A gallery of creatures

A GALLERY OF PERMIAN-TRIASSIC CREATURES.

This book focuses on the end-Permian extinction, but merely to provide graphical information about those organisms most immediately involved in the extinction event and its aftermath would fail to reveal its place in the great panorama of life on Earth. Many of the groups impacted by the extinction event had been around for hundreds of millions of years; some had previously and only narrowly escaped oblivion in the great extinctions at the end of the Ordovician Period, and that of the Late Devonian, only to meet their final fate at the end of the Permian. Other groups, such as the conifers and the therapsids were relatively newly evolved, and despite taking heavy losses, lived to thrive in its aftermath. This mini-gallery is an attempt to provide some sense of the "big picture" of the history of life on Earth, and the role the end-Permian extinction played in that history.

A few photos of actual fossils are included, but most are drawings, especially of larger organisms, which are often found in bits and pieces. The skeletons of vertebrates, for example, are commonly found disarticulated, that is, as separate bones, which must be assembled by knowledgeable paleontologists. Because soft parts are rarely fossilized, scientific illustrators and those who create models of extinct organisms must determine where muscles connected, what skin covering might have been (feathers, scales, hair?), and what color(s) the organism may have been. This last consideration is particularly problematic, and illustrators and modelers have occasionally taken great artistic license with their palettes. The technicolor -- almost psychedelic -- coloration of dinosaurs in the 1970s is an example of such license. The reader, therefore, should recognize that coloring, in particular, is conjectural.

Plant material poses similar problems. The conditions that allow the preservation of tree trunks may not be favorable for the preservation of leaves, and the flowers of flowering plants (which did not arise until well after the Permian) only very rarely survive. Different artists and paleontologists do have quite different conceptions of how organisms looked in life, as amply illustrated by the drawing of Glossopteris here and the drawing in the passage discussing the Glossopteris flora in the Permian World section. (Underlined names are the names of genera -- singular, genus -- the classification level just above the species. Names which are not underlined represent higher biological classification levels than the genus, and are therefore include a greater number and diversity of organisms.)

Marine Organism Description

Fusulinid. Fusulinids are foraminifera (single-celled eukaryotes, that is complex cells) which originated in the Ordovician (see the geological time scale), and flourished in the Carboniferous and Permian. Those at the end of the Permian were the largest that ever lived, some about the size of grains of rice; others even larger (up to several cm/more than an inch). Their skeletons are calcium carbonate. Most lived on the seafloor (that is, they were benthic), though some species probably floated in the open water (that is, they were pelagic). Some presumably contained symbiotic algae, which helped provide essential nutrients. The fusulinids went extinct at the end of the Permian, but many other foraninifera (known as forams) are around today. (Newell, 1978, p. 115, drawing.)

Raphidonema. A sponge. Sponges use flagellae (tiny, hair-like appendages) to pump water through their bodies, capturing food particles along the way. Some sponges have skeletons of fibrous material (these are the ones used as bath sponges), others have glass skeletons (see the Venus flower basket, in the Early Triassic aftermath section), and still others, like Raphidonema, have calcium carbonate skeletons. These are referred to as calcisponges. Raphidonema lived during the Triassic and Cretaceous Periods, and was about 8 cm (just over 3 inches) tall. (Walker and Ward, 1992, p. 34, drawing.)

Rugose coral. Rugose corals are distant relatives of today's corals (scleractinians), and even more distant relatives of jellyfish and sea anemones (they are all classified as cnidarians, pronounced NY-dare-ee-ans). They first appear in the Ordovician; the last of them disappear at the end of the Permian, though most had already gone extinct. This is the calcium carbonate (calcite) skeleton of a solitary rugose coral, which could reach a meter (yard) in length. Some species were colonial; these could be as much as 4 meters (yards) across. With living tissue, they may have resembled sea anemones. (Busbey, 1996, p. 211, drawing.)

Tabulate coral. Tabulate corals were colonial, and like rugose coral colonies, could attain 4 meters (yards) in diameter. They also had calcium carbonate (calcite) skeletons. This drawing shows a tabulate coral from above; each compartment contained a small, sea anemone-like member of the colony. Arose in the Ordovician; extinct at the end of the Permian. (Newell, 1978, p. 115, drawing.)

Scleractinian coral. These are today's corals, having evolved after the end-Permian extinction (in the Triassic). This staghorn coral (Acropora) is just one of many very different kinds of scleractinian corals. Most have a calcium carbonate skeleton (here aragonite rather than calcite). Coral reefs (of which the staghorn is often a prominent member) are only found within about 25° of the equator. Reef-building corals contain symbiotic algae (zooxanthellae, pronounced zose-an-THELL-ee), which help provide nutrition. (Newell, 1978, p. 115, drawing.)

Bryozoan and Brachiopod. The meshlike fossil in the upper left is a byrozoan. Bryozoans are colonial organisms, that is, numerous individuals work together, sweeping the seawater for fine, floating particles of food. The meshlike structure contains chambers for the individual members of the colony; as with fusulinids, this skeleton is composed of calcium carbonate. Though many orders of bryozoans went extinct at the end of the Permian, one made it through, and its descendants thrive today. (The shell is that of a brachiopod, and is discussed below: see Cyrtina.) (Busbey, 1996, p. 213, photo.)

Cyrtina. Brachiopods may look like ordinary sea shells (see Aviculopecten, below), but they are not. Note that the shell, as seen from above, is symmetrical, whereas Aviculopecten's is not. The internal anatomy of brachiopods is also quite different from ordinary sea shells (mollusks), and they are therefore assigned to their own phylum. Cyrtina, which belonged to a group of brachiopods called spirifers (a common fossil in New York state), lived from the Devonian to the Permian. The shell in the photo above is also a spirifer, but not necessarily one of Cyrtina. Cyrtina's shell was about 5 cm (about 1 1/2 inches) across. (Walker and Ward, 1992, p. 88, drawing.)

Archaeocidaris. This sea urchin lived from the Early Carboniferous to the Permian. Sea urchins (echinoids) are echinoderms ("spiny-skins," for the calcite plates which cover their bodies), and, like their fellow echinoderms the sand dollars and starfish (sea stars), display a five-fold (pentameral) symmetry. Sea urchins have long spines for protection, but even longer 'tube feet,' long, thin, but retractable appendages they use for locomotion. They scrape their dinners from off rocks. Archaeocidaris was about 8 cm (3 inches) in diameter. (Walker and Ward, 1992, p. 176, drawing.)

Deltoblastus. The end of the Permian extinction took the last of the blastoids, of which Deltoblastus is one. Like sea urchins, blastoids are echinoderms. They held on to the seafloor with rootlike appendages called holdfasts, and swept the currents with arm-like appendages for food particles, which they transported to their mouths along long grooves. The stalk in this illustration has been cut to indicate that it is longer than the picture size will allow. Cup (top) diameter was about 1.5 cm (3/5 inch). (Walker and Ward, 1992, p. 190, drawing.)

Eocrinus. Though superficially resembling blastoids like Deltoblastus, Eocrinus was a crinoid, a different group altogether, though both blastoids and crinoids are echinoderms. The outstretched arms of crinoids have given the popular name sea lilies. They are a common fossil in the limestones of the American Midwest. Like blastoids, they gathered food particles from the water, and were attached to the seafloor with holdfasts. They were decimated at the end of the Permian, and perhaps only one genus made it through to the Triassic, but its descendants are still around today. Cup diameter was about 2.5 cm (1 inch). (Walker and Ward, 1992, p. 171, drawing.)

Aviculopecten. Pectens (scallops) are extremely common mollusks, of the group known as bivalves. The term 'valve' here refers to a shell; clams too are bivalves. Note that the calcium carbonate shell is not symmetrical, distinguishing it from the brachiopods. Aviculopecten lived from the Carboniferous to the Permian. Diameter was about 2.5 cm (1 inch). (Walker and Ward, 1992, p. 98, drawing.)

Bellerophon. Bellerophon belonged to the group of mollusks (gastropods, that is, "stomach-feet") that we commonly call snails. Gastropods live in seawater, freshwater, and on land. They have shells of calcium carbonate (usually aragonite), and make their livings rasping food off rocks and plants. Bellerophon lived from the Silurian though to the Early Triassic, thus escaping extinction (for a short time) at the end of the Permian. They were typically about 7.5 cm (3 inches) in length. (Walker and Ward, 1992, p. 115, drawing.)

Bifericeras. Though some ammonites grew to about two meters (yards) in diameter, Bifericeras was just a little guy, about 3 cm (1 1/4 inches) in diameter. Ammonites resembled today's squids, but with coiled shells. Indeed, they are squid and octopus relatives, and capture prey in similar fashion: with their long tentacles. Squids, octopi, ammonites, and nautiloids (like today's chambered nautilus) are all cephalopods ("head-feet"), the smartest of the mollusks. The ammonites had several brushes with oblivion: having arisen in the Devonian Period, they barely made it through the extinction event near the Devonian's end but fared well thereafter; only three families made it through the end of the Permian, but again, they thrived through the Mesozoic Era, only to finally succumb to extinction at the end of the Cretaceous.
This specimen is the female; the male was smaller and less ornate. Bifericeras lived during the Early Jurassic. Below the drawing is a photograph of a spectacular pyritized specimen: under the right conditions, fossils may become pyritized, that is, partially replaced by iron pyrite ("fool's gold," FeS¸2), making them look like they have been poured from melted gold. (Walker and Ward, 1992, p. 150, drawing and photo.)

Trilobites. Trilobites, the "bugs" of Paleozoic seas, are arthropods ("jointed feet"), and thus the distant relatives of modern insects, spiders, scorpions, crabs, lobsters, and crayfish. Their external skeletons (called exoskeletons) are made of chitin, a hard protein material similar to that of fingernails. Named for their three "lobes," clearly visible in the segmented sections of these two specimens, they flourished from the Cambrian to the extinction event of the Late Devonian Period, though they managed to survive into the Carboniferous and Permian. The last of the trilobites perished at the end of the Permian. Some trilobites were tiny -- only a millimeter (1/25th of an inch) -- but others reached a full meter (yard) in length. (Busbey, 1996, p. 221, photo.)

Eurypterid. Eurypterids were arthropods, relatives of today's horseshoe crabs. They date from the Ordovician Period, though somewhat similar organisms may be traced back to the Early Cambrian. The end-Permian extinction killed off the eurypterids. The appendages that look like paddles really were paddles: they were used for swimming. And yes, those are eyes. This photograph includes the tail end of one eurypterid as well as a complete specimen. (Busbey, 1996, p. 223, photo.)

Terrestrial Flora Description

Lepidodendron. Lepidodendron was among the first of the tree-like plants. Members of the lycopods ("club mosses"), which emerged in the Silurian Period and has survived to the present day, with notable changes along the way. Toady's lycopods are small plants that appreciate damp conditions; their earliest ancestors were similar. But in the middle of the Paleozoic Era they became dominant members of the first forests, reaching 40 meters (130 feet) in height. Lepidodendron was a cone-bearing Carboniferous lycopod, but others remained important forest constituents until they were replaced by other trees like Archaeopteris. (Walker and Ward, 1992, p. 294, drawing.)

Archaeopteris. Another tree of the first forests, Archaeopteris was a progymnosperm. Conifers are gymnosperms, so progymnosperms were conifer ancestors. Its fern-like fronds originally convinced paleobotanists that it was a fern, until the connection between the fronds and fossil tree stumps measuring up to a meter and a half (5 1/2 feet) in diameter was discovered. Then Archaeopteris, at up to 10 meters (33 feet) tall, was recognized as the fern-tree progenitor of the conifers, and all other seed-bearing plants as well. (Stewart and Rothwell, 1993, p. 266, drawing based on reconstruction by Beck, 1962.)

Dicroidium. In this drawing, Dicroidium looks like a small plant. Actually, it was not so small: about 4 m (13 feet) high. True ferns produce spores, but Dicroidium, a seed fern, produced seeds. It lived during the Triassic, and thus was a descendant of the survivors of the Permian extinction. Its own descendants likely included the cycads. Fern trees and seed ferns are the main constituents of the coal beds dating from the appropriately named Carboniferous. (Walker and Ward, 1992, p. 299, drawing.)

Glossopteris. Like Dicroidium, Glossopteris was a seed fern, but of tree size and shape. With long, tongue or sword-like leaves, it was quite widespread in the forests of Gondwana during the Permian. Despite this success, however, it was wiped out at the end of the Permian, though some related organisms (part of the Glossopteris flora) survived through the Triassic. This Glossopteris purportedly reached about 8 meters (26 feet) in height; other species (that is, members of the same genus) may have been shorter: see the drawing in the discussion of the Glossopteris flora in the Permian world section. But the two pictures of Glossopteris look quite dissimilar, so the differences may be attributable to varying paleontological or artistic interpretations. (Walker and Ward, 1992, p. 297, drawing.)

Conifer. Conifers make cones, hence their name. They are gymnosperms, meaning that they have "naked," relatively unprotected, seeds. Though they evolved prior to the end of the Permian, that extinction event eliminated many gymnosperm competitors. Seizing their new opportunity, conifers thrived in the Mesozoic, and have ever since. Conifers include pines, firs, and spruces, major components of colder region forests. (Walker and Ward, 1992, p. 303, drawing.)

Ginkgo. Ginkgoes are gymnosperms, like conifers and cycads, but instead of having needles or fronds, they have broad leaves. They arose in the Early Permian, and survived the extinction event to thrive in the Triassic Period and especially the Jurassic. Known for the often unpleasant odor of their fruit, Ginkgoes are still around today. Unlike most other trees, which have both male and female organs on the same plant, each tree is either male or female. Ginkgoes are quite tall, and reach as much as 35 meters (115 feet) in height. (Walker and Ward, 1992, p. 307, drawing.)

Terrestrial Fauna Description

Eryops. This large (175 kg/ almost 400 pounds) amphibian lived during the Early Permian Period, and attained a length of 1.5-2 m (5- 6 1/2 feet). Eryops probably lived both on land and in the water. It belonged to a group called the labyrinthodonts, and more specifically to the temnospondyls. (Lambert, 1985, p. 94, drawing.)

Diplocaulus. This Permian Period amphibian (a lepospondyl) was smaller than it may look, being only about 1 m (39 inches) in length. Its unusual wide, flat skull has attracted much conjecture; one suggestion is that it prevented potential predators from easily swallowing the animal. A series of fossils shows that the skull shape of Diplocaulus's ancestors gradually widened with time. (Walker and Ward, 1992, p. 221, drawing.)

Aphaneramma. A fish-eating, early Triassic amphibian. Like today's alligators and crocodiles, and especially gharials (all of which are reptiles, not amphibians), Aphaneramma's elongated snout allowed it to get close to prey before its bulk revealed its presence. It was about 2 m (6 1/2 feet) in length. (Walker and Ward, 1992, p. 222, drawing.)

Batrachosuchus. This amphibian lived in the Triassic; like Diplocaulus, it had an enlarged, flattened skull. It was smaller than Diplocaulus, however, and only reached about half a meter (20 inches) in length. (Walker and Ward, 1992, p. 223, drawing.)

Scaphonyx. Scaphonyx belonged to the rhynchosaurid ("beak-lizard") family of the rhynchocephalians ("beak-heads"). Though they possessed no ordinary teeth, their tusk-like beaks allowed them to gather vegetation which they crushed with strong toothplates in their palates. They lived during the Middle of the Triassic, and reached about 1.8 m (6 feet) in length and about 90 kg (200 pounds) in weight. (Lambert, 1985, p. 115, drawing.)

Edaphosaurus. A "sail-back" reptile. Edaphosaurus was a distant, herbivorous relative of today's mammals. The "sail" was most likely a primitive method of heat regulation. By orienting the sail to catch the morning rays of sunshine, Edaphosaurus could raise its body temperature much more rapidly than could other reptiles, allowing it to move about and feed earlier in the day. Its higher metabolism would also have assisted it in outrunning potential predators. It evolved in the Late Carboniferous Period, and lived into the Early Permian. 3 m (10 feet) in length. (Walker and Ward, 1992, p. 256, drawing.)

Dimetrodon. Because it looks big and nasty -- which it was -- Dimetrodon is often mistaken for a dinosaur. Actually, this "sail-back" reptile (like Edaphosaurus, a pelycosaur) lived -- and died off -- tens of millions of years before the dinosaurs. It lived in the Early Permian, and was a formidable predator, perhaps on Edaphosaurus! At about 3 m (10 feet) in length, Dimetrodon was about the same size as Edaphosaurus, and lived during the Early Permian as well. (Walker and Ward, 1992, p. 255, drawing.)

Moschops. A mammal-like reptile; one of the therapsid group (specifically, a dinocephalian). Mammals, birds, and likely at least some of the dinosaurs are all warmed-blooded creatures. Actually, they are classified as endotherms, which means that they regulate their own internal temperatures, unlike the ectotherms ("cold-blooded" organisms), whose internal temperatures are about the same as their surroundings. Moschops was a big guy (about 2.4 m/ 8 feet long; weight about 700 kg/1500 pounds) with a massive skeleton and sprawling limbs. (Nonetheless, it was a vegetarian.) It lived during the Middle of the Permian. (Lambert, 1985, p. 132, drawing.)

Therapsid. This is a sort of generic therapsid, obviously different from the massive Moschops. (It does, however, resemble Thrinaxodon, or perhaps Pristerognathid, a carnivorous Late Permian therapsid weighing in at about 50 kg/110 pounds.) Some therapsids possessed snout pits, from which long, whisker-like hairs could have protruded (think of your cat!). If so, at least some therapsids may have had body hair, which would have helped keep them warm and possibly allowed them to live in colder conditions. Therapsids included several groups of mammal-like reptiles, including the Dinocephalians (like Moschops), Dicynodonts, and the Cynodonts, from which modern mammals evolved. Note how this therapsid does not possess the sprawling limbs of Moschops, and with limbs upright, was likely more efficient at getting about than its ancestors. Therapsids were, by far, the most successful and numerous of the Late Permian land animals. (Madsen and Troll, 1994. p. 56, drawing by Ray Troll.)

Lystrosaurus. An Early Triassic therapsid. It has been suggested that Lystrosaurus was comparable to today's wild pigs, or perhaps a smaller version of a hippo. Certainly there were plenty of them around, snarfing up lots of vegetation, cropping it with their strong, almost toothless jaws. They may have been semi-aquatic, and fed on aquatic plants. About 2 m (6 1/2 feet) in length. (Norman, 1994, p. 117, drawing.)

Euparkeria. An archosaur (Triassic), about half a meter (1 1/2 feet) in length. Just before the end of the Permian, the dominant land animals were incontestably the therapsids. Other land animals, mostly other lines of reptiles, paled to relative insignificance. The end-Permian extinction reshuffled the existing biota, and allowed some of these other reptiles to usurp the reigning therapsids. Most important, by far, was that group known as the archosaurs. Soon after the extinction, the archosaurs exploded into prominence (the name archosaurs means "ruling lizards"). Indeed, their descendants would rule the world for over a hundred million years, and drive the proto-mammals into smaller sizes and more marginal habitats. These descendants were the dinosaurs. (British Museum, 1985, p. 50, model.)

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Marine Organism	Description
	Fusulinid. Fusulinids are foraminifera (single-celled eukaryotes, that is complex cells) which originated in the Ordovician (see the geological time scale), and flourished in the Carboniferous and Permian. Those at the end of the Permian were the largest that ever lived, some about the size of grains of rice; others even larger (up to several cm/more than an inch). Their skeletons are calcium carbonate. Most lived on the seafloor (that is, they were benthic), though some species probably floated in the open water (that is, they were pelagic). Some presumably contained symbiotic algae, which helped provide essential nutrients. The fusulinids went extinct at the end of the Permian, but many other foraninifera (known as forams) are around today. (Newell, 1978, p. 115, drawing.)
	Raphidonema. A sponge. Sponges use flagellae (tiny, hair-like appendages) to pump water through their bodies, capturing food particles along the way. Some sponges have skeletons of fibrous material (these are the ones used as bath sponges), others have glass skeletons (see the Venus flower basket, in the Early Triassic aftermath section), and still others, like Raphidonema, have calcium carbonate skeletons. These are referred to as calcisponges. Raphidonema lived during the Triassic and Cretaceous Periods, and was about 8 cm (just over 3 inches) tall. (Walker and Ward, 1992, p. 34, drawing.)
	Rugose coral. Rugose corals are distant relatives of today's corals (scleractinians), and even more distant relatives of jellyfish and sea anemones (they are all classified as cnidarians, pronounced NY-dare-ee-ans). They first appear in the Ordovician; the last of them disappear at the end of the Permian, though most had already gone extinct. This is the calcium carbonate (calcite) skeleton of a solitary rugose coral, which could reach a meter (yard) in length. Some species were colonial; these could be as much as 4 meters (yards) across. With living tissue, they may have resembled sea anemones. (Busbey, 1996, p. 211, drawing.)
	Tabulate coral. Tabulate corals were colonial, and like rugose coral colonies, could attain 4 meters (yards) in diameter. They also had calcium carbonate (calcite) skeletons. This drawing shows a tabulate coral from above; each compartment contained a small, sea anemone-like member of the colony. Arose in the Ordovician; extinct at the end of the Permian. (Newell, 1978, p. 115, drawing.)
	Scleractinian coral. These are today's corals, having evolved after the end-Permian extinction (in the Triassic). This staghorn coral (Acropora) is just one of many very different kinds of scleractinian corals. Most have a calcium carbonate skeleton (here aragonite rather than calcite). Coral reefs (of which the staghorn is often a prominent member) are only found within about 25° of the equator. Reef-building corals contain symbiotic algae (zooxanthellae, pronounced zose-an-THELL-ee), which help provide nutrition. (Newell, 1978, p. 115, drawing.)
	Bryozoan and Brachiopod. The meshlike fossil in the upper left is a byrozoan. Bryozoans are colonial organisms, that is, numerous individuals work together, sweeping the seawater for fine, floating particles of food. The meshlike structure contains chambers for the individual members of the colony; as with fusulinids, this skeleton is composed of calcium carbonate. Though many orders of bryozoans went extinct at the end of the Permian, one made it through, and its descendants thrive today. (The shell is that of a brachiopod, and is discussed below: see Cyrtina.) (Busbey, 1996, p. 213, photo.)
	Cyrtina. Brachiopods may look like ordinary sea shells (see Aviculopecten, below), but they are not. Note that the shell, as seen from above, is symmetrical, whereas Aviculopecten's is not. The internal anatomy of brachiopods is also quite different from ordinary sea shells (mollusks), and they are therefore assigned to their own phylum. Cyrtina, which belonged to a group of brachiopods called spirifers (a common fossil in New York state), lived from the Devonian to the Permian. The shell in the photo above is also a spirifer, but not necessarily one of Cyrtina. Cyrtina's shell was about 5 cm (about 1 1/2 inches) across. (Walker and Ward, 1992, p. 88, drawing.)
	Archaeocidaris. This sea urchin lived from the Early Carboniferous to the Permian. Sea urchins (echinoids) are echinoderms ("spiny-skins," for the calcite plates which cover their bodies), and, like their fellow echinoderms the sand dollars and starfish (sea stars), display a five-fold (pentameral) symmetry. Sea urchins have long spines for protection, but even longer 'tube feet,' long, thin, but retractable appendages they use for locomotion. They scrape their dinners from off rocks. Archaeocidaris was about 8 cm (3 inches) in diameter. (Walker and Ward, 1992, p. 176, drawing.)
	Deltoblastus. The end of the Permian extinction took the last of the blastoids, of which Deltoblastus is one. Like sea urchins, blastoids are echinoderms. They held on to the seafloor with rootlike appendages called holdfasts, and swept the currents with arm-like appendages for food particles, which they transported to their mouths along long grooves. The stalk in this illustration has been cut to indicate that it is longer than the picture size will allow. Cup (top) diameter was about 1.5 cm (3/5 inch). (Walker and Ward, 1992, p. 190, drawing.)
	Eocrinus. Though superficially resembling blastoids like Deltoblastus, Eocrinus was a crinoid, a different group altogether, though both blastoids and crinoids are echinoderms. The outstretched arms of crinoids have given the popular name sea lilies. They are a common fossil in the limestones of the American Midwest. Like blastoids, they gathered food particles from the water, and were attached to the seafloor with holdfasts. They were decimated at the end of the Permian, and perhaps only one genus made it through to the Triassic, but its descendants are still around today. Cup diameter was about 2.5 cm (1 inch). (Walker and Ward, 1992, p. 171, drawing.)
	Aviculopecten. Pectens (scallops) are extremely common mollusks, of the group known as bivalves. The term 'valve' here refers to a shell; clams too are bivalves. Note that the calcium carbonate shell is not symmetrical, distinguishing it from the brachiopods. Aviculopecten lived from the Carboniferous to the Permian. Diameter was about 2.5 cm (1 inch). (Walker and Ward, 1992, p. 98, drawing.)
	Bellerophon. Bellerophon belonged to the group of mollusks (gastropods, that is, "stomach-feet") that we commonly call snails. Gastropods live in seawater, freshwater, and on land. They have shells of calcium carbonate (usually aragonite), and make their livings rasping food off rocks and plants. Bellerophon lived from the Silurian though to the Early Triassic, thus escaping extinction (for a short time) at the end of the Permian. They were typically about 7.5 cm (3 inches) in length. (Walker and Ward, 1992, p. 115, drawing.)
	Bifericeras. Though some ammonites grew to about two meters (yards) in diameter, Bifericeras was just a little guy, about 3 cm (1 1/4 inches) in diameter. Ammonites resembled today's squids, but with coiled shells. Indeed, they are squid and octopus relatives, and capture prey in similar fashion: with their long tentacles. Squids, octopi, ammonites, and nautiloids (like today's chambered nautilus) are all cephalopods ("head-feet"), the smartest of the mollusks. The ammonites had several brushes with oblivion: having arisen in the Devonian Period, they barely made it through the extinction event near the Devonian's end but fared well thereafter; only three families made it through the end of the Permian, but again, they thrived through the Mesozoic Era, only to finally succumb to extinction at the end of the Cretaceous. This specimen is the female; the male was smaller and less ornate. Bifericeras lived during the Early Jurassic. Below the drawing is a photograph of a spectacular pyritized specimen: under the right conditions, fossils may become pyritized, that is, partially replaced by iron pyrite ("fool's gold," FeS¸2), making them look like they have been poured from melted gold. (Walker and Ward, 1992, p. 150, drawing and photo.)
	Trilobites. Trilobites, the "bugs" of Paleozoic seas, are arthropods ("jointed feet"), and thus the distant relatives of modern insects, spiders, scorpions, crabs, lobsters, and crayfish. Their external skeletons (called exoskeletons) are made of chitin, a hard protein material similar to that of fingernails. Named for their three "lobes," clearly visible in the segmented sections of these two specimens, they flourished from the Cambrian to the extinction event of the Late Devonian Period, though they managed to survive into the Carboniferous and Permian. The last of the trilobites perished at the end of the Permian. Some trilobites were tiny -- only a millimeter (1/25th of an inch) -- but others reached a full meter (yard) in length. (Busbey, 1996, p. 221, photo.)
	Eurypterid. Eurypterids were arthropods, relatives of today's horseshoe crabs. They date from the Ordovician Period, though somewhat similar organisms may be traced back to the Early Cambrian. The end-Permian extinction killed off the eurypterids. The appendages that look like paddles really were paddles: they were used for swimming. And yes, those are eyes. This photograph includes the tail end of one eurypterid as well as a complete specimen. (Busbey, 1996, p. 223, photo.)
Terrestrial Flora	Description
	Lepidodendron. Lepidodendron was among the first of the tree-like plants. Members of the lycopods ("club mosses"), which emerged in the Silurian Period and has survived to the present day, with notable changes along the way. Toady's lycopods are small plants that appreciate damp conditions; their earliest ancestors were similar. But in the middle of the Paleozoic Era they became dominant members of the first forests, reaching 40 meters (130 feet) in height. Lepidodendron was a cone-bearing Carboniferous lycopod, but others remained important forest constituents until they were replaced by other trees like Archaeopteris. (Walker and Ward, 1992, p. 294, drawing.)
	Archaeopteris. Another tree of the first forests, Archaeopteris was a progymnosperm. Conifers are gymnosperms, so progymnosperms were conifer ancestors. Its fern-like fronds originally convinced paleobotanists that it was a fern, until the connection between the fronds and fossil tree stumps measuring up to a meter and a half (5 1/2 feet) in diameter was discovered. Then Archaeopteris, at up to 10 meters (33 feet) tall, was recognized as the fern-tree progenitor of the conifers, and all other seed-bearing plants as well. (Stewart and Rothwell, 1993, p. 266, drawing based on reconstruction by Beck, 1962.)
	Dicroidium. In this drawing, Dicroidium looks like a small plant. Actually, it was not so small: about 4 m (13 feet) high. True ferns produce spores, but Dicroidium, a seed fern, produced seeds. It lived during the Triassic, and thus was a descendant of the survivors of the Permian extinction. Its own descendants likely included the cycads. Fern trees and seed ferns are the main constituents of the coal beds dating from the appropriately named Carboniferous. (Walker and Ward, 1992, p. 299, drawing.)
	Glossopteris. Like Dicroidium, Glossopteris was a seed fern, but of tree size and shape. With long, tongue or sword-like leaves, it was quite widespread in the forests of Gondwana during the Permian. Despite this success, however, it was wiped out at the end of the Permian, though some related organisms (part of the Glossopteris flora) survived through the Triassic. This Glossopteris purportedly reached about 8 meters (26 feet) in height; other species (that is, members of the same genus) may have been shorter: see the drawing in the discussion of the Glossopteris flora in the Permian world section. But the two pictures of Glossopteris look quite dissimilar, so the differences may be attributable to varying paleontological or artistic interpretations. (Walker and Ward, 1992, p. 297, drawing.)
	Conifer. Conifers make cones, hence their name. They are gymnosperms, meaning that they have "naked," relatively unprotected, seeds. Though they evolved prior to the end of the Permian, that extinction event eliminated many gymnosperm competitors. Seizing their new opportunity, conifers thrived in the Mesozoic, and have ever since. Conifers include pines, firs, and spruces, major components of colder region forests. (Walker and Ward, 1992, p. 303, drawing.)
	Ginkgo. Ginkgoes are gymnosperms, like conifers and cycads, but instead of having needles or fronds, they have broad leaves. They arose in the Early Permian, and survived the extinction event to thrive in the Triassic Period and especially the Jurassic. Known for the often unpleasant odor of their fruit, Ginkgoes are still around today. Unlike most other trees, which have both male and female organs on the same plant, each tree is either male or female. Ginkgoes are quite tall, and reach as much as 35 meters (115 feet) in height. (Walker and Ward, 1992, p. 307, drawing.)
Terrestrial Fauna	Description
	Eryops. This large (175 kg/ almost 400 pounds) amphibian lived during the Early Permian Period, and attained a length of 1.5-2 m (5- 6 1/2 feet). Eryops probably lived both on land and in the water. It belonged to a group called the labyrinthodonts, and more specifically to the temnospondyls. (Lambert, 1985, p. 94, drawing.)
	Diplocaulus. This Permian Period amphibian (a lepospondyl) was smaller than it may look, being only about 1 m (39 inches) in length. Its unusual wide, flat skull has attracted much conjecture; one suggestion is that it prevented potential predators from easily swallowing the animal. A series of fossils shows that the skull shape of Diplocaulus's ancestors gradually widened with time. (Walker and Ward, 1992, p. 221, drawing.)
	Aphaneramma. A fish-eating, early Triassic amphibian. Like today's alligators and crocodiles, and especially gharials (all of which are reptiles, not amphibians), Aphaneramma's elongated snout allowed it to get close to prey before its bulk revealed its presence. It was about 2 m (6 1/2 feet) in length. (Walker and Ward, 1992, p. 222, drawing.)
	Batrachosuchus. This amphibian lived in the Triassic; like Diplocaulus, it had an enlarged, flattened skull. It was smaller than Diplocaulus, however, and only reached about half a meter (20 inches) in length. (Walker and Ward, 1992, p. 223, drawing.)
	Scaphonyx. Scaphonyx belonged to the rhynchosaurid ("beak-lizard") family of the rhynchocephalians ("beak-heads"). Though they possessed no ordinary teeth, their tusk-like beaks allowed them to gather vegetation which they crushed with strong toothplates in their palates. They lived during the Middle of the Triassic, and reached about 1.8 m (6 feet) in length and about 90 kg (200 pounds) in weight. (Lambert, 1985, p. 115, drawing.)
	Edaphosaurus. A "sail-back" reptile. Edaphosaurus was a distant, herbivorous relative of today's mammals. The "sail" was most likely a primitive method of heat regulation. By orienting the sail to catch the morning rays of sunshine, Edaphosaurus could raise its body temperature much more rapidly than could other reptiles, allowing it to move about and feed earlier in the day. Its higher metabolism would also have assisted it in outrunning potential predators. It evolved in the Late Carboniferous Period, and lived into the Early Permian. 3 m (10 feet) in length. (Walker and Ward, 1992, p. 256, drawing.)
	Dimetrodon. Because it looks big and nasty -- which it was -- Dimetrodon is often mistaken for a dinosaur. Actually, this "sail-back" reptile (like Edaphosaurus, a pelycosaur) lived -- and died off -- tens of millions of years before the dinosaurs. It lived in the Early Permian, and was a formidable predator, perhaps on Edaphosaurus! At about 3 m (10 feet) in length, Dimetrodon was about the same size as Edaphosaurus, and lived during the Early Permian as well. (Walker and Ward, 1992, p. 255, drawing.)
	Moschops. A mammal-like reptile; one of the therapsid group (specifically, a dinocephalian). Mammals, birds, and likely at least some of the dinosaurs are all warmed-blooded creatures. Actually, they are classified as endotherms, which means that they regulate their own internal temperatures, unlike the ectotherms ("cold-blooded" organisms), whose internal temperatures are about the same as their surroundings. Moschops was a big guy (about 2.4 m/ 8 feet long; weight about 700 kg/1500 pounds) with a massive skeleton and sprawling limbs. (Nonetheless, it was a vegetarian.) It lived during the Middle of the Permian. (Lambert, 1985, p. 132, drawing.)
	Therapsid. This is a sort of generic therapsid, obviously different from the massive Moschops. (It does, however, resemble Thrinaxodon, or perhaps Pristerognathid, a carnivorous Late Permian therapsid weighing in at about 50 kg/110 pounds.) Some therapsids possessed snout pits, from which long, whisker-like hairs could have protruded (think of your cat!). If so, at least some therapsids may have had body hair, which would have helped keep them warm and possibly allowed them to live in colder conditions. Therapsids included several groups of mammal-like reptiles, including the Dinocephalians (like Moschops), Dicynodonts, and the Cynodonts, from which modern mammals evolved. Note how this therapsid does not possess the sprawling limbs of Moschops, and with limbs upright, was likely more efficient at getting about than its ancestors. Therapsids were, by far, the most successful and numerous of the Late Permian land animals. (Madsen and Troll, 1994. p. 56, drawing by Ray Troll.)
	Lystrosaurus. An Early Triassic therapsid. It has been suggested that Lystrosaurus was comparable to today's wild pigs, or perhaps a smaller version of a hippo. Certainly there were plenty of them around, snarfing up lots of vegetation, cropping it with their strong, almost toothless jaws. They may have been semi-aquatic, and fed on aquatic plants. About 2 m (6 1/2 feet) in length. (Norman, 1994, p. 117, drawing.)
	Euparkeria. An archosaur (Triassic), about half a meter (1 1/2 feet) in length. Just before the end of the Permian, the dominant land animals were incontestably the therapsids. Other land animals, mostly other lines of reptiles, paled to relative insignificance. The end-Permian extinction reshuffled the existing biota, and allowed some of these other reptiles to usurp the reigning therapsids. Most important, by far, was that group known as the archosaurs. Soon after the extinction, the archosaurs exploded into prominence (the name archosaurs means "ruling lizards"). Indeed, their descendants would rule the world for over a hundred million years, and drive the proto-mammals into smaller sizes and more marginal habitats. These descendants were the dinosaurs. (British Museum, 1985, p. 50, model.)