Phylogenetics, development, and Cenozoic paleontology of Buccinidae (Mollusca: Gastropoda).

摘要

The buccinid gastropods (family Buccinidae) are a species-rich clade of mostly North Pacific taxa with an abundant fossil record that dates to the Cretaceous. Here, the evolution, systematics, and biology of fossil and extant members of this family are treated using a variety of analytical and methodological approaches. In chapter one, a new fossil species of Bruclarkia, an endemic eastern Pacific buccinid from the Eocene, Oligocene, and Miocene, is described from the Astoria Formation of the Pacific Northwest. This species, B. ellenae, was discovered among fossil material of the University of California Museum of Paleontology and California Academy of Sciences and had been either overlooked or identified incorrectly in previous reviews of Astoria fauna.;In chapter two, all proposed Bruclarkia taxa are reviewed and re-described based on morphological characters determined from the largest examination of the genus to date. Intraspecific variation as well as autapomorphies and synapomorphies are characterized from hundreds of fossils that were measured and scored. Results suggest that of the twenty proposed Bruclarkia taxa, only seven are valid. The majority of remaining species are either synonymous with valid taxa or named from type material that is insufficient for suitable description. The value of Bruclarkia acuminata, B. barkeriana, and B. gravida, as index fossils is emphasized and the paleobiogeography of these and other Bruclarkia lineages throughout California, Oregon, Washington, Vanouver Island, Canada, and Alaska is reviewed.;In chapter three, the molecular phylogenetic systematics of 43 buccinid taxa mostly from Japanese waters is presented. Phylograms are based on Bayesian and maximum likelihood analyses of approximately 1500 base pairs from the mitochondrial gene CO1 and 625 base pairs from the nuclear gene 28S. These data suggest that: (1) Buccinidae is monophyletic, though the placement of several genera (e.g. Lirabuccinuum, Microfusus, and Solenosteira) is poorly resolved, (2) the genera Busycon and Busycotypus, which have often been classified in the family Melongenidae, belong within Buccinidae, (3) the subfamilies Beringiinae, Buccininae, Busyconinae, Neptuneinae, and Photinae are monophyletic, and (4) the genera Neptunea, Buccinum, and Busycon are also monophyletic. General characters of larval development in selected buccinids are presented in a cladistic framework, which reveals two species (Kelletia kelletii and Volutharpa perryi ) from different subfamilies that both have planktonic larvae.;In chapter four, the early development of the California buccinid Kelletia kelletii is reviewed with new observations of larval asymmetries and feeding ability during incapsulation and after hatching. Larval shells and veligers were visualized under optical microscopy and SEM to observe fine-scale morphology at various ontogenetic stages. These observations reveal that: (1) intracapular veligers are capable of particle capture and transport but not ingestion, (2) hatching time varies between approximately 35 to 60 days depending on water conditions and temperature, (3) intracapsular larvae do not eat undeveloped eggs and/or embryos though they are present in all capsules, (4), pre-hatched veligers swim in the plankton if excapsulated at 27 days old and older, (5) within the capsule, veliger velar lobes are symmetrical but the right cephalic tentacles is larger than the left, (6) at 2.5 weeks in the plankton, both the right cephalic tentacle and right velar lobe are larger than those on the left, and (7) larval shells are brittle at emergence but calcify and grow apertural beaks and proto-siphonal canals by 2.5 weeks in the plankton.;Finally, in chapter five, a new method for replicating gastropod protoconchs (larval shells) is presented. It is based on protocols used in vertebrate paleontology for molding and casting micro-mammal and other small vertebrate teeth. Molding requires clean and periostracum-free shell apexes to be covered with a dental-grade polyvinylsiloxane impression material. Casts are made from molds using tinted epoxy resin and can be re-cast multiple times from the same mold without deterioration in cast quality. The practical applications of this technique to gastropods are substantial because for many snails, the protoconch indicates larval developmental mode as either planktonic or non-planktonic. Resulting casts can be examined in small SEM machines that could not accommodate the full gastropod shell, and can be made from specimens that would be otherwise be prohibited from such studies (e.g. living specimens, shells from protected land or private collections, type specimens, etc.). (Abstract shortened by UMI.)