| Antarcticoceras | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| 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]
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.
Koolasuchus is an extinct genus of brachyopoid temnospondyl in the family Chigutisauridae. Fossils have been found from Victoria, Australia and date back 125-120 million years ago to Barremian-Aptian stages of the Early Cretaceous. Koolasuchus is the youngest known temnospondyl. It is known from several fragments of the skull and other bones such as vertebrae, ribs, and pectoral elements. The type species Koolasuchus cleelandi was named in 1997. K. cleelandi was adopted as the fossil emblem for the state of Victoria, Australia on 13 January 2022.
Antarctopelta is a genus of ankylosaurian dinosaur, a group of large, quadrupedal herbivores, that lived during the Campanian stage of the Late Cretaceous period on what is now James Ross Island, Antarctica. Antarctopelta is the only known ankylosaur from Antarctica and a member of Parankylosauria. The only described specimen was found in 1986, the first dinosaur to be found on the continent, by Argentine geologists Eduardo Olivero and Robert Scasso. The fossils were later described in 2006 by paleontologists Leonardo Salgado and Zulma Gasparini, who named the type species A. oliveroi after Olivero.
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Taniwhasaurus is an extinct genus of mosasaurs that lived during the Campanian stage of the Late Cretaceous. It is a member of the subfamily Tylosaurinae, a lineage of mosasaurs characterized by a long toothless conical rostrum. Two valid species are attached to the genus, T. oweni and T. antarcticus, known respectively from the fossil record of present-day New Zealand and Antarctica. Two other species have been nominally classified within the genus, T. 'capensis' and T. 'mikasaensis', recorded in present-day South Africa and Japan, but their attribution remains problematic due to the fragmentary state of their fossils. The generic name literally means "taniwha lizard", referring to a supernatural aquatic creature from Māori mythology.
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 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.
Australodelphis mirus is an extinct Pliocene dolphin. A. mirus is known from fossils found in the Sørsdal Formation, Mule Peninsula, Vestfold Hills, East Antarctica. The genus has been described as an example of convergent evolution with beaked whales.
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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 the Early Cretaceous of South America. The type species and only known is Stenorhynchosaurus munozi. It was a medium-sized pliosaur, reaching an adult body length of 7 m (23 ft).
Kaikaifilu is an extinct genus of large mosasaurs that lived during the Late Cretaceous (Maastrichtian) in what is now northern Antarctica. The only species known, K. hervei, was described in 2017 from an incomplete specimen discovered in the López de Bertodano Formation, in Seymour Island, Antarctic Peninsula. The taxon is named in reference to Coi Coi-Vilu, a reptilian ocean deity of the Mapuche cosmology. Early observations of the holotype classify it as a member of the subfamily Tylosaurinae. However, later observations note that several characteristics show that this attribution is problematic.
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.
Mongolostegus is a genus of stegosaur from the Early Cretaceous (Aptian-Albian) Dzunbain Formation of Mongolia. The type and only species is M. exspectabilis, known from a single specimen previously under the nomen nudumWuerhosaurus mongoliensis.
Galleonosaurus is a genus of basal ornithopod dinosaur from the Wonthaggi Formation of the Gippsland region of Victoria, Australia. The type and only species is Galleonosaurus dorisae.
Imperobator is a genus of paravian theropod, a group of large, three-toed carnivorous dinosaurs, that lived during the Maastrichtian age of the Late Cretaceous period in what is now James Ross Island in Antarctica. Imperobator is one of only two non-avian theropods known from Antarctica, crossing over to the landmass when it was part of Gondwana. The only described specimen was found in 2003 by an expedition launched by the University of California Museum of Paleontology and initially described as a dromaeosaur in 2007. However, later searches reported more fossils from the site including teeth and skull bones. The fossils were formally described as a new genus of giant paravian in 2019.
Macroscaphitidae is an extinct family of ptychoceratoid cephalopods from the subclass Ammonoidea that lived from the Lower Barremian to the Lower Cenomanian stages of the Cretaceous. Fossils of Macroscaphitidae were found all around the world although the abundance of found fossils is rather limited. Known fossils from collections were found largely in Europe, South America and Africa. It is known for some species of which complete specimens were found that these animals developed a hetermorphic shell, i.e. the coiling of the shell was not regular, such that the first whirls formed a planispirally coiled evolute section as seen in homomorphic ammonites, but had an additional straight middle part and a presumably upwards facing aperture. Due to their odd morphology the taxonomic classification of Macroscaphitidae changed often over time since their discovery and may not be finally settled even now.
