In the Field: week 1

I spent the last week in the painted desert, particularly the Chilne and Kayenta formations, of Arizona, about 50 miles north of Flagstaff. It's awesome! The whole of the Chilne formation in this area seems to be a petrified forest. There are large trees in situ and fragments of petrified wood everwhere. It did however take me a few days to find any bone material and it's rather difficult for me to tell where the boundary between the Chilne and the Kayenta formations actually occurs, so I'm not always sure if I'm in the upper Triassic or lower Jurassic. Two of the days without finding bone don't entirely count. On one day I was asaulted by a sand storm that kept me pent up in my van most of the day¹ and on another I spent without success while trying to find a known bonebed in the Kayenta formation². The last couple of days however have been a great success, wherein I've found one in situ partial skeleton that I've begun excavating and one microvertebrate site from which I've recovered over 20 vertebrae, several partial ribs and four teeth as well as several whole and countless fragmentary osteoderms³. I can't be sure, but I think that most of the material that I've found belonged to a group of large plant eating reptiles called Aetosaurs. However, it is just as possible that the osteoderms that I'm finding belong to one of the other archosaurs that were alive at the time.
My most significant discovery so far however is of a piece of petrified wood from a tree sized lycopod, which I think might be stigmaria or a very worn down lepidodentron. I didn't bring my paleobotony notes with me, so it's difficult to say. The reason that this is significant is that this group of plants is thought to have died out completely by the middle permian. The fact that I found this in either late Triassic or early Jurassic rocks means that the group lasted more than 60 million years longer than previously thought and in fact survived a mass extinction that killed off more than 90% of all life on earth at the end of the Permian!

1. Two things learned that day were: A. never try to brush your teeth during a sand storm. B. Aviator sunglasses are not an adequate substitute for safety goggles when going for a walk in a sand storm.

2. The site was 10 km east of my camp site and consiquentially meant that by the time I got there I only had an hour of prospecting before I had to turn around and go back. I still didn't get back until after dark. While descending a hill in the dark I fell and hurt my right knee; something that's slowed me down every day since. Bad show all around.

3. If you don't know what an osteoderm is, think of the armor plates on the back of an alligator or crocodile. They're modified scales with a bony center. Unfortunately, just about everybody in the triassic had them, making them unhelpful for identification purposes.