Sunday, 31 January 2021

SOOKE FOSSIL BIRDS: PENGUINS AND CORMORANTS

Stemec suntokum, a Fossil Plopterid from Sooke, British Columbia
The upper Oligocene Sooke Formation that outcrops on southwestern Vancouver Island, British Columbia is a wonderful place to collect and especially good for families.

As well as amazing west coast scenery, the beach site outcrop has a lovely soft matrix with well-preserved fossil molluscs, often with the shell material preserved (Clark and Arnold, 1923).

While the site has been known since the 1890s, my first trip here was in the early 1990s as part of a Vancouver Paleontological Society (VanPS) fossil field trip.

By the Oligocene ocean temperatures had cooled to near modern levels and the taxa preserved here as fossils bear a strong resemblance to those found living beneath the Strait of Juan de Fuca today. Gastropods, bivalves, echinoids, coral, chitin and limpets are common-ish — and on rare occasions, fossil marine mammals, cetacean and bird bones are discovered.

Back in 2015, a family found the fossilized bones from a 25-million-year-old wing-propelled flightless diving bird while out strolling the shoreline near Sooke. Not knowing what they'd found but recognizing it as significant, the bones were brought to the Royal British Columbia Museum to identify.

The bones found their way into the hands of Gary Kaiser. Kaiser worked as a biologist for Environment Canada and the Nature Conservatory of Canada. After retirement, he turned his eye from our extant avian friends to their fossil lineage. The thing about passion is it never retires. Gary is now a research associate with the Royal British Columbia Museum, published author and continues his research on birds and their paleontological past.

Kaiser identified the well-preserved coracoid bones as the first example from Canada of a Plotopteridae, an extinct family that lived in the North Pacific from the late Eocene to the early Miocene. In honour of our First Nations communities who settled the Sooke area, Kaiser named the new genus and species Stemec suntokum.

Magellanic Penguin Chick, Spheniscus magellanicus
This is a very special find. Avian fossils from the Sooke Formation are rare. We are especially lucky that the bird bone was fossilized at all.  These are delicate bones and tasty. Scavengers often get to them well before they have a chance and the right conditions to fossilize.

Doubly lucky is that the find was of a coracoid, a bone from the shoulder that provides information on how this bird moved and dove through the water similar to a penguin. It's the wee bit that flexes as the bird moves his wing up and down.

Picture a penguin doing a little waddle and flapping their flipper-like wings getting ready to hop near and dive into the water. Now imagine them expertly porpoising —  gracefully jumping out of the sea and zigzagging through the ocean to avoid predators. It is likely that the Sooke find did some if not all of these activities.

When preservation conditions are kind and we are lucky enough to find the forelimbs of our plotopterid friends, their bones tell us that these water birds used wing-propelled propulsion to move through the water similar to penguins (Hasegawa et al., 1979; Olson and Hasegawa, 1979, 1996; Olson, 1980; Kimura et al., 1998; Mayr, 2005; Sakurai et al., 2008; Dyke et al., 2011).

Kaiser published on the find, along with Junya Watanabe, and Marji Johns. Their work: "A new member of the family Plotopteridae (Aves) from the late Oligocene of British Columbia, Canada," can be found in the November 2015 edition of Palaeontologia Electronica. If you fancy a read, I've included the link below.

The paper shares insights into what we've learned from the coracoid bone from the holotype Stemec suntokum specimen. It has an unusually narrow, conical shaft, much more gracile than the broad, flattened coracoids of other avian groups. This observation has led some to question if it is, in fact, a proto-cormorant of some kind. We'll need to find more of their fossilized lineage to make any additional comparisons.

Sooke, British Columbia Shoreline
Today, fossils from these flightless birds have been found outcrops in the United States and Japan (Olson and Hasegawa, 1996). They are bigger than the Sooke specimens, often growing up to two metres.

While we'll never know for sure, the wee fellow from the Sooke Formation was likely about a 50-65 cm long and weighed in around 1.72-2.2 kg — so roughly the length of a duck and weight of a small Magellanic Penguin, Spheniscus magellanicus, chick. To give you a visual, I've included a photo of one of these cuties here showing off his full range of motion and calling common in so many young.

The first fossil described as a Plotopteridae was from a wee piece of the omal end of a coracoid from Oligocene outcrops of the Pyramid Hill Sand Member, Jewett Sand Formation of California (LACM 8927). Hildegarde Howard (1969) an American avian palaeontologist described it as Plotopterum joaquinensis. Hildegarde also did some fine work in the La Brea Tar Pits, particularly her work on the Rancho La Brea eagles.

In 1894, a portion of a pelagornithid tarsometatarsus, a lower leg bone from Cyphornis magnus (Cope, 1894) was found in Carmanah Group on southwestern Vancouver Island (Wetmore, 1928) and is now in the collections of the National Museum of Canada as P-189401/6323. This is the wee bone we find in the lower leg of birds and some dinosaurs. We also see this same bony feature in our Heterodontosauridae, a family of early and adorably tiny ornithischian dinosaurs — a lovely example of parallel evolution.

Fossil coquina, Photo: John Fam
While rare, more bird bones have been found in the Sooke Formation over the past decade. In 2013, three avian bones were found in a single year. The first two were identified as possibly being from a cormorant and tentatively identified as Phalacrocoracidae tibiotarsi, the large bone between the femur and the tarsometatarsus in the leg of a bird.

They are now in the collections of the Royal BC Museum as (RBCM.EH2013.033.0001.001 and RBCM.EH2013.035.0001.001). These bones do have the look of our extant cormorant friends but the specimens themselves were not very well-preserved so a positive ID is tricky.

The third (and clearly not last) bone, is a well-preserved coracoid bone now in the collection at the RBCM as (RBCM.EH2014.032.0001.001).

Along with these rare bird bones, the Paleogene sedimentary deposits of the Carmanah Group on southwestern Vancouver Island have a wonderful diversity of delicate fossil molluscs (Clark and Arnold, 1923). Walking along the beach, look for boulders with white shelly material in them. You'll want to collect from the large fossiliferous blocks and avoid the cliffs. The lines of fossils you see in those cliffs tell the story of deposition along a strandline. Collecting from them is both unsafe and poor form as it disturbs nearby neighbours and is discouraged.

Sooke Formation Gastropods, Photo: John Fam
We find nearshore and intertidal genera such as Mytilus (mussels) and barnacles, as well as more typically subtidal predatory globular moon snails (my personal favourite), surf clams (Spisula, Macoma), and thin, flattened Tellin clams.

The preservation here formed masses of shell coquinas that cemented together but are easily worked with a hammer and chisel. Remember your eye protection and I'd choose wellies or rubber boots over runners or hikers.

You may be especially lucky on your day out. Look for the larger fossil bones of marine mammals and whales that lived along the North American Pacific Coast in the Early Oligocene (Chattian).

Concretions and coquinas on the beach have yielded desmostylid, an extinct herbivorous marine mammal, Cornwallius sookensis (Cornwall, 1922) and 40 cm. skull of a cetacean Chonecetus sookensis (Russell, 1968), and a funnel whale, a primitive ancestor of our Baleen whales. A partial lower jaw and molar possibly from a large, bear-like beach-dwelling carnivore, Kolponomos, was also found here. A lovely skull from a specimen of Kolponomos clallamensis (Stirton, 1960) was found 60 km southwest across the Strait of Juan de Fuca in the early Miocene Clallam Formation and published by Lawrence Barnes and James Goedert. That specimen now calls the Natural History Museum of Los Angeles County home and is in their collections as #131148.

Directions: From the town of Sooke west of Victoria, follow Highway 14 for about 14 kilometres. Just past the spot where the highway crosses Muir Creek, you will see a gravel parking area on your left. Pull in and park here. From the barrier, walk out to the beach and turn right (west) and walk until you see the low yellow-brown sandstone cliffs about 400 metres ahead. Look at the boulders on the beach. Check for low tide before heading out and choose rubber boots for this beach adventure.

References: L. S. Russell. 1968. A new cetacean from the Oligocene Sooke Formation of Vancouver Island, British Colombia. Canadian Journal of Earth Science 5:929-933
Barnes, Lawrence & Goedert, James. (1996). Marine vertebrate palaeontology on the Olympic Peninsula. Washington Geology, 24(3):17-25.

Fancy a read? Here's the link to Gary Kaiser's paper: https://palaeo-electronica.org/content/2015/1359-plotopterid-in-canada. If you'd like to head to the beach site, head to: 48.4°N 123.9°W, paleo-coordinates 48.0°N 115.0°W.