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n examining Plio-pleistocene turritellids from the Atlantic coastal plain we recently discovered a previously undescribed character state where the inner shell wall appears to have not been formed. This state along with a C1B2A3 apical ontogeny pattern for spiral sculpture appears to characterize a clade of turritellids now extirpated from Florida and the Atlantic coastal plain, but including several common eastern Pacific species. We designate Turritella gonostoma Valenciennes, 1832 as the type species for this genus and refer the eastern Pacific species Turritella banksii Gray in Reeve, 1849, Turritella broderipiana d’Orbigny, 1840, Turritella abrupta† Spieker, 1922 along with several western Atlantic fossil species to this genus. It is likely that numerous additional fossil and extant eastern Pacific turritellids should be referred to this genus. We designate this newly described character state as hollow newel morphology, based on an analogy to spiral staircases where the absence of a central supporting post is termed hollow (or open) newel construction. The hollow newel state also occurs in other gastropod taxa, though it appears to be rare among those with high spires. We also distinguish this state from other axis forms including a columella, an umbilicus, a hollow columella, and a partially resorbed columella.
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The slug within the bivalve: molecular and morphological systematics of the family Juliidae (Gastropoda: Panpulmonata: Sacoglossa)
Abstract The discovery of bivalved sea slugs in the family Juliidae revolutionized our understanding of shell evolution in molluscs. However, relationships among lineages remain unclear, with generic names shared by extant and fossil taxa. Juliidae provide important fossil calibration points for dating phylogenies and for understanding the convergent evolution of a bivalved shell. Here, we present a revision of the systematics and classification of members of the Juliidae including Recent and fossil taxa by integrating molecular data from five genes, geometric morphometrics, and anatomical data. A list of all juliid taxa previously described is provided, along with diagnoses and remarks on genus-level names. Results from a geometric morphometric analysis support a new classification scheme, in which the genus Berthelinia, previously used for Recent and fossil taxa, is restricted to fossil species, and the genera Julia and Edenttellina are used exclusively for Recent species. Species of Edenttellina supported by molecular analyses are illustrated and anatomical details provided, including examination of protoconchs, radular teeth, and reproductive structures by scanning electron microscopy, along with illustrations of existing type material. Distinct biogeographical patterns in Julia and Edenttellina are discussed in the context of ecological differences between these two taxa, including host specificity and developmental mode.
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- Award ID(s):
- 2127110
- PAR ID:
- 10600846
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Zoological Journal of the Linnean Society
- Volume:
- 204
- Issue:
- 2
- ISSN:
- 0024-4082
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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