Monday, November 7, 2016

[Paleontology • 2017] Kaikaifilu hervei • A New Large Mosasaur (Squamata, Mosasauridae) from the upper Maastrichtian of Antarctica

Kaikaifilu hervei 
Otero, Soto-Acuña, Rubilar-Rogers & Gutstein, 2017  

• A new mosasaur from Antarctica.
• The second skull known in the continent.
• A new genus and species of a large austral mosasaur.

We present a large, fragmentary skull and the humerus of a mosasaur (Squamata, Mosasauroidea) recovered from upper Maastrichtian beds of the López de Bertodano Formation in Marambio (=Seymour) Island, Antarctica. The material belongs to a large, adult individual with marked heterodonty as well as unusual humeral features. Different phylogenetic analyses returned the studied specimen within the Tylosaurinae, while the unique features of the skull and humerus allow distinguish it from the unique Antarctic known tylosaurine species, Taniwhasaurus antarcticus (Novas et al., 2002), as well as from other known Late Cretaceous mosasaurids from the Southern Hemisphere, thus, justifying the erection of a new taxon, Kaikaifilu hervei gen. et. sp. nov. The different dental types documented in the specimen studied have been previously recorded through isolated teeth from the same locality and were subsequently referred to several genera. This new find and its importance to comprehend the previously known fragmentary records strongly suggests that the diversity of Antarctic mosasaurids could be more reduced than previously interpreted, including taxa which are different to the genera and species from the Northern Hemisphere. The new material represents the youngest occurrence of tylosaurines in Antarctica.

Keywords: Marine reptiles; Mosasaurs; Upper Cretaceous; Marambio Island; Antarctic Peninsula

 Systematic paleontology

Squamata Oppel, 1811
Mosasauridae Gervais, 1853

Russellosaurina Polcyn and Bell, 2005
Tylosaurinae Williston, 1897

Kaikaifilu gen. nov.
Tylosaurinae indet.: In Otero, 2012.
Tylosaurinae gen. et sp. nov.: Otero et al., 2015

Type species: as for the only known species within the genus, Kaikaifilu hervei sp. nov., below.

Derivation of name. From the Mapudungun language of the ancient people of southern South America. From the Mapuche cosmology, Kai-Kai filú is the almighty giant reptile owner of the seas, rival of Treng-Treng filú, both creators of the lands through their continuous fight that causes the earthquakes, volcanoes, tsunamis and all the events that molded the earth where we live (pronunciation: Khai-khai feelóo).

Kaikaifilu hervei sp. nov.

Holotype. SGO.PV.6509. Fragmentary skull preserved in several blocks, including part of the maxillae and the premaxillar, frontal, prefrontals, part of the parietal, partial cast of the braincase, cast of the right orbit, a portion of the right pterygoid, a partial cast of the meckellian canal of one dentary, near 30 isolated teeth, fragments of the mandible, and the proximal part of the left humerus.
Type Locality. Marambio Island, Antarctica, about 1500 m south from the López de Bertodano Bay.
Horizon and Age. López de Bertodano Formation, Klb9 sensu Macellari (1988), Manumiella bertodano Interval Zone ( Bowman et al., 2012) and Pachydiscus riccardi Zone ( Olivero, 2012), upper Maastrichtian.

Derivation of the name. Honoring Dr. Francisco Hervé, Chilean geologist, for their major contribution to the knowledge of the geology of Chile and Antarctic Peninsula.

Diagnosis. Specimen with the following unique combination of characters: Presence of a prominent lateral process anterior to the orbits, conformed by the posterior end of the prefrontal and the anterior end of the postorbitofrontal; well-marked heterodonty including both faceted and non-faceted functional teeth with very soft striations; articular head of the humerus very thick dorsoventrally; K. hervei differs from other mosasaurids from the WBP in the following features: it differs from Tylosaurus (‘Leiodon’) haumuriensis and from the genus Taniwhasaurus (Ta. antarcticus, Ta. oweni and Ta. mikasaensis) by possessing a well-marked heterodonty, condition absent in the two latter genera; it also differs from these taxa on the frontal midline forming an internarial process which is absent in Ta. mikasaensis (premaxillar extends far beyond external naris) and seems to be absent in Ta. antarcticus; K. hervei differs from Moanasaurus mangahouangae in the outline of the frontal which is axially shorter in the latter and without anterolateral concave margins; K. hervei also differs from Rikisaurus tehoensis in having a frontal contacting the pineal foramen, and by the possession of a preorbital constriction of the rostrum. Unique known specimen here referred to K. hervei comprises the largest known skull of a mosasauroid from the Southern Hemisphere.

SGO.PV.6509 comprises a fragmentary skull and fragmentary humerus of a single specimen recovered from upper Maastrichtian levels (lower Klb9 unit) of the López de Bertodano Formation in Marambio Island, Antarctica. This is here identified as a large mosasaurid with prominent anterorbital processes, an axially elongated and triangular frontal that extends between the external naris, a well-marked heterodonty and a dorsoventrally massive humerus. Morphological features of SGO.PV.6509 differ from all known mosasaurids from the Southern Hemisphere and especially from the better known austral tylosaurine, Taniwhasaurus antarticus. Thus, a new genus and species, Kaikaifilu hervei, is proposed here. This new skull from the upper Mastrichtian of Antarctica represents the best evidence on the presence of very large tylosaurines on high latitudes (65°) of the Southern Hemisphere prior to the K/Pg boundary. Previous to this research, this clade remained poorly documented in high latitudes. The marked heterodonty of SGO.PV.6509 suggest that several taxa previously reported from the Upper Cretaceous of Antarctica and based on isolated teeth, should be reviewed under the new evidence, since most of them appear to match with the different dental types of the specimen here described.

 Rodrigo A. Otero, Sergio Soto-Acuña, David Rubilar-Rogers and Carolina S. Gutstein. 2017. Kaikaifilu hervei gen. et sp. nov., A New Large Mosasaur (Squamata, Mosasauridae) from the upper Maastrichtian of Antarctica. Cretaceous Research. In Press.  DOI:  10.1016/j.cretres.2016.11.002

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