Sarcosuchus

Sarcosuchus (pronounced /ˌsɑrkɵˈsuːkəs/, meaning "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 Frenchpaleontologist Albert-Félix de Lapparent, in the 1940s or 1950s. He called it the "Aoulef crocodile". However, in 1997 and 2000, American paleontologistPaul Sereno discovered half a dozen new specimens, including 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).

Sarcosuchus (red) put to scale with a human and other crocodilians

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.^[2] 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.^[2]

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.^[3]

Mounted Sarcosuchus skeleton replica atThe Children's Museum of Indianapolisshowing osteoderms

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 malegharial 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.^[4]

Gallimimus ( /ˌɡælɨˈmaɪməs/ gal-i-my-məs; meaning "chicken or rooster mimic") is a genus of ornithomimid theropod dinosaur from the late Cretaceousperiod (Maastrichtian stage) Nemegt Formation of Mongolia. With individuals as long as 8 metres (26 ft),^[1] it was one of the largest ornithomimosaurs.^[2]Gallimimus is known from multiple individuals, ranging from juvenile (about 0.5 metres tall at the hip) to adult (about two metres tall at the hip).

The first fossil remains of this dinosaur were discovered in early August 1963 by a team of Professor Zofia Kielan-Jaworowska at Tsagan Khushu during a Polish-Mongolian expedition to the Gobi Desert of Mongolia. The find was reported by her in 1965.^[3] In 1972, it was named and described by paleontologists Rinchen Barsbold, Halszka Osmólska, and Ewa Roniewicz. The only named species is the type species Gallimimus bullatus. The generic name is derived from Latin gallus, "chicken", and mimus, "mimic", in reference to the neural arches of the front neck vertebrae which resemble those of the Galliformes. The specific name is derived from Latin bulla, a magic capsule worn by Roman youth around the neck, in reference to a bulbous swelling in the braincase on the underside of the parasphenoid, in the form of a capsule.^[4]

The holotype specimen, IGM 100/11, consists of a partial skeleton including the skull and lower jaws. It is a larger skeleton; several other partial skeletons have been described, most of them of juveniles, and numerous single bones.

A second species announced by Barsbold in 1996, "Gallimimus mongoliensis" based on specimen IGM 100/14 from the older Bayanshiree Formation, has never been formally referred to this genus. In a reanalysis of the nearly complete skeleton of "Gallimimus mongoliensis" Barsbold concluded in 2006 that it is not a species of Gallimimusbut may represent a new, currently unnamed ornithomimid genus.^[5]

 

Parasaurolophus (pronounced /ˌpærəsɔːˈrɒləfəs/ parr-ə-saw-rol-ə-fəs, commonly also /ˌpærəˌsɔrəˈloʊfəs/ parr-ə-sawr-ə-loh-fəs; meaning "near crested lizard" in reference to Saurolophus) was a genus of ornithopod dinosaur that lived in what is now North America during the Late Cretaceous Period, about 76.5–73 million years ago.^[1] It was an herbivore that walked both as a biped and a quadruped. Three species are recognized: P. walkeri (the type species),P. tubicen, and the short-crested P. cyrtocristatus. Remains are known from Alberta (Canada), and New Mexico and Utah (USA). The genus was first described in 1922 by William Parks from a skull and partial skeleton in Alberta.

Parasaurolophus was a hadrosaurid, part of a diverse family of Cretaceous dinosaurs known for their range of bizarre head adornments. This genus is known for its large, elaborate cranial crest, which at its largest forms a long curved tube projecting upwards and back from the skull. Charonosaurus from China, which may have been its closest relative, had a similar skull and potentially a similar crest. The crest has been much discussed by scientists; the consensus is that major functions included visual recognition of both species and sex, acoustic resonance, and thermoregulation. It is one of the rarer hadrosaurids, known from only a handful of good specimens.

Like most dinosaurs, the skeleton of Parasaurolophus is incompletely known. The length of the type specimen ofP. walkeri is estimated at 9.5 m (31 ft), and its weight is estimated at 2.5 tonnes (2.8 short tons).^[2] Its skull is about 1.6 m (5 ft 3 in) long, including the crest, whereas the type skull of P. tubicen is over 2 m (6 ft 7 in) long, indicating a larger animal.^[3] Its single known forelimb was relatively short for a hadrosaurid, with a short but wide shoulder blade. The thighbone measures 103 cm (41 in) long in P. walkeri and is robust for its length when compared to other hadrosaurids.^[4] The upper arm and pelvic bones were also heavily built.^[5]

Like other hadrosaurids, it was able to walk on either two legs or four. It probably preferred to forage for food on four legs, but ran on two.^[6] The neural spines of the vertebrae were tall, as was common in lambeosaurines;^[4] tallest over the hips, they increased the height of the back. Skin impressions are known for P. walkeri, showing uniform tubercle-like scales but no larger structures.^[7]

Parasaurolophus walkeri with scalation detail.

The most noticeable feature was the cranial crest, which protruded from the rear of the head and was made up of the premaxilla and nasal bones. The P. walkeri type specimen has a notch in the neural spines near where the crest would hit the back, but this may be a pathology peculiar to this individual.^[4]William Parks, who named the genus, hypothesized that a ligament ran from the crest to the notch to support the head.^[7] Although this idea seems unlikely,^[2] Parasaurolophus is sometimes restored with a skin flap from the crest to the neck. The crest was hollow, with distinct tubes leading from each nostril to the end of the crest before reversing direction and heading back down the crest and into the skull. The tubes were simplest in P. walkeri, and more complex in P. tubicen, where some tubes were blind and others met and separated.^[8] While P. walkeri and P. tubicen had long crests with only slight curvature, P. cyrtocristatus had a short crest with a more circular profile.^[9][edit]

Dimorphodon

Dimorphodon (pronounced /daɪˈmɔrfədɒn/) was a genus of medium-sized pterosaur from the early Jurassic Period. It was named by paleontologistRichard Owen in 1859. Dimorphodon means "two-form tooth", derived from Greek δι/di meaning 'two', μορφη/morphe meaning 'shape' and οδων/odonmeaning 'tooth', referring to the fact that it had two distinct types of teeth in its jaws - which is comparatively rare among reptiles.

The first fossil remains now attributed to Dimorphodon were found in England by fossil collector Mary Anning, at Lyme Regis in Dorset, UK in December 1828.^[1] This region of Britain is now a World Heritage Site, dubbed the Jurassic Coast; in it layers of the Blue Lias are exposed, dating from the Hettangian-Sinemurian. The specimen was acquired by William Buckland and reported in a meeting of the Geological Society on 5 February 1829.^[2] In 1835, after a thorough study by William Clift and William John Broderip, this report, strongly expanded, was published in the Transactions of the Geological Society, describing and naming the fossil as a new species. As was the case with most early pterosaur finds, Buckland classified the remains in the genus Pterodactylus, coining the new species Pterodactylus macronyx.^[3] The specific name is derived from Greek makros, "large" and onyx, "claw", in reference to the large claws of the hand. The specimen, presently NHMUK PV R 1034, consisted of a partial and disarticulated skeleton on a slab, lacking the skull. Buckland in 1835 also assigned a piece of jaw from the collection of Elizabeth Philpot to P.macronyx. Later, the many putative species assigned toPterodactylus had become so anatomically diverse that they began to be broken into separate genera.

In 1858, Richard Owen reported the find of two new specimens, NHMUK PV R 41212 and NHMUK PV R 1035, again partial skeletons but this time including the skulls. Having found the skull to be very different from that of Pterodactylus, Owen assigned Pterodactylus macronyx its own genus, which he named Dimorphodon.^[4] His first report contained no description and the name remained a nomen nudum. In 1859 however, a subsequent publication by Owen provided a description.^[5] After several studies highlighting aspects of Dimorphodon 's anatomy, Owen in 1874 made NHMUK PV R 1035 theholotype.^[6]

Meanwhile, though Dimorphodon is not a very common fossil, other fragmentary specimens were found. Some of these were acquired by Othniel Charles Marsh between 1873 and 1881 from the London fossil dealer Bryce McMurdo Wright. One of these had been recovered from early Jurassic strata at the south bank of the Severn river, at theAust Cliff.^[7]