The Japanese Society of Systematic Zoology Symposium 2015 entitled "Collaboration between taxonomists and paleontologists: Taxonomy and phylogeny of marine invertebrates using extant and fossil specimens" was held as a symposium of the 86th Annual Meeting the Zoological Society of Japan in Niigata on 17 September 2015. The four invited speakers gave their talks as follows: Yuki Tokuda "Morphological variability triggered by the changes in life history strategies of azooxanthellate solitary corals", Hayato Tanaka "Ostracodology reveals the connections between taxonomy and paleobiology", Takuma Haga "Tracking evolutionary history of pholadoidean boring bivalves-A combined approach by molecular phylogenetics and fossil scrutiny", and Masanori Okanishi "Evolutionary study of ophiuroids based on systematics, behavioral ecology and paleontology".
Marine sessile benthos living on hard substrates have evolved a variety of attachment strategies. Rhizotrochus (Scleractinia, Flabellidae) is a representative of azooxanthellate solitary scleractinians with a wide geographical distribution and unique attachment structures; it firmly attaches to hard substrates using numerous tube-like rootlets, which are extended from a corallum wall. In contrast, most sessile corals, whether extant or extinct, are attached by stereome-reinforced structures at their corallum bases. However, morphological and constructional traits of the rootlets themselves, along with their evolutionary significance, have not yet been fully resolved. Growth and developmental processes of spines in Truncatoflabellum and rootlets in Rhizotrochus suggest that these attachment structures are homologous. Both structures commonly develop from the calicular edges of walls through the transformation of wall structures, and their skeletal microstructures exhibit similar patterns of rapid accretion and thickening deposits. Taking molecular phylogeny and fossil records of flabellids into consideration, Rhizotrochus evolved from a common free-living ancestor and invaded hard-substrate habitats by the exploitation of rootlets originating from spines, which were adaptive for soft-substrates. Repeated evolution of attachment apparatuses in both scleractinian Rhizotrochus and extinct rugosans (e.g., Silurian Dokophyllum) is likely to represent evolutionary convergence. This study of attachment strategies in Rhizotrochus provides new insights into the understanding of not only the history of adaptive strategies of sessile benthos on changing substrates, but also the natures of soft tissues in extinct organisms.
Half a century ago, paleontology and biology were considered to be weakly connected. However, there should be no difference between the study of fossils and living species because the fossil record preserves the biological activities of past organisms. Under this conception, paleobiology which emphasizes biological aspects, has emerged. The small bivalved crustaceans known as ostracods have a long fossil record and high species diversity. Researchers of ostracods, called "ostracodologists" have been performing evolutionary biology and/or natural history studies based on descriptive taxonomy since early on the paleobiology era. The present paper reviews the peculiarity of Ostracoda regarding their paleobiological aspects, discuss the history of ostracod research, and put forth a preliminary study on the taxonomy of fossil and living Cladocopina (Ostracoda).
Paleontologists have long reconstructed phylogeny using comparisons between fossil record and recent taxa. On the other hand, biologists reconstruct phylogeny using molecules to produce a tree which they constrain using fossils and geographic events to provide estimates for phylogenetic events. Taking both extant and extinct species into account for systematic revisions is essential for biologists and paleontologists. In this paper, I demonstrate example of how paleontological methods, such as preparing thin sections and using x-ray and CT scans can also be applied to extant invertebrates. I provide further discussion of how robust integration between paleontologists and biologists is rewarding to both disciplines.
Two forms of test are known in a fibulariid sea urchin, Fibulariella acuta (Yoshiwara, 1898). One is a "rice grain-shaped" in which both the anterior and the posterior tips are pointed. Another is an "egg-shaped" in which the anterior tip is pointed but the posterior is broad. This species was originally described as "egg-shaped;" nevertheless, the post described drawing of the syntype by the same author showed its "rice grain-shaped." Although many taxonomic examinations have been made to understand the meaning of difference between the two forms, the meaning has not been clarified until today. We here compared the external morphologies of the test and pedicellariae between the two forms based on 59 specimens from Kumamoto Prefecture, Japan. In addition to the external outline of the tests, morphology of pedicellariae was clearly different between the rice grain-shaped and egg-shaped specimens as follows: the former had three types of pedicellariae (globiferous, bidentate, and biphyllous), whereas the latter had only two types (globiferous and bidentate). These morphological differences suggest that the two forms of F. acuta should be revised as two different species.
Sternaspid annelids are common and often abundant in the world ocean. They are usually corrected in sandy or muddy bottoms at a variety of depths. Sternaspid annelids are now known as characterized by the morphology of ventro-caudal shield, papillae of the body surface and posterior shield chaetae. Although sternaspid annelids recorded from Japan have been called as Sternsapis scutata since 1930s works, we could record two genera and seven species from Enshu-Nada, Kumano-Nada and off Sendai, East coast of Japan: Sternsapis scutata sensu strict, S. affinis, S. islandica, S. thalassemoides, S. costata, Petersenaspis capillata, and P. palpallatoci. Sternaspis has seven abdominal chaetigers and shield with radial ribs, concentric line or both. Petesenaspis has eight abdominal chaetigers and shield with poorly distinct ribs but no concentric line.