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.