''Albanerpeton'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

salamander Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten ...

-like

lissamphibian The Lissamphibia is a group of tetrapods that includes all modern amphibians. Lissamphibians consist of three living groups: the Salientia (frogs, toads, and their extinct relatives), the Caudata (salamanders, newts, and their extinct relatives) ...

found in

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

and

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

, first appearing in

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

-aged strata. There are eight described members of the genus, and one undiagnosed species from the Paskapoo Formation, with the most recent, ''A. ektopistikon'' being described by Carrano ''et al.''in 2022. Members of the genus had a robust head and neck which likely allowed them to actively burrow, characteristic of

fossorial A fossorial () animal is one adapted to digging which lives primarily, but not solely, underground. Some examples are badgers, naked mole-rats, clams, meerkats, and mole salamanders, as well as many beetles, wasps, and bees. Prehistoric eviden ...

species, and they lived in a wide range of environments. This genus of amphibian was the last of its order, surviving until the late

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58southern Europe Southern Europe is the southern regions of Europe, region of Europe. It is also known as Mediterranean Europe, as its geography is essentially marked by the Mediterranean Sea. Definitions of Southern Europe include some or all of these countrie ...

, and into the Early Pleistocene ( Gelasian) of northern

Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical re ...

. It likely became extinct when the region developed its present Mediterranean-type climate, having preferred one that was cold and humid. The

monophyly In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...

of ''Albanerpeton'' has recently been questioned

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

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

fissure fills near La Grive-Saint-Alban in southeastern France was found. When the type species was originally described, it was considered to be a salamander, despite possessing no known features that were otherwise restricted to Urodela, as its only salamander-like features were held in common with small, limbed, and non-

saltatorial This glossary of entomology describes terms used in the formal study of insect species by entomologists. A–C A synthetic chlorinated hydrocarbon insecticide, toxic to vertebrates. Though i ...

amphibians in general. ''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. 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, although the presence of a sole species in France, ''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.

Geology and palaeoenvironment

The description of ''A''. ''arthridion'' by Gardner in 1999 established a minimum age of latest

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...

for Albanerpetontidae's establishment in North America. A later paper by Gardner in the same year, in which he described ''A. cifelli'', helped fill missing information in the genus’ record during the Cretaceous period. The finding and description of ''A. pannonicus'' in 2005 extended the genus’ temporal range from the middle Miocene to the early Pliocene. In 2018, Villa et al. investigated fossil herpetofauna and the palaeoenvironment in Northern Italy's town of

Rivoli Veronese Rivoli Veronese is a little town (''comune'') in the Province of Verona, Veneto, Italy, located on the hills overlooking the right bank of the river Adige, northwest of Verona. History Rivoli Veronese is celebrated as the scene of the Battle of ...

. The investigation supported the hypothesis that ''Albanerpeton'' favored a moist environment, and confirmed the former presence of a humid, forested landscape on Po Plain's northern side in the Gelasian, supporting the genus’ preference for humid environmental conditions, and also further extended the genus’ temporal range to the Gelasian period. The discovery and description of a new Albanerpetontidae species, who is closely related to genus ''Albanerpeton'', from the Kuwajima Formation in Japan, ''Shirepeton isajii'', further extends the group into Asia, though the genus ''Albanerpeton'' has still only been found in North America and Europe.

Description

Albanerpeton are distinct from

frog A frog is any member of a diverse and largely Carnivore, carnivorous group of short-bodied, tailless amphibians composing the order (biology), order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-f ...

s, and caecilians, forming their own family of

Lissamphibia The Lissamphibia is a group of tetrapods that includes all modern amphibians. Lissamphibians consist of three living groups: the Salientia (frogs, toads, and their extinct relatives), the Caudata (salamanders, newts, and their extinct relatives), ...

, Albanerpetontidae. Membership of species in the family is determined by diagnostic character states of the frontals and

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...

synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...

, both of which can be used to further diagnose less inclusive

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

s in the genus. 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. The origins of these sister, snout-based clades can both be traced back to the early Late Cretaceous, and therefore antedate the Campanian. ''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. 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 Lingual may refer to: * Tongue, a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication * Lingual, in palaeontology, the side of the teeth that faces the tongue * Lingual artery arises from the e ...

side.

Skull

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

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Hungary Hungary ( hu, Magyarország ) is a landlocked country in Central Europe. Spanning of the Carpathian Basin, it is bordered by Slovakia to the north, Ukraine to the northeast, Romania to the east and southeast, Serbia to the south, Croatia a ...

. The structure of this specimen is in line with what is known of older ''Albanerpeton'' neurocrania, and therefore a good reference for what the neurocranium of the whole genus is like. Features of the reconstructed skull consist of a robust, box-like unit composed of coossification of the

parasphenoid The parasphenoid is a bone which can be found in the cranium of many vertebrates. It is an unpaired dermal bone which lies at the midline of the roof of the mouth. In many reptiles (including birds), it fuses to the endochondral (cartilage-derived) ...

, 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. The neurocranium of ''Albanerpeton'' is in contact dorsally with paired parietals, forming the roof of the brain cavity while contacting laterally with the squamosal. Overall, the robust construct of ''Albanerpeton's'' neurocranium is consistent with the theory that the genus was

in nature, as the thickened and strengthened skull would have lent itself to burrowing. ''Albanerpeton'' have ossified antotic pillars which sit in front of the otic capsules. Additionally, there are a pair of small, robust bony pedestals that are located ventrolaterally in front of the otic capsules, which likely served to brace the neurocranium against the palatal region and suspensorium. In Albanerpeton, the otic capsules themselves are moderately inflated with large, rhomboid-shaped fenestra vestibulli present on both capsules. These fenestra can be used to imply the presence of middle ear

ossicles The ossicles (also called auditory ossicles) are three bones in either middle ear that are among the smallest bones in the human body. They serve to transmit sounds from the air to the fluid-filled labyrinth (cochlea). The absence of the auditory ...

in ''Albanerpeton''. ''Albanerpeton'' had well-developed semicircular canals with a modestly developed ventral auditory region as well.

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. Many remains attributed to ''Albanerpeton'' from the Late Cretaceous of Europe, such as those from the Maastrichtian aged Densuş-Ciula Formation, Sânpetru Formation and

Sard Formation is a Japanese tuning company and racing team from Toyota, Aichi, mainly competing in the Super GT series and specialising in Toyota tuning parts. History The company was formed in 1972 as Sigma Automotive Co., Ltd by Shin Kato to develop and ...

of Romania and the Maastrichtian aged Tremp Formation of Spain, are probably only diagnostic to family level. Cladogram from Venczel and Gardner (2005): In 2020 it was found that ''Albanerpeton'' is

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

with respect to ''

Shirerpeton ''Shirerpeton'' is an extinct genus of albanerpetontid amphibian from the Early Cretaceous Kuwajima Formation, which is located in Japan.Fujita, M. (2003). "Geological age and correlation of the vertebrate-bearing horizons in the Tetori Group ...

'' and ''

Yaksha The yakshas ( sa, यक्ष ; pi, yakkha, i=yes) are a broad class of nature-spirits, usually benevolent, but sometimes mischievous or capricious, connected with water, fertility, trees, the forest, treasure and wilderness. They appear in ...

,'' and it has been suggested that ''Albanerpeton'' be restricted to the Cenozoic species, with the Cretaceous species being given separate genera. Cladogram from Daza et al. (2020) 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 paraphiletic genus'','' further separated than in Daza ''et al.,'' (2020). Instead of restricting ''Albanerpeton,'' they suggested to include ''Shirerpeton'' and ''Wesserpeton'' into the genus, turning their type species into ''A. isajii'' and ''A. evansae'', respectively. Cladogram from Carrano ''et al.'' (2022):