STELLAR SEA COW

This adorable aquatic vacuum is a dugong. I had always grouped the dugongs and manatees together. There are slight differences between these two but both belong to the order Sirenia. 

They shared a cousin in the Steller's sea cow, Hydrodamalis gigas, but that piece of their lineage was hunted to extinction by our species in the 18th century. 

Dugongs have tail flukes with pointed tips — similar to whales — and manatees have paddle-shaped tails, similar to a Canadian Beaver.

Both of these lovelies from the order Sirenia went from terrestrial to marine, taking to the water in search of more prosperous pastures, as it were. They are the extant and extinct forms of the oddball manatees and dugongs.

We find dugongs today in waters near northern Australia and parts of the Indian and Pacific Oceans. 

They inhabit rivers and shallow coastal waters, making the best use of their fusiform bodies that lack dorsal fins and hind limbs. I have been thinking about them in the context of some of the primitive armoured fish we find in the Chengjiang biota of China, specifically those primitive species that were also fusiform.

They favour locations where seagrass, their food of choice, grows plentiful and they eat it roots and all. While seagrass low in fibre, high in nitrogen, and easily digestible is preferred, dugongs will also dine on lower grade seagrass, algae, and invertebrates should the opportunity arise. They have been known to eat jellyfish, sea squirts, and shellfish over the course of their long lives. 

Some of the oldest dugongs have been known to live 70+ years, which is another statistic I find surprising. They are large, passive, have poor eyesight, and look pretty tasty floating in the water; a defenceless floating buffet. Their population is in decline and yet they live on.

DUGONG: SIRENIA

One of the most delightful creatures to ever grace this planet is the dugong — a species of sea cow found throughout the warm latitudes of the Indian and western Pacific Oceans. 

It is one of four living species of the order Sirenia, which also includes three species of manatees — their large, fully aquatic, mostly herbivorous marine mammal cousins.

The closest living relatives of sirenians are elephants. Manatees evolved from the same land animals as elephants over 50 million years ago. If not for natural selection, we might have a much more diverse showing of the Sirenia as their fossil lineage shows a much more diverse group of sirenians back in the Eocene than we have today. 

It is the only living representative of the once-diverse family Dugongidae; its closest modern relative, Steller's sea cow, was hunted to extinction in the 18th century. 

While only one species of the dugong is alive today – a second, the Steller's sea cow only left this Earth a few years ago. Sadly, it was hunted to extinction within 27 years of its discovery – about 30 species have been recovered in the fossil record

The first appearance of sirenians in the fossil record was during the early Eocene, and by the late Eocene, sirenians had significantly diversified. Inhabitants of rivers, estuaries, and nearshore marine waters, they were able to spread rapidly.

The most primitive sirenian known to date, Prorastomus, was found in Jamaica, not the Old World; however, more recently the contemporary Sobrarbesiren has been recovered from Spain. The first known quadrupedal sirenian was Pezosiren from the early Eocene. The earliest known sea cows, of the families Prorastomidae and Protosirenidae, are both confined to the Eocene and were about the size of a pig, four-legged amphibious creatures. By the time the Eocene drew to a close, the Dugongidae had arrived; sirenians had acquired their familiar fully aquatic streamlined body with flipper-like front legs with no hind limbs, powerful tail with horizontal caudal fin, with up and down movements which move them through the water, like cetaceans.

The last of the sirenian families to appear, Trichechidae, apparently arose from early dugongids in the late Eocene or early Oligocene. The current fossil record documents all major stages in hindlimb and pelvic reduction to the extreme reduction in the modern manatee pelvis, providing an example of dramatic morphological change among fossil vertebrates.

Since sirenians first evolved, they have been herbivores, likely depending on seagrasses and aquatic angiosperms, tasty flowering plants of the sea, for food. To the present, almost all have remained tropical (with the notable exception of Steller's Sea Cow), marine, and angiosperm consumers. Sea cows are shallow divers with large lungs. They have heavy skeletons to help them stay submerged; the bones are pachyostotic (swollen) and osteosclerotic (dense), especially the ribs which are often found as fossils.

Eocene sirenians, like Mesozoic mammals but in contrast to other Cenozoic ones, have five instead of four premolars, giving them a 3.1.5.3 dental formula. Whether this condition is truly primitive retention in sirenians is still under debate.

Although cheek teeth are relied on for identifying species in other mammals, they do not vary to a significant degree among sirenians in their morphology but are almost always low-crowned —brachyodont — with two rows of large, rounded cusps — bunobilophodont. The most easily identifiable parts of sirenian skeletons are the skull and mandible, especially the frontal and other skull bones. With the exception of a pair of tusk-like first upper incisors present in most species, front teeth — incisors and canines — are lacking in all, except the earliest sirenians.

SERENGETI OF TEXAS

Eighty years ago, during the Great Depression, unemployed Texans were put to work as fossil hunters. 

The fossils collecting program was part of the State-Wide Paleontologic-Mineralogic Survey that was funded by the Works Progress Administration (WPA), a federal agency that provided work to millions of Americans during the Great Depression. 

From 1939 to 1941, the agency partnered with the UT Bureau of Economic Geology, which supervised the work and organized field units for collecting fossils and minerals across the state. Despite lasting only three years, the program was responsible for the excavation of thousands of fossils from across Texas including four dig sites in Bee and Live Oak counties, with the majority of their finds housed in what is now the Texas Vertebrate Paleontology Collections at the Jackson School Museum of Earth History. 

If you are like me, this sounds like a wonderful idea and work akin to paradise. You will be shocked to know that there were grumblings of malcontent by some of the workers. And yet, happy or sad, those lovely folk unearthed tens of thousands of specimens 80 years ago that only now are being studied in their complete context. 

The collection is housed in the state collections of The University of Texas at Austin and for the past few years, Steven May, a UT researcher, has been poking through those drawers with a special interest in specimens from dig sites near Beeville, Texas. 

Over the years, a number of scientific papers have been published on select groups of WPA specimens. But May's paper is the first to study the entire fauna. This extensive collection of fossils is helping to fill in gaps in the state's ancient environment.

The fauna from this area paints a picture of our modern-day Serengeti — with specimens including elephant-like animals, rhinos, alligators, antelopes, camels, 12 types of horses and several species of carnivores. In total, the fossil trove contains nearly 4,000 specimens representing 50 animal species, all of which roamed the Texas Gulf Coast 11 million to 12 million years ago.

In addition to shedding light on the inhabitants of an ancient Texas ecosystem, the collection is also valuable because of its fossil firsts. They include a new genus of gomphothere, an extinct relative of elephants with a shovel-like lower jaw, and the oldest fossils of the American alligator and an extinct relative of modern dogs.

The emphasis on big mammals is due in large part to the collection practices of the fossil hunters, most of whom were not formally trained in palaeontology. Large tusks, teeth and skulls were easier to spot — and more exciting to find — than bones left by small species.

"They collected the big, obvious stuff," May said. "But that doesn't fully represent the incredible diversity of the Miocene environment along the Texas Coastal Plain."

In order to account for gaps in the collection, May tracked down the original dig sites so he could screen for tiny fossils such as rodent teeth. One of the sites was on a ranch near Beeville owned by John Blackburn. Using aerial photography and notes from the WPA program stored in the university's archives, May and the research team were able to track down the exact spot of an original dig site.

"We're thrilled to be a part of something that was started in 1939," Blackburn said. "It's been a privilege to work with UT and the team involved, and we hope that the project can help bring additional research opportunities."

Reference: Steven R. May. The Lapara Creek Fauna: Early Clarendonian of south Texas, USA. Palaeontologia Electronica, 2019 DOI: 10.26879/929

MESOZOIC BIRDS OF THE JEHOL BIOTA

The Fossil Birds of the Jehol Biota have caused an international stir amongst palaeontologists. The Jehol outcrops of northeastern China has unearthed some of the most important Mesozoic bird specimens worldwide over the past two decades.

This is a tale of how that all began. Back in November 1993, Chinese palaeontologists Hou Lianhai and Hu Yoaming, of the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing received a call from an excited local fossil collector.

He claimed to have quite a remarkable specimen on his hands. The team visited Zhang He at his home in Jinzhou, or Chinchow, a coastal prefecture-level city in central-west Liaoning province

Zhang showed them a spectacular fossil bird specimen he'd recently purchased at a local flea market. Very little was known about the specimen but it was clearly important and the team was hopeful more of this paleo goodness might turn up.

They didn't have that long to wait. A month after his visit to Zhang, Hou learned about a second specimen discovered by a local farmer, Yang Yushan. Things were looking up. Best of all, he learned that both specimens were likely from the same locality in Shangyuan, Beipiao. This was not a one-off discovery or an amazing but anonymous find. With two specimens to compare, the locality determined, the possibility of an interesting publication and career advancement would be a reality.

In 1995, the two specimens, as well as a third, were formally described as a new genus and species, Confuciusornis sanctus, by Hou and colleagues. The generic name combines the philosopher Confucius with a Greek ὄρνις, (ornis), "bird". The specific name means "holy one" in Latin and is a translation of Chinese 圣贤, shèngxián, "sage", again in reference to Confucius.

The first discovered specimen was designated the holotype and catalogued under the specimen number IVPP V10918; it comprises a partial skeleton with skull and parts of the forelimb.

Of the other two skeletons, one (paratype, IVPP V10895) comprises a complete pelvis and hind limb, and the other (paratype, IVPP V10919–10925) a fragmentary hind limb together with six feather impressions attached to both sides of the tibia or shin bone.

All was well until those reading the journal articles realized that the two paratype specimens only comprise bones that were unknown from the holotype. An oversight, likely by design, but this lack of overlap between the specimens made their referral to the species speculative. The lack of overlap also gave a wide margin for error in the naming of additional, albeit hopeful, new species names — names that would later need to be amended. Luckily, the discovery of a veritable treasure trove of well-preserved specimens shortly after confirmed that the specimens indeed represented a single species.

Together with the early mammal Zhangheotherium, which was discovered about the same time, Confuciusornis was considered the most remarkable fossil discovery of the Jehol biota.

It has also given us another fossil-rich Lagerstätte that includes a wonderful mix of advanced and ancient species. My speculation is that northeast Asia was isolated for part of the Jurassic by the Turgai Sea that separated Europe from Asia at that time. The fossils at Jehol are numerous and exceptionally well preserved. Think of the Cambrian goodies at Burgess or the Altmühltal Formation, Jurassic Konservat-Lagerstätte at Solnhofen. Quite remarkably, fully articulated skeletons, soft tissues, colour patterns, stomach contents, and twigs with leaves and flowers still attached, can be found within the Jehol biota.

A beautifully preserved Archaeopteryx

In the late 1990s, Confuciusornis was considered both the oldest beaked bird as well as the most primitive bird after Archaeopteryx. It was also considered to be only slightly younger than Archaeopteryx. 

Yixian Formation, the rock unit where most Confuciusornis specimens have been found, was thought to be of Late Jurassic (Tithonian) age at the time.

Although two bird genera, Sinornis and Cathayornis, had already described from the Jehol biota back in 1992, these were based on fragmentary remains and stem from the younger Jiufotang Formation. At the time, the Jiufotang was thought to be Early Cretaceous. Both formations have since been dated to the Lower Cretaceous — Barremian to Aptian — 131–120 million years ago.

In 1995, local farmers began digging for fossils near the village of Sihetun, Beipiao, in what would become one of the most productive localities of the Jehol biota. The then largely unknown site is truly world-class. Large-scale professional excavations at this single locality have been carried out by the IVPP from 1997 onwards. Not one, not two, but several hundred specimens of Confuciusornis have now been unearthed from here. Many additional sites producing fossils of the Jehol biota have been recognized since, distributed over a large region including Liaoning, Hebei, and Inner Mongolia.

Due to the great abundance, preservation, and commercial value of the fossils, excavations by local farmers produced an unusually high number of fossils. Although some of these fossils have been added to the collections of Chinese research institutions, more have been smuggled out of the country.

In 1999, it was estimated that the National Geological Museum of China in Beijing housed nearly a hundred (100) specimens of Confuciusornis, and in 2010, the Shandong Tianyu Museum of Nature was reported to possess five hundred and thirty-six (536) specimens. While it is illegal to export them, the majority of specimens are still held privately and thus are not available for research. I see them on social media and occasionally they come up for sale on eBay.

At one time forty individuals were discovered on a surface of about 100 m2. This unusual bone bed was likely the result of an entire flock of birds being simultaneously killed by ash, heat or poisonous gas following the volcanic eruptions that caused the tuff stone in which the fossils were found to be deposited as lake sediments. An avian death bed is highly unusual. Very sad for our feathered friends but grateful for what has been revealed by this rare event.

Notes: Confuciusornis chuonzhous was named by Hou in 1997 based on specimen IVPP V10919, originally a paratype of Confuciusornis sanctus. The specific name refers to Chuanzhou, an ancient name for Beipiao. Confuciusornis chuonzhous is now generally considered synonymous with Confuciusornis sanctus.

Confuciusornis suniae, named by Hou in the same 1997 publication, was based on specimen IVPP V11308. The specific name honours Madam Sun, the wife of Shikuan Liang who donated the fossil to the IVPP. Confuciusornis suniae is now usually considered synonymous with Confuciusornis sanctus.

Reference: Zhou, Z; Hou, L. (1998). "Confuciusornis and the early evolution of birds". Vertebrata PalAsiatica. 36 (2): 136–146.

Zhou, Z. (2006). "Evolutionary radiation of the Jehol Biota: chronological and ecological perspectives". Geological Journal. 41 (3–4): 377–393. doi:10.1002/gj.1045.

SNAILS, SLUGS AND LIMPETS

Gastropods are the largest and most successful class of molluscs. They started as exclusively marine but have adapted well and now their rank spends more time in freshwater than in salty marine environments.

Many are marine, but two-thirds of all living species live in freshwater or on land. Their entry into the fossil record goes all the way back to the Cambrian.

Slugs and snails, abalones, limpets, cowries, conches, top shells, whelks, and sea slugs are all gastropods. They are the second-largest class of animals with over 60,000 – 75,000 known living species.

The gastropods are originally sea-floor predators, though they have evolved to live happily in many other habitats. Many lines living today evolved in the Mesozoic. The first gastropods were exclusively marine and appeared in the Upper Cambrian — Chippewaella and Strepsodiscus.

By the Ordovician, gastropods were a varied group present in a variety of aquatic habitats. Commonly, fossil gastropods from the rocks of the early Palaeozoic era are too poorly preserved for accurate identification. Still, the Silurian genus Poleumita contains fifteen identified species.

Most of the gastropods of the Palaeozoic era belong to primitive groups, a few of which still survive today. By the Carboniferous, many of the shapes we see in living gastropods can be matched in the fossil record, but despite these similarities in appearance the majority of these older forms are not directly related to living forms. It was during the Mesozoic era that the ancestors of many of the living gastropods evolved.

In Mesozoic rocks, gastropods are more common as fossils and their shells often very well preserved. While not all gastropods have shells, the ones that do fossilize more easily and consequently, we know a lot more about them. We find them in fossil beds from both freshwater and marine environments, in ancient building materials and as modern guests of our gardens.

FOSSIL FUELS AND THE EARTH'S MASS

A bright, beautiful young mind asked the question, "does Earth's mass decrease when we burn fossil fuels? And if it does, is it measurable? Do we know how much of the Earth’s mass has been lost so far?"

Well, Melaina, the Earth’s mass does decrease when fossil fuels are burnt. But not in the sense you were probably imagining, and only to a very, very small degree.

There is no decrease in chemical mass. Burning fossil fuels rearranges atoms into different molecules, in the process releasing energy from chemical bonds, but in the end, the same particles — protons, neutrons, and electrons — remain, so there is no decrease in mass there.

But energy is released, and some of that energy is radiated out into space, escaping from the Earth entirely. Einstein's Theory of Relativity tells us that energy does have mass: E=mc^2, or m=E/c^2. When a chemical bond that stores energy is formed, the resulting molecule has a very tiny bit more mass than the sum of the masses of the atoms from which it was formed, so a net gain. Wait, what?

Again, this is an exceedingly tiny bit. In very rough numbers, worldwide energy consumption is about 160,000 terawatt-hours per year, and about 80% of that comes from fossil fuels. That is about 450,000,000 TJ/year (tera-joules/year). The speed of light is 300,000,000 meter/s; dividing 450,000,000 TJ by (300,000,000 m/s)^2 gives a decrease in mass of 5000 kilograms per year.

That is an exceedingly small fraction — 50 billionths of one percent — of the approximately 10,000,000,000,000 kilograms of fossil fuels consumed per year. And as far as making the Earth lighter, it’s a tenth of a billionth of a billionth of a percent of the Earth’s mass.

Of course, the energy in fossil fuels originally came from the Sun, and in absorbing that sunlight the Earth’s mass increases slightly. I picture the Earth expanding and contracting, taking a deep breath, then exhaling. We don't see this when we look, but it is a great visual for imaging this never-ending give and take process. I'm not sure how we'd measure the small changes to the Earth's net mass on any given day. The mass of the Earth may be determined using Newton's law of gravitation. It is given as the force (F), which is equal to the Gravitational constant multiplied by the mass of the planet and the mass of the object, divided by the square of the radius of the planet.

Newton's insight on the inverse-square property of gravitational force was from an intuition about the motion of the earth and the moon. The mathematical formula for gravitational force is F=GMmr2 F = G Mm r 2 where G is the gravitational constant. I know, Newton’s law could use some curb appeal but it is super useful when understanding what keeps the Earth and other planets in our solar system in orbit around the Sun and why the Moon orbits the Earth. We have Newton to thank for his formulas on the gravitational potential of water when we build hydroelectricity dams. Newton’s ideas work in most but not all scenarios. When things get very, very small, or cosmic, gravity gets weird... and we head on back to Einstein to make sense of it all.

There was a very cool paper published yesterday by King Yan Fong et al. in the journal Nature that looked at heat transferring in a previously unknown way — heat transferred across a vacuum by phonons — tiny, atomic vibrations. The effect joins conduction, convection and radiation as ways for heating to occur — but only across tiny distances. The heat is transferred by phonons — the energy-carrying particles of acoustic waves, taking advantage of the Casimir effect, in which the quantum fluctuations in the space between two objects that are really, really close together result in physical effects not predicted by classical physics. This is another excellent example of the universe not playing by conventional rules when things get small. Weird, but very cool!

But the question was specifically about the mass of the Earth and the burning of fossil fuels, and that process does decrease the mass.

So it is mostly true that the Earth’s mass does not decrease due to fossil fuel burning because the numbers are so low, but not entirely true. The fuel combines with oxygen from the atmosphere to produce carbon dioxide, water vapour, and soot or ash. The carbon dioxide and water vapour go back into the atmosphere along with some of the soot or ash, the rest of which is left as a solid residue. The weight of the carbon dioxide plus the water vapour and soot is exactly the same as the weight of the original fuel plus the weight of the oxygen consumed. In general, the products of any chemical reaction whatsoever weigh the same as the reactants.

There is only one known mechanism by which Earth’s mass decreases to any significant degree: molecules of gas in the upper atmosphere (primarily hydrogen and helium, because they are the lightest) escape from Earth’s gravity at a steady rate due to thermal energy. This is counterbalanced by a steady rain of meteors hitting Earth from outer space (if you ever want to hunt them, fly a helicopter over the frozen arctic, they really stand out), containing mostly rock, water, and nickel-iron. These two processes are happening all the time and will continue at a steady rate unchanged by anything we humans do. So, the net/net is about the same.

So, the answer is that the Earth's mass is variable, subject to both gain and loss due to the accretion of in-falling material (micrometeorites and cosmic dust), and the loss of hydrogen and helium gas, respectively. But, drumroll please, the end result is a net loss of material, roughly 5.5×107 kg (5.4×104 long tons) per year.

The burning of fossil fuels has an impact on that equation, albeit a very small one, but an excellent question to ponder. A thank you and respectful nod to Les Niles and Michael McClennen for their insights and help with the energy consumption figures.

DOUVILLEICERAS MAMMILLATUM

Some lovely examples of Douvilleiceras mammillatum (Schlotheim, 1813), ammonites from the Lower Cretaceous (Middle-Lower Albian) Douvilliceras inequinodum zone of Ambarimaninga, Mahajanga Province, Madagascar.

The genus Douvilleiceras range from Middle to Late Cretaceous and can be found in Asia, Africa, Europe and North and South America. 

We have beautiful examples in the early to mid-Albian from the archipelago of Haida Gwaii in British Columbia. Joseph F. Whiteaves was the first to recognize the genus from Haida Gwaii when he was looking over the early collections of James Richardson and George Dawson. The beauties you see here measure 6cm to 10cm.

HOPLITES: TIRE-TRACK RIBBING

Hoplites Bennettiana, Troyes, France

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.

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).

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.

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. 

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 the typical 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 centre but I still find the distinctions subtle.

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 tubercles.

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

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

ABUNDANCE TO EXTINCTION: THE AMMONITES

Early Cretaceous Hoplites sp. Dorset, UK

Ammonites were predatory, squid-like creatures that lived inside coil-shaped shells. 

Like other cephalopods, ammonites had sharp, beak-like 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.

These sea creatures were constantly building new shell as they grew. 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. Most of the shell was unused as they preferred to inhabit only the outer 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 the water out of the shell chambers by hyperosmotic active transport process. This process controlled the buoyancy of the ammonite's shell. 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.

They first appeared about 240 million years ago, though they descended from straight-shelled cephalopods called bacrites that date all the way back to the Devonian — some 415 million years. 

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.

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 molluscs, 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.

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

Photo Two: 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.

AVIAN RELATIONS

Although most of the skeletal features differentiating birds from other extant vertebrates can be traced back to the Mesozoic dinosaurs (Makovicky; Zanno, 2011; Xu et al., 2014a), the integration of the fossil record of stem-avians — all taxa closer to birds than crocodiles — with the developmental biology of living birds is more controversial.

The evolution of the three-fingered hand of birds from the ancestral pentadactyl condition of tetrapods is still debated, the former having been considered alternatively as homologous to the medial most three (I–II–III) or the central (II–III–IV) fingers of reptiles (Wagner & Gauthier, 1999; Bever, Gauthier & Wagner, 2011; Xu et al., 2014a).

This controversy has often been depicted as a dichotomy between a paleontological approach supporting the I–II–III pattern in three-fingered theropods, Tetanurans, and a developmental approach supporting the II–III–IV pattern based on the topology of the embryonic mesenchymal condensations from which the avian digits develop (Wagner & Gauthier, 1999).

Yet, both fossil and embryological data are involved in the two alternative interpretations (Bever, Gauthier & Wagner, 2011; Vargas et al., 2008; Xu et al., 2009; Tamura et al., 2011), and may eventually support additional, more complex, homology frameworks (Xu et al., 2014a). Pivotal among the fossil evidence, the unusual hand of the Late Jurassic ceratosaurian Limusaurus has been argued to support a II–III–IV digital identity in birds and a complex pattern of homeotic transformations in three-fingered, Tetanuran, theropods (Xu et al., 2009; Bever, Gauthier & Wagner, 2011), although criticism to this interpretation has been raised from both paleontological and developmental perspectives (Wang et al., 2011; Carrano & Choiniere, 2016).

Following the reinterpretation of the digital identity along the avian stem of Xu et al. (2009), a series of paleontological studies in the last decade used the II–III–IV homology pattern as a morphological framework for three-fingered theropods, challenging the I–II–III pattern traditionally followed in the interpretation of the theropod hand (Xu, Han & Zhao, 2014b). It must be remarked that the evolutionary scenario supporting the II–III–IV homology pattern of Xu et al. (2009) makes predictions that can be falsified in the fossil record (Bever, Gauthier & Wagner, 2011): the phalangeal formula at the root of Ceratosauria should be markedly simplified, compared to the ancestral theropod formula (i.e., 0-3-3/2-1-X vs 2-3-4-1-0).

The new ceratosaurian theropod, Saltriovenator zanellai, from the Saltrio Formation, Lower Jurassic, Lower Sinemurian, ∼198 million-year-old outcrops of Northern Italy (Dal Sasso, 2003), show a mosaic of features seen in four-fingered theropods and in basal tetanurans. Although fragmentary, the new theropod allows the reconstruction of the ancestral ceratosaurian hand, shedding light on the evolutionary digit pattern in tetanuran fingers and thus along the lineage leading to bird origin. The occurrence of large averostran theropods in the fossil record also helps us to understand the body size of this new Italian specimen and its stratigraphic and geochronological context.

The new find, in the context of Early Jurassic neotheropods Skeletal remains of theropod dinosaurs are extremely rare in the Lower Jurassic and most reports are of only fragmentary remains (Benton, Martill; Taylor, 1995; Owen, 1863; Woodward, 1908; Andrews, 1921; Cuny & Galton, 1993; Delsate & Ezcurra, 2014).

Ceratosaurian-grade taxa are absent until Middle Jurassic times (Maganuco et al., 2007; Pol & Rauhut, 2012), with one exception from the Pliensbachian–Toarcian of Northern Africa (Allain et al., 2007). This paucity of skeletal remains is a considerable gap in our knowledge of these animals at a time when theropods were diversifying rapidly. Just after the Triassic–Jurassic mass extinction event we begin to see a rich, worldwide distribution revealed through ichnofossils (Delsate & Ezcurra, 2014).

In Europe, we find theropod remains from the Hettangian, mostly non-diagnostic at the generic level: Scotland (Benton, Martill & Taylor, 1995), England (Owen, 1863; Woodward, 1908; Andrews, 1921), France (Cuny & Galton, 1993), and Luxembourg (Delsate & Ezcurra, 2014).

Two species of the genus Sarcosaurus have been reported from the Hettangian of England, S. woodi from Barrow upon Soar, Leicestershire, based on an isolated pelvis, vertebra, and proximal femur (BMNH 4840/1), and S. andrewsi (Huene, 1932), based on a partial tibia (NHMUK R3542) (Woodward, 1908).

There's also the neotheropod Dracoraptor hanigani, from the Hettangian of Wales, described by Martill et al. in 2016 on the basis of a 40% complete skeleton including cranial and postcranial material. In the rest of the world, the most famous Early Jurassic theropod is certainly Dilophosaurus wetherilli from the Hettangian of Arizona (Welles, 1954, 1984), which is known from several specimens.

Other relevant taxa are Sinosaurus (=“Dilophosaurus” sinensis) from the Hettangian–Sinemurian of China (Hu, 1993), Coelophysis rhodesiensis from the Hettangian–Pliensbachian of South Africa and Zimbabwe (Raath, 1990), a personal favourite Dracovenator from the Hettangian of South Africa (Yates, 2005), Cryolophosaurus from the Early Jurassic (?Sinemurian–Pliensbachian) of Antarctica (Hammer & Hickerson, 1994), Podokesaurus from the Pliensbachian to Toarcian of Massachusetts (Talbot, 1911), Segisaurus from the Pliensbachian to Toarcian of Arizona (Carrano, Hutchinson & Sampson, 2005), “Syntarsus” kayentakatae from the Hettangian of Arizona (Rowe, 1989), and Berberosaurus from the Toarcian of Morocco (Allain et al., 2007).

Ignored is the enigmatic genus Eshanosaurus from the Lower Jurassic of China, tentatively dated as Hettangian (Xu, Zhao & Clark, 2001), pending correct identification and reliably dating, as this purported therizinosaurian coelurosaur might just well be a sauropodomorph.

In this context, the discovery of the new specimen from the Sinemurian of Italy is extremely relevant as it is among the oldest Jurassic theropods, it is larger than all other pre-Aalenian theropods and it helps us to understand some of the macroevolutionary patterns that would have characterized the evolution of Theropoda during the Jurassic.

It also represents the first dinosaur skeleton from the Italian Alps, the first of Jurassic age, and the second theropod skeleton found in Italy after Scipionyx samniticus (Dal Sasso & Signore, 1998; Dal Sasso & Maganuco, 2011). The discovery of the specimen was described accidentally. For a more detailed account, see Dal Sasso, 2004 or the post here from March 9, 2020.

EVOLUTION OF FISH

The evolution of fish began about 530 million years ago with the first fish lineages belonged to the Agnatha, a superclass of jawless fish.

We still see them in our waters as cyclostomes but have lost the conodonts and ostracoderms to the annals of time. 

Like all vertebrates, fish have bilateral symmetry; when divided down the middle or central axis, each half is the same. Organisms with bilateral symmetry are generally more agile, making finding a mate, hunting or avoiding being hunted a whole lot easier. While we still find them on our menus, the ability to move quickly means they avoid being the snack of choice, an honour that falls more to the invertebrates with whom they share the sea.

When we envision fish, we generally picture large eyes, gills, a well-developed mouth. The earliest animals that we classify as fish appeared as soft-bodied chordates who lacked a true spine. While they were spineless, they did have notochords, a cartilaginous skeletal rod that gave them more dexterity than the cold-blooded invertebrates who shared those ancient seas and evolved without a backbone.

Fish would continue to evolve throughout the Paleozoic, diversifying into a wide range of forms. Several forms of Paleozoic fish developed external armour that protected them from predators. The first fish with jaws appeared in the Silurian period, after which many species, including sharks, became formidable marine predators rather than just the prey of arthropods.

Fishes in general respire using gills, are most often covered with bony scales and propel themselves using fins. There are two main types of fins, median fins and paired fins. The median fins include the caudal fin or tail fin, the dorsal fin, and the anal fin. Now there may be more than one dorsal, and one anal fin in some fishes.

The paired fins include the pectoral fins and the pelvic fins. And these paired fins are connected to, and supported by, pectoral and pelvic girdles, at the shoulder and hip; in the same way, our arms and legs are connected to and supported by, pectoral and pelvic girdles. This arrangement is something we inherited from the ancestors we share with fishes. They are homologous structures.

When we speak of early vertebrates, we're often talking about fishes. Fish is a term we use a lot in our everyday lives but taxonomically it is not all that useful. When we say, 'fish' we generally mean an ectothermic, aquatic vertebrate with gills and fins.

Rhacolepis Buccalis, an extinct genus of ray-finned fossil fish

Fortunately, many of our fishy friends have ended up in the fossil record. We may see some of the soft bits from time to time, as in the lovely Rhacolepis Buccalis, an extinct genus of ray-finned fossil fish in carbonate concretion from the Lower Cretaceous, Santana Formation, Brazil.

Not surprisingly, vertebrates with hard skeletons have a much better chance of being preserved than those with just soft parts and no teeth or bone to speak of.

In British Columbia, we have lovely two-dimensional Eohiodon rosei, a common freshwater fossil fish well-represented in Eocene deposits from the Allenby of Princeton and McAbee Fossil Beds near Cache Creek. We also have the Tiktaalik roseae, a large freshwater fish, from 375 million-year-old Devonian deposits on Ellesmere Island in Canada's Arctic. Tiktaalik is a wonderfully bizarre creature with a flat, almost reptilian head but also fins, scales and gills. We have other wonders from this time. There are also spectacular antiarch placoderms, Bothriolepsis, found in the Upper Devonian shales of Miguasha in Quebec.

There are fragments of bone-like tissues from as early as the Late Cambrian with the oldest fossils that are truly recognizable as fishes come from the Middle Ordovician from North America, South America and Australia. At the time, South America and Australia were part of a supercontinent called Gondwana. North America was part of another supercontinent called Laurentia and the two were separated by deep oceans.

Eohiodon rosei, McAbee Fossil Beds

These two supercontinents and others that were also present were partially covered by shallow equatorial seas and the continents themselves were barren and rocky. Land plants didn't evolve until later in the Silurian Period.

In these shallow equatorial seas, a large diverse and widespread group of armoured, jawless fishes evolved: the Pteraspidomorphi. The first of our three groups of ostracoderms. The Pteraspidomorphi are divided into three major groups: the Astraspida, Arandaspida and the Heterostraci.

The oldest and most primitive pteraspidomorphs were the Astraspida and the Arandaspida. You'll notice that all three of these taxon names contain 'aspid', which means shield. This is because these early fishes and many of the Pteraspidomorphi possessed large plates of dermal bone at the anterior end of their bodies. This dermal armour was very common in early vertebrates, but it was lost in their descendants.

Arandaspida is represented by two well-known genera: Sacabampaspis, from South America and Arandaspis from Australia. Arandaspis have large, simple, dorsal and ventral head shields. Their bodies were fusiform, which means they were shaped sort of like a spindle, fat in the middle and tapering at both ends. Picture a sausage that is a bit wider near the centre with a crisp outer shell.

DIPLOGRAPTUS