# Lopez de Bertodano 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 (upper-lower Maastrichtian stage) to the Danian stage of the lower Paleocene, from about 70 to 65.5 million years ago, straddling the Cretaceous-Paleogene boundary.

## Cretaceous-Paleogene boundary

The Cretaceous–Paleogene boundary (K–Pg) crops out on Seymour Island in the upper levels of the Lopez de Bertodano Formation. 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. Directly above the boundary a layer of disarticulated fish fossils occurs, victims of a disturbed ecosystem immediately following the impact event. Multiple reports have described evidence for climatic changes in Antarctica prior to the mass extinction, 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.

## Climate

During the Maastrichtian, Seymour Island was located within the Antarctic polar circle at around ~65°S latitude. 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. 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.

## Fossil content

The Lopez de Bertodano Formation has provided many fossils of flora, dinosaurs and birds. Also the first fossil egg from Antarctica, Antarcticoolithus, was found in the formation.
Dinosaur remains are among the fossils that have been recovered from the formation 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, and cephalopods (ammonites and nautiloids).
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.

### Vertebrates
#### Dinosaurs

| Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon | Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited. |

##### Ornithischians

Ornithischians recorded from Lopez de Bertodano Formation :
| Genus | Species | Member/location | Material | Description |
| Elasmaria | Indeterminate | Sandwich Bluff Member | CM 93790, right prox. Metatarsal II; Rt. Prox. Metatarsal IV; left. Prox. Fibula | |
| Elasmaria | Indeterminate | Sandwich Bluff Member | MLP 98-I-10-70, pedal ungual | Also considered Ornithischia Indet |
| Hadrosauridae | Indeterminate | Sandwich Bluff, Vega Island | Isolated cheek tooth, MLP 98-I-10-1. | The 1st Hadrosaur remains of Antarctica |
| Hadrosauridae | Indeterminate | Seymour Island | MLP 96-1-6-2, Distal end of metatarsal | The 1st Hadrosaur remains of Antarctica |
| Parankylosauria | Indeterminate | Sandwich Bluff Member | Right pedal ungual IV, CM93791, and osteoderm | |

##### Theropods

Theropods recorded from Lopez de Bertodano Formation :
| Genus | Species | Member/location | Material | Description |
| Charadriiform | Indeterminate | Cape Lamb | Partial skeleton | |
| Conflicto | C. antarcticus | Seymour Island | MLP 07-III-1-1, a three-dimensionally preserved, partly complete skeleton | An anseriform |
| Gaviiformes | Indeterminate | VEG IAA 2/98, Isla Vega | MLP 98-I-10-47, MLP 98-I-10-50, MLP 98-I-10-52, MLP 98-I-10-76: tarsometatarsus;MLP 98-I-10-59: diaphysis of left tibiotarsus; MLP 98-I-10-51: proximal end of left femur; MLP 98-I-10-48: distal end of left tibiotarsus; MLP 98-I-10-60 and MLP 98-I-10-61: distal end and partial corpus of pedal phalanges. | Very similar to that of Gavia immer |
| cf. Gaviiformes | Indeterminate | VEG IAA 2/98, Isla Vega | MLP 98-I-10-54, MLP 98-I-10-27: tarsometatarsus; MLP 98-I-10-53: distal end of left tibiotarsus; MLP 98-I-10-49 distal end of right tibiotarsus | Very similar to that of Gavia immer |
| Megaraptora | Indeterminate | Sandwich Bluff, Cape Lamb | SDSM 159537, maxilla | Has oblong and narrow tooth alveoli, seen in Megaraptorans |
| Megaraptora | Indeterminate | Sandwich Bluff, Cape Lamb | SDSM 9918, left maxillary | Has oblong and narrow tooth alveoli, seen in Megaraptorans |
| Neornithes | Indeterminate | Sandwich Bluff, Cape Lamb | Partial skull | Relationships undetermined, cranium some 5–6 centimetres (2.0–2.4 in) long |
| Polarornis | P. gregorii | Sandwich Bluff, Seymour Island | Partial skull and skeleton, holotype | A Vegaviid of uncertain relative. Possibly a more primitive form with strong flight ability and lighter bones |
| Polarornis | P.? sp. | Sandwich Bluff, Cape Lamb | Partial skeleton including wing and hindlimbs | A Vegaviid of uncertain relative. Possibly a more primitive form with strong flight ability and lighter bones |
| Polarornis | cf. P. gregorii | Sandwich Bluff, Cape Lamb | MN 7833-V, distal portion of a tarsometatarsus | A Vegaviid of uncertain relative. Possibly a more primitive form with strong flight ability and lighter bones |
| Polarornis | P. sp. | IAA 10/13, Marambio Island | MLP 96-I-6-2, incomplete skeleton | A Vegaviid of uncertain relative. Possibly a more primitive form with strong flight ability and lighter bones |
| Vegavis | V. iaai | Lower Sandwich Bluff | Holotype (MLP 93-I-3-1), partial skeleton MACN-PV 19.748, partial skeleton AMNH FARB 30899, skull | A foot-propelled diver anseriform |
| Vegavis | V. sp. | Plesiosaur Papoose, Cape Lamb | Isolated femur | Initially identified as a fossil of a member of Cariamae, but subsequently reinterpreted as a fossil of an unnamed large-bodied member of the genus Vegavis. |
| Vegavis | cf. V. iaai | Sandwich Bluff, Cape Lamb | MN 7832-V, synsacrum | |
| Vegaviidae | Indeterminate | Seymour Island | | |
| Theropoda | Indeterminate | Sandwich Bluff, Cape Lamb | Fragments | |

#### Fish
##### Bony fishes

Bony fish recorded from Lopez de Bertodano Formation :
| Genus | Species | Member/location | Material | Description |
| Antarctiberyx | A. seymouri | Seymour Island | TTU P9210. A poorly preserved anterior skull section with partial dentary attached | A member of Beryciformes |
| Enchodus | E. sp. | Seymour Island | One palatine tooth, MLP 12-XI-29-43; five teeth, MLP 12-XI-29-25 to 28; one tooth, MLP 12-XI-29-53; thirty-five teeth, MLP 12-XI-29-55; fifty-three teeth, MLP 12-XI-29-56 | A member of Enchodontidae |
| Ichthyodectiformes | Indeterminate | Seymour Island | One tooth, MLP 12-XI-29-21; ninety-four teeth, MLP 12-XI-29-38; thirteen teeth, MLP 12-XI-29-51; seventy-eight teeth, MLP 12-XI-29-52; one tooth, MLP 12-XI-29-54. | |
| Pachycormidae | Indeterminate | Seymour Island | Isolated and fragmentary caudal fin-rays, MLP 13XI-29-57. | |

##### Chondrichthyes

Chondrichthyes recorded from Lopez de Bertodano Formation :
| Genus | Species | Member/location | Material | Description |
| Callorhinchus | C. sp. | Seymour Island | Teeth | A Chimaera |
| Carcharias | cf. C. sp. | Seymour Island | Two left upper lateral teeth preserving one root branch and lateral denticle, MLP 13-XI-29-35, MLP 13-XI-29-37; one right upper lateral tooth preserving one root branch and lateral denticle, MLP 13-XI-29-36; several fragmentary teeth, MLP 13-XI29-4, MLP13-XI-29-44 to46, MLP13-XI-29-16, MLP 13-XI-29-13 to 14. | A Odontaspididae Shark |
| "Cretalamna" | “C. appendiculata” | Seymour Island | One lateral lower tooth which lacks crown tip, distal lateral cusplet, and distal root branch, MLP 13XI-29-47; one anterior upper tooth lacking the distal root branch, distal lateral cusplet, and crown tip, MLP 13-XI-29-2 | A Otodontidae Shark |
| Lamniformes | Indeterminate | Seymour Island | Four crowns, MLP 13-XI-29-30. | |
| Notidanodon | N. sp. | Seymour Island | Teeth | A Hexanchidae Shark |
| Notidanodon | ?N. sp. | Seymour Island | Teeth | A Hexanchidae Shark |
| Paraorthacodus | P. sp. | Seymour Island | Four fragmentary teeth, MLP 13-XI-29-8, MLP 13XI-29-18, MLP 13-XI-29-31, and MLP 13-XI-29-32. | A Paraorthacodontidae Shark |
| Propristiophorus | aff. P. sp. | Seymour Island | Three fragmentary rostral spines, MLP 13-XI-2939, MLP 13-XI-29-40, and MLP 13-XI-29-41. | A Pristiophoridae Shark |
| Protosqualus | P. sp. | Seymour Island | Two lateral, almost complete teeth, MLP 13-XI29-9, MLP 13-XI-29-33; one latero-posterior, complete tooth, MLP 13-XI-29-10 | A Squalidae Shark |
| Sphenodus | S. sp. | Seymour Island | Teeth | A Orthacodontidae Shark |
| Sphenodus | S. sp. | Seymour Island | Two fragmentary teeth, MLP 13-XI-29-20, MLP 13-XI-29-11 | A Orthacodontidae Shark |
| Xampylodon | X. diastemacron | Filo Negro Section, Klb 9 | MN 7825-V (holotype),incomplete posterolateral tooth of the lower jaw, with only its anterior portion still preserved | A Hexanchidae Shark |

#### Reptiles
##### Elasmosaurs

Elasmosaurs recorded from Lopez de Bertodano Formation :
| Genus | Species | Member/location | Material | Description |
| Aristonectes | A. parvidens | Seymour Island | Partial postcranial skeleton (MLP 89-III-3-1) | A giant elasmosaur |
| Aristonectes | A. sp | Sandwich Bluff, Cape Lamb | MLP 11-I-1-15, caudal vertebra | A giant elasmosaur |
| Aristonectes | A. sp | Seymour Island | TTU.P.9219 (holotype skull and cervical vertebrae) | A giant elasmosaur |
| Elasmosauridae | Indeterminate | SW corner, Seymour Island | MLP 82-I-28-1, an incomplete skeleton comprising 15 cervical, three pectorals, 21 dorsal, three sacral, and 22 caudal vertebrae, an almost complete left hind limb, some dorsal ribs, incomplete coracoids and fragments of the scapulae | |
| Elasmosauridae | Indeterminate | SW corner, Seymour Island | ZPAL R.8, pectoral, dorsal, and caudal vertebral centra, femur, tibia, and fragments of the humerus, scapula, and ischia | |
| Elasmosauridae | Indeterminate | Seymour Island | TTU P 9240; dorsal, sacral and caudal vertebrae, limbs and paddle fragments | |
| Elasmosauridae | Indeterminate | Seymour Island | SGO.PV.6523, postcranial remains of a single adult individual, including remains of 9 mid-to-posterior cervical vertebrae (6 of them preserving parts of their centra), the right scapula, several fragments of ribs and gastralia, and one phalanx. | |
| Elasmosauridae | Indeterminate | Seymour Island | TTU P 9238; part of cervicals, rib fragments, isolated paddles, and gastroliths | |
| Elasmosauridae | Indeterminate | Seymour Island | TTU P 9239; isolated vertebrae, limb bones, paddle elements, and ribs | |
| Elasmosauridae | Indeterminate | Seymour Island | IAA Pv 443, an incomplete skeleton comprising the mandibular symphysis and part of right and left mandibular rami, cervical and dorsal centra, an incomplete humerus, radius, ulna, ulnare, intermedium, radiale and distal carpal 1, 2 þ 3 and 4, other fragmentary postcranial bones and associated gastroliths | |
| Euelasmosaurida | Indeterminate | Sandwich Bluff, Cape Lamb | CM 93780; left and right pubes and ischia: MLP 15-I-7-8, left ilium and indeterminate fragments | |
| Marambionectes | 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 | 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 |
| Weddellonectia | Indeterminate | Sandwich Bluff, Cape Lamb | MLP 15-I-7-48, right humerus, ulna, ulnare, intermedium, distal carpal I, distal carpal II+III, pisiform, phalanges and one rib | |
| Weddellonectia | Indeterminate | Seymour Island | MLP 14-I-20-16, 12 cervical vertebrae, three pectoral vertebrae, 11 dorsal vertebrae, one sacral vertebra, 11 caudal vertebrae, right femur, tibia, fibula and mesopodial elements, fragments of pectoral and pelvic girdles and gastroliths | |

##### Mosasaurs

Mosasaurs recorded from Lopez de Bertodano Formation :
| Genus | Species | Member/location | Material | Description |
| Antarcticoolithus | A. bradyi | Seymour Island. | A fossilized eggshell. | A mosasaur. |
| Kaikaifilu | 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 |
| Liodon | L sp. | Vega Island Sandwich Bluff | MLP 98-I-10-1 is a fragment of a maxilla; MLP 98-I-10-12/15/23 are a teeth | A Mosasauridae mosasaur |
| Liodon | L sp. | Seymour Island | DJ.952.266, a tooth | A Mosasauridae mosasaur |
| Mosasauridae | Indeterminate | Bahía Fósiles | MLP 80-I-1-1, a cervical vertebra; MLP 80-I-1-2, a mandibular fragment; MLP 80-I-1-3, a cranial fragment; MLP 82-I-28-2, a vertebra; MLP 82-I-3-1/4, four caudal centers | |
| Mosasauridae | Indeterminate | Seymour Island | DJ.957.133, 18 partially articulated caudal vertebrae, four of which possess transverse process, and DJ.957.505 a caudal vertebra | |
| Mosasauridae | Indeterminate | Filo Negro Section | MLP 82-I-26-1, a pygal vertebra | |
| Mosasauridae | Indeterminate | Seymour Island | IAA-Pv 819, an almost complete right humerus. | |
| Mosasauridae | Indeterminate | Seymour Island | MLP 82-I-5-1, fragments of vertebrae and ribs | |
| Mosasaurus | aff. M. hoffmanni | Seymour Island | DJ.1053.10, a large, fragmentary skull | A Mosasauridae mosasaur |
| Mosasaurus | M. sp. | Seymour Island | DJ.1020.2-A, DJ.1020.2-B and DJ.1053.14- A, teeth; MLP 83-X-12-2, a caudal vertebra; MLP 92-XII-30, skull fragments including one tooth and a relatively short, and medially constricted suprastapedial process of the quadrate | A Mosasauridae mosasaur |
| Mosasaurus | M. sp. | Seymour Island | MLP 15-I-24-41, a partial skull including, partial frontal, right postorbital, parietal, right quadrate, right posterior end of basisphenoid, right coronoid, right angular, splenial and right surangular, a broken marginal tooth and several pterygoid teeth have been associated to this specimen. | A Mosasauridae mosasaur |
| Plioplatecarpus | P. sp. | Seymour Island | DJ.1020.2-C, DJ.1020.2-H and DJ.952.266, teeth | A Mosasauridae mosasaur |
| Plioplatecarpus | P. sp. | Quebrada de la Foca muerta | MLP 79-I-1/20, several vertebrae | A Mosasauridae mosasaur |
| Tylosaurinae | Indeterminate | Bahía Fósiles | MLP 87-II-7-1, a vertebra; MLP 86-X-28-7, an anterior caudal vertebra | |
| Tylosaurinae | Indeterminate | Seymour Island | DJ.956.41, two or three caudal vertebrae | |
| Tylosaurinae | Indeterminate | Filo Negro Section | lam. II, 7-8, a vertebra | |

### Other fossils
#### Ammonites

Ammonites recorded from Lopez de Bertodano Formation :
| Genus | Species | Description |
| 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 | |

#### Other invertebrates

Invertebrates recorded from Lopez de Bertodano Formation :
| Genus | Species |
| Eutrephoceras | E. dorbignyanum |
| Cyathocidaris | C. nordenskjoldi |
| Cyathocidaris | C. patera |
| Rotularia | R. fallax |

#### Flora

* Antarctoxylon juglandoides
* Eucryphiaceoxylon eucryphioides
* Myrceugenelloxylon antarcticus