word
A comforting hug.
I love it when I can start my Secular Thursday off with a story about dinosaurs. Scientists have discovered multiple 243 million year old Asilisaurus skeletons*, enough to assemble a complete skeleton. If you want to get technical, this Labrador-sized creature (which lived during the middle Triassic period) is a silesaur, another member of the clade dinosauriform, so more like a cousin to the guys we call dinosaurs. Still, dinosaurs and silesaurs existed simultaneously, springing from a common ancestor, so if silesaurs existed earlier than originally thought (by about 10 million years, by scientist’s estimations), their dinosaur cousins likely did, as well.
Now, “clade” is a fun word. It refers to a branch on the tree of life and includes the ancestor and all of its descendants. Cladistics is one way of studying/classifying the diversification of life of Earth through looking at evolutionary relation. The diagram demonstrating cladistics is called a cladogram, and it’s pretty nifty-keen in that it can show the origins and derivations of pretty much everything, or at least everything related, neatly laid out so that you can see what came likely from where (or who) based on shared derived characteristics.
Cladograms don’t indicate how much time has passed, just the relation between species, which makes it a useful tool in demonstrating evolutionary concepts to children. Explaining evolution to (especially younger) children can be tricky, in my experience, because children’s understanding of time is fairly limited. Trying to conceptualize time relations between species and understand tiny changes over millions of years is confusing to a kid who still think of his years in halves. Cladograms just show the probable order of speciation, like a family tree, which kids don’t seem to have a problem understanding.
If you want to look at something really cool (though now out of date, because science…always updating and changing as we develop better tools and find more clues!), you should take a look at this dinosaur cladogram completed in 2001. The way this tool can be useful for your kids isn’t because it has an up-to-date degree of accuracy (too many discoveries sticking other creatures in between the ones list), but because it does provide an interesting visual way to track how creatures change over time. The simple dino silhouettes will probably much a lot more sense that a text-only “family tree” of evolution, plus, what kid doesn’t love dinosaurs (probably some kids, but mine aren’t among them)?
If you’d like to read more about the Asilisaurus, you might enjoy one of the articles from Discover magazine or Wired. I’m sure you want to read more about this herbivorous lap dog of the Triassic period!
Nice looking guy, isn’t he?
*Sterling J. Nesbitt, Christian A. Sidor, Randall B. Irmis, Kenneth D. Angielczyk, Roger M. H. Smith & Linda A. Tsuji. “Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira” Nature 464, 95-98 (4 March 2010) | doi:10.1038/nature08718; Received 16 September 2009; Accepted 1 December 2009
