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Albanerpetontids are an extinct clade of salamander-like lissamphibians characterised by features such as fused frontals and sculptured skull roof bones. Here we provide a histological analysis of the fused and sculptured frontals in two Late Cretaceous species of the type genus Albanerpeton sensu lato that differ in body size: moderate-sized 'Al.' gracile and larger-sized 'Al.' nexuosum. Despite general similarities in microanatomy/histology (no sutural trace remains between left and right frontals; sculpture formed by appositional growth of bone; predominance of parallel-fibred bone; and lack of growth marks, secondary osteons, and Sharpey's fibres) and the presence of sub-ventrolateral crest canals (possible albanerpetontid synapomorphy), 'Al.' nexuosum differs from 'Al.' gracile in exhibiting: a distinct three-layered diploë structure; bone remodelling; a higher degree of vascularisation; and more numerous osteocytic lacunae. We suggest that (1) histological differences between 'Al.' gracile and 'Al.' nexuosum are related to differences in absolute body sizes and relative development of sculpture and robustness of frontals and (2) the sub-ventrolateral crest canals in albanerpetontids are homologous to the canalis arteriae orbitonasalis in modern anurans. Two features (internal vascularisation and lack of Sharpey's fibres) support a recent suggestion that albanerpetontids may have relied entirely on cutaneous respiration. [ABSTRACT FROM AUTHOR]

Based on cranial and jaw elements, the presence of Albanerpeton pannonicum species (Allocaudata: Albanerpetontidae) was noticed from the late Pliocene Csarnóta 3 locality (Villány Hills). Since it is considered a poor fossil site, it had not been sufficiently studied. These fossils represent the geologically youngest record of the species from Hungary. Though, the Csarnóta 3 albanerpetontid assemblage is small the bones are well preserved, and all are informative on species or at least on genus level. The red coloured bone-bearing deposits and the preservation quality of bones are very similar to the uppermost strata (4–1) of the Csarnóta 2 palaeovertebrate locality. The study of small mammal fauna also suggests this correlation, as well as explains the age of the site. The studied vertebrate fauna forms a transition between the woodland and steppe wildlife. [ABSTRACT FROM AUTHOR]

The Albanerpetontidae are salamander-like, Middle Jurassic to Neogene lissamphibians from Laurasia and North Africa. Extensive series of albanerpetontid bones recently identified in collections from the Csarnóta 2 locality, south-central Hungary, extend the temporal range of the clade forward about seven million years from the middle Miocene to the early Pliocene. The Hungarian material is diagnostic for the Euramerican type genus Albanerpeton and pertains to a new species, A. pannonicus sp. nov., which differs from the seven previously reported congeners (Early Cretaceous–Miocene) in a distinctive combination of primitive and derived character states of the jaws and frontals, including a unique ventromedian keel on the azygous frontals. Some of the Hungarian specimens are articulated sets of skull bones, including ones containing the first three-dimensional examples of a nasal and jugals known for albanerpetontids, that help clarify some details of cranial osteology in these amphibians. Cladistic analysis nests A. pannonicus within the robust-snouted clade, as the sister taxon to an unnamed late Palaeocene species from Canada and A. inexpectatum from early–middle Miocene deposits in France, Austria and Germany. This phylogeny and recent reports of diagnostic Albanerpeton material from the Campanian of France and Maastrichtian of Romania suggest the evolutionary history of Albanerpeton was more complex than previously hypothesized, with Europe having played a larger role. The 25 fossiliferous layers at Csarnóta 2 record a shift from forest to grassland palaeoenvironments. Fossils of A. pannonicus are present in all layers, implying that this species was not adversely affected by the change in palaeoenvironments. [ABSTRACT FROM AUTHOR]