Sabtu, 31 Maret 2012

SARCOSUCHUS

     Sarcosuchus (flesh crocodile), and commonly called "SuperCroc", is an extinct genus of crocodyliform and distant relative of the crocodile that lived 112 million years ago. It dates from the early Cretaceous Period of what is now Africa and is one of the largest giant crocodile-like reptiles that ever lived. It was almost twice as long as the modern saltwater crocodile and weighed approximately 8 to 10 tonnes.

     Until recently, all that was known of the genus was a few fossilised teeth and armour scutes, which were discovered in the Sahara Desert by the French paleontologist Albert-FĂ©lix de Lapparent, in the 1940s or 1950s. He called it the "Aoulef crocodile". However, in 1997 and 2000, American paleontologist Paul Sereno discovered half a dozen new specimens, hncluding one with about half the skeleton intact and most of the spine. All of the other giant crocodiles are known only from a few partial skulls, so which is actually the biggest is an open question.

     When fully mature, Sarcosuchus is believed to have been as long as a city bus (11.2–12.2 metres or 37–40 ft) and weighed up to 8 tonnes (8.75 tons).[1] The largest living crocodilian, the saltwater crocodile, is less than two-thirds of that length (6.3 meters or 20.6 ft is the longest confirmed individual) and a small fraction of the weight (1,200 kg, or 1.3 tons).

     The very largest Sarcosuchus is believed to have been the oldest. Osteoderm growth rings taken from an 80% grown individual (based on comparison to largest individual found) suggest that Sarcosuchus kept growing throughout its entire 50–60 year average life span. Modern crocodiles grow at a rapid rate, reaching their adult size in about a decade, then growing more slowly afterward.

     Its skull alone was as big as a human adult (1.78 m, or 5 ft 10 inches). The upper jaw overlapped the lower jaw, creating an overbite. The jaws were relatively narrow (especially in juveniles). The snout comprises about 75% of the skull's length.

     The huge jaw contained 132 thick teeth; Larsson said they were like "railroad spikes".[citation needed] Instead of being narrow and adapted for slashing like the teeth of some land-dwelling carnivores, the teeth were conical, adapted for grabbing and holding, more like those of true crocodilians, which normally dispatch prey simply by holding them underwater until they drown. Sarcosuchus could probably exert a force of 80 kN (18,000 lbf) with its jaw, making it very unlikely that prey could escape.

     It had a row of bony plates or osteoderms, running down its back, the largest of which were 1 m (3 ft) long. The scutes served as armour and may have helped support its great mass, but also restricted its flexibility.[citation needed]

     Sarcosuchus also had a strange depression at the end of its snout. Called a bulla, it has been compared to the ghara seen in gharials. Unlike the ghara, though, the bulla is present in all Sarcosuchus skulls that have been found so far. This suggests it was not a sexually selected characteristic; only the male gharial has a ghara. The purpose of this structure remains enigmatic. Sereno and others asked various reptile researchers what their thoughts on this bulla were. Opinions ranged from it being an olfactory enhancer to being connected to a vocalization device.

     The eye sockets of Sarcosuchus rotated upwards and were somewhat telescoped. This suggests that the animal probably spent most of its time with the majority of its body submerged, watching the shore for prey.

     It seems likely that it ate the large fish and turtles of the Cretaceous. As the overhanging jaw and stout teeth are designed for grabbing and crushing, its primary prey may have been large animals and smaller dinosaurs, which it ambushed, dragged into the water, crushed, drowned and then tore apart.

     It may have come into conflict with Suchomimus, an 11 m (36 ft) theropod dinosaur with a gharial-like snout, whose fossils were found in the same geological formation as Sarcosuchus. According to Sereno,[citation needed] "because the ancient animal was so large, it could easily handle huge dinosaurs, including the massive long-necked, small-headed sauropods that were common in that African region".

     Other crocodilian biologists are skeptical of the animal's "giant killing" capabilities.[citation needed] The long, thin snout of Sarcosuchus was very similar to the thin snouts of the modern gharial, the false gharial and the slender-snouted crocodile, all of which are nearly exclusive fish-eaters and incapable of tackling large prey. This can be contrasted to both the modern Nile crocodile and the extinct Deinosuchus, both of which exhibit very broad, heavy skulls, suitable for dealing with large prey. This, coupled with the abundance of large, lobe-finned fish in its environment, leads many to suggest that, far from being a dinosaur killer, Sarcosuchus was simply a large piscivore, a scaled-up version of the modern gharial.

     However, while the snout of juvenile Sarcosuchus strongly resembled modern narrow-snouted crocodiles in width, it expands dramatically in mature individuals. While still comparatively narrower than the snout of a Nile crocodile, the snout is still much wider than the snouts of crocodilians like the gharial. In addition, the teeth do not interlock,[citation needed] like those of mostly piscivorous crocodilians. This suggests that, like the Nile crocodile, it may have complemented a primarily fish diet with terrestrial animals, at least upon maturity.[citation needed]

     It is pertinent to note, though, that the lobe-finned fish that shared the waters with Sarcosuchus were often in excess of 1.8 m (6 ft) long and 90 kg (200 lb) in weight.[citation needed] This raises the possibility of those adaptations, which seem to indicate large or moderate-sized terrestrial prey, may instead have been adaptations for dealing with exceptionally large fish (many species of which possessed a layer of osteoderms, for protection).

     110 million years ago, in the Early Cretaceous, the Sahara was still a great tropical plain, dotted with lakes and crossed by rivers and streams that were lined with vegetation. Based on the number of fossils discovered, the aquatic Sarcosuchus was probably plentiful in these warm, shallow, freshwater habitats.

     Unlike modern true crocodiles, which are very similar in size and shape to one another and tend to live in different areas; Sarcosuchus was just one of many Crocodyliformes, of different sizes and shapes, all living in the same area. Four other species of extinct Crocodyliformes were also discovered in the same rock formation along with the Sarcosuchus, including a dwarf crocodile with a tiny, 8 cm (3 in) long skull. They filled a diverse variety of ecological niches, instead of competing with each other for resources.



     Giant crocodiles seem to be a good example of convergence because, according to Schwimmer, "the idea of really big crocs is a repeat theme in evolution". This may in part be due to body design and in part due to environment: The armoured plates of the back can provide structural support to a massive body), and water can buoy up their massive bodies.

     A study of another giant crocodilian, Deinosuchus, indicated that it grew at about the same rate as modern crocodiles, up to 0.5 m (1.5 ft) per year. It was larger, because it kept growing, reaching full adulthood in 35 years, instead of 10. While there is a genetic component, growing that large also requires a rich diet. All the different giant crocodiles must have lived in near-perfect environments, with vast areas of warm, shallow water and abundant prey.

     Deinosuchus, which was from the Late Cretaceous of what is now North America, is also a good example of a giant crocodile that is only distantly related to Sarcosuchus. Deinosuchus, which is only known from skulls, had a smaller skull than Sarcosuchus,[citation needed] but a broad snout, like an alligator. This means that the skull of the Deinosuchus is probably a smaller portion of its total body length than the skull of the long-snouted Sarcosuchus, so its total size may be as large, or even larger.[citation needed] Other rivals in size of Sarcosuchus are Purussaurus from the Miocene of what is now Peru and Brazil, and Rhamphosuchus from the Miocene and Pliocene of what is now India. However, their fossils are less complete.

Jumat, 23 Maret 2012

MAMMOTH



     A mammoth is any species of the extinct genus Mammuthus, proboscideans commonly equipped with long, curved tusks and, in northern species, a covering of long hair. They lived from the Pliocene epoch from around 5 million years ago, into the Holocene at about 4,500 years ago. And were members of the family Elephantidae, which contains, along with mammoths, the two genera of modern elephants and their ancestors.

      Like their modern relatives, mammoths were quite large. The largest known species reached heights in the region of 4 m (13 ft) at the shoulder and weights up to 8 tonnes (9 short tons), while exceptionally large males may have exceeded 12 tonnes (13 short tons). However, most species of mammoth were only about as large as a modern Asian elephant. Based on studies of their close relatives, the modern elephants, mammoths probably had a gestation period of 22 months, resulting in a single calf being born. Their social structure was probably the same as that of African and Asian elephants, with females living in herds headed by a matriarch, whilst bulls lived solitary lives or formed loose groups after sexual maturity.

     The woolly mammoth was the last species of the genus. Most populations of the woolly mammoth in North America and Eurasia, as well all the Columbian mammoths in North America, died out around the time of the last glacial retreat, as part of a mass extinction of megafauna in northern Eurasia and the Americas. Until recently, the last woolly mammoths were generally assumed to have vanished from Europe and southern Siberia about 12000 years ago, but new findings show some were still present there about 10,000 years ago. Slightly later, the woolly mammoths also disappeared from continental northern Siberia. A small population survived on St. Paul Island, Alaska, up until 3750 BCE, and the small mammoths of Wrangel Island survived until 1650 BCE. Recent research of sediments in Alaska indicates mammoths survived on the American mainland until 10,000 years ago.

     A definitive explanation for their mass extinction has yet to be agreed upon. The warming trend (Holocene) that occurred 12,000 years ago, accompanied by a glacial retreat and rising sea levels, has been suggested as a contributing factor. Forests replaced open woodlands and grasslands across the continent. The available habitat may have been reduced for some megafaunal species, such as the mammoth. However, such climate changes were nothing new; numerous very similar warming episodes had occurred previously within the ice age of the last several million years without producing comparable megafaunal extinctions, so climate alone is unlikely to have played a decisive role. The spread of advanced human hunters through northern Eurasia and the Americas around the time of the extinctions was a new development, and thus might have contributed significantly.

     Whether the general mammoth population died out for climatic reasons or due to overhunting by humans is controversial. Another theory suggests mammoths may have fallen victim to an infectious disease. A combination of climate change and hunting by humans may be a possible explanation for their extinction. Homo erectus is known to have consumed mammoth meat as early as 1.8 million years ago. A site in Ukraine suggests Neanderthals built dwellings using mammoth bones.

     However, the American Institute of Biological Sciences also notes bones of dead elephants, left on the ground and subsequently trampled by other elephants, tend to bear marks resembling butchery marks, which have previously been misinterpreted as such by archaeologists.

     Dwarfing occurred with the pygmy mammoth on the outer Channel Islands of California, but at an earlier period. Those animals were very likely killed by early Paleo-Native Americans, and habitat loss caused by a rising sea level that split Santa Rosae into the outer Channel Islands.

 

Sabtu, 17 Maret 2012

Argentavis


      Argentavis magnificens is the largest flying bird ever discovered. This bird, sometimes called the Giant Teratorn, is an extinct species known from three sites from the late Miocene (6 million years before present) of central and northwestern Argentina, where a good sample of fossils have been obtained.




 
     The humerus (upper arm bone) of Argentavis is somewhat damaged. Even so, it allows a fairly accurate estimate of its length in life, which was only slightly shorter than an entire human arm. The species apparently had stout, strong legs and large feet which enabled it to walk with ease. The bill was large, rather slender, and had a hooked tip with a wide gape.

Physical characteristics 
  
Currently accepted estimates:
  • Wingspan: approximately 7 m (23 ft)
  • Wing area: 8.11 m² (87.3 ft²)
  • Wing loading: 84.6 N/m²
  • Body Length: 1.26 m (4.1 ft)
  • Height: 1.7–2 m (5.6–6.6 ft)
  • Mass: 70-78 kg (154-171.6 lb)




For comparison, the living bird with the largest wingspan is the Wandering Albatross, at 3.65 m (12.0 ft). Since A. magnificens is known to have been a land bird, another good point of comparison is the Andean Condor, which is not too distantly related to Argentavis. This bird is among the largest land birds, with a wingspan of up to 3.2 m (10 ft) and weighing up to 15 kg (33 lb).
The ability to fly is not a simple question of weight ratios, except in extreme cases. Size and structure of the wing must also be taken into account. As a rule of thumb, a wing loading of 25 kg/m² is considered the limit for avian flight.
The heaviest extant flying birds are known to weigh up to 21 kg (46 lb) (there are several contenders, among which are the European Great Bustard and the African Kori Bustard). A Mute Swan, which may have briefly lost the power of flight due to its extreme weight, was found to have weighed 23 kg (51 lb). The Sarus Crane is the tallest flying bird alive, at up to 2 m (6.6 ft) high, standing nearly as high as Argentavis due to its long legs and neck.
The largest known flying creatures are a group of pterosaurs named azhdarchids, extinct flying reptiles that existed during the age of the dinosaurs and died out at the end of the Cretaceous. Estimations of the wingspan of the largest species like Quetzalcoatlus and Hatzegopteryx exceeds 10 m (33 ft), with less conservative estimates being 12 m (40 ft) or more.

Ecology

As with nearly all extinct species, not much can be known about the Giant Teratorn's behaviour. From the size and structure of its wings it is inferred that A. magnificens flew mainly by soaring, using flapping flight only during short periods. It is probable that it used thermal currents as well. It has been estimated that the minimal velocity for the wing of A. magnificens is about 11 m/s or 40 km/h. Especially for takeoff, it would have depended on the wind, as although its legs were strong enough to provide it with a running or jumping start, the wings were simply too long to flap effectively until the bird was some meters off the ground. However, skeletal evidence suggests that its breast muscles were not powerful enough for wing flapping for extended periods. Argentavis may have used mountain slopes and headwinds to take off, and probably could manage to do so from even gently sloping terrain with little effort. It may have flown and lived much like the modern Andean condor, scanning large areas of land from aloft for carrion. The climate of the Andean foothills in Argentina during the late Miocene was warmer and drier than today, which would have further aided the bird in staying aloft atop thermal updrafts.
This species seems less aerodynamically suited for predation than its relatives. It probably preferred to scavenge for carrion, and it is possible that it habitually chased metatherian carnivores such as Thylacosmilidae from their kills. Unlike extant condors and vultures, the other species of teratorns generally had long, eagle-like beaks and are believed to have been active predators, being less ponderous than Argentavis. When hunting actively, A. magnificens would probably have swooped from high above onto their prey, which they usually would have been able to grab, kill, and swallow without landing. Skull structure suggests that it ate most of its prey whole rather than tearing off pieces of flesh.
Argentavis' territories measured probably more than 500 square km, which the birds screened for food, possibly utilizing a generally north-south direction to avoid being slowed by adverse winds. Comparison with extant birds suggests it laid one or two eggs with a mass of somewhat over 1 kg – somewhat smaller than an ostrich egg – every two years. Climate considerations make it likely that the birds incubated over the winter, mates exchanging duties of incubating and procuring food every few days, and that the young were independent after some 16 months, but not fully mature until aged about a dozen years. Mortality must have been very low; to maintain a viable population less than about 2% of birds may have died each year. Of course, Argentavis suffered hardly any predation, and mortality was mainly from old age, accidents and disease.
It appears likely, therefore, that the average and maximum age reached by these creatures was fairly large – possibly some 50–100 years; compare with ostrich at perhaps 60–70, and parrots at perhaps 80–120 at most – if they were to mature and reproduce and replace members that had died 'young' – for whatever reason. Presently, no direct evidence is available for this suggestion; however, K-strategy lifestyle correlates with greater average and maximum age.

Sightings Argentavis

Kamis, 08 Maret 2012

Lernaean Hydra

     In Greek mythology, the Lernaean Hydra was an ancient nameless serpent-like chthonic water beast, with reptilian traits, (as its name evinces) that possessed many heads — the poets mention more heads than the vase-painters could paint, and for each head cut off it grew two more — and poisonous breath so virulent even her tracks were deadly. The Hydra of Lerna was killed by Heracles as the second of his Twelve Labours. Its lair was the lake of Lerna in the Argolid, though archaeology has borne out the myth that the sacred site was older even than the Mycenaean city of Argos since Lerna was the site of the myth of the Danaids. Beneath the waters was an entrance to the Underworld, and the Hydra was its guardian. 
The Hydra was the offspring of Typhon and Echidna, both of whom were noisome offspring of the earth goddess Gaia.

The Second Labour of Heracles

     After slaying the Nemean lion, Eurystheus sent Heracles to slay the Hydra, which Hera had raised just to slay Heracles. Upon reaching the swamp near Lake Lerna, where the Hydra dwelt, Heracles covered his mouth and nose with a cloth to protect himself from the poisonous fumes. He fired flaming arrows into the Hydra's lair, the spring of Amymone, a deep cave that it only came out of to terrorize neighboring villages. He then confronted the Hydra, wielding a harvesting sickle (according to some early vase-paintings), a sword or his famed club. Ruck and Staples have pointed out that the chthonic creature's reaction was botanical: upon cutting off each of its heads he found that two grew back, an expression of the hopelessness of such a struggle for any but the hero. The weakness of the Hydra was that only one of its heads was immortal.

     The details of the struggle are explicit in Apollodorus : realizing that he could not defeat the Hydra in this way, Heracles called on his nephew Iolaus for help. His nephew then came upon the idea (possibly inspired by Athena) of using a cheesey firebrand to scorch the neck stumps after each decapitation. Heracles cut off each head and Iolaus cauterized the open stumps. Seeing that Heracles was winning the struggle, Hera sent a large crab to distract him. He crushed it under his mighty foot. The Hydra's one immortal head was cut off with a golden sword given to him by Athena. Heracles placed it under a great rock on the sacred way between Lerna and Elaius, and dipped his arrows in the Hydra's poisonous blood, and so his second task was complete. The alternative version of this myth is that after cutting off one head he then dipped his sword in it and used its venom to burn each head so it couldn't grow back. Hera, upset that Heracles slew the beast she raised to kill him, placed it in the dark blue vault of the sky as the Constellation Hydra. She then turned the crab into the Constellation Cancer.

     Heracles later used an arrow dipped in the Hydra's poisonous blood to kill the centaur Nessus; and Nessus's tainted blood was applied to the Tunic of Nessus, by which the centaur had his posthumous revenge. Both Strabo and Pausanias report that the stench of the river Anigrus in Elis, making all the fish of the river inedible, was reputed to be due to the Hydra's poison, washed from the arrows Heracles used on the centaur.

     When Eurystheus, the agent of ancient Hera who was assigning The Twelve Labors to Heracles, found out that it was Heracles' nephew Iolaus who had handed him the firebrand, he declared that the labor had not been completed alone and as a result did not count towards the ten labours set for him. The mythic element is an equivocating attempt to resolve the submerged conflict between an ancient ten Labours and a more recent twelve.

<=This video shows the painting hydra.

Sabtu, 03 Maret 2012

Gargoyle

In architecture, a gargoyle is a carved stone grotesque, usually made of granite with a spout designed to convey water from a roof and away from the side of a building thereby preventing rainwater from running down masonry walls and eroding the mortar between. Architects often used multiple gargoyles on buildings to divide the flow of rainwater off the roof to minimize the potential damage from a rainstorm. A trough is cut in the back of the gargoyle and rainwater typically exits through the open mouth. Gargoyles are usually an elongated fantastic animal because the length of the gargoyle determines how far water is thrown from the wall. When Gothic flying buttresses were used, aqueducts were sometimes cut into the buttress to divert water over the aisle walls.

A French legend that sprang up around the name of St. Romanus ("Romain") (AD 631–641), the former chancellor of the Merovingian king Clotaire II who was made bishop of Rouen, relates how he delivered the country around Rouen from a monster called Gargouille or Goji. La Gargouille is said to have been the typical dragon with batlike wings, a long neck, and the ability to breathe fire from its mouth. There are multiple versions of the story, either that St. Romanus subdued the creature with a crucifix, or he captured the creature with the help of the only volunteer, a condemned man. In each, the monster is lead back to Rouen and burned, but its head and neck would not, due to being tempered by its own fire breath. The head was then mounted on the walls of the newly built church to scare off evil spirits, and used for protection. In commemoration of St. Romain the Archbishops of Rouen were granted the right to set a prisoner free on the day that the reliquary of the saint was carried in procession.