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Temporal range: Olenekian-Norian
250–205.6 Ma
Hyperodapedon BW2.jpg
life restoration of Hyperodapedon
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Crocopoda
Order: Rhynchosauria
Osborn 1903

Rhynchosaurs were a group of Triassic diapsid reptiles from the group Archosauromorpha, meaning they were distantly related to the archosaurs.[1]


Models of Staurikosaurus and rhynchosaur

Rhynchosaurs were herbivores, and at times abundant (in some fossil localities accounting for 40 to 60% of specimens found), with stocky bodies and a powerful beak. Early primitive forms, like Mesosuchus and Howesia, were generally small and more typically lizard-like in build, and had skulls rather similar to the early diapsid Youngina, except for the beak and a few other features. Later and more advanced genera grew to medium to medium large size, up to two meters in length. The skull in these forms were short, broad, and triangular, becoming much wider than long in the most advanced forms like Hyperodapedon (= Scaphonyx), with a deep cheek region, and the premaxilla extending outwards and downwards to form the upper beak. The broad skull would have accommodated powerful jaw muscles. The lower jaw was also deep, and when the mouth was closed it clamped firmly into the maxilla (upper jaw), like the blade of a penknife closing into its handle. This scissors-like action would have enabled rhynchosaurs to cut up tough plant material.

The teeth were unusual; those in the maxilla and palate were modified into broad tooth plates. The hind feet were equipped with massive claws, presumably for digging up roots and tubers by backwards scratching of the hind limbs.

Like many animals of this time, they had a worldwide distribution, being found across Pangea. These abundant animals might have died out suddenly at the end of the Carnian (Middle of the Late Triassic period), perhaps as a result of the extinction of the Dicroidium flora on which they may have fed. On the other hand, Spielmann, Lucas and Hunt (2013) described three distal ends of humeri from early-mid Norian Bull Canyon Formation in New Mexico, which they interpreted as bones of rhynchosaurs belonging to the species Otischalkia elderae; thus, the fossils might indicate that rhynchosaurs survived until the Norian.[2]



Genus Species Age Location Unit Notes


A. navajoi


 US (Arizona)

Moenkopi Formation


B. mariantensis



Santa Maria Formation

Previously known as the "Mariante Rhynchosaur".


B. sidensis

late Anisian

 UK (England)

Otter Sandstone Formation


E. wolvaardti

early Anisian

 South Africa

Burgersdorp Formation


F. spenceri

late Anisian

 UK (England)

Otter Sandstone Formation


H. browni

early Anisian[3]

 South Africa

Burgersdorp Formation


H. gordoni


 UK (Scotland)

Lossiemouth Sandstone Formation

Six valid species has been named, the most of any rhynchosaur.

H. huenei



Santa Maria Formation

H. huxleyi



Lower Maleri Formation

H. mariensis



Santa Maria Formation
Ischigualasto Formation

H. sanjuanensis



Ischigualasto Formation
Santa Maria Formation

H. tikiensis



Tiki Formation


I. genovefae



Makay Formation (Isalo II)


M. kuttyi



Yerrapalli Formation


L. brodiei


 UK (England)

Bromsgrove Sandstone Formation


M. browni

early Anisian[3]

 South Africa

Burgersdorp Formation


N. colletti

early Induan

 South Africa

Katberg Formation

The earliest known species, and the only Early Triassic representative.[3]


O. bairdi

latest Carnian?-earliest Norian?

 Canada (Nova Scotia)

Wolfville Formation


O. elderae

late Carnian

 US (Texas)

Dockum Group

A nomen dubium


R. articeps


 UK (England)

Tarporley Siltstone Formation


S. stockleyi

late Anisian


Manda Formation


S. stockleyi

Middle - Late Triassic


Tunduru district


T. sulcognathus

early Norian


Caturrita Formation

The latest surviving species, and the only Norian rhynchosaur.

Hyperodapedon huxleyi (=Paradapedon)
Mesosuchus browni
Skull of Rhynchosaurus articeps


Skull of a rhynchosaur, in Educational Museum Gama D'Eça.
Illustration of the ventral surface of a tooth plate of Hyperodapedon.

The Rhynchosauria included a single family, named Rhynchosauridae. All rhynchosaurs, apart from the four Early and Middle Triassic monospecific genera, Eohyosaurus, Mesosuchus, Howesia and Noteosuchus, are included in this family.[3] Hyperodapedontidae named by Lydekker (1885) was considered its junior synonym.[4] However, Langer et al. (2000) noted that Hyperodapedontidae was erected by Lydekker to include Hyperodapedon gordoni and H. huxleyi, clearly excluding Rhynchosaurus articeps, which was the only other rhynchosaur known at that time. Thus, they defined it as the stem-based taxon that includes all rhynchosaurs more closely related to Hyperodapedon than to Rhynchosaurus.[5]

Within Hyperodapedontidae, which is now a subgroup of Rhynchosauridae, two subfamilies have been named. Stenaulorhynchinae named by Kuhn (1933) is defined sensu Langer and Schultz (2000) to include all species more closely related to Stenaulorhynchus than to Hyperodapedon. Hyperodapedontinae named by Chatterjee (1969) was redefined by Langer et al. (2000) to include "all rhynchosaurs closer to Hyperodapedon than to "Rhynchosaurus" spenceri" (now Fodonyx).[6]

The cladogram below is based on Schultz et al. (2016) which is the most genera inclusive rhynchosaur phylogenetic analysis to date,[6] with the position of Noteosuchus taken from other recent analyses (since it was removed in Schultz et al. (2016)), all in consensus with one another.[3][7]


Noteosuchus colletti

Mesosuchus browni

Howesia browni

Eohyosaurus wolvaardti


Rhynchosaurus articeps


Ammorhynchus navajoi

Mesodapedon kuttyi

Brasinorhynchus mariantensis

Stenaulorhynchus stockleyi

Bentonyx sidensis

Langeronyx brodiei

Fodonyx spenceri


Isalorhynchus genovefae

Teyumbaita sulcognathus

Hyperodapedon spp.


  1. ^ Ezcurra, Martín D.; Montefeltro, Felipe; Butler, Richard J. (2016). "The Early Evolution of Rhynchosaurs". Frontiers in Ecology and Evolution. 3. doi:10.3389/fevo.2015.00142. ISSN 2296-701X.
  2. ^ Justin A. Spielmann; Spencer G. Lucas & Adrian P. Hunt (2013). "The first Norian (Revueltian) rhynchosaur: Bull Canyon Formation, New Mexico, U.S.A." (PDF). New Mexico Museum of Natural History and Science Bulletin. 61: 562–566.
  3. ^ a b c d e f Richard J. Butler; Martín D. Ezcurra; Felipe C. Montefeltro; Adun Samathi & Gabriela Sobral (2015). "A new species of basal rhynchosaur (Diapsida: Archosauromorpha) from the early Middle Triassic of South Africa, and the early evolution of Rhynchosauria". Zoological Journal of the Linnean Society. 174 (3): 571–588. doi:10.1111/zoj.12246.
  4. ^ Benton, M. J. (1985). "Classification and phylogeny of the diapsid reptiles". Zoological Journal of the Linnean Society. 84 (2): 97–164. doi:10.1111/j.1096-3642.1985.tb01796.x.
  5. ^ Max C. Langer & Cesar L. Schultz (2000). "A new species of the Late Triassic rhynchosaur Hyperodapedon from the Santa Maria Formation of south Brazil". Palaeontology. 43 (6): 633–652. doi:10.1111/1475-4983.00143.
  6. ^ a b Cesar Leandro Schultz; Max Cardoso Langer & Felipe Chinaglia Montefeltro (2016). "A new rhynchosaur from south Brazil (Santa Maria Formation) and rhynchosaur diversity patterns across the Middle-Late Triassic boundary". Paläontologische Zeitschrift. in press (3): 593–609. doi:10.1007/s12542-016-0307-7. hdl:11449/161986. S2CID 130644209.
  7. ^ Ezcurra MD. (2016) The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms. PeerJ, 4:e1778 [1]


External links[edit]

Data related to Rhynchosauria at Wikispecies