Dévonien (Plioart)
380 million years ago. Fran age, Devonian period, Paleozoic era. Tidal coastal zone located on the territory of the modern Ivanovo region of Russia. The painting shows the hunting of the predatory fish Onychodus on Bothriolepis maxima. In the background on the right is shown, Webererpeton sondalensis, a lobe-finned fish from which only part of the lower jaw was found.
Acrocanthosaurus (Johnson-Mortimer)
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Acrocanthosaurus (« lézard à hautes épines ») est un genre éteint de grands dinosaures théropodes carnivores de la famille des carcharodontosauridés qui ont vécu dans ce qui est maintenant l'Amérique du Nord au cours de l'Aptien et de l'Albien inférieur (Crétacé inférieur). Comme pour la plupart des dinosaures, le genre Acrocanthosaurus n'est représenté que par une seule espèce : A. atokensis ; son nom scientifique est francisé en acrocanthosaure. Ses restes fossiles ont été découverts dans les États de l'Oklahoma et du Texas aux États-Unis, mais des dents qui lui ont été attribuées ont été trouvées jusqu'au Maryland.
Ratons
Infos trouvées ici:
The word "raccoon" is derived from the Algonquian word aroughcoune, "he who scratches with his hands". Spanish-speaking colonists similarly adopted their term, mapache, from mapachtli the Nahuatl word for the animal, meaning roughly "that which has hands".
The genus name, Procyon, comes from the Greek for "before the dog"; this term is also used for the star Procyon of the constellation Canis Minor.
Raccoons are today understood to have a relatively loose evolutionary relationship with bears, which was nonetheless seen as significant by the early taxonomists; Carl Linnaeus initially placed the raccoon in the genus Ursus. In many languages, the raccoon is named for its characteristic dousing behavior in conjunction with that language's term for "bear": Waschbär in German, mosómedve in Hungarian, vaskebjørn in Danish and Norwegian, tvättbjörn in Swedish, wasbeer in Dutch, pesukarhu in Finnish, araiguma (アライグマ) in Japanese, orsetto lavatore in Italian, huànxióng (浣熊) in Chinese and mieshta mechka (миеща мечка) in Bulgarian all mean "washing bear". One exception is Russian, where raccoon is named yenot (енот) due to similarity between raccoon and genet furs. However, the full name of the common raccoon in Russian is also water-related: it is called yenot-poloskun (енот-полоскун), which means "rinsing raccoon".
In some cases, the "washing" descriptor is applied only to the common raccoon species: for example, in French the common raccoon is called raton laveur or "washing rat", while its Linnaean binomial is Procyon lotor or, roughly, "washing pre-dog". In contrast, the crab-eating raccoon is "little crab-catching rat" (raton crabier) and "crab-eating pre-dog" (Procyon cancrivorus) in French and Latin, respectively.
Genetic studies have shown that the closest relatives of the raccoon are the ring-tailed cats, coatis, and cacomistles.
In the first decades after its discovery by the members of the expedition of Christopher Columbus—the first person to leave a written record about the raccoon—taxonomists thought the raccoon was related to such taxonomic groups as dogs, cats, badgers, and particularly bears. Carl Linnaeus, the father of modern taxonomy, placed the raccoon in the genus Ursus, first as Ursus cauda elongata ("long-tailed bear") in the second edition of his Systema Naturae, then as Ursus lotor ("washer bear") in the tenth edition. In 1780, Gottlieb Conrad Christian Storr placed the raccoon in its own genus Procyon, which can be translated either to "before the dog" or "dog-like". It is also possible that Storr had its nocturnal lifestyle in mind and chose the star Procyon as eponym for the species.
Based on fossil evidence from France and Germany, the first known members of the family Procyonidae lived in Europe in the late Oligocene about 25 million years ago. Similar tooth and skull structures suggest procyonids and weasels share a common ancestor, but molecular analysis indicates a closer relationship between raccoons and bears. After the then-existing species crossed the Bering Strait at least six million years later, the center of its distribution was probably in Central America. Coatis (Nasua and Nasuella) and raccoons (Procyon) have been considered to possibly share common descent from a species in the genus Paranasua present between 5.2 and 6.0 million years ago. This assumption, based on morphological comparisons, conflicts with a 2006 genetic analysis that indicates raccoons are more closely related to ringtails.
Unlike other procyonids, such as the crab-eating raccoon (Procyon cancrivorus), the ancestors of the common raccoon left tropical and subtropical areas and migrated farther north about 4 million years ago, in a migration that has been confirmed by the discovery in the Great Plains of fossils dating back to the middle of the Pliocene.
Etymology
The word "raccoon" was adopted into English from a native Powhatan term, as used in the Virginia Colony. (Powhatan is a member of the Native American [Algonquian]] language family.) It was recorded on Captain John Smith's list of Powhatan words as aroughcun, and on that of William Strachey as arathkone. It has also been identified as a Proto-Algonquian root aroughcoune ("ahrah-koon-em"), meaning "[the] one who rubs, scrubs and scratches with its hands." Similarly, Spanish colonists adopted the Spanish word mapache from the Nahuatl mapachitli of the Aztecs, meaning " one who takes everything in its hands".
In many languages, the raccoon is named for its characteristic dousing behavior in conjunction with that language's term for "bear." All of the following mean "washing bear": Waschbär in German, mosómedve in Hungarian, vaskebjørn in Danish and Norwegian, tvättbjörn in Swedish, wasbeer in Dutch, pesukarhu in Finnish, araiguma (アライグマ) in Japanese, orsetto lavatore in Italian, huànxióng (浣熊) in Chinese, and mieshta mechka (миеща мечка) in Bulgarian.
In French and Portuguese (in Portugal), the washing behavior is combined with these languages' term for rat, yielding, respectively, raton laveur and ratão-lavadeiro. In some cases, the "washing" descriptor is applied only to the common raccoon species, such as with the French raton laveur. In contrast, the crab-eating raccoon is "little crab-catching rat" (raton crabier) and "crab-eating pre-dog" (Procyon cancrivorous) in French and Latin, respectively.
Dormaalocyon
Pouncing lions, fish-swallowing seals, and even your bone-chewing family dog can all trace their roots back to a small, tree-dwelling ancestor. Bones unearthed from a 55-million-year-old fossil trove have revealed a diminutive creature at or near the root of today's formidable lineage of carnivorous mammals.
Paleontologist Floréal Solé of the Royal Belgian Institute of Natural Sciences and a team of colleagues recently described more than 250 new teeth, jaw, and ankle bone specimens of Dormaalocyon latouri, named for the Belgian locality of Dormaal where the fossil was first found in a site long famed for early Eocene epoch remains.
Fossilized jaw bones and teeth, including baby teeth, provide valuable evidence of the ancient animal's taste for flesh. According to Solé, Dormaalocyon is the most primitive known member of the carnivoraforms group. That group is represented by today's 280-plus species of living carnivorous mammals, the order Carnivora, which includes lions, seals, bears, cats, dogs, and others—all of which count this creature as their ancestor.
Three other carnivorous mammal families (Oxyaenidae, Hyaenodontidae, and Viverravidae) also existed back in the Paleogene but have since died out, Solé said. Chronologically, Dormaalocyon is not the oldest carnivoraform ever found: Another arboreal creature called Uintacyon is one million years older, although it is thought to be farther from the root of the group.
A Cross Between a Squirrel and a Small Cougar
Dormaalocyon, which may have looked a bit like a cross between a squirrel and a small cougar, shows oral features with important adaptations to a meaty diet. The one- to two-pound (half- to one-kilogram) mammal likely consumed insects and other animals smaller than itself. (Related: "Newly Discovered Carnivore Looks Like Teddy Bear.")
Dormaalocyon lived during the Paleocene-Eocene boundary epoch, and fossils from this period have been extremely hard to come by, said Gregg Gunnell, director of the Division of Fossil Primates at Duke University's Lemur Center, who was unaffiliated with the research.
"It's really a matter of just finding the right rocks, and there aren't that many," he explained. "If you don't have that little slice of time preserved in the right rocks, from maybe 55.8 to 56 million years ago, then you are out of luck. So this animal provides a limited sort of window in time at the Paleocene-Eocene boundary, and that lasted for only maybe a couple of hundred thousand years."
Dormaal is one of the very few places in Europe that fossils have been found from the period, Gunnell added. In North America such fossils have been found in just a couple of Wyoming locations, and in Asia they've been found in just a single spot in China, he said. (Related: "Fossil Reveals Long-Lived Mammal Group's Secret.") The scant evidence makes it impossible to determine if the carnivores arose in Asia and spread westward, or had a different geographical origin.
"Despite all the looking, that's all we've ever found," said Gunnell. "It's like trying to put together a 500-piece puzzle when you only have three pieces and trying to see what the picture is going to look like. So this fossil is quite rare, a teeny glimpse on a world that we don't know much about."
Hot, Forested Earth
The Paleocene-Eocene Thermal Maximum (PETM) was a period of evolution, extreme global warming, and low sea levels that opened a land connection between Europe, North America, and Asia. That land bridge allowed mammals, primates, rodents, and other vertebrates to spread during this time. (Related: "World Without Ice.") The period ended rather abruptly during the early Eocene, leaving species to further evolve endemically in their continental locations when waters rose.
"This fossil is from about the same time that we're starting to see real primates showing up for the first time, so it appears to be a part of that radiation of modern animals that shows up at the Paleocene-Eocene boundary," Gunnell said.
Dense forests predominated across the Northern Hemisphere, perhaps prompting Dormaalcyon's adaptation to life in the trees as evidenced by its ankle bones.
"Being arboreal, it probably fits in nicely with the arboreal primates that are showing up at that same time, part of a very early Eocene fauna that spread quickly across the northern continents," Gunnell explained.
The Paleocene began after the Cretaceous-Tertiary mass extinction about 65 million years ago and featured a key period of evolutionary expansion when mammals and birds spread across the globe to occupy ecological niches vacated by recently vanished dinosaurs and larger reptiles. It lasted until about 55 million years ago and was followed by the Eocene, which lasted roughly from 55 million to 33.9 million years ago. (Related: "Dino-era Mammal the 'Jurassic Mother' of Us All?")
"Because of the diversity of the carnivoraforms during the earliest part of the Eocene, we think that they diversified during the late Paleocene," Solé said, noting that his group is also at work in a new locality in Europe where other late Paleocene species may be found. It's his hope that future finds from the period can help paleontologists determine whether the placental mammals adopted a carnivorous lifestyle just once, or several times within the different and now extinct groups.
"This question is important for understanding the evolution of mammals after the disappearance of the majority of the dinosaurs," said Solé.
L'âge des mammifères
Mammals did not emerge from the extinction event unscathed. Before the asteroid strike, Lyson says, the largest mammals were about the size of a raccoon. Immediately after, the biggest mammals were about rat-sized. But in a world without towering dinosaurs, new opportunities opened for mammals.
“Within 100,000 years after the extinction, we have a different type of raccoon-size mammals,” Lyson says, with additional fossils from Corral Bluffs revealing an increase size over time. By the 300,000-year mark, the biggest mammals were about the size of large beavers, and those that lived 700,000 years after the impact could weigh over a hundred pounds, such as Ectoconus ditrigonus, a herbivore unlike any mammal alive today. “This is a hundred-fold increase in body size compared to the mammals that survived the extinction,” Lyson says. Mammals wouldn’t go through this sort of rapid growth again for another 30 million years.
The question facing paleontologists is what spurred this rapid growth. A combination of factors were likely at play. Not only did the dinosaurs that munched mammals disappear, but a warming global climate changed the makeup of forests and allowed for the evolution of new plants. Legumes—energy-rich plants and the ancestors of bean—evolved for the first time. The botanical changes may have helped provide the fuel for mammalian growth, Lyson says, with climate, plants and mammals all tied together in a story of recovery from one of the world’s most devastating mass extinctions.
“For the first time, we are able to link changes in plants and animals together, and more importantly, we are able to place all of these changes in a high-resolution temporal framework,” Lyson says.
Pourquoi les mammifères ont-ils survécu?
Had the non-avian dinosaurs not been wiped out 65 million years ago, our species would probably never existed. The mass extinction that struck at the end of the Cretaceous was one of the major events in earth's history that greatly affected evolution by pruning back the tree of life, and it was in the wake of the extinction that mammals became the dominant vertebrates on land. What scientists have been trying to figure out, however, is why mammals survived while the dinosaurs perished.
Marcher ou respirer?
Fig. 6. Carrier's constraint. (A, B) Reptiles such as lizards can only breathe or walk, but not both: air is shunted from lung to lung as the torso swings laterally during a stride. (C, D) Modern mammals, such as this greyhound, pump air in and out of their lungs as they run because they have constrained lateral movements of the rib cage, and the concave-convex bowing of the backbone as the limbs come together (C) and spread (D) during the stride pumps air out (C) and in (D). (Image modified from work of David Carrier.)
Fourrure et moustaches
The first solid evidence for endothermy in Triassic synapsids came from detailed studies of therocephalians and cynodonts. Watson (1913), in describing the skull and endocranium of the Middle Triassic cynodont Diademodon, noted its mammalian-type brain, ethmoturbinals in the nasal cavity, and concluded (p. 228): “Many of the differences between a mammal and a reptile – the soft skin, the increased body-temperature, the hair and all it implies, the more perfect joints in the limbs – are directly connected with increased activity and precision of movement, and these in turn are dependent on cerebellar improvement. The importance of the Diademodon brain, ear, and nose lies in the evidence which they afford that this change was actually taking place in the Therapsids, and that it is to all appearances a very gradual one and may to a large extent have preceded the development of a mammalian structure.”
He later (Watson, 1931) interpreted the numerous fine pits on the snouts of Late Permian and Triassic synapsids (therocephalians and cynodonts) as evidence for vibrissae, sensory whiskers, and hence for hair more generally. He noted the very mammalian-like limbs, vertebral column, brain, and presumed sensory organs of the snout in the Early Triassic therocephalian Ericiolacerta, and wrote (Watson, 1931, p. 1200): “The general outer surface of the maxilla of Ericiolacerta is exceptionally richly provided with small foramina, whose existence goes to show that the skin of the face was sensory or required a large blood-supply, a condition only understandable if it were muscular. Thus any possible interpretation of these foramina in the maxilla of Ericiolacerta leads to the conclusion that the animals' skin was mammal-like, in that it possessed specially developed sense-organs (?hairs) and was movable and muscular.” Such heavily perforated snouts have been noted in many other Triassic cynodonts (Fig. 5A).
Brink (1957, p. 86) expanded on Watson's evidence, noting that “[v]ibrissae are obviously specialized hair [so] that ordinary hair must have been present even in earlier forms.” He suggested hair had evolved to shield these synapsids from absorbing too much heat from the sun, appropriate perhaps during a time that was as hot and arid as the earliest Triassic, but also to retain heat (insulation) at cooler times. Further, Brink (1957, p. 87) speculated that early synapsids had sweat glands associated with their hair, as well as mammary glands, which are usually interpreted as modified sweat glands.
The story of the early origins of synapsid hair has taken an interesting twist more recently. Smith and Botha-Brink (2011) and Bajdek et al. (2016) independently reported fossil finds of possible hairs in coprolites from South Africa and Russia respectively. These finds suggest the origin of hair during the Late Permian. In future, it will be helpful to determine whether specimens such as these show conclusive evidence of hair characters, such as melanosomes embedded in the structures. Melanosomes, the capsules that contain the pigment melanin in modern birds and mammals, could also give suggestions of the colours of the hair of early synapsids.
A recent study has suggested a much later origin for hair. In their investigation of synapsid brains, Benoit et al. (2017) argued that the presence of a true infraorbital canal in derived cynodonts suggests that they had a mobile rhinarium and whiskers. These authors used evidence of pleiotropic genetic linkage, through the homeogene Msx2 in mice, between the ossification of the parietal fontanelle and development of the cerebellum with the development of mammary glands and hair, to suggest that the first two characters seen in derived cynodonts confirms the presence of mammary glands and hair at least by that point in the Middle Triassic, before the origin of mammaliaforms. Some current researchers are less convinced by Watson's arguments about snout vessels and vibrissae and indicate that hair evolved in the early Late Triassic (Botha-Brink et al., 2018). However, the evidence from cranial nerves provides a conservative estimate, and the coprolites give tantalising evidence for the origin of hair in the Late Permian.
Les cynodontes après l'extinction
The most catastrophic crisis on record—the Permo-Triassic mass extinction event (PTME), some 252 million years (Myr) ago—challenged the surviving organisms with extensive global warming, acid rain and forest loss. The response of terrestrial vertebrates to the PTME is the focus of novel enquiry. Some groups (temnospondyl amphibians; therocephalian synapsids; procolophonid parareptiles) passed through the PTME at low diversity and expanded in the Triassic. Others (anomodont therapsids) were diverse and abundant in the Late Permian, went through a bottleneck at the PTME and recovered in the Triassic.
Cynodont therapsids exemplify a group of land vertebrates that survived the PTME and diversified extensively in the Triassic. In addition, they offer an excellent model for studying clade diversification leading up to the origin of a successful and iconic vertebrate radiation—the mammals. Cynodonts gave rise to the mammals in the Jurassic. Their skeletal anatomy documents in exquisite detail major skeletal changes in the braincase, lower jaw, teeth and limbs that foreshadow the mammalian ground plan.
Évolution des mammifères
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Biarmosuchia
The Biarmosuchia were the most primitive and pelycosaur-like of the therapsids.
Dinocephalians
Dinocephalians ("terrible heads") included both carnivores and herbivores. They were large; Anteosaurus was up to 6 m (20 ft) long. Some of the carnivores had semi-erect hindlimbs, but all dinocephalians had sprawling forelimbs. In many ways they were very primitive therapsids; for example, they had no secondary palate and their jaws were rather "reptilian".
Anomodonts
The anomodonts ("anomalous teeth") were among the most successful of the herbivorous therapsids — one sub-group, the dicynodonts, survived almost to the end of the Triassic. But anomodonts were very different from modern herbivorous mammals, as their only teeth were a pair of fangs in the upper jaw and it is generally agreed that they had beaks like those of birds or ceratopsians.
Theriodonts
The theriodonts ("beast teeth") and their descendants had jaw joints in which the lower jaw's articular bone tightly gripped the skull's very small quadrate bone. This allowed a much wider gape, and one group, the carnivorous gorgonopsians ("gorgon faces"), took advantage of this to develop "sabre teeth". But the theriodont's jaw hinge had a longer term significance — the much reduced size of the quadrate bone was an important step in the development of the mammalian jaw joint and middle ear.
The gorgonopsians still had some primitive features: no bony secondary palate (but other bones in the right places to perform the same functions); sprawling forelimbs; hindlimbs that could operate in both sprawling and erect postures. But the therocephalians ("beast heads"), which appear to have arisen at about the same time as the gorgonopsians, had additional mammal-like features, e.g. their finger and toe bones had the same number of phalanges (segments) as in early mammals (and the same number that primates have, including humans).
Cynodonts
The cynodonts, a theriodont group that also arose in the late Permian, include the ancestors of all mammals. Cynodonts' mammal-like features include further reduction in the number of bones in the lower jaw, a secondary bony palate, cheek teeth with a complex pattern in the crowns, and a brain which filled the endocranial cavity.
Multi-chambered burrows have been found, containing as many as 20 skeletons of the Early Triassic cynodont Trirachodon; the animals are thought to have been drowned by a flash flood. The extensive shared burrows indicate that these animals were capable of complex social behaviors.
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The origin and early radiation of the therapsid mammal‐like reptiles: a palaeobiological hypothesis
The replacement of the basal synapsid pelycosaurs by the more ‘mammal‐like’ therapsids in the Permian was an important event in the history of tetrapods because it initiated the eventual transition to the mammals. It is also an example of taxon replacement in the fossil record that is unusually amenable to explanation, based on a combination of analysis of the biological significance of the inferred character changes, with the stratigraphic, palaeogeographic and palaeoecological circumstances of the time. An hypothesis is presented in which the origin of the therapsids resulted from a correlated progression of character evolution leading to higher levels of metabolic activity and homeostatic regulation of the body. It was a response to the availability of a seasonally arid, savanna‐like biome. The subsequent explosive radiation of therapsids was associated with habitat expansion made possible by the Mid‐Permian development of geographical continuity between that biome and the temperate biomes. The final extinction of the pelycosaurs was a case of incumbent replacement by the new therapsid lineages.
The tempo of the origin and early diversification of the therapsids
The hypothetical ancestral therapsid has been reconstructed as an actively hunting predator, of medium body size, which also proved to have had the potential to give rise to a range of different kinds of carnivores and herbivores. The earliest appearance of possible therapsids in the fossil record is the Russian early Kazanian (Fig. 3), dated approximately 267 Ma (Lucas, 2004). Unfortunately they are very poorly preserved and fragmentary (Efremov, 1954; Chudinov, 1983), leaving their true identification in doubt. However, by the later Kazanian‐early Tatarian of Russia, about 265 Ma, at least seven therapsid lineages are known to have existed (Ivakhnenko, 2003a). Carnivores are represented by biarmosuchians, basal gorgonopsians, and anteosaurid (brithopodid) dinocephalians. There were also the large, herbivorous estemmenosuchids, and three kinds of small herbivores, basal anomodontians and the as yet little known niaftasuchids and nikkasaurids. In the contemporary South African record there are also the more progressive, larger carnivorous therocephalians and herbivorous dicynodont anomodontians (Rubidge, 1995).
Les anciens mammifères vivaient comme des reptiles
Pioneering analysis of 200 million-year-old teeth belonging to the earliest mammals suggests they functioned like their cold-blooded counterparts — reptiles, leading less active but much longer lives.
(...) Fossils of teeth, the size of a pinhead, from two of the earliest mammals, Morganucodon and Kuehneotherium, were scanned for the first time using powerful X-rays, shedding new light on the lifespan and evolution of these small mammals, which roamed the earth alongside early dinosaurs and were believed to be warm-blooded by many scientists. This allowed the team to study growth rings in their tooth sockets, deposited every year like tree rings, which could be counted to tell us how long these animals lived. The results indicated a maximum lifespan of up to 14 years – much older than their similarly sized furry successors such as mice and shrews, which tend to only survive a year or two in the wild.
(...) “By contrast, our findings clearly show that, although they had bigger brains and more advanced behaviour, they didn’t live fast and die young but led a slower-paced, longer life akin to those of small reptiles, like lizards.”
Premiers synapsides
Although we thought we were studying only one animal, Asaphestera intermedia, one of our major findings was recognizing that what previous paleontologists had thought was a single animal was actually a composite of multiple fossils of at least three very different animals! We could only be certain of two of them: a new reptile we named Steenerpeton silvae and an early synapsid, Asaphestera platyris, with evidence of a single temporal opening in the skull.
(...) Asaphestera platyris provides the oldest evidence of mammal-like reptiles in the fossil record, establishing a firm date for their diversification around 315 million years ago.
Asaphestera: the earliest amniote? …No Mann et al. 2020 mistakenly reassessed their ‘microsaur’, Asaphestera platyris (Fig. 1), as at ‘the earliest synapsid’. The LRT nests this taxon as a microsaur after demonstrating interpretation and reconstruction errors. Unambiguous? No. Just because they say so, does not mean it is true. (...) Mann et al. 2020 mistakenly reassessed their microsaur, Asaphestera platyris, as a synapsid. The LRT nests it as a microsaur close to Kirktonecta, a taxon essentially overlooked by the authors. Nearly coeval Archaeothyris remains the earliest known synapsid, but several synapsids are more primitive, indicating an earlier radiation. So, they’re out there somewhere! Mann et al. did not find them…yet.
Protoclepsydrops is an extinct genus of early synapsids, found in Joggins, Nova Scotia. The name means 'first Clepsydrops', and refers to it being the predecessor of the other early synapsid Clepsydrops. Like Archaeothyris, Protoclepsydrops resembled a modern lizard in superficial appearance. However, Protoclepsydrops had primitive vertebrae with tiny neural processes typical of their amniote ancestors. Protoclepsydrops is known from a few vertebrae and some humeri. Its skeletal remains indicate that it may have been more closely related to synapsids than to sauropsids, making it a possible stem-mammal. If so, it is the oldest synapsid known, though its status is unconfirmed because its remains are too fragmentary. Protoclepsydrops lived slightly earlier than Archaeothyris.
Archaeothyris is an extinct genus of ophiacodontid synapsid that lived during the Late Carboniferous and is known from Nova Scotia. Dated to 306 million years ago, Archaeothyris, along with a more poorly known synapsid called Echinerpeton, are the oldest undisputed synapsids known. The name means ancient window (Greek), and refers to the opening in the skull, the temporal fenestra, which indicates this is an early synapsid.
Archaeothyris was also more advanced than the early sauropsids, having strong jaws that could open wider than those of the early reptiles. While its sharp teeth were all of the same size & shape, it did possess a pair of enlarged canines, suggesting that it was a carnivore.
Archaeothyris' legs were articulated laterally at its pelvis and shoulders, which gave it a sprawling stance. The first toe is smaller than the second.
Species: A. florensis (type).
Type: Carnivore/Insectivore.
Size: 50 centimetres long.
Echinerpeton is an extinct genus of synapsid, including the single species Echinerpeton intermedium from the Late Carboniferous of Nova Scotia, Canada. The name means 'spiny lizard' (Greek). Along with its contemporary Archaeothyris, Echinerpeton is the oldest known synapsid, having lived around 308 million years ago. It is known from six small, fragmentary fossils, which were found in an outcrop of the Morien Group near the town of Florence. The most complete specimen preserves articulated vertebrae with high neural spines, indicating that Echinerpeton was a sail-backed synapsid like the better known Dimetrodon, Sphenacodon, and Edaphosaurus. However, the relationship of Echinerpeton to these other forms is unclear, and its phylogenetic placement among basal synapsids remains uncertain.
(...) The teeth of both the upper and lower jaws are small and cone-shaped, some having slightly serrated edges, and are only differentiated by slight differences in length (some other synapsids have teeth that vary greatly and shape across their jaws). The three forward-most dentary teeth are angled slightly outward as in more derived synapsids such as Dimetrodon and Sphenacodon. Several features, including straight-margined maxillae and simple conical teeth, are also seen in the earliest reptiles.
(...) The most prominent feature of the vertebrae of Echinerpeton are their tall neural spines, which can be up to seven times higher than they are wide. They are similar in proportion to the spines of Sphenacodon, although Echinerpeton is considerably smaller in overall size. The neural spines of the holotype are thinnest at their tips, suggesting that MCZ 4090 may have been an immature individual with poorly ossified bones.
Fosse temporale
Synapsids evolved from basal amniotes and are one of the two major groups of amniotes, the other being the sauropsids, the group that includes reptiles and birds. The distinctive temporal fenestra developed in the ancestral synapsid about 312 million years ago, during the Late Carboniferous period.
(...) Synapsids evolved a temporal fenestra behind each eye orbit on the lateral surface of the skull. It may have provided new attachment sites for jaw muscles. A similar development took place in the diapsids, which evolved two rather than one opening behind each eye. Originally, the openings in the skull left the inner cranium covered only by the jaw muscles, but in higher therapsids and mammals, the sphenoid bone has expanded to close the opening. This has left the lower margin of the opening as an arch extending from the lower edges of the braincase.
Les fosses temporales, ou fenêtres temporales, sont des ouvertures présentes dans les crânes de certains amniotes. Elles allègent considérablement le crâne et permettent aussi l'insertion de muscles qui actionnent la mandibule (la mâchoire inférieure). La contribution des différents os à la bordure de ces fenêtres varie selon les groupes considérés.
Différents termes servent à classer les crânes d'amniotes, selon le nombre et la position des fenêtres temporales : anapside, synapside, euryapside et diapside.
(...) Chez certains amniotes, le crâne est percé d'une fenêtre temporale inférieure : il s'agit d'une configuration synapside.
yes, there is an anatomical homologue of temporal fenestra in humans (and to the best of my knowledge, in all the extant mammals), and no, it's not the zygomatic arch (...) The temporal fenestra in mammals is reduced to a rather small opening (about 1x1 cm in humans) situated close to the fissure between the posterior part of maxilla (tuber maxillae) and lateral parts of the sphenoid bone (processus pterygoideus). The superior end of this "fissure" is actually the lateral opening of the pterygopalatine fossa and this opening is (the remnant of) the synapsid temporal fenestra.
If you take a look at any depiction of a "phylotypic" synapsid skull, you will notice that the temporal fenestra is situated right behind the postorbital (and partially jugal) bone. In humans, the postorbital bone became known as the frontal process of the zygomatic bone, and right behind it you can clearly see the opening of the pterygopalatine fossa, i.e. temporal fossa of the synapsides."
In human anatomy, the pterygopalatine fossa (sphenopalatine fossa) is a fossa in the skull. A human skull contains two pterygopalatine fossae—one on the left side, and another on the right side. Each fossa is a cone-shaped paired depression deep to the infratemporal fossa and posterior to the maxilla on each side of the skull, located between the pterygoid process and the maxillary tuberosity close to the apex of the orbit. It is the indented area medial to the pterygomaxillary fissure leading into the sphenopalatine foramen. It communicates with the nasal and oral cavities, infratemporal fossa, orbit, pharynx, and middle cranial fossa through eight foramina.[
(...) The pterygopalatine fossa contains
-the pterygopalatine ganglion suspended by nerve roots from the maxillary nerve
-the terminal third of the maxillary artery
-the maxillary nerve (CN V2, the second division of the trigeminal nerve), with which is the nerve of the pterygoid canal, a combination of the greater petrosal nerve (preganglionic parasympathetic) and the deep petrosal nerve (postganglionic sympathetic). To obtain block anesthesia of the entire second division of the trigeminal nerve, an intraoral injection can be administered into this area.
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