Erik Jarvik - paleoichthyologist

Erik Jarvik (1907-1998)
Image Miguasha National Park

Anders Erik Vilhelm Jarvik (30 November 1907 – January 11, 1998) was a Swedish palaeozoologist who worked extensively on the sarcopterygian (or lobe-finned) fish Eusthenopteron.

In a career that spanned some 60 years, Jarvik produced some of the most detailed anatomical work on this fish, making it arguably the best known fossil vertebrate."
wikipedia

Erik Jarvik did his lifework in the Swedish Museum of Natural History in Stockholm starting in 1937 and becoming the professor and head of department in 1960. Jarvik has written extensively on sarcopterygian fossils and published two books on the subject

• Théories de l'évolution des vertébrés reconsidérées à la lumière des récentes découvertes sur les vertébrés inférieurs. Masson, Paris. 1960.
• Basic Structure and Evolution of Vertebrates, 2 Vols. Academic Press, London. 1980 

3D-modelling before computers

Erik Jarvik’s wax model showing the cavities and canals
inside the neurocranium of Eusthenopteron foordi
Image Miguasha National Park

Erik Jarvik conducted detailed anatomical studies of the cranium of Eusthenopteron foordi using a serial-section technique introduced by William Johnson Sollas and applied to fossil fishes by Erik Stensiö.

A fossil of limited external quality was sectioned by grinding off a thin section, photographing the grind-off end and repeat the process until the whole fossil was worked through. The internal structures would then show up on long series of photographs.

Working in the day before computer simulations, models was made by projecting reversal film on a board, and cut thin wax plates to match. The sticky wax plates could then be assembled to a 3 dimensional scaled up model of the skull, complete with internal structures such as nerve channels and other internal hollows rarely seen in fossils.

Further section to the cranium could easily be made by cutting the wax model at the desired angle. Due to the sticky nature of the wax used, a sectioned skull was put back together by simply pressing the two sections back together. This technique was also applied to the cranium of the porolepiform Glyptolepis groenlandica.
wikipedia

Important but passée
On the basis of his detailed studies of the heads of Eusthenopteron Jarvik proposed a theory on the evolution of tetrapods in which amphibious animals were classed into two groups, one related to salamanders and the other to frogs. According to Jarvik amphibian life evolved twice in prehistoric planet Earth.

Jarvik also studied the anatomy and relationships of lungfish which he held to be relatively primitive gnathostomes, possibly related to holocephalans, and of acanthodians, which he considered to be elasmobranchs rather than osteichthyans.

He made contributions to a number of classical problems in comparative anatomy, including

• the origin of the vertebrates 
• the origin of the pectoral and pelvic girdles 
• the origin of paired fins
• the homologies of the frontal and parietal bones in fishes and tetrapods 

Finally, Jarvik investigated the anatomy of Ichthyostega, resulting in a monograph with an extensive photographic documentation of the material collected in 1929-1955.

Jarvik, E. (1996). The Devonian tetrapod Ichthyostega. Fossils and Strata, 40, 1-213.
Some of Jarvik’s views did not accord with general opinion in vertebrate palaeontology   However, his anatomical studies of Eusthenopteron foordi laid the foundations for modern studies of the transition from fishes to tetrapods. 

Jarvik was a member of the Royal Swedish Academy of Sciences and French Academy of Sciences and Knight of the Order of Vasa. The lungfish Jarvikia and the osteolepiform Jarvikina are named after him.
wikipedia

Third day Devonian

Tree-ferns in Nunniong, Australia
Image: Fir0002/Flagstaffotos
wikimedia

The earliest known trees appear in Devonian. The Late Devonian Wyazzit looked much like the unrelated tree-ferns in the photo and could grow 8 meters high.


The greening of land
"The Devonian period marks the beginning of extensive land colonization by plants. With large herbivorous land-animals not yet present, large forests could grow and shape the landscape.

Early Devonian plants did not have roots or leaves like the plants most common today and many had no vascular tissue at all. They probably spread largely by vegetative growth, and did not grow much more than a few centimeters tall. By far the largest land organism was Prototaxites, the fruiting body of an enormous fungus that stood more than 8 meters tall, towering over the low, carpet-like vegetation.

By Middle Devonian, shrub-like forests of primitive plants existed: lycophytes, horsetails, ferns, and progymnosperms had evolved. Most of these plants had true roots and leaves, and many were quite tall.

In the Late Devonian, the tree-like ancestral fern Archaeopteris and the giant cladoxylopsid trees grew with true wood. (See also: lignin.) These are the oldest known trees of the world's first forests. The earliest known trees, from the genus Wattieza, appeared in the Late Devonian around 380 Ma.

By the end of the Devonian, the first seed-forming plants had appeared. This rapid appearance of so many plant groups and growth forms has been called the "Devonian Explosion".

The 'greening' of the continents acted as a carbon dioxide sink, and atmospheric levels of this greenhouse gas may have dropped. This may have cooled the climate and led to a massive extinction event, Late Devonian extinction."
wikipedia


Genesis
And God said, “Let the waters under the heaven be gathered together unto one place, and let the dry land appear”; and it was so. And God called the dry land Earth; and the gathering together of the waters called He Seas; and God saw that it was good.

And God said, “Let the earth bring forth grass, the herb yielding seed, and the fruit tree yielding fruit after his kind, whose seed is in itself, upon the earth”; and it was so. And the earth brought forth grass, and herb yielding seed after his kind, and the tree yielding fruit, whose seed was in itself, after his kind; and God saw that it was good.

And the evening and the morning were the third day.
Genesis 1:9-13 KJ21


Comment
1. Both texts specify the importance of plants that now begin to appear

2. Both texts list attributes of the various plant species

3. "Late Devonian Extinction"  -  "And the evening came" as boundary marks. Five major extinctions are known in the history of life on planet Earth. Genesis has six days of creation before the great Sabbath.

Dark evolution of life

Devonian nature
Rekonstruction Mary Parrish

The following example of modern evolutionary biology explaining excretion in tetrapods has some sentences that I find very suspicious.

The common ancestor of all present gnathostomes lived in freshwater, and later migrated back to the sea. To deal with the much higher salinity in sea water, they evolved the ability to turn the nitrogen waste product ammonia into harmless urea, storing it in the body to give the blood the same osmolarity as the sea water without poisoning the organism. This is the system currently found in cartilaginous fishes and the first bony fishes (acanthodians).

Ray-finned fishes (Actinopterygii) later returned to freshwater and lost this ability, while the fleshy-finned fishes (Sarcopterygii) retained it. Since the blood of ray-finned fishes contains more salt than freshwater, they could simply get rid of ammonia through their gills. When they finally returned to the sea again, they did not recover their old trick of turning ammonia to urea, and they had to evolve salt excreting glands instead.

Lungfishes do the same when they are living in water, making ammonia and no urea, but when the water dries up and they are forced to burrow down in the mud, they switch to urea production. Like cartilaginous fishes, the coelacanth can store urea in its blood, as can the only known amphibians that can live for long periods of time in salt water (the toad Bufo marinus and the frog Rana cancrivora). These are traits they have inherited from their ancestors.

If early tetrapods lived in freshwater, and if they lost the ability to produce urea and used ammonia only, they would have to evolve it from scratch again later. Not a single species of all the ray-finned fishes living today has been able to do that, so it is not likely the tetrapods would have done so either.

Terrestrial animals that can only produce ammonia would have to drink constantly, making a life on land impossible (a few exceptions exist, as some terrestrial woodlice can excrete their nitrogenous waste as ammonia gas). This probably also was a problem at the start when the tetrapods started to spend time out of water, but eventually the urea system would dominate completely.

Because of this it is not likely they emerged in freshwater (unless they first migrated into freshwater habitats and then migrated onto land so shortly after that they still retained the ability to make urea), although some species never left, or returned to, the water could of course have adapted to freshwater lakes and rivers. wikipedia

It seems to me that for the anonymous writer(s) anything goes

• in order to manage the much higher salinity of sea water some animals evolved the ability to change nitrate based ammon into harmless urea. (How on earth did they evolve themselves?)
• bone-finned fish had to evolve salt evicting gills when they returned from fresh water to the sea (How on sea did they evolve themselves?) 
• if first tetrapods lived in fresh waters and forgot the ability to produce urea (how?) they would have to be able to evolve this skill again from the beginning (How on lake did they evolve themselves?)
• They were not able to do so. (Who prevented them from evolving a forgotten skill?) 

Of course, such active use of verb evolve is parlance. But it is extremely common and also extremely misleading as science has no known mechanism how a species can control its own evolution. The only generally accepted mechanism is survival of the fittest, the ability to adapt, which is population statistics and environmental analysis but not very well known on biological level.

In my opinion there is a Dark evolutionary force of life driving, guiding, blocking and enhancing life forms in different environments.

Dark because this force is not well understood by science. Biologist and paleontologists can only describe what happened and proposed theories why. How exactly, that is another story.

So statements like this are very misleading
They had to evolve salt excreting glands instead.  How on earth would those tetrapods do that? By using their brains?

Astrophysicists are humble enough to say that they do presently not know how galaxies accelerate against the well-known rules of gravity that govern the Universe. They work on it and in the meanwhile call it Dark energy. Someday soon science may know more about it.

Instead of nonsensical "the species evolved this and that" biologists should be equally humble and confess that presently we do not know what is life and what is the force that drives it in evolution against the well-known physical laws of entropy that govern the Universe. They work on it and could as well in the meanwhile call it Dark evolution of life. Someday soon science may know much more about it.


Ye Old ID again?
By confessing to ignorance about what makes living things evolve to provide raw materials for natural selection are we trying to introduce Intelligent Design again into the discussion?

Not really.

The difference between respecting the great unknown of evolution and suggesting intelligent design is that ID people do suggest best engineering patterns and other human ideas of how an omnipotent philosopher's god must be taken into account in science as the watchmaker.

Dark evolution of life approach takes life as it has been and is much more seriously than ID theories. History of life as witnessed in fossil record, in life cycles and development of embryos and otherwise in past and existing life forms is there. This is the given life that we can study using the tools and methods and abilities that we have been given. (And I do not mean that in positivist sense!)

From a religious point of view I emphasize that philosopher's gods are like other man made idols and productions of human mind.

The God of Israel is the only real God there is. He has made the extraordinary and outrageous claim that He has made this all. Outrageous because He claims to have created you and me and is going to hold us responsible for how we live our lives here upon planet Earth.

Amphibious

Aquada-car speeding in water
MSN autos

amphibious  (amfi - both bios - life)

Nobody makes inventions among the created beings as man. But even for us the building of a usable amphibious vehicle is a challenge and they do not come cheap. Water has its resistance where rotors and sails and steams help and rudder is important. On the roads we need wheels and driving wheels and engines to have a working self-moving auto mobile.

Not for nothing evolutionary biologist call the beginning of life on dry land during the Devonian period one of the most momentous events in the history of life on Earth.


Water OR land
Fish and fish-like animals find it fun and efficient to move in water. Two legged man needs there special skills to move around or to dive. Without technical help man is no match to dolphins in swimming competition.

On land horses gallop and enjoy the wind in its hair flowing. But in deep water those powerful four legs are of little use and drowning is a real threat as water fills its lungs made for breathing air.

On land fish is as good as dead with its gills made for breathing in water. That powerful tail does not move it far only makes some desperate jumps. Unless it gets quickly back to water its life is over.

Water AND land 
God thus had quite a challenge in bringing animal life from water to land. Water was teeming with life fully adapted to the conditions and able to get the daily portion of oxygen directly from water.

Scientist suggest that the solution moving living beings to dry land was in an intermediate amphibious animal that

• was able to breath in water with gills and was also able to breath air with lungs on land
• was able to swim in water, catch food and escape predators, but was also able to move on dry land using its front fins 

Land only

The theory goes that when such amphibious animals called tetrapods had spend enough time in water AND land they adapted to life on land ONLY.  

Through such a middle animal, amphibious beings, life could have moved from water to land.

Evidence for such animals have been searched in the Devonian period, the Age of Fish, when also plants start to flourish on dry land and even first trees appear.  

Since many land ONLY animals are known from Carboniferous period they must have arrived from somewhere in Devonian.  

Noah animal?
Tetrapod is in a way a kind of Noah since scientists think that ALL LAND ANIMALS are its children, including us humans.

For this reason the Devonian period is of such central importance to the study of the history of life on Earth.

There is time when life was found only in water.

There is time when life is found both in water and on land.

In the beginning of life on dry land there was tetrapod.

Fishapod

Devonian fishapod
wikimedia

The schematic drawing has devonian sarcopterygia lobe-fins and tetrapods four legged animals. Fishapod half fish and half four legged animals.

The list below includes six devonian lobe-fins and tetrapods as well as one from Carboniferous and one from Permian periods.

First animal in the list is the still living Coelacanth and last animal pictured is a seal as an example of a developed mammal who can swim and also move on land using its fins and breathing with lungs.


Lobe-fins

Coelacanth - hollow skeleton "Living fossil"

Latimeria chalumnae malli
Oxford Museum of Natural History
wikimedia

1. Eusthenopteron - steady fins "Prince of Miguasha"

Eusthenopteron model
Late Devonian Miguasha Quebeck Canada
wikimedia

2. Panderichtys - Pander's fish Named after Christian Heinrich Pander

Panderichtys rekonstruction
Devonian period Latvia
wikimedia 

3. Tiktaalik - Canadian inuit word for burbot "Missing link"

Tiktaalik roseae rekonstruction
Devonian period Nunavut territory, Canada
wikimedia

Tetrapod

4. Ichtyostega - fish leg First discovered tetrapod. Lived in water

Ichyostega rekonstruction
Greenland, Danemark
wikimedia

5. Acanthostega - spiky roof  (strange name...) Relative of Ichyostega Lived in water

Acanthostega modek Stuttgart Museum of Natural History
Greenland, Danemark
wikimedia

6. Tulerpeton - "Crawling from Tula" Relative of Ichyostega. Also on land

Tulerpeton rekonstruction
Andreyevka, Tula, Russia
wikimedia

7. Hynerpeton - "Crawling from Hyner" 8 fingers

Hynerpeton rekonstruction
Hyner, Pennsylvania USA
wikimedia

8. Crassigyrinus - "big tadpole" Carboniferous

Crassigyrinus scoticus rekonstruction
Skotlanti
wikimedia

9. Diadectes - "cross bite" First large 1.5-3 m long land animal. Permian

Diadectes rekonstruction
wikimedia

Diadectos another reconstruction
wikimedia

Pinniped - fin footed!

Harbour seal foca vitulina
wikimedia

Among the mammals we know from our own world there are animals that move in water with fin like limbs. The details are different but the idea is the same as in Late Devonian lobe-fins and tetrapods. Those fins are clumsy on land ... but work somehow!

Tricycles and other means for moving around

Holocene period  6V tricycle
Feber Trimoto Neon

First on all fours then on to rear legs. But running takes practice and child needs usually about a year to find the balance. Some happy early walker gets a tricycle for higher speed, one in front and two back-wheels gives control of direction and balance. Later on human children learn to control vehicles with only two wheels that utilize the gyroscope principle. Many upgrade the vehicles to those with four wheels and some invest on four-wheelers.

God did not create animals that move on wheels but men use wheels quite efficiently, thank you. (Cell motors do have efficient rotating tails, it is true.) In the spiritual world Ezekiel sees in his vision creatures equipped with rotating wheels. For us modern people it is very difficult to visualize his technical description - are the wheels part of the beings or independent of them?

As I looked at the living creatures, I saw a wheel on the ground beside each creature with its four faces. This was the appearance and structure of the wheels: They sparkled like topaz, and all four looked alike. Each appeared to be made like a wheel intersecting a wheel. As they moved, they would go in any one of the four directions the creatures faced; the wheels did not change direction as the creatures went. Their rims were high and awesome, and all four rims were full of eyes all around.

When the living creatures moved, the wheels beside them moved; and when the living creatures rose from the ground, the wheels also rose. Wherever the spirit would go, they would go, and the wheels would rise along with them, because the spirit of the living creatures was in the wheels. When the creatures moved, they also moved; when the creatures stood still, they also stood still; and when the creatures rose from the ground, the wheels rose along with them, because the spirit of the living creatures was in the wheels.

Ezekiel 1:15-21 NIV

Without legs

Black mamba
Image ©2012 National Geographic

In the Garden of Eden story snake moved on somesort of legs until it was cursed by God and forced to move in dust on itse belly. Pretty fast it goes without legs and they say that black mamba can even reach a galloping horse and rider.

So the Lord God said to the serpent, “Because you have done this,

“Cursed are you above all livestock
    and all wild animals!
You will crawl on your belly
    and you will eat dust
    all the days of your life.

Genesis 3:14 NIV

Evolution biologist do suggest that snakes have somehow lost the legs they once had but that is another story.

Two legs

youTube video shows a truly fast running lady   

If God has created two legs under the middle of the body as to dinosaurs and birds the balance may still be kept and there can be plenty of speed. Dinos lower their heads and raise their tails and off we go trying to outrun them! The rather cumbersome looking ostrich with its large feathers and tall neck is able to run surprisingly fast - 70 km in hour.


Four legs

Four legged pulling two wheelers
Vermo
Kuva ©2012 Suomen Kuvalehti

Many land animals have got form Creator four legs. They are particularly suitable for moving on dry land and when equipped with nails can be very helpful also in many kinds of tasks in addition to running and climbing. These animals do not have hands free from the task of moving around.


All movers under the power of two-legged ones 
Waters are teeming with living swimmers with all kinds of fins and tails and systems for moving from crabs to medusa and whales. All sorts of legless snakes, worms crawl on land, birds fly in the air on their feathered wings - or run on their two feats fast as a car. Frogs have legs specialized for jumping and some even climb to trees and kangaroos know how to jump too.

The Creation story in Genesis does not count legs but talks about moving in water, on land and in air and about the absolute power given to humans to do what they want with all of them

Then God said, “Let us make mankind in our image, in our likeness, so that they may rule over the fish in the sea and the birds in the sky, over the livestock and all the wild animals, and over all the creatures that move along the ground.”
Genesis 1:26 NIV

And so it happened.

Dipnorhynchus had lungs

Protopterus dilloi disected 
wikimedia

Lung fish (dipnoi) i.e. salamander fish are well known because while they first appear in Devonian period they still live and multiply in the warm seas of Earth today. Biologists can study them in nature and put them under the microscope at will. The hallmark of these fishes are the lungs that they use to breath air reaching them through their gills.

We will discuss Devonian lung fish later more.

For now, read more about these wonders of Nature in wikipedia.

Dipnorhynchus model from Japan
tfpaleo blog

Sarcopterygi - flesh fin fish

Two lobe-fins from Devonian period and one from Triassic (up left)
Image Devonian times

Devonian bone fish include species with lobe-fins instead of bony fins. There are many different species classed together as Sarcopterygii (Gr. sarks and pteryx, flesh fin). In early models the fin is joined to the body with a single bone and the fins resemble more limbs than fins. These fish usually have two dorsal fins instead of the one other bone fish have.
(wikipedia)

Coelacanth Artist's view
Image Biology of Sharks and Rays

It was generally considered that the Devonian lobe-fins perished with the dinosaurs in the evening that ended the Mesozoic period. One of them was Coelacanth (Gr. koilos akantha, hollow backbone) found for the first time and named in 1839 by the famed Swiss paleontologist Louis Agassiz (1807-1873).

So it was quite a surprise when a live Coelacanth was caught by fishers in 1938 from Chalumne river in South Africa. Today it is known that such live fossils of Devonian fish are living near the coasts of Indian Ocean and Indonesia. Two subspecies have been identified, Latimeria chalumnae and Latimeria menadoensis.  

(see more in wikipedia )

Coelacanth caught in 1974 Comoros islands, Mozambique
Vienna Nature Museum, Austria
wikimedia

Bony Osteichthyes

Devonikauden elämää meressä
kuva University of Michigan Museum of Paleontology

And God said, “Let the water teem with living creatures, and let birds fly above the earth across the vault of the sky.” So God created the great creatures of the sea and every living thing with which the water teems and that moves about in it, according to their kinds, and every winged bird according to its kind. And God saw that it was good. God blessed them and said, “Be fruitful and increase in number and fill the water in the seas, and let the birds increase on the earth.” And there was evening, and there was morning—the fifth day.
Genesis 1:20-23

And so it happened..

Osteichthyes (osteo ikhthys bony fish) have bony skeleton supported by calcium salts. Sharks and their relatives have cartilage body without hard bony skeleton.

Bony fish are among the most fruitful among God's creations. Humans have recorded over 20.000 species, which is statistically highest among all vertebrates. Four-fifth of planet Earth is covered by water so there is room for many kinds of fish.

Osteichthyes are divided into 34 major subspecies

Bony fish have

• jaw
• bony skeleton
• skin covered by scale (some exceptions)
• fin pairs 
• tooth (some exceptions)
• gills protected by bony shields (operculum) Shark gills lack this.

Fernback education Osteichtyes 

Gills - oxygen in water 

Microscope image of fresh water fish gill surface
wikimedia

Gills are a module used by many creatures living in water and corresponds to lungs of land animals.Gills take oxygen directly from water and use them to "breath out" carbon dioxide.

Water has 50 times less oxygen (5gr in cubic meter of fresh water) then atmosphere  (250gr in cubic meter of air). To get as much oxygen as possible into blood the gills must be very thin and folded  (see more in wikipedia)

Swim bladder

The swim-bladder is another mircacle of creation
wikimedia

Only bony fish have the amazing swim-bladder module. Darwin was thinking that these are related to the evolution of lungs in land animals. The module is not used for breathing but rather gives the fish ability to raise or sink deeper or hover at level in water without swimming. Sharks and other cartilage fish need to swim in order to stay put or dive deeper or raise higher in water. Bony fish fill the bladder through mouth and let air out as the bubbles familiar to us in aquariums. 

One of the wonders of the elastic swim-bladder is the fact that it is airtight. Gases do not penetrate the surface because it is covered from inside by guanine crystals.

So what you say! Having lost all your ability to wonder like a child, haven't you?

Guanine crystals inside the fish bladder?

Guanine molecyle
wikimedia

Guanine C₅H₅N₅O molecule has five carbons, five hydrogens, five nitrates and one oxygen atom. When bound they form one of the alphabets of DNA (ACTG).

Adam's children learned to know guanine from bird droppings in 1844 (sp. guano) and it is a valuable fertilizer on fields maintained by humans. (wikipedia)

Fish bladder does not smell all that well. However, Parisian master of fragrances, François Jaquin, invented in 1656 a method to use guano crystals to improve rose water. Today G-crystal is used for example in shampoos. This link gives an animated picture of the 3D sturcture of these crystals and more information about this wondrous organic material.


Miracles of Devonian life
After I have pointed out in very superficial way just some features of fish you are welcome to join me in wondering the bony fish, Osteichthyes, that begins to appear and then practically fills Devonian seas and fresh water sources.

If you are under the impression that modern evolutionary science has satisfactorily explained the origins of bones, scales, fins, gills and guanine-crystal plated swim bladders you still do not know as you should know!

"Now about food sacrificed to idols: We know that “We all possess knowledge.” But knowledge puffs up while love builds up. Those who think they know something do not yet know as they ought to know. But whoever loves God is known by God."
St Paul 1 Corinthians 8.1-3 NIV

God's creation - fins

Hektorin lampfish wikimedia

Terminology
1. Pectoral fins - pair
2. Pelvic fins
3. Dorsal fin
4. Adipose fin
5. Anal fin
6. Caudal fin


For many people it is so obvious that fish has fins and bones. Of course a fish has fins.

Me no more... after studying just a little Devonian fish I have realized that fins are among the great works of creation with enormous significance to all life upon earth.

Many fish use them to swim, some fly over a ship, some climb to trees in swampy areas. Evolutionary biology suggests that all land animals legs and hands have their origins in fishy fins.

The fin is usually made of bones covered by skin, sometimes cartilage. Amazing design allows some fish to fold their dorsal fin or use it for defence or even to crawl into the safety of a hole in coral reef.

We also use the word fin for the limbs of sharks, whales, dolphins and seals because they look the same. Well, a diver uses flippers like ducks rather than fins like barracudas.

wikipedia provides many interesting facts about fins.

Pike is a fish and has fins
Ville Immonen from Lappeenranta Sport fishers is a Finn
Photo Luonnossa.net

Sharks

Tiger shark - God's amazing creature
Image Animal Discovery

Shark must be one of the most amazing and successful creatures God has made in the blue seas of Earth. Fossils are found starting from Middle Devonian and it has survived till modern days. The first real threat to its existence are the humans who massacre these marvellous animals for food and for fun at the rate of over 100 million a year.

Scientific sons of Adam have named them Chondricthyes from Greek khondor ikhthys, cartilage fish.   

Evolutionary biologists suggest that sharks are relatives of placodermi covered by cartilage instead of protective bony armour plates. Dropping the heavy knights iron turned out to be a great decision - heavily protected placodermi perished at the end of Devonian sharks are doing very well, thank you, except for the threat from the even more successful land dwelling bi-pedals ruling over all life on this planet.

Shark tooth
Because sharks body is cartilage and not bony with calcium Devonian fossils are quite rare if existent at all. However, their presence from Middle Devonian on can be deducted from the numerous tooth fossils that have survived.

Image: kidszone.ws

Shark tooth from Eocene and Pliocene sediments
Bolton Museum, Lancashire, UK

Fossil forum has a rare photo of a Devonian shark tooth discovered in 2009 Holy Cross Mountain, Kowala, Poland.

Placodermi had first jaws

Placodermi had strong armored front. Artist view
Image armadaproject.org 2004

This fish looked already like a real fish with jaw, gills and cartilage skeleton. It is considered the first vertebrate on Earth that had jaws. It first appears in Late Silurian and becomes very common during the Devonian period. Adam has called these placodermi (Gr. plax derma plate skin). These creatures were very successful and constitute the most common fish species in the Age of Fish. Placodermi could be a real threat to other fish and animals living in the waters as they were aggressive hunters and would even fight each other when aggravated. Although most of them were only some 15 cm long there were species that grew up to 4 or even 10 meters long sea monsters.

Placodermi did not survive the night that fell at the end of the Devonian period in massive extinction of life forms.

Mike Viney (2008) tells that among all creatures on Earth these animals were the first to have jaws and a pair of fins. The tail resembles that of a shark so they must have been effective swimmers. The dorsal fin assisted in moving in waters. The head area was protected with massive armour while the rear part was covered only by scales or skin as with ostracodermi. They usually had sharp edges on the armour plates around the mouth and only some had teeth.

Placodermi inhabited both salty seas and fresh water regions. Adam has classified seven sub-species listed below with links to PALAIOS.org pages. There you can find drawings and more information about these important devonian fish.

__________________________________________________

Acanthothoraci - spike chest. Eyes supported by bones, adults had the plates grown together.

Arthrodira - joint neck. The most common placoderm consisting about half of all the fossils discovered so far. Some arthodira could grow to even 10 meters (Dunkleosteus). The ball-joint in the neck allowed it to raise the front of the head armour and to drop the jaw into an enormous gaping mouth. Some had also teeth in addition to the sharp edges of the bone plates around the mouth.

Dunkleosteus. Late Devonian.
Reconstruction Karen Carr The Royal Tyrrell Museum of Paleontology

Antiarchi - anti anus. The second most common placoderm species. It was a small strongly protected fish as the armour covered most of its body. The eyes were looking upwards so it probably lived near the muds in search of food. Antiarchi had front fins with joints and were able to use them to crawl on the bottom.

Antiarchi had fins equipped with joints
Picture uua.ca

Petalichthyida was a small fish living at the bottom of lates. Its armour was covered with knobs.

Phyllolepida - leaf scale. These flat fish were protected by bony plates and apparently lived only in fresh waters. The species may have been blind suggesting life in darkness (caves?).

Ptyctodontida - beak tooth. This was a small placoderm with big eyes and heavy mouth plates used to break shells. The fossils resemble the rat fish (in picture) living in northern Pacific Ocean.

Spotted rat fish. Hydrolagus colliei
Image Fish index

Rhenanida - Rein fish. This was very flat resembling rays. Instead of bony plates the front of its body was covered with scales.

H.C. Pander and strange Conodonts

Heinz Christian Pander (1794-1865)
wikimedia

Latvian German biologist Heinz Christian Pander (1794-1865) studied among other things chick embryos. Because of his advanced researches Pander is called the Father of Embryo studies and he was made member of St. Peterburg's Academy of Sciences in 1825.

H.C. Pander worked in his home in Carnikava by the Gauja-river near Riga. At that time English naturalists were taking major steps advancing geology. Pander knew about the subject and in addition to embryos was interested also in "the beginning of life".  In 1820 he had taken part in at that time a rather dangerous research expedition to Bukhara, Persia.

Three types of conodont
Mauch Chunk formation, Carboniferous
wikimedia

Heinz Christian Pander is the first one to report strange spiny objects in sedimentary rock. As a son of Adam he gave these curious items scientific name conodont (kr. konos odont, conical tooth).


Conodont
Conodonts remained a scientific mystery for 150 years. They were known from many rock sediments around the world but what are they, remains of some kind of living things, just mineral formations, pieces of coral? There was no certainty about any of these theories in the lack of evidence beyond the strange conodont micro-fossils.

Only in 1980 did Adam find the answer. By the grace of God he found a Nature Reserve in South Africa where conodont were found connected to the head of an animal. While apparently fairly common in prehistoric oceans the soft tissues of the animal have disappeared and only the hard tooth-like elements survived. Today scientists know only 11 well-preserved samples of conodont.

Working on Soom shale
Kuva courtesy of Prof. Richard Aldridge & Dr Sarah Gabbott, University of Leicester, UK

One of the locations where conodont remains have survived is in South Africa. The 10-15 m thick Soom shale, Cederberg formation, is in Table Mountain near Cape Town and is dated to Ordovician period well before Devonian (the entire formation is amazing 120 meters thick).

The animals found are rather short, often only one cm or so, but a huge 40 cm long specimen has been found in Soom shale. Adam called it Promissum pulcrum. See for example Johannes N. Theron 1992 report of an Upper Ordocivian konservat-lagerstätte in the Journal of Micropalaeontology.

Photo Winneshiek lagerstätte

Huaibao P. Liu, Robert M. McKay ja Brian J. Witzke describe a discovery of the Winneshiek lagerstätte in Decorah, Iowa. The pages have illustrations of the work and discoveries, one of which I copied here. The beast looks quite scary - until you double check the scale.

Today conodont is better known. It is jawless but inside the head is an arrangement of tooth-like elements consistingn of 15 or 19 tooth. It had two eyes in front of the head, fin to help in swimming and a skeleton like notochord (chick embryos studied by Pander also have a notochord).

Without a jaw cocodont did not bite its food. Instead, plankton entered its open mouth while it was swimming and the tooth-arrangement crushed it for digestions. Conodont did not have muscles to gain speed for attack and was probably not an active hunter.

Conodont wikimedia

As we ponder the background of Devonian fish we need to keep in mind conodont that appears already in Late Cambrian.

It is not a fish, not a bird, not a frog ... it is a conodont named by H.C. Pander.

It is no more. Conodont fossils are not found after the evening that ended Triassic. But it was a very successful creature existing on planet Earth for over 300 million human years.

Eel looks a bit like conodont but is a real fish
Image Jon Staple

Bony Ostracoderm

Photo National Geographic

Towards the end of Devonian period the seas and fresh water areas were swarming with all kind of fish and other living things. The Gogo catch includes over fifty different species of fish.

Careful study of Devonian rock sediments suggests that although there were so many fish at Late Devonian there were only quite few species in Early Devonian with some background in Silurian period. During Devonian these animals began to do what God told them.

And God said, “Let the water teem with living creatures, and let birds fly above the earth across the vault of the sky.” So God created the great creatures of the sea and every living thing with which the water teems and that moves about in it, according to their kinds, and every winged bird according to its kind. And God saw that it was good.
God blessed them and said, “Be fruitful and increase in number and fill the water in the seas, and let the birds increase on the earth.”
And there was evening, and there was morning—the fifth day.
Genesis 1:20-23

Paleontologists suggest that the paucity of Silurian and Early Devonian fish fossils is at least partly explained by the fact that early fish did not have bones but their body was supported by cartilage. This perishes more easily than bone that contains calcium.

We hope and pray that our Heavenly Father has hidden somewhere yet another divine Nature Reserve where exceptional conditions have preserved and protected Silurian and Early Devonian fish!


Ostracoderm

Ostracoderm
Image: e-education.net

From the turn of Silurian and Devonian there have been discoveries of fish that have bony protetction.  Adam has given them a generic name ostracoderm (Gr. shell skin).  These early fish do not have jaw bone. This is the oldest known fish type so far found in the oceans and dates to Early Devonian. As far as I know no fossil has been found so that would link these animals to earlier life forms in Silurian seas.

Ostracoderm fossil
Image: Haysvilles community library

Great catch of fish at Gogo, Kimberley

Riding in Kimberley cattle station
Home Valley Station East Kimberley  WA

Gogo fish- wikipedia text

The fossils of the Gogo formation display three-dimensional soft-tissue preservation of tissues as fragile as nerves and embryos with umbilical cords.Over fifty species of fish have been described from the formation, and arthropods (including phylocarids and eurypterids) are similarly well-preserved. Nautiloids, goniatites and tentaculids are also known from the formation, but their soft tissue is not preserved.

The calcareous concretions formed around objects from the shallow reef areas which sank into the deep anoxic basins. The concretions sometimes contain the remains of fish, whose bodies are often preserved complete in three-dimensions due to rapid encasement and the slow rate of decay in the oxygen-poor surroundings. By repeated baths in a dilute acid solution, the matrix is dissolved away via a process of acid etching to reveal delicate fish fossils, some retaining impressions of soft tissues.

The discovery of Materpiscis, a placoderm preserved with an embryonic juvenile still attached by its umbilical cord, has revealed that at least some placoderms gave birth to live young. wikipedia

Fascinating book about Gogo fish
John Long, Victoria museum Melbourne
Swimming in Stone: the Amazing Gogo Fossils of the Kimberley
Fremantle: Fremantle Arts Centre 2007.