Albanerpeton

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Albanerpeton
Temporal range: Aptian–Gelasian
Albanerpeton inexpectatum
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Allocaudata
Family: Albanerpetontidae
Genus: Albanerpeton
Estes and Hoffstetter, 1976
Species
  • A. inexpectatum Estes and Hoffstetter, 1976. Re-described by Gardner, 1999. (type)
  • A. galaktion Fox and Naylor, 1981
  • A. nexuosus Estes, 1981
  • A. arthridion Fox and Naylor, 1982
  • A. cifellii Gardner, 1999
  • A. gracilis Gardner, 2000
  • A. pannonicus Venczel and Gardner, 2005
  • A. ektopistikon Carrano et al., 2022

Albanerpeton is an

paraphyletic.[4][5]

History and Discovery

Albanerpeton was first described by Estes and Hoffstetter in 1976. However, the genus was re-described by Gardner in 1999 after a large collection of jaws and frontals from

saltatorial amphibians in general.[7] A. inexpectatum had many unique characteristics, distinct from salamanders and other amphibians (such as its feeding apparatus, dermal bones of the skull, and anterior cervical vertebrae) that Fox and Naylor suggested it be classified in its own order, Allocaudata, family, Albanerpetontidae, and genus, Albanerpeton, all of which were new at the time.[7] Seven of the eight species are restricted to the Western Interior of North America, suggesting that the evolutionary history of the genus was centered there,[8] although the presence of a sole species in France,[6] A. inexpectatum, suggests a Tertiary dispersal of an unknown species from North America into Europe. Albanerpeton jaws and frontals are the most commonly recovered Albanerpeton bones found at dig sites, but these bones exhibit many characteristics that are taxonomically and phylogenetically informative for the genus and individual species within it.[6]

Evolutionary history

The oldest species of Albanerpeton as usually defined are known from the late Early Cretaceous of North America. During the Late Cretaceous, Albanerpeton was widespread in North America, as well as in Europe (and was present in Asia if remains from the Khodzhakul Formation in Uzbekistan are included). The youngest remains of the species in North America are known from the Paskapoo Formation in Canada, dating to the Paleocene.[1] The Cenozoic record of Albanerpeton is largely confined to Europe, spanning from the Oligocene to the final records of the group in the Early Pleistocene of Italy, around 2.13-2 million years ago.[1][2] Fossils are also known from the Oligocene of Anatolia in Asia.[9]

Ecology

Albanerpeton is suggested to have had a preference for moist environments.[1] Albanerpetontids are proposed to have been sit-and wait predators that fed on invertebrates via the use of a ballistic tongue similar to that used by chameleons and plethodontid salamanders.[5]

Description

Albanerpeton are distinct from

synapomorphies, both of which can be used to further diagnose less inclusive clades in the genus.[10] These less inclusive clades are the gracile-snouted clade and robust-snouted clade, made up of three and four species respectively though only three of the robust-snouted clade have been fully described. The gracile-snouted clade is defined by a triangular to slit-shaped suprapalatal pit. The robust-snouted clade is defined by a robust premaxillae, a short pars dorsalis that is sutured dorsally with the nasal, a short premaxillary lateral process on the maxilla, and an internasal process on frontals that are both narrow and similar to spines.[10] The origins of these sister, snout-based clades can both be traced back to the early Late Cretaceous, and therefore antedate the Campanian.[10] A. arthridion is interpreted as the most primitive species of Albanerpeton, being quite small. Its small size forms the basis for the hypothesis that reduced body size is derived, and was developed at least twice within the genus.[11]
Diagnostic characteristics of the genus itself include characteristics of the teeth and skull.

Dentition

Albanerpeton teeth are about one-third of the distance from the anterior end of the tooth row, and these are markedly larger than other nearby teeth. Additionally, the dorsal edge of the dental boundary is curved on its lingual side.[10]

Skull

In 2013, Maddin et al. created a computer-generated tomography of a partially preserved, three-dimensional A. pannonicum neurocranium which deposited during the

coossification of the parasphenoid, otic capsules, and occipital elements with no trace of fusion or sutural points of contact among these components. Additionally, the anterior three-quarters of the dorsal surface is open, but the furthest posterior portion, tectum synoticum, is fused. The ventral surface of Albanerpeton neurocrania are fully ossified, solid bone.[12] The neurocranium of Albanerpeton is in contact dorsally with paired parietals, forming the roof of the brain cavity while contacting laterally with the squamosal.[12] Overall, the robust construct of Albanerpeton's neurocranium is consistent with the theory that the genus was fossorial in nature, as the thickened and strengthened skull would have lent itself to burrowing.[8]
 

Albanerpeton have ossified

fenestra vestibuli present on both capsules. These fenestrae can be used to imply the presence of middle ear ossicles in Albanerpeton. Albanerpeton had well-developed semicircular canals with a modestly developed ventral auditory region as well.[12]

Classification

Current accepted species:

Genus Albanerpeton Estes & Hoffstetter 1976

  • Albanerpeton arthridion Fox & Naylor 1982 Early Cretaceous, United States
  • Albanerpeton ektopistikon Carrano et al. 2022 Early Cretaceous, North America
  • Clade "Gracile-snouted"
    • Albanerpeton gracilis Gardner 2000 Late Cretaceous, North America
    • Albanerpeton cifellii Gardner 1999 Late Cretaceous, United States
    • Albanerpeton galaktion Fox & Naylor 1982 Late Cretaceous, North America
  • Clade "Robust-snouted"
    • Albanerpeton nexuosus Estes 1981 Late Cretaceous, North America
    • Albanerpeton pannonicus Venczel & Gardner 2005 Latest Miocene-Early Pleistocene Hungary, Italy
    • Albanerpeton inexpectatum Estes & Hoffstetter 1976 Early Oligocene-Late Miocene, Europe

The genus Albanerpeton is part of the family Albanerpetontidae which is part of the order Allocaudata within superorder Batrachia and class Amphibia. Members of genus Albanerpeton are considered to be Lissamphibia who are distinct in character from frogs, salamanders, and caecilians. In 2018, a closely related species, named Shirepeton isajii, was discovered and described in the Kuwajima Formation of Japan. While it is closely related to members of Albanerpeton, it does not fall within the clade.

Densuş-Ciula Formation, Sânpetru Formation and Sard Formation of Romania and the Maastrichtian aged Tremp Formation of Spain, are probably only diagnostic to family level.[13]

Cladogram from Venczel and Gardner (2005):[14]

Albanerpetontidae

Anoualerpeton

Celtedens

Albanerpeton

A. arthridion

Gracile‑snouted clade

A. cifellii

A. galaktion

A. gracilis

Robust‑snouted clade

A. nexuosus

A. pannonicus

Paskapoo sp.

A. inexpectatum

In 2020 it was found that Albanerpeton is paraphyletic with respect to Shirerpeton and Yaksha, and it has been suggested that Albanerpeton be restricted to the Cenozoic species, with the Cretaceous species being given separate genera.[5]

Cladogram from Daza et al. (2020)

 Anoualerpeton

 

Celtedens

Uña taxon

    

Wesserpeton

    

Albanerpeton arthridion

    

Albanerpeton gracilis + Albanerpeton galaktion

    

Albanerpeton cifellii

    

Yaksha

    

Shirerpeton

    

Albanerpeton nexuosum

    

Albanerpeton pannonicum

Paskapoo sp

Albanerpeton inexpectatum

Finally, with the description of Albanerpeton ektopistikon by Carrano et al. (2022), based on the data matrix from the 2018 description of Shirepeton isajii, also recovered Albanerpeton as a paraphyletic genus, further separated than in Daza et al., (2020). Instead of restricting Albanerpeton, they provisionally suggested to include Shirerpeton and Wesserpeton into the genus, turning their type species into A. isajii and A. evansae, respectively, though they also suggested that the genus could be split into separate genera. Cladogram from Carrano et al. (2022):[1]

Celtedens

Cletedens ibericus

Celtedens megacephalus

Unnamed Purbeck Group specimen

 

Anoualerpeton unicum

Aonualerpeton priscum

Yaksha perettii

Alcobaça Formation specimen

Albanerpeton

Albanerpeton arthridion

Albanerpeton (Wesserpeton) evansae

Unassigned claw taxon

Albanerpeton ektopistikon

 'Khodzhakul Formation specimen   

'Gracile‑snouted' Clade

Albanerpeton gracilis

Albanerpeton galaktion

Albanerpeton cifellii

   

'Sânpetru Formation specimen'

 'Csehbánya Formation specimen'

Albanerpeton (Shirerpeton) isajii 

  

 Albanerpeton nexuosum    

Albanerpeton cf Albanerpeton nexuosum  

 

Albanerpeton pannonicum

Albanerpeton inexpectatum

 'Paskapoo specimen' 

References

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    S2CID 247335328
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  10. ^ a b c d Gardner, James (2000). "Albanerpetontid Amphibians from the Upper Cretaceous (Campanian and maastrichtian) of North America". Geodiversitas. 22:3: 349–388.
  11. ISSN 1475-4983
    .
  12. ^ .
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  14. .

Further reading

  • Delfino, M. and Sala, B. 2007. Late Pliocene Albanerpetontidae (Lissamphibia) from Italy. Journal of Vertebrate Paleontology 27(3):716–719
  • Fossil Salamanders of North America (Life of the Past) by J. Alan Holman