Sunday, February 2, 2014

Metro mammoths

Many states have had inventories published of Pleistocene mammal finds; I'm putting together a file for a future post. The most recent such report for Minnesota was complied by Clinton R. Stauffer and published sometime in the late 1940s. It is often cited as Stauffer 1945, but he cites several finds from 1946 and 1948. The journal is a proceedings volume for 1945, which is where the usual date comes from, but the Minnesota Academy of Sciences must have had some trouble getting it out that year. Anyway, 1945, 1948, the immediate point is that it's been a while.

In a place like Minnesota, which has been largely covered with more than a recommended geologic serving of glacial debris, finding fossils of large Pleistocene mammals involves a lot of luck. It's not like, say, the Platteville Formation, which has a limited surface extent and is fossiliferous almost anywhere it is present. I don't think any of the specimens reported by Stauffer were found by someone looking for them; instead, they were recovered in the course of other work, like farming, building construction, road work, gravel quarrying, and dredging. Under such conditions, reporting has been haphazard. The sequence of events that has given us our record of Ice Age finds is a bit like the Drake equation, only with large extinct mammals instead of alien civilzations. First, the fossil has to be noticed. Second, the person at the scene has to do something about it: pick it up and take it home, make some sort of note, take a picture, etc. Third, the report has to make it to someone in a position to keep track of it, scientifically. Fourth, this person has to report the find. This chain can easily fail. At the first step, it is entirely possible for someone to miss a fossil, especially while using large pieces of earth-moving equipment. The second and third steps can be short-circuited by a lack of interest, by a distrust of authority ("if I show a scientist my mammoth tooth, they'll just take it away"), or fearing that if someone is told, work will be stopped to investigate. At the fourth step, there isn't a lot of scientific incentive to publicize or publish isolated finds of single teeth and bones, unless it's unusual for some reason (first example of "X" in an area, some kind of interesting pathology, etc.). It might end up in an internal list somewhere, but actual publication probably would have to wait for someone doing an inventory of that animal, or something along those lines. Thus, you can imagine that any accounting is going to be short a significant number of finds.

So, where have Pleistocene mammals been found in the metro? We covered the giant beavers in a previous entry. Everything else known to Stauffer belonged to a proboscidean (the group including mastodons, mammoths, gomphotheres, modern elephants, and some other things), mostly mammoths. Mammoth taxonomy is "one of those things", and it is not within the scope of this humble blog post to provide a comprehensive review. Suffice it to say the following: Stauffer used three genera and species: Mammonteus primigenius, Parelephas jeffersoni, and Archidiskodon imperator. The first is the woolly mammoth (Mammuthus primigenius) and the other two are now generally considered synonyms of the Columbian mammoth (Mammuthus columbi), which you may know as the star of the Mammoth Site of Hot Springs, South Dakota, and also as the ancestor of the famous pygmy mammoths of the California Channel Islands. Stauffer also reported mastodons, but only in counties outside of the metro. Incidentally, if you're curious, it is quite obvious if you have a mammoth or a mastodon if you have a tooth: mammoth teeth have a washboard-like grinding surface, whereas mastodon teeth have prominent cusps. Six metro counties (Anoka, Dakota, Hennepin, Ramsey, Scott, and Washington) are represented in Stauffer's list by 21 specimens, mostly teeth. See if your neighborhood had elephants:

*Stauffer #20: a tooth and tusk attributed to "P. jeffersoni?" from "the east bank of the Mississippi River along Coon Creek at Fridley", 1878.

*Stauffer #11: a molar tooth attributed to "P. jeffersoni" from glacial gravel near Hastings, undated.
*Stauffer #34: a partial tusk found at the Chicago, Milwaukee, and St. Paul Railway gravel pit near Farmington, 1910.
*Stauffer #42: the head of a femur found in Mississippi River terrace gravels at Hastings. Stauffer reports that this find dates to 1923, and that the bone was given to the Minnesota Historical Society by "Judge Crosby". Provided he meant Francis Marion Crosby, Stauffer seems to have made an error; Crosby died in 1910, and it is doubtful that the prospect of reporting and donating a partial mammoth fossil has ever induced the dead to walk the earth. I checked with the Historical Society and found they had a record for a bone found in gravel near Hastings in March 1909, which fits much better with Crosby's chronology. Unfortunately, the specimen had been lost.
*Stauffer #66: a shoulder blade from a highway gravel pit at Rich Valley Corners south of Inver Grove Heights, 1931; it is now UMPC 4050 in the collections of the University of Minnesota.
*Stauffer #87: a molar attributed to "A. imperator" from a gravel pit at a farm in Rosemount, 1940; it is now UMPC 5890 in the collections of the University of Minnesota.
*Stauffer #97: a tusk fragment from a gravel pit a few miles northwest of Empire City, 1942; it is now UMPC 5936 in the collections of the University of Minnesota.
*Stauffer #98: a molar attributed to "P. jeffersoni?" from the same pit as #97, 1942.

*Stauffer #3: a molar tooth found in drift in Minneapolis, undated.
*Stauffer #13: a molar tooth attributed to "P. jeffersoni" from glacial gravel in Minneapolis, undated; sent to the Peabody Museum of Natural History (Yale) (perhaps YPM 11679, collected in 1895).
*Stauffer #15: a molar tooth attributed to "A. imperator" from a gravel pit in St. Louis Park, undated; sent to the University of Minnesota.
*Stauffer #29: various bones (perhaps most of a skeleton originally) from the Minneapolis and St. Louis Railway car shops, Cedar Lake, 1892; a femur from this find was donated to the University of Minnesota (UMPC 1351).
*Stauffer #33: "a pelvis, femur, and eight vertebra[e] dredged from the bottom of Lake Minnetonka in 30 feet of water, 100 feet off Huntington Point", 1908.
*Stauffer #76: a partial skeleton discovered but not excavated below a city street intersection in Robbinsdale, 1935.
*Stauffer #82: a molar attributed to "P. jeffersoni?" from beach sands at St. Albans Bay, Lake Minnetonka, 1939; it was unearthed after a tree uprooted in a storm.
*Stauffer #99: a molar attributed to "M. primigenius" from gravel near Glenwood Park during construction of the Floyd B. Olson Memorial Highway segment of Minnesota State Highway 55, 1942.

*Stauffer #45: a fragmentary molar attributed to "M. primigenius" dredged from the Mississippi River at St. Paul, 1924; it is now UMPC 3257 in the collections of the University of Minnesota.

*Stauffer #51: a tooth attributed to "P. jeffersoni" from gravel below Main Street of Belle Plaine, 1926.

*Stauffer #6: a tusk from terrace gravels somewhere on the outskirts of Stillwater, undated.
*Stauffer #17: several tusks discovered during excavation in Stillwater, 1856; sent to the "Academy at St. Paul". I have no idea who would have them now.
*Stauffer #64: a molar attributed to "M. primigenius" from a gravel pit two miles below the Hudson bridge near Lakeland, 1931.

The conclusions I draw are that it helps to have access to a gravel pit or Lake Minnetonka.

The map from Stauffer "1945". Note how sparse finds are north of the Minnesota River and west of the Twin Cities; a combination of glaciation (keeping the mammals out, destroying their remains) and low population (fewer people to find fossils) is probably responsible.

Stauffer, C. R. "1945". Some Pleistocene mammalian inhabitants of Minnesota. Minnesota Academy of Science Proceedings 13:20–43.

No comments:

Post a Comment