An official website of the United States government
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.
more »
« less
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.
more »
« less
- Award ID(s):
- 2127110
- PAR ID:
- 10621881
- 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
More Like this
-
-
Summary The Cycadales are an ancient and charismatic group of seed plants. However, their morphological evolution in deep time is poorly understood. While molecular divergence time analyses estimate a Cretaceous origin for most major living cycad clades, much of the extant diversity is inferred to be a result of Neogene diversifications. This leads to long branches throughout the cycadalean phylogeny that, with few exceptions, have yet to be rectified by unequivocal fossil cycads. We report a permineralized pollen cone from the Campanian Holz Shale located in Silverado Canyon, CA, USA ( c. 80 million yr ago). This fossil was studied via serial sectioning, SEM, 3D reconstruction and phylogenetic analyses. Microsporophyll and pollen morphology indicate this cone is assignable to Skyttegaardia , a recently described genus based on disarticulated lignitized microsporophylls from the Early Cretaceous of Denmark. Data from this new species, including a simple cone architecture, anatomical details and vasculature organization, indicate cycadalean affinities for Skyttegaardia . Phylogenetic analyses support this assignment and recover Skyttegaardia as crown‐group Cycadales, nested within Zamiaceae. Our findings support a Cretaceous diversification for crown‐group Zamiaceae, which included the evolution of morphological divergent extinct taxa with unique traits that have yet to be widely identified in the fossil record.more » « less
-
A well-supported genus-level classification of any group of organisms underpins downstream understanding of its evolutionary biology and enhances the role of phylogenetic diversity in guiding its conservation and management. The lorikeets (Psittaciformes: Loriini) are parrots for which genus-level systematics (phylogenetic relationships and classification) has long been unstable and unsatisfactory. Instability has manifested through frequently changing compositions of some genera (e.g. Trichoglossus and Psitteuteles). Other genera (e.g. Charmosyna, Vini) have become so large that their phenotypic heterogeneity alone at least questions whether they are monophyletic assemblages that genera should comprise. Recent molecular phylogenetic and phenotypic studies have improved the framework with which to rationalise genus-level systematics in lorikeets but some trenchant uncertainty has remained. Here we utilise published genomic data and tetrahedral analysis of plumage colour to develop a full review of the genus-level classification of lorikeets. Using existing phylogenetic relationships and a newly estimated time-calibrated tree for lorikeets, we show where paraphyletic assemblages have misled the classification of genera. We assign six species to three new genera and six other species to four previously described generic names that have been in synonymy in recent literature. Our taxonomic revision brings a new perspective informing and guiding the conservation and management of the lorikeets and their evolutionary biology.more » « less
-
Abstract This paper is the first in a two‐part series that charts the evolution of appendicular musculature along the mammalian stem lineage, drawing upon the exceptional fossil record of extinct synapsids. Here, attention is focused on muscles of the forelimb. Understanding forelimb muscular anatomy in extinct synapsids, and how this changed on the line to mammals, can provide important perspective for interpreting skeletal and functional evolution in this lineage, and how the diversity of forelimb functions in extant mammals arose. This study surveyed the osteological evidence for muscular attachments in extinct mammalian and nonmammalian synapsids, two extinct amniote outgroups, and a large selection of extant mammals, saurians, and salamanders. Observations were integrated into an explicit phylogenetic framework, comprising 73 character–state complexes covering all muscles crossing the shoulder, elbow, and wrist joints. These were coded for 33 operational taxonomic units spanning >330 Ma of tetrapod evolution, and ancestral state reconstruction was used to evaluate the sequence of muscular evolution along the stem lineage from Amniota to Theria. In addition to producing a comprehensive documentation of osteological evidence for muscle attachments in extinct synapsids, this work has clarified homology hypotheses across disparate taxa and helped resolve competing hypotheses of muscular anatomy in extinct species. The evolutionary history of mammalian forelimb musculature was a complex and nonlinear narrative, punctuated by multiple instances of convergence and concentrated phases of anatomical transformation. More broadly, this study highlights the great insight that a fossil‐based perspective can provide for understanding the assembly of novel body plans.more » « less
-
Etisine crabs are some of the most abundant cryptobionts in Indo-West Pacific coral reef systems. Despite their ecological importance and abundance in museum collections, several recent systematic studies have indicated family- to subspecies-level taxonomic problems. One such case involves the former chlorodielline genus Soliella Lasley, Klaus & Ng, 2015 (treated here as part of Etisinae), which currently comprises two valid species and three available names that have been in flux in recent literature. The validity of these taxa has only been cursorily discussed. To resolve species limits and distributions, a thorough morphological examination of hundreds of specimens was conducted, including scanning electron microscopy of male gonopods, along with analysis of sequence data of the mitochondrial marker cytochrome c oxidase subunit I (COI) from 84 exemplars across the distribution of the genus. The status of two species that have Indian Ocean versus Pacific Ocean distributions with overlap in the Indo-Australian Archipelago and adjacent regions is confirmed. While external morphology is not reliable for identification, a few discrete, although slight, differences in gonopod morphology were found, and these results are consistent with a “pseudocryptic species” designation. Speciation conforms to a previously published etisine model of allopatric differentiation followed by subsequent divergence of gonopod morphology upon secondary sympatry. This pattern, the biogeography of the two species, and the term “pseudocryptic species” are discussed.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1093/zoolinnean/zlaf056
