Snow Hill Island Formation

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 antarcticusEly & Case, 2019 have been recovered from it, as well as the elasmarian ornithopods Trinisaura santamartaensis and Morrosaurus antarcticus, the ankylosaurian Antarctopelta oliveroi, and the shark Notidanodon sp. Alongside these described genera are also the remains of indeterminate elasmosaurids,O'Gorman, 2012, p.2 lithostrotian titanosaurs and an indeterminate pterosaur.

The uppermost portion of the Gamma Member containing the Santa Marta Cove fauna is dated to the late Campanian, approximately 73.4 million years ago, while the younger Cape Lamb Member is from the latest Campanian to early Maastrichtian, with the uppermost portion dated to 69.7 million years ago.

Paleofauna

Invertebrates Corals GenusSpeciesPresenceMaterialNotesImagesAstreopora?A. sp.Gamma MemberImprintsAcroporidae scleractinian FungiacyathusF. deltoidophorus Karlsen Cliffs MemberImprints Fungiidae scleractinian F. antarcticusNordenskjöld's hutImprintsF. larseniNordenskjöld's hutImprintsScleractinia indet. Unidentifiable Karlsen Cliffs MemberImprints

Arthropoda GenusSpeciesPresenceMaterialNotesImagesAngarestia A. australensisEast side of Leal BluffSpecimensA Glypheidae lobsterCristafronsC. praescientisEast side of Leal BluffSpecimensA Raninidae crabHadrocarcinusH. wrighti East side of Leal BluffSpecimensA Necrocarcinidae crabHoplopariaH. stokesiEast side of Leal Bluff; Humps IslandSpecimensA clawed lobster

Mollusks GenusSpeciesPresenceMaterialNotesImagesCymatocerasC. spp.Santa Marta CoveShellsA NautilidDiplomoceras D. cylindraceumDay NunatakShellsA Diplomoceratidae ammonite D. lambi Day Nunatak; Cape LambShellsEutrephocerasE. spp.Day NunatakShellsA NautilidGunnarites G. antarcticusVega Island; Day Nunatak; Santa Marta CoveShellsA Kossmaticeratidae ammoniteJacobitesJ. croftiDay NunatakShellsA Kossmaticeratidae ammoniteLaevidentaliumL.? sp.Paso San José, Point 96ShellsA Laevidentaliidae scaphopodanMaoritesM. seymourianusDay Nunatak; Al's Bird Site; Vega IslandShellsA Kossmaticeratidae ammoniteOistotrigoniaO. pygosceliumDay NunatakShellsA Pterotrigoniidae bivalvePinnaP. frenexiaeDay NunatakShellsA Pinnidae bivalveP. anderssoniDay NunatakShellsPseudophyllitesP. loryiDay NunatakShellsA Tetragonitidae ammoniteStruthiochenopusS. hurleyiDay NunatakShellsAn Aporrhaidae gastropod

Vertebrates Fish GenusSpeciesPresenceMaterialNotesImagesAlbuliformes indet.IndeterminateSanta Marta CoveIsolated vertebra, IAA-IRJ2000-24AntarctichthysA. longipectoralisSanta Marta Cove MN 7838-V, single and incomplete specimenA Dercetidae fishApateoduscf. A. sp.Santa Marta CoveteethAlepisauriformes fishCallorhinchusC. sp.Santa Marta CoveteethA ChimaeraCf. C. sp.Cape LambTeethCentrophoroidesC. sp.Santa Marta CoveTeethA Squalidae shark ChimaeraC. zangerli Santa Marta Cove, James Ross IslandTeethA chimaeraChlamydoselachusC. thompsoni Santa Marta Cove, James Ross Island Complete dentition A frilled sharkCretalamnaC. appendiculattaSanta Marta CoveTeethAn Otodontidae shark EdaphodonE. snowhillensis Herbert Sound MemberMLP 13- I-26-1, complete dentition A large species of chimaeraEnchodusE. sp.Santa Marta CoveIAA-IRJ2000-32, IAA-IRJ2000-33, teethEnchodontidae fishIchthyodectiformes indet.IndeterminateVega islandMLP 15-XI-7-11, body scale patchLamniformesIndeterminateSanta Marta Cove(IAA-IRJ2000-9 to IAA-IRJ2000-10, BAS DJ.172.11, teethNotidanodonN. dentatus Santa Marta Cove; Vega Island(MLP 95-IV-1), lateral tooth embedded in the hosting rock A cow sharkN. sp.Santa Marta CoveParaorthacodusP. antarcticusSanta Marta CoveIAA-IRJ2000-19; BAS DJ.136.2, teethA SynechodontiformRhinochimaeridae indet.IndeterminateSanta Marta CoveTeethScapanorhynchusS. spp.Santa Marta Cove IAA-IRJ2000-11A Mitsukurinidae sharkCf. S. sp.Santa Marta CoveTeethSphenocephalidaeIndeterminateFalse Island PointDJ. 360.8, small, incomplete, and poorly-preserved specimen that lack its skull and the anterior part of the bodySphenodusS. sp.Santa Marta CoveIAA-IRJ2000-17 and IAA-IRJ2000-18, teethAn OrthacodontidSquatinaS. cf.hassei Santa Marta CoveIAA-IRJ2000-10-IAA-IRJ2000-16An Angelshark

Pterosaurs GenusSpeciesPresenceMaterialNotesImagesPterodactyloidea indet.Indeterminate Camp Lamb, Vega IslandMN 7801-V, a wing metacarpal IVA pterosaur with an estimated wingspan of 4 to 5 meters

Dinosaurs GenusSpeciesPresenceMaterialNotesImagesAntarcticavisA. capelambensisCape Lambe Member, Vega IslandA partial skeleton (SDSM 78147) consists of two thoracic vertebrae, the sternum keel, the right coracoid and shoulder blade, the sternal part of the left coracoid, the right upper arm, parts of the left upper arm, the proximal right ulna, the proximal left ulna and radius (articulated), the proximal right carpometacarpus, the proximal left carpometacarpus, the distal left carpometacarpus, the synsacrum, the right and left thighs, the proximal right tibiotarsus, the right and left distal tibiotarsus, and the proximal right tarsometatarsusAn avialan of uncertain phylogenetic placementAntarctopeltaA. oliveroiSanta Marta CoveA partial skeleton (MLP 86-X-28-1) consists of three isolated teeth, part of the lower jaw with another tooth in situ, some other skull fragments, vertebrae of the neck, back, hips and tail, some shoulder and hip bones (scapula, ilium) a thigh bone (femur), foot and hand bones (five metapodials and two phalanges), and numerous pieces of armorA parankylosaur"Biscoveosaurus"IndeterminateCape Lamb MemberLamanna, Matthew C.; Case, Judd A.; Roberts, Eric M.; Arbour, Victoria M.; Ely, Ricardo C.; Salisbury, Steven W.; Clarke, Julia A.; Malinzak, D. Edward; West, Abagael R.; O'connor, Patrick M. (2019). "Late Cretaceous non-avian dinosaurs from the James Ross Basin, Antarctica: description of new material, updated synthesis, biostratigraphy, and paleobiogeography". Advances in Polar Science. 30 (3): 228–250. doi:10.13679/j.advps.2019.0007.NHMUK PV R 36760, dentaries, teeth, a braincase, parts of the maxillae, forelimb elements, assorted vertebrae, and the pectoral girdleAn ornithopodElasmaria indet.IndeterminateSanta Marta CoveTwo isolated ungual phalanges (MLP 07-III-2-1 and MLP 07-III-2-2)IndeterminateFortress HillLimb, footIndeterminateVega IslandBMNH BAS R.2450Gaviiformes indet.IndeterminateVega IslandMLP 98-I-10-47: incomplete tarsometatarsus; MLP 98-I-10-50: incomplete right tarsometatarsus; MLP 98-I-10-51: proximal end of left femurImperobatorI. antarcticusCape Lamb Member, Naze PeninsulaA single specimen that contains skull fragments possibly from the premaxilla, maxilla, and dentary as well as a caudal vertebra, teeth, and pedal elements, UCMP 276000A potential Unenlagiinae paravianLithostrotia indet.IndeterminateLoma Verde, near Santa Marta Cove11-II-20-1, incomplete middle caudal vertebraNon-SaltasaurinaeMorrosaurusM. antarcticusCape Lamb MemberFragmentary right hind limbAn elasmarian ornithopodNeornithes indet.IndeterminateVega IslandMLP 98-I-10-25, left tarsometatarsusOrnithurae indet.IndeterminateCape LambAMNH FARB 30920, thoracic vertebraTheropoda indet.IndeterminateCape LambMLP 15-I-7-2, isolated pedal phalax (digit III?)TrinisauraT. santamartaensisSanta Marta Cove, in the lower levels of the formationMLP08-III-1-1, disarticulated and partial skeleton that includes one incomplete dorsal vertebra, three sacral centra, seven caudal vertebrae; two incomplete dorsal rib shafts, one proximal haemal arch, incomplete right scapulocoracoid, incomplete right humerus, two metacarpals, both ilia, right pubis, right ischium, right femur, right distal tibia, incomplete metatarsal III, first phalanx of pedal digit III, two phalanges of pedal digit IV, and indeterminate fragmentsAn elasmarian ornithopod

Plesiosaurs Genus Species Presence Material Notes ImagesAristonectinae indet.IndeterminateSanta Marta CoveSGO.PV.6579, fragmentary postcranial skeleton preserving eight fragmentary caudal centra, two articular propodial heads (likely femora), an epipodial (likely a fibula), ventral portion of the right ilium, partial left pubis, and several rib portions Elasmosauridae indet.IndeterminateMonolithic Lake; Santa Marta Cove"MLP 11-II-20-4, one cervical vertebra preserving a partial rib; MLP 86-X-28-3, two cervical vertebrae; MLP 86-X-28-(2–6), 10 posterior cervical vertebrae articulated with three pectoral vertebrae, part of two dorsal vertebrae, ribs, and indeterminate fragments"O'Gorman, J.P. 2012. The oldest elasmosaurs (Sauropterygia, Plesiosauria) from Antarctica, Santa Marta Formation (upper Coniacian? Santonian-?upper Campanian) and Snow Hill Island Formation (upper Campanian-?lower Maastrichtian), James Ross Island. Polar Research 31. 1–10. Accessed 2019-04-13. doi:10.3402/polar.v31i0.11090IndeterminateSanta Marta CoveSGO.PV.6508, one isolated cervical vertebral centrumIndeterminateW Santa Marta CoveMN 7820-V, four vertebral centra and fragments of another six centraIndeterminateCape LambMLP 98-I-10-20, an incomplete postcranial skeleton (juvenile)IndeterminateVega IslandSDSM 78156 (a nearly complete, articulated torso, partial paddles, and neck and tail sections)Plesiosauria indet.IndeterminateThe NazeDJ.355.140, half of large water-worn vertebra, either anterior trunk or distal cervical vertebraPlesiosauroidea indet.IndeterminateThe Naze; Cape LambMLP 78-XI-1-2; MLP 78-XI-1-1, vertebrae and fragments Vegasaurus V. molyi Cape Lamb member, Vega Island MLP 93-I-5-1, postcranial skeleton preserving a complete cervical region with 54 cervical vertebrae, three pectoral vertebrae, 17 dorsal vertebrae, three sacral vertebrae, anterior and medial caudal vertebrae, pectoral and pelvic girdles, forelimbs and hind limbs, ribs, and gastroliths A plesiosaurWeddellonectia indet.IndeterminateCape LambMLP 15-I-7-6, partial skull comprising caudal half of pterygoids, basisphenoid, basioccipital, squamosal, exoccipitalopisthotic; cervical, dorsal, sacral and caudal centra; cervical and dorsal ribs, partially preserved coracoid, two partially preserved propodialsIndeterminateCape LambAMNH FARB 30877 is a largely articulated partial skeleton.

Mosasaurs +GenusSpeciesPresenceMaterialNotesImagesLiodonL. sp.Cape LambTeethA MosasaurCf. L. sp.Cape LambTeethMosasaurusM. cf. M. lemonnieriCape LambTeethA MosasaurPlioplatecarpuscf. P. sp.Cape LambMLP 93-I-3-5, small toothTaniwhasaurusFernando E. Novas; Marta S. Fernandez; Zulma B. de Gasparini; Juan M. Lirio; Héctor J. Nuñez; Pablo Puerta (2002). "Lakumasaurus antarcticus, n. gen. et sp., a new mosasaur (Reptilia, Squamata) from the Upper Cretaceous of Antarctica". Ameghiniana. 39 (2): 245–249. hdl:11336/136746. S2CID 128304133.T. antarcticusSanta Marta Cove; Al's Bird Site IAA 2000-JR-FSM-1, containing a skull measuring 72 cm (28 in) long, teeth, some vertebrae, and rib fragmentsA tylosaurcf. T. antarcticus Al's Bird SiteMLP 93-I-3-7, a tooth crownTylosaurinae indet.IndeterminateVega IslandJuvenile skull

Plants