Fossil Marine Mammals of the National Park Service

This year it works out that I'm a little early for the annual "Fossil [Group] of the National Park Service", and we continue our tour of mammal groups with a bit of a grab-bag. As with the marine reptiles, there is not one single group of marine mammals. Rather, several different groups became adapted to the oceans. There are the cetaceans, including whales, dolphins, and porpoises (and yes, dolphins and porpoises are small whales, but you know what I mean). There are the pinnipeds, including animals such as seals, sea lions, and walruses (and yes, there are two distinct groups of pinnipeds called seals, true seals without ears and eared seals that are closer to sea lions; it wouldn't be an Equatorial Minnesota post without mentioning at least a couple of caveats and technicalities, after all). Finally, we also have sirenians (dugongs and manatees) and desmostylians (extinct, kind of hippo-like things), two herbivorous groups that may or may not have been related.

This time we're dealing with a compact group of parks, 14 in all. No doubt this will come as a great surprise, but all of these occurrences of marine mammals are in coastal states. The only examples where a modern saltwater body is not practically within sight are a few where the coastline has wandered elsewhere sometime during the Neogene. The cetaceans have the most records, but there isn't a huge spread between the groups, and there is a lot of overlap. Six park units are represented by two of the groups, two (Point Reyes National Seashore and Santa Monica Mountains National Recreation Area) are represented by three, and Channel Islands National Park has fossils of all four (see Tweet et al. 2020 for details on that one; it's also got fossils of sea otters). Interestingly, it's more common for a park to have two or more groups than it is to have just one, as only five are singletons.

Map time! 1. Point Reyes National Seashore; 2. Golden Gate National Recreation Area; 3. Channel Islands National Park; 4. Santa Monica NRA; 5. Bering Land Bridge National Preserve; 6. Vicksburg National Military Park; 7. Gateway NRA; 8. Suitland Parkway; 9. George Washington Birthplace National Monument; 10. Colonial National Historical Park; 11. Assateague Island NS; 12. Fort Monroe NM; 13. Cape Hatteras NS; 14. Cumberland Island NS.

Cetaceans

Eleven NPS units have records of fossil cetaceans. The records are scattered from the Oligocene to the Quaternary, rather than being heavily biased to the Quaternary like we have in a lot of these mammal posts. We get close to the famous Eocene Basilosaurus with Natchez Trace Parkway but just miss. The potential Oligocene records are scrap from Oligocene–Miocene units at Channel Islands and Santa Monica Mountains. The Miocene is more interesting. Out on the East Coast several parks have records of cetaceans in the Calvert Formation (Fort Monroe National Monument, George Washington Birthplace National Monument, Suitland Parkway). The Fort Monroe record is one of the well finds and was pulled up from 574 feet down, so the potential for further finds is a bit muted. George Washington Birthplace, of course, is noted for cetacean fossils (Tweet and Santucci 2024). The Suitland record is from a site no longer in Suitland; the fossils were found during construction of the Branch Avenue Metro station in 1997, and included a partial skull of a baleen whale and a portion of a vertebra of a toothed whale (and a dugong rib fragment). Meanwhile, on the West Coast, Point Reyes has fossils from a diversity of Miocene cetaceans in several formations, including the type specimen of Parabalaenoptera baulinensis Zeigler et al., 1997 from the Miocene–Pliocene Santa Cruz Mudstone. Nearby Golden Gate National Recreation Area also has cetaceans in the Purisima Formation (Boessenecker 2013). Miocene cetacean scrap is known from Channel Islands and Santa Monica Mountains. The Pliocene, short as it is, gets some Miocene overlap, as well as cetacean bones in the Yorktown Formation of Colonial National Historical Park (Chriscoe et al. 2020). Quaternary remains have been found at Bering Land Bridge National Preserve and (again) Channel Islands (although also scrappy, again). Displaced cetacean fossils of undetermined age have been found at Cumberland Island National Seashore and Gateway National Recreation Area.

Pinnipeds

Pinnipeds have definitely been found at seven parks, with more equivocal reports at two others. I'd imagine the walrus records are particularly interesting given their much more limited geographic range today. Four parks have confirmed walrus records. One is Bering Land Bridge, which probably doesn't seem especially surprising, but there are also fossil records at several parks with nary a modern walrus: Cape Hatteras National Seashore (Stover 2002), Gateway (Stoffer 2003), and Golden Gate (Repenning and Tedford 1977). Interestingly, the three parks whose pinniped records do not include walruses have sea lions (Channel Islands, Point Reyes, and Santa Monica Mountains). Apparently you can have one or the other, but not both. Seal fossils (eared or earless) are present at Bering Land Bridge, Channel Islands, Gateway, and Point Reyes, which is the source of the type specimen of the Miocene eared seal Thalassoleon macnallyae Repenning and Tedford, 1977.

The Cape Hatteras walrus skull, from Stover (2002).

Of the equivocal records, Assateague Island National Seashore has a jaw attributed to a sea lion in collections, which would be rather interesting on biogeographic grounds (sea lions not being noted for their presence in the North Atlantic) (Tweet et al. 2014). Maybe it's a walrus instead? The record from Colonial seems more likely just based on what we know of where people were collecting, but is not airtight. It consists of the type specimen of the walrus Prorosmarus alleni Berry and Gregory, 1906, now considered a synonym of Ontocetus emmonsi, collected from Yorktown.

The type material of Prorosmarus alleni, from Berry and Gregory (1906).

Sirenians

Four parks have confirmed records of sirenians: Channel Islands, Point Reyes, Santa Monica Mountains, and Suitland Parkway. There is also one record of possible manatee ribs from the Early Oligocene of the Vicksburg area that may have come from Vicksburg National Military Park (and if you don't know about the fossils there, check out Rich et al. 2023). The Channel Islands record is a new undescribed species from the Early Miocene (Paces et al. 2023). The best place for sirenian diversity is Point Reyes, where three successive formations (Santa Margarita Sandstone, Santa Cruz Mudstone, and Purisima Formation) have yielded material of three taxa (Dusisiren jordani, Dusisiren dewana, and Hydrodamalis sp., in stratigraphic order) (Domning 1978; Pearson et al. 2016). The other two parks have scrappy material.

Ribs of the Santa Rosa Island sirenian, from my article on Park Paleontology News.

Desmostylians

We've only got one solid record of desmostylians in the NPS, and it comes from Channel Islands, where a partial skull and vertebrae from the Monterey Formation on Santa Cruz Island represent a new species (Tweet et al. 2020). Also worth noting is Ounalashkastylus tomidai, based on material found on Unalaska Island (Chiba et al. 2016) just outside of NPS-affiliated Aleutian World War II National Historic Area.

References

Berry, E. W., and W. K. Gregory. 1906. Prorosmarus alleni, a new genus and species of walrus from the Upper Miocene of Yorktown, Virginia. American Journal of Science (Series 4) 21: 444–450.

Boessenecker, R. W. 2013. A new marine vertebrate assemblage from the Late Neogene Purisima Formation in central California, part II: pinnipeds and cetaceans. Geodiversitas 35(4): 815–940. doi: 10.5252/g2013n4a5.

Chiba, K., A. R. Fiorillo, L. L. Jacobs, Y. Kimura, Y. Kobayashi, N. Kohno, Y. Nishida, M. J. Polcyn, and K. Tanaka. 2016. A new desmostylian mammal from Unalaska (USA) and the robust Sanjussen jaw from Hokkaido (Japan), with comments on feeding in derived desmostylids. Historical Biology 28 (1–2): 289–303. doi: 10.1080/08912963.2015.1046718.

Chriscoe, M., R. Lockwood, J. S. Tweet, and V. L. Santucci. 2022. Colonial National Historical Park: Paleontological resource inventory (public version). National Park Service, Fort Collins, Colorado. Natural Resource Report NPS/COLO/NRR—2022/2361. doi: 10.36967/nrr-2291851.

Domning, D. P. 1978. Sirenian evolution in the North Pacific Ocean. University of California Publications in Geological Sciences 118.

Paces, J. B., S. A. Minor, K. M. Schmidt, and J. Hoffman. 2023. Strontium isotope chronostratigraphic age of a sirenian fossil site on Santa Rosa Island, Channel Islands National Park, California. U.S. Geological Survey, Reston, Virginia. Scientific Investigations Report 2023–5026. doi: 10.3133/sir20235026.

Pearson, L. K., E. C., Clites, V. L. Santucci and R. W. Boessenecker. 2016. Protocols for paleontological site monitoring at Point Reyes National Seashore. National Park Service, Fort Collins, Colorado. Natural Resource Report NPS/NRSS/NRR—2016/1185.

Repenning, C. A. and R. H. Tedford. 1977. Otarioid seals of the Neogene. U.S. Geological Survey, Washington, D.C. Professional Paper 992. doi: https://doi.org/10.3133/pp992.

Rich, M. M., C. V. Beightol, C. C. Visaggi, J. S. Tweet, and V. L. Santucci. 2023. Vicksburg National Military Park: Paleontological resource inventory (public version). National Park Service, Fort Collins, Colorado. Natural Resource Report NPS/VICK/NRR—2023/2516. doi: https://doi.org/10.36967/2299268.

Stoffer, P. 2003. Geology of the New York City region: a preliminary regional field-trip guidebook.U.S. Geological Survey, Reston, Virginia.

Stover, D. 2002. Fossil walrus skull found on the Outer Banks near Cape Hatteras. Park Paleontology 6(2): 2.

Tweet, J. S, and V. L. Santucci. 2024. How protecting shark teeth can lead to finding dolphins: George Washington Birthplace National Monument as a case study in developing and implementing paleontological resource monitoring. Parks Stewardship Forum 40(1): 103–114. doi: http://dx.doi.org/10.5070/P540162925.

Tweet, J. S., V. L. Santucci, and T. Connors. 2014. Paleontological resource inventory and monitoring: Northeast Coastal and Barrier Network. National Park Service, Fort Collins, Colorado. Natural Resource Technical Report NPS/NCBN/NRTR—2014/897.

Tweet, J. S., V. L. Santucci K. Convery, J. Hoffman, and L. Kirn. 2020. Channel Islands National Park: Paleontological resource inventory (public version). National Park Service, Fort Collins, Colorado. Natural Resource Report NPS/CHIS/NRR—2020/2171. doi: https://doi.org/10.36967/nrr-2278664.

Zeigler, C. V., G. L. Chan, and L. G. Barnes. 1997. A new late Miocene balaenopterid whale (Cetacea: Mysticeti), Parabalaenoptera baulinensis (new genus and species), from the Santa Cruz Mudstone, Point Reyes Peninsula, California. Proceedings of the California Academy of Sciences 50(4): 115–138.