Teyujagua

Source: Wikipedia, the free encyclopedia.

Teyujagua
Temporal range: Induan–Olenekian
↓
Skull in side view and dorsal view
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Sauria
Clade: Archelosauria
Clade: Archosauromorpha
Clade:
Crocopoda
Genus: †Teyujagua
Pinheiro et al., 2016
Type species
†Teyujagua paradoxa
Pinheiro et al., 2016

Teyujagua (named for

extinct genus of small, probably semi-aquatic archosauromorph reptile that lived in Brazil during the Early Triassic period. The genus contains the type and only known species, T. paradoxa. It is known from a well-preserved skull, and probably resembled a crocodile in appearance. It was an intermediary between the primitive archosauromorphs and the more advanced Archosauriformes, revealing the mosaic evolution of how the key features of the archosauriform skull were acquired. Teyujagua also provides additional support for a two-phase model of archosauriform radiation, with an initial diversification in the Permian followed by a second adaptive radiation in the Early Triassic.[1]

Description

Teyujagua is known only from a well preserved skull with four associated

postcranial material,[1] but it is inferred to have been a small, carnivorous quadruped that grew to a length of up to 1.5 metres (4.9 ft).[2]

Skull

The skull of Teyujagua is exceptionally well preserved and almost complete, possessing several key features of the archosauriform skull. In total it measures approximately 115 millimetres (4.5 in), with a long, broad and flattened snout. Teyujagua possesses a mosaic of characteristics intermediate between basal archosauromorphs and Archosauriformes. Primitive features include the absence of an antorbital fenestra and an open lower temporal bar, however like Archosauriformes it has serrated teeth and an exposed mandibular fenestra on the lower jaw, features previously only found in Archosauriformes.[1]

The external

trapezoidal in shape, another characteristic previously on found in archosauriforms, while the upper temporal fenestrae are slender.[1]

Close up of the snout and teeth.

A unique feature (

dentary tooth row is slightly shorter than the tooth row of the maxilla. The teeth are all laterally compressed and serrated, however unlike later Archosauriformes they are only serrated on their distal (rear) margins. The teeth are also unlike early archosauriform teeth in that they are loosely implanted in deep sockets (thecodont), whereas the earliest archosauriforms had teeth fused to their bony sockets (ankylothecodont).[1]

Discovery and Naming

Map of Brazil with the type locality of Teyujagua paradoxa within the Paraná Basin.

The holotype material, UNIPAMPA 653, was collected from an exposure in the

concretions. The specimen was collected by a team from the Paleobiology Laboratory of the Universidade Federal do Pampa (Unipampa) at the beginning of 2015,[2] and later described in a study co-authored by Dr. Felipe L. Pinheiro and others and published in Scientific Reports (Nature Publishing Group) in early 2016.[1]

The skull was noted to be exceptionally well preserved, as many other fossils from the Sanga do Cabral Formation are typically more fragmented and poorly preserved, having been reworked from slightly older sediments amongst layers of

occipital regions.[1]

The genus name Teyujagua is derived from Teyú Yaguá, one of

Guaraní translation.[4] The specific name is derived from Greek paradoxa ("paradoxical", "unexpected"), referring to its unusual combination of ancestral and derived archosauriform characteristics.[1]

Classification

In a

synapomorphies
. The results of their analysis are reproduced and simplified below.

Archosauromorpha

They also performed another analysis that included the enigmatic and poorly known

end-Permian extinction from a prior evolutionary history in the late Permian.[1][3]

Evolutionary significance

Teyujagua provides a form of transitional morphology between Archosauriformes and other earlier archosauromorphs. Features previously considered unique to Archosauriformes, including the external mandibular fenestra and serrated teeth, are found in Teyujagua, and demonstrate that the key traits of Archosauriformes were acquired in a mosaic fashion, rather than evolving all at once. Furthermore, these features broadly relate to dietary adaptations, suggesting that archosauriform skulls were first being adapted for a predatory,

hypercarnivorous lifestyle prior to the acquisition of features relating to pneumaticity (e.g. the antorbital fenestra and a closed temporal bar) that characterise later Archosauriformes.[1]

Sequence showing the mosaic acquisition of archosauriform traits in the skulls of Prolacerta, Teyujagua and Proterosuchus.

Teyujagua also supports a two-phase radiation model of archosauriform evolution at the end of the Permian and into the Triassic. The first of these radiations occurred as a phylogenetic diversification during the

end-Permian extinction, where archosauriforms increased in size, abundance and species richness, coming to occupy the dominant terrestrial roles in Triassic ecosystems. The presence of the archosauriform Eorasaurus and proterosuchid Archosaurus in the Late Permian supports the initial diversification model,[5] and Teyujagua provides unique insight to the initial acquisition of traits in their early evolution in the Permian, as the skeletal records for Permian archosauriforms are rare and fragmentary.[1][6]

Palaeoecology

The Sanga do Cabral Formation is interpreted as representing a broad, semiarid plain with localised shallow braided stream channels. The most common vertebrate fauna are the

synapsids. The formation is roughly coeval with the Lystrosaurus Assemblage Zone in Karoo, South Africa, and shares a similar composition of Early Triassic fauna.[3]

Teyujagua may have been a semi-aquatic ambush predator along the margins of lakes and streams, as suggested by the dorsally positioned nares, similar to some later Crocodyliformes.[2] The serrated teeth and external mandibular fenestra imply the development of a hypercarnivorous lifestyle as in later Archosauriformes,[1] although the limited binocular vision suggests it was a visually oriented terrestrial predator.[8]

References

  1. ^
    PMID 26965521
    .
  2. ^ a b c d "Palaeontologists discover 250 million year old new species of reptile in Brazil". University of Birmingham. March 11, 2016.
  3. ^
    doi:10.1016/j.jsames.2017.07.012
    .
  4. PMID 26965521
    .
  5. ^
    PMID 24586565
    .
  6. ^
    PMID 26083612
    .
  7. S2CID 132509118
    .
  8. ^ Oliveira, Daniel de Simão; Pinheiro, Felipe L. (2016). "O arcossauromorfo Teyujagua paradoxa possuía visão binocular?" (PDF). Boletim de Resumos. X Simpósio Brasileiro de Paleontologia de Vertebrados. Vol. 10. Rio de Janeiro. p. 121.

External links

Retrieved from "https://en.wikipedia.org/w/index.php?title=Teyujagua&oldid=1218551645"