Wednesday, 30 September 2020

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.

Tuesday, 29 September 2020

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.

Sunday, 27 September 2020

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.

Saturday, 26 September 2020

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.

Friday, 25 September 2020

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

Wednesday, 23 September 2020

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.

Tuesday, 22 September 2020

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.

Monday, 21 September 2020

LOPHIIFORMES: ANGLERFISH

Humpback Anglerfish, Melanocetus johnsonii
The festive lassie you see here with her toothy grin and solo birthday-candle-style light is an Anglerfish.

They are bony fish of the teleost order Lophiiformes (Garman, 1899) and one of the most interesting, intriguing yet creepy, species on this planet.

There are over 200 species of anglerfish, most living in the pitch-black depths of the Atlantic and Antarctic oceans. They always look to be celebrating a birthday of some kind, albeit solo. This party is happening deep in our oceans right now and for those that join in, I hope they like it rough. The wee candle you see on her forehead is a photophore, a tiny bit of luminous dorsal spine. Many of our sea dwellers have photophores. We see them in glowing around the eyes of some cephalopods.

These light organs can be a simple grouping of photogenic cells or more complex with light reflectors, lenses, colour filters able to adjust the intensity or angular distribution of the light they produce. Some species have adapted their photophores to avoid being eaten, in others, it's an invitation to lunch but not in the traditional sense of that invite. In the anglerfish' world, it's dead sexy, an adaptation used to attract prey and mates alike, sometimes at the same time.

Deep in the murky depths of the Atlantic and Antarctic oceans, hopeful female anglerfish light up their sexy lures. When a male latches onto this tasty bit of flesh, he fuses himself totally.

He might be one of several potential mates. Each will take a turn getting close to her to see if she's the one. For her, it's not much of a choice. She's not picky, just hungry.

Mating is a tough business down in the depths. A friend asked if anglerfish mate for life. Well, yes... yes, indeed they do. Lure. Feed. Mate. Repeat. Once connected, the attachment is permanent. Her body absorbs his over time until all that's left are his testes. While unusual, it is only one of many weird and whacky ways our fishy friends communicate, entice, hunt and creatively survive and thrive. Ah, this planet has some evolutionary adaptations that are enough to break your brain. Anglerfish are definitely in with that lot.


Sunday, 20 September 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.

Saturday, 19 September 2020

ICHTHYOSAUR BASIOCCIPITAL BONE AND TELEOST FISH

Ichthyosaur Basioccipital Bone / Liam Langley
A very exciting find of an Ichthyosaur basioccipital bone. This is the bone next to the skull that connected to the vertebrae. He found this in situ so not very water warn as you might expect. This lovely bone was found by the deeply awesome Liam Langley on the Yorkshire Coast.

Ichthyosaurs became extinct during the Upper Cretaceous, about 30 million years before the K/T extinction event. There was an ocean anoxic event at the Cenomanian–Turonian stage boundary. The deeper layers of the seas became anoxic and poisoned by hydrogen sulphide. As life died off in the lower (benthos) levels of the sea, so did the predators at the top of the food chain. The last pliosaurs and ichthyosaurs became extinct.

Ichthyosaurs had been dwindling in numbers for some time; they were no longer the force they once were in the Upper Triassic and Lower Jurassic. By the middle Jurassic, it was thought they all belonged to the single clade, the Ophthalmosauridae. By the Cretaceous, it was thought that only three genera survived. For the last 50+ years, it has been thought that only one genus, Platypterygius, was known at the time of the anoxic event in the Upper Cretaceous.

Ichthyosaur Basioccipital Bone / Liam Langley
There was still diversity in ichthyosaurs a few million years before the extinction event. They may have survived right up to the extinction event. Ichthyosaurs had declined from their peak.

By the Cretaceous, they certainly had more competitors than in the Triassic and more elusive prey. The adaptive radiation of teleost fish meant their new prey was fast swimming and highly evasive.

The difference between teleosts and other bony fish lies mainly in their jawbones; teleosts have a movable premaxilla and corresponding modifications in the jaw musculature which make it possible for them to protrude their jaws outwards from the mouth.

This is of great advantage, enabling them to grab prey and draw it into the mouth. In more derived teleosts, the enlarged premaxilla is the main tooth-bearing bone, and the maxilla, which is attached to the lower jaw, acts as a lever, pushing and pulling the premaxilla as the mouth is opened and closed. Other bones further back in the mouth serve to grind and swallow food.

Another difference is that the upper and lower lobes of the tail (caudal) fin are about equal in size. The spine ends at the caudal peduncle, distinguishing this group from other fish in which the spine extends into the upper lobe of the tail fin.

The most basal of the living teleosts are the Elopomorpha, eels and their allies, and the Osteoglossomorpha, those whacky elephantfish and their friends. There are over 800 species of elopomorphs; each with thin leaf-shaped larvae known as leptocephali specialized for a marine environment.

Among the elopomorphs, eels have elongated bodies with lost pelvic girdles and ribs and fused elements in the upper jaw. The 200 species of osteoglossomorphs are defined by a bony element in the tongue. This element has a basibranchial behind it, and both structures have large teeth that are paired with the teeth on the parasphenoid in the roof of the mouth.

The clade Otocephala includes the Clupeiformes, tasty herrings, and Ostariophysi  — carp, catfish and their friends. Clupeiformes are made up of 350 living species of herring and herring-like fish. This group is characterized by an unusual abdominal scute and a different arrangement of the hypurals. In most species, the swim bladder extends to the braincase and plays a role in hearing. Ostariophysi, which includes most freshwater fishes, has developed some unique adaptations.

One is the Weberian apparatus, an arrangement of bones, called Weberian ossicles, connecting the swim bladder to the inner ear. This enhances their hearing, as sound waves make the bladder vibrate, and the bones transport the vibrations to the inner ear. They also have a chemical alarm system; when a fish is injured, the warning substance gets in the water, alarming nearby fish. Excellent for the predatory fish, less so for their poor injured brethren.

The teleosts included fast-swimming predatory fish, which would have been competing for similar food resources to our ichthyosaur friends. Had they complained about the teleosts they would have been deeply aghast to know what was coming next — big, hungry mosasaurs. The ichthyosaurs and pliosaurs were replaced in the marine ecology by the giant mosasaurs. The mosasaurs were probably ambush-hunters, whose sit-and-wait strategy apparently proved most successful. So, teleost fish, the ocean anoxic event and the rise of mosasaurs all contributed to the end of the ichthyosaurs.

Photos 1-2: By the awesome Liam Langley
Image 3: By Sir Francis Day - Fauna of British India, Fishes (www.archive.org), Public Domain, https://commons.wikimedia.org/w/index.php?curid=1919094

Thursday, 17 September 2020

IDENTIFYING FOSSIL BONE

If you’re wondering if you have Fossil Bone, you’ll want to look for the telltale texture on the surface. It’s best to take the specimen outside & photograph it in natural light.

With fossil bone, you will be able to see the different canals and webbed structure of the bone, sure signs that the object was of biological origin.

As my good friend Mike Boyd notes, without going into the distinction between dermal bone and endochondral bone — which relates to how they form - or ossify — it's worth noting that bones such as the one illustrated here will usually have a layer of smooth (or periosteal) bone on the outer surface and spongy (or trabecular) bone inside.

The distinction can be seen in this photograph. The partial weathering away of the smooth external bone has resulted in the exposure of the spongy bone interiors. Geographic context is important, so knowing where it was found is very helpful for an ID. 

Knowing the geologic context of your find can help you to figure out if you've perhaps found a terrestrial or marine fossil. Did you find any other fossils nearby? Can you see pieces of fossil shells or remnants of fossil leaves? Things get tricky with erratics. That's when something has deposited a rock or fossil far from the place it originated. We see this with glaciers. The ice can act like a plough, lifting up and pushing a rock to a new location, then melting away to leave something out of context.

Tuesday, 15 September 2020

TUMBLER RIDGE DINOSAUR TRACKWAY

Heidi Henderson with Daniel & Charles Helm, Tumbler Ridge
In 2000, Mark Turner and Daniel Helm were tubing down the rapids of Flatbed Creek just below Tumbler Ridge.

As they walked up the shoreline excitement began to build as they quickly recognized a series of regular depressions as dinosaur footprints.

Their discovery spurred an infusion of tourism and research in the area and the birth of the Peace Region Palaeontology Society and Dinosaur Centre. The Hudson's Hope Museum has an extensive collection of terrestrial and marine fossils from the area. They feature ichthyosaurs and hadrosaur tracks along with some terrestrial goodies.

The tracks the boys found were identified the following year by Rich McCrae as those of a large quadrupedal dinosaur, Tetrapodosaurus borealis, an ichnotaxon liked to ankylosaurs.

Closer study and excavation of the area yielded a 25 cm dinosaur bone thus doubling the number of dinosaur bones known from British Columbia at the time. The dinosaur finds near Tumbler Ridge are significant. Several thousand bone fragments have been collected, recorded and now reside within the PRPRC collections, making for one of the most complete assemblages for dinosaur material from this age. Betsy Nicholls wrote up an ichthyosaur from the Upper Triassic Pardonet Formation, Shonisaurus sikanniensis. This big fellow is estimated to have grown to 21 metres (69 FT) in length, making him one of the largest marine reptile on record.

The true reveal for the paleontological significance is still to come. There are Triassic marine outcrops in northern British Columbia that extend from Wapiti Lake to the Yukon border. I'm excited for the future of palaeontology in the region as more of these fruitful outcrops are discovered, collected and studied.

This find might never have happened or been hugely delayed if not for the keen eyes of two young boys. All this from a days tubing on the river. I think of them and their excitement of a dinosaur find, then of the 1988 find of the elasmosaur by Mike Trask and his daughter on the Puntledge River — and now a newly discovered plesiosaur by Pat Trask along the Trent River. There is so much out there to explore, to discover and all of it is possible for those who are curious and explore this beautiful world.

Sunday, 13 September 2020

TRENT RIVER PALAEONTOLOGY

Trent River, Vancouver Island, BC
The rocks that make up the Trent River on Vancouver Island were laid down south of the equator as small, tropical islands. They rode across the Pacific heading north and slightly east over the past 85 million years to where we find them today.

The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. And it is massive. At 103 million km2 (40 million sq mi), it is the largest tectonic plate and continues to grow fed by volcanic eruptions that piggyback onto its trailing edge.

This relentless expansion pushes the Pacific Plate into the North American Plate. The pressure subducts it beneath our continent where it then melts back into the earth. Plate tectonics are slow but powerful forces. 

The island chains that rode the plates across the Pacific smashed into our coastline and slowly built the province of British Columbia. And because each of those islands had a different origin, they create pockets of interesting and diverse geology.

It is these islands that make up the Insular Belt — a physio-geological region on the northwestern North American coast. It consists of three major island groups — and many smaller islands — that stretches from southern British Columbia up into Alaska and the Yukon. These bits of islands on the move arrived from the Late Cretaceous through the Eocene — and continues to this day.

The rocks that form the Insular Superterrane are allochthonous, meaning they are not related to the rest of the North American continent. The rocks we walk over along the Trent River are distinct from those we find throughout the rest of Vancouver Island, Haida Gwaii, the rest of the province of British Columbia and completely foreign to those we find next door in Alberta.

To discover what we do find on the Trent takes only a wee stroll, a bit of digging and time to put all the pieces of the puzzle together. The first geological forays to Vancouver Island were to look for coal deposits, the profitable remains of ancient forests that could be burned to power industry.

Jim Monger and Charlie Ross of the Geological Survey of Canada both worked to further our knowledge of the complex geology of the Comox Basin. They were at the cutting edge of west coast geology in the 1970s. It was their work that helped tease out how and where the rocks we see along the Trent today were formed and made their way north.

We know from their work that by 85 million years ago, the Insular Superterrane had made its way to what is now British Columbia. The lands were forested much as they are now but by extinct genera and families. The fossil remains of trees similar to oak, poplar, maple and ash can be found along the Trent and Vancouver Island. We also see the lovely remains of flowering plants such as Cupanities crenularis, figs and breadfruit.

Heading up the river, you come to a delineation zone that clearly marks the contact between the dark grey marine shales and mudstones of the Haslam Formation where they meet the sandstones of the Comox Formation. Fossilized material is less abundant in the Comox sandstones but still contains some interesting specimens. Here you begin to see fossilized wood and identifiable fossil plant material.

Further upstream, there is a small tributary, Idle Creek, where you can find more of this terrestrial material in the sandy shales. As you walk up, you see identifiable fossil plants beneath your feet and jungle-like, overgrown moss-covered, snarly trees all around you.

Polyptychoceras vancouverense / BCPA 2003
Walking west from the Trent River Falls at the bottom, you pass the infamous Ammonite Alley, where you can find Mesopuzosia sp. and Kitchinites sp. of the Upper Cretaceous (Santonian), Haslam Formation. Minding the slippery green algae covering some of the river rocks, you can see the first of the Polytychoceras vancouverense zone.

Continuing west, you reach the first of two fossil turtle sites on the river — amazingly, one terrestrial and one marine. If you continue, you come to the Inland Island Highway.

The Trent River has yielded some very interesting marine specimens, and significant terrestrial finds. We've found both a wonderful terrestrial helochelydrid turtle, Naomichelys speciosa, and the caudal vertebrae of a Hadrosauroid dinosaur. Walking down from the Hadrosaur site you come to the site of the fossil ratfish find — one of the ocean's oddest fish.

Ratfish, Hydrolagus Collie, are chimaera found in the north-eastern Pacific Ocean today. The fossil specimen from the Trent would be considered large by modern standards as it is a bruiser in comparison to his modern counterparts. This robust fellow had exceptionally-large eyes and sex organs that dangled enticingly between them. You mock, but there are many ratfish who would differ. While inherently sexy by ratfish standards, this fellow was not particularly tasty to their ancient marine brethren (or humans today) — so not hugely sought after as a food source or prey.

A little further again from the ratfish site we reach the contact of the two Formations. The rocks here have travelled a long way to their current location. With them, we peel away the layers of the geologic history of both the Comox Valley and the province of British Columbia.

Photo One: Trent River, Haslam Formation, Fossil Huntress. Photo Two: Polyptychoceras vancouverense from the Upper Cretaceous (Santonian), Haslam formation, Trent River, Vancouver Island, British Columbia, Canada. 2003 BCPA Calendar.

References: Note on the occurrence of the marine turtle Desmatochelys (Reptilia: Chelonioidea) from the Upper Cretaceous of Vancouver Island Elizabeth L. Nicholls Canadian Journal of Earth Sciences (1992) 29 (2): 377–380. https://doi.org/10.1139/e92-033; References: Chimaeras - The Neglected Chondrichthyans". Elasmo-research.org. Retrieved 2017-07-01.

Directions: If you're keen to explore the area, park on the side of Highway 19 about three kilometres south of Courtenay and hike up to the Trent River. Begin to look for parking about three kilometres south of the Cumberland Interchange. There is a trail that leads from the highway down beneath the bridge which will bring you to the Trent River's north side.


Saturday, 12 September 2020

TRENT RIVER EXCAVATION

Pat Trask with a Fossil Rib Bone. Photo: Rebecca Miller
A mighty marine reptile was excavated on the Trent River near Courtenay on the east coast of Vancouver Island, British Columbia, Canada in August 2020.

The excavation is the culmination of a three-year palaeontological puzzle.

The fossil remains are those of a plesiosaur — a group of long-necked marine reptiles found in the Late Triassic to the Late Cretaceous some 215 to 80 million years ago. 

In the case of the Trent River, it is closer to 85 million years old. The rocks that make up this riverbed today were laid down south of the equator as small, tropical islands. They rode slow-moving tectonic plates across the Pacific — heading north and slightly east over the past 85 million years to where we find them today.

The plesiosaur fossil was excavated high up a cliff alongside the river. It took a month of work with planning, scaffolding, climbing gear and a team of dedicated souls to unearth what is likely a juvenile plesiosaur or elasmosaur from his 15-meter high perch. 

Bits and pieces of him have been eroding out for years — providing clues to the past and a jigsaw puzzle that has finally had the last pieces put together. The first piece of this marine reptile puzzle was found three years ago. 

The Courtenay Museum hosts regular fossil tours here, led by Pat Trask. On one of those field trips back in 2017, Pat was leading a trip with a family and one of the field trip participants picked up a marine reptile finger bone. It was laying in the river having eroded out from a nearby cliff. She showed it to Pat and he immediately recognized it as being diagnostic — it definitely belonged to a marine reptile — possibly an elasmosaur — but what species and just where on the river it had eroded from were still a mystery. She kindly donated it to the museum and that was that.

While it was an exciting find, it was a find without origin. Just where the material was coming from was unknown. It could have eroded from anywhere upstream and while many had searched the river, no other bone bits were found.   

Pat Trask Wrapping the plaster casing
Then in 2018, another piece of this paleontological puzzle was revealed. Pat was leading yet another Courtenay Museum Fossil Tour on the Trent River when one of the participants showed him a specimen that looked like a really tiny hockey puck. This second find was a wrist bone — again possibly from an elasmosaur but hard to be sure. Contemplating out loud where this material could be coming from, Pat looked down and found a vertebra in the water below his feet.

Pat put the bones in the lab at the museum. Intrigued by their origin, he began heading down to the river on his off hours to see where they might be coming from and thinking about where the erosion occurs on the Trent. 

In 2019, "I came down here and I started thinking about where the water flow would go." He could see a ledge along the river where eroded material might gather. Once he checked, he found a crack and cleaned out all the rock gathered there, finding more than a dozen bone. Pat teamed up with members of the Vancouver Island Palaeontological Society (VIPS) to scale the cliff faces above that section of the river. Jason Hawley, VIPS, did some rappelling but missed the site by a matter of feet.  

Pat had his neighbour fly a drone along the cliff face but it, too, turned up with nothing. Then at the beginning of August, Pat was back on the river in the morning with a family and said to one of the kids, "Hey, let's go look for baby elasmosaur." then they walked right over and saw a neckbone or tailbone in the river. Pat knew it hadn't been there the day before. He looked up and thought it must be coming from right up here. He came back later in the day with Deb Griffiths, his wife, set up his telescope on the river aimed at the likely portion of the cliff and bingo — he could see a bone sticking out.

He returned the next day with his brother Mike Trask. Mike found the elasmosaur on the Puntledge River back in 1988.  "We took a long pole and I said here's my target — and I hit one little piece, maybe three inches by three inches. When it fell down it had bones in it." Excited, they began planning a larger excavation that would include scaffolding, safety planning, climbing gear, permits... a lot of work in a short time. 

Plesiosaur Gastrolith
Initially, they thought there would be a small amount of fossil material, perhaps a few finger bones but over the past few weeks, they have found bones of at least half a marine reptile. 

And the beauty of this find is that most of the bones do not have to be prepared. They are literally eroding out of the matrix. No prep means no tools. Tools can impact the shape of a bone as you prepare it. They've found the pelvis bones, humerus, radius — all diagnostic to identify the genus. And this may be a new species. If it is, there is a good chance it will be named after the Trask family. 

I caught up with Pat and the team from the VIPS out on the river on August 23, 2020 — the day of the excavation. Loose rib bones, gastroliths, wrist bones, finger bones and part of the back and pelvis were recovered — and possibly the head, too. 

The bulk of the specimen was wrapped in plaster and carefully lowered to the ground by Pat and members of the VIPS, under Mike Trask's careful eye. We know that there is a femur in that jacket and possibly all the bones associated with that. Also included are the fibula and tibia and their associated bones — and I'm truly hoping there is a skull in there, too! I've popped a link below of a wee video showing the final moments as the plaster cast is lowered down from the excavation site. Take a look! It was quite an exciting moment.

It is not quite a baby, but this diminutive fellow is about four-metres long, making it a juvenile of his species. We have prepped enough of the material now to safely call it an elasmosaur. James Wood of the VIPS has done an amazing job on the preparation of this specimen using a new smaller air abrasive purchased by the Courtenay Museum.

I hope to see it published with the Trask family name. Their paleontological history is forever tied to the Comox Valley and the honour would be fitting.   

Photo One: Rebecca Miller, Little Prints Photography — she is awesome!

Photo Two: James Wood prepped the material and Pat Trask labelled and oriented the bones.

Photo Three: Pat Trask perched atop scaffolding along the Trent River. And yes, he's attached to a safety line to secure him in case of fall. 

Photo Four: A Plesiosaur gastrolith recovered amongst the stomach contents of the Trent River excavation. A gastrolith is a rock held inside a gastrointestinal tract. Gastroliths in some species are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. The grain size depends upon the size of the animal and the gastrolith's role in digestion. Other species, including marine reptiles, use gastroliths as ballast — which may have been the case here. 

See the Excavation Moment via Video Link: https://youtu.be/r82EcEF7Pfc

Friday, 11 September 2020

UPPER CRETACEOUS FAUNA OF THE PACIFIC

Mosasaur from Manitoba, Courtenay Museum Collection
The Pacific fauna from the Upper Haslam Formation was cut-off geographically from their contemporaries living in the waters of the Western Interior Seaway.

That Seaway — also called the Cretaceous Seaway, the Niobrara Sea, the North American Inland Sea, and the Western Interior Sea  — was the large inland sea that formed during the mid- to late Cretaceous and again during the very early Paleogene. 

It split the continent of North America into two landmasses, Laramidia to the west and Appalachia to the east. We see evidence of this isolation when we look at the fossil marine reptiles from the Late Cretaceous Nanaimo Group of Vancouver Island. The Late Cretaceous Western Interior Seaway of North America has an abundant and well-studied record of fossil marine reptiles. The Pacific faunas we find on Vancouver Island were isolated from their contemporaneous faunas in the Western Interior Seaway. The ancient sea stretched from the Gulf of Mexico and through the middle of the modern-day countries of the United States and Canada, meeting with the Arctic Ocean to the north. At its largest, it was 2,500 feet (760 m) deep, 600 miles (970 km) wide and over 2,000 miles (3,200 km) long.

Betsy Nicholls and Dirk Meckert published on the marine reptiles from the Nanaimo Group (Upper Cretaceous) of Vancouver Island in the Canadian Journal of Earth Sciences in 2002.

They were comparing the newly discovered fossil from the Haslam and Pender formations (upper Santonian) near Courtenay, British Columbia, which include elasmosaurid plesiosaurs, turtles, and mosasaurs. These finds are only the second fauna of Late Cretaceous marine reptiles known from the Pacific Coast, the other being the fossiliferous shales from the Chico Group, Moreno Formation of California (Maastrichtian) that overlies the Panoche Formation.

The Nanaimo Group fossils are some 15 million years older than those from the Moreno Formation. Similarly to the California fauna, there are no polycotylid plesiosaurs — though the Nanaimo Group fauna does include a new genus of mosasaur. The species that we find on Vancouver Island lived at the same time but were not mixing geographically. What we see in our faunal mix reinforces the provinciality of the Pacific faunas and their isolation from contemporaneous faunas in the Western Interior Seaway.

Elizabeth L Nicholls and Dirk Meckert; Marine reptiles from the Nanaimo Group (Upper Cretaceous) of Vancouver Island; Canadian Journal of Earth Sciences, 2002, 39(11): 1591-1603, https://doi.org/10.1139/e02-075

Thursday, 10 September 2020

TURTLE SHELLS AND DERMAL PLATES

Turtle shells are different from the body armour or armoured shells we see adorning dinosaurs like the ankylosaurs. These bad boys were blessed with huge plates of bone embedded into their skin that acted like a natural shield against predators. We find similar body body armour is found on a crocodile or armadillo.

Turtles are covered by a special bony or cartilaginous shell that originates in their ribs. It is a useful adaptation to help deter predators as their soft interior makes for a tasty snack. Though I've never eaten turtle, it was a common and sought after meat for turtle soup. I'd read of Charles Darwin craving it after trying it for the first time on his trip in 1831 aboard the HMS Beagle. It seems Charlie like to taste every exotic new species he had the opportunity to try.

Turtle armour is made of dermal bone and endochondral bones from their vertebrae and rib cage. It is fundamentally different from the armour seen on our other vertebrate friends and the design creates some unique features in turtles. Because turtle ribs fuse together with some of their vertebrae, they have to pump air in and out of the lungs with their leg muscles. Another unusual feature in turtles is their limb girdles (pectoral and pelvic) have come to lie 'within' their rib cage, a feature that allows some turtles to pull its limbs inside the shell for protection. Sea turtles didn't develop this behaviour (or ability) and do not retract into their shells like other turtles.

Armadillos have armour formed by plates of dermal bone covered in relatively small, overlapping epidermal scales called scutes, composed of bone with a covering of horn. In crocodiles, their exoskeletons form their armour, similar to ankylosaurs. A bit of genius design, really. It is made of protective dermal and epidermal components that begin as rete Malpighii: a single layer of short, cylindrical cells that lose their nuclei over time as they transform into a horny layer.

Depending on the species and age of the turtle, turtles eat all kinds of food including sea grass, seaweed, crabs, jellyfish, and shrimp,. That tasty diet shows up in the composition of their armour as they have oodles of great nutrients to work with. The lovely example you see here is from the Oxford Museum collections.

Wednesday, 9 September 2020

GREEN SEA TURTLE

The Green Sea Turtle, Chelonia mydas, also known as the Green Turtle, Black Sea Turtle or Pacific Green Turtle is a species in the family Cheloniidae.

It is the only species in the genus Chelonia. Its range extends throughout tropical and subtropical seas around the world, with two distinct populations in the Atlantic and Pacific Oceans, but it is also found in the Indian Ocean. The common name refers to the usually green fat found beneath its carapace, not to the colour of its carapace, which is olive to black.

This sea turtle's dorsoventrally flattened body is covered by a large, teardrop-shaped carapace; it has a pair of large, paddle-like flippers. It is usually lightly coloured, although in the eastern Pacific populations' parts of the carapace can be almost black. Unlike other members of its family, such as the hawksbill sea turtle, C. mydas is mostly herbivorous. The adults usually inhabit shallow lagoons, feeding mostly on various species of seagrasses. The turtles bite off the tips of the blades of seagrass, which keeps the grass healthy.

Like other sea turtles, green sea turtles migrate long distances between feeding grounds and hatching beaches. Many islands worldwide are known as Turtle Island due to green sea turtles nesting on their beaches. Females crawl out on beaches, dig nests and lay eggs during the night. Later, hatchlings emerge and scramble into the water. Those that reach maturity may live to 80 years in the wild.

Researchers at the Senckenberg Research Institute in Frankfurt, Germany discovered the remains of the oldest fossilized sea turtle known to date. Remains from a new species, Desmatochelys padillai sp, including fossilized shell and bones have been found at two outcrops near Villa de Leyva, Colombia. The find was published in the journal PaleoBios, dates the reptile at 120 million years old – 25 million years older than any previously known specimen of this beautiful and long-lived turtle.

Tuesday, 8 September 2020

A TASTE FOR STUDIES

Green Sea Turtle, Chelonia mydas
While eating study specimens is not in vogue today, it was once common practice for researchers in the 1700-1880s. Charles Darwin belonged to a club dedicated to tasting exotic meats, and in his first book wrote almost three times as much about dishes like armadillo and tortoise urine than he did on the biogeography of his Galapagos finches.

One of the most famously strange scientific meals occurred on January 13, 1951, at the 47th Explorers Club Annual Dinner (ECAD) when members purportedly dined on a frozen woolly mammoth. The prehistoric meat was supposedly found on Akutan Island in Alaska, USA, by the eminent polar explorers' Father Bernard Rosecrans Hubbard, “the Glacier Priest,” and Captain George Francis Kosco of the US Navy.

This much-publicized meal captured the public’s imagination and became an enduring legend and source of pride for the Club, popularizing an annual menu of “exotics” that continues today, making the Club as well-known for its notorious hors d’oeuvres like fried tarantulas and goat eyeballs as it is for its notable members such as Teddy Roosevelt and Neil Armstrong.

The Yale Peabody Museum holds a sample of meat preserved from the 1951 meal, interestingly labeled as a South American Giant Ground Sloth, Megatherium, not Mammoth. The specimen of meat from that famous meal was originally designated BRCM 16925 before a transfer in 2001 from the Bruce Museum to the Yale Peabody Museum of Natural History (New Haven, CT, USA) where it gained the number YPM MAM 14399.

The specimen is now permanently deposited in the Yale Peabody Museum with the designation YPM HERR 19475 and is accessible to outside researchers. The meat was never fixed in formalin and was initially stored in isopropyl alcohol before being transferred to ethanol when it arrived at the Peabody Museum. DNA extraction occurred at Yale University in a clean room with equipment reserved exclusively for aDNA analyses.

In 2016, Jessica Glass and her colleagues sequenced a fragment of the mitochondrial cytochrome-b gene and studied archival material to verify its identity, which if genuine, would extend the range of Megatherium over 600% and alter views on ground sloth evolution. Their results showed that the meat was not Mammoth or Megatherium, but a bit of Green Sea Turtle, Chelonia mydas. So much for elaborate legends. The prehistoric dinner was likely meant as a publicity stunt. Glass's study emphasizes the value of museums collecting and curating voucher specimens, particularly those used for evidence of extraordinary claims. Not so long before Glass et al. did their experiment, a friend's mother (and my kayaking partners) served up a steak from her freezer to dinner guests in Castlegar that hailed from 1978. Tough? Inedible? I have it on good report that the meat was surprisingly divine.

Reference: Glass, J. R., Davis, M., Walsh, T. J., Sargis, E. J., & Caccone, A. (2016). Was Frozen Mammoth or Giant Ground Sloth Served for Dinner at The Explorers Club?. PloS one, 11(2), e0146825. https://doi.org/10.1371/journal.pone.0146825
at 17:48 

Monday, 7 September 2020

STUPENDEMYS GEOGRAPHICUS: A COLOSSAL TURTLE

Freshwater turtles come in all shapes and sizes but one of the most interesting and massive of these is the now-extinct freshwater turtle Stupendemys geographicus.

These aquatic beasties had shells almost three metres long (up to 9.5 feet) making it about a 100 times larger and sharing mixed traits with some of it's nearest living relatives — the giant South American River Turtle, Podocnemis expansa and Yellow-Spotted Amazon River Turtle, Podocnemis unifilis, the Amazon river turtle, Peltocephalus dumerilianus, and twice that of the largest marine turtle, the leatherback, Dermochelys coriacea.

It was also larger than those huge Archelon turtles that lumbered along during the Late Cretaceous at a whopping 15 feet, just over 4.5 metres. Stupendemys geographicus lived during the Miocene in Venezuela and Columbia. South America is a treasure trove of unique fossil fauna.

Throughout its history, the region has been home to giant rodents and an amazing assortment of crocodylians. It was also home to one of the largest turtles that ever lived. But for many years, the biology and systematics of Stupendemys geographicus remained largely unknown. When we found them in the fossil record it is usually as bits and pieces of shell and bone; exciting finds but not enough for us to see the big picture.

Palaeontologist Rodolfo Sánchez with Stupendemys geographicus
Back in 1994, several new shells and the first lower jaws of Stupendemys were found in the Urumaco region near Falcón State, Venezuela. The area is known to palaeontologists as a hotbed rich in well-preserved fossils. Fossil specimens of Stupendemys geographicus were first found here back in the 1970s by Harvard University researchers.

But for almost four decades, very few complete carapaces or other telltale fossils of Stupendemys were found in the region.

This excited Edwin Cadena, Paleontologist at the Universidad del Rosario in Colombia and researchers of the University of Zurich (UZH) and fellow researchers from Colombia, Venezuela, and Brazil. They had very good reason to believe that it was just a matter of time before more complete specimens were to be found. The area is a wonderful place to do fieldwork. It's an arid, desert locality without plant or forest coverage we see at other sites. Fossils weather out but do not wash away like they do at other sites.

Their efforts paid off and the fossils are marvellous. Shown here is Venezuelan Palaeontologist Rodolfo Sánchez with a male carapace (showing the horns) of Stupendemys geographical. This is one of the 8 million-year-old specimens from Venezuela.

Rodolfo Sánchez with Stupendemys geographicus
The team collected the most recent finds from Urumaco and added them fossil specimens from La Tatacoa Desert in Colombia.

Together, they paint a much clearer picture of a large terrestrial turtle that varied its diet and had distinct differences between the males and females in their morphology. Cadena published in February of this year with his colleagues in the journal Science Advances.

The researchers grouped together from multiple sites to help create a better understanding of the biology, lifestyle and phylogenetic position of these gigantic neotropical turtles.

Their paper includes the reporting of the largest carapace ever recovered and argues for a sole giant erymnochelyin taxon, S. geographicus, with extensive geographical distribution in what was the Pebas and Acre systems — pan-Amazonia during the middle Miocene to late Miocene in northern South America).

This turtle was quite the beast with two lance-like horns and battle scars to show it could hold its own with the apex predators of the day.

They also hypothesize that S. geographicus exhibited sexual dimorphism in shell morphology, with horns in males and hornless females. From the carapace length of 2.40 metres, they estimate to total mass of these turtles to be up to 1.145 kg, almost 100 times the size of its closest living relative. The newly found fossil specimens greatly expand the size of these fellows and our understanding of their biology and place in the geologic record.

Their conclusions paint a picture of a single giant turtle species across the northern Neotropics, but with two shell morphotypes, further evidence of sexual dimorphism. These were tuff turtles to prey upon. Bite marks and punctured bones tell us that they faired well from what must have been frequent predatory interactions with large, 30 foot long (over 9 metres) Caimans — big, burly alligatorid crocodilians — that also inhabited the northern Neotropics and shared their roaming grounds. Even with their large size, they were a very tempting snack for these brutes but unrequited as it appears Stupendemys fought, won and lumbered away.

Image Two: Venezuelan Palaeontologist Rodolfo Sánchez and a male carapace of Stupendemys geographicus, from Venezuela, found in 8 million years old deposits. Photo credit: Jorge Carrillo

Image Three: Venezuelan Palaeontologist Rodolfo Sánchez and a male carapace of Stupendemys geographicus, from Venezuela, found in 8 million years old deposits. Photo credit: Edwin Cadena

Reference: E-A. Cadena, T. M. Scheyer, J. D. Carrillo-Briceño, R. Sánchez, O. A Aguilera-Socorro, A. Vanegas, M. Pardo, D. M. Hansen, M. R. Sánchez-Villagra. The anatomy, paleobiology and evolutionary relationships of the largest side-necked extinct turtle. Science Advances. 12 February 2020. DOI: 10.1126/sciadv.aay4593