THE FOSSIL GREEN ALGA MIZZIA (DASYCLADACEAE): A TOOL FOR INTERPRETATION OF PALEOENVIRONMENT IN THE UPPER PERMIAN CAPITAN REEF COMPLEX SOUTHEASTERN NEW MEXICO1

A paleoenvironmental study of the dasyclad Mizzia Schubert, 1907 is potentially important because, unlike most of the other fossil reef-dwelling organisms found in the Guadalupe Mountains, the fossil Mizzia (restricted to the Permian) has a modern analog, Cymopolia Lamouroux, 1916 (Cretaceous to Holocene). The overall morphology of the two genera is similar: both are articulated, and observations on our specimens suggest that both were branched. The transition from the remarkably high-diversity sponge and algal assemblage in the reef into the remarkably low-diversity dasyclad-dominated assemblage in the back reef is abrupt, occurring over distances as short as 10 m. Mizzia is the dominant and usually the only component in grainstones, packstones, and wackestones found; immediately shelfward of the Capitan reef. The low percentage of broken segments (average 10%) and the discovery of several intact sections of thallus are evidence against wave action as a possible limiting factor. Because the climate in the Guadalupe Mountains was extremely arid and because dasyclads are euryhaline, hypersalinity is considered the most likely limiting factor in this case. Our conclusion that prolific stands of dasyclads formed in shallow protected lagoons immediately behind an emergent barrier reef is not compatible with the currently accepted marginal mound hypothesis for deposition of the Capitan reef complex. We suggest that the marginal mound model must either be modified or abandoned in favor of the originally proposed barrier reef model of deposition.     

EVOLUTION OF THE CASUARINACEAE: MORPHOLOGICAL COMPARISONS OF SOME EXTANT SPECIES

The Casuarinaceae consists of the 4 genera Gymnostoma, Ceuthostoma, Casuarina and Allocasuarina. All the genera are found living today in Australia, Malaysia, Melanesia, and Southeast Asia. An abundant and widespread fossil record of the genus Gymnostoma is known from New Zealand, Argentina, South Africa, and Australia. This paper provides a compilation of basic vegetative and reproductive morphological data of the 4 genera of the Casuarinaceae with special emphasis on these features in Gymnostoma. The features are presented in tabular form and the data are compared and discussed. Most of the genera can be clearly distinguished by the morphology of their vegetative and reproductive organs. Species differences within the extant genera often are difficult to distinguish; therefore, comparative systematic analysis of these fossils from fragmentary and incomplete remains ranging through time will be very difficult, and care must be taken when interpreting evolutionary trends from them.     

MUSOPSIS N. GEN.: A BANANA-LIKE LEAF GENUS FROM THE EARLY TERTIARY OF EASTERN NORTH GREENLAND

A fossil flora from the Late Paleocene-Early Eocene Thyra Ø Formation of eastern North Greenland (paleolatitude 77° N) has yielded monocotyledon leaf impressions with characters seen only in the closely related modem species in the families of Heliconiaceae, Musaceae, and Strelitziaceae. The combination of large costae widths and parallel, nonanastomosing, lateral veins that depart at right angles from the costae in the fossil material are features present only in leaves of extant species from these families. Three basic venation patterns also are recognized in the modem species of these families, but except for the genera Strelitzia and Phenakospermum, none of these patterns are present exclusively in any one family. Musopsis n. gen. is created for the fossil material from Greenland, but it is considered a form genus due to the lack of gross morphological features that can be used for separating leaves of the modem genera in Heliconiaceae, Musaceae, and Strelitiziaceae. It is the first known Arctic occurrence of fossil leaf material resembling this modem group of taxa.     

Approaches to the identification of angiosperm leaf remains

During the past 125 years the history of early angiosperms, interpreted through the fossil leaf record has been largely an exercise in paleofloristic studies, ignoring evolution. Imprecise identifications of ancient leaves “matched” to extant genera and families have been used as the basis for reconstructions of paleocommunities and paleoclimates. However, as the result of careful morphological studies of leaf form, venation and cuticular features new insights into the evolution of angiosperms are now available. In this paper considerations are given to the usefulness and shortcomings of leaf form, venation and cuticular analysis as diagnostic tools of plant identification. Many techniques for the study of the morphology of modern and fossil leaves are included in this paper as well as tables outlining features of leaf venation and the epidermis. Careful morphological studies of leaf form (such as the venation and epidermal characters emphasized in this paper) will provide better understanding of the relationships of living angiosperms and transform the fossil leaf record into useful data that can be used to study the evolution of the angiosperms.     

Fossils and living taxa agree on patterns of body mass evolution: a case study with Afrotheria

Most of life is extinct, so incorporating some fossil evidence into analyses of macroevolution is typically seen as necessary to understand the diversification of life and patterns of morphological evolution. Here we test the effects of inclusion of fossils in a study of the body size evolution of afrotherian mammals, a clade that includes the elephants, sea cows and elephant shrews. We find that the inclusion of fossil tips has little impact on analyses of body mass evolution; from a small ancestral size (approx. 100 g), there is a shift in rate and an increase in mass leading to the larger-bodied Paenungulata and Tubulidentata, regardless of whether fossils are included or excluded from analyses. For Afrotheria, the inclusion of fossils and morphological character data affect phylogenetic topology, but these differences have little impact upon patterns of body mass evolution and these body mass evolutionary patterns are consistent with the fossil record. The largest differences between our analyses result from the evolutionary model, not the addition of fossils. For some clades, extant-only analyses may be reliable to reconstruct body mass evolution, but the addition of fossils and careful model selection is likely to increase confidence and accuracy of reconstructed macroevolutionary patterns.     

The relevance of zoological variation studies to the generic identification of fossil brachiopods

Two disturbing trends are seen in current thinking behind the establishment of new genera of fossil brachiopods; the emphasis on their applications stratigraphi-cally, and the use of progressively finer distinctions in diagnoses. The genus is a biologically based concept and thus fossil genera are only justifiable if the basis of their establishment is also biological; any stratigraphical applications are merely a by-product. The use of finer morphological distinctions in the establishment of fossil brachiopod genera in recent years runs contrary to the findings of field zoologists working on modern marine shells. Examples of the wide morphological variation in modern shells, apparently phenotypically induced, are given, the importance of this work in keeping the genus concept of the palaeontologist in perspective is stressed, and a revision of the established taxonomy of the triple-siacean Onychotreta undertaken as an illustration.     

Diversity of Mesozoic gnetophytes and the first angiosperms

A provisionary system of gnetophytes is proposed, including recently discovered Mesozoic members. The following principal characters are used, in descending order of significance: strobilar structure of ovulate organs (eugnetophytes) as opposed to flowerlike cupules and their aggregates (anthognetophytes), radial vs. bilateral symmetry of seed cupules, and morphological distinctions in the pollen organs, pollen micromorphology and exine ultrastructure. The fossil members show mosaic associations of morphological traits, which attests to different evolution rates of their ovulate and pollinate structures. The system includes two superorders and eight orders, several of which are new. A dichotomous key is provided to differentiate between genera of fossil gnetophytes based on ovulate structures. Two stages in evolution of gnetophyte morphological diversity are recognized: first in the Triassic and then in the Early Cretaceous, the latter was associated with the origin of new type herbaceous wetland communities. Angiosperms or some of them might have originated as elements of gnetophyte diversity in such communities.     

Mesozoic conifers

The Coniferophyta attained their greatest diversity and abundance during the Mesozoic Era. Many early forms died out without apparent involvement in the evolution of the modern types. Yet, all living coniferophyte families and a surprising number of their present-day genera are clearly in evidence in the Mesozoic. Generally, modern families are recognizable by the Late Triassic or Early Jurassic while certain contemporary genera make their appearance as early as the Middle Jurassic. The Pinaceae appears to lag behind other families in that it lacks unequivocal representation before the onset of the Cretaceous although certain Late Triassic and Jurassic remains may belong to the family. Modern coniferophyte families appear to have originated somewhat earlier than was formerly believed and this brings to light problems in envisioning their evolution from the known Voltziales. Seed cones of certain of the latter are now known from petrified material which show a greater modification than was formerly known. Various kinds of detached organs that cannot be assigned to existing families are described and discussed and the bearing of the fossil record in certain questions on coniferophyte systematics is evaluated.     

Phylogeny of the North American catfish family Ictaluridae (Teleostei: Siluriformes) combining morphology,genes and fossils

We performed the first combined‐data phylogenetic analysis of ictalurids including most living and fossil species. We sampled 56 extant species and 16 fossil species representing outgroups, the seven living genera, and the extinct genus ?Astephus long thought to be an ictalurid. In total, 209 morphological characters were curated and illustrated in MorphoBank from published and original work, and standardized using reductive coding. Molecular sequences harvested from GenBank for one nuclear and four mitochondrial genes were combined with the morphological data for total evidence analysis. Parsimony analysis recovers a crown clade Ictaluridae composed of seven living genera and numerous extinct species. The oldest ictalurid fossils are the Late Eocene members of Ameiurus and Ictalurus. The fossil clade ?Astephus placed outside of Ictaluridae and not as its sister taxon. Previous morphological phylogenetic studies of Ictaluridae hypothesized convergent evolution of troglobitic features among the subterranean species. In contrast, we found morphological evidence to support a single clade of the four troglobitic species, the sister taxon of all ictalurids. This result holds whether fossils are included or not. Some previously published clock‐based age estimates closely approximate our minimum ages of clades.     

The systematic relationships of glucosinolate-producing plants and related families: a cladistic investigation based on morphological and molecular characters

A cladistic analysis is performed using 94 morphological and biochemical characters for 42 genera to compare a phylogeny based on morphological data with those obtained using different genes ( rbc L, atp B, 18S RNA, mat K) or their combination with morphological data, and to understand the floral evolution within the expanded Brassicales (Capparales) relative to Sapindales and Malvales. The tree produced with morphological data is congruent with those obtained from macromolecular studies in obtaining a well-supported glucosinolate-producing clade and an expanded Sapindales. The combined analysis of the morphological and molecular characters is generally well resolved with support for many of the relationships. The inclusion of the fossil taxon Dressiantha demonstrates the value of inserting fossil evidence in phylogenetic analyses. However, the fossil appears to be related to the Anacardiaceae and not to the Brassicales. The core Brassicales are well supported by a number of synapomorphies, although the internal position of Tovariaceae and Pentadiplandraceae is not well resolved. Emblingiaceae appears to be related to Bataceae and Salvadoraceae. Several significant morphological characters are mapped on the combined trees and their evolutionary significance is discussed. Within Brassicales and Sapindales several well supported clades can be recognized which merit ordinal or subordinal status, putting the present orders at a higher level; these include: Tropaeolales, Setchellanthales, Batidales, Brassicales (Brassiciflorae), Burserales, Sapindales and Rutales (Sapindiflorae). The present scheme of affinities within the Brassicales corresponds well with a gradual morphological evolution in the order.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 453–494.     

A newly recognized fossil coelacanth highlights the early morphological diversification of the clade

Previously considered an actinopterygian or an osteichthyan incertae sedis, the Devonian (Givetian-Frasnian) Holopterygius nudus is reinterpreted as a coelacanth. This genus is among the oldest coelacanths known from articulated remains, but its eel-like morphology marks a considerable departure from the conventional coelacanth body plan. A cladistic analysis places Holopterygius as the sister taxon of the Carboniferous (Serpukhovian) genus Allenypterus. Despite the specialized morphology of these genera, they occupy a surprisingly basal position in coelacanth phylogeny; only Diplocercides and Miguashaia are further removed from the crown. A morphometric analysis reveals that coelacanths were anatomically disparate early in their history. Conflicts between this result and those of previous studies challenge the adequacy of systematic character sets for describing historical patterns of morphological variety. Coelacanths have long had an iconic place in the study of vertebrate evolution for their apparent anatomical conservatism over geological time, but Holopterygius provides clear evidence for rapid morphological evolution early in the history of this clade.     

Comparative study on ovarian structures in scorpaenids: possible evolutional process of reproductive mode

The reproductive modes of the Scorpaenidae are extremely varied: oviparity, viviparity, and even spawning of internally fertilized eggs or embryos (zygoparity or embryoparity), as in Helicolenus, are known. The ovarian structure of this family is divided into two types by the arrangement of the stroma and the ovarian cavity. One type is the ovary in which the lamella-like stroma develops from the ovarian hilus located on the dorsal side and where the ovarian cavity is located on the ventral side of ovary, classified as “cystovarian type II-1” by Takano (1989). In the other type, the stroma in the ovary develops radially around the blood circulatory system that traverses the center of the ovary, and then the ovarian cavity surrounds all the ovary, classified as “cystovarian type II-3” by Takano (1989). In the present analysis, previous reports about ovarian structure and the relationship to the reproductive mode of scorpaenids were described, and the ovarian structure of eight genera of Scorpaenidae was examined. The ovary of cystovarian type II-1 is seen only in viviparous genera and is not seen in oviparous genera. However, the cystovarian type II-1 is a general structure in other families of Scorpaeniformes, and this structure could be considered a primitive type of ovary rather than that acquired by the process of evolution from oviparity to viviparity. The ovary of cystovarian type II-3 is seen in all six oviparous genera and the one zygoparous genus examined. The ovary of this type is not found in any other family of teleosts, so it could be a structure originally divided in Scorpaenidae. In the genera having the cystovarian type II-3 ovary, there is a common feature of spawning: a floating egg mass encompassed by the gelatinous material. We postulate that the evolution of reproductive mode in the scorpaenid fishes is as follows: Sebastes and Sebastiscus have a primitive ovary in which viviparity has developed, whereas the genera that spawn a floating egg mass evolved the ovarian structure from primitive type to cystovarian type II-3, and further zygoparity, such as in Helicolenus, evolved from them.     

Extant‐only comparative methods fail to recover the disparity preserved in the bird fossil record

Most extant species are in clades with poor fossil records, and recent studies of comparative methods show they have low power to infer even highly simplified models of trait evolution without fossil data. Birds are a well‐studied radiation, yet their early evolutionary patterns are still contentious. The fossil record suggests that birds underwent a rapid ecological radiation after the end‐Cretaceous mass extinction, and several smaller, subsequent radiations. This hypothesized series of repeated radiations from fossil data is difficult to test using extant data alone. By uniting morphological and phylogenetic data on 604 extant genera of birds with morphological data on 58 species of extinct birds from 50 million years ago, the “halfway point” of avian evolution, I have been able to test how well extant‐only methods predict the diversity of fossil forms. All extant‐only methods underestimate the disparity, although the ratio of within‐ to between‐clade disparity does suggest high early rates. The failure of standard models to predict high early disparity suggests that recent radiations are obscuring deep time patterns in the evolution of birds. Metrics from different models can be used in conjunction to provide more valuable insights than simply finding the model with the highest relative fit.     

PHYLOGENY OF THE DASYCLADALES (CHLOROPHYTA,ULVOPHYCEAE) BASED ON ANALYSES OF RUBISCO LARGE SUBUNIT (rbcL) GENE SEQUENCES1

The phylogeny of the green algal Order Dasycladales was inferred by maximum parsimony and Bayesian analyses of chloroplast‐encoded rbcL sequence data. Bayesian analysis suggested that the tribe Acetabularieae is monophyletic but that some genera within the tribe, such as Acetabularia Lamouroux and Polyphysa Lamouroux, are not. Bayesian analysis placed Halicoryne Harvey as the sister group of the Acetabularieae, a result consistent with limited fossil evidence and monophyly of the family Acetabulariaceae but was not supported by significant posterior probability. Bayesian analysis further suggested that the family Dasycladaceae is a paraphyletic assemblage at the base of the Dasycladales radiation, casting doubt on the current family‐level classification. The genus Cymopolia Lamouroux was inferred to be the basal‐most dasycladalean genus, which is also consistent with limited fossil evidence. Unweighted parsimony analyses provided similar results but primarily differed by the sister relationship between Halicoryne Lamouroux and Bornetella Munier‐Chalmas, thus supporting the monophyly of neither the families Acetabulariaceae nor Dasycladaceae. This result, however, was supported by low bootstrap values. Low transition‐to‐transversion ratios, potential loss of phylogenetic signal in third codon positions, and the 550 million year old Dasycladalean lineage suggest that dasyclad rbcL sequences may be saturated due to deep time divergences. Such factors may have contributed to inaccurate reconstruction of phylogeny, particularly with respect to potential inconsistency of parsimony analyses. Regardless, strongly negative g₁ values were obtained in analyses including all codon positions, indicating the presence of considerable phylogenetic signal in dasyclad rbcL sequence data. Morphological features relevant to the separation of taxa within the Dasycladales and the possible effects of extinction on phylogeny reconstruction are discussed relative to the inferred phylogenies.     

Revisiting taxonomy, morphological evolution, and fossil calibration strategies in Chloranthaceae

Chtoranthaceae is one of the earliest diverging angiosperm families and is comprised of approximately 75 species in four genera (Chloranthus,Sarcandra,Ascarina,and Hedyosmurn).This family has received considerable attention because of its seemingly primitive morphology,disjunct tropical distribution in Asia and America,and extensive fossil record from the Early Cretaceous.In the present study,we reconstructed the phylogeny of Chloranthaceae based on a combined dataset of three plastid DNA regions and 56 species.We then estimated divergence times in the family using two relaxed molecular clock methods (BEAST and penalized likelihood).We focused on testing the influence of fossil taxa in calibrating the molecular phylogeny,and on assessing the current taxonomy of the family in light of the phylogenetic results.Our results indicate that most intrageneric divisions within Ascarina and Hedyosmum are not monophyletic.The results from the dating analysis suggest that the Hedyosmum-like fossil Asteropollis represents a stem lineage of Hedyosmum,as has been suggested previously from morphological analyses.In contrast,our results indicate that the Chloranthus-like fossil Chloranthistemon,previously suggested on morphological grounds to be a stem relative of Chloranthus,may,instead,belong to the branch leading to the clade Chloranthus + Sarcandra.The median crown ages of Chloranthus,Sarcandra,Ascarina,and Hedyosmum estimated in the BEAST analysis were 26.3,9.5,31.0 and 45.8 million years ago (Ma),respectively,whereas the divergence between Chloranthus and Sarcandra,the splitting of Ascarina with the former two genera,and Hedyosmum separating from the three genera were estimated to 63.8,95.7 and 111.1 Ma.The present study sheds further light on the temporal evolution of Chloranthaceae and exemplifies how molecular dating analyses may be used to explore alternative phylogenetic placements of fossil taxa.     

ANGIOSPERM PALEOBIOCHEMISTRY OF THE SUCCOR CREEK FLORA (MIOCENE) OREGON,USA

The organic chemical profiles of fossil Acer and Quercus leaf tissues are presented and correlated with those of previously described fossil Celtis, Ulmus and Zelkova and interpreted in conjunction with referable extant genera. Intrageneric comparisons among fossil and extant taxa indicate that relatively minor phytochemical differences exist suggesting that little flavonoid and steroid evolution since post-Miocene times has occurred. Biosystematic relationships between living North American and Asian genera indicate that in some cases (Quercus, Zelkova) a greater affinity exists between living Asiatic species and elements of the Succor Creek Flora. The chemical data are proposed as an independent parameter in assessing angiosperm biogeography and proposed migration patterns of the Fagaceae and Ulmaceae. The high chemical fidelity seen between some living and fossil genera preserved in ash-fall deposits is ascribed to the reaction of membrane bound lipids with various organic acids and to subsequent rapid dehydration.     

Phylogeny, speciation and species turnover. The case of the Mediterranean gastropods of genus Cyclope Risso, 1826

The genus Cyclope Risso, 1826 (family Nassariidae) has appeared in the fossil record since the Pliocene. Although it is still found today, the teleoconch morphology has never undergone modification, despite the fact that the protoconch morphologies of fossils (multispiral) and living forms (paucispiral) are different. They vary in their embryological and larval development and, hence, are two different species: C. migliorinii (Bevilacqua, 1928), the fossil species, and C. neritea (Linnaeus, 1758), the living species. We discuss the morphologic modifications in the evolution of this genus: the speciation that leads to its appearance and the speciation driving the Pliocene species to the living one. The order and the direction of these changes are based on phylogenetic analysis. No intermediate forms have been found showing a gradual morphological change that could have been worked by natural selection. Our analysis takes as the origin of the morphological novelties the genetic modifications in the ontogenetic processes which resulted in rapid and important phenotypic changes. Both speciation processes are sympatric cladogenetic. The changes that determine the appearance of the genus affect only the teleoconch, not the larval development. The modifications that lead from one species to the other, within the genus Cycope, affect the larval development exclusively. This points to a certain disconnection between the development of the embryo-larval phase and the young-adult formation, such that evolutionary processes could have occurred independently in different ontogenetic stages. The influence of larval ecology in relation to extinction of the ancestor and persistence of the derived species is also analysed. We hypothesize that climatic fluctuations may have affected the planktonic larvae of the fossil species, driving it to extinction. The living species, developing without the planktonic phase, would have resisted these climatic changes. We consider that the mechanisms described as drivers of the evolution of this genus can be of more general validity in prosobranch gastropods.     

Phylogeny of the snailfishes (Teleostei: Liparidae) based on molecular and morphological data

Liparidae (snailfishes) is one of the most diverse and abundant fish families in polar and deep-sea habitats. However, the evolution of this family is poorly known because of the rarity of many species and difficulties in scoring morphological characters. We perform phylogenetic analyses of Liparidae using sequences from two mtDNA genes, 16S (585 bp) and cytochrome b (426 bp), and 84 morphological characters from 24 species of Liparidae and 4 species of Cyclopteridae (outgroup). The present study confirms earlier hypotheses that the shallow-water genera, such as Liparis and Crystallichthys, occupy basal positions and that deep-water genera, such as Careproctus, Elassodiscus, Rhinoliparis, Paraliparis, Rhodichthys and Psednos, are increasingly derived. The later two genera form a terminal clade which does not include Paraliparis. The topology shows that the family has undergone a reductive type of evolution, with a gradual loss of characters (e.g. sucking disc/pelvic fins, pseudobranchial filaments, skin spinules). Nectoliparis, which had previously been placed either as the basal most genus or among the most derived genera, are found to occupy the most basal position among the taxa analyzed. This result indicates that the sucking disc has been lost at least twice during the evolution of the Liparidae. The basal position of Nectoliparis is supported by its plesiomorphic otolith morphology, whereas an advanced overgrown otolith ostium, unique among teleosts, is found to be apomorphic for a clade containing the derived genera: Paraliparis, Psednos, Rhinoliparis and Rhodichthys. We also identify the presence of probable nuclear inserts of mitochondrial DNA (Numts) in three species of Careproctus and in Elassodiscus caudatus.     

The Fossil Record of the Solanaceae Revisited and Revised—The Fossil Record of Rhamnaceae Enhanced

Solanaceae is a large cosmopolitan family of angiosperms that includes some 92–100 genera and 2300–2500 species. It has been the object of a great deal of attention because of its economic importance as a food source (tomatoes, potatoes, peppers), because it includes tobacco, and is source of drugs (alkaloids). However its fossil history has been elusive with relatively few seemingly reliable reports throughout Tertiary times and no solid bases for molecular dating models to pinpoint important events in its diversification and evolution. While the great diversity found within the family makes it difficult to find morphological characters that define it, in general, the flowers have an overall distinctive morphology with some diagnostic morphological characters. Thus, as is often the case, flowers are potentially the most reliable indicators of the family in the fossil record. There have been a number of reports of flowers representing Solanaceae in the Tertiary. Yet, we report here that upon reinvestigation only one taxon remains as a plausible representative of the family while one of the most notable and frequently cited fossil Solanaceae from the Tertiary of North America is clearly a member of the family Rhamnaceae consistent with the fossil leaf record.