Sunday, November 12, 2017

The first fossils described from Dinosaur National Monument

The first fossils described from Dinosaur National Monument (to the best of my knowledge) were not dinosaurian. They weren't vertebrate. They weren't from the Morrison Formation. They weren't from the Jurassic, or even the Mesozoic. You may not realize it, but the monument has a geologic record extending from the Neoproterozoic to the Quaternary (see for example Untermann and Untermann 1954, Gregson et al. 2010, or Santuci and Kirkland 2010). For this bit of history, we're also going back in geologic time.

Echo Park, at the confluence of the Green and Yampa rivers (NPS/Jacob W. Frank). Why this landmark? Read on!

Let's backtrack just for a moment. People have been finding fossils in what is now Dinosaur National Monument for a long, long time. For example, archeological digs in the monument and the vicinity show that people of the Fremont culture were picking up pieces of petrified wood and various marine invertebrate fossils, such as crinoid stems, mollusk shells, and guards of the Jurassic belemnite Pachyteuthis (Breternitz 1970). The first collection made for scientific purposes appears to have been made by none other than John Wesley Powell and company.

Powell made two trips through the area, during the famous 1869 expedition on the Green and Colorado rivers and the 1871–1872 follow-up expedition. Although the exploits through the Grand Canyon are best-remembered, the expeditions covered quite a bit of land, from Green River, Wyoming, to the Virgin River in Nevada. A portion of the Green River leg is within Dinosaur National Monument: the monument is shaped a bit like an inverted T, with the Green River acting as the approximate axis for the north and west legs. Traveling through this part of the modern monument in 1869, Powell and company gave names to many features, including the Gates of Lodore, Echo Park, Island Park, and Split Mountain.

Split Mountain with snow (NPS/Jake Frank). I think November is getting to me.

Among the specimens collected on these expeditions were fossils, particularly invertebrate fossils, which were important for biostratigraphy and correlation. A catalog in the official geological report (White 1876) shows that some substantial collections were made at various stops. (A fair number of fossils were pulled from the confluence of the Colorado [=Grand] and Green rivers, today smack in the middle of Canyonlands National Park.) Three locations are of particular interest for us today: Echo Park, Island Park, and Split Mountain, all of which are within Dinosaur National Monument today. Several taxa were reported from the "Lower Aubrey Group" of Echo Park and Split Mountain, among them the sponge Chaetetes milleporaceus, tabulate coral Acervularia, bryozoans Fenestella and Archimedes, several species of brachiopods, and the trilobite Phillipsia. The "Upper Aubrey" yielded a species of Bellerophon from Echo Park, and Jurassic bivalves were found at Island Park. These were all only mentioned in passing, though. The first fossil species to actually be described from what becomes the monument is...

A rugose coral, Amplexus zaphrentiformis White 1876 (p. 107–108).

Amplexus zaphrentiformis in White (1880; plate 33, figure 1a); this is the specimen selected as the lectotype in Sando (1965)

75 years later (Sando 1965, plate 2). All but figures 1 and 2 are the lectotype, with arrows on 3 pointing to various sectioning locations.

Powell's expedition collected the group of specimens that White described from the "Lower Aubrey Group" at Echo Park and Split Mountain Canyon. As it turns out, they collected quite a few: White (1876) observed "nearly one hundred examples", and Sando (1965), who redescribed the species, found 102. This gives us the enjoyable image of the explorers taking an hour or two to fill their bags with horn corals, like any of us might do today at a good spot. Sando (1965), working from two original syntype lots (41 specimens cataloged in 1879 as USNM 8064 and 61 specimens cataloged in 1906 as USNM 35696), separated the large specimen illustrated in White (1880) and designated it the lectotype (renumbered USNM 144776), with the other specimens becoming paralectotypes (except for two specimens of other rugose coral genera). He also moved the species to a different genus and emended the spelling, producing Barytichisma zaphrentiforme. Based on geography and the old labels included with the specimens, Sando attributed the fossils to the middle Morgan Formation (Atokan?, Middle Pennsylvanian) about a mile above Echo Park and suggested that none of the fossils in the collection were from Split Mountain, although he also noted that a recent collection from the Morgan Formation at Split Mountain included examples of B. zaphrentiforme that were virtually identical to the original specimens in preservation and matrix. I saw the lectotype a few years ago, which, as the figure from Sando (1965) indicates, was sectioned for detailed study, although a cast was made of the specimen before sectioning. There's a photo in our recent publication on NPS fossil taxa types (in Figure 4).

[2017/11/12 (evening): The opening paragraph initially featured present tense ("are" instead of "were"). There was a reason for this, but on further review the result looked strange.]


Breternitz, D. A. 1970. Archaeological excavations in Dinosaur National Monument, Colorado-Utah, 1964-1965. University of Colorado Press, Boulder, Colorado. University of Colorado Studies, Series in Anthropology 17.

Gregson, J. D., D. Chure, and D. A. Sprinkel. 2010. Geology and paleontology of Dinosaur National Monument, Utah-Colorado. Pages 161–192 in D. A. Sprinkel, T. C. Chidsey, Jr., and P. B. Anderson, editors. Geology of Utah’s parks and monuments (3rd edition). Utah Geological Association, Salt Lake City, Utah. Publication 28.

Sando, W. J. 1965. Revision of some Paleozoic coral species from the western United States. U.S. Geological Survey, Washington, D.C. Professional Paper 503-E.

Santucci, V. L. and J. I. Kirkland. 2010. An overview of National Park Service paleontological resources from the Parks and Monuments in Utah. Pages 589–623 in Sprinkel, D. A., T. C. Chidsey, Jr., and P. B. Anderson, editors. Geology of Utah’s parks and monuments (3rd edition). Utah Geological Association, Salt Lake City, Utah. Publication 28.

Untermann, G. E. and B. R. Untermann. 1954. Geology of Dinosaur National Monument and vicinity, Utah-Colorado. Utah Geological and Mineralogical Survey, Salt Lake City, Utah. Bulletin 42.

White, C. A. 1876. Invertebrate paleontology of the Plateau province, together with notice of a few species from localities beyond its limits in Colorado. Pages 74-135 in Powell, J. W. Report on the geology of the eastern portion of the Uinta Mountains and a region of country adjacent thereto. U.S. Geological and Geographical Survey of the Territories, Government Printing Office, Washington, D.C.

White, C. A. 1880. Contributions to invertebrate paleontology no. 6: Certain Carboniferous fossils from the western states and territories. U.S. Geological and Geographical Survey of the Territories Annual Report 12, part 1 (1883, advance printing 1880):119–141, plates 33-36.

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