Ultrasaurus

This article is about the dubious dinosaur genus from South Korea. For the invalid dinosaur genus from Colorado, see Ultrasauros.

Ultrasaurus is a genus of sauropod dinosaur discovered by Haang Mook Kim in South Korea. However, the name was first used unofficially (as anomen nudum) in 1979 by Jim Jensen to describe a set of giant dinosaur bones he discovered in the United States. Because Kim published the name for his specimen before Jensen could do so officially, Jensen renamed his specimen Ultrasauros. Jensen's giant sauropod was later found to be a chimera, and the type remains are now assigned to Supersaurus.

http://en.wikipedia.org/wiki/Ultrasaurus

American Lion

The term "American lion" has sometimes been used to mean the cougar.

This article is about the feline. For the Pulitzer-winning biography, see American Lion (book).

The American lion (Panthera atrox) — also known as the North American lion or American cave lion — is an extinct feline of thefamily Felidae, endemic to North America during the Pleistocene epoch (1.8 mya to 11,000 years ago), existing for approximately1.79 million years.^[1] While it was once considered a subspecies of lion closely related to the Eurasian cave lion (Panthera leo spelaea),^[2] later study showed that it was not in fact a true lion and cannot be assigned to any modern species of cat.^[3]

The American lion was one of the largest types of cat ever to have existed, slightly larger than the Early Middle Pleistocene primitive cave lion, P. leo fossilis and about twenty-five percent larger than the modern African lion.^[4]

http://en.wikipedia.org/wiki/American_Lion

Smilodon

The species of Smilodon were among the largest felids ever to live; the heaviest specimens of the massively built carnivore S. populator may have exceeded 500 kg (1,100 lb).^[4]

A fully-grown Smilodon weighed approximately 55 to 470 kg (120 to 1,000 lb), depending on species. It had a short tail, powerful legs, muscular neck and long canines. Smilodon was more robustly built than any modern cat, comparable to a bear. The lumbar region of the back was proportionally short, and the lower limbs were shortened relative to the upper limbs in comparison with modern pantherine cats, suggesting that Smilodon was not built for speed.

The largest species, the South American S. populator, had higher shoulders than hips and a back that sloped downwards, superficially recalling the shape of a hyena, in contrast to the level-backed appearance of S. fatalis, which was more like that of modern cats. However, while its front limbs were relatively long, their proportions were extremely robust and the forearm was shorter relative to the upper arm bone than in modern big cats, and proportionally even shorter than in S. fatalis. This indicates that these front limbs were designed for power rather than fast running, and S. populator would have had immense strength in its forequarters.

[edit]Limbs

S. populator skeleton

Smilodon had relatively shorter and more massive limbs than other felines. It had well developed flexors and extensors in its forepaws,^{[citation needed]} which enabled it to pull down large prey.^[7] The back limbs had powerfully built adductor muscles which might have helped the cat's stability when wrestling with prey. Like most cats, its claws were retractable.

[edit]Teeth and jaws

Skull and neck at the AMNH

Smilodon is most famous for its relatively long canines, which are the longest found in the sabre-toothed cats, at about 28 cm (11 in) long in the largest species Smilodon populator.

These canine teeth were fragile and could not have bitten into bone; thus, these cats did not use their long teeth while taking down prey, due to the risk of breaking them. Only when their prey was totally subdued did they use their teeth to simultaneously sever the blood supply and strangle the windpipe, instantly killing the prey.^{[citation needed]}

Despite being more powerfully built than other large cats, Smilodon actually had a weaker bite. Modern big cats have more pronouncedzygomatic arches, while Smilodon had smaller zygomatic arches which restricted the thickness and therefore power of the temporalis muscles, and thus reduced Smilodon’s bite force. Analysis of its narrow jaws indicates that it could produce a bite only a third as strong as that of a lion.^[8] There seems to a be a general rule that the sabre-toothed cats with the largest canines had proportionally weaker bites. However, analyses of canine bending strength (the ability of the canine teeth to resist bending forces without breaking) and bite forces indicate that sabre-toothed cats' teeth were stronger relative to the bite force than those of modern "big cats".^[9] In addition, Smilodon could open its jaws 120 degrees, whereas the lion's gape is limited to 60 degrees.^[10]

It has been suggested that Smilodon's smaller temporalis muscles (controlling much of the bite force) were not used in the killing of prey; rather, Smilodon stretched its jaws around the throat and pressed its canines into the prey with the use of its immense neck and forelimb muscles. The penetration was the result of the neck flexors instead of the jaw muscles, according to this hypothesis.

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weekly daily dinosaur: Rhamphorhynchus

 "beak snout", is a genus of long-tailed pterosaurs in the Jurassic period. Less specialized than contemporary, short-tailed pterodactyloid pterosaurs such as Pterodactylus, it had a long tail, stiffened with ligaments, which ended in a characteristic diamond-shaped vane. The jaws of Rhamphorhynchus housed needle-like teeth, which were angled forward, with a curved, sharp, beak-like tip lacking teeth, indicating a diet mainly of fish and insects.

Although fragmentary fossil remains possibly belonging to Rhamphorhynchus have been found in England, Tanzania, and Spain, the best preserved specimens come from the Solnhofen limestone of Bavaria, Germany. Many of these fossils preserve not only the bones but impressions of soft tissues such as wing membranes. Scattered teeth believed to belong to Rhamphorhynchus have been found in Portugal as well.^[1]

http://en.wikipedia.org/wiki/Rhamphorhynchus

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weekly mammal: Phorusrhacids

Phorusrhacids ("Rag-Thieves"), colloquially known as "terror birds" as the larger species were apex predators during the Miocene, were aclade of large carnivorous flightless birds that were the dominant predators in South America during the Cenozoic, 62–2 million years (Ma) ago.^[3] They were roughly 1–3 meters (3–10 feet) tall. Their closest modern-day relatives are believed to be the 80 cm-tall seriemas. Titanis walleri, one of the larger species, is known from Texas and Florida in North America. This makes the phorusrhacids the only known example of large South American predators migrating north during the Great American Interchange (which occurred after the volcanic Isthmus of Panama land bridge rose ca. 3 Ma ago). It was once believed that T. walleri only became extinct around the time of the arrival of humans in North America,^[4] but subsequent datings of Titanis fossils have failed to provide evidence for their survival more recently than 1.8 Ma ago.^[5]

Possible phorusrhacid remains have recently been recovered from the Eocene of Algeria.^[6]

A recently discovered species, Kelenken guillermoi from Middle Miocene some 15 million years ago, discovered in Patagonia in 2006, represents the largest bird skull yet found. The fossil has been described as being a 71 cm (28 in), nearly intact skull. The beak is roughly 46 cm (18 in) long and curves in a hook shape that resembles an eagle's beak. Most species described as phorusrhacid birds were smaller, 60–90 cm (2.0–3.0 ft) tall, but the new fossil belongs to a bird that probably stood about 3 m (9.8 ft) tall. Although scientists cannot be sure, they theorize that the large terror birds were extremely nimble and quick runners able to reach speeds of 48 km/h (30 mph).^[7]

http://en.wikipedia.org/wiki/Phorusrhacidae

weekend daily dinosaur: Ornithocheirus

Ornithocheirus (from Greek "ορνις", meaning bird, and "χειρ", meaning hand) was a pterosaur from the Cretaceous period of Europeand South America. Based on poor fossil material, the genus has caused enduring problems of zoological nomenclature.

Fossil remains currently classified as Ornithocheirus have been recovered mainly from the Cambridge Greensand of England, dating to the beginning of the Albian stage of the late Cretaceous period, about 110 million years ago.^[1] Additional fossils from the Santana Formation of Brazil, dating to 112-108 million years ago, have been classified as species of Ornithocheirus.^[2]

http://en.wikipedia.org/wiki/Ornithocheirus

weekly mammal: Australopithecus

Australopithecus (Latin australis "southern", Greek πίθηκος pithekos "ape") is a genus of hominids that is now extinct. From the evidence gathered by palaeontologists and archaeologists, it appears that the Australopithecus genus evolved in eastern Africa around 4 million years ago before spreading throughout the continent and eventually becoming extinct 2 million years ago. During this time period various different forms of australopiths existed, including Australopithecus anamensis, A. afarensis, A. sediba, and A. africanus. There is still some debate amongst academics whether certain African hominid species of this time, such as A. robustus and A. boisei, constitute members of the same genus; if so, they would be considered to be robust australopiths whilst the others would be considered gracile australopiths. However, if these species do indeed constitute their own genus, then they may be given their own name, the Paranthropus.

It is widely held by archaeologists and palaeontologists that the australopiths played a significant part in human evolution, and it was one of the australopith species that eventually evolved into the Homo genus in Africa around 2 million years ago, which contained within it species like Homo habilis, H. ergaster and eventually the modern human species, H. sapiens sapiens.^[1]

http://en.wikipedia.org/wiki/Australopithecus