More Triassic Repeat Photography - Ned Colbert (AMNH) at the Petrified Forest in 1946

In 1946 the American Museum of Natural History initiated fieldwork in the Chinle Formation of Arizona. Led by Edwin (Ned) Colbert, the goal of the expedition was to add to our knowledge of Triassic vertebrates and expand the museum's collection of Chinle Formation fossils. The previous year Colbert had travelled to the Petrified Forest with Charles L. Camp to check out Camp's old localities from the 1920s. This lead to a full blown, successful field season in 1946 (several amazing stories from this work can be found in one of Colbert's autobiographies - Digging into the Past). Set to return in 1947, Colbert never made it because on the way to the Petrified Forest he stumbled upon the huge deposit of vertebrates at the Coelophysis Quarry at Ghost Ranch, New Mexico. As a side note: he did return to the park briefly in 1947 to take part in the first ever Society of Vertebrate Paleontology field conference (see Camp et al., 1947; Nesbitt and Parker, 2005).

Fantastically, Colbert shot many rolls of Kodachrome (color) slide film of his Triassic work in 1946 and 1947. The 1946 set was purchased by the Petrified Forest shortly afterwards and some of these are still in the collections to this day. Since 2001 I have been actively trying to relocate two of the sites, the first a large bed of fresh water clams that AMNH staff proclaimed the greatest deposit of Triassic freshwater clams (Unionids) ever! Actually dozens of these sites occur throughout the park but when first discovered this was a big deal.

1946 shot of AMNH jeep parked near clam bed.

2009 photo of same site

The second site was where Colbert and crew collected the skull of a pseudopalatine phytosaur. This site was particularly intriguing as in the photo the outcrop being excavated looks very much like strata of the Blue Mesa Member. If this site really is in the Blue Mesa Member, this would represent a very low occurrence of a pseudopalatine phytosaur.

1946 photo of phytosaur skull excavation.

2009 photo of same site.

The park also has a very old map where Charles Camp's localities as well as those of National Park staff had been plotted. Colbert's 1946 sites were added to this map. Unfortunately, numerous visits to where these two sites were plotted failed to match up the photographs. By 2009 I had eliminated all possibilities except for one area of badlands south of a place called Billing's Gap. This past summer the interns and I were finally able to precisely relocate these sites. Interestingly both were situated very close to each other geographically and over 1.5 miles away from where they had been mapped! Also of interest was that the sites were in the upper portion of the Sonsela Member, thus no low occurrence of a pseudopalatine.

How fortunate we are that past researchers such as Colbert photographed their work (and he did it in color in 1946!). Even with dots on a map (and GPS coordinates) photos are indispensable for relocating sites and determining stratigraphic position of historic specimens. Nowadays with digital photography, there is no excuse for researchers not to photodocument every single site where fossils are collected.

For those interested in historic documentation of paleontology I encourage you to please check out the 2005 article I did with Sterling Nesbitt for a SVP field trip that year. It includes many previously unpublished photos from the 1947 field conference which was attended by notable VP'ers such as Romer, Gregory, Simpson, Colbert, etc... You can order the entire volume (with papers on the vertebrate faunas and plants of the Moenkopi and Chinle Formations from the Arizona Museum of Natural History.

REFERENCES

Camp, C.L., Colbert, E.H., McKee, E.D., and S.P. Welles. 1947. A guide to the continental Triassic of Northern Arizona. Plateau 20:1-8.

Nesbitt, S.J., and W.G. Parker. 2005. The 1947 Society of Vertebrate Paleontology Triassic fieldtrip, then and now, and its significance to Triassic vertebrate paleontology. Mesa Southwest Museum Bulletin 9:1-12.