Palæos:		Unit 160: Temnospondyli
The Vertebrates		500: Rhinesuchids  & Capitosaurs

Rhinesuchids & Capitosaurs

TETRAPODA
|--+--LEPOSPONDYLI
|  `--REPTILOMORPHA
|
Temnospondyli
|--Edopoidea
`--+--Euskelia
   `--Limnarchia
      |--Dvinosauria
      `--Stereospondyli
         |--Rhinesuchidae
         |  |--Rhinesuchus
         |  |--Laccocephalus
         |  |--Uranocentradon 
         |  `--Broomistega
         `--+--Capitosauria
            |  |--Lydekkerinidae
            |  `--+--Mastodonsaurus
            |     `--Capitosauridae
            `--Trematosauria
               |--Trematosauroidea
               `--+--Metoposauroidea
                  `--+--Plagiosauroidea
                     `--+--Rhytidosteidae
                        `--Brachyopoidea

1. Broomistega X
2. Capitosauria X
3. Capitosauridae X
4. Laccocephalus X
5. Lydekkerinidae X
6. Mastodonsaurus X
7. Rhinesuchidae X
8. Rhinesuchus X
9. Uranocentradon X

Descriptions

Rhinesuchidae: 

Range: Late Permian to Early Triassic of South Africa.

Phylogeny: Stereospondyli:: (Capitosauria + Trematosauria) + *: Rhinesuchus + Laccocephalus + Uranocentradon + Broomistega.

Introduction: The Rhinesuchids are relatively massive temnospondyls known, as yet, only from the later Permian and earliest Triassic of South Africa. They were large to very large (200-400 cm) flat-headed, semi- or perhaps completely aquatic tetrapods, transitional between the eryopids and the Capitosaurs, and fulfilling the same ecological role of large semi- to fully-aquatic predator. The eyes are small and face upwards, located towards the rear of the skull. The pubis is ossified, but the wrist and ankles only seem to be partially so. We may imagine that the animal would lie motionless on a pond bottom, then lunch at fish or smaller tetrapods that would swim past or above it. Carroll (1988) lists six genera, which may include junior synonyms.  MAK

As the illustration from Müller (1968) shows, the Rhinesuchids are morphologically transitional between early Permian eryopids and Triassic Capitosaurs and mastodonsaurs. Note the sequence from the short, heavy skull of the semi-terrestrial Eryops (left) to the large flat light (notice the large vacuities or gaps in the bone of the roof of the mouth) late Triassic Cyclotosaurus.  MAK 010423, ATW020723.

Rhinesuchus from the Daptocephalus - Dicynodon Zone.  Image © Bernard Price Institute for Palaeontological Research, University of the Witwatersrand, Johannesburg.

Range: Late Permian of South Africa.

Phylogeny: Rhinesuchidae: Laccocephalus + Uranocentradon + Broomistega + *. 

Rhinesuchus whaitsi Broom 1908
Horizon: this and other species from the Tapinocephalus, Cistecephalus, and Daptocephalus zones, Lower and Middle Beaufort Beds, South Africa
Age: Capitanian to Late Wuchiapingian / Early Changhsingian (middle to late Permian)
Place: central Gondwana
Weight: 100 kg 

Comments: The mouth is armed with numerous tiny teeth on the palatine (roof of mouth), even smaller teeth on the pterygoid and parasphenoid bones of the hard palate. These animals presumably fed on fish and smaller tetrapods. Other similar species (perhaps transferred to other genera) include Rhinesuchus africanus Lydekker and R. nyasaensis Haughton (from the Karoo of Nyasaland). vonZittel (1932). Rhineceps from the Cistecephalus zone is a similar (or perhaps synonymous) genus. (MAK 010423).

Links: South African Museum - An Introduction to the Fossil Wealth of the Nuweveld Mountains; paleontology; fossils; South Africa; Fossil Picture Gallery. ATW020808.

Laccocephalus:

Range: Late Permian or Early Triassic of South Africa.

Phylogeny: Rhinesuchidae: Rhinesuchus + Uranocentradon + Broomistega + *. 

Laccocephalus Watson.
Horizon: Daptocephalus zone, Beaufort Beds, Orange Free State, South Africa
Age: ? Changhsingian
Place: central Gondwana

Comments: previously included with Uranocentradon in the family Uranocentrodontidae. Carroll lists this genus as early Triassic, but according to Anderson & Cruikshank (1978) it is late Permian. Perhaps it is from the early Changhsingian. (MAK 010423).

Uranocentradon:

Range: Late Permian or Early Triassic. 

Phylogeny: Rhinesuchidae: Rhinesuchus + Laccocephalus + Broomistega.+ *.

Uranocentradon senekalensis van Hoepen 1911
Horizon: Lower Lystrosaurus Zone, Beaufort Beds, Orange Free State, South Africa
Age: Latest Changhsingian or Induan
Place: central Gondwana
Known remains: several complete specimens
Length: skull about 50cm. Anderson & Anderson (1970). Overall length 375 cm. vonZittel (1932).

Comments: The skull is greatly flattened. The palatine (on the roof of the mouth) is equipped with a single row of large teeth. The pelvis is very like that of Eryops (indicating terrestrial ability), but the wrist and ankles are incompletely ossified (implying an aquatic existence). Presumably this animal was capable of crawling about on land when need be, but preferred to spend its time in water. vonZittel (1932). This was the last large Rhinesuchid. All the known specimens occur in a single locality and horizon, with specimens of Lystrosaurus occurring in horizons immediately above and below. Romer (1947) places Uranocentradon in its own family, the Uranocentrodontidae. Carroll and Winer (1977) place it in the Rhinesuchidae. The Fossil Record II retains the family Uranocentrodontidae.  MAK

References: Anderson & Anderson (1970); Romer (1947); vonZittel (1932).

Broomistega: 

Range: Early Triassic

Phylogeny: Rhinesuchidae: Rhinesuchus + Laccocephalus + Uranocentradon + *.

Broomistega putterilli (Broom 1930) synonym: Lydekkerina putterilli Broom 1930 
Horizon: Lystrosaurus Zone, Beaufort Beds, South Africa
Age: Induan
Place: central Gondwana
Length: small

Comments: Previously regarded as a species of Lydekkerina or a juvenile Uranocentrodon, this small aquatic tetrapod is now regarded as a paedomorphic rhinesuchid. This means that most of the Lystrosaurus Zone 'amphibians' are now paedomorphic miniature species, perhaps owing to the small size and shallowness of the ponds, lakes, and streams of this period.  MAK

Links: New rhynchosaur & temnospondyls

References: Shishkin & Rubidge (2000).

Capitosauria: 

Range: Early Triassic to Late Triassic. 

Phylogeny: Stereospondyli::: Trematosauria + *: Lydekkerinidae + (Mastodonsaurus + Capitosauridae) 

Introduction: The capitosaurs were a large and important group of large to huge flat-headed semi-aquatic or completely aquatic tetrapods.   Some forms reached three to four or even five metres in length.  They dominated the freshwater ponds, lakes and rivers of the Triassic, but were pushed to extinction by the carnivorous phytosaurs which appeared at the end of the period.  MAK

Characters: Very flat skulls, small limbs, ossification reduced (obligate aquatic); some very large forms. ATW990919.

Lydekkerinidae: Chomatobatrachus, Lydekkerina

Range: Triassic of South Africa & Australia. 

Phylogeny: Capitosauria: (Mastodonsaurus + Capitosauridae) + *.

Mastodonsaurus: Jaeger 1852;  

Range: Middle Triassic of Europe.

Phylogeny: Capitosauria:: Capitosauridae + *.

Characters: ~6m; 

Links: Mastodonsaurus; Triassico; Adventures in Etymology- Oplosaurus, Mastodonsaurus; Mastodonsaurus (Bullyland) (toy); amphibien keuper trias fossilien (most of jaw); fossil des monats trias (Best on the Web); Triassic (a bit hokey, but interesting); SITE Name- Ladram Bay to Sidmouth Parish- Sidmouth Local ...; Some Amphibian and Reptilian Remains (1859); Waldenburg Online - Bildung, Kultur & Vereine - Urweltmuseum.  ATW030621. 

Capitosauridae: Cyclotosaurus, Eryosuchus, Kestrosaurus, Paracyclotosaurus, Parotosuchus

Range: Early to Late Triassic of Russia, Australia & South Africa.

Phylogeny: Capitosauria:: Mastodonsaurus + *.

The capitosaurs were large aquatic tetrapods common throughout much of the Triassic  The various species are distinguished by relative proportions of the snout, the ornamentation or sculpting on the skull, and the degree of closure of the otic notch.

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checked ATW060327