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Source: ucmp.berkeley.edu/help/timeform.php
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Earth during the late Precambrian, circa 650 million years ago
This map illustrates the break-up of the supercontinent, Rodinia, which formed 1100 million years ago, and the positions of the resulting continents as at 650 million years ago.
The Precambrian Era comprises all of geologic time prior to 600 million years ago. The Precambrian was originally defined as the era that predated the emergence of life in the Cambrian Period. It is now known, however, that life on Earth began by the early Archean and that fossilised organisms became more and more abundant throughout Precambrian time.
The two major subdivisions of the last part of the Precambrian are the Archean (oldest) and the Proterozoic. Rocks younger than 600 Mya are considered part of the Phanerozoic.
Credit: Plate tectonic maps and Continental drift animations by C. R. Scotese, PALEOMAP Project (www.scotese.com)
Photo: © 2010, C. R. Scotese
Proximal source: www.scotese.com/precambr.htm
Text: Various sources
Banded iron formation
The coloured bands in this rock reveal a dramatic increase in atmospheric oxygen, a critical moment for the evolution of life on Earth.
More than three billion years ago, cyanobacteria in our planet's young oceans began to produce oxygen through photosynthesis. This oxygen combined with dissolved iron in the sea to form insoluble iron oxide, which separated out of the water and sank to the seafloor.
As it settled, bands of red and grey iron oxide developed between layers of silica-rich sediment. The intricate and dramatic layers in this rock signal a turning point in Earth's history: the Great Oxygenation Event, or GOE. This led to an increased diversity of life forms and the appearance of new minerals.
Before the Great Oxygenation Event, the Earth's atmosphere was primarily made up of nitrogen (N2), carbon dioxide (CO2), and trace gases. There was almost no free oxygen, and the only fixed nitrogen made available to the first bacteria was produced by lightning strikes.
As cyanobacteria began producing oxygen, the levels of free O2 in the atmosphere started to increase. However, this oxygen was initially absorbed by various materials on Earth, including dissolved iron in the oceans, forming banded iron formations. Once these sinks were saturated, free oxygen began to accumulate in the atmosphere.
Cyanobacteria also possess the ability to fix atmospheric nitrogen through the enzyme nitrogenase, which catalyses the conversion of nitrogen gas (N2) into ammonia (NH3) or related nitrogen compounds that can be used to form amino acids, nucleotides, and other essential biological molecules.
However, the oxygen levels still remained low for almost 2 billion years after the Great Oxygenation Event. The exact reason for these low oxygen levels is still a mystery.
The oxygen levels eventually increased substantially when plants evolved, and separated nitrogen fixation from photosynthesis. Plants themselves do not have the ability to fix nitrogen directly. They rely instead on diazotrophic bacteria (bacteria that can fix nitrogen) that live in or on their roots. This process is called symbiotic nitrogen fixation.
Source: Western Australia, circa 2.6 billion years old, AQ-PEG-2016-33. This rock was donated by Rio Tinto and came from the traditional lands of the Eastern Guruma People in the Pilbara region of Australia.
Photo: Don Hitchcock 2018
Proximal source: The Natural History Museum, London
Text: The NHM and various other sources
The Ediacarian
The Ediacaran is a geological period of the Neoproterozoic Era that spans 96 million years from the end of the Cryogenian Period at 635 Mya to the beginning of the Cambrian Period at 538.8 Mya. It is the last period of the Proterozoic Eon as well as the last of the so-called 'Precambrian supereon', before the beginning of the subsequent Cambrian Period marks the start of the Phanerozoic Eon, where recognisable fossil evidence of life becomes common.
The Ediacaran Period is named after the Ediacara Hills of South Australia, where trace fossils of a diverse community of previously unrecognised lifeforms (later named the Ediacaran biota) were first discovered by geologist Reg Sprigg in 1946. Its status as an official geological period was ratified in 2004 by the International Union of Geological Sciences (IUGS), making it the first new geological period declared in 120 years.
Text above from Wikipedia.
Dickinsonia costata Ediacara, Australia.
Dickinsonia is a genus of extinct organism, most likely an animal, that lived during the late Ediacaran period in what is now Australia, China, Russia, and Ukraine. It is one of the best known members of the Ediacaran biota. The individual Dickinsonia typically resembles a bilaterally symmetrical ribbed oval. Its affinities are presently unknown; its mode of growth has been considered consistent with a stem-group bilaterian affinity, though various other affinities have been proposed. It lived during the late Ediacaran (final part of Precambrian). The discovery of cholesterol molecules in fossils of Dickinsonia lends support to the idea that Dickinsonia was an animal, though these results have been questioned.
Dickinsonia fossils are known only in the form of imprints and casts in sandstone beds. The specimens found range from a few millimetres to about 140 cm in length, and from a fraction of a millimetre to a few millimetres thick. They are nearly bilaterally symmetric, segmented, round or oval in outline, slightly expanded to one end (i.e. an egg-shaped outline). The rib-like segments are radially inclined towards the wide and narrow ends, and the width and length of the segments increases towards the wide end of the fossil. The body is divided into two by a midline ridge or groove, except for a single unpaired segment at one end, dubbed the 'anterior-most unit' suggested to represent the front of the organism. It is disputed whether the segments are offset from each other following glide reflection, and are thus isomers, or whether the segments are symmetric across the midline, and thus follow true bilateral symmetry, as the specimens displaying the offset may be the result of taphonomic distortion. The number of segments/isomer pairs varies from 12 in smaller individuals to 74 in the largest Australian specimens.
The body of Dickinsonia is suggested to have been sack-like, with the outer layer being made of a resistant but unmineralised material. Some specimens from Russia show the presence of branched internal structures. Some authors have suggested that the underside of the body bore cilia, as well as infolded pockets.
Dickinsonia is suggested to have grown by adding a new pair of segments/isomers at the end opposite the unpaired 'anterior-most unit'. Dickinsonia probably exhibited indeterminate growth (having no maximum size), though it is suggested that the addition of new segments slowed down later in growth. Deformed specimens from Russia indicate that individuals of Dickinsonia could regenerate after being damaged.
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Text: Adapted from Wikipedia
Aspidella terranovica Ediacara, Australia.
Aspidella consists of disk-shaped fossils, with concentric rings and/or centripetal rays. The diameter of circular Aspidella varies from 1 to 180 mm. Most individuals are between 4 and 10 mm, but smaller individuals would presumably have decayed before they could fossilise. Other Aspidella take the form of ellipses, 3–8 cm long and 1–4 cm wide. Most have a central pimple. The rim of all specimens is made up by ridge-edged rays and/or concentric rings.
The rarity of large individuals probably indicates that Aspidella were r-strategists, producing numerous offspring of which most died young. It is most common in deep-water sediments, but is a constituent of most Ediacaran fossil assemblages, including those deposited above storm wave-base. The organisms can reach densities of more than 3000 per square metre.
Just like Ediacaria, Aspidella has initially been considered a scyphozoan jellyfish. This initial designation has been refuted; some specimens have been shown to be the holdfast of some organism, the main body of which extended into the open water but broke off before fossilisation (a few specimens bearing stubs of stalks opposed to the central pimple support this); whereas others represent microbial colonies.
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Text: Adapted from Wikipedia
Earth during the Cambrian, circa 510 million years ago
A mollweide (equal-area) projection map of Earth 510 million years ago, overlain by a black outline of present-day countries in their respective locations.
( Note that Avalonia was a microcontinent in the Palaeozoic era. Crustal fragments of this former microcontinent underlie southwest Great Britain, southern Ireland, and the eastern coast of North America. It developed as a volcanic arc on the northern margin of Gondwana. It eventually broke off, becoming a drifting microcontinent - Don )
The Cambrian was the first period of the Palaeozoic Era, lasting from 542 to 488 million years ago. Prior to the Cambrian, the majority of living organisms were small, unicellular and poorly preserved. It was a time of rapid evolution, when the basic body plans of most modern animals were established. This period is known as the 'Cambrian Explosion' because of the relatively short time it took for such a diversity of life to appear.
Animals included invertebrates like trilobites, graptolites, molluscs, brachiopods, echinoderms, corals, and sponges. Vertebrates (animals with back bones) also appear in the Cambrian, and fish-like creatures swam in the oceans for the first time. All these animals lived in water.
The Cambrian was also characterised by a warmer global temperature than the present day.
The Cambrian was a time of greenhouse climate conditions, with high levels of atmospheric carbon dioxide and sometimes low levels of oxygen in the atmosphere and seas. Upwellings of anoxic deep ocean waters into shallow marine environments led to extinction events, whilst periods of raised oxygenation led to increased biodiversity.
Some Cambrian curiosities are still with us today. Animals such as sponges, jellyfish and anemones look fairly similar to their Cambrian ancestors.
The term Cambrian is derived from the Latin version of Cymru, the Welsh name for Wales, where rocks of this age were first studied. It was named by Adam Sedgwick in 1835, who divided it into three groups; the Lower, Middle, and Upper. He defined the boundary between the Cambrian and the overlying Silurian, together with Roderick Murchison, in their joint paper 'On the Silurian and Cambrian Systems, Exhibiting the Order in which the Older Sedimentary Strata Succeed each other in England and Wales'. This early agreement did not last.
Due to the scarcity of fossils, Sedgwick used rock types to identify Cambrian strata. He was also slow in publishing further work. The clear fossil record of the Silurian, however, allowed Murchison to correlate rocks of a similar age across Europe and Russia, and on these he published extensively. As increasing numbers of fossils were identified in older rocks, he extended the base of the Silurian downwards into Sedgwick's 'Upper Cambrian', claiming all fossilised strata for 'his' Silurian series.
Matters were complicated further when, in 1852, fieldwork carried out by Sedgwick and others revealed an unconformity within the Silurian, with a clear difference in fauna between the two. This allowed Sedgwick to now claim a large section of the Silurian for 'his' Cambrian and gave the Cambrian an identifiable fossil record. The dispute between the two geologists and their supporters, over the boundary between the Cambrian and Silurian, would extend beyond the life times of both Sedgwick and Murchison. It was not resolved until 1879, when Charles Lapworth proposed the disputed strata belong to its own system, which he named the Ordovician.
The term Cambrian for the oldest period of the Palaeozoic was officially agreed in 1960, at the 21st International Geological Congress. It only includes Sedgwick's 'Lower Cambrian series', but its base has been extended into much older rocks.
Text: Various sources, including Wikipedia
Image: Scotese, Christopher R.; Vérard, Christian; Burgener, Landon; Elling, Reece P.; Kocsis, Ádám T
Permission: Creative Commons Attribution 4.0 International, via Wikipedia
Text on map added by Don Hitchcock
Life on the platform margin of the Miaolingian sea, North China, during the Cambrian. Based on data from the Linyi Lagerstätte.
Drawing by Dinghua Yang.
Photo: Zhixin Sun, Fangchen Zhao, Han Zeng, Cui Luo, Heyo Van Iten, Maoyan Zhu.
Permission: Creative Commons Attribution 4.0 International
Cephalopods
This image is a reconstruction of Plectronoceras, arguably the earliest known crown-group cephalopod, dating to the Upper Cambrian. Its 14 known specimens come from the basal Fengshan Formation (north-east China) of the earliest Fengshanian stage. None of the fossils are complete, and none show the tip or opening of the shell.
Approximately half of its shell was filled with septa; 7 were recorded in a 2 cm shell. Its shell contains transverse septa separated by about half a millimetre, with a siphuncle on its concave side. Its morphology matches closely to that hypothesised for the last common ancestor of all cephalopods, and the Plectronocerida have been said to be the ancestors of the Ellesmerocerids, the first 'true cephalopods'.
Image: Entelognathus, via Wikipedia
Permission: Creative Commons Attribution-Share Alike 4.0 International licence.
Text: Wikipedia
Earth during the Middle Ordovician, circa 465 million years ago
A mollweide (equal-area) projection map of Earth 465 million years ago, overlain by a black outline of present-day countries in their respective locations.
( Note that Avalonia was a microcontinent in the Palaeozoic era. Crustal fragments of this former microcontinent underlie southwest Great Britain, southern Ireland, and the eastern coast of North America. It developed as a volcanic arc on the northern margin of Gondwana. It is shown here after breaking away from Gondwana, becoming a drifting microcontinent - Don )
Image: Scotese, Christopher R.; Vérard, Christian; Burgener, Landon; Elling, Reece P.; Kocsis, Ádám T
Permission: Creative Commons Attribution 4.0 International, via Wikipedia
Text on map added by Don Hitchcock
Avalonia was a microcontinent in the Paleozoic era. Crustal fragments of this former microcontinent underlie south-west Great Britain, southern Ireland, and the eastern coast of North America. It is the source of many of the older rocks of Western Europe, Atlantic Canada, and parts of the coastal United States. Avalonia is named for the Avalon Peninsula in Newfoundland. (wikipedia)
Life during the Ordovician period (485.4–443.8 million years ago) was diverse and included many different types of marine and land animals and plants:
Marine life
The Ordovician period saw a tripling of marine diversity, with the appearance of many new life forms, including starfish, brittle stars, crinoids, and echinoids. Other marine life included graptolites, trilobites, brachiopods, conodonts, cephalopods, corals, gastropods, red and green algae, and primitive fish.
Graptolites
Graptolites were colonial animals that lived in an interconnected system of tubes. From an initial ’embryonic’, cone-like tube (the sicula), subsequent tubes (thecae) are arranged in branches (stipes) to make up the whole colony (rhabdosome). Each individual animal is called a zooid.
Stomochord: The most distinguishing characteristic of the Hemichordates (which include the graptolites) is a more primitive form of notochord, called a stomochord, that contained a nerve system. The notochord is a cartilaginous skeletal rod supporting the body.
The peduncle is a stalklike part by which an organ is attached to an animal's body, or by which a barnacle or other sedentary animal is attached to a substrate.
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Text: Various sources
Graptolites
Monograptus spiralis
Monograptus is a genus of graptolites in the order Graptoloidea. This particular genus is the last stage of the graptoloid evolution before its extinction in the early Devonian. A characteristic of the genus includes one uniserial stipes (stalk/branch) with very elaborate thecae. This particular genus contains large number of graptolite species and may not be monophyletic.
Taking advantage of the spaces left available at the end of the Cambrian, brachiopods, molluscs, echinoderms (sea stars, crinoids and sea urchins) multiplied and diversified. Thus, some spaces disappeared and new ones continually appeared.
Specimen from the Czech Republic.
Photo: Don Hitchcock 2015
Text and source: Muséum de Toulouse
Additional text: Various sources
Graptolite nomenclature
Didymograptus, a 'tuning fork' graptolid, showing the main parts of the rhabdosome.
Photo and text: www.bgs.ac.uk, BGS © UKRI
Crinoid
Crinoids are an ancient fossil group that first appeared in the seas of the Middle Cambrian.
Stalked crinoids today live only in the deep ocean, in
quiet water below the lighted zone where it is too dark for
predators to see them. Because they are attached to the
seafloor and can't escape, they would be too vulnerable
to predators in lighted shallow water.
They live and die in such deep water that they are not washed onto beaches by
currents or waves. Living stalked crinoids were originally studied
by dredging in deep water. Now they are also studied by
scientists in deep-sea submersibles. During much of the
Palaeozoic Era (245—5 70 million years ago), stalked
crinoids lived in shallow water where predators could see
them. Apparently they were able to do this because Palaeozoic predators were less efficient than modern predators, the bony fishes.
Text: Wikipedia
Photo: www.fossils-facts-and-finds.com/crinoid.html
Trilobite
Trilobites (meaning three lobes") form one of the earliest known groups of arthropods.
Trilobites existed from the Early Cambrian, and flourished until the Devonian.
By the time trilobites first appeared in the fossil record, they were already highly diversified and geographically dispersed. Because trilobites had wide diversity and an easily fossilised mineralised exoskeleton, they left an extensive fossil record.
Trilobites evolved into many ecological niches. Some moved over the seabed as predators, scavengers, or filter feeders, and some swam, feeding on plankton. Some even crawled onto land. The largest trilobites were more than 70 cm long and may have weighed as much as 4.5 kg.
Text: Wikipedia
Photo: samnoblemuseum.ou.edu
Land life
The Ordovician period saw the first colonisation of land by plants and arthropods. Plants likely evolved in the ocean, then moved to freshwater, and finally to land. The first animals to leave the ocean were probably modified arthropods.
Other life
The Ordovician period also saw the evolution of jawless fish, which were the first true vertebrates. These bottom-feeders were covered in armour plates.
Reconstruction of an early jawless fish, Arandaspis, from central Australia.
Arandaspis looked like a tube of bony plates about 15 cm long, with headlamp style forward-facing eyes and a circular mouth. It had no fins, and probably lived on the sandy bottom of the sea eating small animals it sucked out of the sediments.
It lived in the Ordovician period, about 480 to 470 million years ago.
Photo: Nobu Tamura
Permission: Creative Commons Attribution-Share Alike 3.0 Unported
Text: Long (2024)
The Ordovician period ended with a mass extinction that was the second largest in history.
Earth during the Middle Silurian, circa 430 million years ago
A mollweide map of Earth at the middle of the Silurian, 430 million years ago, overlain by a black outline of present-day countries in their respective locations.
The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago (Mya), to the beginning of the Devonian Period, 419.2 Mya. The Silurian is the third and shortest period of the Palaeozoic Era, and the third of twelve periods of the Phanerozoic Eon. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by a few million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when up to 60% of marine genera were wiped out.
One important event in this period was the initial establishment of terrestrial life in what is known as the Silurian-Devonian Terrestrial Revolution: vascular plants emerged from more primitive land plants, and three groups of arthropods (myriapods, arachnids and hexapods) became fully adapted to the land.
Vascular plants are plants that have lignified (woody) tissues (the xylem) for conducting water and minerals throughout the plant. They also have a specialised non-lignified tissue (the phloem) to conduct products of photosynthesis. The group includes most land plants other than mosses.
Another significant evolutionary milestone during the Silurian was the diversification of jawed fish, which include placoderms, acanthodians (which gave rise to cartilaginous fish) and osteichthyan (bony fish, further divided into lobe-finned and ray-finned fishes) although this corresponded to sharp decline of jawless fish such as conodonts and ostracoderms.
Image: Scotese, Christopher R.; Vérard, Christian; Burgener, Landon; Elling, Reece P.; Kocsis, Ádám T
Permission: Creative Commons Attribution 4.0 International, via Wikipedia
Text on map added by Don Hitchcock
Gnathostome, reconstruction.
Gnathostomata are the jawed vertebrates. Gnathostome diversity comprises roughly 60 000 species, which accounts for 99% of all living vertebrates, including humans. Most gnathostomes have retained ancestral traits like true teeth, a stomach, and paired appendages (pectoral and pelvic fins, arms, legs, wings, etc.). Other traits are elastin, a horizontal semicircular canal of the inner ear, myelin sheaths of neurons, and an adaptive immune system which has discrete lymphoid organs (spleen and thymus).
It is now assumed that Gnathostomata evolved from ancestors that already possessed a pair of both pectoral and pelvic fins. Until recently these ancestors, known as antiarchs, were thought to have lacked pectoral or pelvic fins. In addition to this, some placoderms (extinct fish with bony plates) were shown to have a third pair of paired appendages, that had been modified to claspers in males and basal plates in females — a pattern not seen in any other vertebrate group.
The Osteostraci (bony armoured jawless fish) are generally considered the sister taxon of Gnathostomata.
Jaw development in vertebrates is likely a product of the supporting gill arches. This development would help push water into the mouth by the movement of the jaw, so that it would pass over the gills for gas exchange. The repetitive use of the newly formed jaw bones would eventually lead to the ability to bite in some gnathostomes.
In Devonian waters, the body of armoured fish was protected by bony plates.
All have a cartilaginous skeleton and fins, which are covered with 'placoderm' plates or protected by an ostracoderm shell.
All Placoderms and Ostracoderms (except for lampreys and hagfish) disappeared at the end of the Devonian period.
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Text: Adapted from Wikipedia
Life reconstruction of Shenacanthus vermiformis
Dawn of Fishes—Early Silurian Jawed Vertebrates Revealed Head to Tail
Editor: LI Yuan | Sep 29, 2022, Nature, Prof. ZHU Min
The Gnathostomata or jawed vertebrates, which include not only almost all the backboned animals you see in zoos and aquariums but humankind as well, have a mysterious origin. The so-called molecular clock, which deduces the age of the most recent common ancestor of two animals by evaluating the difference between the two sets of DNA, suggests that the most recent common ancestor of all modern jawed vertebrates lived 450 million years ago during the Ordovician period. As a result, the origin of jaws cannot be later than that.
However, the fossil record of jawed vertebrates only becomes abundant from the Early Devonian (~419 million years ago), i.e., the beginning of the "Age of Fishes." Only in the past 10 years have scientists found several complete jawed fishes from the Late Silurian (~425 million years ago). Even so, these records are still more than 25 million years later than when jaws should have originated. The dearth of earlier fossils means that jawed vertebrates are a 'ghost lineage' in the early Silurian.
The remarkable discovery of complete early Silurian jawed fishes is the result of 20 years of continuous effort by the authors searching for fossil fishes in all possible Silurian rock strata in China. The breakthrough was finally made in late 2020, when complete early Silurian fishes were found in Xiushan County, Chongqing.
Shenacanthus vermiformis is very small, it is an early shark relative. However, all the sharks we know are covered in tiny scales, or at most small mosaic plates. Shenacanthus instead has prominent 'shoulder armour' made of several large plates that completely encircle its body. This feature, thought to be exclusive to placoderms, provides a strong hint that the first cartilaginous fishes were armoured, similar to placoderms.
'Only 20 years ago it was still believed that sharks are primitive and other jawed fish evolved from a shark-like archetype. Now with the discovery of Shenacanthus, we can finally make certain that the opposite is true' said Prof. ZHU You'an.
Image by ZHANG Heming ( If only all reconstructions were as superbly rendered as this one is. It is a work of art - Don)
Text: english.cas.cn/research/highlight/palaeontology/202209/t20220928_320888.shtml
Editor: LI Yuan | Sep 29, 2022
Long (2024) has a delightful background story to the above:
The oldest early shark known from an almost complete body fossil is Shenacanthus from Chongquing, South China, which lived around 437 MYA. Its discovery was quite serendipitous. Three young Chinese palaeontologists were messing around play-fighting when one kung-fu kicked another into a roadside cliff-face. Some rocks came tumbling down, and one split to reveal a hidden treasure of a spectacular fossil fish inside it. This turned out to be the oldest known complete fossil fish with jaws ever found! They couldn't believe their luck.
With further digging they found a layer rich in complete skeletons of early fishes including Shenacanthus. It was a small fish, about an inch long, with bony plates covering the top of the skull and enveloping its chest area. It has pectoral fins without spines yet bears a stout dorsal fin spine similar to that of the acanthodians.
Jaws with teeth have not been found on the specimen, so teeth might well have been absent. Strange tooth whorls that belong to a stem shark called Qianodus were also found in rock layers of this age in China. They are not the same as shark teeth with sharp-pointed cusps - these would not develop in sharks until the Devonian period.
Shenacanthus might bridge the gap between sharks and another early jawed fish group called placoderms ('plated skin'). Placoderms appear in the Early Silurian at exactly the same time.
I feel compelled to add here that John Long's book, 'The Secret History of Sharks' should have a prominent place on every enthusiast's bookshelf. It is superbly written, the author is a leading researcher and publisher, a world-leading palaeontologist, and for decades has been on the cutting edge of shark research. He is Strategic Professor in Palaeontology at Flinders University in Adelaide, South Australia. I found the book un-put-downable - Don
Platystoma plebium (above) is a fossil gastropod, or snail, that lived in the Silurian period about 400 million years ago. It has been found in the Waldron Shale Formation of St. Paul, Indiana, and is often encrusted with tubeworms.
Gastropods have been around since the Late Cambrian period.
There are 611 known families of gastropods, with 202 families being extinct and only appearing in the fossil record.
The class Gastropoda has the second largest number of named species, after insects.
Photo: Don Hitchcock 2015
Provenance: Indiana
Source: Muséum de Toulouse
Dalmanites Limulurus is a trilobite, a member of the Order Phacopida, Family Dalmanitidae from the Silurian Clinton Group, Rochester Formation deposits, near Rochester, New York.
The species name is derived from perceived similarities in appearance to the modern-day horseshoe crab Limulus.
Size: Circa 50 mm.
Photo: Don Hitchcock 2015
Provenance: New York
Source: Muséum de Toulouse
Text: Adapted from www.fossilmuseum.net
Eurypterus lacustris
Eurypterus is an extinct genus of eurypterid, a group of organisms commonly called 'sea scorpions'. The genus lived during the Silurian period, from around 432 to 418 million years ago. Eurypterus is by far the most well-studied and well-known eurypterid. Eurypterus fossil specimens probably represent more than 95% of all known eurypterid specimens.
There are fifteen species belonging to the genus Eurypterus , the most common of which is Eurypterus remipes, the first eurypterid fossil discovered and the state fossil of New York.
Members of Eurypterus averaged at about 13 to 23 cm in length, but the largest individual discovered was estimated to be 60 cm long. They all possessed spine-bearing appendages and a large paddle they used for swimming. They were generalist species, equally likely to engage in predation or scavenging.
Photo: Don Hitchcock 2015
Provenance: Buffalo, New York
Source: Muséum de Toulouse
Text: Adapted from Wikipedia
Cyathophyllum caespitosum
Cyathophyllum caespitosum is a species of extinct coral from the order Tabulata, which existed primarily in the Silurian and Devonian periods.
The species is found as a fossil in marine sedimentary rocks, with notable fossils located in regions of what are now Europe, North America, and parts of Asia.
Cyathophyllum caespitosum typically formed bushy or mound-like colonies, often encrusting the seabed or forming dense clumps. These colonies would have a characteristic irregular, branching structure. The corallites, which are the skeletal cups that house the polyps, were generally small but distinct, with a well-developed septal arrangement (radial partitions inside the corallite). The polyps within these corallites were likely small and colonial.
The skeleton of this species is composed of calcium carbonate (CaCO3), forming a rigid structure typical of tabulate corals. The surface of the coral often showed growth in a lamellar or layered fashion.
Cyathophyllum caespitosum lived in shallow marine environments, likely forming part of the reef ecosystem. As a colonial coral, it would have been a filter feeder, relying on plankton and organic matter suspended in the water column. Like many corals, it may have had symbiotic relationships with photosynthetic organisms, such as zooxanthellae, in clearer, shallow waters with adequate sunlight.
The fossilised remains of Cyathophyllum caespitosum provide valuable insights into the marine environments and ecological systems of the Silurian and Devonian periods.
Its fossil form, particularly the structure of the colonies and corallites, is used in the study of ancient coral communities and can help palaeontologists understand the diversity and distribution of ancient reef-building organisms.
In summary,Cyathophyllum caespitosum is an extinct, tabulate coral species that formed bushy or mound-like colonies in shallow marine environments. It played a role in reef ecosystems during the Silurian and Devonian periods, and its fossil remains are important for understanding ancient coral communities and marine life of the Palaeozoic.
Photo: Don Hitchcock 2015
Provenance: Huccorgne, Liege, Belgium
Source: Muséum de Toulouse
Text: Various sources
Scyphocrinites elegans is a crinoid that lived from the late Silurian to early Devonian (430 - 415 million years ago). Its fossils have been found in Asia, North America, Europe, and Africa.
Scyphocrinites elegans is an extinct type of echinoderm related to sea stars and sea urchins. Crinoids like Scyphocrinites elegans are often referred to as 'sea lilies' due to their plant-like appearance, though they are marine animals.
Like most crinoids, Scyphocrinites elegans had a long, stalk-like structure that anchored it to the seafloor. The body was composed of a cup-shaped 'calyx' at the top of the stalk, which housed the mouth and digestive organs. From the calyx, the animal would have extended feathery, branched arms that were used to capture food from the water column, typically plankton and small particles. The size of Scyphocrinites elegans could vary, but crinoids in general range from a few centimetres to several metres in height, depending on the species.
One of the key features of Scyphocrinites elegans was its elegant and elaborate arrangement of arms, which were often finely branched. The individual 'plates' that made up its calyx were well-defined, and it had a relatively ornate appearance, hence the species name 'elegans'. The arms and calyx would have been adapted for filter feeding in the currents.
Scyphocrinites elegans would have lived in shallow marine environments, where it anchored itself to the substrate and relied on the movement of water to bring it food. Its filter-feeding behaviour would have been typical for crinoids, as they trap microscopic organisms suspended in the water using their arms, which are lined with tube-like structures called pinnules.
Text: Various sources
Upper photo:
Photo: Don Hitchcock 2015
Provenance: Near Merzouga, a small village in southeastern Morocco.
Source: Muséum de Toulouse
Lower photo:
Silurian, 416 million years old
Origin: Morocco, Erfoud. Exhibited at the Musée des Confluences, in Lyon
Photo: Vassil
Permission: Creative Commons CC0 1.0 Universal Public Domain Dedication
A mollweide map of Earth 390 million years ago, during the middle Devonian, overlaid by a black outline of present-day countries in their respective locations.
The Devonian was a geologic period that lasted from 419.2 to 358.9 million years ago, and was part of the Paleozoic era. It was a time of significant evolutionary advancements for fish, and is known as the 'Age of Fishes'.
Other notable events during the Devonian include:
The appearance of seed plants and terrestrial tetrapods
The onset of the Late Palaeozoic Ice Age
The first vertebrates moved onto land
The collision of the continents of Laurentia and Baltica, which formed the Caledonian Mountains
Much of the Northern Hemisphere was covered by Panthalassa, a huge 'world ocean'. Much of the land was covered by shallow seas, where tropical reef organisms lived.
Large areas of shallow sea in North America, central Asia, and Australia became basins where rock salt, gypsum, and other minerals precipitated.
A mass extinction event caused by lack of oxygen occurred near the end of the Devonian.
This lack of oxygen prohibited decay and allowed the preservation of organic matter. This, combined with the ability of porous reef rocks to hold oil, has led to Devonian rocks being an important source of oil, especially in Canada and the United States.
The Devonian period is named for the red-coloured sediments generated when North America collided with Europe. These rocks were first studied in Devon, England.
Text above: Various sources
Image: Scotese, Christopher R.; Vérard, Christian; Burgener, Landon; Elling, Reece P.; Kocsis, Ádám T
Permission: Creative Commons Attribution 4.0 International, via Wikipedia
Text on map added by Don Hitchcock
Urasterella asperula, Devonian Age, Hunsrück Slate, Bundenbach, Germany.
This exceptional specimen appears to be pyritised, which enhances its natural beauty, and leads to very detailed fossils.
Hunsrück is one of the few marine Devonian Lagerstätte having soft tissue preservation, and in many cases fossils are coated by a pyritic surface layer. Preservation of soft tissues as fossils normally requires rapid burial in an anoxic (i.e., with little or no oxygen) sedimentary layer where the decomposition of the organic matter is significantly slowed. The pyritisation found in Bundenbach fossils facilitated preservation and enhanced the inherent beauty of the fossils.
Pyritisation is rare in the fossil record, and is believed to require not only rapid burial, but burial in sediments both low in organic matter, and high in concentrations of sulphur and iron. Such pyritisation is also prevalent in the lower Cambrian fossils from the Maotianshan shales of Chengjiang, China, the oldest Konservat Lagerstätte of Cambrian time.
The best localities for exceptionally preserved fossils are in the communities of Bundenbach and Gemünden. The slates were widely quarried in the past, mainly for roofing tiles from small pits, of which over 600 are known. Today, only a single quarry remains open in the main fossiliferous region of Bundenbach. There are also areas of the Hunsrück Slates where fossils are neither well preserved, nor pyritised, indicating that there also existed environments with shallow and fully oxygenated water.
( Note also the extreme care and ultimate professionalism of the curators of the museum in presenting the fossil in the best possible way. This is what dedication, artistry, and a deep knowledge of difficult procedures can produce - Don )
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Text: Adapted from Wikipedia
Hapalocrinus frechi
Devonian period
Palm Tree Crinoid
370 - 360 million years ago
Like most crinoids, Hapalocrinus frechi had a stalk that anchored it to the seafloor, from which branched a cup-shaped body known as the calyx. The calyx housed the mouth and digestive organs. Extending from the calyx were the arms, which were equipped with feathery structures used for feeding and capturing plankton.
Hapalocrinus frechi was relatively large for a crinoid, with the stalk typically reaching a length of several metres.
The arms of Hapalocrinus frechi were long and branched, characteristic of crinoids, and equipped with pinnules (smaller feathery structures) for filtering food from the water.
The stalk was composed of calcareous ossicles (small calcium carbonate plates) that helped provide rigidity and stability. The structure of the stalk allowed the animal to stay anchored while it extended its arms to feed on plankton.
Hapalocrinus frechi lived in shallow to moderately deep marine environments, often in areas with strong currents where plankton and other food sources were abundant. The crinoid was probably a filter feeder, using its arms to capture microscopic organisms from the water.
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Text: Various sources
The most severe of the Late Devonian ocean anoxia events was the Kellwasser Event.
The Late Devonian extinction consisted of several extinction events in the Late Devonian Epoch, which collectively represent one of the five largest mass extinction events in the history of life on Earth. The term primarily refers to a major extinction, the Kellwasser event, also known as the Frasnian-Famennian extinction, which occurred around 372 million years ago, at the boundary between the Frasnian age and the Famennian age, the last age in the Devonian Period.
Image: Sarah K. Carmichael, Johnny A. Waters, Peter Königshof, Thomas J. Suttner, Erika Kido.
Source: www.sciencedirect.com/science/article/abs/pii/S0921818118306258
Cladoselache
A modern restoration of the Devonian Chondrichthyan Cladoselache fyleri
Photo and text: EvolutionIncarnate
Permission: Creative Commons Attribution-Share Alike 4.0 International licence
Cladoselache is an extinct genus of shark-like chondrichthyan (cartilaginous fish) from the Late Devonian (Famennian) of North America. It was similar in body shape to modern lamnid sharks (such as mako sharks and the great white shark), but was not closely related to lamnids or to any other modern (selachian) shark. As an early chondrichthyan, it had yet to evolve traits of modern sharks such as accelerated tooth replacement, a loose jaw suspension, enameloid teeth, and possibly claspers.
Some 20th century studies considered Cladoselache to be a basal (early-diverging) member of Elasmobranchii, the fork of cartilaginous fish which leads to modern sharks and rays.[1] More recent studies have identified distinctive traits of the chondrocranium (cartilaginous braincase), dorsal fin spines, and pectoral fin bases.[2][3][4] These newly identified features support a close relationship to symmoriiforms, a small group of bizarre chondrichthyans such as the bristle-spined Stethacanthus. Cladoselache and symmoriiforms may be more closely related to chimaeras (a modern group of unusual deep-sea fish) than to true sharks and rays.
Growing to several metres in length, Cladoselache is considered to have been a fast-moving and fairly agile marine predator due to its streamlined body and deeply forked tail. From both an anatomical and historical perspective, is one of the best known of the early chondrichthyans in part due to an abundance of well-preserved fossils, discovered in the Cleveland Shale on the south shore of Lake Erie. In addition to the cartilaginous skeleton, the fossils were so well preserved that they included traces of skin, muscle fibres, and internal organs, such as the kidneys.
The anatomy of Cladoselache shows a mixture of derived and ancestral characteristics. The skeleton is composed of tessellated cartilage, a complex tissue unique to chondrichthyans. Tessellated cartilage combines flexible cartilage fibers with a loose mosaic of irregular calcified plates, known as tesserae.
The head shape of Cladoselache shares some similarities with modern frilled sharks, while its overall streamlined body shape is reminiscent of mackerel sharks in the family Lamnidae, which likely had a similar ecology. The largest undisputed skeleton of Cladoselache was about 2.0 metres in length, though many specimens were much smaller.
Photo: Don Hitchcock 2015
Source: Facsimile, resin cast, Muséum de Toulouse
Provenance: Cleveland, Ohio
Text: Wikipedia
Skeletal diagram of Cladoselache fyleri in top-down view (top) side on (centre) and from below (bottom).
Photo and text: EvolutionIncarnate
Permission: Creative Commons Attribution-Share Alike 4.0 International licence
Dunkleostus
https://thedaily.case.edu/tag/devonian-period/
Latimeria chalumnae, a Coelacanth, often called a living fossil.
The oldest known Coelacanth fossils date back more than 410 million years, in the Devonian. Coelacanths were thought to have become extinct in the Late Cretaceous, around 66 million years ago, but were discovered living off the coast of South Africa in 1938.
Note that no date was given by the museum for this specimen, but the three dimensionality and the detail is of such high quality that it appears to be a modern catch.
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Earth during the Carboniferous, circa 330 million years ago
A mollweide (equal-area) projection map of Earth 330 million years ago, overlain by a black outline of present-day countries in their respective locations.
Image: Scotese, Christopher R.; Vérard, Christian; Burgener, Landon; Elling, Reece P.; Kocsis, Ádám T
Permission: Creative Commons Attribution 4.0 International, via Wikipedia
Text on map added by Don Hitchcock
Earth during the Triassic, circa 225 million years ago
A mollweide (equal-area) projection map of Earth 225 million years ago, overlain by a black outline of present-day countries in their respective locations.
Image: Scotese, Christopher R.; Vérard, Christian; Burgener, Landon; Elling, Reece P.; Kocsis, Ádám T
Permission: Creative Commons Attribution 4.0 International, via Wikipedia
Text on map added by Don Hitchcock
Animal bones let alone entire skeletons are rarely found in the layers of the Bunter sandstone. Nevertheless, the animals from this period have left us traces of life, as was the case in Rotfelden near Calw. This site is one of the richest in fossils in the Bunter sandstone and was the scene of a 'dinosaur meeting' 250 million years ago, in the Lower Triassic.
A river had flooded a large area, which then dried up again. Numerous animals left their footprints in the wet mud, which soon dried out and became rock-hard under the scorching power of the sun. The next flood then filled the footprints with sediment. The five-fingered track of the hand-held animal has long been known, but the animal itself has only recently been discovered: it is a rauisuchier, a relative of the crocodiles - probably Arizonasaurus.
In the coarse-grained Bunter sandstone, bones normally dissolve completely when water seeps in. This makes the fossil find from 1967 in the quarry near Rotfelden all the more fascinating: a wonderful skull of the armored amphibian Eocyclotosateus, colored violet by the mineral vivianite.
Vivianite (Fe 3(PO4)2 .8H2O) is a hydrated iron(II) phosphate mineral found in a number of geological environments. Small amounts of manganese Mn2+, magnesium Mg2+, and calcium Ca2+ may substitute for iron Fe2+ in its structure. Pure vivianite is colourless, but the mineral oxidises very easily, changing the colour, and it is usually found as deep blue to deep bluish green prismatic to flattened crystals. Vivianite crystals are often found inside fossil shells, such as those of bivalves and gastropods, or attached to fossil bone. Vivianite can also appear on the iron coffins or on the corpses of humans as a result of a chemical reaction of the decomposing body with the iron enclosure.
Photo: Don Hitchcock 2015
Source and text: Naturkunde Museum Stuttgart, State Museum of Natural History, Stuttgart
Additional text: Various sources, including Wikipedia
Land vertebrates
Remains of land vertebrates are very rare in the Bunter Sandstone. Usually they are just individual bones that have been embedded in river deposits. The individual bones have usually been worn down by long transport in rivers. More robust bones such as vertebrae or parts of skulls have less 'transport damage' than fine bones, which are often completely destroyed. The purple colour of the fossils is due to the mineral vivianite, which was formed after deposition.
Disintegrated skeleton of the Giraffe-necked lizard Tanystropheus antiquus
Upper Buntsandstein Rotfelden near Nagold
Tanystropheus antiquus is a European species from the latest part of the Early Triassic (late Olenekian stage). Tanystropheus antiquus had a proportionally shorter neck than other Tanystropheus species, so some palaeontologists consider that Tanystropheus antiquus deserves a separate genus, Protanystropheus.
Numerous complete skeletons of small giraffe-necked lizards were found in Rotfelden. These animals, which were barely a metre long, did not yet have a 'giraffe neck'; one such species only developed in late-living relatives such as the giant Tanystropheus conspicuus, which you can see in the 'Fliorama Sea'. The giraffe-necked lizards of the Buntsandstein period probably lived on the banks of small rivers. There are numerous tracks there that are attributed to them.
Photo: Don Hitchcock 2015
Source and text: Naturkunde Museum Stuttgart, State Museum of Natural History, Stuttgart
Additional text: Wikipedia
Vegetation
Towards the end of the Palaeozoic era, the face of the Earth changed dramatically. Tectonic fermentation caused parts of what is now Europe to enter subtropical climate zones. At the same time, intense volcanism caused the carbon dioxide content of the atmosphere to rise. The result was a natural greenhouse effect. Both tectonics and climate change caused many plants to gradually die out. During the Bunter Sandstone period, which marks the beginning of the Mesozoic era (Triassic-Jurassic-Cretaceous), a 'new' plant world emerged.
Neuropteridium - Suggested fern structure: a) Whole plant Neuropteridium elegans, b) Neuropteridium elegans -single pinnula (PIZ 516), c) Neuropteridium voltzii - single pinnula (PIZ 156), d) Scolopendrites sp. fertile frond, e) Neuropteridium voltzii - entire frond, f) Neuropteridium elegans entire frond, Scolopendrites entire fertile organ.
Photo and text: Wachtler (2011), p 76
Bunter Sandstone The Buntsandstein predominantly consists of sandstone layers of the Lower Triassic series. Sulzbad (Soultz-les-Bains) in Alsace (France) This fern had a short trunk and simply feathered leaves. The feathering and the course of the leaf veins are clearly visible on the fossil on display.
Fern Anomopteris mougeotii
From the Upper Bunter Sandstone (Buntsandstein)
The feathered leaves of this fern are often found together with the club mosses Pleuromeia. This indicates that both plants thrived under similar living conditions.
Findspot: Pforzheim-Brötzingen
Photo: Don Hitchcock 2015
Source and text: Naturkunde Museum Stuttgart, State Museum of Natural History, Stuttgart
Additional text:
Anomopteris mougeotii – Suggested fern structure: a) Whole plant, b) Single bipinnate frond, c) Rachis and aphlebia, d) Fertile pinnae, d) Sterile pinnae.
Photo and text: Wachtler (2011), p 68
Fern Anomopteris mougeotii
From the Upper Bunter Sandstone (Buntsandstein)
The feathered leaves of this fern are often found together with the club mosses Pleuromeia. This indicates that both plants thrived under similar living conditions.
Findspot: Pforzheim-Brötzingen
Photo: Don Hitchcock 2015
Source and text: Naturkunde Museum Stuttgart, State Museum of Natural History, Stuttgart
Pleuromeia sternbergii, a club moss.
Left, complete specimen. Right, close up.
The specimen consists of a longitudinal break through the trunk
Upper Bunter Sandstone (Buntsandstein)
Club mosses are now usually low evergreen herbs with needlelike or scalelike leaves. Many species have conelike clusters of small leaves (strobili), each with a kidney-shaped spore capsule at its base. The plants are homosporous, meaning that they produce just one kind of spore. They have terrestrial or subterranean gametophytes that vary in size and shape depending on the genera. In some species, including nearly all those of the north temperate zone, the subterranean gametophyte is dependent upon an associated fungus for continued growth. This sexual phase alternates in the life cycle with the spore-producing plant, the sporophyte, which is aboveground and is formed following fertilisation.
However, in ancient times, clubmosses were particularly diverse in form: the spectrum ranged from small herbaceous species that resembled today's clubmosses to 40 metre high trees with richly branched, lush crowns. In addition to typical spore-dispersing forms, there were also those whose spores remained on the mother plant and formed a few cells there, including an egg cell that was then fertilised, almost like real seed plants.
Pleuromeia is a typical plant of the Bunter Sandstone, which probably grew near water as a pioneer plant. At the tip of the unbranched shoot was a single spore cone. The small leaves are an adaptation to the dry, hot climate. They reduce evaporation.
Spore plants: Spores are cells with an extremely resistant cell wall. They facilitate plant dispersal by wind. During the transition from water to land life, the development of spores played a major role, as they enabled early land plants to spread quickly. The great era of spore plants - these include mosses, club mosses, horsetails and ferns - was the Palaeozoic period.
The dominance of seed plants began during the Mesozoic era. At the same time, 'modern' families emerged among the spore plants, some of which have survived to this day.
Pleuromeia is an extinct genus of lycophytes related to modern quillworts (Isoetes). Pleuromeia dominated vegetation during the Early Triassic all over Eurasia and elsewhere, in the aftermath of the Permian – Triassic extinction event. During this period it often occurred in monospecific assemblages. Its sedimentary context in monospecific assemblages on immature paleosols, is evidence that it was an opportunistic pioneer plant that grew on mineral soils with little competition. It spread to high latitudes with greenhouse climatic conditions.
Findspot: Dietersweiter near Freudenstadt
Photo: Don Hitchcock 2015
Source and text: Naturkunde Museum Stuttgart, State Museum of Natural History, Stuttgart
Placodus gigas skeleton (cast) from the Upper Muschelkalk (shell-bearing limestone), Steinsfurt near Sinsheim.
Middle Triassic, 240 - 230 Mya.
Among the marine iguanas there were not only fast hunters. The Placodus-toothed lizards were clumsy animals with a rigid torso and weak arms and legs. The round teeth of the common species Placodus are regularly found in the Muschelkalk. With its large, flat teeth it cracked open mussels that it had previously picked out of the sand or rocks with its longer front teeth. This marine iguana had a series of thick bones on its back. In other flat-toothed lizards these bone plates were even more numerous and covered large parts of the torso and belly. This created a turtle-like shell. It is not yet known whether flat-toothed lizards had to go on land to lay their eggs like sea turtles or whether they gave birth to live offspring like many other podded lizards.
Placodus lizards were clumsy animals with a rigid torso and weak arms and legs. The round teeth of the common species Placodus are regularly found in the Muschelkalk limestone. This marine iguana had a series of thick bones on its back. In other Placodus lizards these bone plates were even more numerous and covered large parts of the torso and belly. This created a turtle-like shell. It is not yet known whether Placodus lizards had to go on land to lay their eggs like sea turtles or whether they gave birth to live offspring like many other podded lizards.
The Muschelkalk (shell-bearing limestone) is a sequence of sedimentary rock strata consisting of a sequence of limestone and dolomite beds in the geology of central and western Europe. It has a Middle Triassic (240 to 230 million years) age and forms the middle part of the three-part Germanic Trias (that gives the Triassic its name) lying above the older Buntsandstein and below the younger Keuper.
Findspot: Steinsfurt near Sinsheim
Photo: Don Hitchcock 2015
Source and text: Naturkunde Museum Stuttgart, State Museum of Natural History, Stuttgart
Skeletal restoration of Tanystropheus antiquus (now referred to its own genus Protanystropheus) from the Middle Triassic of Central Europe, based on Wild (1973: pl. 1) and specimens from the Upper Buntsandstein of the Black Forest.
Photo: Rupert Wild & Henk Oosterink
Permission: This image was published in an article by Grondboor en Hamer. Made available under the license CC BY 3.0 NL.
Source: commons.wikimedia.org/wiki/File:Tanystropheus_antiquus_skeletal_restoration.jpg
Armoured amphibian Eocyclotosaurus woschmidti skull
Middle Triassic, circa 247 - 242 Mya.
The name Eocyclotosaurus means 'dawn round-eared lizard'. It is characterised as a capitosauroid with a long and slender snout, closed otic fenestra, and small orbits.
Armoured amphibians were usually significantly larger than salamanders and frogs, their modern relatives. Their skulls were armoured all around with thick bone plates. Many also had bony scales on their belly. Most armoured amphibians lived in fresh water and fed on fish, as evidenced by fossil stomach contents. The Eocyclotosaurus, one of the numerous armoured amphibians of the Buntsandstein period, which was up to three metres long, was widespread. It is known not only from the Black Forest, but also from the Vosges of eastern France, England, and western North America.
Photo: Don Hitchcock 2015
Source and text: Naturkunde Museum Stuttgart, State Museum of Natural History, Stuttgart
Additional text: adapted from Wikipedia
Upper Bunter Sandstone Rotfelden near Nagold Skeleton reconstruction of Encyclotosaurus wosschmidti based on finds from Rotfelden and New Mexico USA.
Thrinaxodon sp.,
245 - 228 Mya
Thrinaxodon is an extinct genus of cynodonts, including the species T. liorhinus which lived in what are now South Africa and Antarctica during the Late Permian - Early Triassic. Thrinaxodon lived just after the Permian–Triassic mass extinction event, its survival during the extinction may have been due to its burrowing habits.
Similar to other therapsids, Thrinaxodon adopted a semi-sprawling posture, an intermediary form between the sprawling position of basal tetrapods and the more upright posture present in current mammals. Thrinaxodon is prevalent in the fossil record in part because it was one of the few carnivores of its time, and was of a larger size than similar cynodont carnivores.
Thrinaxodon was a small synapsid roughly the size of a fox and possibly covered in hair. The dentition suggests that it was a carnivore, focusing its diet mostly on insects, small herbivores and invertebrates. Their unique secondary palate successfully separated the nasal passages from the rest of the mouth, allowing the Thrinaxodon to continue mastication without interrupting to breathe, an adaptation important for digestion.
Cast in patinated resin.
Findspot: South Africa
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Horseshoe Crab
Tachypleus gigas Syn. Limulus mollucanus
250 Mya/Present, Lower Triassic.
( Note that it is not clear from the Museum's documentatioin whether this is a fossil or a modern example, but given its condition, it is likely a modern example - Don )
For modern horseshoe crabs, their earliest appearance was approximately 250 million years ago during the Early Triassic. Because they have seen little morphological change since then, extant (surviving) forms have been described as 'living fossils'.
Horseshoe crabs are arthropods of the family Limulidae and the only surviving xiphosurans. Despite their name, they are not true crabs or even crustaceans; they are chelicerates, more closely related to arachnids like spiders, ticks, and scorpions. The body of a horseshoe crab is divided into three main parts: the cephalothorax, abdomen, and telson. The largest of these, the cephalothorax, houses most of the animal's eyes, limbs, and internal organs. It is also where the animal gets its name, as its shape somewhat resembles that of a horseshoe.
Only four species of horseshoe crab are extant today. Most are marine, though the mangrove horseshoe crab is often found in brackish water. Additionally, certain extinct species transitioned to living in freshwater. Horseshoe crabs primarily live at the water's bottom but they can swim if needed. In the modern day, their distribution is limited, only found along the east coasts of North America and South Asia.
Merostamata comprises two groups of animals of marine ecosystems, i.e. sea scorpions (Euripterida) and horseshoe crabs (Xiphosura). The sea scorpions are an extinct group of animals, and thus the Merostamata are represented by only the living horseshoe crabs of Xiphosura in the present era. The merostomata is characterised with respiration by book gills, excretion by coxal glands, a prosoma with 6 pairs of appendages of which the first one with chelicerae (to help in capturing food), with the next four appendages used as walking legs, and the last one as a pusher leg. The first pair of ophisthosomal appendages are fused with the genital operculum, and the next five ophisthosomal appendages are modified into booklungs. This group of organisms are much closer to the sea spiders (extinct) and arachnids (Spiders and scorpions) rather than other aquatic crustaceans.
Findspot: Ile de Poulo-Condore, Vietnam
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Text: Adapted from Wikipedia
Additional text: Mohapatra (2020), Miquel (1838)
Phytosaur, Nicrosaurus kapffi
221 - 205 Mya.
Nicrosaurus is an extinct genus of phytosaur reptile existing during the Late Triassic period. Although it looked like a crocodile (and probably lived like the more terrestrial crocodylomorphs), it was not closely related to these creatures, instead being an example of parallel evolution. The main difference between Nicrosaurus (and all other phytosaurs) and modern crocodiles is the position of the nostrils – Nicrosaurus's nostrils, or external nares, were placed directly in front of the forehead, whereas in crocodiles, the nostrils are positioned on the end of the snout.
The genus was named by German paleontologist, Dr. Eberhard Fraas, in 1866, possibly after the Neckar river of southwestern Germany, near which it was found.
Photo: Don Hitchcock 2015
Source: Naturkunde Museum Stuttgart, State Museum of Natural History, Stuttgart
Text: adapted from Wikipedia
Phytosaur, Nicrosaurus kapffi, as in the above image.
This image shows clearly the position of the nostrils or external nares, in front of the forehead.
The animal was 4m to 6m long.
Photo: Don Hitchcock 2015
Source: Naturkunde Museum Stuttgart, State Museum of Natural History, Stuttgart
Text: adapted from Wikipedia
Earth during the Jurassic, circa 170 million years ago
A mollweide (equal-area) projection map of Earth 170 million years ago, overlain by a black outline of present-day countries in their respective locations.
Image: Scotese, Christopher R.; Vérard, Christian; Burgener, Landon; Elling, Reece P.; Kocsis, Ádám T
Permission: Creative Commons Attribution 4.0 International, via Wikipedia
Text on map added by Don Hitchcock
Ichthyosaurus communis
183 - 175.6 Mya
Early Jurassic
During the Early Triassic epoch, ichthyosaurs and other ichthyosauromorphs evolved from a group of unidentified land reptiles that returned to the sea, in a development similar to how the mammalian land-dwelling ancestors of modern-day dolphins and whales returned to the sea millions of years later, which they gradually came to resemble in a case of convergent evolution.
Ichthyosaurians were particularly abundant in the Late Triassic and Early Jurassic periods, until they were replaced as the top aquatic predators by another marine reptilian group, the Plesiosauria, in the later Jurassic and Early Cretaceous, though previous views of ichthyosaur decline during this period are probably overstated. Ichthyosaurians diversity declined due to environmental volatility caused by climatic upheavals in the early Late Cretaceous, becoming extinct around the Cenomanian-Turonian boundary approximately 90 million years ago.
Text: Wikipedia
Findspot: Holzmaden Germany
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Nautilus toarcensis
Lower Jurassic
Nautilus toarcensis is a species of nautilus that was described by d'Orbigny in 1850. It belongs to the Nautilidae family and the genus Cenoceras.
Findspot: Cruéjouls, Aveyron, France
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Arieten pflaster or ammonite pavement of the Lower Black Jurassic, Bodelshausen near Hechingen. 'Snail pavement' is what people call these layers with closely packed Arieten or ammonites.
The Black Jurassic or Black Jura (German: Schwarzer Jura) in earth history refers to the lowest of the three lithostratigraphic units of the South German Jurassic, the latter being understood not as a geographical, but a geological term in the sense of a lithostratigraphic super group.
The ammonites, which were up to the size of a wagon wheel - not snails, but cephalopods - were washed together before being embedded and deposited mixed with nautilids, mussels and driftwood.
Arietites is a genus of massive, giant evolute, psiloceratacean (Any ammonoid cephalopod of the superfamily Psilocerataceae) ammonites in the family Arietitidae in which whorls are subquadrate and transversely ribbed and with low keels in triplicate, separated by a pair of longitudinal grooves, running along the venter.
( The venter is the lower or ventral side of the ammonite's shell, which is the part that faces toward the organism's belly (as opposed to the dorsal side, which would be on top - Don ). In most ammonites, the venter is the side where the shell is more rounded and smooth. Fossils are known world wide from the lower Sinemurian stage of the Lower Jurassic.
Photo: Don Hitchcock 2015
Source: Naturkunde Museum Stuttgart, State Museum of Natural History, Stuttgart
Barracudasauroides panxianensis
Middle Triassic
Stage : Anisian from 247.2 million years ago until ~242 million years ago
Size and weight : 118 x 62 x 545 cm – 79.4 Kg
Barracudasauroides is a genus of mixosaurid ichthyosaur which lived during the Middle Triassic. Fossils of this genus have been found in Guizhou Province, China. It is known from GMPKU-P-1033, a partial skeleton recovered from the Upper Member of the Guanling Formation of Yangjuan village, Xinmin area; this rock unit dates to the Pelsonian substage of the Anisian stage. It was named by Michael W. Maisch in 2010, and the type species is Barracudasauroides panxianensis.
Findspot: China, Guizhou Province - Guanling Formation
Accession Number: MHNT.PAL.2006.80.6
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
This is a larger image of the above, 8133 x 3145 pixels, stitched together from four individual images.
Findspot: China, Guizhou Province - Guanling Formation
Accession Number: MHNT.PAL.2006.80.6
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Archaeodontosaurus descouensi, mandible.
Holotype of Archaeodontosaurus descouensi, Right mandible.
Archaeodontosaurus ('ancient-toothed lizard') is a genus of sauropod dinosaur from the Middle Jurassic. Its fossils were found in the Isalo III Formation of Madagascar. The type species, Archaeodontosaurus descouensi, was described in September 2005. The specific name honours the collector, Didier Descouens. It is a probable sauropod, with prosauropod-like teeth. It may be a basal member of Gravisauria.
Upper Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Lower Photo: Didier Descouens 2015
Source: Muséum de Toulouse
Permission: Creative Commons Attribution-Share Alike 4.0 International licence.
Dinosaurs in Swabia - The Middle/Upper Keuper, 233 - 200 Mya, the Upper Triassic. A herd of plateosaurs.
The river is a hive of activity. In the thickets under tall conifers, small mammals seek refuge not only from the heat, but also from nimble predators such as Saltoposuchus. The sturdy, heavily armoured eagle-headed lizards, on the other hand, can search for food in the undergrowth relatively undisturbed. A herd of plateosaurs has also gathered on the bank. Hardly anyone can pose a threat to these large dinosaurs. Perhaps Liliensternus, when he goes on the prowl with his own kind. The nutritious plateosaur eggs, on the other hand, have many interested parties. That is why the parents keep a close eye on them.
Plateosaurus was a bipedal herbivore with a small skull on a long, flexible neck, sharp but plump plant-crushing teeth, powerful hind limbs, short but muscular arms and grasping hands with large claws on three fingers, possibly used for defence and feeding. Unusually for a dinosaur, Plateosaurus showed strong developmental plasticity: instead of having a fairly uniform adult size, fully grown individuals were between 4.8 and 10 metres long and weighed between 600 and 4 000 kilograms. Commonly, the animals lived for at least 12 to 20 years, but the maximum life span is not known.
Photo: Don Hitchcock 2015
Source: Naturkunde Museum Stuttgart, State Museum of Natural History, Stuttgart
Araucaria mirabilis
164.7 - 161.2 Mya.
Araucaria mirabilis is an extinct species of coniferous tree from Patagonia, Argentina. It belongs to the genus Araucaria.
Araucaria mirabilis are known from large amounts of very well preserved silicified wood and cones from the Cerro Cuadrado Petrified Forest, including tree trunks that reached 100 m in height in life. The site was buried by a volcanic eruption during the Middle Jurassic, approximately 160 million years ago.
Araucaria forests were distributed globally and formed a major part of the woody flora of the Mesozoic era.
Middle Jurassic
Findspot: Argentina ( probably Cerro Cuadrado Petrified Forest - Don )
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Nautilus belauensis
Having survived relatively unchanged for hundreds of millions of years, nautiluses represent the only living members of the subclass Nautiloidea, and are often considered 'living fossils'.
Fossil records indicate that nautiloids have experienced minimal morphological changes over the past 500 million years. Many were initially straight-shelled, as in the extinct genus Lituites. They developed in the Late Cambrian period and became a significant group of sea predators during the Ordovician period. Certain species reached over 2.5 m in size. The other cephalopod subclass, Coleoidea, diverged from the nautiloids long ago and the nautilus has remained relatively unchanged since.
Findspot: Present day, Indo-Pacific Ocean
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Pterodactylus Kochi, viewed at one time as an immature form of Pterodactylus antiquus, but the matter is disputed.
155.7 - 150.8 Mya (Jurassic)
Provenance: Eichstätt, Germany
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Cresmoda obscura, Water strider.
155.7 - 150.8 Mya (Jurassic)
Provenance: Solnhofen, Germany
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Archaeopteryx lithographica, Syn. Archaeopteryx siemensii (the assessment as a synonym is now disputed) specimen displayed at the Natural History Museum, London. (This image shows the original fossil - not a cast.)
Circa 150 Mya, the Upper Jurassic.
This is the type specimen of the species, the one to which all others are compared. The NHM ranks it as the most valuable specimen in the Museum's collection.
Archaeopteryx was not like modern birds. It had feathers like a bird, but teeth, claws and a bony tail like a dinosaur.
The first skeleton of Archaeopteryx, known as the London Specimen (BMNH 37001), was unearthed in 1861 near Langenaltheim, Germany and perhaps given to a local physician Karl Häberlein in return for medical services. He then sold it for £700 to the Natural History Museum in London, where it remains.
Missing most of its head and neck, it was described in 1863 by Richard Owen as Archaeopteryx macrura, allowing for the possibility it did not belong to the same species as the first feather found.
In the subsequent 4th edition of his On the Origin of Species, Charles Darwin described how some authors had maintained 'that the whole class of birds came suddenly into existence during the eocene period; but now we know, on the authority of Professor Owen, that a bird certainly lived during the deposition of the upper greensand; and still more recently, that strange bird, the Archaeopteryx, with a long lizard-like tail, bearing a pair of feathers on each joint, and with its wings furnished with two free claws, has been discovered in the oolitic slates of Solnhofen. Hardly any recent discovery shows more forcibly than this how little we as yet know of the former inhabitants of the world.'
Photo: Don Hitchcock 2018
Proximal source: The Natural History Museum, London
Text: The NHM and various other sources including Wikipedia
Archaeopteryx lithographica
Circa 150 Mya, the Upper Jurassic.
Fossils of this type often have two matching halves, where the original slab has been split apart, and this is the case here.
This is the 'other half' of the fossil above. The outlines do not completely match, since exploratory work was conducted before it was realised that there was a fossil in the particular bed being investigated.
At this point, the slab was split into two, often a difficult and stressful operation requiring great expertise.
These matching fossils of the same object can be very important for understanding and further research.
Photo: Don Hitchcock 2018
Proximal source: The Natural History Museum, London
Text: The NHM and various other sources including Wikipedia
Reconstruction of Archaeopteryx on display at the NHM.
We are still learning about bird evolution from this fossil. The shape and arrangement of the wing feathers show similar adaptations for flight to modern birds.
Rephotography: Don Hitchcock 2018
Artist: Not listed
Proximal source and text: The Natural History Museum, London
Natural History Museum scientist Angela Milner led an international team that found further evidence that Archaeopteryx could fly by studying casts of its brain.
The diagram above shows the results of this ground breaking work.
Rephotography: Don Hitchcock 2018
Artist: Not listed
Proximal source and text: The Natural History Museum, London
Archaeopteryx lithographica Syn. Archaeopteryx siemensii (the assessment as a synonym is now disputed) specimen displayed at the Museum für Naturkunde in Berlin. (This image shows the original fossil - not a cast.)
Circa 150 Mya, the Upper Jurassic.
Findspot: Solnhofen Limestone, near Eichstätt in Germany
Photo: H. Raab (User: Vesta)
Permission: Creative Commons Attribution-Share Alike 3.0 Unported licence
Source: Museum für Naturkunde, Berlin, via Wikipedia
Marine crocodile Dakosaurus maximus lower jaw
Upper White Jura Painten, Franconian Alb
This lower jaw comes from the Franconian Jura. Individual teeth prove that Dakosaurus also lived where the Swabian Alb now stands.
The ancestors of crocodiles separated from the other dominant lizards (archosaurs) over 250 million years ago. The real crocodiles, however, only emerged much later, towards the end of the Triassic period.
Upper Jurassic 161 - 150 Mya
Photo: Don Hitchcock 2015
Source: Naturkunde Museum Stuttgart, State Museum of Natural History, Stuttgart
Marine crocodile Dakosaurus maximus skull.
Photo: Don Hitchcock 2015
Source: Naturkunde Museum Stuttgart, State Museum of Natural History, Stuttgart
Cricosaurus suevicus, SMNS 9808.
From Nusplingen in Baden-Württemberg.
Cricosaurus is an extinct genus of marine crocodyliforms of the Late Jurassic. belonging to the family Metriorhynchidae.
It was a relatively small reptile, with the body length of specimens ranging from 2 m to 3.2 m.
Its body was streamlined for greater hydrodynamic efficiency, which along with its finned tail made it a more efficient swimmer than modern crocodilian species.
The genus Cricosaurus comprises rather small and slender metriorhynchids, which likely preyed on fast-moving animals like squids and fish as evident by the small teeth and preserved belemnite rostra in the abdominal region of a specimen from Nusplingen.
Photo: Don Hitchcock 2015
Source: Naturkunde Museum Stuttgart, State Museum of Natural History, Stuttgart
Text: Various sources including Wikipedia
Earth during the Cretaceus, circa 105 million years ago
A mollweide (equal-area) projection map of Earth 105 million years ago, overlain by a black outline of present-day countries in their respective locations.
Image: Scotese, Christopher R.; Vérard, Christian; Burgener, Landon; Elling, Reece P.; Kocsis, Ádám T
Permission: Creative Commons Attribution 4.0 International, via Wikipedia
Text on map added by Don Hitchcock
Araripescorpius ligabuei
125 - 112 Mya
Scorpion, Lower Cretaceous.
Terrestrial carnivore.
Found: In an Aptian lacustrine - large carbonate in the Crato Formation of Brazil. It is the type species of Araripescorpius.
Findspot: Ceará, Araripe, Brazil
Photo: Don Hitchcock 2015
Text: Various sources
Source: Muséum de Toulouse
Frog, Lower Cretaceous.
Pipidae.
125 - 112 Mya
Present day Pipid frogs are highly aquatic and have numerous morphological modifications befitting their habitat. For example, the feet are completely webbed, the body is flattened, and a lateral line system is present in adults. In addition, pipids possess highly modified ears for receiving sound under water. They lack a tongue or vocal cords, instead having bony rods in the larynx that help produce sound. They range from 4 to 19 cm in body length.
Findspot: Ceará, Araripe, Brazil
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Text: Adapted from Wikipedia
Ginkgo sp.
112 - 99.6 Mya
Middle Cretaceous
Ginkgo is a genus of non-flowering seed plants, assigned to the gymnosperms. The scientific name is also used as the English common name. The order to which the genus belongs, Ginkgoales, first appeared in the Permian, 270 million years ago, and Ginkgo is now the only living genus within the order. The rate of evolution within the genus has been slow, and almost all its species had become extinct by the end of the Pliocene. The sole surviving species, Ginkgo biloba, is found in the wild only in China, but is cultivated around the world. The relationships between ginkgos and other groups of plants are not fully resolved.
Findspot: Lake Baikal, Siberia
Photo: Don Hitchcock 2015
Text: Various sources
Source: Muséum de Toulouse
Axelrodichthys araripensis.
Axelrodichthys is an extinct genus of mawsoniid coelacanth from the Cretaceous of Africa, North and South America, and Europe.
Mawsoniidae is an extinct family of prehistoric coelacanth fishes which lived during the Triassic to Cretaceous periods.
This specimen has been superbly prepared for display by the curators of Le Muséum d'Histoire Naturelle de Toulouse.
Several species are known, the remains of which were discovered in the Lower Cretaceous (Aptian-Albian) of Brazil, North Africa, and possibly Mexico, as well as in the Upper Cretaceous of Morocco (Cenomanian), Madagascar (Coniacian –Santonian) and France (Lower Campanian to Lower Maastrichtian).
The Axelrodichthys of the Lower Cretaceous frequented both brackish and coastal marine waters (lagoon-coastal environment) while the most recent species lived exclusively in fresh waters (lakes and rivers). The French specimens are the last known fresh water coelacanths. Most of the species of this genus reached 1 to 2 metres in length. Axelrodichthys was named in 1986 by John G. Maisey in honor of the American ichthyologist Herbert R. Axelrod.
Findspot: Brazil
Photo: Don Hitchcock 2015
Source: Muséum de Toulouse
Text: Adapted from Wikipedia
Skull of Triceratops_horridus (facsimile, original 70 Mya).
Triceratops is a genus of chasmosaurine ceratopsian dinosaur that lived during the late Maastrichtian age of the Late Cretaceous period in what is now western North America.
Triceratops travelled in herds. The horns and the frill of the herbivore were probably not primarily for defense, but probably served more for turf wars between males, comparable to modern antelopes and bulls.
Findspot: South Dakota, USA.
Photo: Don Hitchcock 2015
Source and text: Natural History Museum of Vienna
Additional text: Wikipedia
Skull of Tyrannosaurus rex (facsimile, original 70 Mya).
The huge predator Tyrannosaurus rex was among the last very successful dinosaurs. Like Triceratops, these animals were the victims of a meteor impact.
Findspot: South Dakota, USA.
Photo: Don Hitchcock 2015
Source and text: Natural History Museum of Vienna
Additional text: Wikipedia
The death of the large dinosaurs
Sixty-six million years ago, dinosaurs had the ultimate bad day. With a devastating asteroid impact, a reign that had lasted 180 million years was abruptly ended.
In 1980, Nobel Prize-winning physicist Luis Walter Alvarez and his geologist son Walter published a theory that a historic layer of Iridium-rich clay was caused by a large asteroid colliding with Earth.
The instantaneous devastation in the immediate vicinity and the widespread secondary effects of an asteroid impact were considered to be why the non-bird dinosaurs died out so suddenly.
The crater caused by the asteroid, called the Chicxulub crater, is centred on the Yucatán Peninsula in Mexico.
The asteroid is thought to have been between 10 and 15 kilometres wide, but the velocity of its collision caused the creation of a much larger crater, 150 kilometres in diameter. It is the second-largest crater on the planet.
Other life forms eradicated by the asteroid impact included the Ammonites and large marine reptiles.
Iridium is one of the rarest metals found on Earth. It is usually associated with extraterrestrial impacts, as the element occurs more abundantly in meteorites. The dinosaur-killing crash threw huge amounts of debris into the air and caused massive tidal waves to wash over parts of the American continents. There is also evidence of substantial fires from that point in history. The exact date of the dinosaur extinction is 66.05 million years ago.
The Vredefort impact structure is the largest verified impact structure on Earth. The crater, which has since been eroded away, has been estimated at 170–300 kilometres across when it was formed 2.023 billion (± 4 million) years ago.
Photo: © Don Davis, Via NASA Image and Video Library
Text: Adapted from www.science.org/doi/10.1126/sciadv.abe3647 and Wikipedia
References
- Long, J., 2024: The secret history of sharks, Quercus, London
- Miquel E. et al, 1838: Notice sur le genre Limulus et les especes qui y appartiennent, Bulletin des Sciences Physiques et Naturelles, pp 60, 61, Netherlands
- Mohapatra, A., 2020: Arthropoda : Merostomata, Faunal Diversity of Biogeographic Zones : Coasts of India, Chapter 25 pp 10-13, Director, Zoological Survey of India, www.researchgate.net/publication/348096901_Arthropoda_Merostomata
- Wachtler, M., 2011: Ferns and seedferns from the Early-Middle Triassic (Anisian) Piz da Peres (Dolomites - Northern Italy), in The Genesis of plants - Preliminary researches about the Early-Middle Triassic Fossil Floras from the Dolomites - A Compendium, Dolomythos, 60-79, Innichen.