''Tuarangisaurus'' ( "ancient" + "lizard") is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

elasmosaurid Elasmosauridae, often called elasmosaurs or elasmosaurids, is an extinct family of plesiosaurs that lived from the Hauterivian stage of the Early Cretaceous to the Maastrichtian stage of the Late Cretaceous period (c. 130 to 66 mya). The taxo ...

known from

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

. The

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...

and only known species is ''Tuarangisaurus keyesi'', named by "Pont" Wiffen,

Joan Wiffen Joan Wiffen (née Pederson; 4 February 1922 – 30 June 2009) was a self-taught New Zealand paleontologist known for discovering the first dinosaur fossils in New Zealand. Early life Wiffen was born in 1922 and was brought up in Havelock North, ...

and Bill Moisley in

1986 The year 1986 was designated as the International Year of Peace by the United Nations. Events January * January 1 ** Aruba gains increased autonomy from the Netherlands by separating from the Netherlands Antilles. ** Spain and Portugal en ...

. The specific name honours Ian W. Keyes of the New Zealand Geological Survey.

Discovery

''Tuarangisaurus'' is known from the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

NZGS CD425, a nearly complete

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

and

mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

, and from NZGS CD426, rear skull elements and nine anterior-most

cervical vertebra In tetrapods, cervical vertebrae (: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In sauropsid s ...

e from the same individual. Some

postcrania The postcranium ("behind the cranium"; plural: postcrania) or postcranial skeleton in zoology and vertebrate paleontology is the skeleton apart from the skull. The postcranium encompasses the axial skeleton, which includes the entirety of the verte ...

l remains of juveniles were also provisionally attributed to ''Tuarangisaurus'', with one specimen (NZGS CD427) containing at least thirty gastroliths. It was on 20 March 1978 collected by amateur paleontologists from the Maungataniwha Sandstone Member of the

Tahora Formation The Tahora Formation is a Late Cretaceous geologic Formation (geology), formation that outcrops in northeastern New Zealand near Napier, New Zealand, Napier. It is Haumurian in age according to the New Zealand geologic time scale (mainly Campania ...

, dating to the upper

Campanian The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...

to lower

Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...

stage of the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

. A second species, ''T. australis'', was named in 2005; however, it was moved to the genus '' Eromangasaurus'' in 2007, becoming the senior synonym of ''E. carinognathus''. Another species, ''T.? cabazai'', was collected during the early 2000s and was also placed in ''Tuarangisaurus'' by Gasparini, Salgado and Casadio in 2003; however, it was most recently reassigned to an indeterminate aristonectine. In 2017, a complete specimen (CM Zfr 115), originally belonging to '' Mauisaurus'', has been reassigned to this genus. In 2018, Otero and colleagues redescribed the juvenile specimen NZGS CD427 elucidating the ontogeny of this plesiosaur. The specimen had many features common with the holotype, but it differed in the orientation of the maxilla along with the number of teeth present in it.

Description

''Tuarangisaurus'' was a medium-sized plesiosaur, with a complete specimen (CM Zfr 115) measuring over long. The preserved skull measured about long, and its total skull length is estimated to have been long. It can be distinguished from all other known elasmosaurids by a unique combination of characteristics as well as two otherwise unknown traits: the ectopterygoid has a long process directed towards the back, and a large boss of bone underneath. A

stapes The ''stapes'' or stirrup is a bone in the middle ear of humans and other tetrapods which is involved in the conduction of sound vibrations to the inner ear. This bone is connected to the oval window by its annular ligament, which allows the f ...

is present in the holotype; this bone was previously thought to be absent from elasmosaurids.

Classification

''Tuarangisaurus'' was initially assigned to the

Elasmosauridae Elasmosauridae, often called elasmosaurs or elasmosaurids, is an extinct family of plesiosaurs that lived from the Hauterivian stage of the Early Cretaceous to the Maastrichtian stage of the Late Cretaceous period (c. 130 to 66 mya). The taxo ...

; one study found it to be a close relative of '' Callawayasaurus''. A phylogenetic analysis of plesiosaurs run by O'Gorman and colleagues in 2016 reaffirmed that ''Tuarangisaurus'' was an

, but rejected a close relationship with ''Callawayasaurus''. Its position within the Elasmosauridae according to this analysis is shown below.

References

{{Taxonbar, from=Q18374302 Late Cretaceous plesiosaurs Extinct reptiles of New Zealand Fossil taxa described in 1986 Elasmosauridae Plesiosaurs of Oceania Sauropterygian genera

Discovery

Description

Classification

See also

References