Isolated teeth belonging to the genus Agassiz, 1834 (Chondrichthyes; Elasmobranchii) from the Upper Cretaceous of the Ryazan and Moscow Oblast regions (European Russia) are described and discussed in detail herein. The taxonomic composition of the assemblage from the Ryazan region is very diverse including the first records of the cuspidate species . and . , which thus is largely consistent with those from other contemporaneous European localities. ubiquitously inhabited epicontinental seas of Europe during most of the Cretaceous with the most diverse assemblages coming from southern England, northern Italy, Belgium, and European Russia. Additionally, the material documented here from the Cenomanian of Varavinsky ravine area (Moscow Oblast) represents the northernmost occurrence of hitherto reported from Europe. It is evident that the Late Cretaceous shallow seas of the Russian platform represented a crucial pathway for the dispersal of from the European peri-Tethys to the eastern margins of the Neo-Tethyan Ocean. The Albian-Campanian records of from Europe indicate that its dominance in the peri-Tethys persisted for most of its evolutionary history. A local temperature drop across most of the European shallow seas probably contributed to the narrowing of its geographic range in the peri-Tethyan seas towards the end of the Mesozoic Era. The fossil remains of documented herein are accordingly of utmost importance for better understanding the taxonomic composition of Russian fossil ichthyofaunas and also inform about the dispersal of towards western and eastern peri-Tethyan seas during the Late Cretaceous.

A new extinct sclerorhynchoid sawfish, sp. nov., is presented here based on abundant isolated teeth and some dermal denticles, which were recovered from the Mata Amarilla Formation, belonging to the lower Upper Cretaceous of the Santa Cruz Province in the Austral Basin of Patagonia, Argentina. This new species is the first occurrence in the southern hemisphere, which so far only has been reported from northern hemisphere deposits (Europe, North Africa, and North America). The presence of sp. nov. in these southern high-latitude deposits of Patagonia, Argentina, extends the geographic range of considerably southwards. This distribution pattern in the "middle" Cretaceous seems to correlate with the South Atlantic opening at the end of the Albian. The presence of lateral cephalic dermal denticles and the simultaneous absence of rostral denticles in the abundant fossil material support the view that did not develop such rostral structures. A reinvestigation of all known species assigned to reveals that is a junior synonym of belongs to belongs to , and represents an unidentifiable species (? sp.). The stratigraphic distribution demonstrates that might have originated in the Albian in south-western Europe and subsequently dispersed to obtain its widest distribution during the Cenomanian. In the Coniacian, a steep diversity decline is recognizable with a subsequent distribution shift from Europe to North America.

A new genus and species of pycnodontiform fishes, , from marginal marine, marine-brackish lower Toarcian ( ammonite subzone) clay deposits of Grimmen in northeastern Germany is described. The single specimen represents a diagnostic left prearticular dentition characterized by unique tooth arrangement and ornamentation patterns. , gen. et sp. nov., is the second unambiguously identified pycnodontiform species from the Early Jurassic, in addition to from the early Lower Jurassic of western Europe. We also report an indeterminate pycnodontiform tooth crown from the upper Pliensbachian ( ammonite subzone) of the same site. The material expands the Early Jurassic range of pycnodontiforms significantly northwards and confirms their presence before and immediately following the onset of the Toarcian Oceanic Anoxic Event (T-OAE) in the marginal marine ecosystems south of the Fennoscandian Shield. Moreover, the new records indicate that the Early Jurassic diversity of pycnodontiform fishes was greater than previously assumed and probably equaled that of the Late Triassic. Therefore, it is hypothesized that the Triassic-Jurassic mass extinction event did not affect pycnodontiform fishes significantly. Micro-computed tomography was used to study the internal anatomy of the prearticular of , gen. et sp. nov. Our results show that no replacement teeth were formed within the tooth-bearing bone but rather were added posteriorly to functional teeth. http://zoobank.org/urn:lsid:zoobank.org:pub:A56BDE9C-40C4-4CFA-9C2E-F5FA35A66F2 Citation for this article: Stumpf, S., J. Ansorge, C. Pfaff, and J. Kriwet. 2017. Early Jurassic diversification of pycnodontiform fishes (Actinopterygii, Neopterygii) after the end-Triassic extinction event: Evidence from a new genus and species, . Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1344679.

The Eocene La Meseta Formation on Seymour Island, Antarctic Peninsula, is known for its remarkable wealth of fossil remains of chondrichthyans and teleosts. Chondrichthyans seemingly were dominant elements in the Antarctic Paleogene fish fauna, but decreased in abundance from middle to late Eocene, during which time remains of bony fishes increase. This decline of chondrichthyans at the end of the Eocene generally is related to sudden cooling of seawater, reduction in shelf area, and increasing shelf depth due to the onset of the Antarctic thermal isolation. The last chondrichthyan records known so far include a chimeroid tooth plate from TELM 6 (Lutetian) and a single pristiophorid rostral spine from TELM 7 (Priabonian). Here, we present new chondrichthyan records of , , , , , , and from the upper parts of TELM 7 (Priabonian), including the first record of from Antarctica. This assemblage suggests that chondrichthyans persisted much longer in Antarctic waters despite rather cool sea surface temperatures of approximately 5°C. The final disappearance of chondrichthyans at the Eocene-Oligocene boundary concurs with abrupt ice sheet formation in Antarctica. Diversity patterns of chondrichthyans throughout the La Meseta Formation appear to be related to climatic conditions rather than plate tectonics.

Seymour Island, Antarctic Peninsula, is known for its wealth of fossil remains. This island provides one of the richest fossiliferous Paleogene sequences in the world. Chondrichthyans seemingly dominate this Eocene marine fauna and offer a rare insight into high-latitude faunas during the Palaeogene. So far, only a few isolated teeth of carcharhinid sharks have been reported from Seymour Island. Bulk sampling in the well-exposed La Meseta and Submeseta formations yielded new and abundant chondrichthyan material, including numerous teeth of carcharhinid and triakid sharks. Here, we present a reevaluation of the previously described carcharhinid remains and a description of new taxa: , gen. et sp. nov., , gen. et sp. nov., , sp. nov., and , sp. nov. The carcharhiniforms sp. and sp. are reported based on rare material, whereas teeth previously assigned to represent a nomen dubium.

The presence of eagle rays of the genus in the Neogene of the Temperate Pacific coast of South America (TPSA) still is ambiguous, although the fossil record of elasmobranch fishes (sharks, rays, and skates) from this area is quite good. Here, we present the first unmistakable fossil remains of from the Neogene of the TPSA. The material comprises 13 dental plates from one site in Peru and six localities in Chile ranging in age from Miocene to Pliocene and was compared with dental plates of extant species. Our study reveals that the number of tooth rows and the shape of lateral teeth in extant species are seemingly very variable and need to be established before fossil specimens can be confidently identified. Consequently, we do not assign the fossil specimens from the Neogene of the TPSA to any species but leave them as . Moreover, we recognized that only the shape of medial teeth provides reliable diagnostic characters in our material, whereas the shape and number of lateral teeth are highly variable, similar to the condition seen in extant species.

The Upper Cretaceous (Cenomanian) limestone quarry of Haqel, Lebanon, is home to one of the largest diversities of fossil actinopterygians in the Mesozoic, particularly of pycnodontiform fishes. Here, we describe a pycnodontiform fish, , gen. et sp. nov., from this locality based on four specimens. It is considered a member of the derived family Pycnodontidae due to the presence of a postparietal process. This taxon is distinct from other pycnodontids due to its diamond-shaped body, whip-like dorsal fin, postcloacal scales with forward-pointing spines, and acute anterior profile with a concave slope, giving it a 'hunchback' appearance. The prognathous snout armed with molariform teeth suggests that this pycnodont preyed on a variety of shelled animals from crevices. The smallest specimen is distinct in that it has a larger orbit size, no spines on the contour scales, poorly ossified skull roof bones, a notochord partially covered by arcocentra, and lacks whip-like filament on the dorsal fin, which suggest that it is a juvenile/subadult. The differences between the juvenile/subadult and other larger specimens suggest a change in ecological niche occupation during ontogeny, going from a generalized forager that lived in complex, reef habitats to moving into deeper waters to feed from crevices on the reef edge. These findings provide a more complete picture of the possible life history strategies that pycnodontiforms may have used in order to exploit different resources throughout their lives.