''Tuarangisaurus'' ( mi, tuarangi "ancient" + el, σαῦρος, sauros "lizard") is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

elasmosaurid Elasmosauridae is an extinct family of plesiosaurs, often called elasmosaurs. They had the longest necks of the plesiosaurs and existed from the Hauterivian to the Maastrichtian stages of the Cretaceous, and represented one of the two groups of p ...

known from

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

. The type and only known species is ''Tuarangisaurus keyesi'', named by Wiffen and 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 ente ...

Discovery

Aristonectine (formerly Tuarangisaurus cabazai)

''Tuarangisaurus'' is known from the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

NZGS CD425, a nearly complete

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

and

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

, and from NZGS CD426, nine anterior-most

cervical vertebra In tetrapods, cervical vertebrae (singular: 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 sau ...

e. Some

postcrania Postcrania (postcranium, adjective: postcranial) in zoology and vertebrate paleontology is all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g. of dinosaurs or other extinct tetrapods, consist of partial or isolated sk ...

l remains of juveniles were also attributed to ''Tuarangisaurus''. It was collected from the Maungataniwha Sandstone Member of the

Tahora Formation The Tahora Formation is a Late Cretaceous geologic formation that outcrops in northeastern New Zealand near Napier. It is Haumurian in age according to the New Zealand geologic time scale (mainly Campanian, but ranging from Santonian to lower Maas ...

, 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. Campanian s ...

to lower

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from ...

stage of the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger 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 ''creta'', the ...

. A second species, ''T. australis'', was named in 2005; however, it was moved to the genus ''

Eromangasaurus ''Eromangasaurus'' is an extinct genus of elasmosaurid known from northern Queensland of Australia. Description ''Eromangasaurus'' is a medium-sized elasmosaurid, measuring in length and in body mass. It is known from the holotype QM F11 ...

'' in 2007, becoming the senior synonym of ''E. carinognathus''. A third species, ''T.? cabazai'', was also referred to ''Tuarangisaurus'' by the original description; however, it was most recently reassigned to an indeterminate aristonectine. In 2018, Otero et al. reported a juvenile specimen which indicated 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'' is measured up to in total body length and in body mass. 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 animals 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 foot ...

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

Classification

''Tuarangisaurus'' was initially assigned to the

Elasmosauridae Elasmosauridae is an extinct family of plesiosaurs, often called elasmosaurs. They had the longest necks of the plesiosaurs and existed from the Hauterivian to the Maastrichtian stages of the Cretaceous, and represented one of the two groups of p ...

; one study found it to be a close relative of ''

Callawayasaurus ''Callawayasaurus'' is a genus of plesiosaur from the family Elasmosauridae. When the holotype was first described by Samuel Paul Welles in 1962, it was described as ''Alzadasaurus colombiensis'' before being moved into its current genus by Ken ...

''. A new phylogenetic analysis of plesiosaurs 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 Elasmosaurids Plesiosaurs of Oceania Sauropterygian genera

Discovery

Description

Classification

See also

References