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Systematics and Phylogeny of Plio-Pleistocene Species of Turritellidae (Gastropoda) from Florida and the Atlantic Coastal Plain
Abstract
Turritellid gastropods are among the most widespread, abundant, and diverse mollusks in Plio-Pleistocene deposits of the Atlantic coastal plain and Florida, with at least 46 species and subspecies described over almost two centuries. Yet the systematic status of these common fossil species and their phylogenetic relationships—to each other and to turritellids living today in the western Atlantic—have never been investigated in detail. We make use of recent molecular phylogenetic work on living turritellids and new analyses of shell characters to review the group from this time interval to the present in a comprehensive phylogenetic analysis and assessment of their evolutionary history in the region. We conclude that 20 fossil and two Recent species are valid. Four of these species are placed in the genus Torcula Gray, 1847; five in Caviturritella new genus, and eleven in “Turritella” sensu lato. We identify Torcula perattenuata as the likely direct ancestor of one of the two turritellid species living today off the southeastern U.S. coast, Torcula exoleta, and we elucidate the fossil record of the other extant species, “Turritella” perexilis (senior synonym of Turritella acropora). We show that Caviturritella was extirpated from the United States Gulf and Atlantic coastal plains in the Early Pleistocene but is still represented in the western Atlantic by the living species C. variegata in the southern Caribbean. We also present the first detailed treatment of Plio-Pleistocene turritellid fossils from Georgia. Our analysis shows that the PlioPleistocene Pinecrest beds of Florida contain 18 co-occurring turritellid species, which is the highest turritellid species diversity in one formation known in the fossil record.
... We excluded the turritellid genus Vermicularia, which has a different ecology (generally more reef-associated) and morphology (Vermicularia are uncoiled, making axial length comparisons non-analogous) when compared with other turritelld genera [90]. A recent phylogenetic treatment of Pliocene-to-recent species in Florida and the Atlantic Coastal Plain [66] indicated that at least three evolutionary lineages of non-Vermicularia turritelline gastropods were present, with two of these recognized as the genera Caviturritella and Torcula. Twenty fossil species were present in the Plio-Pleistocene of Florida and the Atlantic Coastal Plain, but only two remain in the region: Torcula exoleta (likely the direct descendant of T. perattenuata [66]) and Turritella (sensu lato) perexilis (= Turritella acropora [66]). ...
... A recent phylogenetic treatment of Pliocene-to-recent species in Florida and the Atlantic Coastal Plain [66] indicated that at least three evolutionary lineages of non-Vermicularia turritelline gastropods were present, with two of these recognized as the genera Caviturritella and Torcula. Twenty fossil species were present in the Plio-Pleistocene of Florida and the Atlantic Coastal Plain, but only two remain in the region: Torcula exoleta (likely the direct descendant of T. perattenuata [66]) and Turritella (sensu lato) perexilis (= Turritella acropora [66]). ...
... A recent phylogenetic treatment of Pliocene-to-recent species in Florida and the Atlantic Coastal Plain [66] indicated that at least three evolutionary lineages of non-Vermicularia turritelline gastropods were present, with two of these recognized as the genera Caviturritella and Torcula. Twenty fossil species were present in the Plio-Pleistocene of Florida and the Atlantic Coastal Plain, but only two remain in the region: Torcula exoleta (likely the direct descendant of T. perattenuata [66]) and Turritella (sensu lato) perexilis (= Turritella acropora [66]). ...
The Plio-Pleistocene turnover event in the western Atlantic following the closure of the Central American Seaway involved high rates of extinction for both gastropod and bivalve molluscs. This extinction was associated with declining nutrient conditions and has been presumed to be associated with a decrease in molluscan body size. Previous work which has been concordant with this expectation, however, has either focused on bivalves or not considered the effects of the recovery post extinction. In three phylogenetically diverse clades, we found that body-size evolution in gastropods across the turnover event is likely tied to ecology. One clade increased in size, one decreased, and another exhibited no substantial change. Individual species lineages exhibit a mixture of microevolutionary changes from the Pliocene to today. This study indicates that gastropod body-size evolution may be more complex than in bivalves, with ecology and other functional traits playing a significant role. Macroevolutionary processes, especially whether a clade re-radiated post extinction, were found to be important. Indeed, a low portion of extant diversity consists of survivors from clades that increased in size or have similar size distributions among their species relative to the Pliocene.
... A number of fossil and living species in the family Turritellidae possess openings in the basal end of the columellar region that at first appear to be examples of true umbilici, but which on closer examination are structurally distinct morphological features ( Fig. 4 ) that have not been previously recognized or named. Our original observation of this trait occurred during a systematic study on Turritellidae from the Pliocene-Pleistocene of Florida and the Atlantic coastal plain of the USA (Friend et al. , 2023 ). The axial hollow opening was first observed in a large specimen of "Turritella alumensis " Dall, 1892 that (importantly) lacked an apex. ...
... In other words, the outermost shell walls (exterior of the shell) formed a tube within which a helical platform coiled, extending from the outer whorl wall inwards, leaving a central column of hollow space. This helical platform is formed as the floor of the aperture, and in columnate taxa, it would connect the Fretter & Graham (1962) . Abbreviations: col, columella; umb, umbilicus. ...
... All of the major body retractor muscles in shelled gastropods originate from the columellar muscle , which is the only muscle attached to the calcified shell (Fretter & Graham, 1962 ;Price, 2003 ). In coiled gastropods with a columella, this insertion takes place on a single area on the columella of the shell, leaving a muscle scar in some cases. ...
[Research note with no associated abstract]; The below is an abstract used for an associated conference presentation;
Terminology for features associated with the coiling axis of gastropods is ambiguous and incomplete. Herein we describe the state of having no inner shell wall as a “hollow newel” construction, following the terminology applied to the analogous situation in spiral staircases lacking a central supporting column. For shells with the hollow newel axial state, a basal opening of the shell permits access to the body chamber of the shell many whorls beyond the aperture. We also clarify other states that can describe the relationship of a shell to its coiling axis, including having a solid columella, an umbilicus, a hollow columella, or a partially resorbed columella, and distinguish these from the hollow newel state. The first observation of a hollow newel occurred during a systematic analysis of Plio-Pleistocene turritellids from Florida and the Atlantic Coastal Plain in the species “Turritella alumensis †”. We searched for additional hollow newel taxa by slicing shells axially, with micro-CT scans, and by designing a test using a sewing needle. The hollow newel state appears to be a phylogenetically informative character in at least one group of turritellids, where it characterizes a clade first identified based on molecular phylogenetics, which we named Caviturritella (Friend et al. 2023). The hollow newel state also occurs in other gastropod taxa, though it appears to be rare among those with high spires. We examine potential evolutionary scenarios for the origin of hollow newel morphology in turritellids, although the apparent single origin of the character and its apparent subsequent retention limits our ability to test these hypotheses without additional developmental data. This feature appears to facilitate achievement of large body size relative to co-occurring turritellid species and may therefore be a means of reallocating calcification effort to axial growth. The observation of this apparently novel, unnamed character in an abundant and commonly occurring family of gastropods illustrates the need for continued descriptive and observational malacology.
Plio-Pleistocene sediments from the southwestern Florida Peninsula contain an extraordinary density and diversity of marine mollusk and vertebrate fossils which, collectively, document major faunal shifts on the Florida Platform through a period of profound environmental change. Systematic study of these fossil assemblages and the environments in which they lived has been limited, however, by: i) a lack of outcrop sections spanning the full Plio-Pleistocene stratigraphy of the region and ii) major uncertainties in correlation between previous study sites due to extreme lateral variability in coastal paleoenvironments. Here, we describe a new stratigraphic section from Florida Shell Quarry in Charlotte County, Florida, which contains fossil-rich deposits of each major Plio-Pleistocene unit in the area (the Tamiami, Caloosahatchee, Bermont, and Fort Thompson formations). Bulk sediment samples collected from 22 horizons were used to broadly characterize stratigraphic variations in lithology and faunal content. Predation intensity was estimated from drill-hole frequency among populations of the bivalve Chione spp. While all studied formations were mainly deposited under marine conditions, both lithologic and faunal facies shifts within the Caloosahatchee and Bermont units indicate periods of pronounced freshwater influence. Faunal diversity is relatively high in the Tamiami, Caloosahatchee, and Bermont units but declines in the Fort Thompson. Similarly, predation intensity is high in the Caloosahatchee and Bermont units but lower in the Fort Thompson at the sampled sites. In addition to characterizing changes in the local paleoenvironment, we propose a sequence stratigraphic model for the section based on inferred local sea-level fluctuations. We leverage this sequence stratigraphic framework to correlate the Florida Shell section with other studied sections in the Charlotte Harbor area. The development of this new site provides a workable basis for more detailed studies of the long-term paleoecological and paleoenvironmental evolution of southwestern Florida.
Vermicularia Lamarck, 1799 is a clade of Miocene–Recent gastropods with an unusual
uncoiled shell morphology. Like other “worm-snails,” they are taxonomically troublesome, and although earlier work affirmed the turritellid affinity of one species, their systematic relationships have not otherwise been previously examined. Here, we present a molecular phylogeny of turritellids, including members of other previously named genera [Mesalia Gray, 1847; Zaria Gray, 1847; Torcula Gray, 1847; Protomella Thiele, 1929; Maoricolpus Finlay, 1926; and the recently named Turritellinella Harzhauser & Landau, 2019, represented by Turritellinella tricarinata (Brocchi, 1814) = “Turritella communis” Risso, 1826], to establish the monophyly of Vermicularia and determine higher level relationships. We provide a revised taxonomy with detailed diagnoses for all known living and fossil species of Vermicularia, including the synonymy of Vermicularia lumbricalis (Linnaeus, 1758) and the commonly used junior synonym Vermicularia knorrii (Deshayes, 1843). The new Plio–Pleistocene species Vermicularia katiae n. sp. is described from the Dominican Republic. The phylogenetic relationships within living and fossil Vermicularia are also established based on morphological characters and with close outgroup turritelliform species chosen based on the molecular phylogeny. Callostracum gracile (Maltzan, 1883) was found to be well nested among the other species and is reassigned to Vermicularia herein as Vermicularia gracilis (Maltzan, 1883). The reconstructed phylogeny indicates that new species arose via cladogenesis much more frequently than by anagenesis, with most lineages originating in the Pliocene, but prior to the complete closure of the Central American Seaway ~ 3.5 million years ago.
In 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.
The Yorktown Formation records paleoclimate conditions along the mid-Atlantic Coastal Plain during the mid-Piacenzian Warm Period (3.264 to 3.025 Ma), a climate interval of the Pliocene in some ways analogous to near future climate projections. To gain insight into potential near future changes, we investigated Yorktown Formation outcrops and cores in southeastern Virginia, refining the stratigraphic framework. We analyzed 485 samples for alkenone-based sea surface temperature (SST) and productivity estimates from the Holland and Dory cores, an outcrop at Morgarts Beach, Virginia, and the lectostratotype of the Yorktown Formation at Rushmere, Virginia, and analyzed planktonic foraminferal assemblage data from the type section. Using the structure of the SST record, we improved the chronology of the Yorktown Formation by establishing the maximum age ranges of the Rushmere (3.3–3.2 Ma) and Morgarts Beach (3.2–3.15 Ma) Members. SST values for these members average ~26 °C, corroborating existing sclerochronological data. Increasing planktonic foraminifer abundance, productivity, and species diversity parallel increasing SST over the MIS M2/M1 transition. These records constitute the greatest temporal concentration of paleoecological estimates within the Yorktown Formation, aiding our understanding of western North Atlantic temperature patterns, seasonality and ocean circulation during this interval. We provide a chronologic framework for future studies analyzing ecological responses to profound climate change.
We examined the collection in the Museum der Natur Gotha (mng) for specimens of Stromboidea, once in the collection of the German physicist Joachim Friedrich Bol-ten, first described in a sales catalogue by Peter Friedrich Röding in 1798 and subsequently auctioned in 1819. We were able to recognize nine specimens of Stromboidea originating from the Bolten collection with certainty, all once in the private collection of Friedrich Christian Schmidt, that is indicated as ex Bolten in the collection catalogue of mng. Apart from that, we discovered 45 specimens acquired possibly once being part of the Bolten collection. A critical listing of all Stromboidea we encountered in Röding's sales catalogue is added. Names attributed to Bolten (= Röding) by the compiler of the catalogue in mng are discussed. Turris operosa Röding, 1798 is the first available name for Strombus turritus Lamarck, 1822 (non Röding, 1798 nec Link, 1807) and is here recombined to Doxander operosus (Röding, 1798) comb. nov.. The family-level taxon Seraphsi-dae should be attributed to Gray, 1853 and the genus-level taxon Terebellum should be attributed to Bruguière, 1798. Lectotypes are designated for: Lambis velum; Lambis con torta; Tibia indiarum; Turris operosa; and Terebellum lin eatum all of Röding, 1798. There are two different printings of the Museum Boltenianum by Röding. Possible future research is briefly addressed.
For inclusion within a new reference text on marine molluscan biogeography, four new gastropods are described here in anticipation of the publication of the book. These include: Stramonita alderi n. sp. (Muricidae) from the Texan Subprovince, Carolinian Province; Turritella (Torcula) howardpetersi n. sp. (Turritellidae) and Prunum sunderlandorum n. sp. (Marginellidae) from the Nicaraguan Subprovince, Caribbean Province; and Charonia marylenae n. sp. (Charoniidae) from the Janeiran Subprovince, Paulinian Province.
Caribbean biota underwent major ecological and evolutionary transformation in the Pliocene–Pleistocene, but a lack of detailed paleoenvironmental reconstruction prevents thorough resolution of cause and effect. We quantify levels of upwelling and freshwater input into Caribbean coastal shelf ecosystems over the last ~6 m.y. with >3300 stable isotope measurements from 74 fossil serially sampled gastropods by normalizing δ18O values to open-ocean δ18O from planktonic foraminifera. We find that the influence of Pacific-like upwelling in the southwestern Caribbean was low after 4.25 Ma but coastal ecosystems were heavily influenced by seasonal freshening until ca. 2.5 Ma, after which time low-freshwater conditions were established. The origination of modern oligotrophic coastal conditions was therefore a result of oceanographic change causing declining upwelling, and declining nutrients from terrestrial sources. We speculate that a southward shift of the Intertropical Convergence Zone, associated with Northern Hemisphere glaciation, reduced rainfall and terrestrial nutrient input and contributed to biotic turnover in the southwestern Caribbean, including the proliferation of modern reef communities.
The closure of the late Neogene interoceanic seaways between the Western Atlantic (WA) and Tropical Eastern Pacific (TEP)-commonly referred to as the Central American Seaway-significantly decreased nutrient supply in the WA compared to the TEP. In marine invertebrates, an increase in parental investment is expected to be selectively favored in nutrient-poor marine environments as prolonged feeding in the plankton becomes less reliable. Here, we examine turritelline gastropods, which were abundant and diverse across this region during the Neogene and serve as important paleoenvironmental proxies, and test whether species exhibit decreased planktotro-phy in the WA postclosure as compared to preclosure fossils and extant TEP species. We also test for differences in degree of planktotrophy in extant sister species pairs. Degree of planktotrophy was inferred by measuring the size of protoconchs, the spe-cies' larval shell that represents egg size. Protoconch size was compared between extant postclosure WA and TEP species and preclosure fossil species. To compare extant sister species, we reconstructed the phylogeny of available WA and TEP species using one nuclear (H3) and three mitochondrial markers (12S, 16S, and COI). Compared to the preclosure fossils, protoconch size increased in WA species but remained the same in the TEP species. In the two extant sister species pairs recovered in the phylogenetic analysis, the WA species are inferred to be nonplanktotrophic while the TEP species are planktotrophic. This suggests that decreased nutrient availability and primary productivity in the WA may have driven this change in developmental mode, and was the primary selective force resulting in postclosure turritelline extinctions.
Turritellid gastropods are important components of many Cretaceous–Recent fossil marine faunas worldwide. Their shell is morphologically simple, making homoplasy widespread and phylogenetic analysis difficult, but fossil and living species can be recognized based on shell characters. For many decades, it has been the consensus that the oldest definite representatives of Turritellidae are from the Lower Cretaceous, and that pre-Cretaceous forms are homeomorphs. Some morphological characters of the present turritelline species resemble those of mathildoids, but many diagnostic characters clearly separate these two groups. We here describe and/or redescribe—based on examination of more than 2600 near complete specimens—four species from the Upper Jurassic Dhosa Oolite Member of the Chari Formation in Kutch, western India, and demonstrate that they are members of Turritellidae, subfamily Turritellinae, on the basis of diagnostic characters including apical sculptural ontogeny (obtained from SEM study), spiral sculpture, and growth line patterns. The four species are in order of abundance, Turritella jadavpuriensis Mitra and Ghosh, 1979; Turritella amitava new species; Turritella jhuraensis Mitra and Ghosh, 1979, and Turritella dhosaensis new species. The turritelline assemblages occur only on the northeastern flank of the Jhura dome (23°24’47.57”N, 69°36’09.26”E). Age of the Dhosa Oolite has recently been confirmed based on multiple ammonite species. All these points indicate that these fossils are the oldest record of the family Turritellidae—by almost 30 million years—in the world.
The history of the discovery of early fossils attributed to the genus Homo has been contentious, with scholars disagreeing over the generic assignment of fossils proposed as members of our genus. In this manuscript I review the history of discovery and debate over early Homo and evaluate the various taxonomic hypotheses for the genus. To get a sense of how hominin taxonomy compares to taxonomic practice outside paleoanthropology, I compare the diversity of Homo to genera in other vertebrate clades. Finally, I propose a taxonomic model that hews closely to current models for hominin phylogeny and is consistent with taxonomic practice across evolutionary biology.
A matched pair of otoliths (right and left saccular otoliths) and associated skeletal remains (n = 107) of Apogon townsendi (belted cardinalfish) were obtained in unconsolidated sediment from inside the valves of an articulated scallop Carolinapecten eboreus. The scallop specimen was collected in Hendry County, Florida, from the lower Pleistocene Caloosahatchee Formation, approximately 1.7 to 2.1 Ma. The recovery of this vertebrate material is highly significant because no skeletal remains of bony fish with in situ or associated otoliths are known from the Gulf or Atlantic coasts of the United States. Furthermore, the specimen represents the first fossil record of the family Apogonidae and the genus Apogon from Florida and the first report of the species Apogon townsendi in the fossil record. The length of the fossil Apogon townsendi was determined to be 4.7 cm based on the linear relationship between fish length and otolith length and utilizing modern specimens of the species for comparison and analysis. The length of the fossil Apogon townsendi indicated that it was an adult fish upon death (> 2.1 cm). Although several taphonomic scenarios are considered, including commensalism, it is believed that the apogonid died in close proximity to the empty scallop shell, which was followed by fairly rapid washing in of sediment with the fish into the valves of the scallop (i.e., sediment trapping). This determination is based on several factors including the biology, distribution, and behavior of extant Apogon townsendi. The presence and preservation of the two matched saccular otoliths and the large number of associated, fragile skeletal remains in the scallop shell suggest that the apogonid was not ingested and excreted by a piscivorous predator.
The formation of the Isthmus of Panama stands as one of the greatest natural events of the Cenozoic, driving profound biotic transformations on land and in the oceans. Some recent studies suggest that the Isthmus formed many millions of years earlier than the widely recognized age of approximately 3 million years ago (Ma), a result that if true would revolutionize our understanding of environmental, ecological, and evolutionary change across the Americas. To bring clarity to the question of when the Isthmus of Panama formed, we provide an exhaustive review and reanalysis of geological, paleontological, and molecular records. These independent lines of evidence converge upon a cohesive narrative of gradually emerging land and constricting seaways, with formation of the Isthmus of Panama sensu stricto around 2.8 Ma. The evidence used to support an older isthmus is inconclusive, and we caution against the uncritical acceptance of an isthmus before the Pliocene.
Après un examen rapide des principaux types de concepts de genre en zoologie, nous proposons de considérer les genres comme des unités évolutives, c'est-à-dire des unités à la fois phylogénétiques, génétiques et écologiques. Unités phylogénétiques: les genres doivent être des taxons monophylétiques au sens de Ashlock (1971), c'est-à-dire holophylétiques ou paraphylétiques mais non polyphylétiques. Unités génétiques: les genres doivent regrouper des espèces ayant une grande similarité génétique; parmi plusieurs méthodes envisageables pour mesurer celle-d, attention est attirée sur l'intérêt de l'étude de l'hybridation interspécifique, et il est notamment suggéré que lorsque deux espèces peuvent donner naissance entre elles à des hybrides adultes viables, ces deux espèces doivent être incluses dans le même genre, et de plus que si ces deux espèces étaient auparavant classées dans des genres distincts, ceux-ci doivent être réunis. Unites écologiques: les genres doivent être conçus comme des ensembles d'espèces occupant des zones adaptatives données. Les genres définis par ces critères sont des unités évolutives naturelles, séparées par des discontinuités. L'apparition d'un nouveau genre (géniation), qui implique une « révolution génétique », est un phénomène évolutif très important, comportant le passage dans une zone adaptative nouvelle. Les genres tels que nous les entendons peuvent être relativement vastes, et il est utile de reconnaitre en leur sein des sous-unités taxinomiques, telles que superspecies, ultraspecies, complexe d'espèces, groupe d'espèces et sous-genre: ces catégories sont discutées et comparées, et des exemples de leur emploi sont donnés.
The genus is one of the most important taxonomic categories because it appears in the two-part species name, is easier to identify than the species, and is very commonly the least inclusive category employed in paleontological, ecomorphological, phylogenetic, evolutionary, and biogeographic comparisons. However, the theoretical and practical definitions of genera have received little attention in the New World monkey literature. Six genus-level changes in platyrrhine taxonomy have been suggested since 1998. The genera Leontocebus, Mico, Oreonax, and Sapajus, have been revalidated and Callibella and “Torquatus” proposed as new. Divergence time is becoming the favored criterion when defining genera, but most molecular phylogenetic studies date the divergence between alleles, not between species, which is the actual date of interest when studying systematics. I here review the recent genus-level changes in platyrrhine taxonomy and propose that we adopt a “focused monophyly” approach for defining genera that overlays a wide variety of morphological, behavioral, and ecological characteristics on the molecular phylogeny to produce a classification. This proposal aims to facilitate communication among researchers and to offer a robust, more predictive, taxonomy that will better withstand future investigations.
In order to predict the fate of biodiversity in a rapidly changing world, we must first understand how species adapt to new environmental conditions. The long-term evolutionary dynamics of species' physiological tolerances to differing climatic regimes remain obscure. Here, we unite palaeontological and neontological data to analyse whether species' environmental tolerances remain stable across 3 Myr of profound climatic changes using 10 phylogenetically, ecologically and developmentally diverse mollusc species from the Atlantic and Gulf Coastal Plains, USA. We additionally investigate whether these species' upper and lower thermal tolerances are constrained across this interval. We find that these species' environmental preferences are stable across the duration of their lifetimes, even when faced with significant environmental perturbations. The results suggest that species will respond to current and future warming either by altering distributions to track suitable habitat or, if the pace of change is too rapid, by going extinct. Our findings also support methods that project species' present-day environmental requirements to future climatic landscapes to assess conservation risks.
Many modern paleobiological analyses are conducted at the generic level, a practice predicated on the validity of genera as meaningful proxies for species. Uncritical application of genera in such analyses, however, has led—perhaps inadvertently—to the unjustified reification of genera in an evolutionary context. While the utility of genera as proxies for species in evolutionary studies should be evaluated as an empirical issue, in practice it is increasingly assumed (rather than demonstrated) that genera are suitable proxies for species. This is problematic on both ontological and epistemological grounds. Genera are arbitrarily circumscribed, non-equivalent, often paraphyletic, and sometimes polyphyletic collections of species. They are useful tools for communication but have no theoretical or biological reality of their own and, whether monophyletic or not, cannot themselves operate in the evolutionary process. Attributes considered important for understanding macroevolution—e.g., geographic ranges, niche breadths, and taxon durations—are frequently variable among species within genera and will be inflated at the generic level, especially in species-rich genera. Consequently, the meaning(s) of results attained at the generic level may not “trickle down” in any obvious way that elucidates our understanding of evolution at the species level. Ideally, then, evolutionary studies that are actually about species should be pursued using species-level data rather than proxy data tabulated using genera. Where genera are used, greater critical attention should be focused on the degree to which attributes tabulated at the generic level reflect biological properties and processes at the species level.
During the Mid-Miocene Climatic Optimum (MMCO, 14.7–17.3 Ma), global temperatures were warmer than present, and similar to predicted temperatures for the coming century. Limited paleoclimate data exist from the tropics during this period, despite its potential as an analog for future climate conditions. This study presents new subannual stable isotope data (δ18O and δ13C) from a large population of Miocene Turritella gastropods from the Jimol and Castilletes Formations of the Guajira Peninsula, Colombia. Turritellids are aragonitic marine mollusks that live in shallow coastal waters, and their rapid growth rates allow for high-resolution subannual records. We compare these fossils to modern Turritella gastropods from multiple tropical localities to reconstruct subannual climate conditions. The seasonal range in δ18O in the modern shells correlates with the seasonal variance of local precipitation, once temperature seasonality is accounted for. The Miocene fossils show larger (in some cases >2‰) seasonal variation in δ18O than modern Turritella from the same location, suggesting increased seasonality of precipitation in Miocene northern Colombia relative to today. We propose that this increased seasonality of precipitation was due to a more northerly position of the Intertropical Convergence Zone during the mid-Miocene. The resulting wet Miocene paleoenvironment is in stark contrast to semiarid conditions on the Guajira Peninsula today, indicating that this area of tropical South America has undergone a drastic environmental change since the Miocene.
Turritella abrupta (Miocene-Pliocene) is the largest species known from the diverse Jurassic-Recent gastropod family Turritellidae. In addition to having achieved long length and substantial width, the species produces shells of exceptional thickness, even before secondary shell deposition. We investigated the paleoecology of this species through analysis of drilling and peeling frequencies with comparisons to co-occurring turritellid species. We used oxygen isotopic sclerochronology to infer the growth rate and lifespan of T. abrupta and to make comparisons with other modern and fossil tropical species, including the living species Turritella terebra, with the first sclerochronologies for both of these species presented herein. We find that T. abrupta was fast-growing, long-lived, and comparatively effective at resisting predation. T. abrupta was notably widespread geographically and temporally, but was a relatively rare component of faunas when compared with co-occurring turritellids. High rates of shell carbonate construction (in excess of 35 g in the first year of life) likely depended on habitats conducive to calcification. Late Miocene cooling and eastern Pacific carbonate limitation are implicated in the range contraction and eventual extinction of this species.
We present a critical evaluation of the taxonomy, stratigraphy and biogeography of the turritellid gastropods of the Miocene Paratethys Sea. 159 species-level names and 6 infrasubspecific names have been used for Paratethyan Turritellidae since 1848. Of these, only 35 species are accepted herein as valid species, with some uncertainties due to poor preservation or limited access to type material. Maximum diversities occurred during the early middle Miocene (Langhian, Badenian) coinciding with the Miocene Climatic Optimum. Whilst early Miocene turritellid assemblages are characterized by large
to very large species of Peyrotia, Turritella and Allmonia, middle Miocene assemblages are predominated by mediumsized species of Archimediella, Helminthia, Oligodia and Ptychidia. The taxonomic composition of these faunas, with representatives of Archimediella, Helminthia, Mesalia and Vermicularia suggests a biogeographic affiliation with Atlantic and especially West African faunas.
Turritellinella new gen. is established as new genus for the eastern Atlantic-Mediterranean Turritella tricarinata/communis complex. Viennella is described as new genus with Turritella incisaeformis Csepreghy-Meznerics 1956 as type species. Allmonia new gen. is introduced as new genus for European Cenozoic Protominae previously placed in Protoma.
For the first time, inner lirae are documented as conchological features of Turritellidae.
Six species are described as new, three within the Turritellinae: Archimediella carpathica new sp., Ptychidia erynella new sp. and Viennella ignorata new sp., and three within the Pareorinae: Mesalia sovisi new sp., Mesalia stryriaca new sp. and Mesalia bohnhavasae new sp.. Ptychidia austrorotundata new nom. is proposed as new name Turritella
turris rotundata Schaffer 1912, non Turritella rotundata Grzybowski 1899. We designate lectotypes for Turritella gradata Menke in Hörnes, 1855, Haustator striatellatus Sacco, 1895, Allmonia carniolica (Stache, 1858) and Allmonia alterniplicata (Sacco, 1895). Neotypes are designated for Archimediella abundans (Handmann, 1882), Archimediella hoernesi (Rolle, 1856), Ptychidia partschi (Rolle, 1856), Ptychidia? ernesti (Handmann, 1882). Rhabdosis Townes, 1970 (Hymenoptera, Ichneumonidae) is a junior homonym of Rhabdosis Handmann 1882 (Gastropoda, Turritellidae) and will need a new name.
Plio-Pleistocene mass extinction of marine bivalves on the U.S. eastern seaboard has been attributed to declines in temperature and primary production. We investigate the relationship of growth rate in the scallop Carolinapecten eboreus to variation in these parameters to determine which contributed to its extinction. We use ontogenetic profiles of shell δ ¹⁸ O to estimate growth rate and seasonal temperature, microgrowth-increment data to validate δ ¹⁸ O-based figures for growth rate, and shell δ ¹³ C to supplement assemblage evidence of production. Postlarval growth started in the spring/summer in individuals from the Middle Atlantic Coastal Plain but in the autumn/ winter in some from the Gulf Coastal Plain. Growth rate typically declined with age and was usually higher in summer than winter. Many individuals died in winter but the largest forms typically died in spring, possibly on spawning for the first time. No individuals lived longer than two years and some grew exceedingly fast overall, up to 60% more rapidly than any other scallop species (, 145.7 mm in a year). Faster growth was generally achieved by secreting more rather than larger microgrowth increments. Some very fast-growing individuals lived in settings of high production and low temperature. No individuals grew slowly under high production whereas most if not all grew slowly under 'average' production and low temperature. In that the rapid growth evidently enabled by high production would have afforded protection from predators, Plio-Pleistocene decline in production was probably contributory to the extinction of C. eboreus. However, the negative impact of low temperature on growth under 'average' production suggests that temperature decline played some part.
The rich fossil record of the Atlantic and Gulf coastal plains of the United States is a gold mine for interested scientists. The last thirty million years of Earth history are superbly chronicled by a succession of fossil assemblages extending from the St. Lawrence River to Florida. Marine scientists, paleontologists, and systematic biologists alike need a thorough guide to interpret this history. Cenozoic Seas: The View from Eastern North America analyzes the changing geography, the arrival and departures of ecosystems and species, and the affect of climate on living things. The author classifies all of the region's fossil-bearing formations and their contents within a logical, descriptive framework of space and time, providing a clear path for those studying evolution and extinction within specific communities of organisms. The book is also an excellent field guide for fossil collectors, providing detailed information for all species illustrated. Many organisms have never before been illustrated in a book on fossil shells.
Studies on drilling predation in the fossil record often analyze site stereotypy and drilling frequency. Postmortem prey shell breakage can create particular problems for these analyses, especially in high-spired gastropods (e.g., normalizing drill hole location and estimating the number of individuals in a sample). As a result, many previous studies of these taxa have considered only “complete specimens” though “completeness” is rarely well defined, thereby frequently excluding much potential data. We applied two approaches to collect predation data from incomplete shells of Turritella alumensis from the Pliocene Jackson Bluff Formation in Florida. First, we studied site stereotypy using a Theoretical Apex System to normalize drill hole location. Including incomplete specimens revealed a different pattern of site stereotypy than some previous authors have noted: we found two potential populations of drillers acting on different portions of the shells. Second, we calculated drilling frequency by creating a new calculation for normalizing the minimum number of individuals of high-spired gastropods within a sample, making it possible to compare samples with variable amounts of shell breakage. The calculated drilling frequency for shells drilled by larger predators generated using this method was consistent with that calculated using only “complete” specimens. Additional studies are needed to determine whether drilling frequencies calculated using “complete” specimens are always consistent with those generated using the minimum number of individuals method introduced here.
Turritelline-dominated assemblages (TDAs) frequently occur in the middle-late Miocene Gatun Formation, and are not uncommon features in the broader fossil record. By gaining a better understanding of the paleoenvironment and taphonomic processes leading to their formation we can gain insight into the conditions in the Western Atlantic (WA) during the Miocene shoaling of the Central American Seaway, as well as the conditions which may lead to TDA formation generally. TDA and non-TDA beds within the Gatun were examined for shell orientation, sclerobiont coverage, drilling predation frequency and site stereotypy, and sediment composition. The most abundant species, T. altilira, was also examined using oxygen isotopic sclerochronology to compare growth rate and environmental conditions during the formation of TDA and non-TDA beds. Mean annual range of temperature (MART) was found to be 6.2 °C, with a moderate associated negative O-C correlation. These data confirm the influence of Tropical Eastern Pacific (TEP) upwelling waters in the WA at this time. Upwelling conditions were found to be associated with all T. altilira, regardless of their source, indicating that Gatun TDAs are not the result of variation in nutrient supply. Orientation data from within a TDA, grain size, and sclerobiont coverage all suggest that TDAs in the Gatun are the result of variation in sediment supply/winnowing. We used the Theoretical Apex System and a calculated minimum number of individuals to determine that the frequency of drilling predation and site stereotypy within and without TDAs was statistically indistinguishable. T. altilira was found to live up to 3 years, growing between 50 and 60 mm in the first year of life with a subsequent decline in growth rate.
We use the trace-fossil record left by the shell-drilling and crushing predators of marine mollusks to investigate the paleoecology of mass extinction. The pulsed extinction of mollusks during the Plio-Pleistocene, in the Western Atlantic, was part of a dramatic faunal turnover coinciding with a decrease in relative abundance of predatory gastropods and an overall relaxation of competition in the predatory milieu. We test the hypothesis that these changes affected the coupled strength and outcome of predator-prey interactions—including those involving the myriad shell-crushing predators in marine food webs, utilizing repaired shell damage and drill holes on five common, or bellwether, prey: Anadara, Cyclocardia, Glycymeris, Plicatula, and Olivella. Predation and abundance data were collected from bulk samples (> 5mm fraction), comprising one late Pliocene (Duplin Formation), one early Pleistocene and two middle Pleistocene (Waccamaw Formation) age localities from southeastern North Carolina, USA. The results do not support our hypothesis because there was no unambiguous change in the frequency of repair scars on any of the bellwether prey taxa. The significant difference in Glycymeris repairs per shell (p < 0.001) is equivocal due to any one of the morphological, ecological, or methodological complications of species comparisons. There is also no change in the frequency of complete, countersunk drill holes between the Plio-Pleistocene time intervals. A range of biases can subtly affect estimates of fossil predation; left-right valve sorting and destruction of shells by predators may have been active biases here. The presence or absence of edge-drill holes in assemblages across the Western Atlantic suggests predator-prey interactions varied locally. The reported decline of predatory gastropod abundance was not recovered in a subset of previously studied samples. These results support the interpretation that changes in taxonomic composition and predatory interactions were decoupled in ancient communities.
John Fleming (1785-1857) was a minister of the Church of Scotland, but in his time at the University of Edinburgh he had also studied geology and zoology. In the tradition of the country parson who was also a talented and knowledgeable naturalist, he published his first works on the geology of the Shetland Islands while serving there as a minister. His subsequent works led to his being offered the chair of natural philosophy at the University of Aberdeen, and subsequently at the newly created chair of natural history at the Free Church College in Edinburgh. The two-volume Philosophy of Zoology was published in 1822, and the young Charles Darwin is recorded as borrowing it from the library of Edinburgh University in 1825/6. His intention in the book was to ‘collect the truths of Zoology within a small compass, and to render them more intelligible, by a systematical arrangement’.
This analysis examines the evolution of the greater diversity of species with non-planktonic larval types relative to species with planktonic larval types in the turritellid gastropods. Two mechanisms for generating diversity gradients in larval types have been proposed in the literature: species selection and factors in development that are mediated by organismal adaptation. In order to examine the relevance of these two proposed mechanisms, a phylogenetic analysis of the turritellids using molecular phylogeny suggests that species selection is not the only process driving the trend toward increasing numbers of non-planktonic species through time. Developmental processes, apart from those involving organismal adaptation are implicated as playing a role in this trend. -from Authors
The Florida Platform is delimited by the 200 m (600 ft) isobath at the shelf break to the approximate location of the Paleozoic suture beneath southern Georgia and Alabama (Fig. 2.1). The Suwannee-Wiggins Suture (Thomas et al. 1989) is the proposed location where terranes with African affinities are welded to the North American Plate (Chowns and Williams 1983; McBride and Nelson 1988; Woods et al. 1991). The basement rocks of the Florida Platform are a fragment of the African Plate that remained attached to the North American Plate when rifting occurred in the Jurassic and range in age from late Precambrian-early Cambrian to mid-Jurassic (Barnett 1975). Excellent reviews of the geology of the basement are provided by Smith (1982), Arthur (1988), Smith and Lord (1997), and Heatherington and Mueller (1997). Barnett (1975) provided a structure contour map of the sub-Zuni surface. This surface equates to what is now recognized as pre-Middle Jurassic. Barnett's interpretation of the basement surface has it occurring as shallow as approximately 915 m (3000 ft) below mean sea level (msl) in central-northern peninsular Florida. The basement surface dips west and southwest toward the Gulf of Mexico basin, to the south into the South Florida basin, and to the east into the Atlantic basin. The basement surface reaches depths of more than 5180 m (17,000 ft) below msl in southern Florida (Barnett 1975).
Conus (or cone) shells are common in many Pliocene and Pleistocene fossil deposits from the Coastal Plain of the southeastern United States, but have never been the subjects of a comprehensive taxonomic review or revision. In total, 84 names (including those of some Recent species and fossil taxa from other strata or areas) have been applied to Plio-Pleistocene cone shells from this region, and since Green described Conus marylandicus in 1830, an additional 59 species have been described from these strata. Forty of these taxa were described in the last 17 years and were published outside of the peer-reviewed literature, making their status as distinct species suspect, particularly because most are poorly illustrated, perfunctorily described, and based on few specimens. This makes them nearly impossible to evaluate without direct inspection of type material and/or access to large suites of specimens. Evaluating whether these suspect taxon names represent distinctive morphospecies is critical to attaining an understanding of the evolutionary history and diversity of Neogene and Recent Conus in the western Atlantic. The present work provides a systematic treatment of 82 of the 84 names that have been applied to Conus shells from the PlioPleistocene fossil records of Virginia, North Carolina, South Carolina, and Florida. Here, through application of a conservative morphological species concept (one that accepts large amounts of intraspecific morphological variation), 19 of these nominal taxa are accepted as representing distinctive species of Plio-Pleistocene Conus from this study area. In addition, this investigation also resulted in the discovery of one new fossil morphospecies, described here as Conus burnetti n. sp. An identification key to these 20 species is provided. The status of three additional, previously described species (known only by their type specimens) remains less certain. Two names that are likely familiar to collectors of Plio-Pleistocene Conus from the United States Coastal Plain, C. floridanus Gabb, 1869, and C druidi Olsson, 1967, are synonymized, respectively, with C cf. largillierti Kiener, 1845, and C haytensis G.B. Sowerby II, 1850. All previously described species of sinistral Conus are considered to belong to one highly morphologically variable species, C adversarius Conrad, 1840.
Pliocene and Pleistocene marine deposits of southern Florida include the Tamiami, Caloosahatchee, Bermont, Ft. Thompson, and Coffee Mill Hammock formations. Eight species of Latirus from three of these deposits are described and illustrated. Lantirus (Latirus) nosali new species and L. (Polygona) miamiensis Petuch, 1986, occur in the middle Pliocene Pinecrest facies of the Tamiami Formation; L. (L .) stephensae new species, L. (P.) hypsipettus Dall, 1890 (synonym: L. tessellatus seminolensis M. Smith, 1936), and L . (P.) caloosahatchiensis new name for L . tessellatus Dall, 1890, non Récluz, 1844, nec Kobelt, 1874, occur in the late Pliocene Caloosahatchee Formation; and L. (L.) cariniferus (Lamarck, 1816), L. (P.) maxwelli Pilsbry , 1939, and L. (P.) jucundus McGinty, 1940, occur in the early Pleistocene Bennont Formation. No species of Latirus is known from the late Pleistocene Ft. Thompson or Coffee Mill Hammock formations. The Florida fossils are compared with 9 late Miocene to Pleistocene species from the Caribbean Basin and with 11 species in the Recent fauna of Florida and the Caribbean Sea. Of the four Recent species of Latirus that occur in Florida, only one also occurs in Florida Pleistocene deposits, but three, and possibly all four, are known as Pleistocene fossils in the Caribbean Basin.
The most significant change in Pliocene oceanic circulation resulted from closure of the Tropical American Seaway between the Caribbean Sea and Eastern Pacific Ocean around 3 Ma. Faunal changes in Caribbean shallow-water marine organisms such as mollusks and corals have been attributed to possible environmental changes associated with this event, including cyclical cooling, initiation of a carbonate regime in the southern Caribbean, and upwelling of deeper waters on the continental shelf, but their occurrences and timing have been unclear.
This study uses the ecological and evolutionary record of benthic foraminifera of the upper continental slope to inner continental shelf to investigate environmental change in Caribbean shallow waters with respect to final closure of the interoceanic seaway. Benthic foraminifera are useful as environmental indicators so periods of increased taxonomic turnover should correspond to times of environmental change. Over 100 species commonly occurring in deposits of Caribbean Panama and Costa Rica dated from 6.5 to 1.6 m.y. were taxonomically standardized with existing literature and collections to produce stratigraphic ranges within the Caribbean region.
Although an average common species has lived from Early Miocene times until today, an increase in first appearances suggests that an interval of ecological restructuring occurred on the continental shelf to upper slope in latest Miocene time. The last 15 m.y. includes about 45% of the first and last appearances, 70% of which are comparably dated in other Caribbean strata. For the period from 15 to 3 Ma, about 75% of first appearances occurred between 7 and 3 Ma, and more than twice as many occurred between 7 and 5 Ma as occurred before or after that interval. Comparable numbers of continental shelf and slope taxa have first occurrences between 7 and 5 Ma, indicating a general change on the continental shelf to upper slope in the latest Miocene which preceded closure of the interoceanic seaway by 2 to 4 m.y. Few extinctions occurred in the last 7 m.y.; 86% of the common taxa less than 7 m.y. old in Panama and Costa Rica have survived to the present. The appearance of carbonate-loving species in Panama to Costa Rica at 4.6–5.0 Ma and northern Colombia by 5.0 Ma indicates a well established carbonate regime in the southern Caribbean by earliest Pliocene time. Benthic foraminiferal assemblages show no evidence of upwelling in the Panama-Costa Rican region through the Pliocene.
The Late Miocene environmental changes in shallow Caribbean waters preceded isotopic changes in open-ocean surface waters that occurred 4 to 3 Ma. Ecological restructuring took place in the latest Miocene, several m.y. before the seaway closed, and any subsequent environmental changes had little effect on benthic foraminifera of the Caribbean continental shelf.
— We studied sequence variation in 16S rDNA in 204 individuals from 37 populations of the land snail Candidula unifasciata (Poiret 1801) across the core species range in France, Switzerland, and Germany. Phylogeographic, nested clade, and coalescence analyses were used to elucidate the species evolutionary history. The study revealed the presence of two major evolutionary lineages that evolved in separate refuges in southeast France as result of previous fragmentation during the Pleistocene. Applying a recent extension of the nested clade analysis (Templeton 2001), we inferred that range expansions along river valleys in independent corridors to the north led eventually to a secondary contact zone of the major clades around the Geneva Basin. There is evidence supporting the idea that the formation of the secondary contact zone and the colonization of Germany might be postglacial events. The phylogeographic history inferred for C. unifasciata differs from general biogeographic patterns of postglacial colonization previously identified for other taxa, and it might represent a common model for species with restricted dispersal.
