The Late Jurassic

~  The Oxfordian Stage  ~

163.5 to 157.3 mya

Late Jurassic

The Oxfordian stage is the first stage of the Late Jurassic; it's preceded by the Callovian stage of the Middle Jurassic and followed by the Kimmeridgian stage of the Late Jurassic. The Oxfordian gets is name from the city of Oxford in England. The base of the Oxfordian is the first appearance of the ammonite species Brightia thuouxensis; the top of the Oxfordian stage is the first appearance of the ammonite species Pictonia baylei. Our knowledge of Oxfordian terrestrial organisms is scant, so long as you exclude China from the list. Indeed, recent discoveries of Oxfordian creatures in China - not only dinosaurs, but also mammals and amphibians - have given us a picturesque glance of what life was like during this stage in southern Laurasia.

Throughout the Middle Jurassic, Laurasia suffered tectonic splitting, and by the beginning of the Late Jurassic – about 150 million years ago – Laurasia was almost completely divided between modern-day North America and Eurasia. The waterway between them was the slender, miniscule genesis of the North Atlantic Ocean. Another rift was forming between North America and what would become Greenland (the two would be completely separated by the end of the Jurassic). In western North America, the Sundance Sea had formed during the mid-Jurassic. This was a shallow continental sea that had spread southwards across the Midwest. Late in the mid-Jurassic it began to dry up and retreat northwards, leaving behind a vast plain of sediment laid down by a shifting network of rivers and streams coursing down from the ancestral Rocky Mountains to the west. This was the formation of the Morrison Formation. By the Late Jurassic this valley was semi-arid, but it was so flat and so close to sea level that it was soggy most of the year. Massive lakes swelled and shrank on a seasonal basis; rivers flooded, spreading silt, and then dwindled to mere streams. Trees and permanent flora were confined to the riverbanks, and vast sand dunes stitched the landscape between the accordion-like waterways.

Gondwana, the southern continent, was a little more stable, but rifting was beginning to occur. South America and Africa remained solidly conjoined, but a waterway was forming between the African and Indian plates. By the end of the Late Jurassic and the beginning of the Cretaceous, South America and Africa had broken away from Antarctica and Australia, and India was a large island in the Tethys Sea. Australia and Antarctica would be conjoined until long after the Mesozoic Era; their combined mass helped channel warm water toward Antarctica and kept it from freezing over.

Caribemys, one of the earliest marine turtles

Many marine reptiles continued from the Callovian into the Oxfordian, such as the pliosaurs Simolestes and Liopleurodon, the plesiosaurs Cryptoclidus and Colymbosaurus, and the ichthyosaurs Opthalmosaurus and Nannopterygius. Several species of marine crocodylomorphs flourished, and a new one – the ten-foot-long Cricosaurus – emerged in the waterways among the European archipelagos. There were new marine reptiles, as well. The pliosaur Gallardosaurus prowled the narrow Caribbean Seaway between the north coast of Africa and the south coast of North America. This shallow seaway – between thirty to forty feet deep – was home to plesiosaurs such as Vinialesaurus, ichthyosaurs, the marine turtle Caribemys, and the seafloor was colonized by oysters and algae.

a pair of Tatenectes in the Sundance Sea of North America

In North America, the Sundance Sea had formed during the Middle Jurassic in what is now the western United States, and it was home to a few species of marine reptiles. The Sundance Sea was a shallow epicontinental sea; it connected to the open ocean around modern Yukon Territory in northern Canada, and it spread southwards to New Mexico and eastward to the Dakotas. During the Oxfordian, the Sundance Sa was less than 130 feet deep and home to all sorts of creatures: in addition to a wide array of invertebrates, it was colonized by hybodont sharks and fish. Interestingly, marine reptiles aren’t that common; that isn’t to say they aren’t present, but they weren’t able to flourish (they much preferred the ‘wide open spaces’ of oceans and seas). The most abundant marine reptile of the Sundance Sea is the twenty-foot-long, dolphin-like ichthyosaur Baptanodon, but other inhabitants include the ten-foot-long plesiosaur Tatenectes and the hardly-known plesiosaur Pantosaurus.

the Chinese pterosaur Darwinopterus

Most of our knowledge of Oxfordian pterosaurs comes from China (and this includes the vampirous Jeholopterus). Darwinopterus is an oddball because it has characteristics of both the rhamphorhynchids and the pterodactyls. It was abundant in its environment, and remains of thirty to forty individuals from up to three different species have been discovered. Three species of Darwinopterus are known; each is slightly different, and as they lived in the same environment, they likely practiced niche partitioning. D. modularis, the type species, was designed for catching fish in the lakes and ponds scattered about prehistoric China; D. linglongtaensis may have been insectivorous; and D. modularis may have fed on hard-shelled beetles or even crustaceans.

the pelican-like Liaodactylus, the earliest known filter-feeding pterosaur

Another Chinese pterosaur was Dendrorhynchoides, one of the smallest known pterosaurs with a wingspan of only fifteen inches. It had a long tail and a short, broad skull with recurved teeth. The scientists who studied the original specimen suggested that Dendrorhynchoides lived an arboreal (or tree-dwelling’) lifestyle as an insectivore. A much larger pterosaur was the rhamphorhynchid Sericipterus, which had a wingspan of just under six feet. It had three bony crests: a low crest on the snout, a short low parietal crest on top of the skull and a short traverse crest connected to the front edge of the latter. The parietal crest is the first reported for a non-pterodactyloid pterosaur. The pterodactyloid Kryptodrakon was slightly smaller, with a five-foot wingspan. The most intriguing pterosaur from Oxfordian China was Liaodactylus, the earliest known filter-feeder. It had 150 long, comb-like teeth packed closely together, and it would’ve soared over prehistoric lakes with its lower jaw underwater, ‘filtering’ small prey into its mouth.

Sordes examines a snail

Two more Oxfordian pterosaurs – both from Kazakhstan – are worth mentioning. The rhamphorhynchid Scaphognathus had a short head with a fairly rounded, blunt snout (hence the meaning of its name, ‘tub jaw.’) It had a three-foot wingspan, and its jaws were filled with long, upright, sharp-pointed teeth. The rhamphorhynchid Sordes pilosus’ name means ‘hairy devil,’ and it gets it name from the hairy pycnofibers that coated much of its body. The first fossils were found in 1960, comprising an all but complete skeleton with imprints of soft body parts, including a thick coat of .25-inch-long ‘hair’ over the head and body and a thinner fur on the wings. This discovery helped prompt a revolution in our understanding of pterosaurs, and it’s a foundational specimen to the idea that most if not all pterosaurs had a furry coat. Sordes was a small pterosaur with short, broad wings; its tail didn’t have a diamond-shaped fin like most rhamphorhynchids, but it was flattened and paddle-like at the end. It had an extra set of wing membranes between the two back legs that stretched down to the ankles, leaving the long tail free. Having examined the major Oxfordian creatures of the oceans and skies, we can now begin our exploration of the Oxfordian's terrestrial creatures. We will move in a west-to-east manner, beginning in Gondwana.

the short-necked sauropod Brachytrachelopan

The First Stop: Gondwana. We begin our tour of the Oxfordian landscapes in Gondwana to the west. In Australia we find the fifty-foot-long sauropod Rhoetusaurus, and in South America we come across Tehuelchesaurus, a long-necked camarasaur that was suited for reaching high vegetation. The most interesting of Gondwana’s Oxfordian inhabitants was the short-necked sauropod Brachytrachelopan. This short-necked sauropod from modern Argentina is infamous because its neck is forty percent shorter than other dicraeosaurids of its lineage (quite a feat, given that the dicraeosaurids are known for short necks in comparison to other sauropods!); indeed, Brachytrachelopan has the shortest neck of any known sauropod. Dicraeosaurids in general had a tendency towards short necks, which scientists speculate was due to them being low browsers and specializing on certain food sources. Brachytrachelopan’s cervical neural arches were designed in such a way that they restricted neck movement, so that this sauropod was specialized to a diet of plants about one to two meters off the ground. Such a specialized diet might be a factor in why the dicraeosaurids didn’t reach large sizes. An interesting theory is that the dicraeosaurids of Gondwana dominated the ecological niches that elsewhere belonged to the ornithopods; it’s noteworthy that dicraeosaurids flourished in southern Gondwana but are virtually absent where ornithopods can be found. This may indicate that larger ornithopods and dicraeosaurids were ‘ecological analogs,’ in that they both underwent evolutionary adaptations from different lineages to dominate the same type of ecosystem. Underfoot these Gondwanan sauropods was the fifteen-inch-long crocodylomorph Lisbosaurus (found in Africa, to the east of Brachytrachelopan) and the three-foot-long, narrow-snouted crocodylomorph Batrachomimus (found in nearby Brazil).

Hesperornithoides: the first paravian - and first troodontid - of
the western world

The Second Stop: Northern Laurasia. Our knowledge of North America (northwest Laurasia) in the Oxfordian stage is rather limited (though North America overtakes China as the ‘hot spot’ of Jurassic fossils in the following Kimmeridgian and Tithonian stages of the Late Jurassic). We know that in the earliest part of the Early Jurassic, North America was home to at least two crocodylomorphs, Eutretauranosuchus and Almadasuchus. This latter crocodylomorph has also been found in Gondwana. Almadasuchus was one of the last ‘sphenosuchian’-like crocodylomorphs; by the Cretaceous Period, virtually all crocodylomorphs looked more or less like the crocodilians we know and love today (albeit more ferocious). A noteworthy dinosaur from North America was the fascinating little critter called Hesperornithoides. This theropod was the only known troodontid from the Jurassic Period, the smallest known dinosaur from the Morrison Formation of North America, and the first western paravian – so this little animal has set a lot of records! Hesperornithoides lived in a semi-arid landscape splotched with patches of shallow, standing water dominated by horsetails, ferns, cycads, and conifers (though trees were sparse and far between). It likely hunted small prey. An adult Hesperornithoides grew to about three feet long. It had a well-developed wishbone, large, blade teeth, and a sickle-claw on its hind feet like Velociraptor and Troodon. Though it was probably covered in feathers, it was incapable of flight, as its arms were too short.

the twenty-six-foot-long Metriacanthosaurus

Moving eastwards from North America, we come to the growing North Atlantic. Modern England is a series of wooded islands cut by a shallow sea known as the Oxford Sea. Remains dating to this period include the twenty-six-foot-long Metriacanthosaurus (believed to be closely related to the Chinese Yangchuanosaurus) and the twenty-foot-long Eustreptospondylus. These predators likely prowled the island beaches to scavenge the washed-up bodies of marine reptiles and oceangoing crocodylomorphs; the larger Metriacanthosaurus likely hunted larger dinosaurs such as sauropods and stegosaurs, whereas the smaller Eustreptospondylus may have hunted early ornithopods. Many scientists believe these theropods were capable of swimming, as they would need to move island-to-island to find enough food to sustain their sizes (smaller theropods, we can surmise, could’ve been more localized and fiercely territorial). Moving farther east, we come to modern mainland Europe. France and Germany are cut by inlets and bays of brackish water that support lush mangrove ecosystems; farther inland, dense woodlands are cut by rivers and lakes. The French and German shoreline is farther east than it is today, and much of modern western France and Germany lies under the warm, shallow North Sea; archipelagos dot this shallow sea. The theropod Streptospondylus, similar in size and shape to Eustreptospondylus, hunted among these European archipelagos.

the twenty-foot-long Eustreptospondylus

The Third Stop: China. Our knowledge of the Oxfordian stage of Late Jurassic China is enormous, making our knowledge of the rest of the world of this time look paltry. Three pristine fossil beds have opened windows into what life was like in China during the Oxfordian. These three fossil beds are the Shishugou Formation, the Shaximiao Formation, and the Tiaojishan Formation. We'll begin at the Shishugou Formation in Xinjiang, China. The Shishugou Formation is peculiar in that it’s comprised of ‘traps’ of vertically-stacked skeletons of numerous non-avian theropods in 3-6 foot deep pits. The pits are filled with a mix of alluvial and volcanic mudstone and sandstone, and they appear to have been created by the trampling and wallowing of large dinosaurs. These depressions filled with volcanic ash from nearby erupting volcanoes; the ash rained down into the marshland, creating viscuous mud and becoming death traps. Three of these ‘death pits’ have been found, and in one of them a crocodylomorph was found against a small ceratosaur; in another pit there were three decapitated theropods. Theropods mired in these traps would be easy prey for scavengers, and many were trampled underfoot behemoth sauropods for whom the pits posed no threat. The high quality of specimen preservation indicates that carcasses were buried rapidly, and evidence for scavenging of the bodies is seen in the dispersal of body parts. The area in which these pits existed was largely marshland adjoined by a small volcanic mountain range. The environment was host to all sorts of creatures other than dinosaurs: the formation includes small crocodylomorphs, early amphibians, and pterosaurs such as the five-foot-wingspan head-crested pterodactyloid Kryptodrakon and the even larger long-tailed rhamphorhynchid Sericipterus. 

a snapshot of Xinjiang, China during the Oxfordian stage of the Late Jurassic. Here we see a Yinlong
being pursued by a pack of Guanlong, and a herd of Mamenchisaurus marches in the background

Sauropods in this volcanic marshland included the short-necked, twenty-foot-long Bellusaurus; the fifty-foot-long Klamelisaurus; and a newcomer to the Jurassic, the super-long-necked sauropod Mamenchisaurus. This latter sauropod genera were wildly successful, as numerous species have been identified. They’re remarkable for their extremely long necks which made up half their length and were longer than school buses. The largest species of Mamenchisaurus grew up to 115 feet in length! These were the titans of their environment. Other dinosaurian herbivores of the area included the twenty-foot-long stegosaur Jiangjunosaurus, the basal ornithopod Agilisaurus, and the basal ceratopsian Yinlong. This primitive ceratopsian is one of the oldest known ceratopsians (along with its contemporary Hualianceratops), and it looked more like a heterodontosaur than the Triceratops we all know and love. It was four feet long snout-to-tail and likely weighed only thirty-five pounds. It was a small, bipedal creature that likely traveled in groups. Its skull shares characteristics of both the more derived ceratopsians and the Cretaceous pachycephalosaurs, indicating that these groups indeed share parentage. The fact that Yinlong’s skull looks more like that of a heterodontosaur – minus the mixed teeth array – is curious, for it seems that ceratopsians evolved from creatures more reminiscent of the Jurassic heterodontosaurs. 

a Guanlong closes in on a Yinlong

The skittering Yinlong would’ve been prey for such predators as Guanlong, a ten-foot-long tyrannosauroid theropod that had grasping three-fingered hands (the ‘staple’ two-fingered hands of tyrannosaurs wasn’t a staple until the Cretaceous Period). Guanlong had a distinctive crest made from fused nasal bones. It was thin as a tortilla and just over two inches tall. The crest was filled with air sacs and reminded the discoverers of the ornamental features found on modern cassowaries and hornbills. Its crest was certainly for ornamental display purposes, as it was far more delicate and elaborate than those found in the earlier Jurassic dilophosaurids (in the case of dilophosaurs, the crests were likely for species-recognition and sexual display). Other predatory theropods of the environment included the eighteen-foot-long Monolophosaurus, the ten-foot-long primitive coelurosaur Zuolong, and the twenty-five-foot-long Sinraptor. This latter theropod was the king tyrant of these volcanic marshlands. 

an adult Limusaurus watches over its young

Not all the theropods at Shishugou were bloodthirsty predators, however. It’s in the Late Jurassic that we begin to see the theropod lineage beginning to take some weird twists and turns, derailing from the typical theropod blueprint of claws and teeth and blood in the gullet. Two theropods in this environment adopted ‘unconventional’ lifestyles. The first, Limusaurus, was a slender dinosaur that reached six feet long in adulthood. It had a long neck, long legs, and very small three-fingered hands. Many specimens of varying ages have been uncovered, and they showcase a fascinating morphological change that took place as the juveniles reached adulthood. Juvenile Limusaurus had teeth and were likely hunters; but as they reached adulthood, they lost their teeth and developed beaks, becoming herbivorous! The other ‘oddball’ at Shishugou was the theropod Haplocheirus. This was the earliest known alvarezsaur. The alvarezsaurs were strange little theropods, and they’re identified by their strange hand morphology in which all digits but the thumb were reduced. More derived alvarezsaurs had large, clawed thumbs that seem designed for digging. Because of their small size and peculiar hand morphology, scientists believe they were insectivores that used their thumb claws to search for grub behind tree bark. Another theory is that they used their claws to break into ant and termite colonies. This insectivorous nature is bolstered by their long, elongated snout and small teeth. Haplocheirus, as a basal alvarezsaur, retained two more functional fingers, giving it a three-digit claw, that would’ve enabled it to seize prey. This theropod had long legs and was likely a fast runner. It would need to be, for it lived in an environment with much larger predators than itself – such as Sinraptor – that might find a little Haplocheirus to be a tasty treat.

a Shunosaurus defends against a Yangchuanosaurus

Leaving the Shishugou Formation behind, we travel three thousand miles southeast to reach the Shaximiao Formation in Sichuan, China. This bone-bed was once a lush forest surrounding a lake that was fed by a large river. Animal remains from the river would’ve been swept by the river’s current into the lake, where they were deposited and, in time, fossilized. Hundreds of dinosaur specimens have been uncovered from this haunting lakeside environment, along with the remains of several species of Late Jurassic turtles and several tritylodonts (these were medium-sized mammal-like cynodonts, the last family of the non-mammalian synapsids. The crocodylomorphs Hsisosuchis and Sunosuchus prowled the river and lakeshore, and the rhamphorhynchid Angustinaripterus flew overhead. Primitive ornithischians such as Agilisaurus, Hexinlusaurus, Yandusaurus, and Gongbusaurus skittered through the underbrush, overshadowed by the conifer tree canopies – and the lakeside rumbled with the heavy footfalls of massive sauropods. Sauropods in this environment included the superbly-long-necked Mamenchisaurus, whom we met at the Shishugou Formation, as well as the sixty-six-foot-long Omeisaurus, the fifty-foot-long Datousaurus, and one of the earliest brachiosaurids, Daanosaurus. Perhaps the most intriguing sauropod of the Shaximiao Formation is Shunosaurus. This sauropod is famous for the ankylosaur-like club on its tail. The ‘club’ was composed of a cluster of two-inch long conical osteoderms, and it was likely used to exact crushing blows to attacking predators or between rival males ‘squaring off’ for the right to the pluckiest females. Shunosaurus composes ninety percent of the fossils in the Dashanpu fossil beds (a segment of the Shaximiao Formation), so it was undoubtedly a successful dinosaur. This was a rather small sauropod, stretching only thirty feet long snout-to-tail and weighing in at just over three tons. It was one of the shortest-necked sauropods (bested only by Brachytrachelopan), so it was likely a low browser who swept its neck in wide arcs before taking a few plodding steps forward to eat another crescent-moon shaped swathe of vegetation.

a Gigantspinosaurus defends against a Yangchuanosaurus

The Shaximiao Formation may have a wealth of sauropods, but it’s better known for its multiple genera of stegosaurs. The stegosaurs emerged earlier in the Jurassic, but it wasn’t until the Late Jurassic that they started to bloom – and it seems they loved this lakeside environment in China. At least five different stegosaur genera are known from this locale, with possible others yet to be classified. Most of these stegosaurs were small-sized, ranging around fifteen feet in length, with the largest being the twenty-three-foot-long Tuojiangosaurus. All these stegosaurs – with the exception of Tuojiangosaurus – had shoulder or hip spikes. Gigantspinosaurus had some of the largest shoulder spikes ever discovered; they were twice the length of its shoulder blades and far larger than the later African Kentrosaurus. Tuojiangosaurus’ absence of shoulder spikes belays its less primitive status, as primitive stegosaurs had a mix of plates and spikes. Nevertheless, Tuojiangosaurus’ relatively early origins are evident in that it retains plate-like spikes on its back over the hips. This stegosaur was on the move from primitive stegosaur attributes to the more derived ones seen later in the Jurassic. All stegosaurs had thagomizers, tail spikes used as defensive weapons. Chungkingosaurus’ tail spikes consisted of two pairs of obliquely vertical stout spikes. It may have had a third pair towards the front of the back two pairs that was present when the specimen was discovered but lost during the excavation. A unique feature of its thagomizer was an additional pair of spikes at the very end of the tail; these were long, thin spikes oriented horizontally, given the thagomizer a ‘pin-cushion’ spike array. Stegosaurs were content to plod through the forest, either alone or in family groupings, eating cycads and ferns, but their thagomizers came in handy against predators such as the thirteen-foot-long Gasosaurus and the thirty-five-foot-long Yangchuanosaurus.

Moving 2600 miles northeast of the Shaximiao bone-beds, we come to the most intriguing bone-bed of Oxfordian China: the Tiaojishan Formation of Liaoning, China. This environment enjoyed a subtropical to temperate climate that was warm and humid. This craggy, mountainous landscape was overshadowed by brooding volcanoes that had a penchant for erupting, and the area was cut by mountain streams and deep sapphire lakes choked by dense gymnosperm forests. The jungle-like forest consisted of ginkgoes and conifers, lycopsids and horsetails, cycads and ferns. Many creatures called this place home: small feathered dinosaurs, numerous pterosaurs, salamanders and insects and arachnids. There were early mammals – including the earliest gliding mammal Volaticotherium and an aquatic protomammal Castorocauda.

the beaver-like Castorocauda of the Oxfordian stage Tiaojishan Formation

the flying mammal Volaticotherium 

Interestingly, there are no ‘large’ animals present in the fossilized record of the Tiaojishan Formation.Though we know that southern Laurasia was host to large dinosaurs – for other Chinese bone-beds have preserved sauropods, stegosaurs, early ornithopods and ceratopsians, and medium- to large-sized theropods – there are none present in this part of China (the largest creature preserved at Tiaojishan is the two-foot-long heterodontosaur Tianyulong!). Researchers have posited two theories to explain the absence of larger organisms. The first explanation is that maybe these larger creatures simply didn’t live in this environment. Maybe the mountainous terrain was too difficult to navigate, or maybe the jungle-like forest, lush from the common nutrient-rich volcanic eruptions, was too difficult for larger animals to penetrate? These factors would be no match for smaller animals such as the panoply of paravian dinosaurs, pterosaurs, amphibians, and mammals that Tiaojishan does preserve. Another explanation is that larger dinosaurs were present in the environment, but they escaped the periodic volcanic eruptions that deposited fine dust and ash. The exquisite preservation of the Tiaojishan fossils is due to the unique volcanic sedimentary rock in which they’re preserved; this has allowed us to examine them closely and see features – such as feathers – that are usually destroyed. That these animals were entombed in volcanic ash is a given. Perhaps when the volcanoes erupted, the larger organisms – the stegosaurs, sauropods, and larger theropods – were able to flee, whereas smaller animals were doomed and buried quickly as the ash layer built up. Marine organisms would be choked as the waterways and lakes turned to ashen mush; extreme heat and volatile air currents would damage pterosaur membranes or send them careening to the ground; and the ash would cake the feathers of the feathered paravians, weighing them down and consigning them to their deaths. In a very real way, the Tiaojishan Formation may be a series of snapshots of recurring Oxfordian apocalypses.

a pair of Tianyulong in the jungle-like forests of the Tiaojishan Formation

Perhaps the most remarkable discoveries of the Tiaojishan Formation are the panoply of paravians (early 'dino-birds' closely related to the Aves, or 'true birds'). For decades it was believed that the Late Jurassic Archaeopteryx was the 'first link' in the dino-bird connection, but the paravians of Tiaojishan predate Archaeopteryx by ten million years; even more surprising is that most of these paravians are even more advanced (i.e. more morphologically similar to Aves) than Archaeopteryx. This indicates that paravian evolution began millions of years before Archaeopteryx came onto the scene, and Archaeopteryx can be viewed as an 'outlier' who was 'behind the times.' Even the paravians of the Oxfordian are predated by other paravians, such as the Middle Jurassic Serikornis (represented at Tiaojishan) and possibly even the Late Triassic Protoavis. Most of the paravians of Tiaojishan were arboreal (tree-dwelling) gliders incapable of powered flight. It's likely they spent almost all their times in trees, climbing trunks, gliding branch-to-branch, building nests to raise their young, and feeding on small lizards and insects. Some were likely ground-dwellers incapable of living in trees. Below are two collages with just a handful of the paravians represented from the Oxfordian beds of Tiaojishan.

clockwise from upper left: Xiaotingia, Anchiornis, Aurornis, and Caihong

clockwise from upper left: Epidexipteryx, Pedopenna, Scansoriopteryx, and Yi

~  The Kimmeridgian Stage  ~

157.3 to 152.1 mya

Late Jurassic

The Kimmeridgian stage is the second stage of the Late Jurassic; it's preceded by the Oxfordian stage and followed by the Tithonian stage. The Kimmeridgian takes its name from the English village of Kimmeridge on the Dorset coast. The base of the Kimmeridgian is the appearance of the ammonite species Pitconia baylei, and the top of the Kimmeridgian is the first appearance of the ammonite species Hybonoticeras hybonotum. Much of our knowledge of the Kimmeridgian stage is relegated to the Morrison Formation of the western United States; unlike the Oxfordian stage, China has no exquisite bonebeds for us to sift through. It's during the Kimmeridgian that many of the infamous dinosaurs appeared: the theropods Allosaurus and Ceratosaurus; the sauropods Apatosaurus, Brachiosaurus, and Diplodocus; the stegosaur Stegosaurus; and we find some of the earliest ankylosaurs, Gargoyleosaurus and Mymoorapelta. 

We begin our exploration of the Kimmeridgian Stage in the oceans. The pliosaur Gallardosaurus continued plowing the burgeoning Caribbean, and the ichthyosaur Acuetzpalin roamed the seas off modern-day Mexico. In the shallow Oxfordian Sea of prehistoric Europe, several marine reptiles continued from the Oxfordian: the ichthyosaur Nannopterygius, the plesiosaur Colymbosaurus, and the pliosaur Simolestes. A few new marine reptiles appeared: the plesiosaur Bathyspondylus from England, the ichthyosaur Grendelius from England and Russia, and the prominent ichthyosaur Brachypterygius. This latter ichthyosaur was large, with a skull length of over three feet, and is known for the width and shortness of its fore-paddles. In North America the Sundance Sea was retreating, but it had yet to disappear completely; despite its shrinking size, it continued to host a variety of marine reptiles such the plesiosaurs Pantosaurus and Tatenectes. The latter was small for a plesiosaur, only nine to twelve feet in length. The dolphin-like ichthyosaur Baptanodon continued to thrive, and the top of the apex food chain was secured by the pliosaur Megalneusaurus, which could grow up to thirty-two feet in length. In the image to the left, a Megalneusaurus interrupts a party of Tatenectes.  

Marine crocodylomorphs – the thallatosuchians – underwent wide variation in the Kimmeridgian. The metriorhynchids Cricosaurus and Purranisaurus continued from the Oxfordian, and a new metriorhynchid, Torvoneustes, appeared in global distribution, its remains being found in both England and Mexico. Torvoneustes had a long snout with smaller-sized teeth and is viewed as a transitional form between long-snouted, fish-eating metriorhynchids and the hyper-carnivorous, short-snouted metriorhynchids like Dakosaurus (pictured to the right). The ‘Biter Lizard’ Dakosaurus appeared during the Kimmeridgian and was quite prolific, known from England, France, Switzerland, Germany, Poland, Russia, Argentina, and Mexico (though popular during the Kimmeridgian, some scientists believe it actually emerged in the Oxfordian, due to teeth attributed to this creature being found in Oxfordian deposits). Dakosaurus had a short snout with serrated teeth and grew up to sixteen feet in length; it had a streamlined body designed for hydrodynamic efficiency; and its finned tail made it a better swimmer than modern crocodilians. The skulls of the Mexican specimens preserve what looks to be a chamber in which salt glands – which could excrete excess salts – could be housed; the presence of salt glands implied that it was likely fully aquatic, spending all of its time in the ocean. It was probably the apex predator of its day: its teeth resemble those of modern whales, and the enlarged fenestrae of its skulls were designed to anchor large muscles to give it a powerful bite. Dakosaurus' triangular-shaped skull, the design of its jaw muscles, and its deeply-rooted, serrated teeth indicate that it probably fed by twist feeding, in which it tore chunks out of its prey. In the prehistoric seas of modern Europe, the metriorhynchids Metriorhynchus and Gracilineustes continued hunting alongside the newly-arrived Aggiosaurus and Plesiosuchus. An interesting newcomer was Bathysuchus, a teleosaurid from both England and France. It was designed more for deep ocean living with smoother skull bones and reduced armor plating. Scientists speculate that this adaptation was prompted by rising sea levels, as Bathysuchus’ earlier relatives – such as Teleosaurus – were more adapted for shallow coasts and lagoon environments. 

Having examined the oceans, now we take to the skies, beginning first in the south, where the anurognathid pterosaur Batrachognathus flitted about the skies. This small pterosaur had a twenty-inch wingspan and a skull just under two inches long. Its skull was high, short, and broad, and its jaws were crammed with over twenty recurved conical teeth; the shape of its jaws gave it a short but wide mouth. In Germany we find the rhamphorhynchid Scaphognathus, which had a three-foot wingspan. In France the pterodactyloid Normannognathus (pictured to the left) took to the skies; this pterosaur had a strange crest on its head, which abruptly jutted out from its upper jaws and formed a crested wave. In England we find the pterodactyloid Cuspicephalus, which had a vertically-directed crest. In southern Gondwana, a number of pterosaurs have dated from the Kimmeridgian: in modern-day Cuba flew two ramphorynchids, Nesodactylus and Cacibupteryx; the latter was relatively large, given its seven-inch-long skull. In eastern Africa the large pterodactyloid Tendaguripterus made its home, and its forty-inch wingspan would’ve cast shadows across the Tendagu Formation.

In northern Gondwana we reach the Morrison Formation of the western United States. This formation has been a hot-bed of bone-beds dating to the Kimmeridgian and Tithonian stages, and it’s revealed a wealth of pterosaur specimens. These pterosaurs were significantly larger than those found throughout the rest of the world at the time. While the four-foot wingspan of Utahdactylus already outranks many other pterosaurs in the wider world, this pterosaur is outdone by the eight-foot wingspans of Comodactylus, Kepodactylus, and Harpactognathus. This latter pterosaur (pictured to the right) had a low bony crest that ran all the way to the tip of its beak, an unusual feature among pterodactyloids. Scientists speculate that it was an aerial predator among the Morrison’s inland freshwater habitats, feeding on fish in the many freshwater streams, ponds, and lakes; others argue that because it lacks the specialization usually seen in fish-hunting pterosaurs, it probably preyed on small land-dwelling animals or hunted smaller pterosaurs or early birds. We will dwell in its habitat in our first stop of our globe-trotting journey across Kimmeridgian planet earth. 

The First Stop: North America. Our continent-hopping journey in the Kimmeridgian Period begins not in South America or Asia but in the Kimmeridgian hotspot of North America. Our knowledge of terrestrial life during this period is dominated by the Morrison Formation of western North America. Radiometric dating puts the age of the Morrison Formation and its associated fossil-beds to between 156 and 146 million years ago, safely nestled in the Late Jurassic and including the late Oxfordian stage, the Kimmeridgian stage, and the early Tithonian stage of the period. The Morrison Formation was a semiarid environment with distinct wet and dry seasons. The Morrison Basin stretched from New Mexico to Alberta and Saskatchewan, and it was a result of the retreating Sundance Sea, which had dominated the western United States during the Middle Jurassic and stretched as far north as the Arctic Sea. As the Sundance Sea retreated during the Oxfordian Stage, the previous sea beds became plains of sediment laid down by shifting networks of rivers and streams flowing down from the emerging Rocky Mountains. The rock fragments that washed off this mountain range were brought down to the sea and were deposited to form broad deltas and well-watered plains. The sand, silt, mud and pebbles that formed the soil of this plain are now a vast swathe of sandstone and mudstone that stretches from New Mexico far north into Canada. These rocks comprise the Morrison Formation. The Morrison Formation was a semiarid environment with distinct wet and dry seasons. Scientists have postulated that wintertime temperatures averaged around 68 degrees Fahrenheit with summer temperatures averaging between 104 and 113 degrees. It was bordered to the west by the newly-thrust Rocky Mountains, and in the lowlands were swampy backwaters, lakeside resorts, river channels, countless streams and gulleys, and fern-savannah foodplains. 

the retreating Sundance Sea was the death-knell for many of its citizens

The Morrison environments were dominated by herbivorous sauropods such as Camarasaurus, Brachiosaurus, Apatosaurus, and Diplodocus. The largest known sauropod of the environment was Supersaurus, which could grow up to 120 feet in length. Other herbivorous dinosaurs included the plated stegosaurs Stegosaurus and the slightly smaller Hesperosaurus, as well as ornithopods such as Camptosaurus and Dryosaurus. The small Dryosaurus likely stuck to deep conifer forests, roaming the woodlands like modern-day deer, safe from larger predators in the inaccessible undergrowth. Two of the earliest ankylosaurs - Mymoorapelta and Garloyleosaurus - also appear in the Morrison Formation. These were nodosaurs, so while they enjoyed the classic ankylosaur armor, they lacked the mace-like tail-bones in more developed ankylosaurs. 

a scene from the Morrison: a pair of Camptosaurus in the foreground, followed by
a pair of Brachiosaurus, and then a pair of Camarasaurus

The top predator of this environment was the thirty-five-foot-long Allosaurus (pictured on the left), which accounts for nearly seventy-five percent of theropod specimens and which may have hunted in packs; other large predators include Torvosaurus and the slightly smaller Ceratosaurus. Scientists ponder how these three alpha predators coexisted, and one idea is that they all practiced a sort of niche partitioning: whereas Allosaurus prowled sauropod herds among the floodplains and attacked the young, weak, or stragglers in packs, Torvosaurus may have been a solitary hunter prowling the forests and waterways; as for Ceratosaurus, it seems more likely than not that it was a semi-aquatic predator who mainly stuck to the numerous rivers, ponds, and lakes. Smaller theropods, such as Coelurus and Ornitholestes, likely hunted lizards, early mammals, or may have even worked in groups to bring down medium-sized prey such as Dryosaurus or Othnielia. Non-dinosaurian organisms included ray-finned fishes, frogs, salamanders, turtles, lizards, and terrestrial and aquatic crocodylomorphs. The semi-aquatic crocodylomorph Eutretauranosuchus grew up to six feet in length and was carnivorous, likely feeding upon fish, small reptiles, early mammals, and unwary dinosaurs. Fossilized flora of the Morrison Formation includes green algae, fungi, mosses, horsetails, cycads, ginkgoes, and conifers. The Morrison Formation was a wide tract of territory with sub-environments that included river-lined forests of tree ferns and ferns (called ‘gallery forests’); swampy ‘backwaters’; lakeside ‘resorts’; and fern savannas with occasional trees such as the Araucaria-like conifer Brachyphyllum.

a Ceratosaurus prowling a lake of the Morrison Formation

The Second Stop: Europe. Moving eastward on our journey, we cross a growing channel of seawater that will one day become the Atlantic Ocean and thus reach modern Europe. Many of the creatures found in Kimmeridgian Europe bear striking resemblance to those found in modern North America, but this isn't surprising. The burgeoning Atlantic was a shallow seaway, and it was dotted by low-lying islands and perhaps even land bridges that allowed cross-continental travel. Two theropods of the Morrison Formation - Torvosaurus and Allosaurus - are represented in Europe, and Eustreptospondylus continued island-hopping as it prowled the beaches of the Oxford Sea. The European stegosaur Dacentrurus resembled the North American Stegosaurus, though there were differences in their plate armor. The German sauropod Europasaurus (pictured to the left) was a tiny sauropod that, in adulthood, reached only twenty feet in length, stood as tall as an eight-year-old human at the hips, and whose head reached only ten feet above the ground. Its small size has been attributed to ‘insular dwarfism,’ in which animals evolve to shrink in size in order to cope with diminished resources. In contrast to Europasaurus was the one-hundred-foot-long Turiasaurus, which thundered through the wooded islands of what is now eastern Spain, eating tough plant matter like leaves, stems, and shoots. Its teeth were heart-shaped and covered in a wrinkled enamel that would’ve helped it grind up tough plant matter. 

the large Spanish sauropod Turiasaurus

Several crocodylomorphs co-existed with the European dinosaurs of the Kimmeridgian. In France, the fossilized remains of Crocodilaemus were discovered in what would've been the bottom of a lagoon enclosed by reefs, evidence of the shallow tropical sea that covered much of western Europe at the time. Northwards in Germany, the remains of Alligatorellus showed up in a marine environment where the crocodylomorph may have been washed into a lagoon. An interesting find in France is Atoposaurus, a small crocodylomorph - only six and a half inches long! - that lacked the bony scutes common on crocodylomorphs; one explanation for this odd find is that it's actually an infantile specimen of Alligatorellus. In both Europe and Africa lived Goniopholis, a semi-aquatic crocodylomorph that ranged between seven and thirteen feet in length. It likely embraced a lifestyle similar to that of the modern American alligator or Nile crocodile. 

the semi-aquatic Goniopholis, found in both Europe and Africa

The Third Stop: Peripheries

Our next stop in our globe-trotting journey through the Kimmeridgian is modern Africa. At this point in history, Africa lie directly southeast of North America and was separated by a channel of water that would, in time, become the middle Atlantic Ocean. Because of its close proximity to North America, many of the north African organisms resembled those of the Morrison Formation. The small-sized diplodocid Dicraeosaurus (pictured to the left) had a ridged back of fleshy skin created by branched neural backbone spines; in life this may have created a 'fan' running along its back (a feature prominent in the later Amargasaurus). Some scientists believe these were bony anchors for a thin, low, sail-like structure. The sail would’ve made it look bigger in profile as a deterrent to predators; or it may have served as a display for species recognition or attracting mates, in which case it was likely brightly colored or vibrantly patterned; another theory is that the sail would’ve served for thermoregulation. In the latter case, the large area of the sail, when positioned at a right angle to the rising sun, would’ve absorbed warmth and passed it, via the blood flowing through it, into the animal’s system. This would quickly raise the animal’s body temperature to allow more and faster activity after the cool of night; conversely, standing in the shade and at a right angle to the breeze would cool the body. 

Two African theropods have been dated to this time. The thirty- to forty-foot-long Veterupristisaurus stalked the muddy banks of a lagoon in Late Jurassic east Africa. Though it’s already noteworthy for being so large – undoubtedly the top predator in its environment – some scholars believe the remains we have actually belong to a juvenile, which would make Veterupristisaurus even larger in adulthood! The other theropod, Elaphrosaurus, has been a seat of debate: because it lacks a head, scientists aren't sure of its diet, and some believe it was carnivorous, others omnivorous, and a few have even speculated that it was one of the rare herbivorous theropods. Elaphrosaurus was twenty feet long with slim, long legs; slender forelimbs with three digits each; a lightweight, shallow-chested body; a long, stiff tail; and a long, relatively stiff neck. This was the shortest theropod dinosaur in stature, at least when you go by the height of the hips compared to the creature’s overall length. In the image above to the right, a flock of Elaphrosaurus scurry among the legs of a nondescript sauropod.

Kimmeridgian bonebeds in China are scant, especially when compared to those of the Oxfordian; nonetheless we know that the sauropod Mamenchisaurus continued into the Kimmeridgian and lived alongside the sixteen-foot-long stegosaur Yingshanosaurus, which had broad, flat, wing-like spines on its shoulders. In the image to the left, a pair of Yingshanosaurus is portrayed in a Chinese forest with an indeterminate theropod giving them an evil eye. The crocodylomorph Sunosuchus - discovered in China, Krygyzstan, and Thailand - appeared during the Kimmeridgian and lasted through the Early Cretaceous. Sunosuchus had a long, narrow snout and a small skull table. Sunosuchus lived in an estuarine environment populated with temnospondyl amphibians, turtles, and hybodont sharks. 

the Kimmeridgian Sunosuchus from middle and southern Laurasia

~  The Tithonian Stage  ~

152.1 to 145 mya

Late Jurassic

The Tithonian stage of the Late Jurassic is the last stage of the Jurassic Period, as it is followed by the Berriasian stage of the Early Cretaceous. This stage gets its name from Greek mythology: Tithonus was the son of Laomedon of Troy and fell in love with Eos, the Greek goddess of dawn. Because the TIthonian finds itself hand-in-glove with the dawn of the Cretaceous, Albert Oppel named it after Tithonus. The base of the Tithonian stage is the first appearance of the ammonite Hybonoticeras hybonotum; the top of the stage is the first appearance of the species Calpionella alpina. ?????

The Tithonian oceans saw the continued thriving of many marine reptiles: the ichthyosaurs Grendelius, Brachypterygius, and Nannonpterygius; the plesiosaur Colymbosaurus, and the pliosaur Simolestes. A new plesiosaur, Kimmerosaurus, emerged in England, alongside the ichthyosaurs Aegirosaurus and Cryopterygius. Aegirosaurus was a small ichthyosaur, with adults growing only to about six and a half feet in length; Cryopterygius, on the other hand, could grow up to eighteen feet in length. Few marine reptiles are known from North America’s Sundance Sea, but this isn’t surprising, as it was dwindling down to nothing with the rise of the Rocky Mountains. 

Many thallatosuchians – such as Gracilineustes, Cricosaurus, Purranisaurus, Torvoneustes, Bathysuchus, Aggiosaurus, and Plesiosuchus continued into the Tithonian. The oceangoing tyrant Dakosaurus also continued into the Tithonian, but he had competition from another seagoing crocodilian named Geosaurus. In the image to the left, a Dakosaurus overshadows a Geosaurus. Geosaurus spent most if not all of its time in the open ocean, and though smaller than Dakosaurus, it had a similar appearance with a relatively short skull and curved teeth designed for slashing into prey. Scientists believe Dakosaurus and Geosaurus competed as the top predators of the Tithonian oceans, and they coexisted alongside Cricosaurus and Rhacheosaurus, the former of which fed primarily on fish and the latter of which may have specialized in hunting small prey. Of particular note in the Tithonian is the teleosaurid Machimosaurus, which has been discovered in multiple places in Europe. It was the largest known crocodilian of the Late Jurassic, dwarfing even Dakosaurus at twenty-two feet in length. It’s believed to have lived in the open seas, swimming by lateral undulations of the tail with its limbs used for steering and balancing. It skeletal anatomy enabled it to be a superb diver. The design of its teeth suggests that it fed primarily on turtles, as they were designed for seizing and crushing hard prey. Indeed, many turtle fossils from northern Switzerland have bite marks matching the teeth of Machimosaurus. Bite marks on the Late Jurassic sauropod Cetiosauriscus from Switzerland also match Machimosaurus’ teeth; whether this is from the crocodilian scavenging the sauropod corpse or from active hunting from the water’s edge like modern crocodiles is unknown.  

the twenty-two-foot-long teleosaurid Machimosaurus

The Tithonian witnessed a flurry of new pterodactyloid pterosaurs emerging in Europe, such as Diopecephalus, Plataleorhynchus, Aerodactylus, Ardeadactylus, Aurorazhdarcho, Cycnorhamphus, and Germanodactylus. This latter pterosaur had a 4’4” wingspan, and atop its skull was a low, horn-covered, bony crest that ran from the forehead halfway down the beak. It may have roosted hanging upside-down by its toes, like a bat. It had a long, narrow beak with few or no teeth. As pterodactyloids evolved, they consistently shed teeth, and the question is, 'Why?' One theory is that they did so because teeth added to the weight that hindered flight (this is thought to be the reason modern birds, descended from avian dinosaurs, eventually shed their teeth). Though Germanodactylus retained a few short, peg-like teeth in the back of its jaws, the front of its beak was toothless, tapering to a horn-covered tip. Ctenochasma (pictured to the right), a filter-feeder from both France and Germany, had jaws containing more than 250 fine needle-like teeth that fanned upwards at the tip. Hatchlings possessed sixty, and they grew the rest as they reached adulthood. Ctenochasma embraced filter-feeding as it skimmed over shallow ponds and caught invertebrate larvae and crustaceans in its bristles. Two species of Ctenochasma have been named, one with a crest that likely served as a display structure. The crest was lightweight and made of porous bone. 

A third prominent European pterosaur was Anurognathus. It had a shortened tail like the pterodactyloids that resembled the fleshy bump of a bird’s tail (called a pygostyl or ‘parson’s nose’). Anurognathus was small and slender with a body the size of a human finger. Its wings were long and slim, giving it a twenty-inch wingspan, and its tiny skull was just an inch-long and formed of bony struts with gaping fenestrae for lightness. The head was deep with a wide, frog-like mouth filled with pin-sized teeth designed for crushing and grinding insect exoskeletons. These teeth suggest a diet of insects caught ‘on the wing,’ in a manner similar to today’s swift or swallow. 

Two more Tithonian pterosaurs are worthy of note, both of which have been found in Laurasia (modern Europe) and Gondwana (Africa). The first is the rhamphorhynchid namesake, Ramphorhynchus. It's ironic that the namesake for the long-tailed, short-headed pterosaurs is one of the last of its kind, emerging in the midst of the rhamphorhynchid decline and the pterodactyloid ascent. Rhamphorhynchus' name means ‘beak-snout’ because of its long, narrow, pointed beak. Its fang-like teeth stuck out at all angles from the sides of the jaw, and these teeth were ideal for spearing and trapping fish. It likely skimmed its beak through the water, snapping it shut the instant a fish touched its mouth. Scientists believe it may have had a pelican-like throat pouch for holding its prey. Its pescetarian lifestyle is attested to by fish remains found in the crop and stomach of some specimens. Rhamphorhynchus had an eight-inch-long head and a long tail. Its broad, strong breastbone carried a forward-pointing crest giving wide attachments for wing muscles. Its neck was short and compact, holding the head straight out rather than at an angle as with modern birds. Its wings were stiffened with fine struts of gristle that radiated from the arm bones in the same pattern as a bird’s flight feathers. 

The second infamous Tithonian pterosaur with worldwide distribution was none other than Pterodactylus, the namesake for the long-snouted, short-tailed pterosaurs. Though Pterodactylus first emerged during the Oxfordian stage of the Late Jurassic around 160 million years ago, it reached its dominance during the Tithonian, and it survived until the Early Cretaceous 130 million years ago. Multiple species of Pterodactylus have been identified, and though they have linking features indicating they aren’t separate genera, the divergences are vast. Some species were as small as a modern blackbird with wings just twelve inches across; others were giants of their day with an eight-foot wingspan. Pterodactyls – referring here to the variant species of Pterodactylus rather than to the wider ‘family lineage’ of the pterodactyloids – had very short tails and lengthened necks that joined at the base of the skull. Their skulls were thin and light with large weight-saving fenestrae. The main wing membranes attached to the upper leg and upper part of the lower leg, and they had no ‘tail’ membrane between the back legs. The wings were long and narrow due to the elongated hand bones near the wing claws. Pterodactyls had a small, extra flap of wings at the front between wrist and shoulder, called the propatagium. The propatagium was supported by one of the wrist bones, the pteroid, which angled forward and upward. One specimen – just a baby a few weeks old – appeared capable of powered flight. Another specimen shows evidence of a baggy throat pouch that could carry food; perhaps the youngest pterodactyls, not yet able to fly, were hand-delivered food from their mothers? Pterodactylus lived in coastal areas and likely roosted along the shorelines, fishing off-shore. These pterosaurs would've been stock imagery of Europe during the Tithonian stage, which is where we begin our globe-trotting journey.

The First Stop: Europe. Much of our information of Tithonian European dinosaurs comes from the Lourinha Formation of Portugal (pictured to the right); this formation emerged at the genesis of the Atlantic Ocean in the Late Triassic and gives us snapshots of terrestrial European life up to the Late Cretaceous. During the Tithonian, this ‘seaside island resort’ environment was home to many sauropods. The eighty-foot-long diplodocid Dinheirosaurus lived alongside the similarly-sized brachiosaurid Lusotitan; these two sauropods practiced niche partitioning, inhabiting the same environment by feeding on different plants: whereas Dinheirosaurus was a low-browser, feasting on ferns and cycads low to the ground, Lusotitan was a high-browser, feeding on the plentiful conifers and gingkoes in its ecosystem. The stegosaur Dacentrurus continued into the Tithonian and walked alongside a new long-necked stegosaur named Miragaia. Miragaia likely grew an elongated neck to shift from being a low-browser to a medium-browser; because of this, it and the low-browsing Dacentrurus could live side-by-side because they were feeding on different foodstuffs. Predators of this environment included Allosaurus and Torvosaurus, both of which also lived in North America. In the image above to the right, a pair of Allosaurus run in front of a mother Lusotitan protecting its child. To the north in what is modern-day England, an early ankylosaur named Priodontognathus emerged, as well as a new theropod closely related to the earlier Stokesaurus. This new theropod, Juratyrant, stalked the wooded islands of prehistoric England. At twenty-two feet in length, it was likely the King of the Prehistoric British Isles.

the long-necked stegosaur Miragaia of Late Jurassic Portugal

To the east of prehistoric England lie the scattered islands and archipelagos of modern Grance and Germany. During the Tithonian, much of modern western Europe was inundated by shallow, reef-dominated armlets of the Tethys Sea. Emerging from this vast spider-web network of waterways were dry, forested islands cut by streams and lagoons. Europe was closer to the equator at this time (along the same latitude as Florida), though the climate was drier than modern tropics. These forested islands were dominated by low-lying shrubs, cycads, and conifers. These islands catered to smaller terrestrial organisms: lizards, mammals, and a number of small-fry dinosaurs such as the lithe, fast-running Compsognathus and the squirrel-like theropod Sciurumimus. Compsognathus was a fast-moving predator the size of a turkey; it hunted small prey like lizards, mammals, and even insects. The small-fry Sciurumimus’ tail resembled that of the modern tree squirrel, hence the meaning of its name, ‘Squirrel-mimic.’ This creature is pictured above to the left; in the image below, a Compsognathus perches atop the cadaver of an indeterminite juvenile sauropod, likely in Portugal, to which it may have migrated.

While paravians - early birds - first appeared in China, by the Tithonian stage of the Late Jurassic they were marching their way into prehistoric Europe. Tithonian paravians of western Europe include Ostromia, Wellnhoferia, Alcmonavis, and the infamous Archaeopteryx. While little is known of the first three European paravians, due to scant fossil evidence, much is known of the infamous Archaeopteryx. This paravian was long considered the first bird, at least until earlier paravians were discovered as far back as the Middle Jurassic in China. Archaeopteryx was the size of a modern raven, and it likely hunted like a modern pheasant, burst-flying out of the brush or leaping from trees to attack prey. It likely fed on small prey such as mammals and lizards. 

The Second Stop: North America. As we move west into North America, we find the Morrison Formation relatively unchanged. Many of the same citizens from the Kimmeridgian Stage continue unabated into the Tithonian: there are sauropods, and stegosaurs, and ankylosaurs, and ornithopods - not to mention predators such as Allosaurus and Ceratosaurus. There are a few newcomers, as well. The stegosaur Alcovasaurus browsed ferns in the floodplains and likely sheltered in the gallery forests around lakes and rivers. It resembled its African cousin Kentrosaurus. Fruitadens (pictured to the left beside a stegosaur thagomizer), one of the latest-known heterodontosaurs, scurried among the ferns and cicads as it sought insects, clams, and crayfish in the countless streams and waterways. While its lithe legs enabled it to high-tail it from larger and more cumbersome predators, it had to keep a wary eye out for crocodylomorphs. 

Two new theropods also appeared: the large-sized Saurophaganax and the medium-sized Stokesosaurus. The latter was an early tyrannosaur, and it marks the beginning of the tyrannosaur lineage's growth in size: while tyrannosaurs of the Cretaceous would reach titanic proportions, they had humble beginnings as lithe, fleet-footed predators in the Jurassic. Stokesosaurus, reaching up to thirteen feet in length, was bigger than its predecessors but still dwarfed by contemporaneous predators such as Allosaurus and Torvosaurus. Even the thirty-foot-long Allosaurus was put in its place by its close cousin Saurophaganax, which could reach up to forty-six feet in length. Saurophaganax was the Top Dog of the Morrison Formation in the Tithonian; it likely hunted sauropods such as Diplodocus and Brachiosaurus, though some speculate that it was a scavenger who principally relied on eating via thieving the kills of smaller theropods. Below is a painting of a Saurophaganax relaxing after a long day of thievery: 

Tithonian-age bone-beds in the Morrison have revealed leagues of non-dinosaurian organisms, such as the turtle Dinochelys and the snake-like Parviraptor. The latter, pictured to the right, is often considered the earliest snake despite not being a ‘true’ snake. It’s known from fragmentary material that leaves us guessing as to the shape, length, and form of its body. The skull shares features with modern snakes but lacks lateral notches in the lower jaw. Parviraptor has led snake researchers to conclude that snake ancestors evolved snakelike heads earlier than snakelike bodies. Amphibians of the Tithonian included the early frogs Comobatrachus and Rhadinosteus. Tithonian bone-beds have revealed numerous early mammals that lived in the Morrison Formation. Fruitafossor was a chipmunk-sized, armadillo-looking mammal that likely fed on termites and other insects. It’s nicknamed ‘Popeye’ because of its large front limbs. Another early mammal, Paurodon, resembled modern golden moles, and it likely fed on earthworms and may have been subterranean. In the image below, a Dinochelys attempts to scurry away from a Ceratosaurus in a drought-stricken lakebed:

Crocodylomorphs were common in the Morrison Formation of the Tithonian. Fruitachampsa (pictured to the left) was a three-foot-long long-limbed terrestrial predator with a short face and a prominent pair of canine-like teeth in the lower jaw. When viewed from above, its skull was square-shaped in the back and narrowed towards the front. It had long and slender limbs, and bony osteoderms covered its back in a pair of overlapping rows and were less robust than those of modern crocodiles. Hoplosuchus measured only eight inches long, though the remains we have may have belonged to a juvenile. It, like Fruitachampsa, had long limbs, suggesting a terrestrial lifestyle, and two rows of bony scutes ran down its back. Given its small size, at least in infancy, it probably fed on insects and small vertebrates. 

The Third Stop: Africa. As we head south from the savannah-like floodplains of the Morrison Formation, we cross the burgeoning Atlantic Ocean and reach the coastal shore of northern Africa. This area is known to us thanks to the Tendaguru Formation of modern Tanzania. The coastline is riddled with brackish coastal lakes, ponds, and pools, and further inland the rugged land gives way to sweeping conifer forests. While the low-browsing diplodocids dominated the Morrison Formation to the north, it's the high-browsing macronarians who reign supreme here in northern Africa. The dense conifer forests are perfect for their way of life. Two new sauropods - both macronarians - come onto the scene. The 56-foot-long Australodocus is one of the first sauropods of the lineage that will eventually give birth to the massive, armored titanosaur sauropods of the Cretaceous Period; the 80-foot-long Giraffatitan (pictured to the above left) is the largest macronarian of these conifer forests with a neck reaching nearly fifty feet above its shoulders. 

Low-browsing herbivores of the Tendaguru included Dysalotosaurus from the Kimmeridgian and the newcoming stegosaur Kentrosaurus (pictured to the right). This stegosaur was closely related to the North American Stegosaurus but was half its size at fifteen feet in length. It had a row of plates along its back, long spikes on its tail, and a single long spike coming out of each of its shoulders. It would've used its spikes as defensive weapons against the theropods Allosaurus and Veterupristisaurus. A new theropod emerged: the 28-foot-long Ostafrikasaurus, known from a single tooth, is the earliest known spinosaurid dinosaur, representing a 'primitive' form of the theropod line that would eventually spawn such heavyweight as Baryonyx, Suchomimus, and Spinosaurus. While little is known of Ostafrikasaurus, it's speculated that it prowled the coastal regions of northern Africa, preying on fish and marine reptiles as well as the occasional pterosaur. 

Intermission: An Oddball in South America. Before we head west across the Pacific Ocean to begin our sight-seeing in Tithonian Stage China, we should make a brief pit-stop in Chile, South America, to note an oddball dinosaur named Chilesaurus. This 'black sheep' dinosaur looks like a cross between a theropod and an ornithischians, and no one really knows where to put it in the dinosaur family tree. Those who argue for a theropod lineage point out that it’s not uncommon – although it’s certainly not usual – for theropods to adapt herbivorous lifestyles. We see this with the therizinosaurs, who became herbivorous, and with the ornithomimosaurs, who became omnivorous. Perhaps Chilesaurus is simply a theropod that went vegan. Others, however, consider the mixture of traits between theropods and ornithischians as evidence that we’ve got the dinosaur family tree all wrong. The current cladogram, which subdivides Dinosauria into the lizard-hipped Saurischians and the bird-hipped Ornithischians, wasn’t the only cladogram proposed; another was proposed by Thomas Huxley in 1869 (and revived by some scientists in 2017). Huxley argued that Dinosauria should be subdivided into Saurischia and Ornithoscelida. In his proposal, Saurischia contained all the sauropodomorphs, and Ornithoscelida contained the theropods and the ornithischians. In Huxley’s scheme, theropods are more closely related to ornithischians than to the sauropodomorphs. Proponents of his view point to Chilesaurus as evidence that his thesis is not only justifiable but correct, and that Chilesaurus, despite its relatively late appearance in the fossil record, is evidence of a ‘vestigial’ family line that eventually gave rise to both ornithischians and theropods. 

The Fourth Stop: China. As we come into China, we find the long-necked Mamenchisaurus continuing to feast on the thick woodlands. Scurrying through the undergrowth are two new species of primitive ceratopsians: Chaoyangsaurus and Xuanhuaceratops. Both were small bipedal herbivores who avoided predators by hiding in thick underbrush and running speedily away on their lithe hind limbs. While primitive ceratopsians emerged earlier in the Jurassic, it was during the Tithonian stage of the Late Jurassic that at least one species - Xuanhuaceratops, pictured here - shows the beginnings of the neck frill that would eventually characterize the ceratopsians. The lush environments of Jurassic China thus gave birth to one of the most beloved and spectacular dinosaur lineages of the entire Mesozoic, the wondrous ceratopsians who would dominate the Cretaceous Period.