Tuesday 7 July 2020
SPOTTED CLEANER SHRIMP: FISH WASH
Thursday 2 July 2020
HETEROPTERAN OF THE GREEN RIVER
Sunday 28 June 2020
CRASPEDITES OF RUSSIA
Saturday 27 June 2020
AMMONITES OF THE VOLGA REGION
The Heteromorph, Jaubertites (Audouliceras) renauxianum |
These magnificent Jaubertites (Audouliceras) renauxianum heteromorph ammonites are often composites — built with exceptional artful skill from various partial specimens.
We sometimes see them cut in two symmetrical parts and glued into a matrix then doctored up a bit for sale. The practice is frowned upon both scientifically and commercially but continues as does the demand for these exceptional specimens. This beauty is in the collection of José Juárez Ruiz and is complete with some minor restorations. I love these chunky Jaubertites and particularly appreciate the beautiful oil in water colouring in the nacre.
The second photo here shows a lovely busy block of ammonites with Deshayesites volgensis (Sasonova, 1958), and Aconeceras (Sinzovia) trautscholdi (Sinzow. 1870) from Lower Cretaceous, Aptian, (120 - 112 MYA), deposits in the v. Shilovka, Ulyanovsk Region of Russia. This beauty is in the collections of Emil Black. While Emil has counselled me that there are some fundamental challenges with the interpretation of these faunal groups, I will share what is available from the current literature.
Aptian deposits near the Volga River between Ul'yanovsk and Saratov have been studied for more than a century. The area produces some of the most beautiful and sought after ammonite specimens in the world. I've never had the pleasure of collecting in this region but follow the literature and local collectors with enthusiastic interest. Looking at the specimens from here, I'm sure you can appreciate why.
Deshayesites volgensis & Aconeceras trautscholdi |
But Deshayesitidae are not the only specimens found here. The vast array of heteromorphic ammonites — the Ancyloceratidae, inhabitants of relatively deep basins, has made it possible to propose a new scheme of ammonoid zonation in the lower Aptian epipelagic deposits of the Russian plate.
Many of the identified ancyloceratids were established here for the first time. The analysis of coexisting deshayesitids and heteromorphs enables a correlation of stratigraphic schemes for the monomorphic Deshayesitidae and heteromorphic Ancyloceratidae.
The described generic taxa and species are Volgoceratoides I. Michailova et Baraboshkin, gen. nov., V. schilovkensis I. Michailova et Baraboshkin, sp. nov., Koeneniceras I. Michailova et Baraboshkin, gen. nov., K. tenuiplicatum (von Koenen, 1902), K. rareplicatum I. Michailova et Baraboshkin, sp. nov.
In some sections of the Saratov Volga area, specifically in the central part of the Russian Platform, we find both offshore and nearshore lithofacies of the epicontinental Middle Russian Sea. Here we see simultaneous changes in ammonite and belemnite successions that speak to an environmental shift. The significant influence of anoxic events on faunal turnovers in marine communities is well-established. However, many studies are focused on the impact of anoxic conditions on benthic organisms, not on the hunter-gatherers living higher up in the sea column and food chain. For this reason, coeval changes in pelagic cephalopod assemblages remain relatively poorly studied and marginally understood.
Belemnites, represented by the late members of the family Oxyteuthididae, are common in the interval directly preceding the anoxic event, but totally disappear with the onset of the black shale deposition. We see a reduction in the shell size of the Deshayesites ammonites across the mudstone – black shale boundary (maximum shell diameter of adults reduces from ∼20 cm to 7–8 cm).
Some other ammonites become numerous (Sinzovia) within the black shale interval or show the first occurrence in it (Koeneniceras and Volgoceratoides). The diminishing of Deshayesites shell size during the early Aptian OAE may have been caused by palaeoenvironmental factors such as progressive warming and regional input of brackish water.
The significant influence of anoxic events on faunal turnovers in marine communities is well-established. However, many studies are focused on the impact of anoxic conditions on benthic organisms, not on the hunter-gatherers living higher up in the sea column. This means that coeval changes in pelagic cephalopod assemblages remain relatively poorly understood.
Photo: Jaubertites (Audouliceras) renauxianum (d'Orbigny, 1842) collection of José Juárez Ruiz.
Photo: Deshayesites volgensis (Sasonova, 1958), and Aconeceras (Sinzovia) trautscholdi (Sinzow. 1870) collections of Emil Black. The diameter on the Deshayesites shown here is 70 mm.
Rogov, Mikhail & Shchepetova, Elena & Ippolitov, Alexei & Seltser, Vladimir & Mironenko, Aleksandr & Pokrovsky, Boris & Desai, Bhawanisingh. (2019). Response of cephalopod communities on abrupt environmental changes during the early Aptian OAE1a in the Middle Russian Sea. Cretaceous Research. 10.1016/j.cretres.2019.01.007.
E. Yu. Baraboshkin and I. A. Mikhailova. New Stratigraphic Scheme of the Lower Aptian in the Volga River Middle Courses. Stratigraphy arid Geological Correlation, Vol 10, No 6, 2002, pp 603-626 Translated from Stratigrafiy a Geologicheskaya Korrelyatsiya, Vol 10, No 6, 2002, pp 82-105
Friday 26 June 2020
HETTANGIAN: TETHYAN AFFINITY
Thursday 25 June 2020
EXPLORING THE GSC COLLECTIONS
Wednesday 24 June 2020
NORTH AMERICAN MIDDLE TRIASSIC AMMONOIDS
Tuesday 23 June 2020
NAPPING KOALA
Monday 22 June 2020
POKEY TACHYCLOSSIDAE
Echidnas are sometimes called spiny anteaters and belong in the family Tachyglossidae (Gill, 1872). They are monotremes, an order of egg-laying mammals.
There are four species of echidnas living today. They, along with the platypus, are the only living mammals who lay eggs and the only surviving members of the order Monotremata.
Superficially, they resemble the anteaters of South America and other spiny mammals like porcupines and adorable hedgehogs. They are usually a mix of brown, black and cream in colour. While rare, there have been several reported cases of albino echidnas, their eyes pink and their spines white. Echidnas have long, slender snouts that act as both nose and mouth for these cuties. The Giant Echidna we see in the fossil record had beaks more than double this size.
Like the platypus, they are equipped with electro sensors, but while the platypus has 40,000 electroreceptors on its bill, the long-beaked echidna has only 2,000. The short-beaked echidna, which lives in a drier environment, has no more than 400 at the tip of its snout.
Echidnas evolved between 20 and 50 million years ago, descending from a platypus-like monotreme. Their ancestors were aquatic, but echidnas have adapted to life on land. Today, they weigh in at about 7 kg today but back in the Pleistocene, they were much larger. The Giant Echnida, Megalibwilia ramsayi was about 10% larger at 10 kg and Zaglossus hacketti was a whopping 30 kg.
Fossil remains are relatively rare and sadly, incomplete, but they tell us potentially two other species of Echidna thriving in the Pleistocene. We also find Robust Echidna, Zaglossus robustus, in slightly older Miocene aged outcrops in a goldmine in Australia. The Giant Echnida's we find in the fossil record are relatives of the Long-Beaked Echidnas who live in New Guinea today.
Sunday 21 June 2020
INUKSUK: STONE SENTINELS
These rocky sentinels stand as helpful reference markers for navigation.
Translated from Inuktitut, the word inuksuk means that which acts in the capacity of a human, combining inuk or person and suk, to substitute.
Saturday 20 June 2020
KEUPPIA: UNCOVERING OCTOBRACHIA
Wednesday 17 June 2020
FOSSIL PEARLS
A simple search will show you a vast array of pearls being used for their ornamental value in cultures from all over the world. I suppose the best answer to why they are appealing is just that they are.
If you make your way to Paris, France and happen to visit the Louvre's Persian Gallery, do take a boo at one of the oldest pearl necklaces in existence — the Susa necklace. It hails from a 2,400-year-old tomb of long lost Syrian Queen. It is a showy piece with three rows of 72 pearls per strand strung upon a bronze wire.
A queen who truly knew how to accessorize.
I imagine her putting the final touches of her outfit together, donning the pearls and making an entrance to wow the elite of ancient Damascus. The workmanship is superb, intermixing pure gold to offset the lustre of the pearls. It is precious and ancient, crafted one to two hundred years before Christ. Perhaps a gift from an Egyptian Pharaoh or from one of the Sumerians, Eblaites, Akkadians, Assyrians, Hittites, Hurrians, Mitanni, Amorites or Babylonian dignitaries who sued for peace but brought war instead.
Questions, good questions, but questions without answers. So, what can we say of pearls? We do know what they are and it is not glamorous. Pearls form in shelled molluscs when a wee bit of sand or some other irritant gets trapped inside the shell, injuring the flesh. As a defensive and self-healing tactic, the mollusc wraps it in layer upon layer of mother-of-pearl — that glorious shiny nacre that forms pearls.
They come in all shapes and sizes from minute to a massive 32 kilograms or 70 pounds. While a wide variety of our mollusc friends respond to injury or irritation by coating the offending intruder with nacre, there are only a few who make the truly gem-y pearls. These are the marine pearl oysters, Pteriidae and a few freshwater mussels. Aside from Pteriidae and freshwater mussels, we sometimes find less gem-y pearls inside conchs, scallops, clams, abalone, giant clams and large marine gastropods.
Pearls are made up mostly of the carbonate mineral aragonite, a polymorphous mineral — same chemical formula but different crystal structure — to calcite and vaterite, sometimes called mu-calcium carbonate. These polymorphous carbonates are a bit like Mexican food where it is the same ingredients mixed in different ways. Visually, they are easy to tell apart — vaterite has a hexagonal crystal system, calcite is trigonal and aragonite is orthorhombic.
As pearls fossilize, the aragonite usually gets replaced by calcite, though sometimes by vaterite or another mineral. When we are very lucky, that aragonite is preserved with its nacreous lustre — that shimmery mother-of-pearl we know and love.
Molluscs have likely been making pearls since they first evolved 530 million years ago. The oldest known fossil pearls found to date, however, are 230-210 million years old.
This was the time when our world's landmass was concentrated into the C-shaped supercontinent of Pangaea and the first dinosaurs were calling it home. In the giant ancient ocean of Panthalassa, ecosystems were recovering from the high carbon dioxide levels that fueled the Permian extinction. Death begets life. With 95% of marine life wiped out, new species evolved to fill each niche.
While this is where we found the oldest pearl on record, I suspect we will one day find one much older and hopefully with its lovely great-great grandmother-of-pearl intact.
Monday 15 June 2020
IS THAT YOU, MAMMA?
When this little fellow grows up, he'll dine on fish, birds (including his penguin pals), squid and krill. Krill are small crustaceans of the order Euphausiacea that look like tiny shrimp. They look similar and are both crustaceans but shrimp hail from the suborder Natantia, order Decapoda and their hearts are located in their heads. I know, right?
Sunday 14 June 2020
PUFFIN ENJOYING A SNICK
These are pelagic seabirds that feed primarily by diving in the water. They breed in large colonies on coastal cliffs or offshore islands, nesting in crevices among rocks or in burrows in the soil. Two species, the tufted puffin and horned puffin are found in the North Pacific Ocean, while the Atlantic puffin is found in the North Atlantic Ocean. This lovely fellow, with his distinctive colouring, is an Atlantic Puffin or "Sea Parrot" from Skomer Island near Pembrokeshire in the southwest of Wales. Wales is bordered by Camarthenshire to the east and Ceredigion to the northeast with the sea bordering everything else. It is a fine place to do some birding if it's seabirds you're after.
These Atlantic Puffins are one of the most famous of all the seabirds and form the largest colony in Southern Britain. They live about 25 years making a living in our cold seas dining on herring, hake and sand eels.
The oldest alcid fossil is Hydrotherikornis from Oregon dating to the Late Eocene while fossils of Aethia and Uria go back to the Late Miocene. Molecular clocks have been used to suggest an origin in the Pacific in the Paleocene. Fossils from North Carolina were originally thought to have been of two Fratercula species but were later reassigned to one Fratercula, the tufted puffin, and a Cerorhinca species. Another extinct species, Dow's puffin, Fratercula dowi, was found on the Channel Islands of California until the Late Pleistocene or early Holocene.
The Fraterculini are thought to have originated in the Pacific primarily because of their greater diversity there; there is only one extant species in the Atlantic, compared to two in the Pacific. The Fraterculini fossil record in the Pacific extends at least as far back as the middle Miocene, with three fossil species of Cerorhinca, and material tentatively referred to that genus, in the middle Miocene to late Pliocene of southern California and northern Mexico.
Although there no records from the Miocene in the Atlantic, a re-examination of the North Carolina material indicated that the diversity of puffins in the early Pliocene was as great in the Atlantic as it is in the Pacific today. This diversity was achieved through influxes of puffins from the Pacific; the later loss of species was due to major oceanographic changes in the late Pliocene due to closure of the Panamanian Seaway and the onset of severe glacial cycles in the North Atlantic.
Friday 12 June 2020
OLENELLUS OF THE EAGER FORMATION
Olenellus are a genus of trilobites — extinct arthropods — common in but restricted to Early Cambrian rocks some 542 million to 521 million years old and thus a useful guide fossil for the Early Cambrian. Olenellus had a well-developed head, large and crescentic eyes, and a poorly developed, small tail. The fellow you see had a bit of his tail crushed as he turned to stone.
This specimen of Olenellus is from the Lower Cambrian Eager Formation of British Columbia and is typical of the group. He's from the Rifle Range outcrop near Cranbrook.
Thursday 11 June 2020
PORTUNOID CRAB
Tuesday 9 June 2020
THE ELEPHANT BIRDS OF MADAGASCAR
Aepyornis skeleton, Monnier, 1913 |
Riding the movements of the Earth's crust, Madagascar, along with India, first split from Africa and South America and then from Australia and Antarctica, and started heading north. India eventually smashed into Asia — forming the Himalayas in the process — but Madagascar broke away from India and was marooned in the Indian Ocean. Madagascar has been on its own for the past 88 million years.
Elephant birds are members of the extinct ratite family Aepyornithidae, made up of large to enormous flightless birds that once lived on the island of Madagascar. A ratite is any of a diverse group of flightless and mostly large and long-legged birds of the infraclass Palaeognathae.
Elephant birds became extinct, around 1000–1200 CE, as a result of human hunting. Elephant birds comprised the genera Mullerornis, Vorombe and Aepyornis. While they were in close geographical proximity to the ostrich, their closest living relatives are the much smaller nocturnal Kiwi — found only in New Zealand — suggesting that ratites did not diversify by vicariance during the breakup of Gondwana but instead evolved from ancestors that dispersed more recently by flying.
Elephant birds were endemic to Madagascar. Phylogenetic, genetic, and fossil evidence all suggest that the elephant bird, along with the ostrich, arrived in Madagascar and India when these landmasses were still connected to Australia and Antarctica via a land bridge.
When India and Madagascar split, the elephant bird wound up surviving on Madagascar, while the ostrich was carried north with India and was eventually introduced to Eurasia when India collided with the continent. The presence of the elephant bird on Madagascar can be chalked up to vicariance; it was living on Madagascar land already when Madagascar broke off from India. Most of the species on Madagascar today seem to be descended from individuals that dispersed from Africa long after Madagascar was established as a separate island.
Photo: Aepyornis skeleton. Quaternary of Madagascar by Monnier, 1913 by Monnier - http://digimorph.org/specimens/Aepyornis_maximus/Aepyornis.phtml digimorph.org, Public Domain, https://commons.wikimedia.org/w/index.php?curid=79655
Image: Size of Aepyornis maximus (centre, in purple) compared to a human, an ostrich (second from right, in maroon), and some non-avian theropod dinosaurs. Grid spacings are 1.0 m by Matt Martyniuk.
Cooper, A., Lalueza-Fox, C., Anderson, S., Rambaut, A., Austin, J., and Ward, R. (2001). Complete mitochondrial genome sequences of two extinct moas clarify ratite evolution. Nature 409:704-707.
Goodman, S. M., and Benstead, J. P. (2005). Updated estimates of biotic diversity and endemism for Madagascar. Oryx 39(1):73-77.
Evolution Berkeley: https://evolution.berkeley.edu/evolibrary/news/091001_madagascar
Vences, M., Wollenberg, K. C., Vieites, D. R., and Lees, D. C. (2009). Madagascar as a model region of species diversification. Trends in Ecology and Evolution 24(8):456-465.
Monday 8 June 2020
URSUS CURIOUS: TLA'YI
The animals are known for their ability to spray a liquid with a strong, unpleasant smell. Generally, the aroma from a skunk is enough of a deterrent to keep curiosity at bay. Not in this case.
Bear cubs are known for being playful and altogether too curious. Born in January, they usually stick pretty close to Mamma for the first two years of their lives but sometimes an intriguing opportunity for discovery will cross their path and entice them to slip away just for a few minutes to check it out. Yearlings are usually quite skittish, spending their time hidden up in trees. By the end of the summer, they grow into confident little bears. The karma gods were good to this wee one. Nobody was skunked in this quest for exploration, though not for lack of trying.
Sunday 7 June 2020
ELEPHANT SHREW
These small, quadrupedal, insectivorous mammals strongly resemble rodents or opossums with their scaly tails, elongated snouts, and rather longish legs.
They live in the desert and temperate grasslands of southern Africa. The Elephant shrew is considered "Living Fossils" as their distinctive morphology has not changed all that much in the past 30 million years. They ought to have been named Elephant Bunny shrew. They move through the world like wee baby elephant-bunnies, snuffling on all fours and hopping about looking for tasty snacks. They have a preference for seeds, fruit, termites and berries. They know how to live well, taking a siesta each afternoon when the sun gets high in the sky.
Thursday 4 June 2020
BASILEMYS FORELIMB
Basilemys is an extinct genus of early terrestrial or land turtles belonging to the family Nanhsiungchelyideae. They had a carapace similar in shape to aquatic turtles but limps and beak closer to terrestrial herbivores.
Today, these lovelies live in the Hell Creek floodplains munching on bits of grass and swamp plants. They are ectotherms, cold-blooded, reptiles and amniotes — they breathed air and did not lay eggs underwater but came to shore similar to modern turtles. They are known from Cretaceous deposits in North America and Asia. We've got some lovely examples from the Horseshoe Canyon Formation in Alberta and the Sustut Basin in northern British Columbia. Fossil remains of Basilemys have also been found in Saskatchewan, China, Kazakhstan, Mexico, Mongolia, the United States in California, Colorado, Montana, New Mexico, North Dakota, South Dakota, Texas, Utah, Wyoming and Uzbekistan from 144 collections and 152 occurrences. Photo credit: Joe Sertich
Wednesday 3 June 2020
BASILEMYS: FRESHWATER TURTLE
You'll recall we've found Basilemys in the Sustut Basin of northern British Columbia. These two finds allow us to make some correlations on what was happening during the Upper Cretaceous in BC and Alberta.
The species Mallon and Brinkman wrote up is intermediate in age between the Campanian forms B. variolosa and B. gaffneyi and the upper Maastrichtian forms B. sinuosa and B. praeclara. It is also intermediate in its morphology, possessing a unique suite of both plesiomorphic — divided extragulars — and derived, square epiplastral beak, pygal wider than long, traits.
The Horseshoe Canyon specimen also boasts an autapomorphic square cervical scale. Phylogenetic analysis assuming parsimony recovers B. morrinensis in a polytomy with B. variolosa and B. gaffneyi, outside the clade formed by the upper Maastrichtian forms B. sinuosa and B. praeclara. The holotype of Basilemys morrinensis provides the first evidence that this genus reached a fairly large size, sometimes over a meter in length in the Horseshoe Canyon Formation, so not as small as previously thought based on less complete shell material.
Although Basilemys is usually regarded as terrestrial based on its skull and limb morphology, this specimen has a shell with a low profile — a derived hydrodynamic feature usually indicative of an aquatic mode of life.
The Horseshoe Canyon specimen was found with well-preserved fossils of Equisetum or horsetail. The Basilemys from Sustut was also found in association with plant fossils. So, aquatic, yes. But swampy freshwater aquatic. Or perhaps wet woods and the peripheries of water bodies — lakes, rivers, ponds. We know horsetails prefer a moist location and it appears our dear Basilymys did also.
Image One: Basilemys morrinensis, CMN 57059, shell, in A, dorsal, B, ventral, C, right lateral, and D, anterior views. Photo: Donald B. Brinkman
Image Two: Depositional context of CMN 57059. Segmented stalks of Equisetum cf. E. perlaevigatum (marked by arrowheads) found associated with shell. B, CMN 57059 as it was originally uncovered in the field (CMN negative #61554). Scale bar equals 8 cm (A). Photo: Donald B. Brinkman
Mallon, J. C., and D. B. Brinkman. 2018. Basilemys morrinensis, a new species of nanhsiungchelyid turtle from the Horseshoe Canyon Formation (Upper Cretaceous) of Alberta, Canada. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1431922.
Wednesday 27 May 2020
BOTTLENOSE DOLPHINS
They have lungs, inhaling and exhaling through a blowhole at the top of their heads instead of a through their nose.
Dolphins are social mammals and very playful. You may have seen them playing in the water, chasing boats or frolicking with one another. Humpback whales are fond of them and you'll sometimes see them hanging out together. They are also quite vocal, making a lot of interesting noises in the water. They squeak, squawk and use body language — leaping from the water while snapping their jaws and slapping their tails on the surface. They love to blow bubbles, will swim right up to you for a kiss and cuddle. Each individual dolphin has a signature sound, a whistle that is uniquely theirs. Dolphins use this whistle to tell one of their friends and family members from another.
Tuesday 26 May 2020
GRAY WHALES: ESCHRICHTIUS ROBUSTUS
Young Gray Whale, Eschrichtius robustus |
Two Pacific Ocean populations are known to exist: one of about 200 individuals whose migratory route is presumed to be between the Sea of Okhotsk off Russia's south coast and southern Korea, and a larger one with a population of about 27,000 individuals in the eastern Pacific.
This second group are the ones we see off the shores of British Columbia as they travel the waters from northernmost Alaska down to Baja California. Gray whale mothers make this journey accompanied by their calves, hugging the shore in shallow kelp beds and providing rare but welcome glimpses of this beauty.
The gray whale is traditionally placed as the only living species in its genus and family, Eschrichtius and Eschrichtiidae, but an extinct species was discovered and placed in the genus in 2017 — the Akishima whale, E. akishimaensis. Some recent DNA analyses suggest that certain rorquals of the family Balaenopteridae, such as the humpback whale, Megaptera novaeangliae, and fin whale, Balaenoptera physalus, are more closely related to the gray whale than they are to some other rorquals, such as minke. Still, others place gray whales as outside the rorqual clade, a kissing cousin if you will.
John Edward Gray placed it in its own genus in 1865, naming it in honour of physician and zoologist Daniel Frederik Eschricht. The common name of the whale comes from its colouration. The subfossil remains of now-extinct gray whales from the Atlantic coasts of England and Sweden were used by Gray to make the first scientific description of a species then surviving only in Pacific waters. The living Pacific species was described by American palaeontologist, Edward Drinker Cope as Rhachianectes glaucus in 1869.
Fin Whale, Balaenoptera physalus |
In 1993, a twenty-seven million-year-old specimen was discovered in deposits in Washington state that represents a new species of early baleen whale. It is especially interesting as it is from a stage in the group’s evolutionary history when baleen whales transitioned from having teeth to filtering food with baleen bristles.
Visiting researcher Carlos Mauricio Peredo studied the fossil whale remains, publishing his research to solidify Sitsqwayk cornishorum (pronounced sits-quake) in the annals of history. The earliest baleen whales clearly had teeth, and clearly still used them. Modern baleen whales have no teeth and have instead evolved baleen plates for filter feeding. Look to the rather good close-up of this young Gray Whale here to see his baleen where once there was a toothy grin.
The baleen is the comb-like strainer that sits on the upper jaw of baleen whales and is used to filter food. We have to ponder when this evolutionary change —moving from teeth to baleen — occurred and what factors might have caused it. Traditionally, we have sought answers about the evolution of baleen whales by turning to two extinct groups: the aetiocetids and the eomysticetids.
The aetiocetids are small baleen whales that still have teeth, but they are very small, and it remains uncertain whether or not they used their teeth. In contrast, the eomysticetids are about the size of an adult Minke Whale and seem to have been much more akin to modern baleen whales; though it’s not certain if they had baleen. Baleen typically does not preserve in the fossil record being soft tissue; generally, only hard tissue, bones and teeth are fossilized.
Sunday 24 May 2020
USING BARNACLES TO TRACK ANCIENT WHALES
It is through the study of fossil barnacles that are roughly 270,000 million years old that help track ancient whale migrations. University of California Berkeley doctoral student Larry Taylor, the lead author of the study, published March 25, 2019, in the peer-reviewed journal Proceedings of the National Academy of Sciences published on some clever findings.
The barnacles not only record details about the whales’ yearly travels but also retain this information after they become fossilized. By following this barnacle trail, Taylor et al. were able to reconstruct migration routes of whales from millions of years in the past.
Today, Humpback whales come from both the Southern Hemisphere (July to October with over 2,000 whales) and the Northern Hemisphere (December to March about 450 whales along Central America) to Panama (and Costa Rica). They undertake annual migrations from polar summer feeding grounds to winter calving and nursery grounds in subtropical and tropical coastal waters.
One surprise find is that the coast of Panama has been a meeting ground for humpback whales going back at least 270,000 years.
To see how the barnacles have travelled through the migration routes of ancient whales, the team used oxygen isotope ratios in barnacle shells and measured how they changed over time with ocean conditions. Did the whale migrate to warmer breeding grounds or colder feeding grounds? Barnacles retain this information even after they fall off the whale, sink to the ocean bottom, and become fossils. As a result, the travels of fossilized barnacles can serve as a proxy for the journeys of whales in the distant past.
Barnacles can play an important role in estimating paleo-water depths. The degree of disarticulation of fossils suggests the distance they have been transported, and since many species have narrow ranges of water depths, it can be assumed that the animals lived in shallow water and broke up as they were washed down-slope. The completeness of fossils, and nature of the damage, can thus be used to constrain the tectonic history of regions.
Friday 22 May 2020
MANATEES AND DUGONGS
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 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've 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.
Wednesday 20 May 2020
ANTHOZOA: CORALS
Corals are important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.
A coral "group" is a colony of a myriad of genetically identical polyps. Each polyp is a sac-like animal typically only a few millimetres in diameter and a few centimetres in length. A set of tentacles surround a central mouth opening. Each polyp excretes an exoskeleton near the base. Over many generations, the colony thus creates a skeleton characteristic of the species which can measure up to several meters in size. Individual colonies grow by asexual reproduction of polyps. Corals also breed sexually by spawning: polyps of the same species release gametes simultaneously overnight, often around a full moon. Fertilized eggs form planulae, a mobile early form of the coral polyp which when mature settles to form a new colony.
Although some corals are able to catch plankton and small fish using stinging cells on their tentacles, most corals obtain the majority of their energy and nutrients from photosynthetic unicellular dinoflagellates of the genus Symbiodinium that live within their tissues. These are commonly known as zooxanthellae and gives the coral colour. Such corals require sunlight and grow in clear, shallow water, typically at depths less than 60 metres (200 ft). Corals are major contributors to the physical structure of the coral reefs that develop in tropical and subtropical waters, such as the Great Barrier Reef off the coast of Australia. These corals are increasingly at risk of bleaching events where polyps expel the zooxanthellae in response to stress such as high water temperature or toxins.
Other corals do not rely on zooxanthellae and can live globally in much deeper water, such as the cold-water genus Lophelia which can survive as deep as 3,300 metres (10,800 ft). Some have been found as far north as the Darwin Mounds, northwest of Cape Wrath, Scotland, and others off the coast of Washington State and the Aleutian Islands.
Tuesday 19 May 2020
CANGREJO FÓSIL: COSTACOPLUMA
Chitin is a polysaccharide — a large molecule made of many smaller monosaccharides or simple sugars, like glucose. It's handy stuff, forming crystalline nanofibrils or whiskers.
Chitin is actually the second most abundant polysaccharide after cellulose. It's interesting as we usually think of these molecules in the context of their sugary context but they build many other very useful things in nature — not the least of these are the hard outer shells or exoskeletons of our crustacean friends. There have been some wonderful studies published of late on the cuticular structure of crabs and in particular the Late Maastrichtian crab, Costacopluma mexicana, from deposits near the town of from near Paredón, Ramos Arizpe in what is now southern Coahuila (formerly Coahuila de Zaragoza), in north-eastern Mexico. We see this same species in the Upper Cretaceous Moyenne of Northeast Morocco and from the Pacific slope, Paleocene of California, USA. This beauty is in the collection of José F. Ventura.
While the crustacean cuticle has been the subject of study for over 250 years (Reaumur, 1712, in Drach, 1939), the focus of that early work has been the process of moulting. Because crabs and other crustaceans have a hard outer shell (the exoskeleton) that does not grow, they must shed their shells through a process called moulting. Just as we outgrow our shoes, crabs outgrow their shells.
In 1984, Roer and Dillaman took a whole new approach, instead looking at the exoskeleton as a mineralized tissue. The integument of decapod crustaceans consists of an outer epicuticle, an exocuticle, an endocuticle and an inner membranous layer underlain by the hypodermis. The outer three layers of the cuticle are calcified.
The mineral is in the form of calcite crystals and amorphous calcium carbonate. In the epicuticle, the mineral is in the form of spherulitic calcite islands surrounded by the lipid-protein matrix. In the exo- and endo-cuticles the calcite crystal aggregates are interspersed with chitin-protein fibres which are organized in lamellae. In some species, the organization of the mineral mirrors that of the organic fibres, but such is not the case in certain cuticular regions in the xanthid crabs.
Control of crystal organization is a complex phenomenon unrelated to the gross morphology of the matrix. Since the cuticle is periodically moulted to allow for growth, this necessitates a bidirectional movement of calcium into the cuticle during post-moult and out during premolt resorption of the cuticle.
These movements are accomplished by active transport affected by a Ca-ATPase and Na/Ca exchange mechanism. The epi- and exo-cuticular layers of the new cuticle are elaborated during pre-moult but do not calcify until the old cuticle is shed. This phenomenon also occurs in vitro in the cuticle devoid of living tissue and implies an alteration of the nucleating sites of the cuticle in the course of the moult.
We're still learning about the relationship between the mineral and the organic components of the cuticle, both regarding the determination of crystal morphology and about nucleation. While the Portunidae offers some knowledge of the mechanisms and pathways for calcium movement, we know nothing concerning the transport of carbonate. These latter areas of investigation will prove fertile ground for future work; work which will provide information not only on the physiology of Crustacea but also on the basic principles of mineralization. I'm interested to see what insights will be revealed in the years to come. Certainly, the bidirectional nature of mineral transport and the sharp temporal transitions in the nucleating ability of the cuticular matrix provide ideal systems in which to study these aspects of calcification.
Torrey Nyborg, Francisco J. Vega and Harry F. Filkorn, Boletín de la Sociedad Geológica Mexicana, Vol. 61, No. 2, Número especial XI Congreso Nacional de Paleontología, Juriquilla 2009 (2009), pp. 203-209. Coahuila paleo coordinates:25°32′26″N 100°57′2″W