The Little Dinosaurs of Ghost Ranch
Edwin Harris Colbert

A handy litttle volume on Coelophysis, the late Triassic dinosaur that is one of the earlier dinosaurs for which we have complete skeletons. Numerous complete skeletons, actually, because a mass die-off a little over two hundred million years ago was preserved in a bed of the Rock Point Formation near Ghost Ranch, New Mexico. Colbert was one of the discoverers, who more or less chanced upon the bed while staying briefly at Ghost Ranch on the way to the Painted Desert. It seems he had, at great trouble, obtained permits to prospect for dinosaurs in the Painted Desert. However, some interesting fossils had been found around Ghost Ranch, and he decided to check out the area briefly as he passed through. The bed he discovered turned out to be one of the most spectacular of dinosaur fossil finds, and he ended up apologizing to the Department of the Interior for not showing up in Arizona because he thought the Ghost Ranch find was more important. They were okay with it, actually, as was his university for spending their research funds somewhere other than expected. It was 1942; different world.

The book has a bit of the feel of an old man’s memoirs, possibly because it is more or less an old man’s memoirs. Nevertheless, it has some nice descriptions of the geologic formations of the Ghost Ranch area, and concludes that the fossils were in beds that should be assigned to the upper Chinle Formation, though he mentions the possible assignment to the Rock Point Formation (which is what younger geologists seem to prefer.) The beds were located in silt under what looks like an old river channel; possibly the dinosaur carcasses were buried in a flood event, though he notes evidence that the carcasses underwent some dessication before deep burial, such as heads bent clear back over their pelvises, presumably from shrinking ligaments.

There’s some good description of how dinosaurs were quarried and prepared back then. Lots of shellac, plaster of Paris, and burlap, with branches cut from nearby juniper trees as splints. I can sympathize. It’s a pretty interesting problem: How do you extract an 8-ton slab of not very strong siltstone with very delicate dinosaur bones embedded, and get it intact to the East Coast? Then prepare it for display in a museum?

There is a chapter that describes the skeleton of Coelophysis in a fair amount of detail. The brain was relatively large for a dinosaur, and the anatomy was clearly build for speed. Not surprising given that these little fellows had to deal with the big lumbering amphibians that dominated the Triassic. Well, not exactly amphibians; tetrapods of distinct lineage from any modern forms.

Another chapter talks about the environment, which was apparently tropical fluvial plain with some high ground. Early seed plants, including conifers, dominated, but there were still some tree ferns.

The quarry is no longer there; it has more or less been washed out and/or buried under more sediments eroded from above. Presumably all the good stuff was extracted first. Other spectacular quarries have been found in the area; Colbert doesn’t write about these, but it’s worth noting that some have been deliberately buried to preserve the remaining fossils while the preparation folks catch up on the ones already quarried.

Cross-posted at Debunkers.org

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