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174-664: Gorgonopsia (from the Greek Gorgon , a mythological beast, and óps 'aspect') is an extinct clade of sabre-toothed therapsids from the Middle to the Upper Permian , roughly between 265 and 252 million years ago. They are characterised by a long and narrow skull, as well as elongated upper and sometimes lower canine teeth and incisors which were likely used as slashing and stabbing weapons. Postcanine teeth are generally reduced or absent. For hunting large prey, they possibly used

348-423: A parietal eye (which detects sunlight and maintains circadian rhythm ), a keen sense of smell, a functional vomeronasal organ ("Jacobson's organ"), and possibly a rudimentary eardrum . The major therapsid groups had all evolved by 275 million years ago from a " pelycosaur " ancestor (a poorly defined group including all synapsids which are not therapsids). The therapsid takeover from pelycosaurs took place by

522-456: A bite-and-retreat tactic, ambushing and taking a debilitating bite out of the target, and following it at a safe distance before its injuries exhausted it, whereupon the gorgonopsian would grapple the animal and deliver a killing bite. They would have had an exorbitant gape, possibly in excess of 90°, without having to unhinge the jaw. They markedly increased in size as time went on, growing from small skull lengths of 10–15 cm (4–6 in) in

696-607: A brief period of domination in the early Spathian, probably related to a transient oxygenation of deep waters. Neospathodid conodonts survived the crisis but underwent proteromorphosis. In the PTME's aftermath, disaster taxa of benthic foraminifera filled many of their vacant niches. The recovery of benthic foraminifera was very slow and frequently interrupted until the Spathian. In the Tethys, foraminiferal communities remained low in diversity into

870-613: A ceiling limiting the maximum ecological complexity of marine ecosystems until the Spathian. Recovery biotas appear to have been ecologically uneven and unstable into the Anisian , making them vulnerable to environmental stresses. Whereas most marine communities were fully recovered by the Middle Triassic, global marine diversity reached pre-extinction values no earlier than the Middle Jurassic, approximately 75 million years after

1044-550: A comprehensive monograph on Gorgonopsia (defining it as an infraorder ), and recognised only two families: Watongiidae and Gorgonopidae. Watongia was moved to Varanopidae in 2004 by the Canadian paleontologists Robert R. Reisz and Michel Laurin . Sigogneau-Russell split Gorgonopidae into three subfamilies—Gorgonopsinae, Rubidgeinae, and Inostranceviinae—and reduced the number of genera to twenty-three. In 2002, Russian palaeontologist Mikhail Feodosievich Ivakhnenko , considering

1218-751: A curse. Permian%E2%80%93Triassic extinction event Approximately 251.9 million years ago, the Permian–Triassic ( P–T , P–Tr ) extinction event ( PTME ; also known as the Late Permian extinction event , the Latest Permian extinction event , the End-Permian extinction event , and colloquially as the Great Dying ) forms the boundary between the Permian and Triassic geologic periods , and with them

1392-455: A device (an apotropaion ) to ward away unwanted things, and which was in origin a dancer-worn mask. The classic formulation of this view is that of Jane Ellen Harrison , the gorgoneion as a "ritual mask misunderstood": ... in her essence Medusa is a head and nothing more; her potency only begins when her head is severed, and that potency resides in the head; she is in a word a mask with a body later appended. The primitive Greek knew that there

1566-513: A family of large-size fusuline foraminifera . The impact of the end-Guadalupian extinction on marine organisms appears to have varied between locations and between taxonomic groups – brachiopods and corals had severe losses. Marine invertebrates suffered the greatest losses during the P–Tr extinction. Evidence of this was found in samples from south China sections at the P–Tr boundary. Here, 286 out of 329 marine invertebrate genera disappear within

1740-601: A full-bodied Gorgon) depicted in relief being displayed at the Temple of Zeus at Olympia . There has been considerable and wide-ranging speculation concerning the possible origins of the story of Perseus and the Gorgons, as well as gorgoneia, the representations of Gorgon faces. The origins of the Perseus-Gorgon story, and gorgoneia, even with respect to each other, are uncertain. The Perseus-Gorgon story might have come first inspiring

1914-568: A great reduction in their geographic range. Following this transition, coal swamps vanished. The North Chinese floral extinction correlates with the decline of the Gigantopteris flora of South China. In South China, the subtropical Cathaysian gigantopterid dominated rainforests abruptly collapsed. The floral extinction in South China is associated with bacterial blooms in soil and nearby lacustrine ecosystems, with soil erosion resulting from

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2088-615: A group of wearable helmet masks from Tiryns , and another group of non-wearable votive masks from the Sanctuary of Orthia at Sparta , which share some features with the typical earliest representations of Gorgon faces. If such masks were in fact intended to represent the face of a Gorgon, then they would show that Gorgons or gorgoneia played a role in some kind of ritualistic or dramatic practice or performance. The gorgonesque votive masks from Sparta have deep S-shaped furrows on either side of wide-mouthed grimaces. Such features resemble those on

2262-420: A high background extinction rate (by implication, taxa with a high turnover ). The extinction rate of marine organisms was catastrophic. Bioturbators were extremely severely affected, as evidenced by the loss of the sedimentary mixed layer in many marine facies during the end-Permian extinction. Surviving marine invertebrate groups included articulate brachiopods (those with a hinge), which had undergone

2436-474: A lake-dominated Triassic world rather than an earliest Triassic zone of death and decay in some terrestrial fossil beds. Newer chemical evidence agrees better with a fungal origin for Reduviasporonites , diluting these critiques. Uncertainty exists regarding the duration of the overall extinction and about the timing and duration of various groups' extinctions within the greater process. Some evidence suggests that there were multiple extinction pulses or that

2610-419: A long time. On the other hand, because the functional canine is typically found in the foremost tooth socket (instead of equal occurrence in either socket), it is possible that canine replacement occurred a finite number of times, and the animal would eventually be left with a single, permanent set of functional canines in these sockets. In 1984, British palaeontologists Doris and Kenneth Kermack suggested that

2784-561: A massive rearrangement of ecosystems does occur, with plant abundances and distributions changing profoundly and all the forests virtually disappearing. The dominant floral groups changed, with many groups of land plants entering abrupt decline, such as Cordaites ( gymnosperms ) and Glossopteris ( seed ferns ). The severity of plant extinction has been disputed. The Glossopteris -dominated flora that characterised high-latitude Gondwana collapsed in Australia around 370,000 years before

2958-724: A mythological lake set somewhere in westernmost North Africa. And the fifth-century BC poet Pindar has Perseus, apparently on his quest for the Gorgon head, visit the Hyperboreans (usually considered to dwell in the far north). However, whether Pindar means to imply that the Gorgons lived near the Hyperboreans is unclear. Pherecydes notes that Medusa's face turned men to stone, and Pindar describes Medusa's severed head as "stony death". In Prometheus Bound , it says that no mortal can look at them and live. According to Apollodorus, all three of

3132-407: A predator. Unlike either reptiles or mammals , the semi-circular canals are flat, probably because they were wedged between the opisthotic (an inner ear bone) and supraoccipital bones. Like many mammals, gorgonopsians were heterodonts , with clearly defined incisors , canines , and postcanine teeth homologous with premolars and molars . They had five incisors in the upper jaw (for most,

3306-668: A random assemblage of which only two have even a remote similarity to Gorgonopsia. In 2011, an incomplete set of teeth were discovered in a locality within the Turpan Depression , Xinjiang , in the northwest of the country. The fossil material, although thin, is described in 2022 by paleontologists Jun Liu and Wan Yiang and confirms that it comes from a gorgonopsian dating from the Upper Permian that actually lived in present-day China. In 2003, Indian palaeontologists Sanghamitra Ray and Saswati Bandyopadhyay assigned some skull fragments from

3480-473: A rather high body temperature, it is unclear if they would have also had sweat glands or fur (and by extension whiskers and related structures). Their brains were reminiscent of modern reptilian brains, rather than those of living mammals . Most species may have been predominantly diurnal (active during the day) though some could have been crepuscular (active at dawn or dusk) or nocturnal (active at night). They are thought to have had binocular vision ,

3654-451: A reference to Athena's aegis . In the Iliad , the aegis is a device, usually associated with Athena , which was decorated with a Gorgon head. Athena wore it in battle as a shield which neither Apollo 's spear, or even Zeus ' thunderbolt could pierce. According to the Iliad , Hephaestus made the aegis for Zeus, while according to a Hesiod fragment, Metis made it for Athena, before Athena

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3828-553: A severe bottleneck in diversity. Evidence from South China indicates the foraminiferal extinction had two pulses. Foraminiferal biodiversity hotspots shifted into deeper waters during the PTME. Approximately 93% of latest Permian foraminifera became extinct, with 50% of the clade Textulariina, 92% of Lagenida, 96% of Fusulinida, and 100% of Miliolida disappearing. Foraminifera that were calcaerous suffered an extinction rate of 91%. The reason why lagenides survived while fusulinoidean fusulinides went completely extinct may have been due to

4002-475: A slow decline in numbers since the P–Tr extinction; the Ceratitida order of ammonites ; and crinoids ("sea lilies"), which very nearly became extinct but later became abundant and diverse. The groups with the highest survival rates generally had active control of circulation , elaborate gas exchange mechanisms, and light calcification; more heavily calcified organisms with simpler breathing apparatuses suffered

4176-406: A specific region were more likely to go extinct than cosmopolitan taxa. There was little latitudinal difference in the survival rates of taxa. Organisms that inhabited refugia less affected by global warming experienced lesser or delayed extinctions. Among benthic organisms the extinction event multiplied background extinction rates , and therefore caused maximum species loss to taxa that had

4350-415: A striking resemblance to a seal impression from Nuzi c. 1450 BC. This suggests the possibility that Greeks misinterpreted or reinterpreted these Mesopotamian images, giving rise, through a process that Burkert has described as a "creative misunderstanding", to the myth of the Gorgon's petrifying gaze. The consensus among classical scholars seems to be that the function of a gorgoneion was apotropaic , as

4524-579: A study of the Shangsi section showed two extinction pulses with different causes too. Recent research shows that different groups became extinct at different times; for example, while difficult to date absolutely, ostracod and brachiopod extinctions were separated by around 670,000 to 1.17 million years. Palaeoenvironmental analysis of Lopingian strata in the Bowen Basin of Queensland indicates numerous intermittent periods of marine environmental stress from

4698-496: Is another point of controversy. Evidence from a well-preserved sequence in east Greenland suggests that the terrestrial and marine extinctions began simultaneously. In this sequence, the decline of animal life is concentrated in a period approximately 10,000 to 60,000 years long, with plants taking an additional several hundred thousand years to show the full impact of the event. Many sedimentary sequences from South China show synchronous terrestrial and marine extinctions. Research in

4872-620: Is associated with the Ancient Greek adjective gorgós ( γοργός ), which, of an eye or look, means 'grim, fierce, awesome, dazzling', and is thought to derive from the Sanskrit stem garğ . The stem has connotations of noise, and Germanic and Romance languages have many derivatives from this stem referring to the throat (e.g. 'gorge') or the guttural sounds produced in the throat (e.g. 'gargle', 'gurgle'). It has been understood as meaning to growl, roar or howl, while Thalia Feldman suggests that

5046-585: Is likely attributable to their ability to thrive in a wide range of environmental conditions. Conodonts saw a rapid recovery during the Induan, with anchignathodontids experiencing a diversity peak in the earliest Induan. Gondolellids diversified at the end of the Griesbachian; this diversity spike was most responsible for the overall conodont diversity peak in the Smithian. Segminiplanate conodonts again experienced

5220-451: Is likely that post-extinction microbial mats played a vital, indispensable role in the survival and recovery of various bioturbating organisms. The microbialite refuge hypothesis has been criticised as reflecting a taphonomic bias due to the greater preservation potential of microbialite deposits, however, rather than a genuine phenomenon. Ichnocoenoses show that marine ecosystems recovered to pre-extinction levels of ecological complexity by

5394-514: Is little consensus on which genera can be assigned to which subfamilies. In 2015, American palaeontologist Christian F. Kammerer and colleagues redescribed Eriphostoma (which was labelled as an indeterminate theriodont) as a gorgonopsian, and sunk Scylacognathus and the next year Eoarctops into it. The first phylogeny (family tree) of the members of Gorgonopsia was published in 2016 by American palaeontologist Christian F. Kammerer, who specifically investigated Rubidgeinae, and re-described both

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5568-529: Is possible that some taxa are synonymous with each other, and represent different stages of development. Among the first attempts to organise the clade was carried out by British zoologist David Meredith Seares Watson and American palaeontologist Alfred Romer in 1956, who split it into twenty families, of which the members of three (Burnetiidae, Hipposauridae, and Phthinosuchidae) are not considered gorgonopsians anymore. In 1970 and again in 1989, predominantly considering African taxa, Sigogneau-Russell published

5742-501: Is possible that the mythology and/or the iconography of Gorgons were subject to Near-Eastern influence. In particular elements of full-bodied Gorgon iconography seem to have been borrowed from that of the Mesopotamian Lamashtu . Mesopotamian depictions of Gilgamesh slaying Humbaba , may have influenced the Perseus-Gorgon story, while gorgoneia may be connected to images of Humbaba. The Gorgon as Mistress of Animals , in

5916-409: Is related to the vestibulo–ocular reflex (which stabilises gaze while moving the head). Judging by the orientation of the semi-circular canals in the ear (which have to be oriented parallel to the ground), the head of the gorgonopsian specimen GPIT/RE/7124 would have tilted forward by about 41°, increasing the overlap between the visual fields of the two eyes and improving binocular vision —useful to

6090-448: Is short but longer and slenderer than the humerus . For most, the tibia and fibula strongly curve into each other, and the tibia is more robust than the fibula. The joint between the ankle and the heel bones may have been somewhat mobile. The fifth digit for both the hands and feet was not attached to the carpus / tarsus , and instead connected directly to the ulna /heel bone. In 1876, the first gorgonopsian remains were identified in

6264-506: Is that the main cause of the extinction was the flood basalt volcanic eruptions that created the Siberian Traps , which released sulfur dioxide and carbon dioxide , resulting in euxinia (oxygen-starved, sulfurous oceans), elevating global temperatures, and acidifying the oceans . The level of atmospheric carbon dioxide rose from around 400 ppm to 2,500 ppm with approximately 3,900 to 12,000 gigatonnes of carbon being added to

6438-663: The Lexicon Iconographicum Mythologiae Classicae ( LIMC ). In addition to the many examples found on vase paintings, Gorgons occur in a wide variety of other contexts, including architectural ornamentation, shield devices, and coins. Some representations show full-bodied Gorgons, while others, called gorgoneia , show only the face (or head) of a Gorgon, such as those described in the Iliad as appearing on Athena 's aegis , and Agamemnon 's shield. The earliest representations of both types are found from roughly

6612-574: The Araguainha crater and caused seismic release of methane and the destruction of the ozone layer with increased exposure to solar radiation. Previously, it was thought that rock sequences spanning the Permian–Triassic boundary were too few and contained too many gaps for scientists to reliably determine its details. However, it is now possible to date the extinction with millennial precision. U–Pb zircon dates from five volcanic ash beds from

6786-818: The Beaufort Group of the Karoo Supergroup of South Africa, by the biologist and paleontologist Richard Owen . He classified the fossils as Gorgonops torvus , combining the Greek Gorgon , a mythological beast, with the word óps ( ὄψ ), meaning 'aspect'. In Africa, gorgonopsians have also been found in Karoo outcroppings in the Ruhuhu Valley of Tanzania, the Upper Luangwa Valley of Zambia , and Chiweta , Malawi . Gorgonopsians were first identified in Russia in

6960-469: The Global Stratotype Section and Point for the Permian–Triassic boundary at Meishan , China , establish a high-resolution age model for the extinction – allowing exploration of the links between global environmental perturbation, carbon cycle disruption, mass extinction, and recovery at millennial timescales. The first appearance of the conodont Hindeodus parvus has been used to delineate

7134-518: The Iliad , the Gorgon's "glaring" eyes were a notably fearsome feature. As Hector pursues the fleeing Achaeans, "exulting in his might" ... ever slaying the hindmost", Homer describes the Trojan hero as having eyes like "the eyes of the Gorgon". And in the Odyssey , Odysseus , although determined "steadfastly" to stay in the underworld , so as to meet other great men among the dead, is seized by such fear at

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7308-508: The Industrial Revolution was 280 ppm , and the amount today is about 422 ppm ). There is also evidence of increased ultraviolet radiation reaching the earth, causing the mutation of plant spores. It has been suggested that the Permian–Triassic boundary is associated with a sharp increase in the abundance of marine and terrestrial fungi , caused by the sharp increase in the amount of dead plants and animals fed upon by

7482-579: The Middle Triassic ) due to the severity of the extinction. However, studies in Bear Lake County , near Paris, Idaho , and nearby sites in Idaho and Nevada showed a relatively quick rebound in a localized Early Triassic marine ecosystem ( Paris biota ), taking around 1.3 million years to recover, while an unusually diverse and complex ichnobiota is known from Italy less than a million years after

7656-683: The Moradi Formation of Niger, western Russia, and in the Turpan Basin of Xinjiang , China , with probable remains known from the Kundaram Formation in the Pranhita–Godavari Basin of India . These places were semi-arid areas with highly seasonal rainfall. Gorgonopsian genera are all very similar in appearance, and consequently many species have been named based on flimsy and likely age-related differences since their discovery in

7830-590: The Paleozoic and Mesozoic eras. It is Earth 's most severe known extinction event , with the extinction of 57% of biological families , 83% of genera, 81% of marine species and 70% of terrestrial vertebrate species. It is also the greatest known mass extinction of insects . It is the greatest of the "Big Five" mass extinctions of the Phanerozoic . There is evidence for one to three distinct pulses, or phases, of extinction. The scientific consensus

8004-505: The Roadian (middle Permian), suffered a selective extinction pulse 10 million years before the main event, at the end of the Capitanian stage. In this preliminary extinction, which greatly reduced disparity , or the range of different ecological guilds, environmental factors were apparently responsible. Diversity and disparity fell further until the P–Tr boundary; the extinction here (P–Tr)

8178-550: The Temple of Apollo at Delphi (latter part of the sixth century BC). In Euripides 's Ion (c. 412–412 BC), the Chorus describes seeing, on the temple's stone walls, Athena "brandishing her gorgon shield" against Enceladus. Pausanias describes seeing a votive golden shield dedicated by the Spartans and their allies after the Battle of Tanagra (457 BC), with a gorgoneion (or possibly

8352-864: The Wordian . The oldest gorgonopsian specimen is a partial snout belonging to an undeterminable genus from the Eodicynodon Assemblage Zone of the Karoo Basin, roughly dating to the Wordian. Phorcys known from the lowermost end of Karoo's Tapinocephalus Assemblage Zone , roughly dating a little later to the Wordian/Capitanian boundary, is the oldest identifiable gorgonopsian taxon. Sphenacodontidae Biarmosuchia Dinocephalia Anomodontia Gorgonopsia Therocephalia Gorgon Gorgons were dread monsters with terrifying eyes. A Gorgon head

8526-406: The ocean acidification that resulted from increased atmospheric CO 2 . Organisms that relied on haemocyanin or haemoglobin for transporting oxygen were more resistant to extinction than those utilising haemerythrin or oxygen diffusion. There is also evidence that endemism was a strong risk factor influencing a taxon's likelihood of extinction. Bivalve taxa that were endemic and localised to

8700-580: The ozone layer . However, some smaller taxa like Cyonosaurus may have survived up to the Early Triassic . The large predatory niches would be taken over by the archosaurs (namely crocodilians and dinosaurs ) in the Mesozoic . Earlier gorgonopsids in the Middle Permian were quite small, with skull lengths of 10–15 cm (4–6 in), whereas some later genera attained massive, bear-like sizes with

8874-994: The tribe Rubidgeini pending further examination. In 2018, Kammerer and Russian palaeontologist Vladimir Masyutin identified a new genus Nochnitsa as the basalmost known gorgonopsians, and found that all Russian taxa (except Viatkogorgon , which is in the outclade) form a completely separate clade from the African taxa. Also in 2018, palaeobiologist Eva-Maria Bendel, Kammerer, and colleagues resurrected Cynariops . In 2022, Kammerer and fellow palaeontologist Bruce S. Rubidge described Phorcys from South Africa. Nochnitsa Viatkogorgon Suchogorgon Sauroctonus Pravoslavlevia Inostrancevia Phorcys Eriphostoma Gorgonops Cynariops Lycaenops Smilesaurus Arctops Arctognathus Aelurognathus Ruhuhucerberus Sycosaurus Leontosaurus Dinogorgon Rubidgea Clelandina Synapsida has traditionally been split into

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9048-605: The 1890s at the Sokolki locality on the Northern Dvina in Siberia under the supervision of Russian palaeontologist Vladimir Prokhorovich Amalitskii . In a posthumous publication, it was described as Inostrancevia alexandri , and it is one of the best known and largest gorgonopsians. Since then, only a few more Russian taxa have been described: Pravoslavlevia , Sauroctonus , Viatkogorgon , Suchogorgon , and Nochnitsa . One of

9222-420: The 3 ridges. They typically feature a long and narrow skull. Juvenile Rubidgea appear to have had snouts wider than long. Unlike eutheriodonts, the occipital bone (at the back of the skull) is rectangular (wider than tall) and concave, as opposed to triangular. The gorgonopsian brain, like other non- mammaliaform therapsids , lacks an expansion of the neocortex , has a relatively large hindbrain compared to

9396-597: The Anisian. Metazoan reefs became common again during the Anisian because the oceans cooled down then from their overheated state during the Early Triassic. Biodiversity amongst metazoan reefs did not recover until well into the Anisian, millions of years after non-reef ecosystems recovered their diversity. Microbially induced sedimentary structures (MISS) from the earliest Triassic have been found to be associated with abundant opportunistic bivalves and vertical burrows, and it

9570-707: The Early Triassic; and they dominated many surviving communities across the recovery from the mass extinction. Microbialite deposits appear to have declined in the early Griesbachian synchronously with a significant sea level drop that occurred then. Metazoan-built reefs reemerged during the Olenekian, mainly being composed of sponge biostrome and bivalve builups. Keratose sponges were particularly noteworthy in their integral importance to Early Triassic microbial-metazoan reef communities, and they helped to create stability in heavily damaged ecosystems during early phases of biotic recovery. " Tubiphytes "-dominated reefs appeared at

9744-559: The Gorgon being beheaded on the Boeotian pithos is depicted as a female centaur , with neither wings nor snakes present, and the Gorgons on the Eleusis Amphora, have wingless, wasp-shaped bodies with cauldron-like heads, by the end of the seventh century BC, humanoid bodies, with wings, and snakes around their head, necks, or waist, such as depicted on the Medusa pediment, become typical. Unlike

9918-516: The Gorgons chasing Perseus also had "horrible snaky hair", so too in Prometheus Bound where all three Gorgons are described as "winged" as well as "snake-haired". The Gorgon's reputation for ugliness was such that the Athenian comic playwright Aristophones could, in 405 BC, ridicule the women of the Athenian deme Teithras by referring to them as Gorgons. The mythographer Apollodorus gives

10092-545: The Gorgons could turn to stone anyone who saw them. Stheno and Euryale were immortal, whereas Medusa was mortal. According to Apollodorus' version of their story, Perseus was ordered by Polydectes (his enemy) to bring back the head of Medusa. So guided by Hermes and Athena , he sought out the sisters of the Gorgons, the Graeae who had only one eye and one tooth which they shared. Perseus managed to steal their eye and tooth, and refused to return them, unless they would show him

10266-478: The Gorgons, other than to say that the two Gorgons, Sthenno, and Euryale did not grow old. Homer mentions only "the Gorgon" (otherwise unnamed) giving brief descriptions of her, and her head. In the Iliad she is called a "dread monster" and the image of her head, which appears—along with several other terrifying images—on Athena 's aegis , and Agamemnon 's shield, is described as "dread and awful", and "grim of aspect, glaring terribly". Already in

10440-683: The Karoo Basin indicates a protracted extinction lasting a million years. Other evidence from the Karoo deposits suggest it took 50,000 years or less, while a study of coprolites in the Vyazniki fossil beds in Russia suggests it took only a few thousand years. Aridification induced by global warming was the chief culprit behind terrestrial vertebrate extinctions. There is enough evidence to indicate that over two thirds of terrestrial labyrinthodont amphibians , sauropsid ("reptile") and therapsid ("proto-mammal") taxa became extinct. Large herbivores suffered

10614-465: The Karoo Supergroup were cold-blooded reptiles, despite bearing teeth resembling those of carnivorous mammals. He proposed classifying all of them under the newly coined order Theriodontia (which he placed in the class Reptilia). He decided to subdivide Theriodontia into families based on the anatomy of the nostrils (the bony narials)—"Mononarialia" for those with one opening in the skull for

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10788-477: The Late Cretaceous to recover their full diversity. Crinoids ("sea lilies") suffered a selective extinction, resulting in a decrease in the variety of their forms. Though cladistic analyses suggest the beginning of their recovery to have taken place in the Induan, the recovery of their diversity as measured by fossil evidence was far less brisk, showing up in the late Ladinian. Their adaptive radiation after

10962-708: The Late Permian Kundaram Formation to a medium-sized gorgonopsian, though the gorgonopsian characteristics have also been documented in some therocephalians. In 2008, a large and probably rubidgeine upper jaw fragment and canine was identified at the Late Permian Moradi Formation in Niger (one of the few low-latitude Late Permian tetrapod-bearing formations), and is the first evidence of a low-latitude gorgonopsian. Upon discovery, Owen presumed that Gorgonops and several other taxa he described from

11136-628: The Medusa pediment from the temple of Artemis in Corfu (Fig. 6) shows affinities with images of Lamashtu. As Walter Burkert has noted, Lamashtu has several characteristic iconographic elements which include an animalistic head atop a humanoid body, often in the Knielauf (kneeling-running) position, with the presence of snakes, a horse or ass, animal offspring, and sometimes in the Mistress of Animals configuration. All of these elements are present, for example, in

11310-475: The Medusa pediment. Images which show Perseus, with head turned away, decapitating Medusa (Figs. 1, 7), resemble Mesopotamian depictions of Gilgamesh slaying the wild man Humbaba . Such depictions can show Gilgamesh with head turned away looking behind him for a goddess to pass him a weapon. In particular, a bronze shield strap from Olympia (mid-sixth century BC), which shows Perseus with his head turned away about to decapitate Medusa, assisted by Athena, bears

11484-634: The Middle Permian as the world progressively became drier. Gorgonopsians rose to become apex predators of their environments following the Capitanian mass extinction event which killed off the dinocephalians and some large therocephalians after the Middle Permian. Despite the existence of a single continent during the Permian, Pangaea , gorgonopsians have only been found in the Karoo Supergroup (primarily in South Africa, but also in Tanzania, Zambia, and Malawi),

11658-659: The Middle Permian to bear -like proportions of up to 60 cm (2 ft) in the Upper Permian. The latest gorgonopsians, Rubidgeinae , were the most robust of the group and could produce especially powerful bites. Gorgonopsians are thought to have been completely terrestrial and could walk with a semi-erect gait, with a similar terrestrial locomotory range as modern crocodilians . They may have been more agile than their prey items, but were probably inertial homeotherms rather than endotherms unlike contemporary therocephalians and cynodonts , and thus were probably comparatively less active. Though gorgonopsians were able to maintain

11832-447: The Middle Triassic, with the exception of a notable Ladinian fauna from the Catalonian Basin. Microbial reefs were common across shallow seas for a short time during the earliest Triassic, predominating in low latitudes while being rarer in higher latitudes, occurring both in anoxic and oxic waters. Polybessurus -like microfossils often dominated these earliest Triassic microbialites . Microbial-metazoan reefs appeared very early in

12006-420: The PTME, being the most severely affected clade among the lophophorates. Deep water sponges suffered a significant diversity loss and exhibited a decrease in spicule size over the course of the PTME. Shallow water sponges were affected much less strongly; they experienced an increase in spicule size and much lower loss of morphological diversity compared to their deep water counterparts. Foraminifera suffered

12180-546: The PTME, but some tentative evidence suggests they may have survived into the Triassic. Freshwater and euryhaline fishes, having experienced minimal diversity losses before the PTME, were unaffected during the PTME and actually appear to have increased in diversity across the Permian-Triassic boundary. However, faunal turnovers in freshwater fish communities occurred in areas like the Kuznetsk Basin. The groups that survived suffered extremely heavy losses of species and some terrestrial vertebrate groups very nearly became extinct at

12354-399: The PTME. The Cordaites flora, which dominated the Angaran floristic realm corresponding to Siberia, collapsed over the course of the extinction. In the Kuznetsk Basin , the aridity-induced extinction of the regions's humid-adapted forest flora dominated by cordaitaleans occurred approximately 252.76 Ma, around 820,000 years before the end-Permian extinction in South China, suggesting that

12528-500: The Permian mass extinction event, both complex and simple marine ecosystems were equally common. After the recovery from the mass extinction, the complex communities outnumbered the simple communities by nearly three to one, and the increase in predation pressure and durophagy led to the Mesozoic Marine Revolution . Marine vertebrates recovered relatively quickly, with complex predator-prey interactions with vertebrates at

12702-506: The Permian-Triassic boundary are highly variable depending on the location and preservation quality of any given site. Plants are relatively immune to mass extinction, with the impact of all the major mass extinctions "insignificant" at a family level. Floral diversity losses were more superficial than those of marine animals. Even the reduction observed in species diversity (of 50%) may be mostly due to taphonomic processes. However,

12876-462: The Permian-Triassic boundary, with this flora's collapse being less constrained in western Gondwana but still likely occurring a few hundred thousand years before the boundary. The collapse of this flora is indirectly marked by an abrupt change in river morphology from meandering to braided river systems, signifying the widespread demise of rooted plants. Palynological or pollen studies from East Greenland of sedimentary rock strata laid down during

13050-494: The Permian-Triassic boundary. The extinction occurred between 251.941 ± 0.037 and 251.880 ± 0.031 million years ago, a duration of 60 ± 48 thousand years. A large, abrupt global decrease in δ C , the ratio of the stable isotope carbon-13 to that of carbon-12 , coincides with this extinction, and is sometimes used to identify the Permian–Triassic boundary and PTME in rocks that are unsuitable for radiometric dating . The negative carbon isotope excursion's magnitude

13224-513: The Permian-Triassic mass extinction marked a key turning point in this ecological shift that began after the Capitanian mass extinction and culminated in the Late Jurassic . Typical taxa of shelly benthic faunas were now bivalves , snails , sea urchins and Malacostraca , whereas bony fishes and marine reptiles diversified in the pelagic zone . On land, dinosaurs and mammals arose in

13398-454: The Permian–Triassic boundary. The best-known record of vertebrate changes across the Permian–Triassic boundary occurs in the Karoo Supergroup of South Africa , but statistical analyses have so far not produced clear conclusions. One study of the Karoo Basin found that 69% of terrestrial vertebrates went extinct over 300,000 years leading up to the Permian-Triassic boundary, followed by a minor extinction pulse involving four taxa that survived

13572-580: The Perseus-Medusa story. The earliest representations (mid-seventh century BC) of such Gorgons are a Boeotian relief pithos (Fig. 1), which depicts Perseus, with head turned away, decapitating a Gorgon, and the Eleusis Amphora (Fig. 2), which shows two Gorgons chasing Perseus fleeing with a severed Gorgon head. That the Perseus on the pithos averts his gaze shows that already in these earliest images it

13746-594: The Reverend John H. Whaits, Broom reinstated Gorgonopsia. The number of South African genera rapidly grew in the 20th-century, headed principally by Broom, whose extensive work on the Karoo therapsids—from the beginning of his career in the country in 1897 to his death in 1951—led to his description of 57 gorgonopsian holotype specimens and 29 genera. Many of Broom's taxa would later be invalidated. Many other contemporary workers created wholly new species or genera based on single specimens. Consequently, Gorgonopsia has been

13920-589: The Russian genera named, Leogorgon , is now considered as a nomen dubium . Gorgonopsians are conspicuously absent beyond these two areas. In 1979, Chinese palaeontologist Yang Zhongjian described a Chinese gorgonopsian " Wangwusaurus tayuensis " based on teeth from the Late Permian Jiyuan Formation , but in 1981, palaeontologists Denise Sigogneau-Russell and Ai-Lin Sun found the assigned material to be

14094-515: The Russian taxa, instead considered Gorgonopsia a suborder, and grouped it together with Dinocephalia into the order "Gorgodontia". He divided Gorgonopsia into the superfamilies "Gorgonopioidea" (families Gorgonopidae, Cyonosauridae, and Galesuchidae) and "Rubidgeoidea" (Rubidgeidae, Phtinosuchidae, and Inostranceviidae). In 2007, biologist Eva V. I. Gebauer, in her comprehensive review of Gorgonopsia (her PhD dissertation), rejected Ivakhnenko's model in favour of Sigogneau-Russell's, and further reduced

14268-499: The Sanskrit garğ , with its connotations of a growling beast—was also part of their mythology. The Hesiodic Shield of Heracles (c. late seventh–mid-sixth century BC), which describes Heracles' shield, has the Gorgons depicted on it chasing Perseus, with their shrill cry seemingly being heard emanating from the shield itself: The Gorgons, dreadful and unspeakable, were rushing after him, eager to catch him; as they ran on

14442-432: The Spathian and Anisian. Accordingly, low levels of interspecific competition in seafloor communities that are dominated by primary consumers correspond to slow rates of diversification and high levels of interspecific competition among nektonic secondary and tertiary consumers to high diversification rates. Other explanations state that life was delayed in its recovery because grim conditions returned periodically over

14616-536: The Spathian. Despite high taxonomic turnover, the ecological life modes of Early Triassic ostracods remained rather similar to those of pre-PTME ostracods. Bryozoans in the Early Triassic were restricted to the Boreal realm. They were also not diverse, represented mainly by members of Trepostomatida . During the Middle Triassic, there was a rise in bryozoan diversity, which peaked in the Carnian. However, bryozoans took until

14790-515: The Sydney Basin of the PTME's duration and course also supports a synchronous occurrence of the terrestrial and marine biotic collapses. Other scientists believe the terrestrial mass extinction began between 60,000 and 370,000 years before the onset of the marine mass extinction. Chemostratigraphic analysis from sections in Finnmark and Trøndelag shows the terrestrial floral turnover occurred before

14964-497: The Triassic, taking over niches that were filled primarily by brachiopods before the mass extinction event. Bivalves were once thought to have outcompeted brachiopods, but this outdated hypothesis about the brachiopod-bivalve transition has been disproven by Bayesian analysis . The success of bivalves in the aftermath of the extinction event may have been a function of them possessing greater resilience to environmental stress compared to

15138-460: The adaptive shift from pelycosaur-grade to therapsid-grade took place during the Middle Permian ( Olson's Extinction ); however, the classification of those "therapsids" and the age of the formations have since been challenged. Thus, the exact timing of the therapsid takeover is unclear, but the six major therapsid groups ( Biarmosuchia , Dinocephalia , Anomodontia , Gorgonopsia, Therocephalia, and Cynodontia) had evolved by 265 million years ago during

15312-788: The basal " Pelycosauria " and the derived Therapsida. The former comprises cold-blooded creatures with a sprawling gait and presumably lower metabolism which evolved in the Upper Carboniferous . Through the middle to late 20th-century, American palaeontologist Everett C. Olson investigated synapsid diversity in the Middle Permian San Angelo , Flowerpot , and Chickasha Formations in North America, and noted that pelycosaur diversity reduced from six to three in these formations, and that they coexisted with several fragmentary specimens which he interpreted as therapsids. He then suggested

15486-625: The bottoms of bowls and cups. As with full-bodied Gorgons the earliest representations are found from the mid-sixth century BC. The earliest example of a "beautiful" gorgoneion is the Medusa Rondanini (Fig. 19), which is thought to be a Roman copy of a Greek original dated to either the fifth-century BC or the Hellenistic period. Athena's victory over the Giant Enceladus —with a gorgoneion on her shield—was apparently depicted on

15660-423: The brachiopods that they coexisted with, whilst other studies have emphasised the greater niche breadth of the former. The rise of bivalves to taxonomic and ecological dominance over brachiopods was not synchronous, however, and brachiopods retained an outsized ecological dominance into the Middle Triassic even as bivalves eclipsed them in taxonomic diversity. Some researchers think the brachiopod-bivalve transition

15834-434: The canines grew to match the size of the skull, and continually broke off until the animal stopped growing, and that gorgonopsians featured an early version of finite tooth replacement exhibited in many mammals. The tooth replacement patterns of the other teeth are unclear. The postcanine teeth were replaced more slowly than the other teeth, likely due to their lack of functional significance. The seven cervical vertebrae (in

16008-466: The cervical vertebrae is overall reptilian, permitting side-to-side movement of the head but restricting up-and-down motion. The last cervical is shaped more like the dorsal vertebrae . The dorsals are spool-shaped and all appear about the same as each other. The spinous processes jut out steeply from the centra, and feature sharp keels on the front and back sides. Unlike eutheriodonts, gorgonopsians do not have distinguished lumbar vertebrae . Nonetheless,

16182-508: The classification of Reptilia in 1903, and erected two major groups: Diapsida and Synapsida , and in 1905, South African palaeontologist Robert Broom created a third group, Therapsida , to house the "mammal-like reptiles", including Theriodontia. He also challenged Seeley's claim and relegated Gorgonops back to Theriodontia, but he placed it into his newly erected subgroup Therocephalia , dissolving Gorgonopsia. In 1913, especially in light of an almost complete G. torvus skull discovered by

16356-487: The closest meaning for the stem might be the onomatopoeic grrr of a growling beast. According to Hesiod and Apollodorus , the Gorgons were daughters of the primordial sea-god Phorcys and the sea-monster Ceto , and the sisters of three other daughters of Phorcys and Ceto, the Graeae . However, according to Hyginus , they were daughters of "the Gorgon", an offspring of Typhon and Echidna , and Ceto, while Euripides , in his tragedy Ion , has "the Gorgon" being

16530-475: The course of the Triassic . The profound change in the taxonomic composition was partly a result of the selectivity of the extinction event, which affected some taxa (e.g., brachiopods ) more severely than others (e.g., bivalves ). However, recovery was also differential between taxa. Some survivors became extinct some million years after the extinction event without having rediversified ( dead clade walking , e.g.

16704-627: The course of the Early Triassic, causing further extinction events, such as the Smithian-Spathian boundary extinction . Continual episodes of extremely hot climatic conditions during the Early Triassic have been held responsible for the delayed recovery of oceanic life, in particular skeletonised taxa that are most vulnerable to high carbon dioxide concentrations. The relative delay in the recovery of benthic organisms has been attributed to widespread anoxia, but high abundances of benthic species contradict this explanation. A 2019 study attributed

16878-623: The depictions of gods and heroes, which are usually shown in profile, Archaic Gorgons, even when their bodies are presented in profile (usually running), their heads are (as noted above) always turned frontally displaying their full face, directly gazing at the viewer. Of the depictions of ancient Greek demons, the gorgoneion is, by far, the most frequently occurring. Thought to have had an apotropaic (protective) function, gorgoneia are often found on architectural elements such as temple pediments, and ornamental antefixes and acroteria , or decorating various round objects, such as shields, coins, and

17052-547: The development of gorgoneia, or gorgoneia might have come first, in which case the Perseus story might have served an etiological function, as an origin myth , developed as a way to explain where gorgoneia had come from. It is also possible that the Perseus story and gorgoneia developed independently, but later converged. Since the earliest literary and iconographic evidence of both the Perseus story and gorgoneia are roughly contemporaneous, such evidence seems unable to definitively distinguish between any of these three scenarios. It

17226-460: The die-off of plants being their likely cause. Wildfires too likely played a role in the fall of Gigantopteris . A conifer flora in what is now Jordan, known from fossils near the Dead Sea , showed unusual stability over the Permian-Triassic transition, and appears to have been only minimally affected by the crisis. The tempo of the terrestrial vertebrate extinction is disputed. Some evidence from

17400-423: The dissimilarity of recovery times between different ecological communities to differences in local environmental stress during the biotic recovery interval, with regions experiencing persistent environmental stress post-extinction recovering more slowly, supporting the view that recurrent environmental calamities were culpable for retarded biotic recovery. Recurrent Early Triassic environmental stresses also acted as

17574-415: The dorsals equating to that series are similar to the lumbars of sabre-toothed cats with steeply oriented zygopophases, useful in stabilising the lower back especially when pinning down struggling prey. There are three sacral vertebrae , and the series attached to the pelvis by the first vertebra. The pelvis is reptilian, with separated ilium , ischium , and pubis . The femur is slightly s-shaped, and

17748-615: The edge of night where the Hesperides (and the Graeae?) live. The Cypria apparently had the Gorgons living in Oceanus on a rocky island named Sarpedon. Aeschylus 's Prometheus Bound places them in the far east "across the surging sea" on the "Gorgonean plains of Cisthene", where the Graeae live, while his lost play Phorkides (another name for the Graeae) apparently placed them at "Lake Tritonis",

17922-487: The end of the Olenekian, representing the earliest platform-margin reefs of the Triassic, though they did not become abundant until the late Anisian, when reefs' species richness increased. The first scleractinian corals appear in the late Anisian as well, although they would not become the dominant reef builders until the end of the Triassic period. Bryozoans, after sponges, were the most numerous organisms in Tethyan reefs during

18096-440: The end of the Permian. Some of the surviving groups did not persist for long past this period, but others that barely survived went on to produce diverse and long-lasting lineages. However, it took 30   million years for the terrestrial vertebrate fauna to fully recover both numerically and ecologically. It is difficult to analyze extinction and survival rates of land organisms in detail because few terrestrial fossil beds span

18270-439: The end-Capitanian had finished, depending on the factor considered. Many of the extinctions once dated to the Permian-Triassic boundary have more recently been redated to the end- Capitanian . Further, it is unclear whether some species who survived the prior extinction(s) had recovered well enough for their final demise in the Permian-Triassic event to be considered separate from Capitanian event. A minority point of view considers

18444-497: The end-Permian biotic catastrophe may have started earlier on land and that the ecological crisis may have been more gradual and asynchronous on land compared to its more abrupt onset in the marine realm. In North China, the transition between the Upper Shihhotse and Sunjiagou Formations and their lateral equivalents marked a very large extinction of plants in the region. Those plant genera that did not go extinct still experienced

18618-630: The end-Permian extinction. Additionally, the complex Guiyang biota found near Guiyang , China also indicates life thrived in some places just a million years after the mass extinction, as does a fossil assemblage known as the Shanggan fauna found in Shanggan, China, the Wangmo biota from the Luolou Formation of Guizhou, and a gastropod fauna from the Al Jil Formation of Oman. Regional differences in

18792-498: The expansion of more habitable climatic zones. Brachiopod taxa during the Anisian recovery interval were only phylogenetically related to Late Permian brachiopods at a familial taxonomic level or higher; the ecology of brachiopods had radically changed from before in the mass extinction's aftermath. Ostracods were extremely rare during the basalmost Early Triassic. Taxa associated with microbialites were disproportionately represented among ostracod survivors. Ostracod recovery began in

18966-415: The extinction event resulted in forms possessing flexible arms becoming widespread; motility , predominantly a response to predation pressure, also became far more prevalent. Though their taxonomic diversity remained relatively low, crinoids regained much of their ecological dominance by the Middle Triassic epoch. Stem-group echinoids survived the PTME. The survival of miocidarid echinoids such as Eotiaris

19140-547: The extinction event. Prior to the extinction, about two-thirds of marine animals were sessile and attached to the seafloor. During the Mesozoic, only about half of the marine animals were sessile while the rest were free-living. Analysis of marine fossils from the period indicated a decrease in the abundance of sessile epifaunal suspension feeders such as brachiopods and sea lilies and an increase in more complex mobile species such as snails , sea urchins and crabs . Before

19314-409: The extinction period indicate dense gymnosperm woodlands before the event. At the same time that marine invertebrate macrofauna declined, these large woodlands died out and were followed by a rise in diversity of smaller herbaceous plants including Lycopodiophyta , both Selaginellales and Isoetales . Data from Kap Stosch suggest that floral species richness was not significantly affected during

19488-543: The extinction was long and spread out over a few million years, with a sharp peak in the last million years of the Permian. Statistical analyses of some highly fossiliferous strata in Meishan, Zhejiang Province in southeastern China, suggest that the main extinction was clustered around one peak, while a study of the Liangfengya section found evidence of two extinction waves, MEH-1 and MEH-2, which varied in their causes, and

19662-569: The final extinction killed off only about 80% of marine species alive at that time, whereas the other losses occurred during the first pulse or the interval between pulses. According to this theory, one of these extinction pulses occurred at the end of the Guadalupian epoch of the Permian. For example, all dinocephalian genera died out at the end of the Guadalupian, as did the Verbeekinidae ,

19836-409: The final two sedimentary zones containing conodonts from the Permian. The decrease in diversity was probably caused by a sharp increase in extinctions, rather than a decrease in speciation . The extinction primarily affected organisms with calcium carbonate skeletons, especially those reliant on stable CO 2 levels to produce their skeletons. These organisms were susceptible to the effects of

20010-403: The first three were the same size as each other, and the last two were shorter) and four on the bottom. In the majority of gorgonopsians, the incisors were large, and the upper canines were elongated into sabres, much like those of later sabre-toothed cats . Some gorgonopsians had exceptionally long upper canines, such as Inostrancevia , and some of them had a flange on the lower jaw to sheath

20184-403: The forebrain, a large epyphysial nerve (found in creatures with a parietal eye on the top of the head), an enlarged pituitary gland , and an overall elongated shape; all-in-all resembling a reptilian brain. The braincase was also rather reptilian, and is also comparatively smaller and not as thick as those of mammals. The flocculus , a lobe of the cerebellum , is proportionally large, and

20358-414: The fourth century BC. One of the earliest such "beautiful" Gorgons (mid-fifth century BC) is a red-figure pelike (Fig. 11), which shows Perseus, with head turned away, about to behead a sleeping Medusa. While gorgoneia continue to be ubiquitous through the end of antiquity, after the fourth century BC full-bodied Gorgons ceased to be represented. Full-bodied Gorgons are usually shown in connection with

20532-417: The fragile canines. Similar ridges have been identified on the machairodont Homotherium . The postcanine teeth were reduced in both size and number; many rubidgeines (the latest gorgonopsians) did not have postcanines in the lower jaw, and Clelandina lacked them entirely. Gorgonopsians were polyphyodonts , and teeth grew continuously throughout an individual's life. Like some therapsids, while there

20706-405: The fungi. This "fungal spike" has been used by some paleontologists to identify a lithological sequence as being on or very close to the Permian–Triassic boundary in rocks that are unsuitable for radiometric dating or have a lack of suitable index fossils . However, even the proposers of the fungal spike hypothesis pointed out that "fungal spikes" may have been a repeating phenomenon created by

20880-441: The greater range of environmental tolerance and greater geographic distribution of the former compared to the latter. Cladodontomorph sharks likely survived the extinction by surviving in refugia in the deep oceans, a hypothesis based on the discovery of Early Cretaceous cladodontomorphs in deep, outer shelf environments. Ichthyosaurs , which evolved immediately before the PTME, were also PTME survivors. The Lilliput effect ,

21054-421: The greatest loss of species diversity. In the case of the brachiopods, at least, surviving taxa were generally small, rare members of a formerly diverse community. Conodonts were severely affected both in terms of taxonomic and morphological diversity, although not as severely as during the Capitanian mass extinction. The ammonoids , which had been in a long-term decline for the 30 million years since

21228-628: The heaviest losses. All Permian anapsid reptiles died out except the procolophonids (although testudines have morphologically -anapsid skulls, they are now thought to have separately evolved from diapsid ancestors). Pelycosaurs died out before the end of the Permian. Too few Permian diapsid fossils have been found to support any conclusion about the effect of the Permian extinction on diapsids (the "reptile" group from which lizards, snakes, crocodilians, and dinosaurs (including birds) evolved). Tangasaurids were largely unaffected. Gorgonopsians are traditionally thought to have gone extinct during

21402-423: The inarticulate brachiopod Lingularia , and the foraminifera Earlandia and Rectocornuspira kalhori , the latter of which is sometimes classified under the genus Ammodiscus . Their guild diversity was also low. Post-PTME faunas had a flat, insignificant latitudinal diversity gradient. The speed of recovery from the extinction is disputed. Some scientists estimate that it took 10 million years (until

21576-491: The large negative δ C shift during the marine extinction. Dating of the boundary between the Dicynodon and Lystrosaurus assemblage zones in the Karoo Basin indicates that the terrestrial extinction occurred earlier than the marine extinction. The Sunjiagou Formation of South China also records a terrestrial ecosystem demise predating the marine crisis. Other research still has found that the terrestrial extinction occurred after

21750-467: The largest being Inostrancevia up to 3.5 m (11 ft) in length and 300 kg (660 lb) in body mass. Nonetheless, small gorgonopsians remained abundant until extinction (though small species may actually represent juvenile specimens of other taxa). Like other Permian therapsids, gorgonopsians had developed several mammalian characteristics. These might have included a parasagittal gait (the limbs were vertically oriented and moved parallel to

21924-465: The late 19th century, and the group has been subject to several taxonomic revisions. Most gorgonopsians became extinct during a phase of the Permian–Triassic extinction event taking place at the very end of the Permian, in which major volcanic activity (which would produce the Siberian Traps ) and resultant massive spike in greenhouse gases caused rapid aridification due to temperature spike, acid rain , frequent wildfires , and potential breakdown of

22098-625: The maidens ... she created the many-voiced song of flutes so that she could imitate with musical instruments the shrill cry that reached her ears from the fast-moving jaws of Euryale. Nonnus , in his Dionysiaca , also has the fleeing Perseus "listening for no trumpet but Euryale's bellowing". The desire to evoke this Gorgon cry may account for the typical distended mouth seen in Archaic Gorgon iconography. The earliest literary accounts of Gorgons occur in works by Hesiod and Homer (c. 700–650 BC). Hesiod provides no physical description of

22272-402: The marine extinction in the tropics. Studies of the timing and causes of the Permian-Triassic extinction are complicated by the often-overlooked Capitanian extinction (also called the Guadalupian extinction), just one of perhaps two mass extinctions in the late Permian that closely preceded the Permian-Triassic event. In short, when the Permian-Triassic starts it is difficult to know whether

22446-713: The mass extinction, exemplifying the Lilliput effect's opposite, which has been dubbed the Brobdingnag effect. The Permian had great diversity in insect and other invertebrate species, including the largest insects ever to have existed. The end-Permian is the largest known mass extinction of insects; according to some sources, it may well be the only mass extinction to significantly affect insect diversity. Eight or nine insect orders became extinct and ten more were greatly reduced in diversity. Palaeodictyopteroids (insects with piercing and sucking mouthparts) began to decline during

22620-509: The mere thought that he might encounter there the "head of the Gorgon, that awful monster", leaves "straightway". The Hesiodic Shield describes the Gorgons chasing Perseus as being "dreadful and unspeakable" with two snakes wrapped around their waists, and that "upon the terrible heads of the Gorgons rioted great Fear", perhaps a reference to snakes writhing about their heads. Pindar makes snakes for hair explicit, saying that Perseus' Gorgon head "shimmered with hair made of serpents", and that

22794-506: The mid-Permian; these extinctions have been linked to a change in flora. The greatest decline occurred in the Late Permian and was probably not directly caused by weather-related floral transitions. However, some observed entomofaunal declines in the PTME were biogeographic changes rather than outright extinctions. The geological record of terrestrial plants is sparse and based mostly on pollen and spore studies. Floral changes across

22968-428: The middle to late Lopingian leading up to the end-Permian extinction proper, supporting aspects of the gradualist hypothesis. Additionally, the decline in marine species richness and the structural collapse of marine ecosystems may have been decoupled as well, with the former preceding the latter by about 61,000 years according to one study. Whether the terrestrial and marine extinctions were synchronous or asynchronous

23142-469: The middle". He also mentions Athena's "Gorgon-faced shield" in his tragedy Electra . In vase-painting, Athena is often shown wearing her aegis, fringed with snake-heads. In some accounts, the blood of "the Gorgon" (any Gorgon?) was said to have both the power to heal and harm. According to Euripides' Ion , Athena gave two drops of blood from the Gorgon she slew for her aegis to Erichthonius , one of which "wards off diseases and nourishes life", while

23316-490: The monster is begotten to account for it; then the hero is supplied to account for the slaying of the monster. That gorgoneia were used as apotropaic shield devices, at least, seems evident from Agamemnon's gorgoneion-shield, which Homer describes in the Iliad as displaying "the Gorgon, grim of aspect, glaring terribly, and about her were Terror and Rout". Supporting the view that gorgoneia originated as masks, are two groups of seventh-century BC terracotta gorgonion-like masks:

23490-453: The most detailed description: ... the Gorgons had heads twined about with the scales of dragons, and great tusks like swine's, and brazen hands, and golden wings, by which they flew". While such descriptions emphasize the hideous physical features of the Gorgon, by the fifth century BC, Pindar can also describe his snake-haired Medusa as "beautiful". And the Roman poet Ovid tells us that Medusa

23664-469: The most distinctive feature of archaic representations of Gorgons is that the head is always facing frontally (en face) with its large fierce eyes glaring directly at the viewer. Consistent with the change in literary descriptions seen in the works of Pindar and Ovid mentioned above, beginning in the fifth century BC, representations of Gorgons and gorgoneia transition from hideous monsters to beautiful young women, with such representations becoming typical in

23838-422: The mouth from the nasal cavity, prohibiting chewing. Anatomy varies incredibly little between gorgonopsians. Many species are distinguished by vague proportional differences, and consequently smaller species may actually represent juveniles of larger taxa. Notably, the vomer at the tip of the snout varies among species in terms of the degree of its expansion, as well as the positions, degree of splay, and shape of

24012-423: The much earlier terracotta plaques depicting Humbaba . Medusa and the other Gorgon sisters, Stheno and Euryale , have been featured in art and culture spanning from the days of ancient Greece to present day. Medusa is the most well-known of the three mythological monsters, having been variously portrayed as a monster, a protective symbol, a rallying symbol for liberty, and a sympathetic victim of rape and/or

24186-403: The neck) are all the same size as each other except for the last one, which is shorter and lower; there is one atlas and one axis . Like sabre-toothed cats, the neck is long with well-developed muscles, which would have been especially useful when the canines were sunk into an animal. Like other early synapsids, gorgonopsians have a single occipital condyle , and the articulation (the joints) of

24360-428: The nose as in mammals, "Binarialia" for those with two openings as in reptiles, and "Tectinarialia" for Gorgonops because its opening was overshadowed by a thick bone roof ( tectus is Latin for "covered, roofed, decked"). In 1890, English naturalist Richard Lydekker made Gorgonops the type species of the family Gorgonopsidae. British palaeontologist Harry Seeley in 1895 believed Gorgonops lacked an opening in

24534-414: The number of genera to fourteen in addition to the Russian genera: Aloposaurus , Cyonosaurus , Aelurosaurus , Sauroctonus , Scylacognathus , Eoarctops , Gorgonops , " Dixeya " nasuta (under the informal nomen nudum " Njalila "), Lycaenops , Arctognathus , Aelurognathus , Sycosaurus , Clelandina , and Rubidgea . In general, Sigogneau-Russell's model is supported, but there

24708-488: The ocean-atmosphere system during this period. Several other contributing factors have been proposed, including the emission of carbon dioxide from the burning of oil and coal deposits ignited by the eruptions; emissions of methane from the gasification of methane clathrates ; emissions of methane by novel methanogenic microorganisms nourished by minerals dispersed in the eruptions; longer and more intense El Niño events; and an extraterrestrial impact which created

24882-575: The offspring of Gaia , spawned by Gaia to be an ally for her children the Giants in their war against the Olympian gods. Medusa had two offspring by Poseidon , the winged-horse Pegasus and the warrior Chrysaor . Where the Gorgons were supposed to live varies in the ancient sources. According to Hesiod, the Gorgons lived far to the west beyond Oceanus (the Titan, and world-circling river) near its springs, at

25056-501: The other "kills, as it is poison from the Gorgon serpents". While according to Apollodorus, Athena gave Asclepius some of the blood the Gorgon, "and while he used the blood that flowed from the veins on the left side for the bane of mankind, he used the blood that flowed from the right side for salvation, and by that means he raised the dead." The loud cry that came from the Gorgons—;perhaps related to 'Gorgon' being derived from

25230-475: The pace of biotic recovery existed, which suggests that the impact of the extinction may have been felt less severely in some areas than others, with differential environmental stress and instability being the source of the variance. In addition, it has been proposed that although overall taxonomic diversity rebounded rapidly, functional ecological diversity took much longer to return to its pre-extinction levels; one study concluded that marine ecological recovery

25404-411: The pallid adamant, the shield resounded sharply and piercingly with a loud noise. Pindar tells us that the cry of the Gorgons, lamenting the death of Medusa during their pursuit of Perseus, was the reason Athena invented the flute. According to Pindar, the goddess: wove into music the dire dirge of the reckless Gorgons which Perseus heard pouring in slow anguish from beneath the horrible snakey hair of

25578-471: The parameters were now shared differently among clades . Ostracods experienced prolonged diversity perturbations during the Changhsingian before the PTME proper, when immense proportions of them abruptly vanished. At least 74% of ostracods died out during the PTME itself. Bryozoans had been on a long-term decline throughout the Late Permian epoch before they suffered even more catastrophic losses during

25752-516: The phenomenon of dwarfing of species during and immediately following a mass extinction event, has been observed across the Permian-Triassic boundary, notably occurring in foraminifera, brachiopods, bivalves, and ostracods. Though gastropods that survived the cataclysm were smaller in size than those that did not, it remains debated whether the Lilliput effect truly took hold among gastropods. Some gastropod taxa, termed "Gulliver gastropods", ballooned in size during and immediately following

25926-403: The post-extinction ecosystem during the earliest Triassic. The very idea of a fungal spike has been criticized on several grounds, including: Reduviasporonites , the most common supposed fungal spore, may be a fossilized alga ; the spike did not appear worldwide; and in many places it did not fall on the Permian–Triassic boundary. The Reduviasporonites may even represent a transition to

26100-405: The previous extinction interval. Another study of latest Permian vertebrates in the Karoo Basin found that 54% of them went extinct due to the PTME. In the wake of the extinction event, the ecological structure of present-day biosphere evolved from the stock of surviving taxa. In the sea, the "Palaeozoic evolutionary fauna" declined while the "modern evolutionary fauna" achieved greater dominance;

26274-456: The quick recovery seen in nektonic organisms such as ammonoids , which exceeded pre-extinction diversities already two million years after the crisis, and conodonts, which diversified considerably over the first two million years of the Early Triassic. Recent work suggests that the pace of recovery was intrinsically driven by the intensity of competition among species, which drives rates of niche differentiation and speciation . That recovery

26448-525: The same time period, the mid-seventh century BC. Archaic Gorgons typically have snaky hair either with snake-like curls (Figs. 8, 9), or actual snakes protruding from their heads (Figs. 2, 5, 6, 10). The faces of Archaic Gorgons are particularly distinctive, typically with large menacing eyes, tripartite scroll-like ( volute ) noses, wide mouths with rictus-like grins or grimaces, lolling tongues, fangs and/or tusks (Figs. 4, 5, 6), and sometimes beards (Figs. 3, 4, 13, 15). Aside from its particular monstrousness,

26622-412: The sequence of environmental disasters to have effectively constituted a single, prolonged extinction event, perhaps depending on which species is considered. This older theory, still supported in some recent papers, proposes that there were two major extinction pulses 9.4 million years apart, separated by a period of extinctions that were less extensive, but still well above the background level, and that

26796-417: The snail family Bellerophontidae ), whereas others rose to dominance over geologic times (e.g., bivalves). A cosmopolitanism event began immediately after the end-Permian extinction event. Marine post-extinction faunas were mostly species-poor and were dominated by few disaster taxa such as the bivalves Claraia , Unionites , Eumorphotis , and Promyalina , the conodonts Clarkina and Hindeodus ,

26970-422: The spine) as opposed to the sprawling gait of amphibians and earlier synapsids. This gait change in therapsids was possibly related to the reduction in tail size and phalangeal formula (the number of bones per digit, which for gorgonopsians was 2.3.4.5.3 like reptiles). Other developments included fibrous lamellar cortical bone and deeply-set teeth. Like reptiles, gorgonopsians lack a secondary palate separating

27144-401: The subfamily and the nine species he assigned to it (reducing the number from thirty-six species). Kammerer also resurrected Dinogorgon , Leontosaurus , Ruhuhucerberus , and Smilesaurus . Kammerer was unsure if Leontosaurus , Clelandina , Dinogorgon , and Rubidgea all represent the same taxon or not (for which Dinogorgon has priority ), but he decided to classify all of them in

27318-466: The subject of much taxonomic turmoil, and is one of the most problematic synapsid groups. Because the skull anatomy differs very little across taxa, many are defined based on vague proportional differences, including even the well-known members. Nominal species are distinguished predominantly by traits which are known to be quite variable depending on the age of the individual, including eye orbit size, snout length, and number of postcanine teeth. Thus, it

27492-409: The temporal bone (temporal fenestra), which is a diagnostic feature of Theriodontia, and so elevated Gorgonopsidae to Gorgonopsia, distinct from Theriodontia. He classified all South African materials bearing both reptilian and mammalian traits into the order "Theriosuchia", and considered Gorgonopsia and Theriodontia suborders of it. American palaeontologist Henry Fairfield Osborn completely reworked

27666-607: The tip of the canine while the mouth was closed. Sabres are generally interpreted as having been used as stabbing or slashing weapons, which would have required an extremely wide gape. Both the upper and lower canines of Rubidgea were elongated, and the animal would have needed an even greater gape. The serration pattern of gorgonopsians was most similar to those of theropod dinosaurs than to other synapsids. The palate also features tuberosities and ridges which oftentimes have functional teeth, which may have been used to hold onto struggling prey, diverting these powerful forces away from

27840-420: The top of the food web being known from coprolites five million years after the PTME. Post-PTME hybodonts exhibited extremely rapid tooth replacement. Ichthyopterygians appear to have ballooned in size extremely rapidly following the PTME. Bivalves rapidly recolonised many marine environments in the wake of the catastrophe. Bivalves were fairly rare before the P–Tr extinction but became numerous and diverse in

28014-504: The way to the nymphs, which they did. Perseus got from the nymphs, winged sandals, which allowed him to fly, and the cap of Hades , which made him invisible. He also received an adamantine sickle ( harpē ) from Hermes. Perseus then flew to Oceanus, found the Gorgons asleep. And when Perseus managed to behead Medusa by looking at her reflection in his bronze shield, Pegasus and Chrysaor sprang from Medusa's neck, and Stheno and Euryale chased after him, but were unable to see him because he

28188-475: Was 4-7% and lasted for approximately 500 kyr, though estimating its exact value is challenging due to diagenetic alteration of many sedimentary facies spanning the boundary. Further evidence for environmental change around the Permian-Triassic boundary suggests an 8 °C (14 °F) rise in temperature, and an increase in CO 2 levels to 2,500  ppm (for comparison, the concentration immediately before

28362-588: Was attributable not only to the end-Permian extinction but also the ecological restructuring that began as a result of the Capitanian extinction. Infaunal habits in bivalves became more common after the PTME. Linguliform brachiopods were commonplace immediately after the extinction event, their abundance having been essentially unaffected by the crisis. Adaptations for oxygen-poor and warm environments, such as increased lophophoral cavity surface, shell width/length ratio, and shell miniaturisation, are observed in post-extinction linguliforms. The surviving brachiopod fauna

28536-463: Was born. However, Euripides , in his tragedy Ion , has a character say that Athena's aegis was made from the skin of the Gorgon, the offspring of Gaia , who Gaia had brought forth as an ally for her children the Giants and who Athena had killed during the Gigantomachy . In the same play, Euripides has Creusa describe a weaving she made "like an aegis, bordered with serpents" with a "Gorgon in

28710-528: Was displayed on Athena 's aegis , giving it the power both to protect her from any weapon, and instill great fear in any enemy. Gorgon blood was said to have both the power to heal and harm. Representations of full-bodied Gorgons and the Gorgon face, called a gorgoneion (pl. gorgoneia), were popular subjects in Ancient Greek, Etruscan and Roman iconography. While Archaic Gorgons and gorgoneia are universally depicted as hideously ugly, over time they came to be portrayed as beautiful young women. The name 'Gorgon'

28884-458: Was in his ritual a horrid thing called a Gorgoneion, a grinning mask with glaring eyes and protruding beast-like tusks and pendent tongue. How did this Gorgoneion come to be? A hero had slain a beast called the Gorgon, and this was its head. Though many other associations gathered round it, the basis of the Gorgoneion is a cultus object, a ritual mask misunderstood. The ritual object comes first; then

29058-410: Was non-selective, consistent with a catastrophic initiator. During the Triassic, diversity rose rapidly, but disparity remained low. The range of morphospace occupied by the ammonoids, that is, their range of possible forms, shapes or structures, became more restricted as the Permian progressed. A few million years into the Triassic, the original range of ammonoid structures was once again reoccupied, but

29232-489: Was one functional canine, another canine was growing to replace it when it inevitably broke off. The left and right sides of the jaws did not have to be synchronous, so, for example, the first canine on the left side could be functional while the first canine on the right side was still growing. Such a method might have been in play so as always to have a set of functional canines, as having a single or no canines would have severely impeded hunting, and growing such large teeth took

29406-582: Was originally a beautiful maiden, but because of a sexual encounter with Neptune (the Roman equivalent of the Greek Poseidon ) in Minerva 's temple (Minerva being the Roman equivalent of the Greek Athena ), Minerva punished Medusa by transforming her beautiful hair into horrible snakes. Gorgons were a popular subject in ancient Greek, Etruscan and Roman art, with over six hundred representations cataloged in

29580-425: Was slow in the Early Triassic can be explained by low levels of biological competition due to the paucity of taxonomic diversity, and that biotic recovery explosively accelerated in the Anisian can be explained by niche crowding, a phenomenon that would have drastically increased competition, becoming prevalent by the Anisian. Biodiversity rise thus behaved as a positive feedback loop enhancing itself as it took off in

29754-519: Was still ongoing 50 million years after the extinction, during the latest Triassic, even though taxonomic diversity had rebounded in a tenth of that time. The pace and timing of recovery also differed based on clade and mode of life. Seafloor communities maintained a comparatively low diversity until the end of the Early Triassic, approximately 4 million years after the extinction event. Epifaunal benthos took longer to recover than infaunal benthos. This slow recovery stands in remarkable contrast with

29928-467: Was understood that looking directly at the Gorgon's face was deadly. Of particular interest is the famous Medusa pediment (early sixth century BC) from the temple of Artemis in Corfu (Fig. 6), which shows a winged-Medusa in the characteristic Knielauf (kneeling-running) position, with two snakes wrapped around her waist, like the Gorgons described in the Hesiodic Shield of Heracles . Although

30102-435: Was very low in diversity and exhibited no provincialism whatsoever. Brachiopods began their recovery around 250.1 ± 0.3 Ma, as marked by the appearance of the genus Meishanorhynchia , believed to be the first of the progenitor brachiopods that evolved after the mass extinction. Major brachiopod rediversification only began in the late Spathian and Anisian in conjunction with the decline of widespread anoxia and extreme heat and

30276-428: Was wearing Hades' cap of invisibility. When Perseus brought back the Gorgon head, as ordered, with averted eyes he showed the head to Polydectes who was turned to stone. Perseus returned the things he had acquired from the nymphs and Hermes, but gave the Gorgon head to Athena. According to Apollodorus, after Perseus gave the Gorgon head to Athena, she "inserted the Gorgon's head in the middle of her shield", apparently

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