Un nouveau placoderme pétalichtyidé du Dévonien inférieur d’Yunnan, Chine

Pauropetalichthys magnoculus, nouveaux genre et espèce de Petalichthyda (Gnathostomata; Placodermi) est décrit dans le tardi-Emsien (Dévonien inférieur) de Qujing, Yunnan, Sud-Ouest de la Chine. Une reconstitution tridimensionnelle du toit du crâne et du neurocrâne, basée sur la tomodensitométrie haute résolution révèle la configuration des canaux sensoriels, la surface viscérale du toit du crâne et le profil de l’endocrâne. Le revêtement périchondral des capsules nasales fournit la première évidence sérieuse de capsules nasales chez les pétalichthyidés. Une analyse phylogénétique caractérise le nouveau taxon comme étant le membre le plus basal des Quasipetalichthyidae, un groupe endémique frère des Macropetalichthyidae. À la lumière de ces traits endocrâniens récemment découverts, les auteurs discutent de la disparité morphologique des endocrânes de pétalichithyidé. La distribution paléogéographique des Petalichthyidea est résumée pour montrer le lieu d’origine du groupe et les itinéraires de dispersion.Pauropetalichthys magnoculus, a new genus and species within the Petalichthyida (Gnathostomata: Placodermi), is described from the Late Emsian (Early Devonian) of Qujing, Yunnan, southwestern China. A three-dimensional reconstruction of the skull roof and neurocranium based on high-resolution computed tomography reveals the pattern of sensory canals, the visceral surface of the skull roof, and the profile of the endocranium. The perichondral lining of the nasal capsules provides the first hard evidence of nasal capsules in petalichthyids. A phylogenetic analysis resolves the new taxon as the most basal member of the Quasipetalichthyidae, an endemic group sister to the Macropetalichthyidae. In light of the newly revealed endocranial features, we discuss the morphological disparity of petalichthyid endocrania. The paleogeographic distribution of the Petalichthyida is summarized to show the group\u27s center of origin and routes of dispersal.</p

A primitive fish provides key characters bearing on deep osteichthyan phylogeny

Osteichthyans, or bony vertebrates, include actinopterygians (teleosts and their relatives) and sarcopterygians (coelacanths, lungfishes and tetrapods). Despite features found in basal actinopterygians (for example, Dialipina and Ligulalepis)1-3 and basal sarcopterygians (for example, Psarolepis and Achoania)4,5, the morphological gap between the two lineages remains wide and how sarcopterygians developed a dermal surface covering known as cosmine (composed of a pore-canal network and a single layer of odontodes and enamel) is still poorly known6-10. Here we describe a primitive fossil fish, Meemannia eos gen. et sp. nov., that possesses an actinopterygian-like skull roof and a cosmine-like dermal surface combining a pore-canal network (found in various fossil sarcopterygians) with superimposed layers of odontodes and enamel (previously known in actinopterygians and some acanthodians11-13). This 405-million-year-old fish from the Lower Devonian of Yunnan (China) demonstrates that cosmine in many fossil sarcopterygians arose step by step through the acquisition of a pore-canal network followed by the subsequently developed ability to resorb previous generations of odontodes and enamel. Meemannia provides key characters for studying deep osteichthyan phylogeny and indicates a possible morphotype for the common ancestor of actinopterygians and sarcopterygians. © 2006 Nature Publishing Group

A new antiarch placoderm from the Emsian (Early Devonian) of Wuding, Yunnan, China

<p>Pan, Z., Zhu, M., Zhu, Y. & Jia, L., August 2017. A new antiarch placoderm from the Emsian (Early Devonian) of Wuding, Yunnan, China. <i>Alcheringa 42</i>, 10–21. ISSN 0311-5518.</p> <p><i>Wufengshania magniforaminis</i>, a new genus and species of the Euantiarcha (Placodermi: Antiarcha), is described from the late Emsian (Early Devonian) of Wuding, Yunnan, southwestern China. The referred specimens were three-dimensionally preserved in black shales, allowing a high-resolution computed tomography reconstruction of anatomical details. The new euantiarch is characterized by a large orbital fenestra, an arched exoskeletal band around the orbital fenestra and a developed obtected nuchal area of the skull roof. Maximum parsimony analysis, using a revised data-set of antiarchs with 44 taxa and 66 characters, resolves <i>Wufengshania</i> gen. nov. as a member of the Bothriolepididae, which is characterized by the presence of the infraorbital sensory canal diverging on the lateral plate, and the nuchal plate with orbital facets. New analysis supports a sister group relationship between <i>Dianolepis</i> and the Bothriolepididae. <i>Luquanolepis</i>, a coeval euantiarch from the neighboring site of the new form, is referred to the Asterolepidoidei and represents the basalmost and earliest member of the Asterolepidoidei.</p> <p><i>Zhaohui Pan* [</i>[email protected]<i>], Min Zhu* [</i>[email protected]<i>], You’an Zhu</i>^<i>†</i><i>[</i>[email protected]<i>]</i> and <i>Liantao Jia [</i>[email protected]<i>] Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, PR China. *Also affiliated with University of Chinese Academy of Sciences, Beijing, 100049, PR China.</i> ^<i>†</i><i>Also affiliated with Uppsala University, PO Box 256, 751 05 Uppsala, Sweden.</i></p

A new osteichthyan from the late Silurian of Yunnan, China.

Our understanding of early gnathostome evolution has been hampered by a generally scant fossil record beyond the Devonian. Recent discoveries from the late Silurian Xiaoxiang Fauna of Yunnan, China, have yielded significant new information, including the earliest articulated osteichthyan fossils from the Ludlow-aged Kuanti Formation. Here we describe the partial postcranium of a new primitive bony fish from the Kuanti Formation that represents the second known taxon of pre-Devonian osteichthyan revealing articulated remains. The new form, Sparalepis tingi gen. et sp. nov., displays similarities with Guiyu and Psarolepis, including a spine-bearing pectoral girdle and a placoderm-like dermal pelvic girdle, a structure only recently identified in early osteichthyans. The squamation with particularly thick rhombic scales shares an overall morphological similarity to that of Psarolepis. However, the anterior flank scales of Sparalepis possess an unusual interlocking system of ventral bulges embraced by dorsal concavities on the outer surfaces. A phylogenetic analysis resolves Sparalepis within a previously recovered cluster of stem-sarcopterygians including Guiyu, Psarolepis and Achoania. The high diversity of osteichthyans from the Ludlow of Yunnan strongly contrasts with other Silurian vertebrate assemblages, suggesting that the South China block may have been an early center of diversification for early gnathostomes, well before the advent of the Devonian "Age of Fishes"

The earliest known stem-tetrapod from the Lower Devonian of China

Recent discoveries of advanced fish-like stem-tetrapods (for example, Panderichthys and Tiktaalik) have greatly improved our knowledge of the fin-to-limb transition. However, a paucity of fossil data from primitive finned tetrapods prevents profound understanding of the acquisition sequence of tetrapod characters. Here we report a new stem-tetrapod (Tungsenia paradoxa gen. et sp. nov.) from the Lower Devonian (Pragian, ∼409 million years ago) of China, which extends the earliest record of tetrapods by some 10 million years. Sharing many primitive features with stem-lungfishes, the new taxon further fills in the morphological gap between tetrapods and lungfishes. The X-ray tomography study of the skull depicts the plesiomorphic condition of the brain in the tetrapods. The enlargement of the cerebral hemispheres and the possible presence of the pars tuberalis in this stem-tetrapod indicate that some important brain modifications related to terrestrial life had occurred at the beginning of the tetrapod evolution, much earlier than previously thought

Pushing the boundaries: The 2014 ANZSOC conference

On 1 - 3 October 2014, the University of Sydney’s Law School hosted the 27th annual Australian and New Zealand Society of Criminology conference in Camperdown, New South Wales. As usual, the conference attracted a diverse audience of academics, researchers, and practitioners from Australia and around the globe, working in and around criminology. The theme of the conference was ‘Testing the Edges: Challenging Criminology’, and it certainly lived up to this clarion call..

A Devonian predatory fish provides insights into the early evolution of modern sarcopterygians

Crown or modern sarcopterygians (coelacanths, lungfishes, and tetrapods) differ substantially from stem sarcopterygians, such as Guiyu and Psarolepis, and a lack of transitional fossil taxa limits our understanding of the origin of the crown group. The Onychodontiformes, an enigmatic Devonian predatory fish group, seems to have characteristics of both stem and crown sarcopterygians but is difficult to place because of insufficient anatomical information. We describe the new skull material of Qingmenodus, a Pragian (similar to 409-million-year-old) onychodont from China, using high-resolution computed tomography to image internal structures of the braincase. In addition to its remarkable similarities with stem sarcopterygians in the ethmosphenoid portion, Qingmenodus exhibits coelacanth-like neurocranial features in the otic region. A phylogenetic analysis based on a revised data set unambiguously assigns onychodonts to crown sarcopterygians as stem coelacanths. Qingmenodus thus bridges the morphological gap between stem sarcopterygians and coelacanths and helps to illuminate the early evolution and diversification of crown sarcopterygians

Phylogenetic relationships of <i>Sparalepis tingi</i> gen. et sp. nov.

<p>Strict consensus (A) and 50% Majority-rule consensus (B) of the 2496 most parsimonious trees recovered in this study. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170929#pone.0170929.s002" target="_blank">S1 Fig</a> for synapomorphies at each node.</p

Summary of the Silurian sequence in Qujing (Yunnan, China), displaying the stratigraphic position of <i>Sparalepis tingi</i> gen. et sp. nov. and other vertebrate taxa of the Xiaoxiang fauna.

<p>Modified after Zhu et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170929#pone.0170929.ref008" target="_blank">8</a>].</p