The South Polar region of the Cretaceous comprised the continent of East Gondwana–modern day Australia, Zealandia, and Antarctica–a product of the break-up of Gondwana in the Cretaceous Period. The southern region, during this time, was much warmer than it is today, ranging from perhaps 4–8 °C (39–46 °F) in the latest Cretaceous Maastrichtian in what is now southeastern Australia. This prevented permanent ice sheets from developing and fostered polar forests, which were largely dominated by conifers, cycads, and ferns, and relied on a temperate climate and heavy rainfall. Major fossil-bearing geological formations that record this area are: the Santa Marta and Sobral Formations of Seymour Island off the Antarctic Peninsula; the Snow Hill Island, Lopez de Bertodano, and the Hidden Lake Formations on James Ross Island also off the Antarctic Peninsula; and the Eumeralla and Wonthaggi Formations in Australia.
Pliosauroidea is an extinct clade of plesiosaurs, known from the earliest Jurassic to early Late Cretaceous. They are best known for the subclade Thalassophonea, which contained crocodile-like short-necked forms with large heads and massive toothed jaws, commonly known as pliosaurs. More primitive non-thalassophonean pliosauroids resembled plesiosaurs in possessing relatively long necks and smaller heads. They originally included only members of the family Pliosauridae, of the order Plesiosauria, but several other genera and families are now also included, the number and details of which vary according to the classification used.
Pachyrhinosaurus is an extinct genus of centrosaurine ceratopsid dinosaur from the Late Cretaceous period of North America. The first examples were discovered by Charles M. Sternberg in Alberta, Canada, in 1946, and named in 1950. Over a dozen partial skulls and a large assortment of other fossils from various species have been found in Alberta and Alaska. A great number were not available for study until the 1980s, resulting in a relatively recent increase of interest in Pachyrhinosaurus.
Alaskacephale is an extinct genus of pachycephalosaurid, a group of dome-headed, herbivorous ornithischian dinosaurs, that lived during the Campanian stage of the Late Cretaceous period in what is now northern Alaska. The genus is one of the few known Arctic dinosaurs and was found in the Prince Creek Formation, which preserves a menagerie of fossils. The only known specimen, a squamosal bone, was found in 1999 and later described in 2005. However, Alaskacephale was not formally named until the next year.
Umoonasaurus is an extinct genus of plesiosaur belonging to the family Leptocleididae. This genus lived approximately 115 million years ago during the Early Cretaceous period, in shallow seas covering parts of what is now Australia. It was a relatively small animal around 2.5 metres (8.2 ft) long. An identifying trait of Umoonasaurus is three crest-ridges on its skull.
Plesiopleurodon is an extinct genus of Mesozoic marine reptiles, belonging to Sauropterygia, known from the Late Cretaceous of North America. It was named by Kenneth Carpenter based on a complete skull with a mandible, cervical vertebra, and a coracoid. In naming the specimen, Carpenter noted "Of all known pliosaurs, Plesiopleurodon wellesi most closely resembles Liopleurodon ferox from the Oxfordian of Europe, hence the generic reference." It was initially described as a pliosaur due to it short neck, a common trait of the family, although it is in the order Plesiosauria. However, later exploration into the relationships of both orders indicate that not all pliosaurs have short necks and not all plesiosaurs have long necks.
Polycotylidae is a family of plesiosaurs from the Cretaceous, a sister group to Leptocleididae. Polycotylids first appeared during the Albian stage of the Early Cretaceous, before becoming abundant and widespread during the early Late Cretaceous. Several species survived into the final stage of the Cretaceous, the Maastrichtian.
Nichollssaura is an extinct genus of leptocleidid plesiosaur from the Early Cretaceous Boreal Sea of North America. The type species is N. borealis, found in the early Albian age Clearwater Formation near Fort McMurray, Alberta, Canada.
Ophthalmosauridae is an extinct family of thunnosaur ichthyosaurs from the Middle Jurassic to the early Late Cretaceous worldwide. Almost all ichthyosaurs from the Middle Jurassic onwards belong to the family, until the extinction of ichthyosaurs in the early Late Cretaceous. Opthalmosaurids appeared worldwide during early Bajocian, subsequent to the disappearance of most other ichthyosaur lineages after the end of the Toarcian. Currently, the oldest known ophthalmosaurids is Mollesaurus from the early Bajocian of Argentina, as well as indeterminate remains of the same age from Luxembourg and Canada. Named by George H. Baur, in 1887, the family contains the basal taxa like Ophthalmosaurus. Appleby (1956) named the taxon Ophthalmosauria which was followed by some authors, but these two names are often treated as synonyms; Ophthalmosauridae has the priority over Ophthalmosauria. However, some researchers argue that Ophthalmosauridae should be restricted to the group typically referred to as Ophthalmosaurinae, with classic Platypterygiinae instead being referred to as Undorosauridae or Brachypterygiidae and Ophthalmosauria being used to unite these two groups.
Mollesaurus is an extinct genus of large ophthalmosaurine ophthalmosaurid ichthyosaur known from northwestern Patagonia of Argentina.
Nannopterygius is an extinct genus of ophthalmosaurid ichthyosaur that lived during the Middle Jurassic to the Early Cretaceous. Fossils are known from England, Kazakhstan, Russia, and Norway and six species are currently assigned to the genus.
Baptanodon is an ichthyosaur of the Late Jurassic period, named for its supposed lack of teeth. It had a graceful 3.5 m (11 ft) long dolphin-shaped body, and its jaws were well adapted for catching squid. Major fossil finds of this genus have been recorded in North America. The type species, Sauranodon natans, was originally included under Sauranodon in 1879, but this name was preoccupied.
The Toolebuc Formation is a geological formation that extends from Queensland across South Australia and the Northern Territory in Australia, whose strata date back to the Albian stage of the Early Cretaceous. Dinosaurs, pterosaurs, plesiosaurs, ichthyosaurs, protostegid turtles, sharks, chimaeroids and bony fish remains are among the fossils that have been recovered from the formation.
The Prince Creek Formation is a geological formation in Alaska with strata dating to the Early Maastrichtian stage of the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.
Arthropterygius is a widespread genus of ophthalmosaurid ichthyosaur which existed in Canada, Norway, Russia, and Argentina from the late Jurassic period and possibly to the earliest Cretaceous.
Thunnosauria is an extinct clade of parvipelvian ichthyosaurs from the Early Jurassic to the early Late Cretaceous (Hettangian–Cenomanian) of Asia, Australia, Europe, North America, and South America. Named by Ryosuke Motani in 1999, it contains the basal taxa Ichthyosaurus and Stenopterygius and the family Ophthalmosauridae. In thunnosaurs, the fore fin is at least twice as long as the hind fin.
Spitrasaurus is an extinct genus of cryptoclidid plesiosauroid plesiosaur known from the uppermost Jurassic of central Spitsbergen, Norway and likely also Kimmeridge, England. It is named after a syllabic abbreviation for Spitsbergen Travel.
The Agardhfjellet Formation is a geologic formation in Svalbard, Norway. It preserves fossils dating back to the Oxfordian to Berriasian stages, spanning the Late Jurassic-Early Cretaceous boundary. The formation contains the Slottsmøya Member, a highly fossiliferous unit (Lagerstätte) where many ichthyosaur and plesiosaur fossils have been found, as well as abundant and well preserved fossils of invertebrates.
