© Henskens Fossils & John v. Straaten
THE PLEISTOCENE ERA
proboscideans (mammoths also) are classified into species mainly by
characteristics of the teeth (e.g. the number of enamel plates). With most
mammals, a new tooth grows vertically. With elephants, however, it grows
horizontally. In total elephants will have 24 teeth during their life (six per
corner). If the sixth and last tooth is worn away, the animal is condemned to
die of starvation. If we assume that mammoths could get as old as modern
elephants, their maximum age was about 60 years.
The ancestor of all mammoths is the African mammoth (Mammuthus africanavus), which originated in the Middle-Pliocene and died out about about three to four million years ago. About three million years ago the first mammoths appeared in
One million years ago the climate changed. The temperature became colder, and this changed the landscape in
Approximately 300,000 years ago in
M. primigenius is the last species of the Mammuthus family. If people say ‘mammoth’, they usually refer to the woolly mammoth. About 20,000 to 30,000 years ago the woolly mammoth was also able to reach
Woolly mammoths are well-known because of their finds in the Siberian permafrost (constantly frozen soil). The animals are often so well-preserved that even skin, flesh and hair remain. In Europe, fishing boats often find remains in their nets, especially on the North Sea between
At the end of the Pleistocene, 10,000 years ago, a lot of big mammals like the cave bear, cave lion, giant deer, steppe wisent, but also the mammoth, died out. On the one hand this was caused by the changing climate (it became warmer, so that the vegetation changed), on the other hand because of the influence of humans, which rose in number and developed more efficient hunting techniques.
Only a few mammoth populations could survive on a number of islands that were still attached to the main land during the last ice age. When the sea level rose they could not return, and because of the limited food supply on the islands they evolved into dwarf forms. Remains of these so-called pygmy mammoths have been found on Wrangel island, which lies about 200 km north of
The straight-tusked elephant (Elephas antiquus) lived in
Cave bears were mainly herbivores.
Just like most modern bears, they probably ate dead animals now and then, but
only rarely will have killed prey themselves. They hibernated, for which they
usually used a cave (hence their name). Some animals died during their winter
sleep (because of their old age, or because they had not built enough fat
reserves in the autumn), and in some European caves (for example in
The ancestors of
the woolly rhino (Coelodonta antiquitatis) came from
Officially called Megaloceros giganteus, the giant deer is an extinct deer
that lived in Eurasia, from
The steppe wisent (Bison priscus) was a bison found on steppes in
Europe, Central Asia, Beringia and
Aurochs (Bos primigenius)
The aurochs evolved in Asia
about 2 million years ago and reached Europe, Middle East and
The lion evolved in
The cave lion is considered to be a subspecies of the extant lion (Panthera leo) and lived from about 300,000 to 10,000 years ago, during the Pleistocene era (although some finds indicate it may have lived until as recently as 2000 years ago in the Balkans). It ranged across Europe and Asia, from
They probably preyed on the large, herbivorous animals of their time. Their extinction may have been related to the Holocene extinction event, which wiped out most of their prey. Cave paintings and remains found in the refuse piles of ancient camp sites indicate that they were hunted by early humans, which may also have contributed to their extinction.
The cave lion is one of the biggest cats that ever lived. It was about 25 % bigger than the modern African lion, and averaged 3.5 m in length, with a typical male weighing between 335 and 400 kg, and a typical female weighing 175 kg. The Siberian tiger and the South American Smilodon (which was the largest of the saber-toothed cats) are both smaller. Only. P. leo fossilis and P. leo atrox were a little bigger than the cave lion.
Until the late Pleistocene the lion was the most widespread large land mammal beside humans. They were found in most of Africa, much of Eurasia from western Europe to
Cave hyena (Crocuta crocuta
Hyenas seem to have originated about 25 million years ago (mya) from an arboreal civet-like ancestor in
Cave hyena (Crocuta crocuta spelaea)
The hippo is a large, mostly plant-eating
African mammal, one of the only two extant species in the family Hippopotamidae
(the other being the Pygmy Hippo from central
Despite their resemblance to terrestrial even-toed ungulates, their closest living relatives are cetaceans. The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago. The earliest known hippo fossils date to around 16 mya, found in
During the Pleistocene hippos also ranged throughout North Africa and
Epileptobos groeneveldtii , Axis lydekkeri and Rusa sp.
These fossils were found in
Trinil is very well known due to the excavations of the famous Dutch geologist and anatomist Eugene Dubois (1858 – 1940). Trinil is the first hominid site that was described outside
The Kedung Brubus fauna includes a huge extinct pangolin, the proboscideans Stegodon and the fossil elephant Elephas hysudrindicus, the large tiger species that is also known from Trinil, a hyena, otter, tapir, the Javan and Indian rhino and a hippo species. This implies an open landscape with rivers.
The Ratites, long-legged walking birds that can’t fly,
appeared in the
The elephant bird (Aepyornis titan) was the largest of the Aepyornis family. It could become three to four m high and weigh
The name ‘elephant bird’ comes from an old Arab legend, which tells of a large bird, the ‘Rukh’, that grabbed elephants and lifted them in the air. The giant bird in the legendary book ‘Thousand and One Nights’ with Sinbad the Sailor was probably also an elephant bird. It became extinct in the 17th century.
Description on Marsupials
A kangaroo is a
herbivorous marsupial from the family Macropodidae (macropods, meaning ‘large
foot’). Besides the well-known larger species such as the red and grey
kangaroo, the family also includes many smaller species which include the
wallabies, tree kangaroos, wallaroos, pademelons and the quokka, more than 60
living species in all. The bigger species are endemic to
Kangaroos arose in the early Miocene, but, being grazers, they prospered in the Pliocene and Pleistocene, after
This is a very rare extinct species of wallaby known only from the
The genus Macropus includes the (eastern and western) grey kangaroo, the red kangaroo, wallaroos and some wallabies.
M. giganteus (the grey kangaroo) is an extant species. However, the grey kangaroos in the Pleistocene were much larger than their modern descendants.
M. titan is an extinct giant form of the grey kangaroo. It was flat-faced and about twice as big as the modern grey kangaroo. Some scientists regard it as a pre-dwarfing version of M. giganteus (as a sub-species, M. giganteus titan)
M. siva is a rare Macropus species from eastern
Protemnodon is a genus of macropods that existed in
P. anak was one of the biggest Protemnodons, with a weight of at least 90 kilos, while P. roechus was one of the smallest.
Sthenurus is an extinct genus of the so-called short-faced kangaroo. The sthenurines became numerous about 2 million years ago. Fourteen species are now extinct, with a single related species (the banded hare-wallaby) surviving on two islands off the coast of
S. occidentalis was a leaf-eating kangaroo, about the size of a modern grey kangaroo. In order to grind tough leaves and shrubs it had powerful jaws and striations (sharp vertical ridges) on its teeth. The name ‘Sthenurus’ (Latin for strong-tailed) was derived from the first description of this group by Sir Richard Owen in the 19th century. He noted that the bones were undoubtedly kangaroo-like and suggestive of powerful hind limbs and strong tails.
S. gilli was a rather small sthenurine, with a body weight of about 20 kg.
This genus lived in the Pliocene and Pleistocene. They were browsers (while most other kangaroos are grazers), some could reach a body weight of 100 kg. T. minor was its smallest member with a body weight of approximately 40 kg.
Diprotodontids were adapted for life in a land of
forests. They were browsers with simple premolars and ate soft vegetation.
There were several species of diprotodons, which all lived in
Kolopsis torus lived in the late Miocene and was about 1.5 m long with a shoulder height of 80 cm. It was one of the first diprotodontids and relatively small. Later species were much larger.
Palorchestes parvus was characterized by retracted nasal bones, a narrow elongated rostrum and enlarged infra-orbital foramina capable of carrying large bundles of nerves and blood vessels probably supplying a trunk. It was about the size of a bull.
Zygomaturus trilobus got its name from its wide flaring
zygomatic arches. The Zygomaturus species were somewhat smaller than Diprotodon, and probably favoured the forested areas
of south-eastern and south-western
Diprotodon optatum was the largest marsupial that ever lived. It was 3 m long and 2 m tall at the shoulder, weighing about two tonnes. It existed from 1.6 million years ago until about 40,000 years ago, through most of the Pleistocene era. It inhabited open forests, wood- and grasslands, eating leaves, shrubs and grasses. D. optatum was first described in the 1830s by the famous British anatomist Sir Richard Owen.
T. carnifex is a member of the extinct thylacoleonid family,
whose members evolved in the Oligocene and are informerly known as ‘marsupial
lions’. T. carnifex was a leopard-sized
marsupial very distantly related to wombats. It was first described by the
distinguished British palaeontologist Sir Richard Owen in 1858. It weighed
about 120 kg and was the largest mammalian predator in
Sarcophilus is a genus of carnivorous marsupial best known for
its only living member, the Tasmanian Devil (S. harrisii). Three species are known, S. laniarius and S.
moornaensis are only known from Pleistocene fossils. D. harrisii can now only be found on
Perameles is a genus also called long-nosed bandicoots. A bandicoot is any of about 20 living species of small to medium-sized, rat-like terrestrial marsupial omnivores of the family Peramelidae. They feed on insects and plants and have a long, tapering snout and elongated hind legs.
Wombats are Australian herbivorous marsupials. They are short-legged, muscular quadrupeds, about one meter in length with a very short tail. They dig extensive burrow systems with rodent-like front teeth and powerful claws. They are mainly nocturnal animals. Their fur color can vary from a sandy color to brown, or from grey to black. There are three species, each around a meter in length and weighing between 20 and 35 kg: the Common Wombat (Vombatus ursinus), the Southern Hairy-nosed Wombat (Lasiorhinus latifrons) and the Northern Hairy-nosed Wombat (Lasiorhinus krefftii).
Bettongia leseur, also known as the Boodie or Burrowing Bettong, is a small extant marsupial related to the kangaroo. It belongs to the family Potoroidae, which includes the rat-kangaroos, potoroos and other bettongs. Fossils of this family appear in the Mid-Miocene. B. leseur is a small, rat-like marsupial with short, rounded ears and a lightly-haired, thick tail. It has a pointed rostrum and beady black eyes, hind limbs longer than the forelimbs and large hind feet. It is about the size of a wild rabbit, weighing about 1.5 kg.
Potorus is a small extant marsupial also known as a Potoroo. Potoroos are the same size as rabbits. They have long feet and toes to hop and have grey fur. They come out at night to feed on seeds, fungi and insects. The potoroos weight is 1.5-2.5 kg.
Megalania was a giant varanid lizard also known as the Giant Goanna, that lived
in the Pliocene and Pleistocene. It grew to lengths of at least 5 metres,
perhaps 7. At about 600 kg, it was several times as heavy as the largest living
goanna, the Komodo Dragon of Indonesia (Varanus
komodensis). It was probably an ambush killer and scavenger. Megalania is known only from fragmentary
material. It is the largest known land-dwelling lizard and belonged to the
family that includes the goannas or monitor lizards. It appears to have become
extinct around 40,000 years ago (although numerous people claim to have seen
very large lizards in
Members of the genus Tiliqua are
also called blue-tongued skinks. It contains some of the largest members of the
skink family. They are commonly called blue-tongued lizards in
Emydura is a genus of extant turtles, also called Australian short-necked turtles. The six species of the genus Emydura are webbed-footed and semi-aquatic river turtles. They are characterized by unusually short necks.
Pallimnarchus is an extinct genus of crocodile from the Pliocene and Pleistocene of Australia. The genus consists of only one species, P. pollens. It was about as big as a modern saltwater crocodile. It had conical ziphodont (serrated and curved posteriorally) teeth and probably specialized in ambushing prey like kangaroos and diprotodons in shallow water.
THE TERTIARY ERA (Pliocene, Miocene, Oligocene, Eocene and Paleocene) © Henskens Fossils & John v. Straaten
Carcharodon was a white shark species that lived in the Miocene and Pliocene. It must have grown to about 15-18 m in length. However, this is difficult to tell exactly, since a shark skeleton consists of cartilage that hardly fossilizes since it is very soft. What we do find a lot from sharks are their teeth. Not only because they are hard and have a big chance to be preserved, also because a shark constantly replaces them. A shark has several rows of teeth, and can produce up to 15,000 teeth during its life. Carcharodon teeth can be 20 cm long. The height of its wide open jaws must have been about 1.5 m. Its main food source were probably whales.
The Cainotheriidae are small artiodactyls (even-toed hoofed plant-eating mammals) that suddenly appeared in the Lower Oligocene of western Europe. Cainotherium looked like a hare. This is probably because it lived the same life style, a good example of convergent evolution. It is not related to hares, but has evolved similar adaptations as it occupied similar niches. Cainotherium became extinct in the Upper Miocene and left no descendants.
Messelornis cristata is a fossil rail-like
bird from the famous Messel Pit fossil site in
Collecting fossils from the Messel site requires a special technique. Once is fossil is discovered (by splitting the thin shale slabs) it needs to be kept wet. If the shale is allowed to dry out, then the fossil disintegrates. Then, still keeping the fossil damp, the shale is carefully removed from around the bones. Then the bones are coated with resin to hold them in place. Now, the whole slab is turned over and the other side of the fossil exposed in the same way. Eventually, the fossil is completely free from the rock and encased in resin.
M. cristata was about the size of a moorhen and earlier they were also classified in this group, the rails. It now appears, however, that the Messelornithidae are more related to the present crane family (Gruiformes). They had short wings, long legs and short toes. The tail feathers were long. On the head they had a helmet-shaped crest. The full skeleton is 25 to 30 cm in size.
The fishes Atractosteus starusi, Amphiperca multiformis, Thaumaturus intermedius and Palaeoperca proxima from the Fish page also come from this site.
is an extinct group of frogs. They lived mainly from the Eocene through
All these fishes come from the world-famous fossil locality of the
Green River Formation in
Titanotheriidae, also called Brontotheriidae, is
a family of extinct mammals from the order Perrisodactyla, that includes
horses, rhinos, and tapirs. They looked like rhinos but are probably related to
horses. They lived in the Eocene and Oligocene. The term “Brontothere” means
“thunder beast” in Sioux Indian language. Brontotheres have four toes on their
front feet and three on their hind feet. Their teeth are adapted to cutting leaves.
The history of this group is well known due to an excellent fossil record in
THE CRETACEOUS ERA © Henskens Fossils & John v. Straaten
As its name suggests, Aegyptosaurus
was discovered in
Alligators, caimans, gavials, and crocodiles belong to
the family Crocodylidae. Although this family has existed since the upper Triassic,
over 200 million years ago, reptiles which can definitely be classed as modern Crocodylidae
only appear in the fossil record about 80 million years ago. The group
Crocodylia consists of modern crocodiles, alligators, and gavials. Crocodilians
have a long head with nostrils at the tip of the snout, four legs projecting
sideways, heavy scales, a muscular tail, and partially webbed hind feet.
Crocodilians are semi-aquatic; they spend much of their time in water, but must
lay their eggs on land. Their extinct relatives share many skeletal features
with modern crocodilians, but were quite different. Some were small (less than
50 cm), lightly built, and probably preyed on insects and very small reptiles.
Others even walked on two legs, or had hind limbs longer than their forelimbs,
betraying their bipedal ancestry. The biggest croc that ever lived was Sarcosuchus
imperator. It lived about 110 million years ago in what is now northern
Elasmosaurus was a plesiosaur with an extremely long neck that
lived in the world sees in the late Cretaceous. Its name means “thin-plated
lizard”. This is because it had platelike bones in its pelvic girdle. It is the
longest plesiosaur that ever lived (about 14 m in length). More than half of
its length was neck, which had more than 70 vertebrae, more than any other
animal. It had a large body and four flippers for limbs, a small head with
sharp teeth, and probably ate fish, belemnites and ammonites. It was described
in 1868 by Edward Drinker Cope from fossils found in
Mosasaurs were carnivorous
marine reptiles with flippers that likely descended from varanid lizards. They
are named after the Dutch river Meuse where the fossils were first discovered. This
river runs next to the city of Maastricht, after which the period they lived in
(Upper Cretaceous) was named (Maastrichtian). These fossils were from the
species Mosasaurus hoffmanni. Mosasaurs dominated the shallow seas
worldwide during the late Cretaceous. They were top predators that ate almost
anything, even ammonites. Some fossil ammonites cary the bite marks of
Mosasaurus was the largest of all mosasaur types known. It could reach a length of 18 m, with a skull of almost 2 m. The lower jaw is loosely hinged to the skull with a moveable joint on each side just behind the teeth. This loose joint must have permitted the animal to swallow large prey, much as some living snakes do. Finds of mosasaur embryos inside the skeleton of adult specimens indicate that mosasaurs, just like ichthyosaurs, were viviparous and gave birth to live young.
These fishes come from the Santana Formation, in
Coelacanths evolved approximately 380 million years ago. Since no fossils of these fishes have been found in rocks from the Tertiary or younger, palaeontologists assumed they had died out at the end of the Cretaceous, 65 million years ago, together with the dinosaurs and other big reptiles. Until a Coelacanth was caught at a depth of 200 m off the coast of Madagascar in 1938. Closer investigation showed a population that consisted of several hundred specimens. In 1998, another Coelacanth population was found near Sulawesi, Indonesia. These modern Coelacanths grow to about 1.8 m in length. They are the last of the lobe-finned fishes. This class had four more subclasses in the Devonian, which are now all extinct. The bones of the pectoral and pelvic fins in lobe-finned fishes already clearly show a humerus, radius and ulna. Scientists used to think that the lung fishes were the direct ancestors of the amphibians, nowadays most palaeontologists think these were the lobe-finned fishes. In a group of lobe-finned fishes living in the Devonian, the swim-bladder evolved into lungs, when, for unknown reasons, they left the sea water.
Archaeopteryx, Confuciusornis is proof that birds evolved from reptiles.
Confuciusornis is about 25 million years younger than Archaeopteryx
and is the oldest known bird to have a toothless beak. However, the wings still
have three claws. It must have been a better flyer than Archaeopteryx
because it had lighter bones (in modern birds the bones are completely hollow
to save weight). The males were a little larger than the females and had two
very long, narrow tail feathers. Confuciusornis is found in deposits
from the Lower Cretaceous of the
Turtles are an ancient group of reptiles. The earliest
turtles were enormous, tortoise-like animals. Millions of years of evolution
resulted in some species adapting to life in the oceans. The earliest known
marine turtle fossils are about 110-150 million years old. Allopleuron
is known from Upper Cretaceous deposits of North America, northern Africa and
THE JURASSIC ERA © Henskens Fossils & John v. Straaten
Pterosaurs (‘flying reptiles’) evolved approximately 230 million years ago. They developed in the same period as the dinosaurs, at the end of the Triassic, and also had the same ancestors (the archosaurs, from which the crocodiles also evolved). The wing is formed by a greatly elongated fourth finger. From the top of this finger, a leathery skin stretched towards the thigh bone of the hind legs. The other three fingers formed a claw halfway the wing. The fifth finger was still present in early species (although already greatly reduced), but was gone in later forms. The wings could be folded backwards, so that pterosaurs were able to walk on their hind legs on the ground, supported by their wing claw.
More than 120 different species are known. The smallest had the size of a sparrow, the largest (Quetzalcoatlus) had a wing span of about 12 m. Just as in birds, pterosaur bones were hollow to save weight. It were the first vertebrates that were able to fly. Most species lived from insects and fishes, which they caught from the surface waters of the seas. Pterosaurs were probably active, warm-blooded animals. The ones with a large wing span must have been able to glide for a long time by using the thermal currents (upward movement of heated air). Just like many other reptile families, they became extinct at the end of the Cretaceous.
Pterosaurs are not the ancestors of birds. Birds developed in the Jurassic from small, carnivorous reptiles (probably dinosaurs), and pterosaurs and birds still shared the skies for almost 100 million years.
Rhamphorhynchus had a long tail. Its name
means “beak snout”. It had a wingspan of 1 m and a long tail stiffenened with
ligaments which ended in a vane. It probably ate fish and it is believed that
one of the ways it hunted was by dragging its beak in the water, catching fish,
and tossing them into its throat pouch, a structure similar to that of
pelicans, which has been preserved in some specimens. Although fossils have
been found in
Scaphognathus had a skull length close to 12 cm and a wingspan of about 90 cm. It had a characteristically broad jaw, relatively short tail and short wings in comparison to other rhamphorhynchoids and a broad sternum. Compared to Rhamphorhynchus, the teeth pointed downward instead of forward.
altivelis, Allothrissops salmoneus, Allothrissops mesogaster, Tharsis dubius,
Ascalabos voithii, Pachytrhissops, and Leptolepides sprattiformis
All these fishes come from
the world-famous fossil Lagerstätte of Solnhofen near
Horsehoe crabs are distant relatives of spiders
and probably descended from the ancient eurypterids (sea scorpions). They
evolved in the Cambrian with other primitive arthropods like the trilobites.
Horseshoe crabs are one of the oldest classes of marine arthropods, and are
often referred to as "living fossils", as they have not changed much
in the last 350 to 400 million years. Limulus
polyphemusis one of the few surviving species of Limulus, and it closely resembles Mesolimulus
walchi. They are found in the Gulf of
Mexico and along the northern Atlantic coast of
Pseudorhina is related to the recent squatinids, the so-called
angel sharks, bottom-dwelling sharks with a ray-like shape. They are an ancient
lineage, first appearing in the fossil record about 150 million years ago
during the late Jurassic period. The remains of articulated angel sharks are
known from the marine deposits of Solnhofen, southern
The genus Pseudorhina is extinct but it has close relationships with the genus Squatina which has 15 extant members.
reptiles of which the ancestors lived on land, but later decided to go back to
sea (possibly under pressure of the dinosaurs, which dominated on land). Their
body shape looks a lot like that of a dolphin (but with a vertical instead of a
horizontal tail, and four instead of two flippers). Just like dolphins (mammals
which later also returned to sea), ichthyosaurs had lungs and had to come to
the surface now and then to breathe. More than 80 species are known, of which
the biggest one (Shonisaurus) could reach
They lived on fish, ammonites and belemnites. Ichthyosaurs have, in comparison
to the rest of their body, the biggest eyes of all animals. Species of the
genus Temnodontosaurus even had the biggest eyes ever, with a diameter
Since the skeleton is as good as complete, this
ichthyosaur must have drifted at the surface only for a short while after its
death, before it started to sink. The deeper it sank, the more the chest and
lungs were compressed. The body’s centre of gravity moved into the direction of
the head. As a consequence, such ichthyosaurs often sank towards the sea bottom
head first, with a speed of ± 1.5 m/s. When it collided with the sea floor, the
snout broke into several pieces, and also the skull was damaged. Approximately
This ichthyosaur is mentioned in a German scientific article about ichthyosaurs which sank to the sea bottom head first (Der Ichthyosaur vom Hauensteiner Nebelmeer, H. Hänggi, 2007, Naturforschende Gesellschaft des Kantons Solothurn).
THE TRIASSIC ERA © Henskens Fossils
& John v. Straaten
THE PERMIAN ERA © Henskens Fossils & John v. Straaten
Archegosaurus belongs to the
Labyrinthodontia, a group of extinct amphibians. They were the first vertebrates
to conquer land in the Devonian. The Labyrinthodontia evolved from the Crossopterygii,
a class of lobe-finned fishes, consisting of lungfish and coelacanths. In a group of lobe-finned
fishes living in the Devonian, the swim-bladder evolved into lungs, when, for
unknown reasons, they left the sea water. Archegosaurus could reach a
length of 1 m. Together with Sclerocephalus and Actinodon it
belonged to the biggest amphibians of
Discosauriscus was an amphibium that lived in the early Permian.
Lots of its fossils have been found in deposits of fresh water lakes in central
and western Europe, especially in the
was a salamander that lived about 280 million years ago (in the Lower-Permian)
of what is now south-western
Micromelerpeton was an
amphibian that lived in the Permian in what is now southwestern
Orthacanthus is a fresh water shark that lived
in the Upper Carboniferous and Lower Permian of Europe and
Fossils of complete sharks are rare as their skeleton is from cartilage which is much softer than bone.
THE CARBONIFEROUS ERA © Henskens Fossils & John v. Straaten
Ferns are vascular
plants that differ from the more primitive lycophytes in having true leaves,
and from the more advanced seed plants in lacking seeds. Unlike the other
vascular plants, the flowering plants and conifers, where the adult plant grows
immediately from the seed, ferns reproduce from spores. Ferns are (relatively)
delicate plants that only grow in areas with moist conditions. They favour
sheltered areas under the forest canopy, along creeks and streams and other
sources of permanent moisture.
Ferns first appear in the fossil record in the Lower Carboniferous, meaning they were already around for two hundred million years before the flowering plants evolved. By the Triassic, the first evidence of ferns related to several moden families appeared. The first modern families evolved in the Upper Cretaceous.
THE DEVONIAN ERA © Henskens Fossils & John v. Straaten
The first armored fishes developed in the Lower Ordovician. They belong
to the class Agnathans, the first vertebrates, which were still jawless. Most
species lacked paired fins, and only possessed a tail fin. Many species also
did not have a dorsal fin. For compensation, they had protrusions on the head
shield that served as a stabilizer. They swam using only their tail. The
Agnathans also included non-armored fishes. This class became extinct at the
end of the Devonian. A second class which includes armored fishes are the
Placoderms. As opposed to the Agnathans, they had jaws and paired fins. They
already die out in the Lower Carboniferous.All armored fishes had an amazing
exoskeleton, consisting of a head shield, and, for the Placoderms, hard, bony
plates halfway the body. Their length varied from a few centimeters to 6 m (Dunkleosteus).
Besides protection against predators, the armor also served to support the
Rhinopteraspis is an Agnathan. Although lacking paired fins, the pteraspids were probably powerful swimmers. Stability was provided by the wing-like outgrowths from the back of the head shield. A large spine over the back acted as a kind of dorsal fin while two rigid 'wings' or keels functioned as pectoral hydrofoils. The long, flexible tail was also hydrodynamic, with the lower lobe elongated to provide lift at the front of the body during swimming. Additional lift was provided by the elongated snout, which was drawn out into a bladelike 'rostrum', below which the mouth opened. The rostrum may have served a dual purpose, both hydrodynamic and used to probe the mud and sediment for small organisms.
Coccosteus is a genus of arthrodire placoderm (“arthrodire” means “jointed neck”, with well developed neck joints between head shield and trunk shield). Its fossils have been found throughout Europe and
Pterichthyodes is a genus of placoderm fish from the Devonian period. It had heavily armored heads and front bodies, while their tail ends were uncovered. As placoderms, they were members of one of the first group of animals to possess jaws, though they had grinding plates rather than teeth. They are distinguished easily from other placoderms by their odd wing-like appendage where fins would be found on a modern fish ("pterichthys" is ancient Greek for “wing-fish”). Pterichthyodes was first described by the famous Scottish geologist Hugh Miller (1802 – 1856) and bearing his name in recognition. At the time, these fossils were among the oldest vertebrates ever discovered.
Gyroptychius is an extinct genus of coelacanthiform lobe-finned fish from the Devonian period. It was a fast riverine predator with an elongated body about 30 cm long. As it eyes were relatively small, it is presumed to have hunted by smell rather than by sight. It had short jaws which gave it a powerful bite. All its fins except the pectorals were moved to the back of the body, increasing the power of the tail while swimming.
The eurypterids were the largest known arthropods that ever lived. They are members of the extinct class Eurypterida. The largest, such as Pterygotus, reached 2 m or more in length, but most species were less than 20 cm. They were formidable predators that lived in warm shallow water in the Cambrian to Permian from 510 to 250 million years ago. Eurypterids were the most fearsome swimming predators of the Paleozoic. Although called "sea scorpions", only the earliest ones were marine (most became brackish or freshwater animals), and they were not true scorpions. The typical eurypterid had a large, flat, semicircular carapace, followed by a jointed section, and finally a tapering, flexible tail, with a long spine at the end. Some eurypterids have paddles, which were used to propel themselves through water. They had four pairs of jointed legs for walking, and two small claws at the front. Some species may have been amphibious, emerging onto land for at least part of their life cycle. They may have been capable of breathing both in water and in air.
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