Lopez de Bertodano Formation | |
---|---|
Stratigraphic range: Maastrichtian-Danian ~ | |
Type | Geological formation |
Unit of | Marambio & Seymour Island Groups |
Sub-units | Cape Lamb & Lower Sandwich Bluff Members |
Underlies | Sobral Fm., La Meseta Fm. |
Overlies | Snow Hill Island Formation |
Lithology | |
Primary | Siltstone, mudstone |
Other | Sandstone with concretions |
Location | |
Coordinates | 64°00′S57°24′W / 64.0°S 57.4°W |
Approximate paleocoordinates | 61°54′S68°06′W / 61.9°S 68.1°W |
Region | Seymour Island, James Ross Island group, Vega Island |
Country | Antarctica |
Type section | |
Named for | López de Bertodano Bay |
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 (upper-lower Maastrichtian stage [1] ) to the Danian stage of the lower Paleocene, from about 70 to 65.5 million years ago, straddling the Cretaceous-Paleogene boundary. [2]
The Cretaceous–Paleogene boundary (K–Pg) crops out on Seymour Island in the upper levels of the Lopez de Bertodano Formation. [3] A small (but significant) iridium anomaly occurs at the boundary on Seymour Island, as at lower latitudes, thought to be fallout from the Chicxulub impactor in the Gulf of Mexico. [4] Directly above the boundary a layer of disarticulated fish fossils occurs, victims of a disturbed ecosystem immediately following the impact event. [3] Multiple reports have described evidence for climatic changes in Antarctica prior to the mass extinction, [5] but the extent to which these affected marine biodiversity is debated. Based on extensive marine fossil collections from Seymour Island, recent work has confirmed that a single and severe mass extinction event occurred at this time in Antarctica just as at lower latitudes. [6]
During the Maastrichtian, Seymour Island was located within the Antarctic polar circle at around ~65°S latitude. [7] Chemical studies on oxygen-18 isotopes found in shells and benthic foraminifera have calculated intermediate-depth and deep-sea ocean temperatures at a mean average of 6 °C (43 °F) with fluctuations of 4–12 °C (39–54 °F) throughout the Maastrichtian; one of the same studies has also suggested that sea surface temperatures may have been colder, possibly dropping below freezing and forming sea ice at times. [8] [9] Alternatively, a study using data acquired from ancient bacterial membrane lipids yielded a slightly warmer temperature of 12 ± 5 °C (54 ± 9 °F) around 66 Ma. Nevertheless, these estimated climates characterize primarily cool temperate environments with possible subpolar and warm episodes. [7]
The Lopez de Bertodano Formation has provided many fossils of flora, dinosaurs and birds. [10] [11] [12] Also the first fossil egg from Antarctica, Antarcticoolithus , was found in the formation. [13]
Dinosaur remains are among the fossils that have been recovered from the formation [14] and include at least two and probably as much as six lineages of indisputably modern birds: one related to waterfowl, a primitive shorebird or related form, 1 to 2 species of possible loons, a large and possibly flightless bird belonging to a lineage extinct today as well as a partial skull that might belong to either of the smaller species or represent yet another one. The formation also contains a rich fossil invertebrate fauna, including bivalves, gastropods, [15] and cephalopods (ammonites and nautiloids). [16]
The fish assemblage of the López de Bertodano Formation was dominated by Enchodus and ichthyodectiformes, accounting for 21.95% and 45.6% of local fish diversity respectively. Of the remaining percentages, sand sharks made up 10.5%, the cow shark Notidanodon 6.8%, chimaeras 3.9%, saw sharks 2.7%, various other teleost fish 2.4%, and the remaining 6% were shared between other sharks like Paraorthacodus , frilled sharks, Protosqualus , and Cretalamna. [17]
Color key
| Notes Uncertain or tentative taxa are in small text; |
Theropods recorded from Lopez de Bertodano Formation | |||||
---|---|---|---|---|---|
Genus | Species | Member | Material | Description | Image |
Charadriiform [18] | Unnamed species | Cape Lamb | Partial skeleton | ||
Conflicto | C. antarcticus | Partial skeleton | An anseriform | ![]() | |
Neornithes | Indeterminate. | Partial skull | Relationships undetermined, cranium some 5–6 centimetres (2.0–2.4 in) long | ||
Polarornis | P. gregorii | Lower Sandwich Bluff | Partial skull and skeleton, holotype | A loon? [14] | |
P.? sp. | Lower Sandwich Bluff | Partial skeleton including wing and hindlimbs | Possibly a more primitive form with strong flight ability and lighter bones | ||
Vegavis | V. iaai [19] | Lower Sandwich Bluff | Partial skeleton, holotype | An anseriform | ![]() |
V. sp. | Cape Lamb | Isolated femur | Initially identified as a fossil of a member of Cariamae, [20] but subsequently reinterpreted as a fossil of an unnamed large-bodied member of the genus Vegavis. [21] | ||
Theropoda | Indeterminate. | Fragments [1] |
Ornithopods recorded from Lopez de Bertodano Formation | |||||
---|---|---|---|---|---|
Genus | Species | Member | Material | Description | Image |
Hadrosauridae | Indeterminate. | Sandwich Bluff Member | Isolated cheek tooth, MLP 98-I-10-1. [1] |
Elasmosaurs recorded from Lopez de Bertodano Formation | |||||
---|---|---|---|---|---|
Genus | Species | Member | Material | Description | Image |
Aristonectes [22] | A. parvidens | Seymour Island | Partial postcranial skeleton (MLP 89-III-3-1) | A giant elasmosaur | ![]() |
Marambionectes [23] | M. molinai | Seymour Island | Partially articulated incomplete skeleton including cranial material, many vertebrae, ribs, an ilium, limb bones (right humerus and ulna, a femur), and gastroliths (IAA-Pv 752) | A weddellonectian elasmosaur | ![]() |
Morturneria [24] | M. seymourensis | Seymour Island | several cervical vertebrae, a right humerus, a nearly complete left forelimb missing the proximal end of the humerus, and a left femur (TTU P9217) | An elasmosaur | ![]() |
Mosasaurs recorded from Lopez de Bertodano Formation | |||||
---|---|---|---|---|---|
Genus | Species | Member | Material | Description | Image |
Antarcticoolithus | A. bradyi | Seymour Island. | A fossilized eggshell. | A mosasaur. | |
Kaikaifilu [25] | K. hervei | Seymour Island | Several incomplete parts of a skull, jawbone, 30 isolated teeth, and a partial left humerus (SGO.PV.6509) | A tylosaurine mosasaur | ![]() |
Among others, the following fossils have been found in the formation:
Ammonites recorded from Lopez de Bertodano Formation | |||||
---|---|---|---|---|---|
Genus | Species | Member | Material | Description | Image |
Diplomoceras | D. cylindraceum | A paperclip-shaped Ammonite. | |||
Gaudryceras | G. seymouriense | ||||
Grossouvrites | G. joharae | ||||
Kitchinites | K. laurae | ||||
Maorites | M. densicostatus | ||||
Pachydiscus | P. (Pachydiscus) ultimus | ||||
Pseudophyllites | P. cf. loryi | ||||
Zelandites | Z. varuna |
Invertebrates recorded from Lopez de Bertodano Formation | |||||
---|---|---|---|---|---|
Genus | Species | Member | Material | Description | Image |
Eutrephoceras | E. dorbignyanum | ||||
Cyathocidaris | C. nordenskjoldi | ||||
C. patera | |||||
Rotularia | R. fallax |
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.
Vegavis is a genus of extinct bird that lived in Antarctica during the Maastrichtian stage of the Late Cretaceous, around 66.5 million years ago. The type species is Vegavis iaai. Vegavis was considered to be a member of Anseriformes within Galloanserae, but this claim has not been supported by recent studies.
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.
Victorlemoinea is an extinct litoptern genus of the family Sparnotheriodontidae, that lived from the Early to Middle Eocene. Fossils of Victorlemoinea have been found in the Las Flores, Sarmiento and Koluel Kaike Formations of Argentina, the Itaboraí Formation of Brazil and La Meseta Formation, Antarctica.
Seymour Island or Marambio Island, is an island in the chain of 16 major islands around the tip of the Graham Land on the Antarctic Peninsula. Graham Land is the closest part of Antarctica to South America. It lies within the section of the island chain that resides off the west side of the peninsula's northernmost tip. Within that section, it is separated from Snow Hill Island by Picnic Passage, and sits just east of the larger key, James Ross Island, and its smaller, neighboring island, Vega Island.
Aristonectes is an extinct genus of large elasmosaurid plesiosaurs that lived during the Maastrichtian stage of the Late Cretaceous. Two species are known, A. parvidens and A. quiriquinensis, whose fossil remains were discovered in what are now Patagonia and Antarctica. Throughout the 20th century, Aristonectes was a difficult animal for scientists to analyze due to poor fossil preparation, its relationships to other genera were uncertain. After subsequent revisions and discoveries carried out from the beginning of the 21st century, Aristonectes is now recognised as the type genus of the subfamily Aristonectinae, a lineage of elasmosaurids characterized by an enlarged skull and a reduced length of the neck.
The Santa Marta Formation is a geologic formation in Antarctica. It, along with the Hanson Formation and the Snow Hill Island Formation, are the only formations yet known on the continent where dinosaur fossils have been found. The formation outcrops on James Ross Island off the coast of the northern tip of the Antarctic Peninsula. In its entirety, the Santa Marta Formation is on average one kilometer thick.
Paraorthacodus is an extinct genus of shark. It a member of the family Paraorthacodontidae, which is either placed in Hexanchiformes or in Synechodontiformes. It is known from over a dozen named species spanning from the Early Jurassic to the Paleocene, or possibly Eocene. Almost all members of the genus are exclusively known from isolated teeth, with the exception of P. jurensis from the Late Jurassic-Early Cretaceous of Europe, which is known from full body fossils from the Late Jurassic of Germany, which suggest that juveniles had a robust body with a round head, while adults had large body sizes with a fusiform profile. There was only a single dorsal fin towards the back of the body without a fin spine. The dentition had teeth with a single large central cusp along with shorter lateral cusplets, which where designed for clutching. The teeth are distinguished from those of Synechodus by the lateral cusplets decreasing in size linearly away from the central cusp rather than exponentially as in Synechodus.
The Sobral Formation is a palaeontological formation located in Antarctica. It dates to the Danian stage of the Lower Paleocene period.
Ampheristus is an extinct genus of prehistoric marine ray-finned fish. It was a basal or stem member of the family Ophidiidae, which contains modern cusk-eels. Fossils are known from worldwide from the Late Cretaceous to the late Paleogene, making it a rather successful survivor of the Cretaceous-Paleogene extinction event.
The Snow Hill Island Formation is an Early Maastrichtian geologic formation found on James Ross Island, James Ross Island group, Antarctica. Remains of a paravian theropod Imperobator antarcticus have been recovered from it, as well as the elasmarian ornithopods Trinisaura santamartaensis, Biscoveosaurus and Morrosaurus antarcticus, the ankylosaurian Antarctopelta oliveroi, and the shark Notidanodon sp. Alongside these described genera are also the remains of indeterminate elasmosaurids, lithostrotian titanosaurs and an indeterminate pterosaur.
Cariamiformes is an order of primarily flightless birds that has existed for over 50 million years. The group includes the family Cariamidae (seriemas) and the extinct families Phorusrhacidae, Bathornithidae, Idiornithidae and Ameghinornithidae. Extant members (seriemas) are only known from South America, but fossils of many extinct taxa are also found in other continents including Europe and North America. Though traditionally considered a suborder within Gruiformes, both morphological and genetic studies show that it belongs to a separate group of birds, Australaves, whose other living members are Falconidae, Psittaciformes and Passeriformes.
Trinisaura is a genus of ornithopod dinosaur that lived during the late Campanian stage of the Upper Cretaceous, around 73 to 72 million years ago in what is now James Ross Island off the coast of northern Antarctica near Patagonia. It is known from a single, incomplete postcranial skeleton that includes several vertebrae, a partial pelvis, and nearly complete right hindlimb. The fossils were collected in 2008 by paleontologists Juan Moly and Rodolfo Coria from the sandstone of the Snow Hill Island Formation. It remained undescribed in the collections of the Museo de La Plata until its description by Coria and colleagues in 2013, being the basis of the novel genus and species Trinisaura santamartaensis. The genus name is to commemorate the efforts of Argentine geologist Trinidad "Trini" Diaz and the Latin root -sauros, meaning "lizard". The species name is after Santa Marta Cove, where the fossils were collected.
The La Meseta Formation is a sedimentary sequence deposited during the Eocene on Seymour Island off the coast of the Antarctic Peninsula. It is noted for its fossils, which include both marine organisms and the only terrestrial vertebrate fossils from the Cenozoic of Antarctica.
The Cretaceous–Paleogene (K–Pg) extinction event, also known as the Cretaceous–Tertiary(K–T)extinction, was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. The event caused the extinction of all non-avian dinosaurs. Most other tetrapods weighing more than 25 kilograms also became extinct, with the exception of some ectothermic species such as sea turtles and crocodilians. It marked the end of the Cretaceous period, and with it the Mesozoic era, while heralding the beginning of the current era, the Cenozoic. In the geologic record, the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary or K–T boundary, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows unusually high levels of the metal iridium, which is more common in asteroids than in the Earth's crust.
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.
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.
Notiolofos is an extinct genus of sparnotheriodontid ungulate from the order Litopterna. The animal lived during the Eocene, in modern-day Antarctica. The genus contains two species, N. arquinotiensis, the type species, and N. regueroi.
Marambionectes is an extinct genus of weddellonectian elasmosaurid plesiosaur from the Late Cretaceous López de Bertodano Formation of Antarctica. The genus contains a single species, M. molinai, known from a partial skeleton.