Showing posts with label miocene. Show all posts
Showing posts with label miocene. Show all posts

Saturday, January 20, 2024

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

Thursday, May 26, 2022

SALMON: FRESH, DRIED, BOILED, STEAMED... AND FOSSILIZED

Salmon permeate First Nations mythology and have been a prized food source for thousands of years — fresh, dried, boiled, steamed or smoked — the bones carefully returned to the river or sea to continue the lifecycle of these immortal beings. 

In the Kwak'wala language of the Kwakiutl First Nations of the Pacific Northwest — or Kwakwaka'wakw, speakers of Kwak'wala — sockeye salmon are known as ma̱łik

For the Tk'emlúps te Secwépemc First Nation, people of the confluence, of the Interior of British Columbia, near Kamloops, salmon was the most important of the local fishing stock and the salmon fishing season was a significant social event that warranted the nomination of a Salmon Chief who directed the construction of the hooks, weirs and traps and the distribution of the catch.

In the Interior of the province, archaeological evidence dates the use of salmon as a food source back a mere 3,500 years. While the First Nation groups have an oral history telling us they have lived here since always, 3,500 years falls short of the mark. 

The truth, it seems, needed to be teased from the rock. Sheri Burton and Catherine Carlson were able to isolate and amplify mitochondrial DNA from the salmon remains at archaeological sites near Kamloops. The DNA came from the species as Oncorhynchus nerka or Sockeye salmon, preserved in concretion and collected along the southern shores of Kamloops Lake.

The concretions were originally dated as Miocene (24 – 5.5 million years old) by the Geological Survey of Canada, based on pollen grain analysis. However, many local experts, including UBC geology professor W.R. (Ted) Danner (my mentor), W.H. Mathews and Richard Hughes, suspected the remains were much more recent, perhaps the Late Pleistocene. It was a topic that provided lively debate for many years and much pounding on tables during dinner. But it was not until the early 1990s that Catherine Carlson and Ken Klein found definitive proof of this.

Oncorhynchus nerka
By good luck, the fish remains in the Kamloops Lake concretions had not been completely replaced by minerals — enough of the original organic bone collagen remained for radiocarbon dating. 

For those on either side of the debate, the results were startling — 18,000 years. It is likely that erosion during the time of deposition had carried pollen down from Miocene layers in surrounding hills, to be deposited around the dead fish, causing the initial over-estimation of the age of the concretions.

This lovely specimen is Oncorhynchus nerka, a Late Pleistocene Fossil Sockeye Salmon, from the fine-grained, silty clays on the south shore of Kamloops Lake, British Columbia, Canada. The site was originally collected in the 1970s by the late geologist and palaeontologist Richard Hughes. I was introduced to the site much later after its rediscovery by Catherine Carlson and Kenneth Klein in the fall of 1991 with the help of local and gracious host, Bill Huxley.

They later wrote up and published a chapter in Rolf Ludvigsen's "Life in Stone: A Natural History of British Columbia's Fossils." It was Huxley who shared its location with John Leahy — a local Kamloops resident and avid fossil hunter — and him with me. 

This specimen was collected by John in the 1990s, his tenth partial salmon from this site and the sole one in my collection.

An age of 18,000 plus years sets the fossils firmly as the only salmonids of the Late Pleistocene in North America, a very significant find. The date also changed our ideas about the early climate of the Interior; the Thompson Valley could not have been covered by glacial ice for as long as originally thought. Indeed, it makes the Interior ice-free only 2,000 years after the Last Glacial Maximum and some 4,000 years before our western continental coastline and the Rocky Mountain Foothills.  

It has long been accepted that the most recent series of ice ages began approximately 1.6 million years ago, beginning as ice accumulations at higher altitudes with the gradual cooling of the climate. Four times the ice advanced and receded, most recently melting away somewhere around 10,000 years ago. Ice retreated from southwestern British Columbia and the Puget Sound area around 15,000 years ago. 

In the southern Interior, ice built up first in the northern Selkirk Mountains, then slowly flowed down into the valleys. Once the valleys were filled, the depth of the ice increased until it began to climb to the highlands and finally covered most of the Interior of British Columbia. Between ice advances, there were times when the Kamloops area was ice-free and the climate warm and hospitable. 

Glacial ice was believed to have initiated its most recent retreat from the South Thompson area around 11,000 to 12,000 years ago, but salmon remains from 18,000 years ago suggest that it may have actually begun its northwest decline much earlier — and presenting the possibility of a much warmer climate in the Interior than archaeologists or geologists had originally thought.

Eighteen thousand-year-old salmon also challenge the archaeological notion that the First Nation people of the Interior have had access to salmon as a significant protein source for only a few thousand years. 

In the popular view, people living in the Okanagan and Thompson Valleys were felt to have moved to settlements that were semi-permanent about 4,500 years ago. By that time they would have had a seasonally regulated diet composed primarily of salmon and supplemented by local game — deer, elk, small mammals — and available shellfish, birds and plant foods, roots and berries. If salmon were present much earlier, it is possible that this pattern of food utilization may have arisen earlier than thought.

Richard Hughes had originally identified the fossilized Kamloops salmon as Oncorhynchus nerka or Sockeye salmon, the same species found in the 3,500-year-old archaeological sites. But, using the carbon-13 isotope ratio, Klein and Carlson were able to determine that these salmon did not feed on protein from a marine source and relied solely on a freshwater diet. 

In other words, they could not have spent part of their life in the ocean, as modern Sockeye salmon do. Based on the specimens’ smaller heads and stunted bodies, the longest measuring in at a pint-sized 11.5 cm, Klein and Carlson feel that the fossils are likely Kokanee — a modern landlocked variety of Sockeye.

If you are wondering about the traditional First Nation use of salmon, this McGill University link is outstanding:http://traditionalanimalfoods.org/fish/searun-fish/page.aspx?id=6446


Wednesday, January 19, 2022

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.