Chien-Hsiang Lin

Otolith paleontology traditionally relies on descriptive alpha taxonomy and standard ecological inference, leaving some aspects of long-term community restructuring insufficiently explored. Here we apply a quantitative community framework integrating formal beta diversity partitioning, which separates species turnover from nestedness, and multivariate dispersion analyses to evaluate Neogene–Quaternary teleost dynamics in the western Pacific. Based on 4,893 newly collected otoliths along the Dahan River section in northern Taiwan, the dataset completes an 8-million-year sequence extending from the Late Miocene into the Quaternary. Multivariate analyses resolve three distinct, epoch-defined assemblages: Miocene, Pliocene, and Pleistocene. Moreover, otolith-based community restructuring across temporal transitions was driven by taxonomic turnover that suggests gradual faunal replacement rather than simple diversity loss or nestedness-driven assemblage contraction. At the regional scale, we compiled 5,083 sciaenid otolith occurrences from the western Pacific, revealing a transition from Late Miocene endemic shelf taxa to Plio–Pleistocene assemblages increasingly dominated by extant lineages. Finally, this sciaenid otolith record exposes discrepancies with molecular-clock hypotheses that infer older divergence times for several modern lineages whose fossil appearances currently date to the Plio–Pleistocene. Our study demonstrates how fossil otoliths can be used to link local paleoecological signals with regional community turnover, providing empirical constraints for molecular phylogenies and contributing to a better-resolved view of teleost evolution in the western Pacific.

Adaptations to diverse substrate environments and tiering behaviours are thought to have contributed to the evolutionary success of echinoids. However, the macroevolution of respiratory structures remains poorly understood because of the fragmentary fossil record. Here, we investigate the evolution of petaloid respiratory structures in Brissopsis , one of the most diverse and specialized genera of deep‐infaunal heart urchins. We describe new fossil specimens of Brissopsis luzonica from Taiwan and the Philippines, dating from the Early Pliocene to the Early Pleistocene, an interval during which fossils of the genus are globally rare. We compiled fossil and extant records of Brissopsis and analysed petal morphology using linear measurements and outline‐based geometric morphometrics. Morphospace analysis shows that petal morphology remained broadly stable through time, with only a slight expansion of morphospace occupation since the Eocene–Oligocene. Petal outline is strongly associated with relative petal size but shows little relationship with body size or pore pair number. Species with convergent posterior petals tend to have relatively smaller petals than divergent forms, suggesting alternative respiratory strategies potentially associated with different environmental conditions and tiering behaviours. Together, these results indicate that much of the petal morphological diversity observed in extant Brissopsis was established early in the evolutionary history of the genus and subsequently maintained throughout the Cenozoic, providing new insights into the evolution of respiratory structures and adaptation in infaunal echinoids.

Otolith paleontology traditionally relies on descriptive alpha taxonomy and standard ecological inference, leaving some aspects of long-term community restructuring insufficiently explored. Here we apply a quantitative community framework integrating formal beta diversity partitioning, which separates species turnover from nestedness, and multivariate dispersion analyses to evaluate Neogene–Quaternary teleost dynamics in the western Pacific. Based on 4,893 newly collected otoliths along the Dahan River section in northern Taiwan, our dataset completes an 8-million-year sequence extending from the Late Miocene into the Quaternary. Multivariate analyses resolve three distinct, epoch-defined assemblages: Miocene, Pliocene, and Pleistocene. Moreover, the otolith-based community restructuring across temporal transitions was driven by taxonomic turnover that suggests gradual faunal replacement rather than simple diversity loss or nestedness-driven assemblage contraction. Scaling up to a regional framework, we compiled 5,083 sciaenid otolith occurrences from the western Pacific, revealing a transition from Late Miocene endemic shelf taxa to Plio–Pleistocene assemblages increasingly dominated by extant lineages. Finally, this sciaenid otolith record exposes discrepancies with molecular-clock hypotheses that infer older divergence times for several modern lineages whose fossil appearances are currently Plio–Pleistocene. Our study demonstrates how fossil otoliths can be used to link local paleoecological signals with regional community turnover, providing empirical constraints for molecular phylogenies and contributing to a better-resolved view of teleost evolution in the western Pacific.

Teleost fishes have evolved taxon‐specific otoliths that vary greatly in size and shape and are primarily involved in hearing and balance. This study identifies the main drivers of otolith shape disparity in Sciaenidae, a clade of sound‐producing bony fishes, using three‐dimensional geometric morphometrics (3DGM). We quantified variation in overall sagittal shape and sulcus configuration, performed cluster analysis, inferred 3D shape‐based trees, assessed phylogenetic signal using COI‐based molecular trees, and tested associations with ecological and biological factors. Overall sagittal shape formed nine morphogroups, mainly reflecting variation in longitudinal size and outer‐face protuberances, features that are often missed in 2D analyses. Shape‐based trees did not closely match COI‐based tree. The entire sulcus shape formed four morphogroups based on ostium curvature and cauda elongation. Phylogenetic signal was low but significant for overall sagittal shape (λ = 0.0000026, P = 0.0061), but not significant for the entire sulcus (λ = 0.0000015, P = 0.328), suggesting that overall sagittal shape is likely more evolutionarily conserved. A weak but significant association between overall sagittal shape and swim bladder shape ( R ² = 0.123, P = 0.017) supports the hypothesis that enhanced hearing and acoustic sensitivity contribute to otolith shape diversification in sciaenids. Our results establish 3DGM as a significant advancement in otolith research, offering a robust approach for quantifying shape disparity and understanding the combined effects of phylogeny and ecology across multiple levels of otolith structure. This 3DGM framework can be applied beyond Sciaenidae to reconstruct macroevolutionary history and identify drivers of otolith diversification over geological timescales using fossil otoliths.

Recent investigations of bottom-trawl bycatch around Dongsha Atoll, Taiwan, South China Sea have yielded numerous new records and undescribed fish species. Among the specimens collected, an unexpectedly large number of the Indian barracudina, Magnisudis indica (Ege, 1953), were obtained. Among its congeners in the family, M. indica is readily distinguishable by possessing the lowest number of total vertebrae (60–62). The adults of this species were extremely rare and by using these new adult materials we document intraspecific morphological variation in this species. Moreover, all examined specimens exhibit a strongly reduced or absent dentition on the jaws, gill rakers, and pharyngeal arches. This reduction of dentition reported here for M. indica may represent an ontogenetic condition in adults.

Fish otoliths are commonly found in the fossil record and are crucial for reconstructing past environments, especially in areas such as the Philippines, where well-preserved fish fossils are rare. This study analyzed fish otoliths from the Lower Pliocene clastic unit in Cabarruyan Island, northwestern Luzon Island, Philippines. The age of the sediments was constrained using calcareous nannofossil biostratigraphy, based on the last occurrence (LO) of Reticulofenestra pseudoumbilicus (Gartner, 1967) Gartner, 1969 and the first occurrence (FO) of Pseudoemiliania lacunosa Kamptner, 1963 ex Gartner, 1969. Bulk sediments were screen-washed, and individual otoliths were separated and identified. A total of 1,225 fish otoliths were analyzed, revealing 69 taxa in 28 families. We also report two new species: Benthosema rarang sp. nov. and Myctophum luzonicum sp. nov., as well as new fossil otolith records from the Philippines. The fish assemblage was dominated by the families Myctophidae, Sternoptychidae, Bregmacerotidae, Macrouridae, and Gobiidae, which agrees with findings from a previous study. The dominance of these families indicates an open marine environment and a tropical-to-subtropical climate during the Pliocene. The co-occurrence of deep- and shallow-water taxa in our study, together with other recorded fossils (e.g., fish vertebrae and scales, sea urchins, brachiopods, and other mollusks), suggests an outer-shelf-to-upper-slope paleoenvironment. This study not only provides an accurate age constraint for the marine sediments in Cabarruyan Island but also offers a significant opportunity to deepen our understanding of fish paleodiversity in the tropical West Pacific.

The Neogene Siwalik deposits have long been recognised for their rich terrestrial fossil record, yet their freshwater ichthyofauna remains virtually unknown. This gap limits our understanding of past aquatic ecosystems and the biogeographic history of South Asian freshwater fishes. In this study, we report the first fossil record of freshwater fish otoliths from the Upper Siwalik Pliocene deposits of Mohand, Saharanpur district, in the northwestern Himalaya, India. Three taxa Channa (Channidae), Trichogaster fasciata (Osphronemidae), and Gobiidae indet. were discovered through our extensive bulk sampling. Among these, T. fasciata represents the second known fossil record of Osphronemidae globally and the first based on otoliths. The assemblage reflects a structured trophic composition composed of mid-level preys and apex predators. These faunal components suggest a calm, possibly lentic freshwater habitat with dense vegetation, consistent with the spawning behaviour of labyrinth fishes and the hunting of snakeheads. Despite the limited number of otoliths, this collection provides rare but significant insights into Pliocene freshwater biodiversity in the Himalayan region.

Fossil records of porcupines ( Hystrix ) from island environments in East Asia have never been reported, leaving their Pleistocene dispersal and biogeographic history poorly understood. This study describes fossil remains of Hystrix subcristata from the Chochen–Tsailiao locality, south-western Taiwan. The locality, part of the Chiting Formation in Tainan, is dated to the Middle Pleistocene. The collection includes a well-preserved upper molar (M1/2), a lower last premolar (p4), a fragmentary lower molar (m1/2) and three fragmentary incisors. Biometric analysis indicates that the Chochen–Tsailiao specimens are smaller than H. refossa , but larger than H. lagrelii and H. vinogradovi and closely comparable in size to H. subcristata . Morphological features further corroborate this identification. This discovery is the first record of H. subcristata from Taiwan, representing both its easternmost known occurrence and the first island evidence for the genus, contrasting with all prior records which consisted only of mainland forms.

The family Sciaenidae comprises around 300 species and 70 genera, with the Indo-West Pacific (IWP) region exhibiting the highest species richness. The genus Boesemania Trewavas, 1977 was established as a monotypic group based on the swim bladder and otolith morphology of Johnius microlepis Bleeker. Corvina polykladiskos Bleeker was recognized as the third species of the genus Bahaba. Based on recent morphology and molecular evidence, we assign Bahaba polykladiskos to the genus Boesemania. Boesemania polykladiskos is distinguished from Boesemania microlepis by its distinctly larger scales, the number of lateral-line, upper and lower trans-lateral-line rows, and sagitta and swim-bladder morphology. Phylogenetic analysis of 24 sciaenid species representing 23 genera from the Indo-West Pacific region further confirms that Boesemania is monophyletic and that Boesemania polykladiskos is the sister species of Boesemania microlepis. The two Boesemania species are commercially important fish in their native range and play an essential role in the global luxury dried swim-bladder trade. However, significant knowledge gaps persist regarding their ecology, biology, and population status. Consequently, this paper also addresses the need for further research and conservation measures for these species.