Nostolepis scale remains (stem Chondrichthyes) from the Lower Devonian of Qujing, Yunnan, China

Based initially on microfossils, Nostolepis is one of the first known ‘acanthodians’, which constitute a paraphyletic assemblage of plesiomorphic members of the total group Chondrichthyes. Its wide distribution has potential implications for stratigraphic comparisons worldwide. Six species of Nostolepis have been reported in China, including one species from the Xitun Formation (Lochkovian, Lower Devonian) of Qujing, eastern Yunnan. Acid preparation of rock samples from the Xitun Formation has yielded abundant acanthodian remains. Based on both morphological and histological examinations, here we identify five species of Nostolepis, including two new species. N. qujingensis sp. nov. is characterized by thin scales devoid of the neck anteriorly and the dentine tubules rarely present in the anterior part of the crown. N. digitus sp. nov. is characterized by parallel ridges on anterior and lateral margins of the crown, and the neck constricted and ornamented with pore openings. We extend the duration of N. striata in China from the Pridoli of Silurian (Yulungssu Formation) to the Lower Devonian in Qujing and report the first occurrences of N. amplifica and N. consueta in this region. This study increases the diversity of the Lower Devonian Xitun Fauna and provides a better understanding of the paleogeographic distribution of Nostolepis.

What the Ur-crustacean Looked Like

Crustaceans are a paraphyletic assemblage within arthropods. Hexapoda (insects) are nested within crustaceans, with the Remipedia the most likely sister group to Hexapoda. Together, crustaceans and hexapods comprise the monophyletic Tetraconata (also called Pancrustacea). Herein, we “reconstruct” the last common ancestor of crown group Tetraconata, calling it the ur-crustacean. We base our reconstruction on knowledge of extant crustaceans. We tentatively suggest that the ur-crustacean displayed certain characters: The ur-crustacean was a free-living marine species with a distinct head and equipped with two pairs of sensory limbs (antennule and antenna), mandibles, and two more pairs of mouthparts (maxillule and maxilla). We suggest that no further segments were fused to the head and that no maxilliped was present. The ur-crustacean may or may not have possessed a carapace. Its brain was complex, with an extended olfactory system, possibly a central complex, and a lateral protocerebrum containing at least two optical neuropils. The protocerebrum was connected to a nauplius eye as well as to compound eyes. The ur-crustacean might have had a uniformly segmented trunk posterior to its five-segmented head or (less probably) may have possessed two tagmata, a limb-bearing thorax and a limb-less abdomen. It had a heart that might have extended right through the trunk independently of tagmatization. Its thoracopodal appendages were true arthropodal (consisting of podomeres) with a protopod (probably subdivided into coxa and basis), an exopod, and an endopod. Larval development started with a nauplius larva (probably an orthonauplius).

A Review of Necrotauliids from the Triassic/Jurassic of England (Trichoptera: Necrotauliidae)

Species previously attributed to Necrotauliidae are revised from the Late Triassic and Early Jurassic of England based on examination of type specimens and non-type material. The necrotauliids have been considered as a basal family of caddisflies (Trichoptera) or as a paraphyletic assemblage of stem-amphiesmenopterans. Herein a new genus, Austaulius, is erected which includes all Lilstock Formation∖Lower Lias material from England; the previously described species are synonymized with A. furcatus and a new species, A. haustrum, is described from the Dorset Coast, the holotype of which preserves synapomorphic traits of the Trichoptera not previously described suggesting that the family is trichopteran. The type genus remains Necrotaulius and type species N. parvulus (Geinitz, 1884) from the type locality of Dobbertin, Germany. One species of Necrotaulius is represented in the UK, N. parvulus, which is found in the Upper Lias.

Precise occlusion and trophic niche differentiation indicate specialized feeding in Early Devonian jawed vertebrates

Acanthodians may represent a paraphyletic assemblage of stem chondrichthyans, stem osteichthyans, stem gnathostomes, or some combination of the three. One of the difficulties in determining the phylogenetic affinities of this group of mostly small, spiny fishes is that several subgroups of acanthodians are represented by relatively little information in the fossil record. It is becoming increasingly apparent that to understand the evolution of gnathostomes, we must understand more about acanthodians. This study uses micro-computed tomography to test hypotheses about acanthodian jaw function, and in doing so provides insight into the form, function, and ecological role of ischnacanthiform acanthodian jaws and teeth from an extraordinary Early Devonian fossil locality in the Northwest Territories of Canada. The results of this study suggest that ischnacanthiform acanthodians may have coexisted by trophic niche differentiation, employing specialized feeding strategies during the Silurian and Early Devonian.

Molecular systematics of marine gregarine apicomplexans from Pacific tunicates, with descriptions of five novel species of Lankesteria

The eugregarines are a group of apicomplexan parasites that mostly infect the intestines of invertebrates. The high level of morphological variation found within and among species of eugregarines makes it difficult to find consistent and reliable traits that unite even closely related lineages. Based mostly on traits observed with light microscopy, the majority of described eugregarines from marine invertebrates has been classified into a single group, the Lecudinidae. Our understanding of the overall diversity and phylogenetic relationships of lecudinids is very poor, mainly because only a modest amount of exploratory research has been done on the group and very few species of lecudinids have been characterized at the molecular phylogenetic level. In an attempt to understand the diversity of marine gregarines better, we surveyed lecudinids that infect the intestines of Pacific ascidians (i.e. sea squirts) using ultrastructural and molecular phylogenetic approaches; currently, these species fall within one genus, Lankesteria. We collected lecudinid gregarines from six ascidian host species, and our data demonstrated that each host was infected by a different species of Lankesteria: (i) Lankesteria hesperidiiformis sp. nov., isolated from Distaplia occidentalis, (ii) Lankesteria metandrocarpae sp. nov., isolated from Metandrocarpa taylori, (iii) Lankesteria halocynthiae sp. nov., isolated from Halocynthia aurantium, (iv) Lankesteria herdmaniae sp. nov., isolated from Herdmania momus, (v) Lankesteria cf. ritterellae, isolated from Ritterella rubra, and (vi) Lankesteria didemni sp. nov., isolated from Didemnum vexillum. Visualization of the trophozoites with scanning electron microscopy showed that four of these species were covered with epicytic folds, whereas two of the species were covered with a dense pattern of epicytic knobs. The molecular phylogenetic data suggested that species of Lankesteria with surface knobs form a clade that is nested within a paraphyletic assemblage species of Lankesteria with epicytic folds.

A molecular palaeobiological hypothesis for the origin of aplacophoran molluscs and their derivation from chiton-like ancestors

Aplacophorans have long been argued to be basal molluscs. We present a molecular phylogeny, including the aplacophorans Neomeniomorpha (Solenogastres) and Chaetodermomorpha (Caudofoveata), which recovered instead the clade Aculifera (Aplacophora + Polyplacophora). Our relaxed Bayesian molecular clock estimates an Early Ordovician appearance of the aculiferan crown group consistent with the presence of chiton-like molluscs with seven or eight dorsal shell plates by the Late Cambrian (approx. 501–490 Ma). Molecular, embryological and palaeontological data indicate that aplacophorans, as well as chitons, evolved from a paraphyletic assemblage of chiton-like ancestors. The recovery of cephalopods as a sister group to aculiferans suggests that the plesiomorphic condition in molluscs might be a morphology similar to that found in monoplacophorans.

A revision of Plesiobaena (Testudines: Baenidae) and an assessment of baenid ecology across the K/T boundary

Over the course of the last two decades, the baenid taxon Plesiobaena has typically been thought to consist of two named species, Plesiobaena antiqua (Campanian) and Plesiobaena putorius (Paleocene), along with an unnamed species from the Maastrichtian, but the interrelationship of these three taxa was never explored in an explicit phylogenetic context. Herein we present or re-describe a number of relevant specimens and provide a cladistic analysis of Baenidae using species only as terminal taxa. The phylogenetic analysis clearly reveals that Plesiobaena in the traditional sense is a paraphyletic assemblage relative to the clade formed by Gamerabaena sonsalla and Palatobaena spp., thus demanding some nomenclatural adjustments. In particular, Plesiobaena putorius is moved to a new genus, Cedrobaena, and the unnamed taxon from the Maastrichtian is formally named Peckemys brinkman. Many of the new Cedrobaena putorius and Peckemys brinkman specimens described herein were found at the Turtle Graveyard locality in Slope County, North Dakota, along with four other turtle taxa, increasing the turtle diversity of this locality to at least six taxa. Although this indicates that Turtle Graveyard is the world's most diverse fossil turtle thanatocoenosis, a comparable diversity is found in modern river systems in the southeastern United States today. Our phylogenetic analysis indicates that seven out of nine latest Cretaceous baenid turtle lineages survived into the Paleocene, four of which are interpreted as being durophagous.

A Morphology-Based Cladistic Analysis of Digitaria (Poaceae, Panicoideae, Paniceae)

A phylogenetic analysis was performed on 67 species of Digitaria belonging to four subgenera and 26 of the 32 sections recognized in Henrard's monograph. The analysis was based on 113 discrete and six continuous morphological characters. In the resulting topologies the genus Digitaria was monophyletic. In spite of the low support for most groupings, several clades were recovered. The subdivision of Digitaria in the four subgenera proposed by Henrard was not supported since the large subgenus Digitaria appears as a paraphyletic assemblage within which the other three subgenera are nested. Nevertheless, the monophyly of some of Henrard's sections was supported. This is the first approach to the phylogeny of Digitaria. Se llevó a cabo un análisis cladístico. Se incluyeron 67 especies de Digitaria pertenecientes a los 4 subgéneros y a 26 de las 32 secciones reconocidas en la monografía de Henrard. El análisis fue basado en 113 caracteres morfológicos discretos y 6 continuos En las topologías resultantes el género Digitaria resultó monofilético. A pesar del bajo soporte de la mayoría de los grupos, fueron recuperados varios clados. Los resultados no fueron consistentes con la subdivisión de Digitaria en 4 subgéneros propuesta por Henrard, ya que el extenso subgénero Digitaria aparece como un agregado parafilético dentro del cual se hallan anidados los otros tres subgéneros. Sin embargo, la monofilia de algunas secciones fue confirmada. El presente estudio constituye el primer análisis filogenético de Digitaria.

Systematic status of the caridean families Gnathophyllidae Dana and Hymenoceridae Ortmann (Crustacea : Decapoda): a preliminary examination based on nuclear rDNA sequences

The systematic positions of the caridean families Gnathophyllidae and Hymenoceridae are inferred based on analyses of nuclear 18S rRNA and 28S rRNA genes. The phylogenetic trees based on 18S rRNA and 28S rRNA from selected species of one genus of the family Gnathophyllidae, two genera of the family Hymenoceridae, one genus of the family Anchistioididae, eight genera of the subfamily Pontoniinae and five genera of the subfamily Palaemoninae show a close relationship between Hymenoceridae, Gnathophyllidae and Pontoniinae, with the last group constituting a paraphyletic assemblage. This result concurs with the morphology of maxilla in the first zoea, but not the shape of the third maxilliped in adults, based on which Gnathophyllidae and Hymenoceridae are treated as families. Molecular analysis supports the similarities in larval morphology between Hymenoceridae, Gnathophyllidae and Pontoniinae and therefore draws into question the familial status of the former two groups.