Blogs

10 Crazy Facts About Stegosaurus

Thursday, December 15, 2016

Stegosaurus

How Much Do You Really Know About Stegosaurus?

Few people know much about Stegosaurus beyond the fact that a) it had triangular plates on its back, b) it was dumber than the average dinosaur, and c) its plastic figurine looks really cool on an office desk. On the following article, you’ll discover 10 fascinating facts about Stegosaurus, the popular plant-eater with the spiked tail and plated back.

Stegosaurus Had a Brain the Size of a Walnut

The tiny skull of Stegosaurus contained an equally tiny brain (Wikimedia Commons)

Given its size, Stegosaurus was equipped with an unusually small brain, comparable to that of a modern Golden Retriever. How could a four-ton dinosaur possibly survive and thrive with so little gray matter? Well, as a general rule, any given animal only has to be slightly smarter than the food it eats (in Stegosaurus’ case, primitive ferns and cycads) and just alert enough to avoid predators–and by those standards, Stegosaurus was brainy enough to prosper in the wilds of late Jurassic North America.

Paleontologists Once Thought Stegosaurus Had a Brain in its Butt

An early depiction of Stegosaurus (Charles R. Knight)

Early naturalists had a hard time wrapping their minds around the diminutive size of Stegosaurus’ brain. It was once proposed (by no less an eminence than the famous American paleontologist Othniel C. Marsh) that this none-too-bright herbivore possessed supplementary grey matter located somewhere in its hip region, but contemporaries quickly soured on this “brain in the butt” theory when the fossil evidence proved unavailing.

The Spiked Tail of Stegosaurus Is Called a “Thagomizer”

The spiked tail of Stegosaurus (Wikimedia Commons)

Way back in 1982, a famous Far Side cartoon depicted a group of cavemen clustered around a picture of a Stegosaurus tail; one of them points to the sharp spikes and says, “Now this end is called the thagomizer…after the late Thag Simmons.” The word “thagomizer” has been used by paleontologists ever since.

There’s a Lot We Don’t Know About Stegosaurus’ Plates

A comparison of the largest wide plate (A) next to the largest tall plate (B) of the studied Stegosaurus mjosi plates.

The name Stegosaurus means “roofed lizard,” reflecting the belief of 19th-century paleontologists that this dinosaur’s plates lay flat along its back, like a form of armor. Various reconstructions have been offered up since then, the most convincing of which has the plates alternating in parallel rows, pointy ends up, from this dinosaur’s neck all the way down to its butt. As to why these structures evolved in the first place, that’s still a mystery.

Stegosaurus Supplemented its Diet with Small Rocks

Small Pebble Rocks

Like many plant-eating dinosaurs of the Mesozoic Era, Stegosaurus intentionally swallowed small rocks (known as gastroliths) that helped mash up the tough vegetable matter in its enormous stomach; it would have had to eat hundreds of pounds of ferns and cycads every day to maintain its presumably cold-blooded metabolism. Of course, it’s also possible that Stegosaurus swallowed rocks because it had a brain the size of walnut; who knows?

Stegosaurus Was One of the Earliest Dinosaurs to Evolve Cheeks

Side view of the Stegosaurus skull

Although it was undoubtedly lacking in other respects, Stegosaurus did possess one relatively advanced anatomical feature: extrapolating from the shape and arrangement of its teeth, experts believe this plant-eater may have possessed primitive cheeks. Why were cheeks so important? Well, they gave Stegosaurus the ability to thoroughly chew and pre-digest its food before swallowing it, and also allowed this dinosaur to pack away more vegetable matter than its non-cheeked competition.

Stegosaurus is the State Dinosaur of Colorado

Colorado’s state dinosaur is the Stegosaurus, since 1982.

Back in 1982 (around the same time Gary Larson was coining the word “thagomizer”), the governor of Colorado signed a bill making Stegosaurus the official state dinosaur, after a two-year write-in campaign spearheaded by thousands of fourth-grade students. This is a bigger honor than you might think, considering the huge number of dinosaurs that have been discovered in Colorado, including AllosaurusApatosaurus and Ornithomimus.

It Was Once Thought that Stegosaurus Walked on Two Legs

Another early depiction of Stegosaurus (Wikimedia Commons)

Because it was discovered relatively early in paleontological history, Stegosaurus has become the poster-lizard for wacky dinosaur theories (such as that brain-in-the-butt blunder detailed in slide #3). Early naturalists once thought this dinosaur r was bipedal, like Tyrannosaurus rex; even today, some experts argue that Stegosaurus may have been occasionally capable of rearing back on its two hind feet, especially when threatened by a hungry Allosaurus, though few people are convinced.

Most Stegosaurs Hailed from Asia, not North America

Image of a map that displays where Stegosaurid dinosaur fossils are found.

Although it’s by far the most famous, Stegosaurus wasn’t the only spiked, plated dinosaur of the late Jurassic period. The remains of these odd-looking reptiles have been discovered across the expanse of Europe and Asia, with the largest concentrations further east–hence the odd-sounding stegosaur genera Chialingosaurus, Chungkingosaurus and Tuojiangosaurus. All in all, there are less than two dozen identified stegosaurs, making this one of the rarest types of dinosaur.

Stegosaurus Was Closely Related to Ankylosaurus

Stegosaurus vs Ankylosaurus by SameerPrehistorica

The stegosaurs of the late Jurassic period were cousins of the ankylosaurs (armored dinosaurs), which prospered tens of millions of years later, during the middle to late Cretaceous period. Both of these dinosaur families are grouped under the larger classification of “thyreophorans” (Greek for “shield bearers). Like Stegosaurus, Ankylosaurus was a low-slung, four-footed plant-eater–and, given its armor, even less appetizing in the eyes of ravenous raptors and tyrannosaurs.

Source: www.thoughtco.com

10 Stunning Facts About Herrerasaurus

Wednesday, December 14, 2016

Herrerasaurus skeleton

Dinosaurs are often said to have “ruled” the earth throughout their tenure upon it. Yet, as we’ll see, the boxy-headed Herrerasaurus hailed from a time in which dinos were hardly dominant.

1. IT’S ONE OF THE FOSSIL RECORD’S EARLIEST DINOSAURS

South America may very well be the place where dinosaurs made their grand debut. HerrerasaurusEoraptor, and Panphagia—which rank among the earliest dinos yet unearthed—emerged there roughly 231 million years ago.

2. HERRERASAURUS WAS DISCOVERED BY A GOAT HERDER

Wikimedia Commons

1959 saw Argentinian rancher Victorino Herrera happen upon the fossilized creature that would later be named in his honor.

3. IT HAD A “SLIDING” LOWER JAW

Wikimedia Commons

Helpful joints allowed Herrerasaurus’ lower jawbones to flex about considerably for added leverage while ensnaring its quarrelsome prey.

4. AN IMPORTANT HERRERASAURUS SPECIMEN WAS BRIEFLY IMPOUNDED IN BUENOS AIRES

First known skull, specimen PVSJ 407, and left maxilla PVSJ 053

During the late fifties, when very little was known about this animal, a partial Herrerasaurus skull and skeleton were found by Harvard paleontologist Alfred Romer. Unfortunately, these remains were confiscated by the local authorities and held in their custody for two years until Romer’s institution finally claimed them.

5. HERRERASAURUS DEFIED EASY CATEGORIZATION

Wikimedia Commons

For several years, scientists couldn’t agree about how to classify this odd-looking critter. Some felt that Herrerasaurus was closely akin to the gigantic, long-necked herbivores known as sauropods. Others felt the animal couldn’t even be considered a proper dinosaur at all, but was instead a humble precursor. Today’s general consensus, however, cites Herrerasaurus as a basal theropod (or “meat-eating” dino).

6. IT WALKED IN THE SHADOWS OF SOME MUCH LARGER PREDATORS

Herrerasaurus was somewhere in the ballpark of 12 feet long, yet it would’ve been dwarfed by such non-dinosaurian predators as the 20-foot quadruped Saurosuchus, which also inhabited its territory. Carnivorous dinos wouldn’t start topping food chains until the stage was set by a mass extinction that wiped out these competitors 201 million years ago.

7. HERRERASAURUS ALSO CO-EXISTED WITH SOME WEIRD, MAMMAL-LIKE ANIMALS

Wikimedia Commons

Get ready to meet some distant relatives, folks! Mammals are the last surviving members of a larger group known as the “therapsids.” Though non-mammalian species were largely on the decline when Herrerasaurus came along, fossils from a few varieties have been found in the same deposits as this South American dino.

8. SCIENTISTS HAD TO WAIT FOR NEARLY THREE DECADES BEFORE A DECENT HERRERASAURUS SKELETON SHOWED UP

Jesus Blanco

Before 1988, Herrerasaurus—like many prehistoric creatures—was exclusively known from a smattering of very incomplete specimens.  Thankfully, an American team dug up a reasonably complete Herrerasaurus skeleton that year.

9. HERRERASAURUS WASN’T THE ONLY HERRERASAURID

Staurikosaurus pricei, via Wikimedia Commons

The amazing Herrerisauridae family also includes two other genera: Staurikosaurus of Brazil & Argentina’s Sanjuansaurus.

10. HERRERASAURUS HELPS EXPLAIN THE EVOLUTION OF MODERN BIRD WINGS

Brian Smith

Herrerasaurus’ wrist and lower arm look fairly unusual for a reptile from its period, yet they do crudely resemble those of 21st-century avians. Herrerasaurus forelimbs utilized a similar range of motion, folded up like a modern pigeon’s, and may have even been decorated with lengthy feathers. What we’re almost certainly seeing here, therefore, is an early step down the evolutionary path to bird wings and, eventually, flight.

Source: www.mentalfloss.com

10 Cool Facts About Iguanodon

Wednesday, December 14, 2016

Iguanodon herd

Perhaps more than any other dinosaur, Iguanodon reveals how dramatically our perception of these amazing creatures has evolved—while reminding us how much we’ve yet to learn.

1. IT’S GOT ONE OF THE WORLD’S OLDEST DINOSAUR NAMES.

Our story begins with an eccentric English doctor. The year was 1825. Sussex’s Gideon Mantell had recently obtained a fossilized tooth, one which looked rather strange. Convinced that his specimen belonged to some huge, plant-eating reptile, the physician named it “Iguanodon,” meaning “iguana tooth.” Seventeen years later, anatomist Richard Owen coined the word “Dinosaur”—or “fearfully great reptile”—to classify a trio of newly-unearthed prehistoric creatures: HylaeosaurusMegalosaurus, and Mantell’s Iguanodon.

2. THE ORIGINAL IGUANODON SPECIMEN MAY HAVE ACTUALLY BELONGED TO ANOTHER DINO.

Wikimedia Commons

Today, the Iguanodon genus only contains a single species: Europe’s handsome Iguanodon bernissartensis (pictured above). Nice and simple, right? Well, way back in the 20th century, over a dozen vastly different-looking dinos—spread out across four continents—were lumped together as members of the Iguanodon genus. From a classification standpoint, this was hardly helpful, so scientists started divvying them up during the early 2000s.

Brand new titles such as Mantellisaurus and Dollodon were given to former Iguanodon species. After the dust eventually settled, none but I. bernissartensis remained unaltered. Thickening this plot still further, Mantell’s tooth—the fossil that started it all—might also deserve to be placed in a separate genus.

3.  IGUANODON’S FAMOUS “THUMB SPIKES” WERE ORIGINALLY MISTAKEN FOR NASAL HORNS.

Wikimedia Commons

At first, this long-extinct beast was only known from assorted bits and pieces. Iguanodon snouts, therefore, seemed like as good a place as any for paleontologists to put their conical spikes. When more complete remains started turning up in the 1870s, it was realized that they actually belonged on the sides of their hands.

4. BY THE WAY, SCIENTISTS STILL AREN’T ENTIRELY SURE WHAT THOSE SPIKES WERE USED FOR.

Wikimedia Commons

Iguanodon is often drawn using its thumbs as powerful weapons, heroically jabbing these clawed digits into careless carnivores. But they could have also been employed to tackle less-dramatic errands like breaking open nuts or stripping tree bark. After all, though feeding may lack the glamour of combat, both tasks can force evolution to get inventive.

5. IN 1878, A BELGIAN MINE YIELDED OODLES OF GAME-CHANGING IGUANODON SKELETONS.

Getty Images

That year, two miners unwittingly stumbled on a prehistoric treasure trove over 1000 feet beneath Bernissart, Belgium. Among the fossils their site yielded were 14 beautifully-preserved Iguanodon skeletons, which finally helped paleontologists understand what this majestic animal looked like.

6. IGUANODON APPARENTLY PREFERRED FOUR LEGS TO TWO.

Wikimedia Commons

With such robust torsos and long, powerful arms, chances are adult Iguanodon bernissartensis didn’t spend too much time walking about on their hind limbs; instead, using all fours served as the standard method of transportation. Nevertheless, when life called for a brief two-legged stroll, these animals could have doubtlessly risen to the occasion.

7. IGUANODON HAS HAD A SIZABLE LITERARY IMPACT.

The Lost World, Sir Arthur Conan Doyle’s 1912 epic adventure story, involves herds of Iguanodon roaming the South American wilderness. One comically-oversized specimen trudges through Paris in Nicolas Flammarion’s The World Before Man (1886). And then there’s Raptor Red (1995)—written by maverick paleontologist Robert Bakker—which features a botched Utahraptor attack triggering an Iguanodon stampede.

8. THERE’S A STILL-ORBITING ASTEROID CALLED 9941 IGUANODON.

Wikimedia Commons

On February 4, 1989, a new asteroid was found inside the rocky belt between Mars and Jupiter. In a move that might sound like naming an iceberg after the Titanic (at least, if some popular extinction hypotheses turn out to be correct), NASA subsequently gave it this dinosaurian title.

9. IT’S ON AN ENGLISH COAT OF ARMS.

ngw

In 1834, Mantell received some congregated Iguanodon bones that turned up near the town of Maidstone, which has since honored its paleontological heritage by adding the dino to its official coat of arms.

10. A SUPER-COOL NEW YEAR’S EVE PARTY WAS ONCE THROWN INSIDE AN IGUANODONSCULPTURE.

Wikimedia Commons

As 1854 approached, London’s Crystal Palace saw what was arguably history’s strangest New Year’s Eve celebration. Sculptor Benjamin Waterhouse Hawkins had been commissioned to build a menagerie of full-sized prehistoric creature statues which still captivate visitors today.

Hoping to promote this Victorian Jurassic Park, Hawkins hosted a dinner party in the belly of a partially-completed Iguanodon. On the guest list were 20 great academic figures, including the aforementioned Owen. Ham was served, wine was imbibed, and soon, a cheerful chant rang out: “The Jolly Old Beast is Not Deceased, There’s Life in Him Again!”

Source: www.mentalfloss.com

Saltasaurus

Sunday, December 31, 2017

Segnosaurus

Saltasaurus (which means “lizard from Salta”) is a genus of titanosaurid sauropod dinosaur of the Late Cretaceous Period of Argentina. Small among sauropods, though still heavy by the standards of modern creatures, Saltasaurus was characterized by a short neck and stubby limbs. It was the first genus of sauropod known to possess armour of bony plates embedded in its skin. Such small bony plates, called osteoderms, have since been found on other titanosaurids.

Saltasaurus herd passes Quilmesaurus and Noasaurus

Saltasaurus (which means “lizard from Salta”) was a sauropod dinosaur of the Late Cretaceous Period. Relatively small among sauropods, though still massive by human standards, it was characterized by a diplodocid-like head

The fossils of Saltasaurus were excavated by José Fernando Bonaparte, Martín Vince and Juan C. Leal between 1975 and 1977 at the Estancia “El Brete”. The find was in 1977 reported in the scientific literature.

Saltasaurus was named and described by Bonaparte and Jaime E. Powell in 1980. The type species is Saltasaurus loricatus. Its generic name is derived from Salta Province, the region of north-west Argentina where the first fossils were recovered. The specific name means “protected by small armoured plates” in Latin.

The holotype, PVL 4017-92, was found in a layer of the Lecho Formation dating from the early Maastrichtian stage of the Upper Cretaceous period, about seventy million years old. It consists of a sacrum connected to two ilia. Under the inventory number PVL 4017 over two hundred additional fossils have been catalogued. These include rear skull elements, teeth, vertebrae of the neck, back, hip and tail, parts of the shoulder girdle and the pelvis, and limb bones — plus various pieces of armour. These bones represent a minimum of five individuals, two adults and three juveniles or subadults.

Currently the only recognised species of Saltasaurus is S. loricatus. A S. robustus and a S. australis have been suggested but these are now considered to belong to a separate genus, Neuquensaurus. Earlier, armour plates from the area had been named as Loricosaurus by Friedrich von Huene who assumed them to be from an armoured ankylosaurian. It has been suggested these plates were in fact from Saltasaurus.

The skeleton of the small titanosaur Saltasaurus was protected by large bony scutes imbedded in its skin.

Saltasaurus is very small compared to most other members of the Sauropoda, estimated at 12.8 metres (42 ft) in length and 6.87 tonnes (7.57 short tons) in weight. Powell estimated the adult length at six metres. In 2010, Gregory S. Paul estimated the maximum length at 8.5 metres, the weight at 2.5 tonnes.

Segnosaurus

Sunday, December 11, 2016

Segnosaurus restoration

Segnosaurus (‘slow lizard’) is a genus of herbivorous theropod dinosaur belonging to the Therizinosauridae from the Cretaceous of Mongolia.

Segnosaurus by PrehistoricWildlife.com

Segnosaurus was a rather large therizinosaurid. In 2010 Gregory S. Paul estimated the body length at 6 metres (19.5 ft), the weight at 1.3 tonnes. Segnosaurus had an elongated head, large clawed hands, a somewhat elevated torso, a broad strong pelvis, stocky legs and a short tail.

Segnosaurus can be distinguished from all other therizinosaurs on the basis of two unique derived traits (autapomorphies). The in total forty-eight mandibular teeth are markedly peg-like and only slightly recurved: the front or mesial edge is curved and the back or distal edge is straight. The second autapomorphy is that the claws of the hand are rather flat instead of very narrow. In the same formation the closely related Erlikosaurus is found; Segnosaurus can be distinguished from this species by its moderate transverse compression of the pedal unguals or foot claws. Also the latero-dorsal shelf on the dentary, a flat bone surface at the upper outside of the lower jaw, starts at the fourteenth dentary tooth position and runs backwards for half the length of the lower jaw, unlike the shelf in Erlikosaurus, which starts at the fifth tooth position. This would have indicated that Segnosaurus did not have as extensive ‘cheeks’ as Erlikosaurus is believed to have had.

Segnosaurs For Your Amusement by Qilong

Exactly what use this strange combination of features was to Segnosaurus is widely debated. It has been suggested that it was a plant-eater descended from a meat-eating ancestor or, perhaps, a specialist termite hunter that used its huge claws to rip open termite nests. Alternatively, it may have been a specialist fish-hunting dinosaur, hooking fish out of the water with its claws.

Segnosaurus galbinensis MPC-D 100/80 right hemimandible in (A) lateral, (C) dorsal, and (D) ventral views and (B) left hemimandible in medial view. Source: Wikipedia

Segnosaurus is a relatively new dinosaur, described in 1979, and known only from fragments and isolated bones. This makes it difficult to understand what it was really like. Mongolia and China have produced many unusual theropods, such as Segnosaurus, from late Cretaceous deposits. These groups are not found anywhere else, indicating that what is now central Asia was isolated from the rest of the world by mountains and seas for most of the later Mesozoic era.

Saurolophus

Sunday, December 11, 2016

Restoration of S. osborni Illustration by L. Xing and Y. Liu.

Saurolophus (meaning “lizard crest”) is a genus of large saurolophine hadrosaurid dinosaurs that lived about 70.0–68.5 million years ago, in the Late Cretaceous of North America and Asia; it is one of the few genera of dinosaurs known from multiple continents. It is distinguished by a spike-like crest which projects up and back from the skull. Saurolophus was a herbivorous dinosaur which could move about either bipedally or quadrupedally.

The size of the two Saurolophus species compared to a human

The type species, S. osborni, was described by Barnum Brown in 1912 from Canadian fossils. A second valid species, S. angustirostris, is represented by numerous specimens from Mongolia, and was described by Anatoly Konstantinovich Rozhdestvensky.

S. angustirostris skeleton and skull

Saurolophus is known from material including nearly complete skeletons, giving researchers a clear picture of its bony anatomy. S. osborni, the rarer Albertan species, was around 9.8 m (32 ft) long, with its skull 1.0 m (3.3 ft) long. Its weight is estimated at 1.9 tonnes (2.1 tons). S. angustirostris, the Mongolian species, was larger; the type skeleton is roughly 12 m (39 ft) long, and larger remains are reported. Aside from size, the two species are virtually identical, with differentiation hindered by lack of study.

The most distinctive feature of Saurolophus is its cranial crest, which is present in young individuals, but is smaller. It is long and spike-like and projects upward and backward at about a 45° angle, starting from over the eyes. This crest is often described as solid, but appears to be solid only at the point, with internal chambers that may have had a respiratory and/or heat-regulation function.

Skulls in Moscow Paleontological Museum. Author: Pavel Bochkov

The holotype of S. angustirostris is a skull and postcrania, so the cranium of the species is well-described. Bell et al. re-evaluated the entire species in a 2011 publication with Acta Palaeontologica Polonica. Their description found the skull to be generalized among hadrosaurines, and are much larger than any skulls of S. osborni. The most unusual feature for a hadrosaurine is the long, protruding, solid crest that extends upwards diagonally from the back of the skull roof. Unlike lambeosaurines, the crests are made up completely of the nasal bone. The premaxilla bones make up almost 50% of the entire skull length, and both sides are filled with small holes. Only in adult individuals has the front of the premaxillary contact been fused. Longer than the premaxilla, the nasal bones are the longest in the skull. They make up the entire length of the crest, and are never preserved as fused.

Stegosaurus

Sunday, December 11, 2016

Stegosaurus stenops by cheungchungtat

Stegosaurus is a genus of armored dinosaur. Fossils of this genus date to the Late Jurassic period, where they are found in Kimmeridgian to early Tithonian aged strata, between 155 and 150 million years ago, in the western United States and Portugal. Several species have been classified in the upper Morrison Formation of the western U.S, though only three are universally recognized; S. stenopsS. ungulatus and S. sulcatus. The remains of over 80 individual animals of this genus have been found. Stegosaurus would have lived alongside dinosaurs such as ApatosaurusDiplodocusBrachiosaurusAllosaurus, and Ceratosaurus; the latter two may have been predators of it.

As the archetypal thyreophoran, Stegosaurus is one of the best-known dinosaurs, and has been featured in film, postal stamps, and many other types of media.

Stegosaurus was the first-named genus of the family Stegosauridae. It is the type genus that gives its name to the family. The Stegosauridae are one of two families within the infraorder Stegosauria, with the other being the Huayangosauridae. The infraorder Stegosauria lies within the Thyreophora, or armored dinosaurs, a suborder which also includes the more diverse ankylosaurs. The stegosaurs were a clade of animals similar in appearance, posture, and shape that mainly differed in their array of spikes and plates. Among the closest relatives to Stegosaurus are Wuerhosaurus from China and Kentrosaurus from East Africa.

Stegosaurus by Prehistoric Wildlife

These were a large, heavily built, herbivorous quadrupeds with rounded backs, short fore limbs, long hind limbs, and tails held high in the air. Due to their distinctive combination of broad, upright plates and tail tipped with spikes, Stegosaurus is one of the most recognizable kinds of dinosaur. The function of this array of plates and spikes has been the subject of much speculation among scientists. Today, it is generally agreed that their spikes were most likely used for defense against predators, while their plates may have been used primarily for display, and secondarily for thermoregulatory functions. Stegosaurus had a relatively low brain-to-body mass ratio. It had a short neck and a small head, meaning it most likely ate low-lying bushes and shrubs. One species, Stegosaurus ungulatus, is the largest known of all the stegosaurians (bigger than related dinosaurs such as Kentrosaurus and Huayangosaurus).

Stegosaurus remains were first identified during the “Bone Wars” by Othniel Charles Marsh. The first known skeletons were fragmentary and the bones were scattered, and it would be many years before the true appearance of these animals, including their posture and plate arrangement, became well understood. The name Stegosaurus means “roof lizard” or “covered lizard”, in reference to its bony plates. Despite its popularity in books and film, mounted skeletons of Stegosaurusdid not become a staple of major natural history museums until the mid-20th century, and many museums have had to assemble composite displays from several different specimens due to a lack of complete skeletons.

S. stenops skull cast, Natural History Museum of Utah. Author: Daderot

The most recognizable features of Stegosaurus are its dermal plates, which consisted of between 17 and 22 separate plates and flat spines. These were highly modified osteoderms (bony-cored scales), similar to those seen in crocodiles and many lizards today. They were not directly attached to the animal’s skeleton, instead arising from the skin. The largest plates were found over the hips and could measure up to 60 cm (2.0 ft) wide and 60 cm tall.

In a 2010 review of Stegosaurus species, Peter Galton suggested that the arrangement of the plates on the back may have varied between species, and that the pattern of plates as viewed in profile may have been important for species recognition. Galton noted that the plates in S. stenops have been found articulated in two staggered rows, rather than paired. Fewer S. ungulatus plates have been found, and none articulated, making the arrangement in this species more difficult to determine. However, the type specimen of S. ungulatus preserves two flattened spine-like plates from the tail that are nearly identical in shape and size, but are mirror images of each other, suggesting that at least these were arranged in pairs.

Many of the plates are manifestly chiral and no two plates of the same size and shape have been found for an individual; however plates have been correlated between individuals.

Back plate cast, Museum of the Rockies. Photo by Tim Evanson

Stegosaurus, one of the many dinosaurs first collected and described in the Bone Wars, was originally named by Othniel Charles Marsh in 1877, from remains recovered north of Morrison, Colorado. These first bones became the holotype of Stegosaurus armatus. Marsh initially believed the remains were from an aquatic turtle-like animal, and the basis for its scientific name, ‘roof(ed) lizard’ was due to his early belief that the plates lay flat over the animal’s back, overlapping like the shingles (tiles) on a roof. A wealth of Stegosaurus material was recovered over the next few years, and Marsh published several papers on the genus from 1877 to 1897. In 1878, Edward Drinker Cope named Hypsirhophus discurus, as another stegosaurian based on fragmentary fossils specimens from Cope’s Quarry 3 near the “Cope’s Nipple” site in Garden Park, Colorado. Many later researchers have considered Hypsirhophus to be a synonym of Stegosaurus, though Peter Galton (2010) suggested that it is distinct based on differences in the vertebrae.

Stegosaurus strikes out by palaeoartist Robert Nicholls This artist’s reconstruction shows a Stegosaurus striking a powerful blow to one of its predators, a Ceratosaurus.

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.

Skeletal restoration combining several specimens. By Jaime A. Headden

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.

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).

Pages