Puffbird similar to Fossil Birds found at Driftwood Canyon |
Metasequoia, the Dawn Redwood |
A Tapir showing off his prehensile nose trunk |
Puffbird similar to Fossil Birds found at Driftwood Canyon |
Metasequoia, the Dawn Redwood |
A Tapir showing off his prehensile nose trunk |
This matrix you see here is the Gault Clay, known locally as the Blue Slipper. This fine muddy clay was deposited 105-110 million years ago during the Lower Cretaceous (Upper and Middle Albian) in a calm, fairly deep-water continental shelf that covered what is now southern England and northern France.
Lack of brackish or freshwater fossils indicates that the gault was laid down in open marine environments away from estuaries. The maximum depth of the Gault is estimated 40-60m a figure which has been reached by the presence of Borings made by specialist Algal-grazing gastropods and supported by a study made by Khan in 1950 using Foraminifera. Estimates of the surface water temperatures in the Gault are between 20-22°c and 17-19°c on the seafloor. These estimates have been reached by bulk analysis of sediments which probably register the sea surface temperature for calcareous nanofossils.
It is responsible for many of the major landslides around Ventnor and Blackgang the Gault is famous for its diverse fossils, mainly from mainland sites such as Folkestone in Kent.
Folkestone, Kent is the type locality for the Gault clay yielding an abundance of ammonites, the same cannot be said for the Isle of Wight Gault, however, the south-east coast of the island has proved to be fossiliferous in a variety of ammonites, in particular, the Genus Hoplites, Paranahoplites and Beudanticeras.
While the Gault is less fossiliferous here on the island it can still produce lovely marine fossils, mainly ammonites and fish remains from these muddy mid-Cretaceous seas. The Gault clay marine fossils include the ammonites (such as Hoplites, Hamites, Euhoplites, Anahoplites, and Dimorphoplites), belemnites (such as Neohibolites), bivalves (notably Birostrina and Pectinucula), gastropods (including the lovely Anchura), solitary corals, fish remains (including shark teeth), scattered crinoid remains, and crustaceans (look for the crab Notopocorystes).
Occasional fragments of fossil wood may also be found. The lovely ammonite you see here is from the Gault Clays of Folkstone. Not all who name her would split the genus Euhoplites. There’s a reasonable argument for viewing this beauty as a very thick form of E. loricatus with Proeuhoplites being a synonym of Euhoplites.
Jack Wonfor shared a wealth of information on the Gault and has many lovely examples of the ammonites found here in his collections. If you wish to know more about the Gault clay a publication by the Palaeontological Association called 'Fossils of the Gault clay' by Andrew S. Gale is available in Dinosaur Isle's gift shop.
There is a very good website maintained by Fred Clouter you can look at for reference. It also contains many handy links to some of the best fossil books on the Gault Clay and Folkstone Fossil Beds. Check it out here: http://www.gaultammonite.co.uk/
Euhoplites is an extinct ammonoid cephalopod from the Lower Cretaceous, characterized by strongly ribbed, more or less evolute, compressed to inflated shells with flat or concave ribs, typically with a deep narrow groove running down the middle.
In some, ribs seem to zigzag between umbilical tubercles and parallel ventrolateral clavi. In others, the ribs are flexious and curve forward from the umbilical shoulder and lap onto either side of the venter.
Its shell is covered in the lovely lumps and bumps we associate with the genus. The function of these adornments are unknown. I wonder if they gave them greater strength to go deeper into the ocean to hunt for food.
They look to have been a source of hydrodynamic drag, likely preventing Euhoplites from swimming at speed. Studying them may give some insight into the lifestyle of this ancient marine predator. Euhoplites had shells ranging in size up to a 5-6cm.
We find them in Lower Cretaceous, middle to upper Albian age strata. Euhoplites has been found in Middle and Upper Albian beds in France where it is associated respectively with Hoplites and Anahoplites, and Pleurohoplites, Puzosia, and Desmoceras; in the Middle Albian of Brazil with Anahoplites and Turrilites; and in the Cenomanian of Texas.
This species is the most common ammonite from the Folkstone Fossil Beds in southeastern England where a variety of species are found, including this 37mm beauty from the collections of José Juárez Ruiz.
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:
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.
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
Highly prized as seafood, lobsters are economically important and are often one of the most profitable commodities in coastal areas they populate.
These lobsters are related to the modern-day lobsters. They lived in warm, shallow seas during the Cenomanian, some 93.9–100.5 million years ago.
This cutie was found in Cretaceous outcrops at Hâdjoula. The sub‐lithographical limestones of Hâqel and Hâdjoula, in northwest Lebanon, produce beautifully preserved shrimp, fish, and octopus. The localities are about 15 km apart, 45 km away from Beirut and 15 km away from the coastal city of Jbail.
Dan Bowen, Chair, VIPS, Trent River |
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. And it is massive. At 103 million km2 (40 million sq mi), it is the largest tectonic plate and continues to grow fed by volcanic eruptions that piggyback onto its trailing edge.
This relentless expansion pushes the Pacific Plate into the North American Plate. The pressure subducts it beneath our continent where it then melts back into the earth. Plate tectonics are slow but powerful forces.
The island chains that rode the plates across the Pacific smashed into our coastline and slowly built the province of British Columbia. And because each of those islands had a different origin, they create pockets of interesting and diverse geology.
It is these islands that make up the Insular Belt — a physio-geological region on the northwestern North American coast. It consists of three major island groups — and many smaller islands — that stretches from southern British Columbia up into Alaska and the Yukon. These bits of islands on the move arrived from the Late Cretaceous through the Eocene — and continues to this day.
The rocks that form the Insular Superterrane are allochthonous, meaning they are not related to the rest of the North American continent. The rocks we walk over along the Trent River are distinct from those we find throughout the rest of Vancouver Island, Haida Gwaii, the rest of the province of British Columbia and completely foreign to those we find next door in Alberta.
To discover what we do find on the Trent takes only a wee stroll, a bit of digging and time to put all the pieces of the puzzle together. The first geological forays to Vancouver Island were to look for coal deposits, the profitable remains of ancient forests that could be burned to the power industry.
Jim Monger and Charlie Ross of the Geological Survey of Canada both worked to further our knowledge of the complex geology of the Comox Basin. They were at the cutting edge of west coast geology in the 1970s. It was their work that helped tease out how and where the rocks we see along the Trent today were formed and made their way north.We know from their work that by 85 million years ago, the Insular Superterrane had made its way to what is now British Columbia.
The lands were forested much as they are now but by extinct genera and families. The fossil remains of trees similar to oak, poplar, maple and ash can be found along the Trent and Vancouver Island. We also see the lovely remains of flowering plants such as Cupanities crenularis, figs and breadfruit.
Heading up the river, you come to a delineation zone that clearly marks the contact between the dark grey marine shales and mudstones of the Haslam Formation where they meet the sandstones of the Comox Formation. Fossilized material is less abundant in the Comox sandstones but still contains some interesting specimens. Here you begin to see fossilized wood and identifiable fossil plant material.
Further upstream, there is a small tributary, Idle Creek, where you can find more of this terrestrial material in the sandy shales. As you walk up, you see identifiable fossil plants beneath your feet and jungle-like, overgrown moss-covered, snarly trees all around you.
Walking west from the Trent River Falls at the bottom, you pass the infamous Ammonite Alley, where you can find Mesopuzosia sp. and Kitchinites sp. of the Upper Cretaceous (Santonian), Haslam Formation. Minding the slippery green algae covering some of the river rocks, you can see the first of the Polytychoceras vancouverense zone.
Continuing west, you reach the first of two fossil turtle sites on the river — amazingly, one terrestrial and one marine. If you continue, you come to the Inland Island Highway.
The Trent River has yielded some very interesting marine specimens, and significant terrestrial finds. We have found a wonderful terrestrial helochelydrid turtle, Naomichelys speciosa, and the caudal vertebrae of a Hadrosauroid dinosaur. Walking down from the Hadrosaur site you come to the site of the fossil ratfish find — one of the ocean's oddest fish.
Ratfish, Hydrolagus Collie, are chimaera found in the north-eastern Pacific Ocean today. The fossil specimen from the Trent would be considered large by modern standards as it is a bruiser in comparison to his modern counterparts.This robust fellow had exceptionally large eyes and sex organs that dangled enticingly between them. You mock, but there are many ratfish who would differ. While inherently sexy by ratfish standards, this fellow was not particularly tasty to their ancient marine brethren (or humans today) — so not hugely sought after as a food source or prey.
A little further again from the ratfish site we reach the contact of the two Formations. The rocks here have travelled a long way to their current location. With them, we peel away the layers of the geologic history of both the Comox Valley and the province of British Columbia.
The Trent River is not far from the Puntledge, a river whose banks have also revealed many wonderful fossil specimens. The Puntledge is also the name used by the K'ómoks First Nation to describe themselves. They have lived here since time immemorial. Along with Puntledge, they refer to themselves as Sahtloot, Sasitla and Ieeksun.
References: Note on the occurrence of the marine turtle Desmatochelys (Reptilia: Chelonioidea) from the Upper Cretaceous of Vancouver Island Elizabeth L. Nicholls Canadian Journal of Earth Sciences (1992) 29 (2): 377–380. https://doi.org/10.1139/e92-033; References: Chimaeras - The Neglected Chondrichthyans". Elasmo-research.org. Retrieved 2017-07-01.
Directions: If you're keen to explore the area, park on the side of Highway 19 about three kilometres south of Courtenay and hike up to the Trent River. Begin to look for parking about three kilometres south of the Cumberland Interchange. There is a trail that leads from the highway down beneath the bridge which will bring you to the Trent River's north side.
Smilodon is a genus of the extinct machairodont subfamily of the felids. It is one of the most famous prehistoric mammals and the best known saber-toothed cat. Although commonly known as the saber-toothed tiger, it was not closely related to the tiger or other modern cats.
Up until a few years ago, all the great fossil specimens of this apex predator were found south of us in the United States. That was until some interesting bones from Medicine Hat, Alberta got a second look.
A few years ago, a fossil specimen caught the eye of researcher Ashley Reynolds as she was rummaging through the collections at the Royal Ontario Museum in Toronto.
Back in the 1960s, University of Toronto palaeontologist C.S. Churcher and his team had collected and donated more than 1,200 specimens from their many field seasons scouring the bluffs of the South Saskatchewan River near Medicine Hat, Alberta.
Churcher is a delightful storyteller and a palaeontologist with a keen eye. I had the very great pleasure of listening to many of his talks out at the University of British Columbia and a few Vancouver Paleontological Society meetings in the mid-2000s.
"Rufus" was a thoroughly charming storyteller and shared many of his adventures from the field.
He moved out to the West Coast for his retirement, first to Gabriola Island then to Victoria, but his keen love of the science kept him giving talks to enthralled listeners keen to hear about his survey of the Dakhleh Oasis in the Western Desert of Egypt, geomorphology, stratigraphy, recent biology, Pleistocene and Holocene lithic cultures, insights learned from Neolithic Islamic pottery to Roman settlements.
The specimens he had collected had been roughly sorted but never examined in detail. Reynolds, who was researching the growth patterns and life histories of extinct cats saw a familiar-looking bone from an ancient cat's right front paw. That tiny paw bone had reached through time and was positively identified as Canada's first Smilodon.
These Apex Predators used their exceptionally long upper canine teeth to hunt large mammals.
Isotopes preserved in the bones of S. fatalis in the La Brea Tar Pits in California tell us that they liked to dine on bison (Bison antiquus) and camels (Camelops) along with deer and tapirs. Smilodon is thought to have killed its prey by holding it still with its forelimbs and biting it. And that was quite the bite!
Their razor-sharp incisors were arranged in an arch. Once they bit down, the teeth would hold their prey still and stabilize it while the canine bite was delivered — and what a bite that was. They could open their mouths a full 120 degrees.
Smilodon died out at the same time that most North and South American megafauna disappeared, about 10,000 years ago. Its reliance on large animals has been proposed as the cause of its extinction, along with climate change and competition with other species.
Melissa Kay, Fossil Restoration Technician, Dino Lab Inc. |
Dr. Catherine Hickson & Dr. John Clague |
Dendrerpeton acadianum, an extinct amphibian |
These little cuties belong to an extinct genus of amphibians who loved wet, swampy wetlands similar to those we find in the bayous of Mississippi today.
Dendrerpeton is the primitive sister-group to a clade of Temnospondyls that includes Trimerorhachoids, the Eryopoids — Ervops, Parioxys, & Sclerocephalus — Zatracheids & Dissorophoids.
This little guy along with finding the first true reptile, Hylonomus lyelli, ancestor of all dinosaurs that would rule the Earth 100 million years later serve as the reference point where animals finally broke free of the water to live on land. This evolutionary milestone recorded at Joggins remains pivotal to understanding the origins of all vertebrate life on land, including our own species.
Joggins records life in a once a wet, swampy wetland |
Pennsylvanian Coal Age Ecosystem, 300-Million-Years-Old |
References & further reading:
Joggins Fossil Cliffs: https://jogginsfossilcliffs.net/cliffs/history/
Image: Hylonomus lyelli, Una ricostruzione di ilonomo by Matteo De Stefano/MUSEThis file was uploaded by MUSE - Science Museum of Trento in cooperation with Wikimedia Italia., CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=48143186
Image: Arthropleura: Par Tim Bertelink — Travail personnel, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=48915156
Joggins Map: Joggins Fossil Cliffs: https://jogginsfossilcliffs.net/cliffs/history/
A gull cries in protest at not getting his share of a meal |
Eype is a small village that hugs the English Channel in southwest Dorset near the town of Bridport on the infamous Jurassic Coast. Picture creamy rust-coloured sand, a shelved shingle bank backed by a massive cliff-face and the constant rush of waves.
Aside from the surf, this is a quiet hamlet and a wonderful place to explore along the pebble beach. You'll want to stay well away from the cliffs as rock slides happen quickly and the debris field is much wider than you would think.
Prepping these lovelies is a tricky business as the flanges are very delicate. You can see that many of the ornamental rings are intact. The specimen itself is amazing but the level of patience and skill that went into the preparation of this lovely cephalopod is world-class.
Photo: Specimen: 16 cm (just over 6 inches) at its widest point. Craig Chivers, Natural Selection Fossils. If you would like to see more of Craig's work, head on over to his website: naturalselection fossils.com or check out his Instagram account @naturalselectionfossils. You will drool over the incredible ammonites, marine reptile material and some bivalves — plus some paleo art thrown in for good measure.
Spinosaurus the Spine Lizard of the Cretaceous |
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 |
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
Capilano Watershed & Reservoir |
Capilano River Canyon & Regional Park |
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 — octopus, squid, and cuttlefish — than they are to shelled nautiloids such as the living nautilus species.
Ammonoidea can be divided into six orders:
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.
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
Ankylosaur — Armoured Plant-Eating Dinosaur |