Tahora Formation

Tahora Formation
Stratigraphic range: Santonian-Maastrichtian (Piripauan) ~85.8–66  Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Unit of	Tinui Group
Sub-units	Maungataniwha Sandstone Member, Mutuera Member, Houpapa Member
Underlies	Whangai Formation
Overlies	Urewera Group or Matawai Group
Thickness	~500 m (1,600 ft) [1]
Lithology
Primary	Sandstone, conglomerate
Other	Siltstone
Location
Coordinates	39°00′S176°48′E / 39.0°S 176.8°E / -39.0; 176.8
Approximate paleocoordinates	59°24′S168°48′W / 59.4°S 168.8°W / -59.4; -168.8
Region	North Island
Country	New Zealand
Extent	Gisborne
Type section
Named for	Tahora Station
Tahora Formation (New Zealand)

The Tahora Formation is a Late Cretaceous geologic formation that outcrops in northeastern New Zealand near Napier. ^{[2] [3]} It is Haumurian in age according to the New Zealand geologic time scale (mainly Campanian, but ranging from Santonian to lower Maastrichtian). It forms part of the Upper Cretaceous to Teurian (Danian) (lower Paleocene) Tinui Group. It unconformably overlies the Jurassic to Lower Cretaceous Urewera Group or the Upper Cretaceous Matawai Group. It is conformably overlain by the Haumurian to Teurian Whangai Formation. It consist of three members, the Maungataniwha Sandstone Member, the Mutuera Member and the Houpapa Member. ^[1] It is named for Tahora Station, south of Matawai in the Gisborne Region. The aptly named Maungataniwha (Māori for "mountain of monsters") Sandstone Member is known for its rich reptile fossil remains, first investigated by amateur palaeontologist Joan Wiffen.

Depositional environment

The whole of the Tinui Group is interpreted to be an upper Cretaceous transgressive sequence. The Maungataniwha Sandstone Member was deposited in a very shallow water to beach environment. The siltstones of the time-equivalent Mutuera Member are thought to have been deposited in a mid to outer shelf environment. The Houpapa Member is interpreted to be the fill of local channels cut into the underlying strata. ^[1]

Fossil content

Vertebrates

Indeterminate dinosaur remains have been recovered from the formation, including indeterminate theropod, sauropod, and ornithischian remains. ^[4] Other fossils found in the Tahora Formation include plesiosaurs and pterosaurs. ^[5]

Because of a lack of material, the exact taxonomic placement of the theropod from the Tahora Formation is uncertain, although its discoverer Joan Wiffen considered it possibly a megalosaurid, at the time a poorly defined group of unspecialized large carnivorous dinosaurs. The vertebra was described by Molnar (1981), and was considered an indeterminate theropod by Agnolin et al. (2010). ^{[6] [7]}

Reptiles

Plesiosaurs

Plesiosaurs recorded from Tahora Formation
Genus	Species	Member/Location	Material	Description	Image
Tuarangisaurus [8]	T. keyesi	Maungataniwha Sandstone	A nearly complete skull, mandible, rear skull elements, and nine anterior-most cervical vertebrae from the same individual.	An elasmosaurid.

Mosasaurs

Mosasaurs recorded from Tahora Formation
Genus	Species	Member/Location	Material	Description	Image
Moanasaurus [9]	M. mangahouangae	Maungataniwha Sandstone [10]	A disarticulated skull, vertebrae, ribs and flipper bones.	A Mosasaurini mosasaur.

Pterosaurs

Pterosaurs recorded from Tahora Formation
Genus	Species	Member/Location	Material	Description	Image
Azhdarchidae [11]	Indeterminate	Maungataniwha Member, Mangahouanga Stream	Distal left ulna, coracoid fragment

Dinosaurs

Dinosaurs recorded from Tahora Formation
Genus	Species	Member/Location	Material	Description	Image
Ankylosauria [12] [7]	Indeterminate	Maungataniwha Member, Mangahouanga Stream	An incomplete rib and two caudal veterbral centra
Ornithopoda [7]	Indeterminate	Maungataniwha Member, Mangahouanga Stream	Partial right ilium
Sauropoda [12]	Indeterminate	Maungataniwha Member	A rib fragment
Theropoda [7] [12]	Indeterminate	Maungataniwha Member, Mangahouanga Stream	Caudal vertebra, pedal phalanx

Invertebrates

Invertebrates found in the formation include beetles, ^[13] ammonites, annelids, belemnites, bivalves, brachiopods, crinoids, crustaceans, gastropods, nautiloids and scaphopods. ^[3]

See also

• List of dinosaur-bearing rock formations
  • List of stratigraphic units with indeterminate dinosaur fossils
• Geology of the Raukumara Region
• Stratigraphy of New Zealand
• South Polar region of the Cretaceous

References

1. Isaac M.J., Moore P.R. & Joass Y.J. (1991). "Tahora Formation: The basal facies of a Late Cretaceous transgressive sequence, northeastern New Zealand". New Zealand Journal of Geology and Geophysics. 34 (2): 227–236. Bibcode:1991NZJGG..34..227I. doi:10.1080/00288306.1991.9514460.
2. "Tahora Formation". New Zealand Stratigraphic Lexicon. GNS Science. Retrieved 25 May 2013.
3. Vajda V. & Raine J.I. (2010). "A palynological investigation of plesiosaur-bearing rocks from the Upper Cretaceous Tahora Formation, Mangahouanga, New Zealand". Alcheringa. 34 (3): 359–374. Bibcode:2010Alch...34..359V. doi:10.1080/03115518.2010.486642.
4. Weishampel, et al. (2004). "Dinosaur distribution" Pp. 517-607. in Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN   0-520-24209-2. " Pp. 517-607.
5. Mangahouanga Stream at Fossilworks.org
6. Molnar,R.E.1981.AdinosaurfromNewZealand.Pp.91–96in M.M.Cresswell&P.Vella(eds)GondwanaFive:Proceeding of the Fifth International Gondwanan Symposium. Wellington. A. A., Balkema, Rotterdam.
7. Agnolin, Federico L.; Ezcurra, Martín D.; Pais, Diego F.; Salisbury, Steven W. (2010-05-24). "A reappraisal of the Cretaceous non-avian dinosaur faunas from Australia and New Zealand: evidence for their Gondwanan affinities". Journal of Systematic Palaeontology. 8 (2): 257–300. doi:10.1080/14772011003594870. ISSN   1477-2019.
8. O'Gorman, José P.; Otero, Rodrigo A.; Hiller, Norton; Simes, John; Terezow, Marianna (March 2017). "Redescription of Tuarangisaurus keyesi (Sauropterygia; Elasmosauridae), a key species from the uppermost Cretaceous of the Weddellian Province: Internal skull anatomy and phylogenetic position". Cretaceous Research. 71: 118–136. doi:10.1016/j.cretres.2016.11.014.
9. O'Gorman, J. P.; Bona, P.; Canale, J. I.; Tineo, D. E.; Fernández, M. S.; Cárdenas, M.; Reguero, M. (2023). "A new mosasaurine specimen (Squamata, Mosasauridae) from the Upper Cretaceous of Antarctica with comments on the Weddellian diversity of Mosasaurinae". Alcheringa: An Australasian Journal of Palaeontology. 47 (2): 211–220. Bibcode:2023Alch...47..211O. doi:10.1080/03115518.2023.2203739. S2CID   258691668.
10. Wiffen, J. (1980). "Moanasaurus, a new genus of marine reptile (Family Mosasauridae) from the Upper Cretaceous of North Island, New Zealand". New Zealand Journal of Geology and Geophysics. 23 (4): 507–528. doi: 10.1080/00288306.1980.10424122 .
11. Pentland, Adele H.; Poropat, Stephen F. (July 2023). "A review of the Jurassic and Cretaceous Gondwanan pterosaur record". Gondwana Research. 119: 341–383. doi:10.1016/j.gr.2023.03.005.
12. Molnar, R.E.; Wiffen, J. (December 1994). "A Late Cretaceous polar dinosaur fauna from New Zealand". Cretaceous Research. 15 (6): 689–706. doi:10.1006/cres.1994.1038.
13. GS 14182, Mangahouanga Stream (V19/f133) at Fossilworks.org