| Antarcticoceras | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Subclass: | † Ammonoidea |
| Order: | † Ammonitida |
| Suborder: | † Ancyloceratina |
| Family: | † Ancyloceratidae |
| Genus: | † Antarcticoceras Thomson, 1974 |
| Species | |
| |
Antarcticoceras is a genus of crioconic ammonites in the family Shasticrioceratidae. It lived during the Early Cretaceous Period. Antarcticioceras fossils can be found in the Cretaceous rocks of Antarctica and South America. [1]
The type species of Antarcticoceras,A. antarcticum, was described from 6 (possibly 7) specimens that were recovered from Alexander Island: the largest antarctic island. [1] When these specimens were first recovered, it was thought they represented an unknown taxon within the Ancyloderid subfamily Helicancyanae. [1] [2] This original hypothesis was made because the first two specimens recovered were smaller in overall size and displayed apparent aspinoceratid coiling, which is typical within several helicancyan taxa. [1] Once more specimens were recovered, it became clear that the overall form of the shell was more similar to the Crioceratidae than the Ancyloceratidae. The exact placement of Antarcticoceras remained uncertain because the specimens displayed high dorso-lateral tubercule, single-sized ribbing, and fairly simple suture, none of which were Crioceratid features.
A later study found major similarities in the ventral morphology and ornamentation Shasticrioceras and Antarcticoceras which suggest a shared evolutionary origin. [3] A new family, Shasticrioceratidae, was then erected to accommodate both genera. [3]
Following the placement of the genus into the Shasticrioceratidae, it appears most likely that Antarcticoceras evolved sometime during or before the Barremian from Shasticrioceras or a Shasticrioceras-like common ancestor. A. domeykanum appeared first, followed by A. perezi and A. antarcticum, however the nomen nudum status of A. perezi casts uncertainty on the late-Berremian to early Albian evolutionary history of the genus, until the appearance of A. antarcticum. [3]
Three species of Antarcticoceras are known in the literature: A. antarcticum, the type, was recovered from Albian- aged rocks of Alexander Island. Following the recognition of Antarcticoceras as a genus another species, A. domeykanum (from the earlier Barremian) was placed into the genus as well. [4] [5] A third species A. perezi is generally regarded as a nomen nudum (the description is not considered complete enough to justify a valid taxonomic name). [6] [3]
Anarcticoceras fossils are known from marine deposits randing from 113 to 129 million years in age. A. domeykanum is found in the Chañarcillo Basin of northern Chile, [6] While A. antarcticum is known only from the rocks of Antarctica's Alexander Island. [1]
Mosasaurs comprise a group of extinct, large marine reptiles from the Late Cretaceous.Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. They belong to the order Squamata, which includes lizards and snakes.
Ultrasaurus is a genus of sauropod dinosaur discovered by Haang Mook Kim in South Korea. However, the name was first used unofficially in 1979 by Jim Jensen to describe a set of giant dinosaur bones he discovered in the United States. Because Kim published the name for his specimen before Jensen could do so officially, Jensen renamed his specimen Ultrasauros. Jensen's giant sauropod was later found to be a chimera, and the type remains are now assigned to Supersaurus.
The South Polar region of the Cretaceous comprised the continent of East Gondwana–modern day Australia and Antarctica–a product of the break-up of Gondwana. 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.
Valdosaurus is a genus of bipedal herbivorous iguanodont ornithopod dinosaur found on the Isle of Wight and elsewhere in England, Spain and possibly also Romania. It lived during the Early Cretaceous.
Tugulusaurus is a genus of coelurosaurian theropod dinosaur that belongs to the Alvarezsauroidea. It is known from the Early Cretaceous Tugulu Group in the Urhe area of the People's Republic of China.
Futabasaurus is a genus of plesiosaur from the Late Cretaceous of Fukushima, Japan. It was described and named in 2006, and was assigned to the family Elasmosauridae. The genus contains one species, F. suzukii.
Antarctopelta was a genus of ankylosaurian dinosaur with one known species, A. oliveroi, which lived in Antarctica during the Late Cretaceous Period. It was a medium-sized ankylosaur, reaching no more than 4 meters (13 ft) in length, and showed characteristics of two different families, making more precise classification difficult. The single known fossil specimen was discovered on James Ross Island in 1986, constituting the first dinosaur remains ever discovered on Antarctica, although it is the second dinosaur from the continent to be formally named.
Palaeocursornis is a monotypic genus of pterosaurs. The only known species, P. corneti, was described in 1984 based on a single bone interpreted as the distal part of a left femur, found in Early Cretaceous (Berriasian rocks from a mine at Cornet near Oradea in northwestern Romania. It was initially assumed to be a flightless paleognathe bird, possibly a ratite, and later as a more primitive ornithuromorph or non-avialan theropod. However, re-evaluation of the specimen suggested that it was not a femur at all, but the upper arm bone of a pterodactyloid pterosaur similar to Azhdarcho.
"Proornis" is an extinct genus of basal bird from the Early Cretaceous Gyeongsang Supergroup of northernmost North Korea. Since it was never formally described in a peer-reviewed journal, the genus is considered a nomen nudum. A single species, "Proornis coreae", is known.
Vescornis is a genus of enantiornithine bird. One species is named, V. hebeiensis. The holotype fossil is in the collection of the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences. Its catalog number is CAGS 130722. The fossil was found in Early Cretaceous rocks first attributed to the Yixian Formation, Senjitu, Fengning County, Hebei Province, China. However, later study of area geology showed that these rocks actually belong to the Huajiying Formation.
Taniwhasaurus is an extinct genus of mosasaur which inhabited New Zealand, South Africa, Japan and Antarctica. The genus was a close relative of the genus Tylosaurus.
Polyptychoceras is an extinct genus of ammonites from the Late Cretaceous of Asia, Europe, and North and South America. It was first named by Hisakatsu Yabe in 1927.
The Wonthaggi Formation is an informal geological formation in Victoria, Australia whose strata date back to the Early Cretaceous. It is part of the Strzelecki Group within the Gippsland Basin. Dinosaur remains are among the fossils that have been recovered from the formation. It is partially equivalent to the Eumeralla Formation.
The Lopez de Bertodano Formation is a geological formation in the James Ross archipelago of the Antarctic Peninsula. The strata date from the end of the Late Cretaceous to the Danian stage of the lower Paleocene, from about 70 to 65.5 million years ago, straddling the Cretaceous-Paleogene boundary.
Hylaeochampsa is an extinct genus of eusuchian crocodylomorphs. It is known only from a partial skull recovered from Barremian-age rocks of the Lower Cretaceous Vectis Formation of the Isle of Wight. This skull, BMNH R 177, is short and wide, with a eusuchian-like palate and inferred enlarged posterior teeth that would have been suitable for crushing. Hylaochampsa was described by Richard Owen in 1874, with H. vectiana as the type species. It may be the same genus as the slightly older Heterosuchus, inferred to have been of similar evolutionary grade, but there is no overlapping material as Heterosuchus is known only from vertebrae. If the two could be shown to be synonyms, Hylaeochampsa would have priority because it is the older name. Hylaeochampsa is the type genus of the family Hylaeochampsidae, which also includes Iharkutosuchus from the Late Cretaceous of Hungary. James Clark and Mark Norell positioned it as the sister group to Crocodylia. Hylaeochampsa is currently the oldest known unambiguous eusuchian.
Ancyloceratidae is a family of heteromorphic ammonites that lived during the Early Cretaceous. Their shells begin as a loose spiral with whorls not touching which then turns into a straight shaft that ends in a J-shape hook or bend at end. Coarse ribbing and spines are common.
Stenorhynchosaurus is an extinct genus of pliosaurid plesiosaurs which lived in South America during the Early Cretaceous. The type species and only known is Stenorhynchosaurus munozi.
Leyvachelys is an extinct genus of turtles in the family Sandownidae from the Early Cretaceous of the present-day Altiplano Cundiboyacense, Eastern Ranges, Colombian Andes. The genus is known only from its type species, Leyvachelys cipadi, described in 2015 by Colombian paleontologist Edwin Cadena. Fossils of Leyvachelys have been found in the fossiliferous Paja Formation, close to Villa de Leyva, Boyacá, after which the genus is named. The holotype specimen is the oldest and most complete sandownid turtle found to date.
