Abstract
Abstract. Eryopid temnospondyls were large apex predators in Carboniferous and Permian stream and lake habitats. The eryopid life cycle is exemplified by Onchiodon labyrinthicus from Niederhäslich (Saxony, Germany), which is represented by numerous size classes from small larvae to heavily ossified adults. Morphometric and principal component analyses provide new insights into ontogenetic changes in O. labyrinthicus, and comparison with adults of other eryopids documents phylogenetic patterns in the occupation of morphospace. Compared with small specimens of Sclerocephalus spp., immature O. labyrinthicus occupies a neighboring but much larger space, corresponding to a broader range of variation. Adults of Actinodon frossardi map with some juveniles of O. labyrinthicus, whereas other juveniles of the latter lie close to adults of O. thuringiensis, Glaukerpeton avinoffi and Osteophorus roemeri. Morphospace occupation of adult eryopids is partly consistent with cladistic tree topology, which gives the following branching pattern: Actinodon frossardi forms the basalmost eryopid, followed by Osteophorus roemeri, Glaukerpeton avinoffi and the genus Onchiodon (O. labyrinthicus + O. thuringiensis); then Clamorosaurus nocturnus; and finally the monophyletic genus Eryops. The presumably juvenile skull of Eryops anatinus falls well outside the domains of both adult eryopids and immature O. labyrinthicus, showing a unique combination of juvenile and adult features. Instead, Onchiodon langenhani and the Ruprechtice specimens referred to O. labyrinthicus map within the domain of immature O. labyrinthicus. Raised levels of variation in O. labyrinthicus coincide with evidence of a stressed habitat, in which limiting factors were fluctuating salinity, absence of fishes, enhanced competition and seasonal algal blooms. The documented broad variation was possibly caused by developmental plasticity responding to fluctuations in lake hydrology and nutrients in this small, short-lived water body.
Highlights
In extant amphibians, metamorphosis is a drastic transformation in morphology that coincides with a change from an aquatic to a terrestrial existence
The eryopid life cycle is exemplified by Onchiodon labyrinthicus from Niederhäslich (Saxony, Germany), which is represented by numerous size classes from small larvae to heavily ossified adults
Metamorphosis is a drastic transformation in morphology that coincides with a change from an aquatic to a terrestrial existence
Summary
Metamorphosis is a drastic transformation in morphology that coincides with a change from an aquatic to a terrestrial existence. In more basal taxa, such as eryopiform temnospondyls, aquatic gill-bearing larvae transformed into terrestrial morphs (Witzmann, 2004, 2005), but this change was slow and gradual, with much less specialized larvae transforming slowly into adults (Boy, 1974; Schoch, 2009) Among the latter group, a more enigmatic clade is the eryopids – large apex predators of the late Paleozoic that were preserved in stream and lake deposits and that have often been presumed to have inhabited dry land. The present study seeks to integrate the available data (Appendix B) on life cycles in eryopids with patterns of phylogeny This necessarily starts with the ontogeny of O. labyrinthicus, the ontogenetically best studied and most completely preserved taxon of the clade (Boy, 1990). The following objectives are envisioned in the present study: (1) a review of the evidence on morphological changes in O. labyrinthicus with emphasis on newly identified features in the skull, (2) a morphometric analysis of variation and ontogeny in O. labyrinthicus as compared with other eryopiforms, (3) a cladistic analysis of all reasonably preserved eryopids, and (4) an integrated analysis of the evolution of the life cycle in eryopids
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