Aspects of evolutionary differentiation of theHamamelidaceae and the LowerHamamelididae

New investigations on the flower and fruit structure of extantHamamelidaceae and other LowerHamamelididae together with new finds of fossil flowers and seeds from the Upper and Lower Cretaceous provide the outline of an increasingly more differentiated picture of the early evolution of the subclass. Three patterns of valvate anther dehiscence are recognized in the subfamilyHamamelidoideae (and the subclassHamamelididae). The basic (plesiomorphic) type within theHamamelididae has 2 valves per theca. The type with 1 valve but 2 pollen sacs per theca is both consistent and exclusive for the 5 southern genera of theHamamelidaceae. They seem to be the remnants of a homogeneous group that originated before the Upper Cretaceous. This is supported by fossil hamamelidaceous flowers from the Upper Cretaceous that have thecae with 1 valve. Since several-seededHamamelidaceae predate one-seeded forms in the fossil seed record (in Europe) and the systematic structure of the one-seeded group is relatively more homogeneous, several-seeded groups are considered to be more ancient. Several parallel evolutionary trends are recognized within theHamamelidaceae as well as within the LowerHamamelididae: anther dehiscence with 2 valves per theca 1 slit or 1 valve; pollen sacs per theca 2 1; pollen tricolpate polyforate; exine coarsely reticulate finely reticulate; loss of perianth (tepals or petals and sepals) and concomitant loss of fixed number of floral organs; differentiation of exposed nectaries.     

A preliminary phylogeny of the Pterasteridae (Echinodermata,Asteroidea) and the first fossil record: Late Cretaceous of Germany and Belgium

The Pterasteridae comprises a diversified group of extant largely deep-sea starfishes. Generic diagnoses have been based classically on soft tissue characters and skeletal architecture. A preliminary phylogeny of sixteen extant species is here worked out by cladistic analysis. The resulting tree suggests monophyly of extant genera and the validity of dissociated plates for identification of genera. Fossil remains of Pterasteridae are here described for the first time. By comparison with extant species, all the skeletal remains from the lower Upper Campanian of Belgium and from the lower Maastrichtian of Germany are tentatively assigned to the genusPteraster. The fossil record of starfishes is poor, but the present Late Cretaceous pterasterids provide one more piece of evidence of the high diversity of starfishes during the Mesozoic. Known Late Cretaceous and Paleogene fossils are broadly similar, which suggests the end-Cretaceous extinction event did not cause major turnover in asteroid faunal composition. As suggested for other starfish groups, both the fossil record of deep-sea Pterasteridae in shelf settings and tree topology imply an onshore-offshore evolutionary trend.      

Upper Cretaceous aquatic plants from Northern Mexico

Two aquatic plant genera assignable to Decodon (Lythraceae) and Ceratophyllum (Ceratophyllaceae) are described based on reproductive structures collected from the Cerro del Pueblo Formation (late Campanian [73.5 ma]), Coahuila, Northeast Mexico. Decodon is represented by three small seeds with a pyramidal shape, rounded borders, and a concave ventral surface with a rectangular valve towards the center of the seed ventral surface. The Ceratophyllum spiny fruit has an ellipsoidal central body and two proximal long spines flanking a short pedicel opposite the stylar projection. These new reports confirm the presence of both genera in the Upper Cretaceous sediments of Northeastern Mexico, and add to our recognition of diversity within the widely distributed freshwater communities along the margin of the epicontinental sea.     

Structure of the inflorescence and flower ofPetalonyx linearis (Loasaceae)

Fossil chloranthoid androecia,Chloranthistemon endressii gen. et spec. nov. are described from the Upper Cretaceous (Upper Santonian or Lower Campanian) of Scania, southern Sweden. They are three-lobed and dorsiventrally flattened with all pollen sacs borne laterally and inclined toward the presumed adaxial surface. The central lobe bears two pairs of pollen sacs, the lateral lobes a single pair each. The morphology, anatomy and valvate dehiscence of the fossil androecia is very similar to that seen in extant species ofChloranthus andSarcandra, but the in situ pollen differs from that of all extantChloranthaceae in being spiraperturate. A single chloranthoid androecium from the Lower Cretaceous (Upper Albian) of Maryland, North America has a more generalized structure thanChloranthistemon endressii. It consists of three stamens that are fused at the base, and each stamen bears two pairs of oppositely positioned pollen sacs. Combined with anatomical information from recentChloranthus the Lower Cretaceous specimen suggests that the androecium in the living genus has arisen by fusion and other modifications of three separate stamens each with a normal complement of four pollen sacs. The structure of both the Upper and Lower Cretaceous androecia suggest that these fossilChloranthaceae were insectpollinated. Macrofossil evidence combined with information from dispersed pollen indicates that theChloranthaceae diversified early in angiosperm fossil history and were an important component of Mid-Cretaceous plant communities.     

Fossil flowers and pollen ofLauraceae from the Upper Cretaceous of New Jersey

A fossil trimerous flower from the Turonian (ca. 90 MYBP, Upper Cretaceous) of New Jersey is described as a new genus in the familyLauraceae. The fossil flower is charcoalified and preserved in exceptional detail. This fossil specimen is particularly remarkable in that several pollen grains have been preserved; pollen grains ofLauraceae generally have very thin exine and are rarely preserved in the fossil record. Although the specimen is incomplete and lacks anthers, there are sufficient structural details preserved to permit an assignment to theLauraceae, as well as comparisons with the tribePerseeae. This new genus provides an important addition to our knowledge of systematic and structural diversity in CretaceousLauraceae.     

Reproductive structures of Rhamnaceae from the Cerro del Pueblo (Late Cretaceous, Coahuila) and Coatzingo (Oligocene, Puebla) Formations, Mexico

Recently discovered fossil flowers from the Cretaceous Cerro del Pueblo and flowers and fruits from the Oligocene Coatzingo Formations are assigned to the Rhamnaceae. The Cretaceous flower, Coahuilanthus belindae Calvillo-Canadell and Cevallos-Ferriz, gen. et sp. nov., is actinomorphic with fused perianth parts forming a slightly campanulate to cupulate floral cup, with sepals slightly keeled and spatulate clawed petals. The Oligocene fossils include Nahinda axamilpensis Calvillo-Canadell and Cevallos-Ferriz, gen. et sp. nov. (characterized by its campanulate bisexual flower with stamens opposite, adnate to and enfolded by petals; and with the ovary ripening into a drupe), and a winged fruit assigned to Ventilago engoto Calvillo-Canadell and Cevallos-Ferriz, sp. nov. The flowers and drupe features indicate closer affinity to Zizipheae and/or Rhamneae, while the single samaroid fruit suggests the presence of Ventilagineae. However, the unique character combination in the fossil flowers precludes placing them in extant genera. Nevertheless, the history of the family is long and can be traced back to the Campanian. A detailed phylogenetic revision of the group that uses morphological characters from both extant and fossil plants is needed to better understand the significance of these records as well as other important fossils of the family.     

Fossil spores and pollen grains of cretaceous (Upper campanian) from Sakhalin, Russia

This paper shows fossil spores and pollen grains from Cretaceous (Upper Campanian) of Sakhalin, Russia, with scanning electron microscopy. A total of 520 palynomorph assemblages consisting of 25% spores of pteridophytes and bryophytes, 4.5% of ephedroid pollen grains, 6.5% of coniferous pollen grains, and 64% of angiospermous pollen grains were recovered in the present study. 5 genera of pteridophytes, 4 genera of gymnosperms, and 18 genera of angiosperms are described in the present study. The frequent and representative genera from the stratum areEphedripites, Liliacidites, Clavatipollenites, Tricolpites, Aquilapollenites, andAzonia. A new genus,Sciadopitipollenites, that is comparable with extantSciadopitys is proposed in the present study. Polycolpate pollen with the same exine sculpture ofClavatipollenites suggests a generic differentiation in the Chloranthaceae during the Cretaceous age. The diverse spores and pollen paleoflora shown in the present study suggests a wide diversification of angiosperms in the Upper Campanian at the eastern side of Laurasia (Aquilapollenites province).     

Sorophores of<Emphasis Type="Italic">Lygodium</Emphasis> Sw. (Schizaeaceae) from the Late Cretaceous of New Jersey

We report here on a series of specimens of charcoalified sorophores with characteristics of the extant fern genusLygodium (Schizaeaceae) collected from sediments of the Raritan Formation (Late Cretaceous). Each elongate lobed fertile pinnule (sorophore) is flattened and bears alternately arranged sporangia on one surface. Each sporangium is covered by an indusium continuous with the margin of the lamina. Sporangia are oblong in shape, short stalked, and have an apical annulus formed by a single ring of radiating cells that dehisces longitudinally. The sporangial cap or distal face is formed by only one cell. All of these features are characteristic of the extant genusLygodium. Small numbers of trilete, psilate spores are found in the sporangia. Megafossils assignable toLygodium are known from the Upper Cretaceous of North America and Germany with worldwide distribution during the Tertiary. The newLygodium fossils are compared with others previously referred to the genus.     

Plio-Pleistocene cercopithecids from Kanam East, western Kenya

This paper describes cercopithecid craniodental and postcranial fossils recovered by L. S. B. Leakey at Kanam East, Kenya during the early 1930s. These fossil monkeys have been generally assumed to have been derived from early Pliocene horizons, but their exact geographical and stratigraphical provenience is unknown. Although the question of the evolutionary significance of these specimens must await the recovery of more securely dated material from Kanam East, some general conclusions can be drawn concerning their taxonomic affinities and paleobiology. Based on comparative studies of the craniodental material, at least three extant genera are represented—Colobus,Lophocebus, andCercopithecus. The postcranial fossils include a number of hindlimb specimens, as well as the manubrium of a sternum and a caudal vertebra. Identification of the postcranial remains to particular genera is not possible, but they are similar in morphology to modern arboreal and semiterrestrial cercopithecid monkeys of small to medium size. It is evident that Kanam East had a diverse cercopithecid community, similar to those found today in forested and woodland habitats, and this may be of some significance in reconstructing the paleoecology of the site. Because the fossil record of most extant cercopithecid genera is rather sparse at Plio-Pleistocene sites in Africa, Kanam East represents one of only a few sites that has yielded material that can be assigned toColobus,Lophocebus, orCercopithecus. The fossil monkeys from the site, therefore, provide additional evidence to help reconstruct the paleobiology, as well as the patterns of species diversity and community structure that characterized the cercopithecid radiation during the Plio-Pleistocene.     

Scandianthus gen.nov., Angiosperm Flowers of Gaxifragalean Affinity from the Upper Cretaceous of Southern Sweden

Structurally preserved angiosperm flowers are described fromthe Upper Cretaceous of southern Sweden. They are found in fluviatiledeposits dated, on palynological evidence, as Upper Santonianor Lower Campanian. The material studied includes two speciesof Scandianthus gen.nov. and one unnamed, related taxon. Thefossil flowers represent the best-preserved Cretaceous floralstructures available and the preservation permits detailed studyof organization and arrangement of parts. Comparison with flowersof extant angiosperms indicates a close relationship with membersof the Saxifragales. Scandianthus gen.nov. fossil angiosperm, Upper Cretaceous     

Marsileaceaephyllum, a new genus for marsileaceous macrofossils: leaf remains from the Early Cretaceous (Albian) of southern Gondwana

Three new taxa from Albian, Early Cretaceous assemblages in Gondwana (Australia and Antarctica) and two previously described fossils from the Late Cretaceous and Eocene of North America are attributable to the heterosporous semi-aquatic fern family Marsileaceae. They are assigned to Marsileaceaephyllum, a morphotaxon erected here for sterile remains (whole plants, and isolated leaves and leaflets) of Marsileaceae. The Gondwanan taxa, Marsileaceaephyllum lobatum and Marsileaceaephyllum spp. B-C, have either a cruciform leaflet arrangement or dichotomous and anastomosing venation characteristic of modern Marsileaceae. Two previously established taxa, Marsilea johnhallii and Marsilea sp., which represent sterile Marsileaceae, are also transferred to the new genus (now Marsileaceaephyllum johnhallii and Marsileaceaephyllum sp. A, respectively). Examination of all fossil venation patterns reveals four new venation types not present in extant taxa, suggesting that most fossil Marsileaceae (leaves) are distinct from extant genera, and are likely members of extinct lineages. This is further supported by the absence of modern megaspore types in the Early Cretaceous.     

Structure and affinities of the petrified plants from the cretaceous of Northern Japan and Saghalien. XII.Obirastrobus gen. nov., petrified pinaceous cones from the Upper Cretaceous of Hokkaido

Two new species of pinaceous cones belonging toObirastrobus gen. nov. are described from the Upper Cretaceous of Hokkaido. Bract-scale complexes are arranged helically and each consists of a small bract and a large scale. The bract and scale are separated. The scale tapers distally and its apex does not become papery. The anatomy of the bracts, scales, and seeds shows a combination of features unique in the Pinaceae and resembling those of the extant genusKeteleeria and the extinct genusPseudoaraucaria. Consecutive number from the previous paper (Ohsawaet al., 1992). Supported by Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture Nos. 63540545 and 02640533 to Makoto Nishida.     

Fossil flowers and fruits of the Actinidiaceae from the Campanian (Late Cretaceous) of Georgia

A new genus and species of Actinidiaceae (Parasaurauia allonensis gen. et sp. nov.) are established for fossil flowers and fruits from the early Campanian (Late Cretaceous) Buffalo Creek Member of the Gaillard Formation in central Georgia, USA. The fossil flowers, which are exquisitely preserved as charcoal, have five imbricate, quincuncially arranged sepals and petals. The androecium consists of ten stamens with anthers that are deeply sagittate proximally. The gynoecium is tricarpellate, syncarpous, and has three free styles that emerge from an apical depression in the ovary. The fruit is trilocular and contains numerous ovules on intruded axile placentae. The structure of mature fruits is unknown. Comparisons with extant taxa clearly demonstrate that the affinities of Parasaurauia allonensis are with the Ericales, and particularly with the Actinidiaceae, which have been placed among the Ericales in recent cladistic analyses. Because Parasaurauia allonensis is not identical to any one genus of Actinidiaceae, or other member of the Ericales, phylogenetic relationships of the fossil were evaluated through a cladistic analysis using morphological and anatomical characters. Results of this analysis place Parasaurauia allonensis within the Actinidiaceae as sister to the extant genera Saurauia and Actinidia. Parasaurauia allonensis differs from extant Saurauia only in having ten rather than numerous stamens.     

Tylerianthus crossmanensis gen. et sp. nov. (aff. Hydrangeaceae) from the Upper Cretaceous of New Jersey

A fossil flower with affinities to the modern families of the saxifragalean complex is described. Fossils were collected at Old Crossman Pit, Raritan Formation, New Jersey, USA. These sediments are dated on the basis of palynology as Turonian (Upper Cretaceous, ~90 million years before present). Fossils are charcoalified and preserved with exceptional three- dimensional detail. The characters observed in these flowers, when compared with those of extant flowers of several families of the saxifragalean complex, suggest a close relationship with extant members of the Saxifragaceae and Hydrangeaceae. Hypotheses on the origin of petals and staminodes and a possible mechanism of pollination are discussed. This new taxon provides additional characters in the floral morphology of the fossil saxifragoids and extends their geographical distribution in the Cretaceous to North America.     

EMBRYOGENY AND REPRODUCTIVE BIOLOGY OF BOTHRODENDROSTROBUS MUNDUS (LYCOPSIDA)

Permineralized lycopsid megagametophytes and embryos from Upper Carboniferous strata (Westphalian A) at Burnley, England have been found within isolated megaspores assignable to Setosisporites. The specimens illustrate for the first time the reproductive biology and embryogeny of a free-sporing, bisporangiate, Paleozoic lycopod, and permit reinterpretation of the megagametophyte of Bothrodendrostrobus. Megagametophyte development is entirely endosporal. Embryogeny is comparable to that of the extant genus Isoetes, and is fundamentally different from that of the fossil lycopsid, Lepidocarpon—Lepidophloios. This further illustrates the diversity among Paleozoic lycopods and helps to clarify relationships among both fossil and extant lycopsid taxa.     

Mesozoic Araucariaceae: Morphology and systematic relationships

The Southern Hemisphere conifer family Araucariaceae has a very restricted present day distribution, but was more widespread in the past. The genusAraucaria is represented by good fossil material in both hemispheres as early as the Jurassic, whileAgathis is only known from the Southern Hemisphere beginning in the Cretaceous. Cuticle studies of extant araucarians have enabled accurate comparisons of fossil leaves to living taxa.Araucaria SectionBunya is represented by cones of several types in the Jurassic. In addition to these remains, a suite of araucarian cones showing affinities to several sections of the genusAraucaria have been described from England, Japan and North America. Evidence that fossil araucarian cones may have produced seeds with hypogeal germination is discussed in light of recent work on germination of extant bunya seedlings and the discovery of new fossil shoots from the Jurassic Morrison Formation of Utah.     

Fossil Cycadales of Argentina

A survey of Cycadalean taxa of Argentina (including Antarctica) is presented. The record of leaves represented byNilssonia, Pseudoctenis, Ctenis, Mesodescolea, Ticoa, Almargemia,Kurtziana, andZamia genera are summarized. Recent investigations made of cuticles with transmission and scanning electron microscopy are included. In stems, a preliminary study of two forms found in the Upper Cretaceous of Rio Negro Province are incorporated intoMichelilloa, Bororoa, andMenucoa. The fossil record shows some characters of leaf morphology, presence of inverse xylem and medullary bundles, two kinds of leaf traces, and monoxylic and polyxylic steles of systematic importance when compared with both extant and fossil cycads. Affinities of fossil taxa related to extant families are suggested through analysis of the above-mentioned characters. The presence of medullary vascular rings related to the emission of terminal reproductive strobili are recognized inBororoa andMenucoa. This character associated with polyxyly makes it possible to assign these genera to the Zamiaceae-Encephalartoideae sensu Stevenson, widening the paleogeographical distribution of this subfamily.     

A Cretaceous crane-fly (Diptera: Tipulidae): 93 million years of stasis

A new fossil species of crane-fly, Helius botswanensis:Diptera: Tipulidaey is described. The specimen was discovered recently in reliably dated. Cretaceous sediments from Botswana. Ii is extremely well preserved, has a distinctive morphology, and is identified as belonging to the extant genus Helius. The single specimen puts the origin of the subfamily Limoniinae and the genus well into the Cretaceous Period, and provides data on the southern African Cretaceous palaeoenvironment. The conservative nature of a dipteran of such antiquity, assignable to an extant genus which has an association with flowers, has implications for evolutionary theory.     

Archamamelis,hamamelidalean flowers from the Upper Cretaceous of Sweden

Lignite fossil flowers (including pollen) and isolated stamens of probable hamamelidalean (possible hamamelidaceous) affinities from the upper Cretaceous (Late Santonian or Early Campanian) of Sweden are described. The flowers are 6–7-merous with probably a double perianth, one whorl of stamens and (2-?)3 carpels. The stamens are disporangiate; each theca opens by a valve towards the centre of the flower. Pollen is tricolpate, tectate-columellate and reticulate; the endexine is lamellated in the apertural region. The gynoecium has free styles and a syncarpous ovary. In the one flower that was serially sectioned the ovary is either non-functional or development of the few (2?) ovules is retarded.