Field of Science

Phytosaur Skull Excavation

Awhile back some of our park neighbors alerted us to a specimen weathering out in outcrops of the Sonsela Member of the Chinle Formation. Matt Brown checked it out and identified it as a phytosaur skull. Last week we braved an incoming storm to document the site and check out the specimen. In this photo Jeff Martz is taking notes on the site. This specimen is important because of its stratigraphic position, just below what we believe is the Jasper Forest bed, and based on this should represent a "Leptosuchus".

As you can see the specimen is weathering out along its entire length. The matrix is a muddy, poorly sorted sandstone, crystalline and very hard in some places, and easily friable in others. This will make for a challenging excavation.


Although at first glance the specimen looks like just a scatter of weathered fragments, closer examination (below) shows that it is a phytosaur skull. The specimen is lying with its ventral surface exposed. Unfortunately much of the ventral surface has fragmented and much is missing; however, the upper portion of the skull, including the all important squamosals, should be present. We believe that the rostrum may be gone but cannot say for sure without further excavation.

The bottom photo shows where we left off on our first day (2 hours) at the site. We have picked up much of the float outside of the skull perimeter and consolidated loose pieces that are nearly in place. About six or seven centimeters down the matrix gets really hard. Looks to be a three or four day job.
I will be posting our progress with this specimen regularily mainly because the landowners, who have generously donated the specimen, will be away and thus can follow the excavation here. Of course I hope that my readers will also find this of interest.

5 comments:

  1. Someone needs a grant for a gas-powered rock saw!

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  2. Someone has a gas-powered rock saw, and I'm surprised that Matt and/or Jeff haven't been chomping at the bit to use it! Keep me posted on this skull; hopefully it turns out that most of it is there and that you can get some of the float fragments back together.

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  3. Fascinating! thanks for the play by play. Looking forward to following the excavation as it progresses.

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  4. Heh. Looking at all the fragments on the surface made me say "Eugh." Genus Explodosuchus?

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