Extant jawed vertebrates, or gnathostomes, fall into two major monophyletic groups, namely chondrichthyans (cartilaginous fishes) and osteichthyans (bony fishes and tetrapods). Fossil representatives of the osteichthyan crown group are known from the latest Silurian period, 418 million years (Myr) ago, to the present. By contrast, stem chondrichthyans and stem osteichthyans are still largely unknown. Two extinct Palaeozoic groups, the acanthodians and placoderms, may fall into these stem groups or the common stem group of gnathostomes, but their relationships and monophyletic status are both debated. Here we report unambiguous evidence for osteichthyan characters in jaw bones referred to the late Silurian (423-416-Myr-old) fishes Andreolepis hedei and Lophosteus superbus, long known from isolated bone fragments, scales and teeth, and whose affinities to, or within, osteichthyans have been debated. The bones are a characteristic osteichthyan maxillary and dentary, but the organization of the tooth-like denticles they bear differs from the large, conical teeth of crown-group osteichthyans, indicating that they can be assigned to the stem group. Andreolepis and Lophosteus are thus not only the oldest but also the most phylogenetically basal securely identified osteichthyans known so far.

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A diverse Late Permian assemblage of chondrichthyan and actinopterygian micro-and macroremains is presented from the central Iranian locality of Baghuk Mountain for the first time. The vertebrate remains were found in sediments containing mainly pelagic organisms such as nautiloids, ammonoids, and conodonts. Their habitat is interpreted as a deep shelf area with well-oxygenated bottom water conditions below the storm wave base. The chondrichthyans are represented by various dermal denticles, a fragment of a spine, and a low number of teeth from mostly durophagous hybodontiforms and eugeneodontiforms. A new eugeneodontid species is described as Bobbodus xerxesi sp. nov.; this genus was known only from the east coast of the former Panthalassic Ocean. The actinopterygian remains are represented by dermal bones, teeth, and scales. The bones are only fragmentarily preserved. The Baghuk Mountain vertebrate fauna shows closest similarities to remains known from the Russian Platform and from localities situated at the east coastal region of the Panthalassic Ocean (central United States).•

The record of Polyacrodus teeth from the Triassic of the Germanic Basin is summarized. The validity of the species Polyacrodus krafri Seilacher, 1943 and Polyacrodus keuperianus (Winkler, 1880) is discussed on the basis of new specimens, that allows to emend the diagnosis of P krafti.