The Green River Formation is an Eocene geologic formation that records a 12 million year history of sedimentation in a group of intermountain lakes in three basins along the present-day Green River in Colorado, Wyoming, and Utah. It is one of the most important outcrops we have for insight into life in the Eocene. It gives a window into what our world looked like about 50 million years ago.
Wednesday, July 17, 2024
HETEROPTERA: SNEAKOPTERA
The Green River Formation is an Eocene geologic formation that records a 12 million year history of sedimentation in a group of intermountain lakes in three basins along the present-day Green River in Colorado, Wyoming, and Utah. It is one of the most important outcrops we have for insight into life in the Eocene. It gives a window into what our world looked like about 50 million years ago.
BUMBLEBEES: FOSSILS AND FIRST NATIONS
My Norwegian cousins on my mother's side call them humle. Norway is a wonderful place to be something wild as the wild places have not been disturbed by our hands.
There are an impressive thirty-five species of bumblebee species that call Norway hjem (home), and one, Bombus consobrinus, boasts the longest tongue that they use to feast solely on Monkshood, genus Aconitum, you may know by the name Wolf's-bane.
In the Kwak̓wala language of the Kwakwaka'wakw, speakers of Kwak'wala, and my family in the Pacific Northwest, bumblebees are known as ha̱mdzalat̕si — though I wonder if this is actually the word for a honey bee, Apis mellifera, as ha̱mdzat̕si is the word for a beehive.
I have a special fondness for all bees and look for them both in the garden and in First Nation art.
Bumblebees' habit of rolling around in flowers gives us a sense that these industrious insects are also playful. In First Nation art they provide levity — comic relief along with their cousins the mosquitoes and wasps — as First Nation dancers wear masks made to mimic their round faces, big round eyes and pointy stingers. A bit of artistic license is taken with their forms as each mask may have up to six stingers. The dancers weave amongst the watchful audience and swoop down to playfully give many of the guests a good, albeit gentle, poke.
Honey bees actually do a little dance when they get back to the nest with news of an exciting new place to forage — truly they do. Bumblebees do not do a wee bee dance when they come home pleased with themselves from a successful foraging mission, but they do rush around excitedly, running to and fro to share their excitement. They are social learners, so this behaviour can signal those heading out to join them as they return to the perfect patch of wildflowers.
Bumblebees are quite passive and usually sting in defence of their nest or if they feel threatened. Female bumblebees can sting several times and live on afterwards — unlike honeybees who hold back on their single sting as its barbs hook in once used and their exit shears it off, marking their demise.They are important buzz pollinators both for our food crops and our wildflowers. Their wings beat at 130 times or more per second, literally shaking the pollen off the flowers with their vibration.
And they truly are busy bees, spending their days fully focused on their work. Bumblebees collect and carry pollen and nectar back to the nest which may be as much as 25% to 75% of their body weight.
And they are courteous — as they harvest each flower, they mark them with a particular scent to help others in their group know that the nectar is gone.
The food they bring back to the nest is eaten to keep the hive healthy but is not used to make honey as each new season's queen bees hibernate over the winter and emerge reinvigorated to seek a new hive each Spring. She will choose a new site, primarily underground depending on the bumblebee species, and then set to work building wax cells for each of her fertilised eggs.
Bumblebees are quite hardy. The plentiful hairs on their bodies are coated in oils that provide them with natural waterproofing. They can also generate more heat than their smaller, slender honey bee cousins, so they remain productive workers in cooler weather.
We see the first bumblebees arise in the fossil record 100 million years ago and diversify alongside the earliest flowering plants. Their evolution is an entangled dance with the pollen and varied array of flowers that colour our world.We have found many wonderful examples within the fossil record, including a rather famous Eocene fossil bee found by a dear friend and naturalist who has left this Earth, Rene Savenye.
His namesake, H. Savenyei, is a lovely fossil halictine bee from Early Eocene deposits near Quilchena, British Columbia — and the first bee body-fossil known from the Okanagan Highlands — and indeed from Canada.
It is a fitting homage, as bees symbolize honesty, playfulness and willingness to serve the community in our local First Nation lore and around the world — something Rene did his whole life.
Tuesday, July 16, 2024
FOSSIL RHINO AND THE GREAT DEPRESSION
We have known about this gem for a long while now. The fossil was discovered by hikers back in 1935 and later cast by the University of California palaeontologists in 1948.
The Dirty Thirties & The Great Depression
These were the Dirty Thirties and those living in Washington state were experiencing the Great Depression along with the rest of the country and the world. Franklin D. Roosevelt was President of the United States, navigating the States away from laissez-faire economics.
Charmingly, Roosevelt would have his good name honoured by this same park in April of 1946, a few years before researchers at Berkeley would rekindle interest in the site.
Both hiking and fossil collecting was a fine answer to these hard economic times and came with all the delights of discovery with no cost for natural entertainment. And so it was that two fossil enthusiast couples were out looking for petrified wood just south of Dry Falls on Blue Lake in Washington State.
While searching the pillow basalt, the Frieles and Peabodys came across a large hole high up in a cave that had the distinctive shape of an upside-down rhinoceros.
This fossil is interesting in all sorts of ways. First, we so rarely see fossils in igneous rocks. As you might suspect, both magma and lava are very hot. Magma, or molten rock, glows a bright red/orange as it simmers at a toasty 700 °C to 1300 °C (or 1300 °F to 2400 °F) beneath the Earth's surface.
A Rhinoceros Frozen in Lava
During the late Miocene and early Pliocene, repeated basaltic lava floods engulfed about 63,000 square miles of the Pacific Northwest over a period of ten to fifteen million years. After these repeated bathings the residual lava accumulated to more than 6,000 feet.
As magma pushes up to the surface becoming lava, it cools to a nice deep black. In the case of our rhino friend, this is how this unlikely fellow became a fossil. Instead of vaporizing his remains, the lava cooled relatively quickly preserving his outline as a trace fossil and remarkably, a few of his teeth, jaw and bones. The lava was eventually buried then waters from the Spokane Floods eroded enough of the overburden to reveal the remains once more.
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| Diceratherium tridactylum (Marsh, 1875) |
While there are likely many more, we have found fossil remains of Diceratherium, an extinct genus of rhinoceros, in the Miocene of Canada in Saskatchewan, China, France, Portugal, Switzerland, and multiple sites in the United States.
He has also been found in the Oligocene of Canada in Saskatchewan, and twenty-five localities in the United States — in Arizona, Colorado, Florida, Nebraska, North Dakota, Oregon, South Dakota, Washington and Wyoming.
Diceratherium was a scansorial insectivore with two horns and a fair bit of girth. He was a chunky fellow, weighing in at about one tonne (or 2,200 lbs). That is about the size of a baby Humpback Whale or a walrus.
Back in the Day: Washington State 15 Million-Years Ago
He roamed a much cooler Washington state some 15 million years ago. Ice dams blocked large waterways in the northern half of the state, creating reservoirs. Floodwaters scoured the eastern side of the state, leaving scablands we still see today. In what would become Idaho, volcanic eruptions pushed through the Snake River, the lava cooling instantly as it burst to the surface in a cloud of steam.
By then, the Cascades had arrived and we had yet to see the volcanic eruptions that would entomb whole forests up near Vantage in the Takama Canyon of Washington state.
Know Before You Go
You are welcome to go see his final resting site beside the lake but it is difficult to reach and comes with its own risks. Head to the north end of Blue Lake in Washington. Take a boat and search for openings in the cliff face. You will know you are in the right place if you see a white "R" a couple hundred feet up inside the cliff. Inside the cave, look for a cache left by those who've explored here before you. Once you find the cache, look straight up. That hole above you is the outline of the rhino.
If you don't relish the thought of basalt caving, you can visit a cast of the rhino at the Burke Museum in Seattle, Washington. They have a great museum and are pretty sporting as they have built the cast sturdy enough for folk to climb inside.
The Burke Museum
The Burke Museum recently underwent a rather massive facelift and has re-opened its doors to the public. You can now explore their collections in the New Burke, a 113,000 sq. ft. building at 4300 15th Ave NE, Seattle, WA 98105, United States. Or visit them virtually, at https://www.burkemuseum.org/
Photo: Robert Bruce Horsfall - https://archive.org/details/ahistorylandmam00scotgoog, Public Domain, https://commons.wikimedia.org/w/index.php?curid=12805514
Reference: Prothero, Donald R. (2005). The Evolution of North American Rhinoceroses. Cambridge University Press. p. 228. ISBN 9780521832403.
Reference: O. C. Marsh. 1875. Notice of new Tertiary mammals, IV. American Journal of Science 9(51):239-250
Lincoln, Roosevelt and Recovery from The Great Depression
Rural Tennessee has electricity for the same reason Southeast Alaska has totem parks. In order to help the nation recover from The Great Depression, President Franklin D. Roosevelt, created a number of federal agencies to put people to work. From 1938-1942 more than 200 Tlingit and Haida men carved totem poles and cleared land for the Civilian Conservation Corps in an effort to create “totem parks” the federal government hoped would draw travelers to Alaska.
This odd intersection of federal relief, Alaska Native art and marketing is the subject of Emily L. Moore’s book “Proud Raven, Panting Wolf: Carving Alaska’s New Deal Totem Parks.”
This effort to bring poles out of abandoned villages includes the Lincoln Pole being moved to Saxman Totem Park by the Civilian Conservation Corps (CCC), who established the Saxman Totem Park in 1938.
The top carving on the Lincoln Pole bears a great likeness of Abraham Lincoln. According to the teachings of many Tlingit elders, this carving was meant to represent the first white man seen in Tlingit territory in the 18th century.
A century later, in the 1880s, one of my ancestors from the Gaanax.ádi Raven clan of the Tongass Tlingit commissioned the pole to commemorate our ancestor's pride to have seen this first white man—which has become a Gaanax.ádi crest—using a photograph of Abraham Lincoln as the model.
It is important not only for these various readings of the crests but also because it claims Gaanax.ádi clan territory before the first Europeans and budding Americans came to these shores—territory that Tlingit carvers who were re-carving the pole in the 1940s were trying to assert to the U.S. government as sovereign land.
Interestingly, another pole in that same park is the Dogfish Pole, carved for Chief Ebbits Andáa, Teikweidi, Valley House. The Chief Ebbits Memorial Pole—the Dogfish Kootéeyaa Pole—was raised in 1892 in Old Tongass Village in honour of a great man, Head Chief of the Tongass and my ancestor. It was then moved, re-carved and re-painted at Saxman Totem Park in 1938 as part of Roosevelt's program—and it due to be re-carved again this year.
It tells the story of his life and the curious way he became Ebbits as he was born Neokoots. He met and traded with some early American fur traders. One of those traders was a Mister Ebbits. The two became friends and sealed that friendship with the exchanging of names.
If you would like to read more about that pole and others, I recommend, The Wolf and the Raven, by anthropologist Viola Garfield and architect Linn Forrest (my talented cousin), published in 1961 and still in print as I ordered a copy for a friend just this year.
Monday, July 15, 2024
HUMPBACK WHALES: MEGAPTERA NOVAENGLIAE
Baleen whales, the mysticetes, split from toothed whales, the Odontoceti, around 34 million years ago. The split allowed our toothless friends to enjoy a new feeding niche and make their way in a sea with limited food resources. There are fifteen species of baleen whales who inhabit all major oceans. Their number include our humbacks, grays, right whales and the massive blue whale. Their territory runs as a wide band running from the Antarctic ice edge to 81°N latitude. These filter feeders
Humpback whales are rorquals, members of the Balaenopteridae family that includes the blue, fin, Bryde's, sei and minke whales. The rorquals are believed to have diverged from the other families of the suborder Mysticeti during the middle Miocene.
It is one of the larger rorqual species, with adults ranging in length from 12–16 m (39–52 ft) and weighing around 25–30 metric tons (28–33 short tons). The humpback has a distinctive body shape, with long pectoral fins and a knobbly head. It is known for breaching and other distinctive surface behaviours, making it popular with whale watchers and the lucky few who see them from the decks of our local ferries.
Both male and female humpback whales vocalize, but only males produce the long, loud, complex "song" for which the species is famous. Males produce a complex soulful song lasting 10 to 20 minutes, which they repeat for hours at a time. I imagine Gregorian Monks vocalizing their chant with each individual melody strengthening and complimenting that of their peers. All the males in a group produce the same song, which differed in each season. Its purpose is not clear, though it may help induce estrus in females and bonding amongst the males.
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| Humpback Whale, Megaptera novaeangliae |
Humpbacks are a friendly species that interact with other cetaceans such as bottlenose dolphins. They are also friendly and oddly protective of humans. You may recall hearing about an incident off the Cook Islands a few years back. Nan Hauser was snorkelling and ran into a tiger shark. Two adult humpback whales rushed to her aid, blocking the shark from reaching her and pushing her back towards the shore. We could learn a thing or two from their kindness. We have not been as good to them as they have been to us.
Like other large whales, the humpback was a tasty and profitable target for the whaling industry. My grandfather and uncle participated in that industry out of Coal Harbour on northern Vancouver Island back in the 1950s. So did many of my First Nation cousins. My cousin John Lyon has told me tales of those days and the slippery stench of that work.
Wednesday, July 10, 2024
NEVADA PALAEONTOLOGY: BERLIN-ICHTHYOSAUR STATE PARK
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| Time Slows at Berlin-Ichthyosaur State Park |
A worn American flag and sun bleached outbuildings greet you on your way to the outcrops. Away from the hustle and bustle that define the rest of Nevada this place feels remarkably serene. Your eyes squint against the sun as you search for ammonoids and other marine fossil fauna while your nose tends to the assault from the bracing smell of sage brush.
This site holds many stories. The interpretive centre displays wonderful marine reptiles, ichthyosaurs in situ, as you might expect from the name of the park — but it also showcases years of history lovingly tended. This stretch of dry golden low hills dappled with the yellow of creosote and desert grasses is an important locality for our understanding of the Carnian-Norian boundary (CNB) in North America.
The area is known worldwide as one of the most important ichthyosaur Fossil-Lagerstätte because of the sheer volume of remarkably well-preserved, fully articulated (all the sweet bones laid out all in a row...) specimens of Shonisaurus popularis.
Rich ammonoid faunas outcrop in the barren hills of the Upper Triassic (Early Norian, Kerri zone), Luning Formation, West Union Canyon, Nevada. They were studied by N. J. Silberling (1959) and provide support for the definition of the Schucherti and Macrolobatus zones of the latest Carnian — which are here overlain by well-preserved faunas of the earliest Norian Kerri Zone.
The genus Gonionotites, very common in the Tethys and British Columbia, is for the moment, unknown in Nevada. The Upper Carnian faunas are dominated by Tropitidae, while Juvavitidae are conspicuously lacking.
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| Middle Triassic Ammonoids |
October is an ideal time to do fieldwork in this area. There are a few good weeks between screaming hot and frigid cold. It is also tarantula breeding season so keep your eyes peeled. Those sweet little burrows you see are not from rodents but rather largish arachnids.
The eastern side of the canyon provides the best record of the Macrolobatus Zone, which is represented by several beds yielding ammonoids of the Tropites group, together with Anatropites div. sp.Conodont faunas from both these and higher beds are dominated by ornate metapolygnthids that would formerly have been collectively referred to Metapolygnathus primitius, a species long known to straddle the CNB. Within this lower part of the section, they resemble forms that have been separated as Metapolygnathus mersinensis. Slightly higher, forms close to Epigondolella' orchardi and a single Orchardella n. sp. occur. This association can be correlated with the latest Carnian in British Columbia.
Higher in the section, the ammonoid fauna shows a sudden change and is dominated by Tropithisbites. Few tens of metres above, but slightly below the first occurrence of Norian ammonoids Guembelites jandianus and Stikinoceras, two new species of conodonts (Gen et sp. nov. A and B) appear that also occur close to the favoured Carnian/Norian boundary at Black Bear Ridge, British Columbia. Stratigraphically higher collections continue to be dominated by forms close to M. mersinensis and E. orchardi after BC's own Mike Orchard.
The best exposure of the Kerri Zone is on the western side of the West Union Canyon. Ammonoids, dominated by Guembelites and Stikinoceras div. sp., have been collected from several fossil-bearing levels. Conodont faunas replicate those of the east section. The collected ammonoids fit perfectly well with the faunas described by Silberling in 1959, but they differ somewhat from coeval faunas of the Tethys and Canada.
The ammonoid fauna paints a compelling picture of Tethyan influence with a series of smoking guns. We see an abundance of Tropitidae in the Carnian, a lack of Pterosirenites in the Norian, copious Guembelites, the Tethyan species G. philostrati, the stratigraphic position of G. clavatus and the rare occurrence of Gonionotites. Their hallelujah moment was likely finding an undescribed species of the thin-shelled bivalve Halobia similar to Halobia beyrichi — the clincher that perhaps seals this deal on Tethyan influence.
I'll take a boo to see what Christopher McRoberts published on the find. A jolly good idea to have him on this expedition as it would have been easy to overlook if the focus remained solely on the conodonts and ammonoids. McRoberts has published on the much-studied Pardonet Formation up in the Willison Lake Area of Northeastern, British Columbia. He knows a thing or two about Upper Triassic Bivalvia and the correlation to coeval faunas elsewhere in the North American Cordillera, and to the Boreal, Panthalassan and Tethyan faunal realms.
If you fancy a read, they published a paper: "Towards the definition of the Carnian/Norian Boundary: New data on Ammonoids and Conodonts from central Nevada," which you can find in the proceedings of the 21st Canadian Paleontology Conference; by Haggart, J W (ed.); Smith, P L (ed.); Canadian Paleontology Conference Proceedings no. 9, 2011 p. 9-10.
| Fig. 1. Location map of Berlin-Ichthyosaur State Park |
Marco Balini, James Jenks, Riccardo Martin, Christopher McRoberts, along with Mike Orchard and Norman Siberling, did a bed by bed sampling in 2013 and published on The Carnian/Norian boundary succession at Berlin-Ichthyosaur State Park (Upper Triassic, central Nevada, USA) and published in January 2014 in Paläontologische Zeitschrift 89:399–433. That work is available for download from ResearchGate. The original is in German, but there is a translation available.
After years of reading about the correlation between British Columbia and Nevada, I had the very great pleasure of walking through these same sections in October 2019 with members of the Vancouver Paleontological Society and Vancouver Island Palaeontological Society. It was with that same crew that I'd originally explored fossil sites in the Canadian Rockies in the early 2000s. Those early trips led to paper after paper and the exciting revelations that inspired our Nevada adventure.
If you plan your own adventure, you'll want to keep an eye out for some of the other modern fauna — mountain lions, snakes, lizards, scorpions, wolves, coyotes, foxes, ground squirrels, rabbits, falcons, hawks, eagles, bobcats, sheep, deer and pronghorns.
Figure One: Location map of Berlin-Ichthyosaur State Park. A detailed road log with access information for this locality is provided in Lucas et al. (2007).
Monday, July 8, 2024
UNESCOCERATOPS: A SMALL LEPTOCERATOPSID DINOSAUR
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| Unescoceratops koppelhusae, Julius Csotonyi |
The Royal Tyrrell Museum of Palaeontology, named in honour of Joseph Burr Tyrrell, is a palaeontology museum and research facility in Drumheller, Alberta, Canada.
This jaw is the holotype specimen of this small leptoceratopsid dinosaur. Only a handful of isolated fossils have been found from this species, including a jaw that is the holotype specimen now in collections at the Royal Tyrell.
The Royal Tyrrell Museum of Palaeontology, named in honour of Joseph Burr Tyrrell, is a palaeontology museum and research facility in Drumheller, Alberta, Canada.
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| Unescoceratops koppelhusae, RTMP Collections |
The Cleveland Museum of Natural History's Michael Ryan and David Evans of the Royal Ontario Museum in Toronto recently determined that the specimen was a new genus and species.
Unescoceratops is a genus of leptoceratopsid ceratopsian dinosaurs known from the Late Cretaceous (about 76.5-75 million years ago) of Alberta, Canada. Unescoceratops is thought to have been between one and two meters long and less than 91 kilograms. A plant-eater, its teeth were the roundest of all Leptocertopsids.
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| Dinosaur Provincial Park, Alberta, Canada |
In addition to its particularly beautiful scenery, Dinosaur Provincial Park – located at the heart of the province of Alberta's badlands – is unmatched in terms of the number and variety of high-quality specimens.
To date, they represent more than 44 species, 34 genera and 10 families of dinosaurs, dating back 75-77 million years. This provides us with remarkable insight into life millions of years ago.
The park contains exceptional riparian habitat features as well as badlands of outstanding aesthetic value.
The creamy honey, beige and rust coloured hills around the fossil locality are outstanding examples of major geological processes and fluvial erosion patterns in semi-arid steppes — think glorious!The genus is named to honour the UNESCO World Heritage Site designation for the locality where the specimen was found and from the Greek “ceratops,” which means 'horned face'.
Dr Michael Ryan explained that he meant to honour UNESCO's efforts to increase understanding of natural history sites around the world.
© Julius T. Csotonyi An illustration of Unescoceratops koppelhusae, a plant-eating dinosaur from the Late Cretaceous period that lived approximately 75 million years ago shared with his gracious permission.
ABOUT THE ARTIST
Dr. Julius Csotonyi is a Vancouver-based scientific illustrator and natural history fine artist. He is a featured paleoartist on Season One of BC's Fossil Bounty. Julius has a scientific background in ecology (MSc) and microbiology (PhD) which has taken him to study sensitive ecosystems, from sand dunes in the Rocky Mountain parks to hydrothermal vents at the bottom of the Pacific Ocean.
These experiences have fuelled his strong resolve to work toward preserving our Earth’s biota. Painting biological subjects is one means that he uses to both enhance public awareness of biological diversity and to motivate concern for its welfare.
He paints murals and panels that have appeared in numerous museums including the Smithsonian’s National Museum of Natural History, press release images for scientific publications, books, stamp sets — including the outstanding 2018 “Sharks of Canada” set for Canada Post — and coins for the Royal Canadian Mint. To view more of Julius Csotonyi's exquisite work visit: https://csotonyi.com/
Sunday, July 7, 2024
AMMONITE TIME KEEPERS
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| Argonauticeras besairei, José Juárez Ruiz |
Ammonites were predatory, squidlike creatures that lived inside coil-shaped shells.
Like other cephalopods, ammonites had sharp, beak-like jaws inside a ring of squid-like tentacles that extended from their shells.
They used these tentacles to snare prey, — plankton, vegetation, fish and crustaceans — similar to the way a squid or octopus hunt today.
Catching a fish with your hands is no easy feat, as I am sure you know. But the Ammonites were skilled and successful hunters. They caught their prey while swimming and floating in the water column.
Within their shells, they had a number of chambers, called septa, filled with gas or fluid that were interconnected by a wee air tube. By pushing air in or out, they were able to control their buoyancy in the water column.
They lived in the last chamber of their shells, continuously building new shell material as they grew. As each new chamber was added, the squid-like body of the ammonite would move down to occupy the final outside chamber.
They were a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda.These molluscs, commonly referred to as ammonites, are more closely related to living coleoids — octopuses, squid, and cuttlefish) than they are to shelled nautiloids such as the living Nautilus species.
The Ammonoidea can be divided into six orders:
- Agoniatitida, Lower Devonian - Middle Devonian
- Clymeniida, Upper Devonian
- Goniatitida, Middle Devonian - Upper Permian
- Prolecanitida, Upper Devonian - Upper Triassic
- Ceratitida, Upper Permian - Upper Triassic
- Ammonitida, Lower Jurassic - Upper Cretaceous
Ammonites have intricate and complex patterns on their shells called sutures. The suture patterns differ across species and tell us what time period the ammonite is from. If they are geometric with numerous undivided lobes and saddles and eight lobes around the conch, we refer to their pattern as goniatitic, a characteristic of Paleozoic ammonites.
If they are ceratitic with lobes that have subdivided tips; giving them a saw-toothed appearance and rounded undivided saddles, they are likely Triassic. For some lovely Triassic ammonites, take a look at the specimens that come out of Hallstatt, Austria and from the outcrops in the Humboldt Mountains of Nevada.
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| Hoplites bennettiana (Sowby, 1826) Christophe Marot |
One of my favourite Cretaceous ammonites is the ammonite, Hoplites bennettiana (Sowby, 1826). This beauty is from Albian deposits near Carrière de Courcelles, Villemoyenne, near la région de Troyes (Aube) Champagne in northeastern France.
At the time that this fellow was swimming in our oceans, ankylosaurs were strolling about Mongolia and stomping through the foliage in Utah, Kansas and Texas. Bony fish were swimming over what would become the strata making up Canada, the Czech Republic and Australia. Cartilaginous fish were prowling the western interior seaway of North America and a strange extinct herbivorous mammal, Eobaatar, was snuffling through Mongolia, Spain and England.
In some classifications, these are left as suborders, included in only three orders: Goniatitida, Ceratitida, and Ammonitida. Once you get to know them, ammonites in their various shapes and suturing patterns make it much easier to date an ammonite and the rock formation where it is found.
Ammonites first appeared about 240 million years ago, though they descended from straight-shelled cephalopods called bacrites that date back to the Devonian, about 415 million years ago, and the last species vanished in the Cretaceous–Paleogene extinction event.
They were prolific breeders that evolved rapidly. If you could cast a fishing line into our ancient seas, it is likely that you would hook an ammonite, not a fish. They were prolific back in the day, living (and sometimes dying) in schools in oceans around the globe. We find ammonite fossils (and plenty of them) in sedimentary rock from all over the world.
In some cases, we find rock beds where we can see evidence of a new species that evolved, lived and died out in such a short time span that we can walk through time, following the course of evolution using ammonites as a window into the past.For this reason, they make excellent index fossils. An index fossil is a species that allows us to link a particular rock formation, layered in time with a particular species or genus found there.
Generally, deeper is older, so we use the sedimentary layers of rock to match up to specific geologic time periods, rather like the way we use tree rings to date trees. A handy way to compare fossils and date strata across the globe.
References: Inoue, S., Kondo, S. Suture pattern formation in ammonites and the unknown rear mantle structure. Sci Rep 6, 33689 (2016). https://doi.org/10.1038/srep33689
https://www.nature.com/articles/srep33689?fbclid=IwAR1BhBrDqhv8LDjqF60EXdfLR7wPE4zDivwGORTUEgCd2GghD5W7KOfg6Co#citeas
Photos: Argonauticeras besairei from the awesome José Juárez Ruiz.
Photo: Hoplites bennettiana from near Troyes, France. Collection de Christophe Marot

















