My Collection #2

Small Kosmoceras jason on a piece of Oxford Clay with a tiny
belemnite to the left.

These fossils were collected from Must Farm Brick Pit in Whittlesey, near Peterborough in Cambridgeshire, UK in June 2016.

Kosmoceras ammonites are known from Callovian age Oxford Clays of the Late Jurassic Period in Europe. These ammonites therefore date back to around 163 Ma. As with these two fossils, they are commonly found flattened in the clay, rarely it is possible to find three dimensional casts of the shell. The maximum diameter known from fossils is about ten centimetres. There is evidence of sexual dimorphism in these ammonite, the more decorated males have a smaller shell than the females, the purpose of the ornamentation is unknown.

Calcitic Kosmoceras jason from Kings
Dyke Brick Pit.

A larger iridescent Kosmoceras jason on a piece of Oxford Clay

The preserved phragmocone of a belemnite from the
Oxford Clay.

Cylindroteuthis is a belemnite known from the Early Jurassic, ~200 Ma, to the Early Cretaceous, ~140 Ma. This specimen is rather common, being found in Asia, Europe, North America and New Zealand. The calcitic guard of the belemnite is what is commonly found, lengths range from ten centimetres to twenty-two centimetres. Rarer fossils exhibit traces of appendages and an ink sac, showing their relation to squids. The guard would be an internal feature as traces of blood vessels have been found on the surface of the guard. This fossil is not to be confused with the shell of the belemnite, this is found within the guard, as shown in the photo to the right.

The largest of the Cylindroteuthis belemnites in my collection from the Oxford Clay at Kings Dyke Brick Pit.

This is a fragment on a bone from the giant fish Leedsichthys. This member of the pachycormidae is known from Callovian sediments of the late Jurassic. Discovered by Alfred Leeds in 1889 when the Peterborough brick making industry was taking off and quarries were being opened in and around the city, Leeds collected various marine fossils from the Oxford Clay in this time. Fossils have been found in England, France, Germany and Chile. In 2002, another individual was discovered in the Must Farm pit in Whittlesey by students at Portsmouth University. An excavation led by Jeff Liston of Yunnan University, revealed thousands of delicate bones, including the pectoral fin. A lot of the skeleton would have been composed of cartilage and so it doesn't fossilise. Size estimates put the fish at around twelve metres long. It is believed that a spike in planktonic populations were the reason behind the size of the Leedsichthys. Being a filter feeder, water would have been forced through gill rakers that removed the plankton from the water.

A small fragment of Leedsichthys problematicus from the Oxford Clay at Kings Dyke Brick Pit.

The larger and more complete Gryphaea
in my collection.

Also known as the Devil's Toenail, Gryphaea is an extinct genera of bivalve mollusc. Their geological range is from the late Triassic through to the Eocene. These bivalves are some of the more common finds in Jurassic marine deposits of Europe. They possibly lived in small colonies as shown in the photograph to the right. The bivalve had a larger hooked valve and a smaller, flatter lid. The
larger valve would be embedded in the sediment whilst the lid remained exposed. It is one of the only bivalves that have one valve larger than the other.

A broken Gryphaea from the Oxford Clay.

The underside of the above Gryphaea.

Dotternhausen and the Posidonia Schieffer

While on my third year residential fieldtrip to Southern Germany we visited to early Jurassic strata known as the Posidonia schieffer (shale). The rock here is somewhat akin to the Blue Lias of Lyme Regis and Charmouth, however the rock here is much more uniform and does not feature Milankovitch Cycles. This particular outcrop was in a quarry just outside Dotternhausen.

Everyone hard at work counting ammonites, you can see the
enthusiasm in the picture.

The shale was deposited under anoxic marine conditions, the sea floor would have been a soupy mud that supported no benthic fauna. This is perfect for exceptional preservation. Ammonites, crinoids, ichthyosaurs, pterosaurs, sharks and fish all would fall into this mud and sink. Due to the lack of oxygen aerobic bacteria would not be present and therefore decay would be inhibited. This leads to the preservation and discovery of fossil logs with crinoids attached and ichthyosaurs with skin outlines and embryos in the womb, just to name some examples.

The morning was spent at the Werkforum Museum at the cement works in Dotternhausen. Here we got a brief background to the fossils found in the quarry and what the environment would have been like 185 Ma.

So while visiting the Dotternhausen Quarry it was to be expected that as a cohort of 20 students we should find something between us.

Dactylioceras in one of many sheets of split shale.

Phylloceras from yet another sheet of shale.

Our first task was to collect and tabulate the number of ammonites with epibionts living on them. Myself and three of my close colleagues set to work splitting shale "sheets" and counting every ammonite in sight. Here I had my first find, a beautifully preserved fish fin, encircled by the disarticulated 'horseshore' structure of a Lytoceras ammonite.

The well preserved fish fin with the Lytoceras horseshoe
in the top of the picture.

I would have been happy to come away from the entire field trip with just this one find. But a few layers down, I come across a very small bone, about a centimetre or so in diameter. What we know is this is an Ichthyosaur vertebra. What we believe is that it is a tail vertebra of a juvenile because of how small it is. Unfortunately this was an isolated bone. Fortunately, it doesn't need any mechanical preparation as it is already well presented on the slab of shale it came from. Already I have had more success here in an hour than I have in three years of fossil hunting across numerous sites on the south coast of England.

The small tail vertebra from the ammonite exercise.

The small Ichthyosaur vertebra, in need of a
little treatment to protect it.

An hour or two after we arrived to the quarry we had all just about finished the exercise, and not a moment too soon with the day only getting hotter and hotter! And so, true to form with this class, we enthusiastically scrabbled over freshly blasted rock from the quarry wall in search of the fossils we had seen in the museum that morning.

I chose to split larger blocks bit by bit in the hope that there would be a bone or two preserved inside. A few blocks in, I start on one particular piece and put it on its side and begin hammering. It split a little too easy and at an odd angle, revealing a line of bones in the piece that had come away. Turning it over, I found that there was a line of vertebrae, criss-crossed by slender ribs. This was a disarticulated Ichthyosaur. Just on this block there was around 15 vertebrae. Definitely not complete but certainly exciting to find! It took three of us to move this block out so that the rest of the class could see what had been found.

The first block to be found in the quarry, with
some of the offcuts to the right.

The two main blocks and offcuts that we
managed to find and bring back to the
UK for preparation.

Meanwhile, the search continued for the rest of the animal. After shifting some rock, another block with a single vertebra and some definition of ribs was found. Still not complete but unfortunately there was no more of the Ichthyosaur to find. At first, I thought that the museum, or at least the cement works, would want this find for themselves. Some quarry owners in the UK confiscate fossils and sell them as profit, I assumed this was the same here. But, I was told that I would be allowed to keep them and bring them back to the UK to prepare the bones myself.

Side view of one offcut that thankfully fits back onto the
rounded block quite nicely

The two blocks are jam packed with bones, still not complete unfortunately. I believe that the centre of the skeleton is preserved, the tail and head unfortunately missing, possibly eaten by a much larger Ichthyosaur.

There's always one piece left over, no idea how this fits onto
either block. But it'll still make a nice addition to my collection.

I spoke to Professor Dave Martill about why the bones are scattered in the block as opposed to being articulated like the specimens we have seen before. He said that this is probably due to the final resting position of the animal in the Jurassic. It may well have come to rest on its ventral side and not be completely buried in the sediment, therefore decay would have taken place. Therefore you know have vertebrae that are elevated above the sediment and becoming loose due to the decay process. They will begin to fall out and land on the sediment in seemingly more random orientations. The same is true for the ribs.

The local museum has very kindly allowed me to use their equipment to prepare this find. Work will begin on the 27th June. I plan to upload nightly on the progress of the day even if it is just a photograph of what has been revealed so far. Needless to say, I'm very excited!

Lyme Regis (and a passing visit to Charmouth)

In this second part to the Dorset Fieldwork I will show you all the world famous Lyme Regis Lias outcrops. These were incredibly interesting both geologically and palaeontologically. Our trip leader, Professor David Martill found something very exciting when making our way back to the coach.

We visited the beach to the west of the town of Lyme Regis, Monmouth Beach.

Lyme Regis (with a quick stop at Charmouth):

Map of West Dorset showing the location of Monmouth Beach.
(Source: Google Maps)

The alternating succession of shales and argillaceous
limestones at Monmouth Beach. (Source:
https://www.shutterstock.com/video/clip-5416676-stock-
footage-the-blue-lias-beds-and-limestone-pavement-on-
monmouth-beach-cliffs-lyme-regis-on-the-jurassic.html)

The limestone ammonite pavement, or ammonite
graveyard. (Source: https://chandlerscottage.co.uk/1
125x750-lyme-regis-0772/)

In the morning after a rather lengthy drive from Swanage, we arrived in Charmouth. Although we didn't actually go onto the beach to see the cliffs up close, we got a pretty good view of the geology. I have also visited this site a number of times and will post the fossils I found in my collection series.

When standing at the Charmouth Heritage Centre, if you were to look to the west towards Lyme Regis those dark clay cliffs are called Black Ven. To the east you have Stonebarrow and the Golden Cap.

Charmouth is a Jurassic succession being deposited during the Sinnemurian to Pliensbachian ages of the lower Jurassic, approximately 190 Ma.

Black Ven is highly fossiliferous with ammonites being the most common fossil you will find. If you are very lucky you can also find crinoids, Ichthyosaur and Plesiosaur remains. A complete dinosaur, Scelidosaurus, has also been found here and is on display in the Charmouth Heritage Centre. Another must see is in the fossil shop, where they have on display a large Temnodontosaurus skull.

This is also one of the sites that Mary Anning collected from, finding marine reptiles and the pterosaur, Dimorphodon macronyx, later described by Sir Richard Owen.

After this brief talk we then drove a bit further west into Lyme Regis and walked down onto Monmouth Beach. Here you will notice, similar to Kimmeridge Bay, a repeating pattern in the cliffs between shales and argillaceous limestones, another example of Milankovitch Cyclicity.

But the really interesting thing to see here is in the wave cut platform that is formed by one of these bands of limestone. It is covered in hundreds of ammonites, the majority are of the genus Coroniceras. This was a single event where all of these ammonites died at the same time, this was gradual, possibly they returned to the same site seasonally. Ammonites won't be the only fossil you find here, you can also spot nautiloids, crinoids and gastropods. A complete Plesiosaur was even found in the pavement some years back.

If you wet the limestone around an ammonite you will find dark marks in the rock. These are fossilised burrows. Some are branching 'Y' shapes, this is formed by a shrimp, the name given to these burrows is Thalassinoides. Others will be two circles next to each other (Diplocraterion), straight burrows (Planolites), and some very fine burrows. These very small burrows are called Chondrites and show that the water had become anoxic for a period.

On the walk to the next locality, Professor Andy Gale found a large nautilus, preserved in three dimensions, a very nice find indeed. It was picked up by a course mate on the way back to the coach.

The next site was geologically of interest. This was the boundary between the limestone dominated White Lias, to the shale of the Blue Lias. The interesting part is, lithologically speaking the boundary is very clear, you can see a pale limestone become a dark shale. You would be forgiven for thinking that this is simply the boundary between the Rhaetian of the Triassic and the Hettangian of the Jurassic.

But to date the rock to confirm this is very difficult. The use of lavas of similar ages are regularly used to radiometrically date rock, however, there are no lavas to use. So dating could be done with the fossils, using relative dating. The change in the ammonites present between the White and Blue Lias represents a biological boundary. This is higher in the succession than the lithological boundary.

On the way back, Professor Dave Martill came across some Ichthyosaur remains in a limestone band of the Blue Lias. Unfortunately I did not see it but there was enough articulated material to warrant him going back to recover it.

The Fossilisation Process

When a land dwelling vertebrate dies its carcass is commonly disarticulated, this means its limbs are removed, often by predators and scavengers alike. Most of the decomposition of the organic material is done by bacteria that will feast on the rotting flesh that remains on the bones. Some bones are completely stripped clean of flesh and bleached in the sun. Others might be carried off or gnawed by rodents. Sometimes, disarticulated remains are trampled and scattered by herds of animals.


Sooner or later the bones are either destroyed or buried. If they aren’t digested their destruction can come from weathering; this is when the minerals in the bone begin to break down and the bones disintegrate. But the weathering can be stopped by rapid burial, it’s at this point fossils are formed. A body fossil is part of an organism that is buried and a trace fossil is an impression left behind in the ground by the organism.


Bone is made out of calcium-sodium hydroxyl apatite, this mineral weathers easily, this means that the mineral is no longer present once a bone becomes fossilised. This mineralogy can remain intact if the bone doe not come into contact with any fluids during its burial, something that is extremely rare.

It is possible to find tissues of extinct animals. Since bones are porous, the spaces once occupied by blood vessels and nerves fill up with minerals. This is called permineralisation.

Fossil of Archaeopteryx. Image credit Humboldt
Museum Fur Naturkunde Berlin

Pristine fossils can be found in geological lagerstatte, feathers of dinosaurs are known from these lagerstatte. Most famously the early bird Archaeopteryx is known from the Solnhofen lagerstatte in Germany.

Ammonite shells are originally made of aragonite, this is unstable so when fossilisation begins the aragonite becomes the more stable calcite. This calcite creates a cast of the shell and this is what we find today.

Woolly Mammoths and Woolly Rhinos have been discovered mummified in the permafrost in Siberia and Alaska. Soft tissue of a Tyrannosaurus Rex has even been found which allowed palaeontologists to see that the animal was female, within the fossil, red blood cells and connective tissues were found.

Natural mummies have been found in a variety of locations around the world; bog deposits or tar pits, deep inside caves, glacier ice and in the permafrost of Alaska and Siberia. A Woolly Rhinoceros was found mummified after it was covered in salty ground water that essentially pickled the carcass, preventing bacteria and microorganisms digesting the flesh by altering the pH of the environment which means that microorganisms cannot survive in these acidic conditions.

Mummified dinosaurs have been found, good examples of these mummies come from Brachylophosaurus and Edmontosaurus. Leonardo, the Brachylophosaurus that features in the palaeoart post, had skin impressions, muscle impressions that showed an excess of tissue around the neck, even parasites are found on Leonardo.


The permafrost is also effective as the low temperature prevents the bacteria from respiring by removing any moisture on the carcass through freezing. However, once the mummy is excavated the bacteria become active and decomposition begins.

Nurture or Nature?

So far I've only been looking at the prehistoric animals once they are mature, but what about their offspring? Was it best to lay a clutch of eggs and hope that some survive to create the next generation or is nurturing a small number of young to ensure they survive the ideal way to maintain populations.

Amphibians in general are a good example of nature taking hold, for the survival of

Modern day frog spawn, these eggs are incredibly vulnerable
to both predators and environmental changed.
Image credit vernalpool.org

offspring. We've all seen frog spawn in a pond, in prehistory amphibian eggs would be rather similar to this. They need to be laid in water to prevent drying out but have no protective layer like a shell in order to allow for the movement of water across the membrane. This makes the eggs vulnerable, these unprotected eggs would have been preyed on by early arthropods, fish and even other amphibians, possibly to eliminate competition. To counteract the loss of eggs, an individual would have to lay hundreds of these jelly like eggs. It is believed that the shelled amniote egg was the reason behind amphibian decline at the end of the Carboniferous Period. As thee climate began to dry out and become more arid, the amniote egg could tolerate it as the moisture is locked in the egg by the shell, whereas ideal environments for amphibian eggs became scarcer and created more and more competition.

Clutch of ammonite eggs from the Kimmeridge
clay of Dorset, UK. Image credit Terry Keenan

Discoveries in the Kimmeridge clay of Dorset show us something spectacular; ammonite eggs. Initially these clutches have been interpreted as egg sacks attached to the adult ammonite, there is no evidence as of yet that supports this as soft body parts are not preserved. Therefore logically these eggs are laid in well oxygenated sediments. There are two possibilities as to why these eggs failed out of the thousands laid. Firstly, the eggs could have been deposited in an anoxic environment before they could hatch. The other hypothesis is that the environment they were laid in had varying oxygen levels due to seasonal changes. Again the environment is a big threat to the eggs as with the amphibians. Predation probably wasn't as much of an issue, Plesiosaurs are one of few predators that actively searched the sea bed for food, invertebrates and microorganisms being other examples of predators.

Even though some animals leave their offspring to the mercy of nature, we do see some adaptations that help to increase the odds of survival. A good example of this is the famous dinosaur Diplodocus from the late Jurassic period. These eggs are large and round, the size of the eggs is the first adaptation. A large egg means a large hatchling. Size increases survival as it means only predators larger than the hatchlings are a threat. After hatching young Diplodocus will grow at an exponential rate, the larger they are the fewer threats there are, before long the nest raiders are no longer a problem. Diplodocus nests are created underground, this helps to incubate the eggs, not only this it also prevents the eggs being scavenged by nest raiders. These adaptations all come together to improve chances of survival for the young sauropods.

Crushed eggshell of a titanosaur from Auca Maheuvo nesting
site. Image credit dougu.me

Dinosaurs later became more parental, we start to find evidence of a move towards nurturing the young. There is no evidence for direct nurturing of young after they've left the nest, however footprints do show young members of herds so perhaps there is a collective nurture from all mature members of the herd. But when we look at a vast nesting site at Auca Mahuevo in Argentina, there is evidence all around that young Argentinosaurs were kept in the nest and cared for. This evidence is crushed eggshells. This indicates that the young were spending the first stages of life in the nest watched over and fed by the adult. Titanosaurs aren't the only dinosaurs to make this step, a lot of Cretaceous dinosaurs were tending to nests, its believed even Tyrannosaurus rex had a parental instinct until the young were mature enough to fend for themselves. Birds and crocodiles today have this kind of care for their young.

Mammals are a good example of nurture rather than nature. Mammals are known to have few offspring and care for them for much longer in order to ensure survival to sexual maturity. Focusing all this effort and energy on a single offspring is potentially less efficient, given that only one individual reaches maturity. So could it be that the more vulnerable genera require nurture for survival? Look at our own ancestors for an example, the Australopithecines were not as fast as other predators of the time, such as Dinofelis, therefore our ancestors relied on intelligence to trap prey as well as falling back on an omnivorous diet. But we were prey as well, we were and still are a delicate species. Larger mammals and predators had the ability to kill an Australopithecine with ease. Meaning we must have had to protect our young to create the next generation.

So what do you think, is it quantity or quality that you think is more successful? Let me know in the comments.

My Collection #1

So in this feature I want to share the fossils and rock that I have in my collection, give you a little information about each piece. Hope you enjoy reading it.

I thought a good place to start was with the first fossils that I received as a present, and the first fossils I owned. There is a range of fossils in this box ranging from the Ordovician to the Eocene.

Scyphocrinites elegans stems.

Artist's impression of Scyphocrinites elegans
with loboliths. Image credit: Terry McKee

Firstly is a piece that features numerous crinoid stems. There are approximately 625 species of crinoid, both extinct and extant. Crinoid origins officially date back to the Ordovician, however there is one species known from the Cambrian Burgess Shale, Echmatocrinus, but it is unclear as to whether this fossil is a crinoid or an octocoral. Crinoids are typically found attached to a substrate on the sea floor, there are some exceptions as some species anchor themselves to driftwood and reside at the surface. These simple organisms are filter feeders, they use tiny structures called pinnules that line the brachials to catch tiny plankton, this is where the colloquial name of 'sea lillies' comes from as the brachials make them look like flowers, despite being a member of the echinodermata. Crinoids have also been known to create 'forests', with individuals of varying heights. This particular species has a geological range between 416.0 to 412.3 Ma, placing this fossil in the opening of the Devonian period. It had a structure called a lobolith instead of a holdfast, this was a flotation device meaning that these crinoids floated on the surface, as shown in the artist's impression, the brachials can then been seen hanging in the water at the end of the stem, the stems are what is preserved in this fossil. This specimen comes from Erfoud, Morocco.

Orthoceras sp. in Moroccan Limestone.

Orthoceras sp. on Devonian limestone, from Cumberland House
Museum, Portsmouth

Orthoceras is a genus of straight cephalopod with a geological range between 471.8 to 205.6 Ma (Early Ordovician to Late Triassic). These fossils, like the one above, are commonly found in marine limestones. In rare occasions Orthoceras can be found in monospecific assemblages, previously theorised to be mass deaths after mating rituals, it is now, after sedimentological and taphonomical studies, widely accepted that the shells were deposited over time rather than during a single event. The assemblages are more common throughout the Ordovician until the early Devonian. Orthoceras did not grow to massive sizes like other straight cephalopods, reaching about 6 inches in length. This fossil is often confused with the Cretaceous ammonoid, Baculites. A key difference that helps to identify each fossil is that the Baculites exhibits the complex ammonitic sutures whereas Orthoceras has a simple suture. Some specimens have a medial line between the anterior and the posterior of the shell. This is called the siphuncle, a tissue that allows for the disposal of water from the formation of new chambers as the shell grows. This is done through osmosis. It also allows for a change in density, taking in more water to sink, and releasing water to become more buoyant. The two Orthoceras fossils are from Erfoud, Morocco dating back to around 400 Ma in the Early Devonian. The fossil pictured right is from the Cumberland House Museum in Portsmouth, definitely worth a visit if you're in the area.

Goniatites sp. from the Moroccan limestone

Goniatite fossil with sutures. Image credit: educationalfossils.com

Goniatites are ammonoid cephalopods that occupied the oceans of our planet between the early Devonian, 391.9 Ma, to the Permian extinction 251.4 Ma. These cephalopods are morphologically similar to ammonites in the sense that they have a series of gas filled chambers to allow for buoyancy and a single living chamber. A major difference between the two shelled creatures is their suture patterns, the ammonite suture is incredibly complex, the suture of the Goniatite is quite simple, more of a zig-zag. It is clearer to see on the image on the left. There is little to no evidence to how this animal lived, nor is there evidence of a calcified jaw, similar to the ammonite, which eliminates shellfish as a food source. The fossil pictured above is again from Erfoud, Morocco, dating back to the late Devonian, 360 Ma.

Heliophora orbiculus

This interesting fossil is known as a sand dollar. These are highly modified sea urchins that reside on sandy sea floors. These sea urchins are found mostly in shallow tropical waters and temperate seas. With a geological range of 9 Ma to recent times. The odd outline of the outer edge of the echinoid that you can see in the photograph has no official explanation to its use in life. Some hypotheses suggest that they aided feeding, while others state they allow the creature to anchor itself in the sand to prevent the current from carrying it away. This particular specimen comes from Morocco and dates back to the early Pleistocene 2 Ma.

Terebratula sp.

This is an example of an epifaunal brachiopod, epifaunal meaning that it lives on the surface of the sea floor. This genus of brachiopod is a suspension feeder, like the crinoids they feed on plankton and other microscopic organisms. The hole that you see in the larger valve of the photograph above is known as the pedicle opening. This is where the pedicle emerges to attach the brachiopod to a substrate. It is common that bivalves and brachiopods get mixed up as they are similar at first glance. However, for the most part bivalves are symmetrical, with the exception of Gryphaea. Brachiopods have one valve larger or a different shape to the other. Also bivalves don't have a pedicle opening as their pedicle comes from between the valves to feed. This species of brachiopod first evolved approximately 268 Ma in the late Permian surviving until 0.781 Ma in the Pleistocene. This particular specimen dates back to around 120 Ma in the early Cretaceous, it was then discovered in Agadir, Morocco. 

Flexicalymene ouzregi

This small trilobite dates back to around 450 Ma in the late Ordovician, it is named after the location of it's discovery, Ikhf-n-Ouzreg, Morocco. The geological range of this species of trilobite is from the middle Ordovician, 463.5 Ma, to the late Silurian, 426 Ma. It is common to find this species of trilobite enrolled, this is hypothesised to have been a defense mechanism. This was more likely to be due to an external stimulus, possibly a predator or environmental hazard. The cephalon (head) of this specimen is better preserved than the more damaged pygidium (posterior). The eyes are visible, however it is not possible to determine whether they are holochroal or schizochroal. For an explanation on holochroal and schizochroal take a look at my post on the Cambrian period. 

Trinucleus fimbriatus

Another species of trilobite and also my oldest specimen in my collection, this is the cephalon of a 460 My old trilobite from Llanfar, Wales, UK. A geological range of between 466 to 455.8 Ma places the trilobite in the middle to late Ordovician. This species lacks the typical compound eyes that most trilobites exhibit. Instead there are small pits lining the outer edge of the cephalon, it is believed that these are sensory pits that could detect movement in the water, helping to hunt and evade predators. This is a likely use for the pits as the trilobite lived approximately 200 metres beneath the surface of the oceans, light cannot penetrate this far down and so eyes would be useless. 

Toxaster peroni

This is another example of an echinoid. This specimen is from the early Cretaceous, 118 Ma, from Agadir, Morocco. This echinoid survived the Mesozoic world between the early Cretaceous 140.2 Ma to the start of the late Cretaceous 99.7 Ma. This differs from the sand dollar shown earlier in the fact that this is an infaunal echinoid, meaning that it lived within the sediment itself rather than on it. It was also a detritivore rather than a filter feeder. 

Placosmilia sp.

Placosmilia is an example of a scleractinian coral of the phylum cnidaria. Placosmilia originate 167.7 Ma in the middle Jurassic, becoming extinct only 5.332 Ma in the Pliocene. This particular coral is solitary, scleractinian corals are known for being colonial and solitary. These corals build themselves a hard skeleton that is topped with the mouth surrounded by tentacles. This specimen was discovered in Lleida, Spain, and dates back to 80 Ma in the late Cretaceous. 

Otodus obliquus

This tooth is from the top predator of it's time. A genus of extinct Mackerel Shark, Otodus lived between the early Palaeocene, 61.7 Ma, to the middle Miocene 13.65 Ma, this particular specimen comes from 55 Ma, this is the Ypresian stage of the early Eocene. The morphology of this shark is unknown because, as with most other sharks, the skeleton is composed primarily of cartilage which doesn't fossilise, therefore very few skeletal structures are known of this genus. The largest tooth however, measured 104mm, and shows signs of the evolution of serrated teeth in sharks. Studies on the vertebral centrum of these sharks put length estimates between 9.1 and 12.2 metres long, meaning this shark dominated the oceans on a global scale during it's reign. 

Three ammonites, the bottom two from Madagascar and the top from Deux Sevres in France.

Ammonite fossil showing complex sutures. Image
credit: fossilmall.com

Ammonites are by far the most common Mesozoic marine fossils that can be found, so common that they are used in relative dating of Mesozoic rocks. Ammonites have a massive geological range between 400 Ma in the Early Devonian to the KT Boundary at the end of the Cretaceous 66 Ma. These coiled cephalopods are related to the Goniatite shown above. Ammonites survived the massive Permian extinction but not the extinction that wiped out the dinosaurs and other reptiles of the Mesozoic. In life the shells of the ammonites would be made of aragonite but this is more unstable than calcite and therefore the shells change their chemical composition to become more stable. The fossils we find are actually casts of where sediment has entered the chambers of the shell and the shell has consequently broken down leaving a cast behind. It is sometimes possible to find the complex ammonitic sutures on the fossils, as shown in the photograph on the right. 

Diplomystus dentatus from Kemmerer, Wyoming, USA

Possibly the most impressive fossil on this post, this is a brilliantly preserved fish in a fossil lagerstätte from 55 Ma, this fossil therefore comes from the early Eocene. This is a genus of freshwater fish that is related to herrings and sardines that swim in our oceans today. The upturned mouth of this specimen and genus as a whole is indicative of a surface feeding fish. It is relatively conclusive that Diplomystus fed on smaller fish called Knightia as the bones of Knightia have been found in the stomach of Diplomystus. The geological range of this fish is very short, from 55.8 to 50.3 Ma, this genus of fish evolved and became extinct in the Eocene. 

So that's it for now, please do share any interesting specimens you have in your collection or just share your thoughts in the comments below. 

Palaeoart: Feeding Ichthyosaurs

This particular piece was created by Robert Nicholls. It depicts a feeding frenzy in the late Jurassic oceans, this artwork actually features in the geology gallery at Peterborough Museum, this gallery is dedicated to the fossil fauna of the local Oxford Clay, an interesting exhibit if you happen to be in the city. 

The scene here is of three Ichthyosaurs feeding on a shoal of fish. This is an interesting creation as although our eyes are drawn to the action of the marine reptiles and the energetic shoal, looking closer you can see a number of ammonites in the background and also squid around the edges. These squid are responsible for the fossil belemnites that can be found in the Oxford Clay, they are long guards that end in a point and provide some protection for the animal. Nicholls has depicted these squid ejecting ink like modern day squid, a nice addition as it is possible to find the remains of this ink sack in some fossils, although this is very rare. 

Another aspect I find interesting is the Ichthyosaur's appearance, the large eye and long snout show the key adaptations of these animals. Giving the Ichthyosaur a keen eyesight in the murky waters combined with a slender snout to pierce through the water to snatch prey, making it a real danger for anything unfortunate enough to come face to face with this predator. 

Nicholls appears to have taken some inspiration from the behaviour of modern dolphins. These mammals attack shoals of fish in a similar way to the Ichthyosaurs in this artwork, taking it in turns to dart through the shoal and grab a meal. 

So what do you think of this piece, do you find it as interesting as I do? Let me know in the comments what your favourite thing is or another piece of artwork that you particularly like.