The Amniotic Egg: Amphibians to Reptiles (October 2-6)

The sixth week already. 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 trimmed 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 –

Another important lesson from genetic research: physical appearance does not always track evolutionary relationships. The example here is the genetic heritage of living nautiloids. Turns out even in this relatively small group we thought we understood, there is plenty of evolutionary convergence going on.

Here’s a cool video of the Earth’s surface evolution projected over the next 250 million years. The Wilson Cycle continues!

Giant wombats (that alone should bring some clicks) apparently had mass migrations in Australia during the Pleistocene. The clues to these journeys are carbon isotopes found in their fossilized teeth.

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