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a b s t r a c tThe cold adapted larger mammal faunas of Pleistocene Eurasia (the so-called Mammuthus-Coelodonta faunas) were mainly composed of autochthonous Palaearctic elements. Whereas the history of the immigration and evolution of European woolly mammoths has been exhaustively studied, comparable investigations for woolly rhinoceroses are lacking. Referring to the remains of European and Asian Coelodonta in general and the first skull to be found of a European woolly rhinoceros of early Middle Pleistocene age (from Bad Frankenhausen, Germany) in particular, the occurrence, dispersal, morphological evolution and ecological adaptation of early Coelodonta are reviewed. Coelodonta originated around 2.5 Myr BP north of the Himalayan-Tibetan uplift. The genus was restricted in its range to different types of steppe landscapes of continental Asia for more than two million years and it wasn't until MIS 12, when extended phases of low temperature and aridity prevailed in western Eurasia that woolly rhinoceroses comparable to Coelodonta tologoijensis spread westward towards Central Europe for the first time. Coelodonta entered Central and, in several cases, Western Europe during all of the subsequent Middle to Late Pleistocene cold stages. Morphological evolution, in particular, the elongation and narrowing of the head and successively its lower and more inclined posture, the shift of the orbits towards the rear of the skull, and changes in the position and morphology of the tooth row concurrently indicate progressive adaptations to an efficient grazer. During the course of their Plio-/ Pleistocene evolution, Coelodonta rhinoceroses changed strikingly from cursorial mixed feeders of central Asian origin to graviportal, highly specialised grazers, inhabiting huge belts of tundra-steppe-like environments during dry and cool to cold periods, and thus becoming the only rhinocerotid to join the Eurasian mammoth faunas. The Bad Frankenhausen Coelodonta record dates the initial formation of a pan-Eurasian Mammuthus-Coelodonta faunal complex to about 460 kyr BP.

Asteracanthus was one of the most common Mesozoic hybodontiform chondrichthyans, given that remains traditionally referred to this genus have been reported almost worldwide from Middle Triassic to Late Cretaceous strata so far. Asteracanthus was erected by Louis Agassiz for Late Jurassic fin spines with stellate tubercles. Later, Arthur Smith Woodward synonymized Strophodus, originally introduced by Agassiz for distinctive crushing teeth of Triassic-Cretaceous age, with Asteracanthus based on associated teeth and spines from the English Middle Jurassic. This taxonomic scheme has been accepted for more than 130 years until now, although articulated material has never been found. Here, we present a unique hybodontiform skeleton from the German Late Jurassic, displaying a striking combination of characters: tuberculate dorsal fin spines reminiscent of Asteracanthus, and multicuspid teeth that markedly differ from the crushing teeth previously referred to this genus. Using qualitative and quantitative approaches, we compared its fin spines with those that were found in association with Agassiz's Strophodus teeth, providing evidence that Asteracanthus and Strophodus in fact represent two valid genera distinct from all other hybodontiforms. Morphological features that distinguish fin spines of Strophodus from those of all other hybodontiforms include a straight anterior border and distally distributed posterior denticles. These observations led us to present an emended diagnosis for Asteracanthus. Dentally, Asteracanthus shows strong resemblance to Hybodus, but it otherwise lacks a palatobasal process on the palatoquadrate. Therefore, and in the absence of any reliable phylogenetic framework, we recommend treating Asteracanthus as incertae familiae until hybodontiform interrelationships are resolved.

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