Thursday, 31 January 2019

APODEROCERAS, YOUR GRACE

This stunning specimen with her regal ridges (and small anomaly) is an Apoderoceras ammonite. Apoderoceras are an extinct genus of cephalopod, an active predatory mollusk belonging to the subclass Ammonoidea.

Apoderoceras is, in fact, a wonderful example of sexual dimorphism within ammonites as the macroconch (putative female) shell grew to diameters in excess of 40 cm – many times larger than the diameters of the microconch (putative male) shell. Apoderoceras has been found in the Lower Jurassic of Argentina, Hungary, Italy, Portugal, and most of North-West and central Europe, including as this one is, the United Kingdom. She was found on the beaches of Charmouth in West Dorset, then prepped expertly by the lovely and talented Lizzie Hingley. 

Neither Apoderoceras nor Bifericeras donovani are strictly index fossils for the Taylori subzone, the index being Phricodoceras taylori. Note that Bifericeras is typical of the earlier Oxynotum Zone, and ‘Bifericeras’ donovani is doubtfully attributable to the genus.

The International Commission on Stratigraphy (ICS) has assigned the First Appearance Datum of genus Apoderocerasas and of Bifericeras donovani the defining biological marker for the start of the Pliensbachian Stage of the Jurassic, 190.8 ± 1.0 million years ago.  As the brilliant Murray Edmunds points out, this lovely large specimen (macroconch) of Apoderoceras is likely a female. Her larger body perfected for egg production.

Cat's Paw Suture Walls of Apoderoceras
Apoderoceras (Family Coeloceratidae) appears ‘out of nowhere’ in the basal Pliensbachian and dominates the ammonite faunas of NW Europe. It is superficially similar to the earlier Eteoderoceras (Family Eoderoceratidae, of the Raricostatum Zone), but on close inspection can be seen to be quite different.  It is, therefore, an ‘invader’ and its ancestry is cryptic.

The Pacific ammonite Andicoeloceras, known from Chile, appears quite closely related and may be ancestral, but the time correlation of Pacific and NW European ammonite faunas is challenging. Even if Andicoeloceras is ancestral to Apoderoceras, no other preceding ammonites attributable to Coeloceratidae are known. (Maybe there are clues in the Lias of Canada?) Apoderoceras remains present in NW Europe throughout the Taylori Subzone, showing endemic evolution.

It becomes progressively more inflated during this interval of time, the adult ribs more distant, and there is evidence that the diameter of the macroconch evolved to become larger. At the end of the Taylori Subzone, Apoderoceras disappeared as suddenly as it appeared in the region, and ammonite faunas of the remaining Jamesoni Zone are dominated by the Platypleuroceras–Uptonia lineage, generally assigned (but erroneously, IMO!) to the Family Polymorphitidae.

In the NW European Taylori Subzone, Apoderoceras is accompanied (as well as by the Eoderoceratid, B. donovani, which is only documented from the Yorkshire coast, although I know of examples from Northern Ireland) by the oxycones Radstockiceras (quite common) and Oxynoticeras (very rare), the late Schlotheimid, Phricoderoceras (uncommon: note P. taylori is a microconch, and P. lamellosum the macroconch), and the Eoderoceratid, Tetraspidoceras (very rare).

Thank you to Murray Edmunds for his advice, guidance and corrections as we explore Apoderoceras and the ammonite faunas of the Pacific and NW Europe. You are deeply awesome, my friend!
Check out Murray’s Research Gate site for more interesting tidbits!

https://www.researchgate.net/profile/Murray_Edmunds; the photo above of the Cat's Paw Sutures of an Apoderoceras from Dorset are from the lovely Simon Guscott. Appreciate you!

Wednesday, 30 January 2019

DINOGORGON: TERROR OF THE LATE PERMIAN

Dinogorgon Rubidgei / Photo: Jonathan Blair / Corbis
A quarter of a billion years ago, long before dinosaurs or mammals evolved, this three-metre (10-foot) gorgonopsid, Dinogorgon, terrorized the floodplains of what is now South Africa and Tanzania during the Late Permian.

For many years, we've believed that these mighty hunters reigned and died out in less than a million years. Dinogorgon is meant to have vanished during one of the greatest mass extinction events on the planet, the Permian Extinction. We've recorded five mass extinction events in our humble 4.6 billion year history. The event from the Permian wiped our about nine of every ten plant and animal species on the planet. New fossil evidence suggests that there were actually two mass extinctions during this time, with a sixth event happening around 260 million years ago.


Tuesday, 29 January 2019

UPPER CRETACEOUS NANAIMO GROUP

Upper Cretaceous Nanaimo Group / Denman Island
The Upper Cretaceous Nanaimo Group of southwest British Columbia is a four-kilometre thick succession of mostly deep marine siliciclastics sitting directly above the Insular Superterrane.

This succession has been the focus of many paleomagnetic, isotope geochemistry, paleontology, and sedimentology studies with the aim of untangling the tectonic history and paleolatitude of the Insular Superterrane during the Nanaimo Group deposition some 90 to 65 million years ago.

One would think that these research papers would support each other in terms of that deposition. Much to our chagrin, we're still working through the strata to define both the formal stratigraphy, untangle if it was deposited in single or multiple basins and match it up with local and regional correlations.

The upper two-thirds of the succession is continuously and well exposed on Denman and Hornby islands and represents the best example of this part of the succession in the northern half of what we consider the single Nanaimo Basin. This area includes the previously only informally defined type areas for the Geoffrey and Spray formations, defined here formally for the first time with type sections and detailed descriptions. New interpretations of the geology of these islands demonstrate that previously interpreted major faults do not exist, resulting in stratigraphic and age controls that are both different and simpler than previously interpreted. The redefined stratigraphy of the northern part of the basin is remarkably similar to that of southern areas in both type and age, affirming both a single basin evolution and a single stratigraphic nomenclature.


Monday, 28 January 2019

FOSSIL TRACKWAYS

Ichnofossil Trackways. Photo credit: Luis Lima. Lisbon Museum Collection

Saturday, 26 January 2019

Friday, 25 January 2019

ICHTHYOSAUR VERTEBRAE AND RIBS

A very well preserved ichthyosaur block with three distinct vertebrae and some ribs just peeking out. You can see the edges of the ribs nicely outlined against the matrix.

Ichthyosaurs are an extinct order of marine reptiles from the Mesozoic era. They evolved from land-dwelling, lung-breathing reptiles who returned to our ancient seas and evolved into the fish-shaped creatures we find in the fossil record today.

They were visibly dolphin-like in appearance but seem to share some other qualities as well. These lovelies were warm-blooded and used their coloration as camouflage. The smaller of their lineage to avoid being eaten and the larger to avoid being seen by prey. Ichthyosaurs also had insulating blubber, a lovely adaptation to keep them warm in cold seas.

Over time, their limbs fully transformed into flippers, sometimes containing a very large number of digits and phalanges. Their flippers tell us they were entirely aquatic as they were not well-designed for use on land. It was their flippers that first gave us the clue that they gave birth to live young; a hypothesis later confirmed by fossil embryo and wee baby ichy specimens.

We find their fossil remains in outcrops spanning from the mid-Cretaceous to the earliest Triassic. As we look through the fossils, we see a slow evolution in body design moving towards that enjoyed by dolphins and tuna by the Upper Triassic, albeit with a narrower, more pointed snout.

During the early Triassic period, ichthyosaurs evolved from a group of unidentified land reptiles. They were particularly abundant in the later Triassic and early Jurassic periods before being replaced as a premier aquatic predator by another marine reptilian group, the Plesiosauria, in the later Jurassic and Cretaceous periods. The block you see here is from Middle Triassic (Anisian/Ladinian) outcrops in the West Humboldt Mountains, Nevada.

Thursday, 24 January 2019

Wednesday, 23 January 2019

FOSSIL CROCODILE

Fossil Crocodile, Lisbon Natural History Museum. Photo: Luis Lima
This well-preserved fossil crocodile is around 12 million years old and hails from Chelas, a locality near the airport in Lisbon. This fellow was quite the beast. The complete crocodile would have been 8-9 meters in length.

This specimen is housed in the Geological Museum of Lisbon. The museum was built in 1857 and is home to beautiful paleontology, archaeology and mineral specimens.

Tuesday, 22 January 2019

Monday, 21 January 2019

CHAMPAGNE-ARDENNE HOPLITES

An excellent example of the ammonite, Hoplites bennettiana (Sowby, 1826) with a pathology. This beauty is from Albian deposits near Carrière de Courcelles, Villemoyenne, laid down in the Cretaceous near la région de Troyes (Aube) Champagne in northeastern France.

L'Albien or Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It was named after Alba, the Latin name for the River Aube, a tributary of the Seine that flows through the Champagne-Ardenne region of northwestern France.

The Albian is the youngest or uppermost subdivision of the Lower Cretaceous, approximately 113.0 ± 1.0 Ma to 100.5 ± 0.9 Ma (million years ago).

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. Interesting times.

Hoplites maritimus / Hoplites rudis
Hoplites are amongst my favourite ammonites. I still have a difficult time telling them apart. To the right, you can see a slightly greyish, Hoplites maritimus, from Sussex England. Below him is a brownish Hoplites rudis from outcrops between Courcelles and Troyes, France. There are many Hoplites species. Each has a nicely raised tire-track ribbing. My preference is for Hoplities bennetianus (or bennettiana). I'm still sorting out the naming of that species. The difference between Hoplites bennettiana and Hoplites dentatus is seen on the venter.

Hoplites shells have compressed, rectangular and trapezoidal whorl sections. They have pronounced umbilical bullae from which their prominent ribs branch out. The ends of the ribs can be both alternate or opposite. Some species have zigzagging ribs and these usually end thickened or raised into ventrolateral tubercules.

Ammonites were predatory, squid-like creatures that lived inside coil-shaped shells. Like other cephalopods, ammonites had sharp, beaklike jaws inside a ring of tentacles that extended from their shells to snare prey such as small fish and crustaceans. Some ammonites grew more than three feet (one meter) across — possible snack food for the giant mosasaur Tylosaurus.

Ammonites constantly built new shell as they grew, but only lived in the outer chamber. They scooted through the warm, shallow seas by squirting jets of water from their bodies. A thin, tubelike structure called a siphuncle reached into the interior chambers to pump and siphon air and helped them move through the water.

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. They were prolific breeders, lived in schools, and are among the most abundant fossils found today. They went extinct with the dinosaurs 65 million years ago. Scientists use the various shapes and sizes of ammonite shells that appeared and disappeared through the ages to date other fossils.

Hoplites sp. from the Early Cretaceous of Dorset, UK
During their evolution, three catastrophic events occurred. The first during the Permian period (250million years ago), only 10% survived.  They went on to flourish throughout the Triassic period, but at the end of this period (206 million years ago), all but one species died. Then they began to thrive from the Jurassic period until the end of the Cretaceous period when all species of ammonites became extinct.

Ammonites began life very tiny, less than 1mm in diameter, and were vulnerable to attack from predators. They fed on plankton and quickly assumed a strong protective outer shell. They also grew quickly with the females growing up to 400% larger than the males; because they needed the larger shell for egg production. Most ammonites only lived for two years.  Some lived longer becoming very large. The largest ever found was in Germany (6.5 feet in diameter).

Ammonites lived in shallow waters of 100 meters or less. They moved through the water by jet propulsion expelling water through a funnel-like opening to propel themselves in the opposite direction. They were predators (cephalopods) feeding on most living marine life including mollusks, fish even other cephalopods. Ammonites would silently stalk their prey then quickly extend their tentacles to grab it.  When caught the prey would be devoured by the Ammonites' jaws located at the base of the tentacles between the eyes.

Hoplites dentalus, from Albian deposits near Troyes, France
Most ammonites have coiled shells. The chambered part of the shell is called a phragmocone.  It contains a series of progressively layered chambers called camerae, which were divided by thin walls called septae. The last chamber is the body chamber.

As the ammonite grew, it added new and larger chambers to the opened end of the shell. A thin living tube called a siphuncle passed through the septa, extending from the body to the empty shell chambers.

This allowed the ammonite to empty water out of the shell chambers by hyperosmotic active transport process. This process controlled the buoyancy of the ammonite's shell.

First Photo: Hoplites Bennettiana from near Troyes, France. Collection de Christophe Marot

Second Photo: Top: Hoplites maritimus from Sussex, UK. Bottom: Hoplites rudis from near Troyes, France. Collection of Mark O'Dell

Third Photo: Hoplites sp. from the Early Cretaceous of Dorset, UK. Natural Selection Fossils

Fourth Photo: Hoplites dentalus from Albian deposits near Troyes, France. Collection of Stéphane Rolland.

Wright, C. W. (1996). Treatise on Invertebrate Paleontology, Part L, Mollusca 4: Cretaceous Ammonoidea (with contributions by JH Calloman (sic) and MK Howarth). Geological Survey of America and University of Kansas, Boulder, Colorado, and Lawrence, Kansas, 362.

Amédro, F., Matrion, B., Magniez-Jannin, F., & Touch, R. (2014). La limite Albien inférieur-Albien moyen dans l’Albien type de l’Aube (France): ammonites, foraminifères, séquences. Revue de Paléobiologie, 33(1), 159-279.

Sunday, 20 January 2019

OSTEOLOGIE DU MEGATHERIUM

This lovely illustration of Megatherium, a fossil sloth discovered in South America was published in 1825 by Georges Cuvier as part of his work comparing specimens from South America to those from the Paris Basin.

Jean Louis Denis was the engraver who created this lovely plate. We have Leonard C. Bruno to thank for access to this image. He took black and white photos of the plate and published them in 1987 to the Library of Congress with full open access. Illus. in: Recherches sur les ossemens fossiles / Georges Cuvier. Third ed. Paris: G. Dufour et E. d'Ocagne, 1825, pl. 16. Published in: The tradition of science / Leonard C. Bruno. Washington, D.C. : Library of Congress, 1987, p. 215.

Saturday, 19 January 2019

SLOTHS AND AVOCADOS

In 1788, this magnificent specimen of a Megatherium sloth was sent to the Royal Cabinet of Natural History from the Viceroyalty of Rio de la Plata.

The megaterios were large terrestrial sloths belonging to the group, Xenarthra. These herbivores inhabited large areas of land on the American continent. Their powerful skeleton enabled them to stand on their hind legs to reach leaves high in the trees, a huge advantage given the calories needed to be consumed each day to maintain their large size.

Avocados were one of the food preferences of our dear Giant ground sloths. They ate then pooped them out, spreading the pits far and wide. The next time you enjoy avocado toast, thank this large beastie. One of his ancestors may have had a hand (or butt) in your meal.

In 1788, Bru assembled the skeleton as you see it here. It is exhibited at the Museo Nacional De Ciencias Naturales in Madrid, Spain, in its original configuration for historic value. If you look closely, you'll see it is not anatomically correct. But all good paleontology is teamwork. Based upon the drawings of Juan Bautista Bru, George Cuvier used this specimen to describe the species for the very first time.

Friday, 18 January 2019

Thursday, 17 January 2019

ZENAPIS PODOLICA

A Devonian fish mortality plate showing all lower shields of Zenaspis podolica (Lankester, 1869) and Stensiopelta pustulata (and possibly Victoraspis longicornualis) from Lower Devonian deposits of Podolia, Ukraine.

Zenaspis is an extinct genus of jawless fish which existed during the early Devonian period. Due to it being jawless, Zenaspis was probably a bottom feeder.

The lovely 420 million-year-old plate you see here is from Podolia or Podilia, a historic region in Eastern Europe, located in the west-central and south-western parts of Ukraine, in northeastern Moldova. Podolia is the only region in Ukraine where Lower Devonian remains of ichthyofauna can be found near the surface.

For the past 150 years, vertebrate fossils have been found in more than 90 localities situated in outcrops along banks of the Dniester River and its northern tributaries, and in sandstone quarries. At present faunal list of Early Devonian agnathans and fishes from Podolia number 72 species, including 8 Thelodonti, 39 Heterostraci, 19 Osteostraci, 4 Placodermi, 1 Acanthodii, and 1 Holocephali (Voichyshyn 2001a, modified).

In Podolia, Lower Devonian redbeds strata (the Old Red Formation or Dniester Series) can be found up to 1800 m thick and range from Lochkovian to Eifelian in age (Narbutas 1984; Drygant 2000, 2003). In the lower part (Ustechko and Khmeleva members of the Dniester Series) they consist of multicoloured, mainly red, fine-grained cross-bedded massive quartz sandstones and siltstones with seams of argillites (Drygant 2000).

We see fossils beds of Zenaspis in the early Devonian of Western Europe. Both Zenaspis pagei and Zenaspis poweri can be found up to 25 centimetres long in Devonian outcrops of Scotland.

Reference: Voichyshyn, V. 2006. New osteostracans from the Lower Devonian terrigenous deposits of Podolia, Ukraine. Acta Palaeontologica Polonica 51 (1): 131–142. Photo care of Fossilero Fisherman.

Wednesday, 16 January 2019

THE LAST ICE AGE

The massive ice sheets of the Pleistocene covered much of the planet. They contained so much of the Earth's water that sea levels dropped to 100 metres lower than they are today.

Tuesday, 15 January 2019

FIRST ITALIAN FOSSILS OF AGRIOTHERIUM

Agriotherium / Short-Faced Bear
Fossil remains of Agriotherium, the short-faced giant bear, have been found in Collepardo, Italy. A fragment of a mandible was unearthed back in 2015 in the province of Frosinone. Thanks to several years of research and a recent CT scan, the team from Sapienza University of Rome were finally ready to publish.

Agriotherium is one of the largest of the mighty carnivores that lived in Europe back in the Pleistocene. They weighed as much as 900 kilos (almost 2,000 lbs) and grew up to 2.5 meters tall. These ancient bears roamed prehistoric Italy amid a humid and temperate climate, competing for food resources with some of our ancestors as they only becoming extinct 2.6 million years ago.

Monday, 14 January 2019

CAMBRIAN SEA ANEMONE

A stunning Cambrian soft-bodied Sea Anemone from outcrops near Malong, China. Collection of Marc R. Hänsel

Sunday, 13 January 2019

PREHISTORIC BUGS: WANNERIA DUNNAE

Wanneria dunnae, an impressive trilobite from British Columbia's Eager Formation near Cranbrook. Trilobites were among the earliest fossils with hard skeletons. They were the dominant form of life at the beginning of the Cambrian Period. This specimen of Wanneria dunnae from the East Kootenay of British Columbia is typical of the group. Trilobite eyes were compound like those of modern crustaceans and insects. The eyes of these earliest trilobites are not well-known as the visual surface dropped away and was lost during molting long before they ever became fossils.

Saturday, 12 January 2019

Friday, 11 January 2019

IRIDESCENT EUHOPLITES

A beautiful Euhoplites ammonite from Folkstone, 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. They look to have been a source of hydrodynamic drag, preventing Euhoplites from swimming at high speeds. Studying them may give some insight into the lifestyle of this ancient marine predator. Euhoplites had shells ranging in size up to a few inches.
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. It is the most common ammonite fossil of 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.

Thursday, 10 January 2019

FIRE-KISSED ARTHROPOD

This fellow is Chengjiangocaris kunmingensis, a rather glorious fuxinhuiid arthropod. While he looks like he could be from the inside of the Lascaux Caves and their fire-kissed Palaeolithic paintings, albeit by a very ancient Picasso, he was found at a Cambian fossil site in southern China.

As his name indicates, he is from a fossil site in the Yunnan region near Kunming. He is unusual in many ways, both because of the remarkable level of preservation and the position in which he was found. This fellow was a bit of a tippy arthropod. His carapace had flipped over before fossilisation, allowing researchers to to examine this fuxianhuiid's head and legs in great detail without a carapace in the way.

The roughly 518-million-year-old site contains a dizzying abundance of beautifully preserved weird and wonderful life-forms, from jellyfish and comb jellies to arthropods and algae and is about 10 million years older than the Burgess Shale. Photo credit: Yie Jang (Yunnan University)

Wednesday, 9 January 2019

Tuesday, 8 January 2019

WASH ON, WASH OFF

If you were a fish living in the warm turquoise waters off the coast of Bonaire, you may not hear those words, but you'd see the shrimp sign language equivalent. It seems Periclimenes yucatanicus or Spotted Cleaner Shrimp is doing a booming business in the local reefs by setting up a fish washing service.

That's right, a Fish Wash. You'd be hard pressed to find a terrestrial Molly Maid with two opposable thumbs as studious and hardworking as this wee marine beauty.

This quiet marine mogul is turning out to be one of the ocean's top entrepreneurs. Keeping its host and diet clean and green, the spotted shrimp hooks up with the locals, in this case, local sea anemones and sets up a fish wash. Picture a car wash but without the noise and teenage boys. The signage posted is the shrimps' natural coloring which attracts fish from around the reefs.

Wash on, wash off.

Once within reach, the shrimp cleans the surface of the fish, giving the fish a buff and the shrimp its daily feed.

Monday, 7 January 2019

FRATERCULA ARCTICA

This lovely fellow is a Puffin or "Sea Parrot" from Skomer Island near Pembrokshire in Wales. They live about 20 years making a living in our cold seas dining on herring, hake and sand eels.

They are good little swimmers as you might expect but surprisingly they are great flyers, too! Once they get some speed on board, they can fly up to 88 km an hour. The sexy orange beak (dead sexy, right?) shifts from a dull grey to bright orange when it is time to attract a mate. While not strictly monogamous, most Puffin choose the same mate year upon year producing adorable chicks or pufflings (awe) from their mating efforts.

Sunday, 6 January 2019

ICHTHYOSAURIA

Ichthyosaurus was an extinct marine reptile first described from fossil fragments found in 1699 in Wales. Shortly thereafter, fossil vertebrae were published in 1708 from the Lower Jurassic.

Saturday, 5 January 2019

HOLCOPHYLLOCERAS MEDITERRANEUM

This lovely ammonite is Holcophylloceras mediterraneum (Neumayr 1871) from Late Jurassic (Oxfordian) deposits near Sokoja, Madagasgar.

Amazing suturing on this lovely ammonite and great detail, allowing us to see how he grew, adding to his size, chamber by chamber, building out his spiral shape.

Ammonite shells had many chambers divided by walls called septa. Nautiloids had simple septa with a single arc whereas ammonites developed septa with intricate folds, lobes and saddles. They also developed delicate feather-like or fern-like lacey patterns, called sutures, on the outer shell. You sometimes see them on polished or water worn specimens and in the photos of this fellow below.

The chambers were connected by a tube called a siphuncle which allowed for the control of buoyancy with the hollow inner chambers of the shell acting as air tanks to help them float. A bit like internal water wings you might use to learn how to swim as a kid.

We can see the edges of this specimen's shell where it would have continued out to the last chamber, the body-chamber, where the ammonite lived. Picture a squid or octopus, now add a shell. That's him!

Friday, 4 January 2019

MEGALODON TOOTH

Carcharocles chubutensis, which roughly translates to the "glorious shark of Chubut," from the ancient Greek is an extinct species of prehistoric mega-toothed sharks in the genus Carcharocles.

These big beasties lived during Oligocene to Miocene. This fellow is considered to be a close relative of the famous prehistoric mega-toothed shark, C. megalodon, although the classification of this species is still disputed.

Swiss naturalist Louis Agassiz first identified this shark as a species of Carcharodon in 1843. In 1906, Ameghino renamed this shark as C. chubutensis. In 1964, shark researcher, L. S. Glikman recognized the transition of Otodus obliquus to C. auriculatus. In 1987, shark researcher, H. Cappetta reorganized the C. auriculatus - C. megalodon lineage and placed all related mega-toothed sharks along with this species in the genus Carcharocles.

At long last, the complete Otodus obliquus to C. megalodon progression began to look clear. Since then, C. chubutensis has been re-named into Otodus chubutensis, also the other chronospecies of the Otodus obliquus - O. megalodon lineage. Chubutensis appears at the frontier Upper Oligocene to Lowest Miocene (evolving from O. angustidens which has stronger side cusps) and turns into O. megalodon in the Lower to Middle Miocene, where the side cusps are already absent. Despite previous publications, there is no chubutensis in the Pliocene.

Victor Perez and his team published on the transition between Carcharocles chubutensis and Carcharocles megalodon (Otodontidae, Chondrichthyes): lateral cusplet loss through time in March of 2018. In their work, they look at the separation between all the teeth of Carcharocles chubutensis and Carcharocles megalodon and published that it is next to impossible to divide them up as a complex mosaic evolutionary continuum characterizes this transformation, particularly in the loss of lateral cusplets.

The cuspleted and uncuspleted teeth of Carcharocles spp. are designated as chronomorphs because there is wide overlap between them both morphologically and chronologically. In the lower Miocene Beds (Shattuck Zones) 2–9 of the Calvert Formation (representing approximately 3.2 million years, 20.2–17 Ma, Burdigalian) both cuspleted and uncuspleted teeth are present, but cuspleted teeth predominate, constituting approximately 87% of the Carcharocles spp. teeth represented in their samples.

In the middle Miocene Beds 10–16A of the Calvert Formation (representing approximately 2.4 million years, 16.4–14 Ma, Langhian), there is a steady increase in the proportion of uncuspleted Carcharocles teeth.

In the upper Miocene Beds 21–24 of the St. Marys Formation (representing approximately 2.8 million years, 10.4–7.6 Ma, Tortonian), lateral cusplets are nearly absent in Carcharocles teeth from our study area, with only a single specimen bearing lateral cusplets. The dental transition between Carcharocles chubutensis and Carcharocles megalodon occurs within the Miocene Chesapeake Group. Although their study helps to elucidate the timing of lateral cusplet loss in Carcharocles locally, the rationale for this prolonged evolutionary transition remains unclear.

The specimen you see here is in the Geological Museum in Lisbon. The photo credit goes to the deeply awesome Luis Lima who shared some wonderful photos of his recent visit to their collections.

If you'd like to read the paper from Perez, you can find it here:
https://www.tandfonline.com/doi/full/10.1080/02724634.2018.1546732

Thursday, 3 January 2019

MEGALOSAURUS BUCKLANDII

Oxford University Museum of Natural History was established in 1860 to draw together scientific studies from across the University of Oxford. Today, the award-winning Museum continues to be a place of scientific research, collecting and fieldwork and plays host to a number of programmes and exhibitions.

Notable collections include the world's first described dinosaur, Megalosaurus bucklandii, and the world-famous Oxford Dodo, the only soft tissue remains of the extinct dodo. Although fossils from other areas have been assigned to the genus, the only certain remains of Megalosaurus come from Oxfordshire and date to the late Middle Jurassic. In 1824, Megalosaurus was the first genus of non-avian dinosaur to be validly named. The type species is Megalosaurus bucklandii, named in 1827.

In 1842, Megalosaurus was one of three genera on which Richard Owen based his Dinosauria. On Owen's direction, a model was made as one of the Crystal Palace Dinosaurs, which greatly increased the public interest for prehistoric reptiles. Subsequently, over fifty other species would be classified under the genus, originally because dinosaurs were not well known, but even during the 20th century after many dinosaurs had been discovered. Today it is understood these additional species were not directly related to M. bucklandii, which is the only true Megalosaurus species. Because a complete skeleton of it has never been found, much is still unclear about its build.

The Museum is as spectacular today as when it opened in 1860. As a striking example of Victorian neo-Gothic architecture, the building's style was strongly influenced by the ideas of 19th-century art critic John Ruskin. Ruskin believed that architecture should be shaped by the energies of the natural world, and thanks to his connections with a number of eminent Pre-Raphaelite artists, the Museum's design and decoration now stand as a prime example of the Pre-Raphaelite vision of science and art.

On 30 June 1860, the Museum hosted a clash of ideologies that has become known as the Great Debate. Even before the collections were fully installed, or the architectural decorations completed, the British Association for the Advancement of Science held its 30th annual meeting to mark the opening of the building, then known as the University Museum. It was at this event that Samuel Wilberforce, Bishop of Oxford, and Thomas Huxley, a biologist from London, went head-to-head in a debate about one of the most controversial ideas of the 19th century – Charles Darwin's theory of evolution by natural selection.

Wednesday, 2 January 2019

ALSACE AMMONITE

A lovely example of the nautilus, Cératite Nodosus, from Shell Lime Superior deposits near Alsace in northeastern France on the Rhine River plain. Ammonite and nautilus shells are made up predominantly of calcium carbonate in the form of aragonite and proteinaceous organic matrix or conchiolin arranged in layers: a thin outer prismatic layer, a nacreous layer and an inner lining of prismatic habitat. While their outer shells are generally aragonite, aptychus are distinct as they are composed of calcite.


The aptychus we see here, hard anatomical structures or curved shelly plates now understood to be part of the body of an ammonite or nautilus, are often referred to as beaks. If you look closely at this specimen, you can see the beak of the nautilus, that wee pointed piece, near the centre. Collection of Ange Mirabet, Strasbourg, France.


Tuesday, 1 January 2019