FOSSIL VERTEBRATES/Cenozoic Amphibians 523 records from Morocco and Sudan are both based on isolated bones Albanerpetontids The albanerpetontids are the extinct fourth group of lissamphibians; first recognized in 1976, subsequent discoveries have proved that they were widespread in the northern continents during the mid- to Late Mesozoic They were small, superficially salamander-like forms (Figure 9E), uniquely characterized by the two halves of the lower jaw articulating anteriorly by means of an asymmetrical ball-and-socket joint (Figure 9F) Even small fragments of such jaws are readily recognized in microvertebrate assemblages Articulated albanerpetontids are known from the konservat-lagerstaă tte at Las Hoyas, Spain, and this material is the key to understanding their morphology Albanerpetontids first appear with the full suite of characteristics in the Bathonian, and they appear to have been present throughout Eurasia and North America in the Upper Jurassic and Cretaceous, with a recent report from the Lower Cretaceous of Morocco representing the first Gondwanan record See Also Fossil Vertebrates: Palaeozoic Non-Amniote Tetrapods; Cenozoic Amphibians Lagerstaă tten Palaeozoic: End Permian Extinctions Further Reading Bystrow AP and Efremov IA (1940) Benthosuchus sushkini Efr A labyrinthodont from the Eotriassic of Sharjenga River Trudy Paleozoologicheskogo Instituta Akademii Nauk SSSR 10: 152 Holman JA (2003) Fossil frogs and toads of North America Bloomington and Minneapolis: Indiana Press Milner AR (1990) The radiations of temnospondyl amphib ians In: Taylor PD and Larwood GP (eds.) Systematics Association Special Volume 42 Major Evolutionary Ra diations, ch 15, pp 321 349 Oxford: Clarendon Press Milner AR (2000) Mesozoic and Tertiary Caudata and Albanerpetontidae In: Heatwole H and Carroll RL (eds.) Amphibian Biology, Volume 4, Palaeontology: The Evolutionary History of Amphibians, ch 18, pp 1412 1444 Chipping Norton, NSW: Surrey Beatty Rocˇek Z (2000) Mesozoic anurans In: Heatwole H and Carroll RL (eds.) Amphibian Biology, Volume 4, Palae ontology: The Evolutionary History of Amphibians, ch 14, pp 1295 1331 Chipping Norton, NSW: Surrey Beatty Sanchı´z B (1998) Salientia In: Wellnhofer P (ed.) Hand buch der Palaă oherpetologie part Munich: Pfeil Schoch RR and Milner AR (2000) Stereospondyli In: Wellnhofer P (ed.) Handbuch der Palaă oherpetologie part 3B Munich: Pfeil Warren AA (2000) Secondarily aquatic temnospondyls of the Upper Permian and Mesozoic In: Heatwole H and Carroll RL (eds.) Amphibian Biology, Volume 4, Palae ontology: The Evolutionary History of Amphibians, ch 8, pp 1122 1149 Chipping Norton, NSW: Surrey Beatty Cenozoic Amphibians A R Milner, Birkbeck College, London, UK ß 2005, Elsevier Ltd All Rights Reserved Introduction The fossil record suggests that archaic amphibian groups had entirely vanished by the Cenozoic, and that at least the majority of extant families were already established, many in the regions in which they still occur In this article, the Cenozoic fossil record of each of the modern groups and of the extinct albanerpetontids is reviewed Amphibians and the Cretaceous and Tertiary Boundary By the Late Cretaceous, the fossil record indicates that the only amphibians were the three modern lissamphibian groups (frogs, salamanders, and caecilians) and the enigmatic albanerpetontids Such evidence as exists suggests that the Cretaceous and Tertiary (K–T) boundary event (see Mesozoic: End Cretaceous Extinctions) had no effect on the diversity of amphibians In Montana, United States, and Alberta, Canada, there are freshwater faunas bracketing the Maastrichtian to Paleocene transition, and the frog and salamander assemblages are unchanged in diversity and taxonomic content through this time Evidence from the rest of the world is consistent with this, but at too poor a resolution to be convincing in its own right Cenozoic Assemblages Cenozoic amphibians are represented either as complete skeletons in assemblages in a few konservat-lagerstaătten (see Lagerstaă tten) (localities, or lagerstaătten, where prevailing conditions have produced highly conserved or diverse fossils) or, more commonly, as isolated elements in microvertebrate