2023 in paleoichthyology
This list of fossil fish research presented in 2023 is a list of new taxa of jawless vertebrates, placoderms, acanthodians, fossil cartilaginous fishes, bony fishes, and other fishes that were described during the year, as well as other significant discoveries and events related to paleoichthyology that occurred in 2023. Jawless vertebrates

Jawless vertebrate research
 A study on the anatomy and affinities of Lasanius is published by Reeves et al. (2023), who interpret this vertebrate as a stem-cyclostome. Dearden et al. (2023) describe the cranial anatomy of Eriptychius americanus, provide evidence of the presence of a symmetrical set of cartilages interpreted as the preorbital neurocranium, and report that the studied cartilages filled out the head and closely supported the dermal skeleton (in that they were closer to the cranial anatomy of osteostracans and galeaspids than cyclostomes), but were not fused into a single unit around the brain (more closely resembling the cranial anatomy of cyclostomes than osteostracans, galeaspids and jawed vertebrates in that aspect). Placoderms

Placoderm research
 Evidence from the study of the skull of Kolymaspis sibirica, interpreted as indicating that the sixth branchial arch was probably the one that was incorporated into the vertebrate shoulder girdle, is presented by Brazeau et al. (2023). Brazeau et al. (2023) describe a near-complete "acanthothoracid" upper jaw from the Devonian (Pragian) Yamaat Gol locality (Mongolia), and interpret this finding as indicating that the morphology and function of "acanthoracid" jaws resemble generalized "placoderm" conditions seen also in arthrodires and rhenanids. Redescription and a study on the affinities of Bothriolepis sinensis is published by Luo et al. (2023). Engelman (2023) attempts to determine body size of Dunkleosteus terrelli, recovering the body lengths of between 3.1 and 3.5 m for typical adults and ~4.1 m for the largest individuals; in a subsequent study the author reevaluates the methodology and length estimates used by Ferrón, Martinez-Perez & Botella (2017), and argues that length estimates for Dunkleosteus based on the mouth dimensions of extant sharks are not reliable, as arthrodires have proportionally larger mouths than sharks. Acanthodians

Acanthodian research
 Burrow & Desbiens (2023) describe dental elements of Doliodus latispinosus from the Devonian York River Formation (Quebec, Canada), finding no justification for assigning the studied isolated dental elements to a species distinct from D. latispinosus from the Atholville beds (New Brunswick, Canada). Cartilaginous fishes

Cartilaginous fish research
 Fossil material of members of the genera Pucapampella and Zamponiopteron is described from the Devonian (Eifelian) Chagrapi Formation by Zevallos-Valdivia et al. (2023), representing the first record of Paleozoic vertebrates from Peru reported to date. A study on the musculoskeletal anatomy of Iniopera is published by Dearden, Herrel & Pradel (2023), who interpret the anatomy of Iniopera as unsuited to durophagy, and consider it to be likely a high-performance suction-feeder. Fossil material of members of at least seven species belonging to the genus Ptychodus is described from the ?Cenomanian–Santonian of the Malyy Prolom area (Ryazan Oblast, Russia) by Amadori et al. (2023), who also report the northernmost occurrence of Ptychodus in Europe from the Cenomanian of Varavinsky ravine area (Moscow Oblast, Russia), and interpret the studied fossils as indicating that Late Cretaceous epicontinental seas of the Russian platform were important areas of diversification and spread of Ptychodus. Amadori et al. (2023) report the discovery of teeth of various species belonging to the genus Ptychodus from the Cenomanian and Turonian deposits of Ukraine, including teeth of cuspidate (P. altior) and un-cuspidate species (P. decurrens, P. latissimus, P. marginalis and P. polygyrus), and argue that the availability of diverse shelled invertebrates in epicontinental seas might have favored the diversification of Ptychodus. A study on the teeth of Megachasma applegatei is published by Krak & Shimada (2023), who find that the range of the morphometric variation of teeth of M. applegatei is larger than that of teeth of extant megamouth shark, with different tooth types corresponding to tooth types present in the smalltooth sand tiger. Shimada et al. (2023) describe tessellated calcified cartilage and placoid scale associated with a tooth set of Otodus megalodon from the Miocene strata in Japan, and interpret the morphology of the studied material as indicating that O. megalodon was generally a slow cruising shark. A study on the thermoregulation in Otodus megalodon is published by Griffiths et al. (2023), who argue that O. megalodon had an overall warmer body temperature compared with other coexisting shark species, and that its large body size coupled with high metabolic costs associated with having at least partial endothermy might have made it vulnerable to extinction. Collareta, Casati & Di Cencio (2023) describe new fossil material of Parotodus benedenii from the Valdelsa Basin (Italy), providing evidence of the survival of the species at least until the Late Pliocene, and interpret P. benedenii as a large-bodied carnivorous shark living in pelagic settings. Collareta et al. (2023) report the discovery of teeth of Alopias grandis from the Miocene deposits in southern Italy, possibly including the geologically youngest record of the species and extending its known geographic range. Villafaña et al. (2023) describe fossil material of the common thresher and the porbeagle from the Bahía Inglesa Formation (Caldera Basin, Chile), confirming the abundance of lamniform sharks in the Eastern Pacific of South America during the Neogene. A study on the anatomy and affinities of Protospinax annectans, based on data from both known and previously undescribed specimens from the Tithonian Altmühltal Formation (Germany), is published by Jambura et al. (2023). Ferrón (2023) argues that, although representatives of most squalomorph groups colonized deep waters independently during the Late Jurassic and Early Cretaceous, bioluminescence evolved only once among sharks in a bathydemersal ancestor. A fossil egg case containing a well-preserved batoid (possibly stem-myliobatiform) embryo, with a unique combination of characters indicating that the embryo represents a previously unknown batoid form, is described from the Cenomanian Sannine limestone of Hjoula (Lebanon) by Capasso & Yamaguchi (2023). Reinecke et al. (2023) study the anatomy and affinities of whiptail stingray teeth from the Chattian of northern Germany and the Burdigalian of southern France, transferring the species Dasyatis probsti to the genus Bathytoshia. Pollerspöck et al. (2023) describe an assemblage of deep-sea shark fossils from the Eocene (Ypresian) Lillebælt Clay Formation (Denmark), showing highest similarities with deep-sea shark faunas of France, Austria and northern Morocco in spite of the North Sea Basin having lost direct connections to the neighbouring marine areas in the Eocene. Kovalchuk et al. (2023) revise the taxonomic composition of the cartilaginous fish assemblage from the Eocene (Lutetian-Bartonian) Kyiv Formation (Ukraine), interpreting the studied taxa as inhabiting shallow, warm waters and confined to the continental shelf. Verma (2023) describes new fossil material of elasmobranchs from the Eocene (Bartonian) Harudi Formation (India), providing evidence of replacement of earlier Eocene assemblages of elasmobranchs from western India by an assemblage dominated by members of the genera Brachycarcharias, Striatolamia, Galeocerdo and Carcharhinus, which might have been linked to the Middle Eocene Climatic Optimum. An assemblage of shark and ray teeth, interpreted as indicative of a warm, shallow water community, is described from the Lower Miocene deposits of the Upper Marine Molasse near Ballendorf (Germany) by Höltke et al. (2023). A study on changes of diversity of European chondrichthyans during the Neogene is published by Villafaña et al. (2023). A study on the impact of the Cretaceous–Paleogene extinction event on elasmobranchs is published by Guinot & Condamine (2023), who find rays and durophagous species to be more affected by the extinction than sharks and nondurophagous species, and find taxa with large geographic ranges or restricted to high-latitude settings to show higher survival. Ray-finned fishes

Ray-finned fish research
 Figueroa et al. (2023) report brain and cranial nerve soft-tissue preservation in the type specimen of Coccocephalus wildi from the Carboniferous strata in the Mountain Fourfoot Mine (Pennine Lower Coal Measures; Lancashire, United Kingdom). Bakaev, Johanson & LeBlanc (2023) study the dental system of Kazanichthys viatkensis, reporting the presence of morphological similarities to the dental systems of extant sparids, and interpreting K. viatkensis as a generalist durophagous feeder. Revision of the fossil material of Permian ray-finned fishes from the Kazankovo-Markino Formation (Kemerovo Oblast, Russia) is published by Bakaev (2023), who considers Heterolepis Sergienko (1974) to be a junior synonym of Eurynotoides Berg (1940). Martill (2023) describes a bony scute of a sturgeon from the Maastrichtian marine phosphatites of central Morocco, representing the first record of an acipenseriform fish from Africa reported to date. New information on the morphology of the scales of members of the family Pseudobeaconiidae, based on new fossil material from the Triassic Santa Clara Abajo Formation (Argentina), is presented by Giordano, Benavente & Suárez (2023). Putative eugnathid amiiform Sinoeugnathus kueichowensis is reinterpreted as a small-sized member of Ionoscopiformes by Feng et al. (2023), who name a new family Subortichthyidae including the genera Subortichthys, Sinoeugnathus, Allolepidotus and Eoeugnathus. Sullivan, Jasinski & Williamson (2023) describe an exceptionally well-preserved articulated skull roof and braincase of Melvius chauliodous from the Upper Cretaceous Kirtland Formation (New Mexico, United States), revise the characters that defin the genus and its two recognized species, and study the phylogenetic affinities of Melvius. A study on the microstructure of teeth of Late Jurassic pachycormids and caturoids from the Owadów-Brzezinki site (Poland) is published by Weryński, Błażejowski & Kędzierski (2023), who report structural differences interpreted as suggestive of different adaptations for predation and possible niche partitioning between the studied taxa. Systematic revision of the Late Jurassic species of Caturidae is published by López-Arbarello & Ebert (2023). Cooper & Maxwell (2023) describe a specimen of Pachycormus macropterus from the Toarcian Posidonia Shale (Germany) preserved with an unusually large ammonite inside its gut, interpreted as ingested immediately prior to and directly responsible for the fish's death. A study on the bone histology of Araripichthys castilhoi, interpreted as corroborating its placement within basal Teleostei, is published by Mayrinck et al. (2023). Stinnesbeck et al. (2023) report the presence of two different body shape types of specimens of Tselfatia formosa from the Turonian platy limestone deposit of Vallecillo (Mexico), intepreted as evidence of sexual dimorphism, and interpret the anatomy of its fins as indicating that T. formosa lived in a deep water environment and that its lifestyle resembled that of extant fan fishes. Cooper & Norton (2023) describe fossil material of an indeterminate plethodid from the Maastrichtian deposits from the Plateau des Phosphates (Morocco), representing the youngest occurrence of a plethodid reported to date. Redescription and a study on the affinities of Sorbinichthys elusivo is published by Taverne & Capasso (2023). A study on the fossil record of acanthomorphs from the Maastrichtian–Paleocene strata is published by Friedman et al. (2023), who find that the majority of the principal acanthomorph groups appear in the fossil record before the end of the Paleocene. A study on the variety of the morphology of the first abdominal vertebral centrum in extant acanthomorphs is published by Murray & Brinkman (2023), who interpret their findings as indicating that the overall morphology of the first centrum is conservative within acanthomorph families, and that it is possible to assign many fossil acanthomorph centra to extant families, suborders or orders. Rust & Robinson (2023) redescribe Eothyrsites holosquamatus, and interpret this taxon as likely representing an ancestral form of gempylid. Ngoepe et al. (2023) reconstruct the history of arrival order and relative abundances of major fish groups from Lake Victoria, using data from the continuous fossil record from the preceding 17,000 years, and report that cichlids did not dominate the assemblage until several thousand years into its history, but they were the only major group that had the ecological versatility that allowed them to persist once the new deep and open-water habitats emerged. Evidence from (mostly lanternfish) otoliths from the Lindos Bay Formation (Rhodes, Greece), interpreted as indicative of an overall decline of the median size of lanternfishes in the eastern Mediterranean during MIS 19 interglacial, but also as indicative of different trends in size in individual mesopelagic species across the studied time interval, is presented by Agiadi et al. (2023). Lobe-finned fishes

Lobe-finned fish research
 Dupret et al. (2023) describe new fossil material of sarcopterygians from the Devonian (Givetian) Valentia Slate Formation (Republic of Ireland), including a tooth plate of a lungfish with a derived morphology otherwise only known from Late Devonian and later taxa, and a possible rhizodontid fossil material, which might indicate that a dispersal of rhizodontids from Gondwana into Euramerica happened as early as middle Givetian. General research
 Kuznetsov & Kryukova (2023) present new reconstructions of subcephalic musculature for Pucapampella, Eusthenopteron and Ichthyostega. Baucon et al. (2023) describe fish-feeding traces from the Lower Cretaceous (Hauterivian–Barremian) Palombini Shale Formation (Italy), interpreted as the earliest direct evidence of bottom-living vertebrates from the deep sea. Trif et al. (2023) describe a diverse fish assemblage from the Priabonian strata in the Leghia-Tabără area (Romania), including the first record of Physogaleus alabamensis from Europe and the first record of Striatolamia tchelkarnurensis outside the Turgai Strait region. References 

2023 in paleontology