fight has developed over the earliest fossils. Structures in Greenland have been interpreted as microbial stromatolites 3.7 billion years old. Now a new study suggests that these features are inorganic, not biological. This would mean the earliest evidence for life returns to 3.5 billion year old stromatolites in Western Australia. Hot words have appeared between the two sides. I think the new study has the best evidence, so I would now say the earliest fossil evidence for life is 3.5 bya.

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Plate Tectonics (October 15-19)

Our primary topic this week is the Theory of Plate Tectonics, with an emphasis on how the dynamic Earth has affected the evolution of life. We can start with this beautiful world map, showing continents, mountains, ridges, transform faults and trenches in the Pacific and Atlantic Oceans. An excellent, world-class site for ancient maps of the evolving Earth is the Paleomap Project. The US Geological Survey has a thorough site called This Dynamic Earth which covers the basics of plate tectonic theory. The University of Texas hosts The Plates Project which concentrates on producing accurate plate reconstructions of the past. Of course, plate tectonics is an ideal subject for web animations. PBS reviews plate tectonic theory with a simple and clear set of images and animations. Here is a global history of continental movement in the last 750 million years from UC Berkeley. This YouTube video on plate tectonics is narrated with a cool Irish accent.

Here, by the way, is a description of the Ordovician fossiliferous marine limestone at the top of Mount Everest. That fact alone shows the incredible dynamic nature of the Earth’s crust.

As for the primary effect of plate tectonics on us, visit the real-time global earthquake website maintained by the U.S. Geological Survey. You will see how very common earthquakes are around the world, and where you do not want to buy a house. PBS has a nice set of animations of earthquakes from a global perspective, along with volcanoes and the geological phenomenon we now know all too well, tsunamis. Here are summary pages on the devastating 2004 tsunami in the Indian Ocean, the January 2010 Haiti Earthquake and the 2011 earthquake and tsunami in Japan. The new page on last month’s terrible tsunami in Indonesia is now available as well. Note that geologists are still debating the origins of the tsunami.

Bristlecone Pine in the White Mountains of eastern California.

Geology in the News –

Here’s a nice summary of the latest ideas on the evolution of modern birds. It appears that the Cretaceous extinctions may have sped up their evolution, primarily by selecting for small body sizes which have higher rates of evolution.

Speaking of bird evolution, here’s that story of the “messy new species” of dinosaur-bird found in China. (This was on the back of your Quiz #5.) “The 127-million-year-old species, which they have named Jinguofortis perplexus, retains other features of its dinosaur ancestors, such as claws on the fingers of its wings, a jaw with tiny teeth rather than a beak, and a fused shoulder girdle. That last trait is seemingly poorly adapted to flight, hence the name perplexus.”

Here’s a strange new dinosaur from the Jurassic of South Africa: Ledumahadi mafube. It “crouched like a cat” and had strangely flexible forelimbs for a 12-ton animal. We are in a golden age of dinosaur paleontology. There are new discoveries every week.

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The Amniotic Egg: Amphibians to Reptiles (October 1-5)

It must be time to really “conquer the land”, as we say too often. Please review the links for last week so you’re up to speed on the amphibians. Their descendants the reptiles are an enormously successful class, and their diversity is reflected in the websites devoted to them. I can only give you links to a few of the many groups we will discuss in class this week. (Just wait until we get to the dinosaurs!) You will want to study the wonders of the amniotic egg. Here’s an introductory page to the turtles, and then another for the diapsids. Everything you want to know about the therapsids (“mammal-like reptiles”) can be found here. The best general reptile page I’ve found is from Heidelberg, Germany. It has many  informative (and richly illustrated) pages in English. I’m sure you’ll also like this mosasaur page from the South Dakota School of Mines and Technology Museum of Geology. (I learned a cool mosasaur story during a visit to The Netherlands.) The Wikipedia pages on plesiosaurs and ichthyosaurs are well done. (If they weren’t, we would fix them!) I enjoy this elaborate Oceans of Kansas site, which concentrates on the Late Cretaceous reptiles of the Western Interior.

An amphibious ancestor to the ichthyosaurs was recently discovered in the Triassic of China. This is big news because prior to this the origin of these elegant marine reptiles was a mystery.

A pivotal event in Mesozoic reptile evolution was the Triassic mass extinction, which is well covered on this webpage from the University of Bristol. The rise of the dinosaurs starts soon after.

Here  is our Classification of the Phylum Chordata used in this course. It is a list edited just for you. Yes, you do need to know all these names. This is the fish evolution diagram we’ve been using in class.

Mosasaur front paddle (Cretaceous); Natural History Museum of Maastricht, The Netherlands.

Geology in the News –

Here is that recent story on Dickinsonia from the Ediacaran found by your classmate Nate. Biomarkers (you remember those) show that it was an animal. This is not a surprising conclusion, but a cool technique.

The Japanese have landed tiny space rovers on an asteroid, and they’re starting to send back images. Postcards from the beginning of our Solar System.

This will not be news to you, but it is a fairly good accounting: What Darwin didn’t know about evolution. There are some nomenclature errors in this popular article, and poor Wallace should have been in the headline too.

Crystals of the hardy mineral zircon are giving us chemical clues about surface conditions on the earliest Earth. Maybe it wasn’t as bad as we’ve thought. There are even hints of life prior to 3.7 billion years ago.

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From Fins to Feet: Early Vertebrate Evolution (September 24-28)

This week we return to the Paleozoic and examine developing marine communities, followed by a discussion of the causes of the Permian Mass Extinctions — the greatest disaster in the History of Life. Paleogeographic maps of Pangaea at the end of the Permian can be found on the Paleomap website (note that it was not “99% of all life” which went extinct). Wikipedia has a good Permian Extinctions article, although the topic is controversial enough that some parts of it may be biased by partisan editors of one cause or another.

The End-Permian Extinction happened much more rapidly than we previously thought. In fact, from this study, it was geologically instantaneous. Life was doing OK until quite suddenly a tipping point was reached to throw it into catastrophe.

Probably on Friday our vertebrate cousins will appear in our narrative. The best place on the Web for simple and thorough descriptions of the chordates and their history is at the University of California Museum of Paleontology. Check out their pages on the urochordates (tunicates), cephalochordates, and chordates in general. The Berkeley tetrapod (four-legged) webpage is especially useful for us. I like this website lovingly devoted to the ancient coelacanth fish Latimeria. It has many illustrations and an extensive history of what we know about this remarkable evolutionary survivor. The Tree of Life page on terrestrial vertebrates will show you current ideas about the relationships of fish and early amphibians. It is a rich source of further links. You might like the short Japanese 3-D animation of Eusthenopteron (an ancient bony fish near the origin of the amphibians) embedded in this link.

Here is a good general page from Wikipedia on amphibians.

Your first test results: The class average was 78%, with a high of 100%. There were 10 tests 90-100%, 10 from 80 to 89%, 6 in the 70s, 3 in the 60s, and 5 below 60%. Well over half the class earned the equivalent of an A or B, which is good. Here are the Fall 2018 student HOL test #1 answers.

A pycnodontid fish tooth, Menuha Formation (Upper Cretaceous), southern Israel. Collected by Andrew Retzler. (Click to enlarge.)

Geology in the News –

You may have heard that mammoths are about to be cloned. Fake news!

Great music video on evo-devo. Starts with hox genes. “This is how we go from single cells to people.” The channel A Capella Science is highly recommended!

Paleontologists are now using neutron scanners to make ultra-high resolution images of vertebrate fossils. Very cool results.

Arctic lakes are now bubbling out massive amounts of the potent greenhouse gas methane. This is not good.

 

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Developing Marine Ecosystems (September 17 & 21)

It is an unusual week for us. We have class on Monday, no class on Wednesday, a review session on Thursday (3:30 – 4:30 pm, Scovel 205). Then your first lecture examination is on Friday. For preparation, I’m giving you a copy of the Fall 2017 student HOL test #1 answers as a pdf. I highly recommend reading it through. The student answers are not necessarily the best, but they were good enough to receive full credit. Also note that there are always topics we covered in the past that we may not have done this semester, and vice versa. You will be tested over only what we have completed in class through Monday, September 17. Test seating: Students with last names starting with A through L in Room 205 (our regular room); M-Z in Room 216 (across the lobby). Test doors open at 7:50 a.m.; all tests due at 8:50 a.m.

Our topic on Monday is the rise of animal life and the early development of marine communities. A good place to start is with the Wikipedia page on the Ediacaran Biota. The Wikipedia pages on all these topics are good and authoritative. Another example is the Cambrian article.

We will spend time on the rise of skeleton-bearing invertebrates in the Cambrian. I hope you enjoy the Burgess Shale (this is the Smithsonian’s main page on it), found in the Middle Cambrian. Here is the Smithsonian’s Burgess Shale reconstructed images page. (I was fortunate to visit the Burgess Shale quarries in British Columbia.) This virtual submarine website from the Royal Ontario Museum has great animated images of the Burgess Shale fauna. A new site of Burgess Shale-type fossils in Kootenay National Park in Canada was announced recently. It may soon rival the original for number and diversity of soft-bodied fossils.

You may enjoy this blog post from the superlative science writer Carl Zimmer on the Cambrian animals. (The illustrations by Quade Paul are stunning.) Zimmer also has a New York Times article on new ideas about “Evolution’s Big Bang” in the Cambrian.

Anomalocaridid “arm” from the Burgess Shale, Walcott Quarry, British Columbia, Canada.

Geology in the News –

Dr. Rick Lehtinen recently named a new frog species after our treasured College of Wooster. This is an honor for Wooster and an accomplishment for Dr. Lehtinen. Guibemantis woosteri is a cute little guy who lives in Madagascar.

Here’s a beautiful map showing streams and rivers of the United States. The watersheds are in separate colors.

Wish we could spend more time with the Kingdom Fungi. Here’s a nice modern summary of their diversity and utility.

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