Giraffatitan

Type Species: Giraffatitan brancai

Classification: Dinosauria – Saurischia – Sauropoda - Gravisauria - Eusauropoda - Neosauropoda – Macronaria – Titanosauriformes – Brachiosauridae

Time Period: Late Jurassic 

Location: Africa

Diet: Herbivore

Giraffatitan was originally thought to be a species of Brachiosaurus but has since been given freedom to stand on its own. It was one of the largest sauropods of the Late Jurassic, averaging between 72 and 74 feet in length but capable of reaching up to 85 feet snout-to-tail. Its neck, held vertical, reached up to forty feet in length. It had a giraffe-like build (hence its name) with long forelimbs and a long neck. It had chisel-like ‘spatulate’ teeth and the first three toes on its hind feet were clawed. Its distinctive high-crested skull was once thought to be characteristic of the brachiosaurids, to which Giraffatitan originally belonged; however, it’s possible that many brachiosaurs didn’t have this feature, since this feature is known only from African specimens now assigned to Giraffatitan – all this to say that the classic portrayal of Brachiosaurus may actually not represent Brachiosaurus at all, at least as far as the skull design goes. Like other sauropods, Giraffatitan had a sacral enlargement above the hip; scientists of an earlier age thought this housed a ‘second brain,’ given that sauropods had pretty small brains to begin with, but it’s know believed to be the location of glycogen bodies. Giraffatitan likely roamed the sweeping conifer forests of the Tendaguru Formation, avoiding the coastal environments of brackish coastal lakes, ponds, and pools where vegetation would be harder to come by. 

Giraffatitan’s nostrils were once thought to be located on the top of its head, lending earlier scientists to speculate that it was a water-dweller, snorkeling in the burgeoning North Atlantic. However, studies have shown that the water pressure placed on the rib cage would make it extremely difficult for a submerged Giraffatitan to breathe; extended time submerged would undoubtedly lead to drowning. Studies of the skull in 2001 suggested that while the nasal openings in the skull were above the eyes, this didn’t mean that the nostrils wouldn’t emerge at the tip of the snout. In this case, Giraffatitan’s tall ‘crests’ may have housed a fleshy resonating chamber. 

Australodocus

Type Species: Australodocus bohetii

Classification: Dinosauria – Saurischia – Sauropoda - Gravisauria - Eusauropoda - Neosauropoda – Macronaria – Titanosauriformes – Somphospondyli 

Time Period: Late Jurassic 

Location: Africa

Diet: Herbivore

The 56-foot-long and 8800-pound sauropod Australodocus was originally classified as a diplodocid but has since been reclassified as an early titanosauriform, making it more closely related to Brachiosaurus than Diplodocus. Australodocus is currently considered one of the first specimens of the somphospondyls, a sauropod lineage that would give birth in the Cretaceous to the larger-than-life armored titanosaur sauropods. This ‘large-nosed’ macronarian roamed the dense conifer forests of Africa’s Tendaguru Formation, separated to the south of North America by the widening strip of water that would eventually become the Atlantic Ocean. While the Morrison Formation in North America was dominated by diplodocids, the Tendaguru Formation was dominated by macronarians, likely as a result of the different environments. The Morrison was a savannah-like floodplain cut by lakes and rivers that were forested on the peripheries; the Tendaguru, however, was more densely-packed with thick conifer forests. The low-lying foliage of the Morrison was perfect eating for low-browsing diplodocids whereas macronarians with vertically-oriented necks did better with the plentiful trees of the Tendaguru. 

Saurophaganax

Type Species: Saurophaganax maximus

Classification: Dinosauria – Saurischia – Theropoda - Carnosauria – Allosauroidea – Allosauria – Allosauridae

Time Period: Late Jurassic 

Location: North America 

Diet: Carnivore

Saurophaganax was the largest predator of the Morrison Formation, reaching lengths up to 46 feet snout-to-tail, making it twice as large as its more common and contemporary cousin Allosaurus (because of the similarity between these two theropods, some scientists argue that Saurophaganax is actually a larger species of Allosaurus, but those making these claims are currently in the minority). As the chief hunter of Late Jurassic North America, it’s not surprising that its remains have been scant: the larger the predator, and the greater its competition in the environment, the less prevalent it is. Saurophaganax had lots of predatory competition, principally from the smaller (but still large) Allosaurus and Torvosaurus. Saurophaganax likely hunted large sauropods such as Diplodocus and Brachiosaurus; it may have hunted in groups, like many of its contemporaries, but there’s currently no evidence for this. Some scientists believe that it may even have hunted other theropods, as there have been discoveries of Allosaurus bones with teeth marks matching the size of those belonging to Saurophaganax (it’s noteworthy that these same-sized teeth marks have also been found on the remains of the ankylosaur Mymoorapelta). Because of its large size, some paleontologists argue that Saurophaganax would’ve been slow-moving and would’ve leaned more towards scavenging than hunting. This, too, would explain the presence of its teeth marks on the Allosaurus bones. Given its size, it may have relied on smaller predators taking down prey and then moving in to take over the kill-site; even the mighty Allosaurus would think twice before defending its kill against a predator twice its size. 

a Saurophaganax takes a break from being Top Dog

Stokesosaurus

Type Species: Stokesosaurus clevelandi

Classification: Dinosauria – Saurischia – Theropoda – Tetanurae – Coelurosauria – Tyrannosauroidea – Pantyrannosauria - Stokesosauridae

Time Period: Late Jurassic 

Location: North America 

Diet: Carnivore

Stokesosaurus was a medium-sized theropod from the Late Jurassic Morrison Formation of North America. By the Cretaceous Period, tyrannosaurs would be becoming larger-than-life despite austere beginnings in the Jurassic. Stokesosaurus represents the gradual increase of size among the tyrannosaur lineage; while the earliest tyrannosaurs emerged in the Middle Jurassic small and lithe, as the Jurassic progressed they were growing larger. Stokesosaurus graduated from a small-sized predator to a medium-sized one, clocking in at ten to thirteen feet in length. A fleet-footed predator, this tyrannosaur likely hunted Morrison ornithopods such as Camptosaurus and Dryosaurus, perhaps even wrangling with an occasional stegosaur. The larger predators of its environment, such as Allosaurus and Torvosaurus, likely preyed on the much-larger sauropods. 

Fruitadens

Type Species: Fruitadens haagarorum

Classification: Dinosauria - Ornithischia - Heterodontosauridae

Time Period: Late Jurassic 

Location: North America 

Diet: Omnivore

The heterodontosaur Fruitadens is the smallest known heterodontosaur. It’s known from partial skulls and skeletons from at least four individuals of differing biological ages; the presence of these skeletons in the same locale indicate that this heterodontosaur may have travelled in family packs. Young adults grew to around 26 to 30 inches in length and weighed between a pound and a half. Fruitadens had relatively short arms and long feet and shins. The lower jaws had an enlarged canine-like tooth which corresponded to a gap in the upper jaw. Fruitadens also had a small peg-like tooth in front of its canine-like tooth. It had replacement teeth present in the jaws, a unique find among other heterodontosaurs. Its hind limb bones were hollow like those of small theropod dinosaurs. 

Paleontologists believe Fruitadens was an omnivore, and it lived in an environment rich with food for the plucking. It likely prowled the many riverbeds and streams of the savannah-like Morrison Formation, feeding on plant material in addition to snails, clams, crayfish, and insects. Being on the smaller size, it would’ve been wary of running across crocodylomorphs. While large theropod dinosaurs such as Allosaurus, Ceratosaurus, and Torvosaurus lived in the same environment, Fruitadens would’ve likely evaded these predators by running into heavy thickets or hiding in the gallery forests spreading out from rivers and lakes. 

Barosaurus

Type Species: Barosaurus lentus
Classification: Dinosauria – Saurischia – Sauropoda – Gravisauria - Eusauropoda - Neosauropoda - Diplodocoidea – Flagellicaudata – Diplodocidae
Time Period: Late Jurassic
Location: North America
Diet: Herbivore

The North American Barosaurus was one of the largest sauropods of the savannah-like Morrison Formation during the Tithonian Stage of the Late Jurassic. While most individuals were already larger-than-life, clocking in at 82-89 feet in length and weighing between twelve and twenty tons, at least one specimen may have reached up to 157 feet in length with a 49-foot neck. Barosaurus was closely related to the more popular Diplodocus, though it had some significant differences: it had a longer neck, a shorter tail, and its skeleton was less robust than its contemporaneous cousin. Additionally, Barosaurus’ cervical vertebrae were designed in such a way that it had a lot of side-to-side flexibility at the cost of up-and-down flexibility. This indicates it ate by sweeping its neck in crescent-shaped arcs over the low foliage, which would’ve been a perfect feeding method for the savannah-like conditions of the Morrison Formation. While its neck and skull have not been recovered, it’s assumed that, due to its close relationship with Diplodocus, Barosaurus had a whip-like tail and a skull with an elongated, sloping snout with peg-like teeth.

Alcovasaurus

Type Species: Alcovasaurus longispinus

Classification: Dinosauria – Ornithischia – Thyreophora – Stegosauria – Stegosauridae – Dacentrurinae

Time Period: Late Jurassic

Location: North America

Diet: Herbivore

The North American stegosaur Alcovasaurus grew up to eighteen feet in length; this medium-sized stegosaur would’ve been a low browser in prehistoric North America. Its main enemies would’ve included the theropods Allosaurus, Torvosaurus, and perhaps Ceratosaurus. Much of Alcovasaurus’ anatomy is unknown, but because what we do know is similar to the African Kentrosaurus, most reconstructions make it similar to its African contemporary. Alcovasaurus was originally identified as a species of Stegosaurus. This classification was questioned, however, due to five significant anatomical differences, not least its long dermal spikes. Alcovasaurus had two tail spike pairs as its thagomizer that were slender and elongated and ninety percent of the thighbone length. Some scientists argued that these larger spike pairs weren’t indicative of a different species but of sexual dimorphism used for display; perhaps, the argument went, male stegosaurs had flashier thagomizers. Other scientists argued that this stegosaur was less closely related to Stegosaurus and had more affinity with the African Kentrosaurus. Serious studies of this dispute were hampered when the type specimen was damaged by water after a pipe burst at the University of Wyoming; studies couldn’t continue until more specimens were recovered. Recently those scientists who argued for Alcovasaurus being a different genera won out, and Alcovasaurus is now differentiated from its contemporary Stegosaurus.