Monday Mammal #6: The Gorilla

Since gorillas seem to be popular lately, (see my recent post, this one from Laelaps and here in the news) I had little choice but to feature them as this week's Monday Mammal.  Below, I'll first introduce the different gorilla species (yes, there are more than one!) then cover where they fall in the list of our closest primate relatives.

Figure 1. Adult male gorilla, Denver Zoo, 2009

 

Figure 2. Hand of a female gorilla, napping at the Denver Zoo.
While I doubt gorillas have ever wished they had our hairless, 
fragile bodies I'm have to be suffering with major thumb envy!

Gorillas are comprised of two species

Amazing Story from Gorilla School

A brief "must watch" video of a Damian Aspinall's visit with a western lowland gorilla (G. g. gorilla) which he helped raise and reintroduce to the wild.  The video is part of the Animal Planet series Gorilla School. 

"Damian Aspinall's Extraordinary Gorilla Encounter on Gorilla School"

More about donating to help support gorilla conservation can be found at the Aspinall Foundation website, here or from other organizations such as the International Gorilla Conservation Programme, the Dian Fossey Gorilla Fund, and the Mountain Gorilla Conservation Fund.

[Hat tip to Dr. Tom]

Evolution at the zoo

I just saw this post over at the Axis of Evo blog, and remembered a photo I took of a sign at the Denver Zoo on primate evolution... which included humans.  The photo was taken in early July, 2009 in front of the gorilla exhibit.

Figure 1. The sign.

First, I think it's fantastic that the Denver Zoo isn't being shy, and is trying to educate the public about where our species sits in the tree of life -- especially in relation to the (other) great apes.  I've seen lesser zoos completely devoid of such efforts.

That said, there were some problems with the sign:  It depicted an outdated relationship between humans and other apes, and it looked as though someone was trying to sugar coat those human-to-primate relationships further by including extinct groups that (conveniently?) introduce extra space between humans and the other primates.  In any case, I think the sign needs an update...  Here's a closer look at the bottom panel -- their presentation of the major modern primate lineages plus one extinct group...

Figure 2. The bottom panel from the sign in Figure 1.

I could be wrong here, but last I recall all the evidence suggests this picture (excluding the extinct "ape-men") should look something more like this:

Figure 3.  An edited (or maybe, corrected?) version of the sign above.

Only a few feet away, should any visitor get curious, were nice close looks at Gorillas and Orangutans.  I was able to snap this picture...

Figure 4. Hand of a female gorilla, napping a few feet away from the sign above.

Perhaps not as impressive as the big silver-back, but it does nicely illustrate how some of our human features maybe aren't as exclusively human as some like to think.

A Dinosaur on the Christmas Dinner Table

If you recall my post from back around Thanksgiving, the Wild Turkey -- like all birds -- is a modern day dinosaur.  What better opportunity to share this little fact with your friends and family than over the Christmas Turkey?

Below are some resources for turning the remains of your holiday feast into a biology lesson, but before we get into details I want to first answer a simple question: What exactly is a dinosaur anyway?

Dinosaur's are a group of (mostly extinct) reptiles that arose around the early Triassic period about 230 million years ago (mya).  They persisted until the mass extinction event that occurred 65mya at the end of the Cretaceous period, (also the end of the Mesozoic era and start of the Cenozoic era), when all of the dinosaur lineages save modern birds died out.

To put this talk of dinosaurs and birds into perspective, lets take a crash course in vertebrate taxonomy. Starting with the ancestor of all land vertebrates, we can follow evolution forward to the present, noting major points of divergence along the way.  We're of course skipping a lot, taking the fast track from the first vertebrate land animals to modern day birds.

The first amphibian-like terrestrial tetrapods appeared over 350mya (Late Devonian into the Carboniferous period), with the Synapsids (whose descendants became the modern mammals) splitting off 25+ million years later.  Another 25 million years or so later, ancestral turtles and other Testudines appeared, then the sphenodonts (the tuatara) and the squamates (lizards and snakes), then crocodilians, then dinosaurs and birds.

These relationships can be summarized as follows (here I've included proper group names as well as extant representatives):

•  Amniotes - Descendants of the first egg-laying terrestrial vertebrates (~ 340mya) split around ~325mya
• Synapsids - Mammalian ancestors
• ...
• Mammals ~ 200 mya
• Primates ~ 55+ mya
• Human-Chimp Split ~ 5-10 mya
• Saurapsids - Modern Reptilians
• Anapsids - Turtles
• Diapsids - Other modern reptiles (including birds), split ~ 300mya
• Lepidosauria -Tuatara, Lizards and Snakes
• Sphenodonts - Tuatara
• Squamates - Lizards, Snakes
• Archosauria - Crocodilians, Dinosaurs (including birds)
• Crocodilia
• Dinosauria - Two dinosaur groups diverged ~250 mya
• Ornithischia - "bird-hipped", beaked - but not birds!
• Saurischia - "lizard-hipped", toothed ancestors of birds.
• Sauropodomorpha - big herbivores like Diplodicus.
• Theropoda - bipedal carnivores like T. rex, Velociraptor and...
• Aves - modern birds, originating ~ 150mya

Whew!  So to sum up, birds have been around since their divergence from the other dinosaurs during the Cretaceous period (145-65mya), and are the only surviving Dinosaurs of the big Cretaceous extinction 65mya. Their closest living relatives are the Crocodilians (together with dinosaurs and other relatives, these are the Archosaurs), then the lizards and snakes (which all together form the Diapsid reptilians), then turtles (all together, the Saurapsids). After all the reptilians, the next closest relatives are the mammals (all together, these are all of the living Amniotes), then amphibians, fishes, etc.

So how do you bring all this information to the dinner table?  Well the easiest way to see the relationship between dinosaurs and birds is from the differences and similarities in their skeletal structure.

Source: The Origin and Early Evolution of Birds | Geology Rocks

Other ideas can be found here, and for a nice reference you can bring with you to the Christmas dinner table...

Source: Image from here, modified by Tom Holtz here.

Resources:

---

1. Prothero, S. 2007. Evolution: What the Fossils Say and Why It Matters. Columbia Univ. Press.
2. The Dinosauria, from the University of California Museum of Paleontology website.
3. Wikipedia (links above).
4. Wedel, Matt. Your Holiday Dinosaur, University of California Museum of Paleontology website.
5. Holtz, Tom. Your Thanksgiving/Christmas Therapod from Dave Hone's Archosaur Musings.

Signs of Evolution in Primate Teeth

I've been busy with thesis work lately, but I'll try and get back to regular posts after the holidays! 

For now, here's a nice little clip on primate evolution, which I came across on the YouTube channel for the U.S. National Institute of Standards and Technology (yes, they have one!).

I'll let Dr. Constantino explain...