''Albanerpeton'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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 t ...

-like

albanerpetontid The Albanerpetontidae (also spelled Albanerpetidae and Albanerpetonidae) are an extinct family of small amphibians, native to the Northern Hemisphere during the Mesozoic and Cenozoic. The only members of the order Allocaudata, they are thought to ...

amphibian found in

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

and Asia first appearing in

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

-aged strata. There are eight described members of the genus, and one undiagnosed species from the

Paskapoo Formation The Paskapoo Formation is a stratigraphic unit of Middle to Late Paleocene age in the Western Canada Sedimentary Basin. The Paskapoo underlies much of southwestern Alberta, and takes the name from the Blindman River ( means 'He is blind' in Cr ...

, making it by far the most speciose genus in the family. 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 that is adapted to digging and which lives primarily (but not solely) underground. Examples of fossorial vertebrates are Mole (animal), moles, badgers, naked mole-rats, meerkats, armadillos, wombats, and mole salamand ...

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

Gelasian The Gelasian is an age in the international geologic timescale or a stage in chronostratigraphy, being the earliest or lowest subdivision of the Quaternary Period/System and Pleistocene Epoch/Series. It spans the time between 2.58 Ma (million y ...

) of northern

Italy Italy, officially the Italian Republic, is a country in Southern Europe, Southern and Western Europe, Western Europe. It consists of Italian Peninsula, a peninsula that extends into the Mediterranean Sea, with the Alps on its northern land b ...

, and possibly northern Spain, until around 2 million years ago. It likely became extinct when the region developed its present Mediterranean-type climate, having preferred one that was cold and humid. The

monophyly In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent comm ...

of ''Albanerpeton'' has recently been questioned, with some authors regarding the genus as

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

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 epoch (geology), 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 mea ...

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 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 t ...

, 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 ...

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 The Albanerpetontidae (also spelled Albanerpetidae and Albanerpetonidae) are an extinct family of small amphibians, native to the Northern Hemisphere during the Mesozoic and Cenozoic. The only members of the order Allocaudata, they are thought to ...

, 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.

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 The Khodzhakul Formation is a Cenomanian aged geologic formation in Uzbekistan. Dinosaur remains are among the fossils that have been recovered from the formation.Weishampel, et al., 2004, "Dinosaur distribution." pp.517-607 As well as those of ...

in Uzbekistan are included). The youngest remains of the species in North America are known from the

in Canada, dating to the

Paleocene The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...

. The Cenozoic record of ''Albanerpeton'' is largely confined to Europe, spanning from the

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

to the final records of the group in the

Early Pleistocene The Early Pleistocene is an unofficial epoch (geology), sub-epoch in the international geologic timescale in chronostratigraphy, representing the earliest division of the Pleistocene Epoch within the ongoing Quaternary Period. It is currently esti ...

of Italy, around 2.13-2 million years ago. Fossils are also known from the Oligocene of

Anatolia Anatolia (), also known as Asia Minor, is a peninsula in West Asia that makes up the majority of the land area of Turkey. It is the westernmost protrusion of Asia and is geographically bounded by the Mediterranean Sea to the south, the Aegean ...

in Asia.

Ecology

''Albanerpeton'' is suggested to have had a preference for moist environments. 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 Chameleons or chamaeleons (family Chamaeleonidae) are a distinctive and highly specialized clade of Old World lizards with 200 species described as of June 2015. The members of this family are best known for their distinct range of colours, be ...

and

plethodontid Plethodontidae, or lungless salamanders, are a family of salamanders. With over 500 species, lungless salamanders are by far the largest family of salamanders in terms of their diversity. Most species are native to the Western Hemisphere, from B ...

salamanders.

Description

Albanerpeton are distinct from

frog A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order (biology), order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough ski ...

s, and

caecilian Caecilians (; ) are a group of limbless, vermiform (worm-shaped) or serpentine (snake-shaped) amphibians with small or sometimes nonexistent eyes. They mostly live hidden in soil or in streambeds, and this cryptic lifestyle renders caecilians ...

s, forming their own family of

Lissamphibia The Lissamphibia (from Greek λισσός (lissós, "smooth") + ἀμφίβια (amphíbia), meaning "smooth amphibians") is a group of tetrapods that includes all modern amphibians. Lissamphibians consist of three living groups: the Salientia ( ...

, 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 mammals h ...

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 ...

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

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

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 The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...

. ''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 (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Hungary Hungary is a landlocked country in Central Europe. Spanning much of the Pannonian Basin, 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 and ...

. 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 Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in the ...

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 The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestra ...

. 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 The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly sepa ...

region and suspensorium. In Albanerpeton, the otic capsules themselves are moderately inflated with a large, rhomboid-shaped fenestra vestibuli present on both capsules. These

fenestra A fenestra (fenestration; : fenestrae or fenestrations) is any small opening or pore, commonly used as a term in the biology, biological sciences. It is the Latin word for "window", and is used in various fields to describe a pore in an anatomy, ...

e can be used to imply the presence of middle ear

ossicles The ossicles (also called auditory ossicles) are three irregular bones in the middle ear of humans and other mammals, and are among the smallest bones in the human body. Although the term "ossicle" literally means "tiny bone" (from Latin ''ossi ...

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 The Sânpetru Formation is an Maastrichtian, early Maastrichtian geologic Formation (geology), formation. Dinosaur remains are among the fossils that have been recovered from the formation.Weishampel, et al. (2004). "Dinosaur distribution." Pp. 5 ...

and Sard Formation of Romania and the Maastrichtian aged

Tremp Formation The Tremp Formation (, ), alternatively described as Tremp Group (), is a geological Formation (geology), formation in the comarca Pallars Jussà, Lleida Province, Lleida, Spain. The formation is restricted to the Tremp-Graus Basin, Tremp or T ...

of Spain, are probably only diagnostic to family level.

Cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

from Venczel and Gardner (2005): In 2020 it was found that ''Albanerpeton'' is

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 (, , ) in Mythology 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 Hindu, Jain and Bud ...

,'' 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 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):