The study of palynomorphs based on pollen and fern spore assemblages and their ecological characteristics has a long history of more than 100 years. In the history of this kind of the research, much attention has been paid to palynomorphs other than pollen and fern spores. However, the majority of these palynomorphs are dormant cells including resting eggs, hypnozygotes and resting spores (cyst) of various aquatic organisms, and their morphology is markedly different from that of their parent organisms. This has often prevented the identification of the parental organisms of these palynomorphs preserved in sediments. This paper focuses on the components of the aquatic palynomorph assemblage in the Quaternary sediments of Japan - mainly in the surface sediments of coastal waters. These aquatic palynomorphs included dinoflagellate cysts, raphidophyte Chattonella cysts, prasinophyte phycoma, resistant cells and colonies of green algae (primary producers), ciliate lorica and cysts, benthic foraminifera linings, resting eggs of cladocera and copepoda, testate amoebae, turbellarian egg capsules, jaws of annelids, and acritarchs (primary and low-level consumers). With the taxa to which they belong to higher taxonomic ranks, the description focuses on morphological and ecological characteristics and the fossil record. The purpose of this paper is to contribute to the palaeoecology of aquatic palynomorph assemblages, which aims to reveal aspects of past climatic changes and geological events that can be interpreted from the aquatic fossil palynomorph assemblages.

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This paper describes the aquatic palynomorphs of microfaunal remains (fossils) that are mainly first consumers in the food chain. These palynomorphs include lorica and cysts of protozoan ciliates, shells of testate amoebae, linings of benthic foraminifera, dormant eggs and body parts of crustacea, turbellarian egg capsules, and maxillary organs of annelids. These microfaunal remains have quite different morphologies from those of parent organisms. Acritarchs, which are treated as organic-walled microfossils of unknown affiliation in micropaleontology, because their parent organisms are currently unknown, but probably eukarotic organisms, and are classified mainly on the basis of morphological characteristics, are also described in this paper. As mentioned in the previous paper (Constituent organisms of aquatic palynomorph assemblage - Part 1 primary producers), one of the goals of paleoecology is to elucidate the interrelationships among organisms. The relationship between resting egg of copepods and dinoflagellate cysts preserved in sediments was examined, because it is known that copepods, which are abundant in the aquatic palynomorphs of coastal waters, feed on various organisms including dinoflagellates.

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Charophyte gyrogonites, isolated teeth of crocodylomorphs, ornithopods and sauropods, and theropod eggshells, found from the Lower Cretaceous (lower to middle Albian) Ohyamashimo Formation of the Sasayama Group at Tambasasayama and Tamba cities, Hyogo Prefecture, Japan, were newly described, classified, and discussed, and their taxonomic diversity in this formation was examined. Charophyte gyrogonites were identified as Characeae based on their five spiral cells converging at the tips and the absence of an utricle. Crocodylomorph teeth were classified in seven morphotypes based on the size, shape, and surface structure. Morphotypes I-III were assigned to Atoposauridae, whereas morphotypes IV-VI belong to Neosuchia, and morphotype VII belongs to Metasuchia. Ornithopod teeth include two dental types, styracosternan maxillary and ankylopollexian dentary teeth. If these teeth belong to a single taxon, derived styracosternan iguanodontians, which are more basal than Xuwulong, are possible candidates for these teeth. Sauropod teeth were classified into two distinct taxa: one resembling Tambatitanis and another earlier diverging taxon. Eggshells were classified into three ootaxa: Nipponoolithus ramosus, Elongatoolithus oosp., and indeterminate theropods. These results expand our knowledge of the spatial and chronological distributions of terrestrial taxa in the Ohyamashimo Formation, which partly sheds light on ecosystem transitions in the region.

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