The behaviour of fossil organisms can typically be inferred only indirectly, but rare fossil finds can provide surprising insights. Here, we report from the Eocene Messel Pit Fossil Site between Darmstadt and Frankfurt, Germany numerous pairs of the fossil carettochelyid turtle Allaeochelys crassesculpta that represent for the first time among fossil vertebrates couples that perished during copulation. Females of this taxon can be distinguished from males by their relatively shorter tails and development of plastral kinesis. The preservation of mating pairs has important taphonomic implications for the Messel Pit Fossil Site, as it is unlikely that the turtles would mate in poisonous surface waters. Instead, the turtles initiated copulation in habitable surface waters, but perished when their skin absorbed poisons while sinking into toxic layers. The mating pairs from Messel are therefore more consistent with a stratified, volcanic maar lake with inhabitable surface waters and a deadly abyss.

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The first fossils of the tholichthys larval stage of a chaetodontid from the lower Oligocene (Rupelian, Fish Shales; about 30.1 MYA) of Frauenweiler (Baden-Würt-temberg, S Germany) are described, along with two less well-preserved probable tholichthys from the lower Oligocene of Przemyśl (Outer Carpathians, SE Poland). The fossils are compared with tholichthys larvae of the extant genus of Chaetodontidae to which they are most similar, namely Chaetodon. The German specimens are identified as tholichthys larvae by the plate-like expansions of the supracleithrum and posttemporal that extend posteriorly well behind the head and by an expanded preopercle with a large posterior spine; these bones, and the frontals and supraoccipital, are distinctively rugose. The Polish specimen from IPM3 has similar features so it is safe to assume that it also is a chaetodontid tholichthys, whereas the specimen from IPM4A is so poorly preserved that it can only very tentatively be referred to the Chaetodontidae. The occurrence of tholichthys larvae prompts reconsideration of the paleoenvironmental situation at their respective fossil sites.

The Baid formation (Ad Darb locality, Tihamat Asir. SW Saudi Arabia) is Oligocene in age. The sediments have been deposited in one of a series of several alkaline continental lakes that once flanked the early Red Sea Rift. So far seven specimens of cichlid fish have been discovered there. They represent at least three different species. One species from endo-and exoskeletal characteristics can be assigned to the basal grade of cichlids, today represented mainly in Madagascar and India. The other two species seem to belong to two different clades within the African assemblage that today comprises more than 1000 species.

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The new genus and species of surgeon fish, Glarithurus friedmani (Acanthuridae), from the Lower Oligocene (Rupelian) of Kanton Glarus, Switzerland, differs from all other acanthurid fishes, fossil and extant, by having a single anal-fin basal pterygiophore situated in the first interhaemal space, versus two or more such pterygiophores in all other taxa. The new taxon is based upon a 29-mm SL acronurus stage specimen that probably had already settled onto a benthic substrate from its pelagic larval stage and begun its transformation into a juvenile. It has a scalpel-like dermal spine on the caudal peduncle and a crest on the hyomandibular, which are derived characters that establish it as a member of the clade of higher acanthurins. Within that clade, it is unique because of the great depth of its basipterygium at the subpelvic keel.