Taxonomic revision of buchanosteoid placoderms (Arthrodira) from the Early Devonian of south-eastern Australia and Arctic Russia

The ‘buchanosteid’ placoderms are best known from the Early Devonian of Australia, but also occur in China, Russia, Central Asia and the Middle East. Here we rediagnose the type species Buchanosteus confertituberculatus (Hills 1936) from the type locality at Buchan, Victoria, in the light of new material of both head and trunk shields. The superfamily Buchanosteoidea Denison, 1978 is redefined to unite taxa that share a similar skull roof with separate rostro-pineal (ethmoid) bone, and postethmoid skull pattern characterised by a large trapezoidal nuchal, strap-like short and broad preorbitals, large subrectangular centrals, small postorbitals not contacting the paranuchals, and large, elongate marginal plates. The Family Buchanosteidae is redefined on skull roof and parasphenoid shape and trunk armour features as a monotypic family within the Buchanosteoidea. A new family (Parabuchanosteidae nov.) includes taxa with the posterior lateral plate overlapping the anterior dorsolateral plate externally. Two new buchanosteids are described, Richardosteus barwickorum gen. et sp. nov., from Burrinjuck, south-eastern Australia, and Urvaspis lithuanica gen. et sp. nov., from Severnaya Zemlya, Russia.

Diploporite (Echinodermata, Blastozoa) thecal attachment structures from the Silurian of southeastern Indiana

Taxonomic descriptions of diploporites from the middle Silurian of eastern Laurentia have focused nearly entirely on thecal plating, with minimal description or figuring of attachment structures. A recently discovered hardground surface within the Wenlock-age (Sheinwoodian) Massie Formation that is encrusted by numerous well-preserved pelmatozoan holdfasts, including structures identifiable as diploporite thecal attachments, provides an opportunity to document the morphology of these rarely described structures. Moderately thin-walled structures with a parabolic, depressed central area composed of seven distinct marginal plates with prominent pores appear to represent thecal attachments of the broad-based trematocystinid holocystitid Paulicystis. Thick-walled, steep-sided structures composed of five to seven fused or partially fused plates with less prominent pores, a deep stelar depression, and radiating canals appear to represent thecal attachments of undetermined, possibly holocystinid or pentacystinid holocystitids. All diploporite holdfasts are cemented to fine-grained, well-sorted skeletal substrates on elevated crests of the hardground surface, but are not found on microbioherms.

New Associated Structures of the Anterior Flagella of Giardia duodenalis

Giardia duodenalis is a protozoan parasite that causes intestinal disorders. The trophozoites present four pairs of flagella. Here we further analyze the structural organization of the anterior flagella associated structures of G. duodenalis. High resolution scanning electron microscopy of detergent-extracted trophozoites revealed novel aspects of the interaction of the anterior flagella axonemes with the marginal plates. Images of the marginal plates showed that it was located in the anterior region of the parasite, above the crossing point of the anterior flagella axonemes toward the periphery of the cell. Two well distinguished structures were seen associated with the anterior flagella. The first one corresponds to the “dense rods”, located just below the axoneme. The second one is a system of filaments located in the upper portion of the flagellum, facing the marginal plates and connecting these two structures. The thickness of the filaments is around 18 nm and they are spaced at intervals of 4–32 nm (average 18 nm). The length of the filaments may vary from 33 to 240 nm. We suggest that this filamentous structure of Giardia may help the dynamics and behavior of the anterior flagella of trophozoites during protozoan motility and adhesion, providing favorable conditions for the establishment of parasitism.

A new species of Neoferdina and three new records of sea stars (Echinodermata: Asteroidea) collected from Kumejima Island, southwestern Japan

Sea stars were collected at depths ranging from 91 to 160 m around Kumejima Island situated in the middle of the RyukyuIslands chain in the Western Pacific. Sampling was carried out using a dredge or beam trawl in November 2009, as partof the KUMEJIMA 2009 Expedition. The specimens included an undescribed species of the genus Neoferdina, and threespecies that have never been reported in Japanese waters. Features that characterise this new species, Neoferdina longi-brachia, include: extremely long and narrow arms, no alternating arrangement of large and small superomarginal plates,body surface (except for the marginal plates) completely covered with granules, and an adambulacral armature with 3 furrow spines.

Morphologic and systematic revision of the solute Maennilia estonica (Homoiostelea, Echinodermata) from the Upper Ordovician of Estonia

Maennilia estonica Rozhnov and Jefferies was first described as a stem-chordate but restudy shows it is an unusually large homoiostelean echinoderm. Its feeding structure, an erect ambulacrum, extending exothecally from the peristomial frame plates, bears a large internal tunnel that opens directly into the body cavity. This type of feeding appendage is now recognized to be unique to homoiosteles. It bears no evidence for water vascular system impressions adjacent to its food groove. The theca has poorly developed marginal plates and a narrow rim that, in contrast to some other homoiosteles, does not extend over either lower or upper thecal face. Maennilia appears to have inhabited the deeper portions of a near-shore environment in limey muds adjacent to a linear zone of bryozoan and microbial bioherms.

Henricia pumila sp. nov.: A brooding seastar (Asteroidea) from the coastal northeastern Pacific

A small species of the seastar genus Henricia Gray, 1840 occurs along the cool temperate Pacific coast of North America from near Sitka, Alaska to just south of Ensenada, Baja California, Mexico. Its small adult size, mottled aboral colors, and benthic external brooding reproductive mode have long been noted, but it has never been formally separated from the larger, free-spawning Henricia leviuscula (Stimpson, 1857), with which it has been confused. Here we amplify the description of H. leviuscula, based on examination of the holotype and new specimens, and restrict it to only one of several similar species that co-occur in Puget Sound and vicinity. We also describe the small mottled brooder as Henricia pumila sp. nov., characterize its distribution, and contrast its morphology with H. leviuscula based on the arrangement of marginal plates and the microanatomy of aboral spines.

Carcinization in the Anomura – fact or fiction? II. Evidence from larval, megalopal and early juvenile morphology

In this second of a two-part series, carcinization in the Anomura has been reviewed from early juvenile, megalopal, and larval perspectives. Data from megalopal and early juvenile development in ten genera of the Lithodidae have provided unequivocal evidence that earlier hypotheses regarding evolution of the king crab pleon were erroneous. A pattern of sundering, and decalcification has been traced from the megalopal stage through several early crabs stages in species of Lithodes and Paralomis, with supplemental evidence from species in eight other genera. Of major significance has been the attention directed to the Marginal plates of the second pleomere, which when separeted in lithodids are not homologous with the adult so-called “marginal plates” of the following three tergites. Auxiliary megalopal and early juvenile lithodid data, as well as equivalent data from other paguroids, support the evolutionary direction indicated by lithodid pleonal plate development. Therefore, while carcinization, or development of a crab-like body form, has occurred in the Lithodidae, it has not proceeded from a hermit crab ancestor. Rather the data suggest the reverse, thus effectively refuting the “hermit to king” myth. Brief reviews of data available from the Lomisidae and Porcellanidae support the proposition of independent anomuran carcinization events in these taxa as well. Results of cladistic analysis of megalopal and juvenile data, although somewhat unconventional, do not support the claim of a sister-group relation of the lithodid genera Lithodes and Paralithodes with the pagurid genus Pagurus. Attempts to subject larval phase data to similar analysis were thwarted by the tendency in paguroids, including lithodids, for lecithotrophic development. Additionally, presumed initial and terminal stage deletions disallow the ontogenetic stage homologies required for meaningful phylogenetic results.

Re-evaluation of Graneledone setebos (Cephalopoda: Octopodidae) and allocation to the genus Megaleledone

The holotype of the Antarctic octopodid Graneledone setebos was re-examined and found to lack the epidermal warts characteristic of the genus Graneledone. It is similar in its large size to another Southern Ocean species, Megaleledonesenoi. A comparative study of G. setebos and specimens attributed to M. senoi led us to conclude that M. senoi is a junior synonym of G. setebos. Although M. senoi is not valid, the genus Megaleledone can be separated from other genera by the structure of the radula (which lacks marginal plates) and we therefore consider the genus to be valid. We propose the new combination of Megaleledone setebos and have refigured the beaks and radula of the holotype herein and expanded the description. A search of museum specimens and the literature shows that Megaleledone setebos is more common in Antarctic waters than previously supposed.

Morphological and paleoecological analysis of the Ordovician ankyroid Lagynocystis (Stylophora: Echinodermata)

Despite its atypical thecal plate pattern, Lagynocystis pyramidalis (Jaekel, 1918) (Middle Ordovician, Northern Gondwanaland) is composed of normally positioned marginal plates on the left side of the theca, whereas those on the right side are shortened or missing in comparison with marginal plates of other ankyroids. The only somatic on the lower thecal surface is the CS plate. The abnormally long distal aulacophore, reduced theca, and internal ctenoid organ are interpreted as adaptations to deep water, dysaerobic environmental conditions. Ctenoid organ morphology is re-evaluated and is interpreted to have both feeding and respiratory functions. Loss of plates relative to a presumed ancestor similar to Barrandeocarpus has resulted in torsion that places somatic platelets, originally on the superior face, onto the inferior face and in contact with both CS and M′3 plates.

Jaws and radula of the Carboniferous ammonoid Cravenoceras

A well-preserved mouth apparatus consisting of jaws and a radula was found in situ within the body chamber of the goniatite Cravenoceras fayettevillae Gordon, 1965 (Neoglyphiocerataceae: Cravenoceratidae), from the middle Chesterian (Upper Mississippian) of Arkansas. Both upper and lower jaws consist of a black material. The lower jaw is characterized by a widely opened larger outer lamella and a shorter inner lamella. The upper jaw is fragmental. The radula is preserved in the anterior portion of the buccal space and comprises a series of tooth elements. Each transverse tooth row consists of seven teeth (a rhachidian and pairs of two lateral and one marginal teeth), with a pair of marginal plates. This arrangement is typical of radulae of other ammonoids of Carboniferous to Cretaceous age, coleoids, and the orthoconic “nautiloid” Michelinoceras (Silurian, Michelinocerida), suggesting a phylogenetic affinity among them.