nandi's blog

Suchomimus

Sunday, December 11, 2016

Mounted skeleton, Chicago Children's Museum.

Suchomimus (“crocodile mimic”) is a genus of large spinosaurid dinosaur with a crocodile-like skull that lived between 125–112 million years ago, during the Aptian to early Albian stage of the Cretaceous period in Niger, Africa. The only species named in the genus is Suchomimus tenerensis.

Size comparison of several species of spinosaurids and a human, Suchomimus in red. Author: Matt Martyniuk

Suchomimus was one of the largest known spinosaurid dinosaurs. It was discovered in Niger by a party led by Paul Sereno from the University of Chicago and was first described in 1998. Shortly before that, Dale Russell and Philippe Taquet announced the discovery of a very similar dinosaur from another part of Niger, but the fossils that were described by Sereno were much more complete and allowed for a more detailed reconstruction.

The length of the type specimen of Suchomimus, a subadult, was initially estimated at 10.3–11 m (34–36 ft). Its weight was estimated at between 2.7 and 5.2 tonnes (2.7 and 5.1 long tons; 3.0 and 5.7 short tons). In 2010, Gregory S. Paul gave lower estimations of 9.5 metres and 2.5 tonnes.

Like other spinosaurids, Suchomimus had a low and slender snout, much the same as that of a modern crocodile-hence the animal’s name. Suchomimus and other spinosaurids had a secondary palate. The nasal passages stretched all the way to the back of the mouth cavity, as they do in living mammals and crocodiles, and did not open within the mough, as they do in many living reptiles and most dinosaurs. This was possible because the nasal openings were set back from the tip of the snout. We do not know why these animals evolved these features, but the secondary palate may have strengthened the narrow snout or even allowed Suchomimus and its relatives to keep the tip of the snout submerged while they hunted for fish.

Like Baryonyx, Suchomimus had pointed teeth with very fine serrations. Also like Baryonyx, it had massively built forearms and a large sickle-like claw on each thumb. The nature of the teeth, together with its slender, gracile snout, suggests that Suchomimus may have been unable to catch large prey and so fed largely on fish-possibly either picking them up with its muzzle or grasping the slippery creatures with its blade-like claws.

The overall impression is of a massive and powerful creature that ate fish and presumably other sorts of meat — carrion — more than 113 million years ago, when what is today part of the Sahara was a lush, swampy habitat.

Skeletal restoration combining several specimens. By Jaime A. Headden

Stygimoloch

Sunday, December 11, 2016

Reconstructed skull at the Museum für Naturkunde, Berlin

Stygimoloch is a controversial genus of pachycephalosaurid dinosaur from the end of the Cretaceous period, roughly 66 million years ago. It is currently known from the Hell Creek Formation, Ferris Formation, and Lance Formation of the Western Interior (United States), where it lived alongside Tyrannosaurus and Triceratops.

Size comparison of Stygimoloch (purple) and a human. Author: Matt Martyniuk

It is a relatively large pachycephalosaur, with the skull being about 46 centimeters long (18 in). Among North American pachycephalosaurs, only Pachycephalosaurus is larger. Unlike other pachycephalosaurs, the domed skull is relatively small, slightly flattened from side to side, and pear-shaped; even when isolated this unusual dome can easily be distinguished from the broader, larger domes of Pachycephalosaurus. While the dome is reduced in size, the ornamentation over the skull is more elaborate than in any other pachycephalosaur. Short, conical hornlets covered the nose, and the back corners of the skull bore an enormous pair of massive, backward-pointing spikes, up to 5 centimeters in diameter (2 in) and 15 centimeters long (6 in); these are surrounded by two or three smaller spikes. The function of this unusual ornamentation is unknown. Even if other pachycephalosaurs did butt heads (which is a subject of continuing debate), the small dome of Stygimolochsuggests that this behavior was not as important. Instead, the skull ornament might have functioned for display, may have been used for self-defense, or perhaps were locked together and used in shoving matches, like the horns of deer. Another possibility is that the squamosal horns were used to inflict pain during flank-butting.

MARGINOCEPHALIA. www.geol.umd.edu

The pachycephalosaur Dracorex may actually be an individual of Stygimoloch or Pachycephalosaurus in which the dome and horns are not well-developed, either because the animal was a juvenile or because the animal was a female. This consideration was supported at the 2007 annual meeting of the Society of Vertebrate Paleontology. Jack Horner of Montana State University presented evidence, from analysis of the skull of the single existing Dracorex specimen, that this dinosaur may well be a juvenile form of Stygimoloch. In addition, he presented data that indicates that both Stygimoloch and Dracorexmay be juvenile forms of Pachycephalosaurus. Horner and M.B. Goodwin published their findings in 2009, showing that the spike/node and skull dome bones of all three ‘species’ exhibit extreme plasticity, and that both Dracorex and Stygimoloch are known only from juvenile specimens while Pachycephalosaurus is known only from adult specimens. These observations, in addition to the fact that all three forms lived in the same time and place, lead them to conclude that Dracorex and Stygimoloch were simply juvenile Pachycephalosaurus, which lost spikes and grew domes as they aged. A 2010 study by Nick Longrich and colleagues also supported the hypothesis that all flat-skulled pachycephalosaurs were juveniles, suggesting that flat-skulled forms like Goyocephale and Homalocephale represent juveniles of dome-skulled adults.

Struthiomimus

Sunday, December 11, 2016

Struthiomimus by Mohamad Haghani

Struthiomimus (meaning “ostrich mimic”) is a genus of ornithomimid dinosaurs from the late Cretaceous of North America. Ornithomimids were long-legged, bipedal, ostrich-like dinosaurs with toothless beaks. The type species, Struthiomimus altus, is one of the more common small dinosaurs found in Dinosaur Provincial Park; its abundance suggests that these animals were herbivores or omnivores rather than pure carnivores.

Struthiomimus sedens skeleton in the Oxford University Museum of Natural History

The size of S. altus is estimated as about 4.3 metres (14 ft) long and 1.4 metres (4.6 ft) tall at the hips, with a weight of around 150 kilograms (330 lb).

Struthiomimus had a build and skeletal structure typical of ornithomimids, differing from closely related genera like Ornithomimus and Gallimimus in proportions and anatomical details. As with other ornithomimids, they had small slender heads on long necks (which made up about 40% of the length of the body in front of the hips). Their eyes were large and their jaws were toothless. Their vertebral columns consisted of ten neck vertebrae, thirteen back vertebrae, six hip vertebrae, and about thirty-five tail vertebrae. Their tails were relatively stiff and probably used for balance. They had long slender arms and hands, with immobile forearm bones and limited opposability between the first finger and the other two. As in other ornithomimids but unusually among theropods, the three fingers were roughly the same length, and the claws were only slightly curved; Henry Fairfield Osborn, describing a skeleton of S. altus in 1917, compared the arm to that of a sloth. These might have been adaptations to support wing feathers.

Struthiomimus differed from close relatives only in subtle aspects of anatomy. The edge of the upper beak was concave in Struthiomimus, unlike Ornithomimus, which had straight beak edges. Struthiomimus had longer hands relative to the humerus than other ornithomimids, with particularly long claws. Their forelimbs were more robust than in the similar Ornithomimus.

Struthiomimus atlus by lizardman22
Fossil remains of S. altus are only known definitively from the Oldman Formation, dated to between 78 and 77 million years ago during the Campanian stage of the late Cretaceous period. A younger species (which has not yet been named), which apparently differed from S. altus in having longer, more slender hands, is known from several specimens found in the Horseshoe Canyon Formation and lower Lance Formation, between 69 and 67.5 million years ago (early Maastrichtian).

Sinornithosaurus

Sunday, December 11, 2016

Sinornithosaurus millenii fossil displayed in Hong Kong Science Museum

Sinornithosaurus (derived from a combination of Latin and Greek, meaning ‘Chinese bird-lizard’) is a genus of feathered dromaeosaurid dinosaur from the early Cretaceous Period (early Aptian) of the Yixian Formation in what is now China. It was the fifth non–avian feathered dinosaur genus discovered by 1999. The original specimen was collected from the Sihetun locality of western Liaoning. It was found in the Jianshangou beds of the Yixian Formation, dated to 124.5 million years ago. Additional specimens have been found in the younger Dawangzhangzi bed, dating to around 122 million years ago.

Sinornithosaurus by PrehistoricWildlife.com

The small predatory dinosaur Sinornithosaurus was a dromaeosaurid-one of a group of agile bipedal runners with large eyes, relatively large brains, and long, narrow snouts equipped with steak-knife teeth. The three fingers on each hand and the four toes of each foot had long, curved, wickedly sharp claws for hooking into prey, with the second toe claw being extra large. As in many other dinosaurs, especially fast-running kinds, the tail was stiffened by overlapping bony rods.

Skeletal reconstructions of S. millenii and NGMC 91. Author: Jaime A. Headden

Sinornithosaurus was discovered by Xu Xing, Wang Xiaolin and Wu Xiaochun of the Institute of Vertebrate Paleontology and Paleoanthropology of Beijing. An almost-complete fossil with feather impressions, was recovered from Liaoning Province, China, in the Yixian Formation; the same incredibly rich location where four dinosaurs with feathers were discovered previously, ProtarchaeopteryxSinosauropteryxCaudipteryx, and Beipiaosaurus. The holotype specimen is IVPP V12811, in the collection of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China.

The NGMC 91 specimen is in the collection of the National Geological Museum of China. It was collected in Fanzhangzi quarry, near Lingyuan City, Liaoning Province. This location is part of the Dawangzhangzi fossil beds, which have been dated to about 122 million years ago, during the early Aptian age. A specimen of the fish Lycoptera is also preserved near the foot.

Artist's impression of S. millenii
Phylogenetic studies did not support the idea that NGMC 91 was a close relative of S. millenii. In a 2004 analysis, Phil Senter and colleagues found that it was, in fact, more closely related to Microraptor. Subsequent studies, also by Senter, have continued to show support for this finding despite the fact that some data used in the original study was later found to be flawed.

Sinosauropteryx

Sunday, December 11, 2016

Sinosauropteryx

Sinosauropteryx (meaning “Chinese reptilian wing”, Chinese: 中华龙鸟; pinyin: Zhōnghuá lóng niǎo; literally: “China dragon bird”) is a compsognathid dinosaur. Described in 1996, it was the first dinosaur taxon outside of Avialae (birds and their immediate relatives) to be found with evidence of feathers. It was covered with a coat of very simple filament-like feathers. Structures that indicate colouration have also been preserved in some of its feathers, which makes Sinosauropteryx the first non-avialian dinosaurs where colouration has been determined. The colouration includes a reddish and light banded tail. Some contention has arisen with an alternative interpretation of the filamentous impression as remains of collagen fibres, but this has not been widely accepted.

 

Size of adult and sub-adult specimens, compared with a human. Author: Matt Martyniuk

Sinosauropteryx caused a sensation when it was revealed to the world in 1996. Here was a clear and perfectly preserved skeleton of a small theropod dinosaur, but covering most of the body were impressions of an enigmatic fuzz, a coat of fine filaments up to 1 1/2 inches (4 cm) long.

Skin impressions found for some dinosaurs reveal that they had scales. But the growing recognition that birds evolved from dinosaurs raised the possibility that some dinosaurs had feathers, or at least some kind of protofeather-like body covering that later evolved into the feathers of present-day birds. However, feathers are relatively soft and rarely fossilized.

Skeletal restoration of two specimens. Author: Jaime A. Headden

It is likely that several birdlike dinosaurs may have had feathers or similar structures, but, as they were not preserved, we know nothing about them. Then Sinosauropteryx was found in the fabulous Liaoning deposits in China. Here was the right kind of dinosaur (a small, advanced theropod) with much of its back, rump, and tail covered in a fine, filamentous fuzz that appeared to be fur-like coat made up of short, single strands.

While lacking the complex structure of a feather, it was a more intricate body covering than simple reptilian scales. The fuzzy coat seemed to form a downy layer that would have been perfect for trapping body heat and keeping the animal warm. This observation lends more weight to the ongoing debate that some dinosaurs were warm-blooded. It is also possible that the fuzz was used when displaying to attract mates.

Sinosauropteryx fossil, from our trip to Hohhot, Inner Mongolia, China for National Day Holiday 2007. This is the Inner Mongolia Museum, the biggest museum in the region. Sam / Olai Ose / Skjaervoy from Zhangjiagang, China

In one of the specimens was the remains of its last meal, a small, unidentified animal-providing proof that this little ancestor of the birds ate the ancestors of modern mammals. One of the other specimens revealed unlaid eggs in the oviducts.

Sinosauropteryx Photo: PA

Scutellosaurus

Sunday, December 11, 2016

Scutellosaurus

Scutellosaurus is an genus of thyreophoran ornithischian dinosaur that lived approximately 196 million years ago during the early part of the Jurassic Period in what is now Arizona, USA. It is classified in Thyreophora, the armoured dinosaurs; its closest relatives may have been Emausaurus and Scelidosaurus, another armored dinosaur which was mainly a quadrupedal dinosaur, unlike bipedal Scutellosaurus. It is one of the earliest representatives of the armored dinosaurs and the basalmost form discovered to date. Scutellosaurus was a small, lighly-built, ground-dwelling, herbivore, that could grow up to an estimated 1.2 m (3.9 ft) long.
 

1. Scelidosaurus harrisonii (“limb lizard”) 1861 Chordata/Ornithischia/Scelidosauridae. 2. Scutellosaurus lawleri (“little shielded lizard”) 1981 Chordata/Ornithischia.

The holotype specimen of Scutellosaurus lawleri (MNA V175) was recovered at the West Moenkopi Plateau locality in the Silty Facies Member of the Kayenta Formation, in Coconino County, Arizona on the land of the Navajo Nation. The specimen was discovered and collected by David Lawler in red claystone sediments that were deposited during the Sinemurian stage of the Jurassic period, approximately 196 million years ago.
 
Scutellosaurus is one of the earliest representatives of the armored dinosaurs (the thyreophorans) that would later include giants as Stegosaurus and Ankylosaurus. However, compared to some of its later relatives, Scutellosaurus was small and lightly armored. Along its back and extending onto the base of the tail were rows of small bony “shields” embedded in the skin. Some of these shields were flat, while others were pitched, like little roofs. The largest shields formed two rows that ran along the middle of the back.
 
Spread across the back, the shields formed a protective armored layer that would have defended the animal from attacks by such meat-eating dinosaurs as Dilophosaurus, with which it shared its early Jurassic world. Scutellosaurus would also have been reasonably fleet of foot and therefore able to escape predators by weaving its way through tangled undergrowth.
 
Skeletal reconstruction showing known material. Author: Jaime A. Headden
Scutellosaurus was lightly built, and was probably capable of walking on its hind legs. It had an unusually long tail, possibly to provide a counterbalance against the weight of the armored body. It was around 1.2 metres (3.9 ft) long, 50 centimetres (20 in) tall at the hips, and weighed 10 kilograms (22 lb). The fossil evidence includes several partial skeletons recovered from Arizona by the Museum of Northern Arizona and the University of California Museum of Paleontology, although the skull is poorly known from these specimens. There were several hundred osteoderms running along its neck to its back and as far down as its tail. These formed parallel rows, with as many as five rows on each side. It also had double rows of osteoderms, or external plates, running neck to tail. Some of these shields were flat, while others were pitted.

Pachyrhinosaurus

Saturday, December 10, 2016

P. perotorum mounted at the Perot Museum

Pachyrhinosaurus (meaning “thick-nosed lizard”) is an extinct genus of centrosaurine ceratopsid dinosaurs from the Late Cretaceous period of North America. The first examples were discovered by Charles M. Sternberg in Alberta, Canada, in 1946, and named in 1950. Over a dozen partial skulls and a large assortment of other fossils from various species have been found in Alberta and Alaska. A great number were not available for study until the 1980s, resulting in a relatively recent increase of interest in the Pachyrhinosaurus. Three species have been identified. P. lakustai, from the Wapiti Formation, the bonebed horizon of which is roughly equivalent age to the upper Bearpaw and lower Horseshoe Canyon Formations, is known to have existed from about 73.5-72.5 million years ago. P. canadensis is younger, known only from the lower Horseshoe Canyon Formation, about 71.5-71 Ma ago. Fossils of the youngest species, P. perotorum, have been recovered from the Prince Creek Formation of Alaska, and date to 70-69 million years ago. The presence of three known species makes this genus the most speciose among the centrosaurines.

Pachyrhinosaurus by PrehistoricWildlife.com

QUICK PACHYRHINOSAURUS FACTS

  • May have run as fast as 20 MPH

  • Lived in parts of Canada and Alaska

  • Its name means “thick nosed lizard”

  • 3 species of this dinosaur have been discovered

  • Weighed as much as a Black Rhinoceros

ABOUT PACHYRHINOSAURUS

Pachyrhinosaurus is a dinosaur which lived around 70 million years ago during the late Cretaceous Period. It was first discovered in the late 1940s by Charles M. Sternberg, son of famous paleontologists Charles H. Sternberg who found specimens in Alberta, Canada and Alaska, U.S. He also named the fossil, calling it Pachyrhinosaurus—a name which means “thick nosed lizard.”

Pachyrhinosaurus was an herbivore that was approximately 20 to 26 feet long, about 6 feet high and weighed around 2 to 3 tons. Like other dinosaur’s in this dinosaur order, the Pachyrhinosaurus had a large bony frill that came out of the back of its skull. However, what makes this dinosaur different from the other ones in it dinosaur classification is that instead of horns on its nose it had a large bony bump called a “boss.” It did have a pair of horns that grew out of the top of its frill and it may have had horns over its eyes.

Like other herbivores of this time, the Pachyrhinosaurus probably traveled in herds that kept it safe from predators. Paleontologists believe that some of these herds may have had hundreds or thousands of animals in it at one time. If this was indeed the case, then it would have made it quite difficult on predators. It is also likely that these dinosaurs also nested their eggs like modern birds and may have even taken care of them. This has been found to be the case in other dinosaur types such as the Protoceratops and the Styracosaurus.

Paleontologists believe this animal probably lived off of a diet that consisted mainly of palms and cycads and other tough plant material that it could tear off and crush with its beak. It also had cheek teeth that it could use to further masticate this tough plant material, making it easier to digest.

P. perotorum engaged in intraspecific combat. Artistic rendering of Pachyrhinosaurus perotorum engaged in head-butting/pushing behavior. In the first description of Pachryhinosaurus by Sternberg, he speculated that the enlarged nasal boss in the taxon might have been used in head battering or pushing behavior, an idea emphasized by this image of two Pachyrhinosaurus perotorum sparring with their craniofacial bosses, while a third looks on. Author: Karen Carr

Anchiceratops

Saturday, December 10, 2016

Anchiceratops by atrox1 on DeviantArt

Anchiceratops is an genus of chasmosaurine ceratopsid dinosaur that lived approximately 72 to 71 million years ago during the latter part of the Cretaceous Period in what is now Alberta, Canada. Anchiceratops was a medium-sized, heavily built, ground-dwelling, quadrupedal herbivore that could grow up to an estimated 5 m (16.4 ft) long. Its skull featured two long brow horns and a short horn on the nose. The skull frill was elongated and rectangular, its edges adorned by coarse triangular projections. About a dozen skulls of the genus have been found.

NMC 8547 mounted at the Canadian Museum of Nature, completed with a skull cast of NMC 8535. NMC 8547 might represent a separate taxon.

Anchiceratops was a medium-sized ceratopsid. If specimen NMC 8547 is not taken into account, no very exact estimations of the body length of Anchiceratops can be given. Some popular science book state that it approached 20 feet (6 m) in length. In 2010 Gregory S. Paul, on the assumption that specimen NMC 8547 represented Anchiceratops, estimated its length at 4.3 metres, its weight at 1.2 tonnes.

The first remains of Anchiceratops were discovered along the Red Deer River in the Canadian province of Alberta in 1912 by an expedition led by Barnum Brown. The holotype, specimen AMNH 5251, is the back half of a skull, including the long frill, and two other partial skulls, specimens AMNH 5259 (the paratype) and AMNH 5273, were found at the same time, which are now stored in the American Museum of Natural History in New York City. A complete skull designated NMC 8535, was discovered by Charles M. Sternberg at Morrin in 1924, and was described as A. longirostris five years later, in 1929. but this species is widely considered a junior synonym of A. ornatus today. In total, at least ten incomplete skulls have been recovered. The skulls are different with respect to their proportions (e.g. size of the supraorbital horn cores, the dimensions of the frill) which had led researchers to conclude that the disparity is a result of interspecific differences or due to sexual dimorphism.

ROM 802, a skull in the Royal Ontario Museum by Daderot

The most distinctive features of this dinosaur are in its unusual neck frill. The frill is moderately long and rectangular with small, oval fenestrae (openings). The edge of the frill is thick just behind the brow horns. On the back of the frill are six large epoccipitals (bony knobs around the frill) that were expanded into short, triangular, backward-pointing spikes. Also on the frill are two short spikes that curve up and out.

Anchiceratops had a short nasal horn, a very long nose, and two moderate-size brow horns. Its skeleton shows it had a very short tail, but otherwise it looked much like other ceratopsids.

Anchiceratops lived at the same time as its close relative Arrhinoceratops. It was also closely related to TorosaurusChasmosaurusPentaceratops, and Triceratops.

Styracosaurus

Saturday, December 10, 2016

Styracosaurus by atrox1 on DeviantArt

Styracosaurus (meaning “spiked lizard” from the Ancient Greek styrax/στύραξ “spike at the butt-end of a spear-shaft” and sauros/σαῦρος “lizard”) was a genus of herbivorous ceratopsian dinosaur from the Cretaceous Period (Campanian stage), about 75.5 to 75 million years ago. It had four to six long horns extending from its neck frill, a smaller horn on each of its cheeks, and a single horn protruding from its nose, which may have been up to 60 centimetres (2 ft) long and 15 centimetres (6 in) wide. The function or functions of the horns and frills have been debated for many years.

Size compared to a human by Marmelad

Styracosaurus was a relatively large dinosaur, reaching lengths of 5.5 metres (18 ft) and weighing nearly 3 tonnes. It stood about 1.8 meters (6 ft) tall. Styracosaurus possessed four short legs and a bulky body. Its tail was rather short. The skull had a beak and shearing cheek teeth arranged in continuous dental batteries, suggesting that the animal sliced up plants. Like other ceratopsians, this dinosaur may have been a herd animal, traveling in large groups, as suggested by bonebeds.

Named by Lawrence Lambe in 1913, Styracosaurus is a member of the Centrosaurinae. One species, S. albertensis, is currently assigned to Styracosaurus. Other species once assigned to the genus have since been reassigned elsewhere.

Styracosaurus skeleton at Canadian Museum of Nature, Ottawa, Ontario. The Vagaceratops irvinensis type specimen can be seen in the lower left corner. Author: D. Gordon E. Robertson

The first fossil remains of Styracosaurus were collected in Alberta, Canada by C.M. Sternberg (from an area now known as Dinosaur Provincial Park, in a formation now called the Dinosaur Park Formation) and named by Lawrence Lambe in 1913. This quarry was revisited in 1935 by a Royal Ontario Museum crew who found the missing lower jaws and most of the skeleton. These fossils indicate that S. albertensis was around 5.5 to 5.8 meters in length and stood about 1.65 meters high at the hips. An unusual feature of this first skull is that the smallest frill spike on the left side is partially overlapped at its base by the next spike. It appears that the frill suffered a break at this point in life and was shortened by about 6 centimeters (2 in). The normal shape of this area is unknown because the corresponding area of the right side of the frill was not recovered.

 

Styracosaurus is a member of the Centrosaurinae. Other members of the clade include Centrosaurus (from which the group takes its name), PachyrhinosaurusAvaceratopsEiniosaurusAlbertaceratopsAchelousaurusBrachyceratops, and Monoclonius, although these last two are dubious. Because of the variation between species and even individual specimens of centrosaurines, there has been much debate over which genera and species are valid, particularly whether Centrosaurusand/or Monoclonius are valid genera, undiagnosable, or possibly members of the opposite sex. In 1996, Peter Dodson found enough variation between CentrosaurusStyracosaurus, and Monoclonius to warrant separate genera, and that Styracosaurusresembled Centrosaurus more closely than either resembled Monoclonius. Dodson also believed one species of MonocloniusM. nasicornis, may actually have been a female Styracosaurus. However, most other researchers have not accepted Monoclonius nasicornis as a female Styracosaurus, instead regarding it as a synonym of Centrosaurus apertus. While sexual dimorphism has been proposed for an earlier ceratopsian, Protoceratops, there is no firm evidence for sexual dimorphism in any ceratopsid.

Depiction of dietary niche partitioning among megaherbivorous dinosaurs from the DPF (MAZ-2).  Left to right: Chasmosaurus belli, Lambeosaurus lambei, Styracosaurus albertensis, Euoplocephalus tutus, Prosaurolophus maximus, Panoplosaurus mirus. A herd of S. albertensis looms in the background. Image courtesy of J.T. Csotonyi.

Styracosaurus is known from the Dinosaur Park Formation, and was a member of a diverse and well-documented fauna of prehistoric animals that included horned relatives such as Centrosaurus and Chasmosaurus, duckbills such as ProsaurolophusLambeosaurusGryposaurusCorythosaurus, and Parasaurolophustyrannosaurids GorgosaurusDaspletosaurus, and armored Edmontonia and Euoplocephalus.

Tenontosaurus

Saturday, December 10, 2016

Reconstructed skeleton of Tenontosaurus, from the Cloverly Formation.

Tenontosaurus (meaning “sinew lizard”) is a genus of medium- to large-sized ornithopod dinosaur. The genus is known from the late Aptian to Albian ages of the middle Cretaceous period sediments of western North America, dating between 115 and 108 million years ago.

The genus contains two species, Tenontosaurus tilletti (described by John Ostrom in 1970) and Tenontosaurus dossi (described by Winkler, Murray, and Jacobs in 1997). Many specimens of T. tilletti have been collected from several geological formations throughout western North America. T. dossi is known from only a handful of specimens collected from the Twin Mountains Formation of Parker County, Texas.

Restoration of T. tilletti by Nobu Tamura

It was about 6.5 to 8 metres (21 to 26 ft) long and 3 metres (9.8 ft) high in a bipedal stance, with a mass of somewhere between 1 to 2 tonnes (1 to 2 short tons). It had an unusually long, broad tail, which like its back was stiffened with a network of bony tendons.

Tenontosaurus fed on plant matter, which it broke off with its horny beak and then chewed with its teeth, all of which were at the back of its mouth. The small, swift-moving Deinonychus was Tenontosaurus’s main enemy. The teeth of this predator have been found along with Tenontosaurus skeletons. Some scientists therefore believe that Deinonychus hunted the larger animal in packs, but there is no real evidence to support this. In spite of what would seem to be the advantages of having clawed feet and a huge tail, Tenontosaurus would have been easy catch for packs of sharp-fanged Deinonychus.

 

T. tilletti with juveniles, in front of Deinonychus, Academy of Natural Sciences, Philadelphia by Daderot

The first Tenontosaurus fossil was found in Big Horn County, Montana by an American Museum of Natural History (AMNH) expedition in 1903. Subsequent digs in the same area during the 1930s unearthed 18 more specimens, and four specimens were found during the 1940s. Despite the large number of fossil specimens, the animal was not named or scientifically described during this time, though Barnum Brown of the AMNH gave it the informal name “Tenantosaurus”, “sinew lizard”, in reference to the extensive system of stiffening tendons in its back and tail.

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