ATURIA: MIOCENE NAUTILOID

Aturia angustata, Lower Miocene, WA

This lovely Lower Miocene nautiloid is Aturia angustata collected on the foreshore near Clallam Bay, Olympic Peninsula, northwestern Washington. 

Aturia is an extinct genus of Paleocene to Miocene nautiloid within Aturiidae, a monotypic family, established by Campman in 1857 for Aturia (Bronn, 1838), and is included in the superfamily Nautilaceae (Kümmel,  1964).

There are seven living nautiloid species in two genera: Nautilus pompilius, N. macromphalus, N. stenomphalus, N. belauensis, and the three new species being described from Samoa, Fiji, and Vanuatu (Ward et al.). We have specimens of fossil nautiloids dating to the Turonian of California, and possibly the Cenomanian of Australia. There has also been a discovery of what might be the only known fossil of Allonautilus (Ward and Saunders, 1997), from the Nanaimo Group of British Columbia, Canada.

Aturia in the Collection of Rick Ross, VIPS

The exquisite shell preservation of many Nanaimo nautilids has opened up a lens into paleotemperatures and accurate Nitrogen isotope analyses. 

Nautilus and all other known Cretaceous through Paleogene nautiloids were shallow water carnivores. We may see their shells as beautiful bits of art and science today, but they were seen in our ancient oceans as small yet mighty predators. Preferring to dine on shrimp, crab, fish and on occasion, a friendly cousin nautiloid to two.

Aturia lived in cooler water in the Cenozoic, preferring it over the warmer waters chosen by their cousins. Aturia, are commonly found as fossils from Eocene and Miocene outcrops. That record ends with their extinction in the late Miocene. This was a fierce little beast with jaws packed with piranha-like teeth. They grew at least twice that of the largest known Nautilus living today. 

Aturia is characterized by a smooth, highly involute, discoidal shell with a complex suture and subdorsal siphuncle. The shell of Aturia is rounded ventrally and flattened laterally; the dorsum is deeply impressed. The suture is one of the most complex within the subclass Nautiloidea. Of all the nautiloids, he may have been able to go deeper than his brethren.

Nautiloids are known for their simple suturing in comparison to their ammonite cousins. This simplicity of design limited their abilities in terms of withstanding the water pressure experienced when several atmospheres below the sea. Nautiloids were not able to compete with their ammonite cousins in this regard. 

Instead of elaborate and complex sutures capable of withstanding the pressures of the deep, nautiloids have simpler sutures that would have them enfold on themselves and crush at depth.  

Aturia angustata; Rick Ross Collection

It has a broad flattened ventral saddle, narrow pointed lateral lobes, broad rounded lateral saddles, broad lobes on the dorso-umbilical slopes, and a broad dorsal saddle divided by a deep, narrow median lobe. 

The siphuncle is moderate in size and located subdorsally in the adapical dorsal flexure of the septum. Based on the feeding and hunting behaviours of living nautiluses, Aturia most likely preyed upon small fish and crustaceans. 

I've found a few of these specimens along the beaches of Clallam Bay and nearby in a local clay quarry. I've also seen calcified and chalcedony — microcrystalline quartz — agatized beauties of this species collected from river sites within the Olympic Peninsula range. In the bottom photos, you can see Aturia from Washington state and one (on the stand on the left) from Oregon, USA. These beauties are in the collections of the deeply awesome Rick Ross, Vancouver Island Palaeontological Society.

References: Ward, P; Haggart, J; Ross, R; Trask, P; Beard, G; Nautilus and Allonautilus in the Nanaimo Group, and in the modern oceans; 12th British Columbia Paleontological Symposium, 2018, Courtenay, abstracts; 2018 p. 10-11

ATURIA: MIOCENE NAUTILOID

Aturia angustata, Lower Miocene, WA

This lovely Lower Miocene nautiloid is Aturia angustata collected on the foreshore near Clallam Bay, Olympic Peninsula, northwestern Washington. 

Aturia is an extinct genus of Paleocene to Miocene nautiloid within Aturiidae, a monotypic family, established by Campman in 1857 for Aturia (Bronn, 1838), and is included in the superfamily Nautilaceae (Kümmel,  1964).

There are seven living nautiloid species in two genera: Nautilus pompilius, N. macromphalus, N. stenomphalus, N. belauensis, and the three new species being described from Samoa, Fiji, and Vanuatu (Ward et al.). We have specimens of fossil nautiloids dating to the Turonian of California, and possibly the Cenomanian of Australia. There has also been a discovery of what might be the only known fossil of Allonautilus (Ward and Saunders, 1997), from the Nanaimo Group of British Columbia, Canada.

Aturia in the Collection of Rick Ross, VIPS

The exquisite shell preservation of many Nanaimo nautilids has opened up a lens into paleotemperatures and accurate Nitrogen isotope analyses. 

Nautilus and all other known Cretaceous through Paleogene nautiloids were shallow water carnivores. We may see their shells as beautiful bits of art and science today, but they were seen in our ancient oceans as small yet mighty predators. Preferring to dine on shrimp, crab, fish and on occasion, a friendly cousin nautiloid to two.

Aturia lived in cooler water in the Cenozoic, preferring it over the warmer waters chosen by their cousins. Aturia, are commonly found as fossils from Eocene and Miocene outcrops. That record ends with their extinction in the late Miocene. This was a fierce little beast with jaws packed with piranha-like teeth. They grew at least twice that of the largest known Nautilus living today. 

Aturia is characterized by a smooth, highly involute, discoidal shell with a complex suture and subdorsal siphuncle. The shell of Aturia is rounded ventrally and flattened laterally; the dorsum is deeply impressed. The suture is one of the most complex within the subclass Nautiloidea. Of all the nautiloids, he may have been able to go deeper than his brethren.

Nautiloids are known for their simple suturing in comparison to their ammonite cousins. This simplicity of design limited their abilities in terms of withstanding the water pressure experienced when several atmospheres below the sea. Nautiloids were not able to compete with their ammonite cousins in this regard. 

Instead of elaborate and complex sutures capable of withstanding the pressures of the deep, nautiloids have simpler sutures that would have them enfold on themselves and crush at depth.  

Aturia angustata; Rick Ross Collection

It has a broad flattened ventral saddle, narrow pointed lateral lobes, broad rounded lateral saddles, broad lobes on the dorso-umbilical slopes, and a broad dorsal saddle divided by a deep, narrow median lobe. 

The siphuncle is moderate in size and located subdorsally in the adapical dorsal flexure of the septum. Based on the feeding and hunting behaviours of living nautiluses, Aturia most likely preyed upon small fish and crustaceans. 

I've found a few of these specimens along the beaches of Clallam Bay and nearby in a local clay quarry. I've also seen calcified and chalcedony — microcrystalline quartz — agatized beauties of this species collected from river sites within the Olympic Peninsula range. In the bottom photos, you can see Aturia from Washington state and one (on the stand on the left) from Oregon, USA. These beauties are in the collections of the deeply awesome Rick Ross, Vancouver Island Palaeontological Society.

References: Ward, P; Haggart, J; Ross, R; Trask, P; Beard, G; Nautilus and Allonautilus in the Nanaimo Group, and in the modern oceans; 12th British Columbia Paleontological Symposium, 2018, Courtenay, abstracts; 2018 p. 10-11

FOSSIL FAUNA OF THE OLYMPIC PENINSULA

Vertipecten fucanus (Dall, 1898), Clallam Formation, WA

Some water-worn samples of the fossil bivalve Vertipecten fucanus from Lower Miocene deposits in the Clallam Formation.

These lovelies were collected on the foreshore near Clallam Bay, Olympic Peninsula, northwestern Washington on a lovely fossil field trip I did with my mother years ago.

Range zones of pectinid bivalves provide a principal means of age determination and correlation of shallow-water, inshore facies from California, through to Washington state and up to the head of the Gulf of Alaska.

Until Addicott's study from 1976, the area was considered middle Miocene. The new Lower Miocene designation can be credited in large part to the restricted stratigraphic range of Vertipecten fucanus (Dall, 1898) and the restricted and overlapping ranges of several other fossil mollusks collected from Alaska to California.

Neogene marine sediments of the West Coast of North America were deposited in a series of widely spaced basins that extended geographically from the western and northern Gulf of Alaska (60°N) to southern California (33°N). Rich molluscan faunas occur extensively throughout these deposits and form the basis for biostratigraphic schemes that are useful for correlating within and between individual basins.

Arturia angustata nautiloid, Clallam Formation, WA

Early biostratigraphic work was concerned with faunas from particular horizons and with the stratigraphic range of diverse taxa, such as Pecten and Turritella, without reference to other fossil groups.

Succeeding work increasingly dealt with the relationships of molluscan zones to benthic and, later, planktonic foraminiferal stages. In recent years the age limits of Neogene molluscan stages have become better documented by reference to planktonic microfossils from dated DSDP cores and onshore faunas. As our tools get better, our insight into these faunal groups and their correlation with their cousins to the south and over in the Pacific become clearer.

Neogene molluscan faunas from California, the Pacific Northwest states (Oregon and Washington), and southern Alaska have been treated separately due to differences in faunal composition and geographic isolation. As a result, a different biostratigraphic sequence has been described for each region.

Pacific Northwest stages have been formally named and defined. This naming structure is also used informally for Alaskan faunas. California Neogene stages were proposed early in this century, are in need of redescription, and their usage is informal. Precise correlations between the three regional sequences have not yet been achieved, due to the low number of co-occurring species and the general lack of planktonic microfossils in these largely shallow-water faunas. The objectives of ongoing research include the documentation of the faunas of California and Pacific Northwest stages; formal description of California stages; an improved correlation between regional stage sequences; refinement of age estimates for stage boundaries; and, the establishment of Neogene stages for Alaskan faunas.

FOSSIL SALMON OF SKOKOMISH

This toothy specimen is an Oncorhynchus nerka, a Pleistocene Sockeye Salmon from outcrops along the South Fork Skokomish River, Olympic Peninsula, Washington State, USA.

The area is home to the Skokomish — one of nine tribes of the Twana, Coast Salish First Nations in the northern-mid Puget Sound area of western Washington state in the United States. 

Each of the Tribal Nations are known by their locations — Dabop, Quilcene or salt-water people, Dosewallips, Duckabush, Hoodsport, Skokomish or Skoko'bsh, Vance Creek, Tahuya, and Duhlelap or Tule'lalap. The name Skokomish means river people or people of the river in the language of the Twana, sqʷuqʷóbəš or sqWuqWu'b3sH.

Closer to my home farther north in the Pacific Northwest on northern Vancouver Island are the Kwakiutl or Kwakwaka'wakw, speakers of Kwak'wala. Here, sockeye salmon are known as ma̱łik. You would likely recognize these fossils' modern counterparts from their distinctive red bodies and greenish heads. 

Their descendants had been absent from the Skokomish River for more than a decade up to 2014 when construction to augment the negative impact of the Cushman Reservoir was undertaken to restore their natural habitat.

The fossil specimens include individuals with enlarged breeding teeth and worn caudal fins. It is likely that these salmon acted very similar to their modern counterparts with males partaking in competitive and sneaky tactics to gain access to the sexiest (large and red) females who were ready to mate. These ancient salmon had migrated, dug their nests, spawned and defended their eggs prior to their death. For now, we're referring to the species found here as Oncorhynchus nerka, as they have many of the characteristics of sockeye salmon, but also several minor traits of the Pink Salmon, Oncorhynchus gorbuscha.

I had expected to learn that the locality contained a single or just a few partial specimens, but the fossils beds are abundant with large, 45–70 cm, four-year-old adult salmon concentrated in a beautiful sequence of death assemblages.

Oncorhynchus nerka, Pleistocene Sockeye Salmon

Gerald Smith, a retired University of Michigan professor was shown the specimens and recognized them as Pleistocene, a time when the northern part of North America was undergoing a series of glacial advances and retreats that carved their distinctive signature into the Pacific Northwest.

It looks as though this population diverged from the original species about one million years ago, possibly when the salmon were deposited at the head of a proglacial lake impounded by the Salmon Springs advancement of a great glacier known as the Puget lobe of the Cordilleran Ice Sheet. 

Around 17,000 years ago, this 3,000 foot-thick hunk of glacial ice had made its way down from Canada, sculpting a path south and pushing its way between the Cascade and Olympic Mountains. The ice touched down as far south as Olympia, stilled for a few hundred years, then began to melt.

After the ice began melting and retreating north, the landscape slowly changed —  both the land and sea levels rising — and great freshwater lakes forming in the lowlands filled with glacial waters from the melting ice. The sea levels rose quite considerably, about one and a half centimetres per year between 18,000 and 13,000 years ago. The isostatic rebound (rising) of the land rose even higher with an elevation gain of about ten centimetres per year from 16,000 to 12,500 years ago.

Around 14,900 years ago, sea levels had risen to a point where the salty waters of Puget Sound began to slowly fill the lowlands. Both the land and sea continued to rise and by 5,000 years ago, the sea level was about just over 3 meters lower than it is today. The years following were an interesting time in the geologic history of the Pacific Northwest. The geology of the South Fork Skokomish River continued to shift, undergoing a complicated series of glacial damming and river diversions after these salmon remains were deposited.

Today, we find their remains near the head of a former glacial lake at an elevation of 115 metres on land owned by the Green Diamond Company. The first fossil specimens were found back in 2001 by locals fishing for trout along the South Fork Skokomish River.

Upon seeing the fossil specimens, Smith teamed up with David Montgomery of the University of Washington, Seattle, along with N. Phil Peterson and Bruce Crowley, a Late Oligocene Mysticete specialist from the Burke Museum, to complete fieldwork and author a paper.

The fossil specimen you see here is housed in the Burke Museum collection. They opened the doors to their new building and exhibitions in the Fall of 2019. These photos are by the deeply awesome John Fam from a trip to see the newly opened exhibits this year. If you fancy a visit to the Burke Museum, check out their website here: https://www.burkemuseum.org/.

David B. Williams did up a nice piece on historylink.org on the Salmon of the Puget lowland. You can find his work here: https://www.historylink.org/File/20263

If you'd like to read more of the papers on the topic, check out:

• Smith, G., Montgomery, D., Peterson, N., and Crowley, B. (2007). Spawning sockeye salmon fossils in Pleistocene lake beds of Skokomish Valley, Washington. Quaternary Research, 68(2), 227-238. doi:10.1016/j.yqres.2007.03.007.
• Easterbrook, D.J., Briggs, N.D., Westgate, J.A., and Gorton, M.P. (1981). Age of the Salmon Springs Glaciation in Washington. Geology 9, 87–93.
• Hikita, T. (1962). Ecological and morphological studies of the genus Oncorhynchus (Salmonidae) with particular consideration on phylogeny. Scientific Reports of the Hokkaido Salmon Hatchery 17, 1–97.

If you fancy a read of Crowley's work on Late Oligocene Mysticete from Washington State, you can check out:  Crowley, B., & Barnes, L. (1996). A New Late Oligocene Mysticete from Washington State. The Paleontological Society Special Publications, 8, 90-90. doi:10.1017/S2475262200000927

ARTURIA OF THE PACIFIC

This lovely Lower Miocene nautiloid is Aturia angustata collected on the foreshore near Clallam Bay, Olympic Peninsula, northwestern Washington. 

I have been exploring Washington State for many years. It is rugged, windswept and has amazing fossil exposures all along its northern edge. The area goes by the name of the Olympic Peninsula and it is a wilderness playground. The sites I usually visit are Majestic Beach for its rare but prized fossil whale bone.

Further west are the beach exposures that have fossil echinoids in matrix and Ghost shrimp claws in concretion. There is a clay mine that holds wonderful nautiloids like the creamy Aturia you see here. Sometimes they are cemented together and come out whole. Sometimes calcified and show yellow, brown and white when you hold them to the light. Further up are the beach exposures along Clallam Bay.

Aturia is an extinct genus of Paleocene to Miocene nautilids within Aturiidae, a monotypic family, established by Campman in 1857 for Aturia Bronn, 1838, and is included in the superfamily Nautilaceae in Kümmel, 1964.

Aturia is characterized by a smooth, highly involute, discoidal shell with a complex suture and subdorsal siphuncle. 

Their shells are rounded ventrally and flattened laterally; the dorsum is deeply impressed. The suture is one of the most complex within Nautiloidea. It has a broad flattened ventral saddle, narrow pointed lateral lobes, broad rounded lateral saddles, broad lobes on the dorso-umbilical slopes, and a broad dorsal saddle divided by a deep, narrow median lobe. 

The siphuncle is moderate in size and located subdorsally in the adapical dorsal flexure of the septum. Based on the feeding and hunting behaviours of living nautiluses, Aturia most likely preyed upon small fish and crustaceans. It is well worth exploring the exposures at Clallam Bay. The local clay quarry is on private land so you would need to seek permission. I have also seen calcified beauties of this species collected from river sites within the Olympic Peninsula range, though I have not explored these myself.