Head and backbone of the Early Cambrian vertebrate Haikouichthys

Agnathan fish hold a key position in vertebrate evolution, especially regarding the origin of the head and neural-crest-derived tissue. In contrast to amphioxus, lampreys and other vertebrates possess a complex brain and placodes that contribute to well-developed eyes, as well as auditory and olfactory systems. These sensory sytems were arguably a trigger to subsequent vertebrate diversifications. However, although they are known from skeletal impressions in younger Palaeozoic agnathans, information about the earliest records of these systems has been largely wanting. Here we report numerous specimens of the Lower Cambrian vertebrate Haikouichthys ercaicunensis, until now only known from the holotype. Haikouichthys shows significant differences from other fossil agnathans: key features include a small lobate extension to the head, with eyes and possible nasal sacs, as well as what may be otic capsules. A notochord with separate vertebral elements is also identifiable. Phylogenetic analysis indicates that this fish lies within the stem-group craniates. Although Haikouichthys somewhat resembles the ammocoete larva of modern lampreys, this is because of shared general craniate characters; adult lampreys and hagfishes (the cyclostomes if monophyletic) are probably derived in many respects.     

An Early Cambrian tunicate from China

Like the Burgess Shales of Canada, the Chengjiang Lagerst?tte from the Lower Cambrian of China is renowned for the detailed preservation as fossils of delicate, soft-bodied creatures, providing an insight into the Cambrian explosion. The fossils of possible hemichordate chordates and vertebrates have attracted particular attention. Tunicates, or urochordates, comprise the most basal chordate clade, and details of their evolution could be important in understanding the sequence of character acquisition that led to the emergence of chordates and vertebrates. However, definitive fossils of tunicates from the Cambrian are scarce or debatable. Here we report a probable tunicate Cheungkongella ancestralis from the Chengjiang fauna. It resembles the extant ascidian tunicate genus Styela whose morphology could be useful in understanding the origin of the vertebrates.     

A new troodontid dinosaur from China with avian-like sleeping posture

Discovering evidence of behaviour in fossilized vertebrates is rare. Even rarer is evidence of behaviour in non-avialan dinosaurs that directly relates to stereotypical behaviour seen in extant birds (avians) and not previously predicted in non-avialan dinosaurs. Here we report the discovery of a new troodontid taxon from the Early Cretaceous Yixian Formation of western Liaoning, China. Numerous other three-dimensionally preserved vertebrate fossils have been recovered recently at this locality, including some specimens preserving behavioural information. The new troodontid preserves several features that have been implicated in avialan origins. Notably, the specimen is preserved in the stereotypical sleeping or resting posture found in extant Aves. Evidence of this behaviour outside of the crown group Aves further demonstrates that many bird features occurred early in dinosaurian evolution.     

Distribution of α-MSH-like immunoreactive cells in the nervous system, Hatschek''''s pit and other tissues of amphioxus, Branchiostoma belcheri

Immunohistochemical localization of a-melanocyte-stimulating hormone (α-MSH) in the nervous system, Hatschek's pit and other tissues of amphioxus (Branchiostoma belcheri) was performed using the antibody against synthetic α-MSH. The results revealed that α-MSH-like immunoreactive cells were distributed at the dorsal side and ventral side of brain vesicle, the dorsal side and the surrounding of nerve tube, and in the epithelial cells of Hatschek's pit, the zone 1, 3, and 6 of endostyle and gut. The immunoreactive substance was also found in the primary oocytes of the small and large growth stage of ovary and early stage spermatogenic cells in testis. These findings indicate that α-MSH is an ancient and highly conserved hormone and it is extensively distributed in amphioxus. Although Hatschek's pit in amphioxus does not have a structure of the intermediate lobe of vertebrate adenohypophysis, it has already hosted α-MSH-like endocrine cells, implying that the functional differentiation of α-MSH-like cells occurred earlier than the differentiation of the tissue structure. The results of the present study provided a new evidence for the endocrinology of Hatschek's pit and for the origin and evolution of vertebrate adenohypophysis.     

Axial patterning in cephalochordates and the evolution of the organizer

The organizer of the vertebrate gastrula is an important signalling centre that induces and patterns dorsal axial structures. Although a topic of long-standing interest, the evolutionary origin of the organizer remains unclear. Here we show that the gastrula of the cephalochordate amphioxus expresses dorsal/ventral (D/V) patterning genes (for example, bone morphogenetic proteins (BMPs), Nodal and their antagonists) in patterns reminiscent of those of their vertebrate orthlogues, and that amphioxus embryos, like those of vertebrates, are ventralized by exogenous BMP protein. In addition, Wnt-antagonists (for example, Dkks and sFRP2-like) are expressed anteriorly, whereas Wnt genes themselves are expressed posteriorly, consistent with a role for Wnt signalling in anterior/posterior (A/P) patterning. These results suggest evolutionary conservation of the mechanisms for both D/V and A/P patterning of the early gastrula. In light of recent phylogenetic analyses placing cephalochordates basally in the chordate lineage, we propose that separate signalling centres for patterning the D/V and A/P axes may be an ancestral chordate character.     

云南洞穴二须鳅属一新种

2015年10月，在云南省丘北县采到一尾二须鳅标本，经鉴定为尚未记录的新物种，以其采集地温浏乡命名为温浏二须鳅Bibarba wenliuensis sp. nov..该新种可以通过以下特征与同属的其余2个物种相区分：身体无色，无鳞片；头较小；眼睛全部退化；背鳍分枝鳍条为6；背鳍起点位于腹鳍起点之后；尾柄长为体长的25.0%；吻须较短，稍长于口角须；尾柄上下具有长而明显的鳍褶.     

Fossil jawless fish from China foreshadows early jawed vertebrate anatomy

Most living vertebrates are jawed vertebrates (gnathostomes), and the living jawless vertebrates (cyclostomes), hagfishes and lampreys, provide scarce information about the profound reorganization of the vertebrate skull during the evolutionary origin of jaws. The extinct bony jawless vertebrates, or 'ostracoderms', are regarded as precursors of jawed vertebrates and provide insight into this formative episode in vertebrate evolution. Here, using synchrotron radiation X-ray tomography, we describe the cranial anatomy of galeaspids, a 435-370-million-year-old 'ostracoderm' group from China and Vietnam. The paired nasal sacs of galeaspids are located anterolaterally in the braincase, and the hypophyseal duct opens anteriorly towards the oral cavity. These three structures (the paired nasal sacs and the hypophyseal duct) were thus already independent of each other, like in gnathostomes and unlike in cyclostomes and osteostracans (another 'ostracoderm' group), and therefore have the condition that current developmental models regard as prerequisites for the development of jaws. This indicates that the reorganization of vertebrate cranial anatomy was not driven deterministically by the evolutionary origin of jaws but occurred stepwise, ultimately allowing the rostral growth of ectomesenchyme that now characterizes gnathostome head development.     

Protochordate amphioxus is an emerging model organism for comparative immunology

Protochordate amphioxus is an extant invertebrate regarded quite recently as a basal chordate. It has a vertebrate-like body plan including a circulation system with an organization similar to that of vertebrates. However, amphioxus is less complex than vertebrates for having a genome uncomplicated by extensive genomic duplication, and lacking lymphoid organs and free circulating blood cells. Recent studies on immunity have demonstrated the presence in amphioxus of both the constituent elements of key molecules involved in adaptive immunity such as proto-major histocompatibility complex (proto-MHC), V region-containing chitin-binding protein (VCBP) and V and C domain-bearing protein (VCP), and the complement system operating via the alternative and lectin pathways resembling those seen in vertebrates. In addition, the acute phase response profile in amphioxus has been shown to be similar to that observed in vertebrates. These findings together with the relative structural and genomic simplicity make amphioxus an ideal organism for gaining insights into the origin and evolution of the vertebrate immune system, especially adaptive immunity, and the composition and mechanisms of the vertebrate innate immunity.     

Distribution of CRH-and ACTH-like immunoreactive cells in amphioxus,Branchiostoma belcheri

Immunocytochemical studies on the nervous system,Hatschek's pit,digestive tract and gonads tissues of an amphioxus(Branchiostoma belcheri)were performed using polyclonal antibodies against human corticotrophin-releasing hormone(CRH)and human adrenocorticotropin(ACTH).The results showed that many CRH-like immunoreactive neurons were distributed specifically on the dorsal side and ventral side of brain vesicle,while a few CRH-like neurons and their fibers in spinal cord.At the same time,the epithelial cells in the basic region of Hatschek's pit were shown immunopositive to CRH antibody.In gonads(ovary and testis),CRH-immunopositive substance was localized in the cytoplasm near oocyte nucleus and in early spermatogenic cells.ACTH-like immunoreactivities were observed specially in the neurons and their protrusions localized on the ventral side of the brain vesicle and in spinal cord,and also in epithelial cells of Hatschek's pit,enteric neurons of digestive tract,oocytes in ovary and in early spermatogenic cells as well.It was found for the first time that CRH-like neurons existed in the middle region of brain vesicle(corresponding to the hypothalamus of vertebrates)and ACTH-like immunopositive cells existed in Hatschek's pit,implying that a control mechanism between brain vesicle and Hatschek's pit maybe had been already built in amphioxus as that in vertebrates.The present study will provide new morphological evidence for the origin and evolution of ACTH.In addition,the immunoreactivities of CRH and ACTH in the digestive tract and gonads suggested other physiological function of CRH and ACTH in amphioxus.     

A new orang-utan relative from the Late Miocene of Thailand

The fossil record of the living great apes is poor. New fossils from undocumented areas, particularly the equatorial forested habitats of extant hominoids, are therefore crucial for understanding their origins and evolution. Two main competing hypotheses have been proposed for orang-utan origins: dental similarities support an origin from Lufengpithecus, a South Chinese and Thai Middle Miocene hominoid; facial and palatal similarities support an origin from Sivapithecus, a Miocene hominoid from the Siwaliks of Indo-Pakistan. However, materials other than teeth and faces do not support these hypotheses. Here we describe the lower jaw of a new hominoid from the Late Miocene of Thailand, Khoratpithecus piriyai gen. et sp. nov., which shares unique derived characters with orang-utans and supports a hypothesis of closer relationships with orang-utans than other known Miocene hominoids. It can therefore be considered as the closest known relative of orang-utans. Ancestors of this great ape were therefore evolving in Thailand under tropical conditions similar to those of today, in contrast with Southern China and Pakistan, where temperate or more seasonal climates appeared during the Late Miocene.     

The molecular nature of the zebrafish tail organizer

Based on grafting experiments, Mangold and Spemann showed the dorsal blastopore lip of an amphibian gastrula to be able to induce a secondary body axis. The equivalent of this organizer region has been identified in different vertebrates including teleosts. However, whereas the graft can induce ectopic head and trunk, endogenous and ectopic axes fuse in the posterior part of the body, raising the question of whether a distinct organizer region is necessary for tail development. Here we reveal, by isochronic and heterochronic transplantation, the existence of a tail organizer deriving from the ventral margin of the zebrafish embryo, which is independent of the dorsal Spemann organizer. Loss-of-function experiments reveal that bone morphogenetic protein (BMP), Nodal and Wnt8 signalling pathways are required for tail development. Moreover, stimulation of naive cells by a combination of BMP, Nodal and Wnt8 mimics the tail-organizing activity of the ventral margin and induces surrounding tissues to become tail. In contrast to induction of the vertebrate head, known to result from the triple inhibition of BMP, Nodal and Wnt, here we show that induction of the tail results from the triple stimulation of BMP, Nodal and Wnt8 signalling pathways.     

Live birth in the Devonian period

The extinct placoderm fishes were the dominant group of vertebrates throughout the Middle Palaeozoic era, yet controversy about their relationships within the gnathostomes (jawed vertebrates) is partly due to different interpretations of their reproductive biology. Here we document the oldest record of a live-bearing vertebrate in a new ptyctodontid placoderm, Materpiscis attenboroughi gen. et sp. nov., from the Late Devonian Gogo Formation of Australia (approximately 380 million years ago). The new specimen, remarkably preserved in three dimensions, contains a single, intra-uterine embryo connected by a permineralized umbilical cord. An amorphous crystalline mass near the umbilical cord possibly represents the recrystallized yolk sac. Another ptyctodont from the Gogo Formation, Austroptyctodus gardineri, also shows three small embryos inside it in the same position. Ptyctodontids have already provided the oldest definite evidence for vertebrate copulation, and the new specimens confirm that some placoderms had a remarkably advanced reproductive biology, comparable to that of some modern sharks and rays. The new discovery points to internal fertilization and viviparity in vertebrates as originating earliest within placoderms.     

Skara hunanensis a new species of Skaracarida (Crustacea) from Upper Cambrian (Furongian) of Hunan, south China

The fossils of Orsten-type preservation are as famous as Chengjiang Fauna in the world, but it was not until 2005 that the Orsten-type fossils represented by Skaracarida and Phosphatocopida were first reported to be found in western Hunan, South China. Here, we report the systematic paleontology of all the exquisitely preserved specimens belonging to Skaracarida. They were found at a same horizon of Upper Cambrian (Furongian) in Wangcun section, western Hunan, south China, assigned to a new species Skara hunanensis herein. Skara hunanensis is characterized by small, soft-integumented, marine forms with slender, annulate body; labrum large and ventrocaudally directed; uniramous antennulae; biramous antennae and mandibulae; maxillas and maxillipeds of the same shape; all postantennular limbs join a short cephalic filter apparatus. The body has two tagmata: a cephalon with five pairs of well developed appendages and a trunk composed of 11 ring-shaped conical segments.     

锚首虫科一新纪录属和一新纪录种

记述了锚首虫科Ancyrocephalidae单殖吸虫中国一新纪录属一新纪录种,即寄生在黄唇裸颊鲷Lethrinus xanthochilus 鳃上的裸颊鲷虫属Lethrinitrema Lim & Justine,2011,弓背裸颊鲷虫Lethrinitrema gibbus Lim & Justine,2011;裸颊鲷虫属的种类具2个梨形的后吸器囊,腹中央大钩具有外侧沟,后吸器囊远端延长形成分叉的管,进入每侧腹中央大钩的外侧沟.所获标本的形态结构和大小与原始描述基本一致,黄唇裸颊鲷为宿主新纪录     

A cell surface molecule distributed in a dorsoventral gradient in the perinatal rat retina

Brain topography may have its earliest expression as spatial gradients of molecules controlling the deposition of neurones and neuronal processes. In the vertebrate visual system there is evidence that the stereotyped alignment of central retinal projections relies on an initial spatially organized distribution of molecules in both the retina and its central target nuclei. We used an immunological approach to look for molecules that are so organized and produced a monoclonal antibody (JONES) which shows a pronounced dorsal to ventral gradient of binding in the rat retina throughout the period when retinal ganglion cell axons are forming topographically organized projections within the central nervous system (CNS). Binding is present throughout the radial thickness of the retinal epithelium in regions where postmitotic neurones are generated but is not associated with any consistent histological characteristic of the tissue. The antibody was shown to bind on the cell surface of freshly dissociated retinal cells, and dorsal retinal quadrants were found in vitro to have nearly twice as much antigen as ventral retinal quadrants. Initial biochemical characterization of the target epitope reveals that it is a lipid present in chloroform/methanol extracts from perinatal retina and is sensitive to neuraminidase digestion.     

鹦鹉嘴龙的研究进展及CT应用

鹦鹉嘴龙作为亚洲东部地区早白垩世时期中所特有的原始角龙类群,对研究角龙类的起源和演化有着重要意义。近年来在辽宁西部地区发现大量鹦鹉嘴龙化石,大大推进了该类恐龙的骨骼解剖学和古生物学研究。结合最新研究进展,对鹦鹉嘴龙科内的属种分异度进行了剖析,并对该科的地史地理分布特征和演化历史进行了讨论。此外,本项研究应用医学CT扫描和计算机辅助三维图像重建技术,对辽西新发现的一件完整的鹦鹉嘴龙头骨进行了CT扫描和三维图像的复原。这一手段的应用揭示了该头骨腭面的形态结构,为鹦鹉嘴龙类的解剖和生物学研究提供了新的特征信息。     

The origin of the vertebrate jaw:Intersection between developmental biology-based model and fossil evidence

The origin of the vertebrate jaw has been reviewed based on the molecular,developmental and paleontological evidences.Advances in developmental genetics have accumulated to propose the heterotopy theory of jaw evolution,i.e.the jaw evolved as a novelty through a heterotopic shift of mesenchyme-epithelial interaction.According to this theory,the disassociation of the nasohypophyseal complex is a fundamental prerequisite for the origin of the jaw,since the median position of the nasohypophyseal placode in cyclostome head development precludes the forward growth of the neural-crest-derived craniofacial ectomesenchyme.The potential impacts of this disassociation on the origin of the diplorhiny are also discussed from the molecular perspectives.Thus far,our study on the cranial anatomy of galeaspids,a 435-370-million-year-old ’ostracoderm’ group from China and northern Vietnam,has provided the earliest fossil evidence for the disassociation of nasohypophyseal complex in vertebrate phylogeny.Using Synchrotron Radiation X-ray Tomography,we further show some derivative structures of the trabeculae(e.g.orbitonasal lamina,ethmoid plate) in jawless galeaspids,which provide new insights into the reorganization of the vertebrate head before the evolutionary origin of the jaw.These anatomical observations based on new techniques highlight the possibility that galeaspids are,in many respects,a better proxy than osteostracans for reconstructing the pre-gnathostome condition of the rostral part of the braincase.The cranial anatomy of galeaspids reveals a number of derived characters uniquely shared with gnathostomes.This raises the potential possibility that galeaspids might be the closest jawless relatives of jawed vertebrates.Our study provides an intriguing example of intersection between developmental biology-based model and fossil evidence.     

Skara hunanensis a new species of Skaracarida (Crustacea) from Upper Cambrian (Furongian) of Hunan,south China

The fossils of Orsten-type preservation are as famous as Chengjiang Fauna in the world,but it was not until 2005 that the Orsten-type fossils represented by Skaraearida and Phosphatocopida were first reported to be found in western Hunan,South China. Here,we report the systematic paleontology of all the exquisitely preserved specimens belonging to Skaraearida.They were found at a same horizon of Upper Cambrian (Furongian) in Wangcun section,western Hunan,south China,assigned to a new species Skara huna- nensis herein.Skara hunanensis is characterized by small,soft-integumented,marine forms with slender,annulate body;labrum large and ventrocaudally directed;uniramous antennulae;biramous antennae and mandibulae;maxillas and maxillipeds of the same shape;all postantennular limbs join a short cephalic filter apparatus.The body has two tagmata:a cephalon with five pairs of well developed ap- pendages and a trunk composed of 11 ring-shaped conical segments.     

“圆盘青钱柳Cyclocarya scutellata Guo”论评

圆盘青钱柳Cyclocarya scutellata Guo为郭双兴(1979)建立于海南岛长昌盆地长昌组的新种,但根据果柄、果的大小以及所谓的"翅脉"等特征,作者认为郭双兴(1979)建立的"圆盘青钱柳Cyclocarya scutellata Guo"并不成立,这类标本应是莲的果实的不同保存状态,不能归入Cyclocarya.因此,郭双兴(1979)提出的关于青钱柳属可能起源于海南岛始新世的推论也就缺乏化石依据.     

BMP inhibition-driven regulation of six-3 underlies induction of newt lens regeneration

Lens regeneration in adult newts is a classic example of how cells can faithfully regenerate a complete organ through the process of transdifferentiation. After lens removal, the pigment epithelial cells of the dorsal, but not the ventral, iris dedifferentiate and then differentiate to form a new lens. Understanding how this process is regulated might provide clues about why lens regeneration does not occur in higher vertebrates. The genes six-3 and pax-6 are known to induce ectopic lenses during embryogenesis. Here we tested these genes, as well as members of the bone morphogenetic protein (BMP) pathway that regulate establishment of the dorsal-ventral axis in embryos, for their ability to induce lens regeneration. We show that the lens can be regenerated from the ventral iris when the BMP pathway is inhibited and when the iris is transfected with six-3 and treated with retinoic acid. In intact irises, six-3 is expressed at higher levels in the ventral than in the dorsal iris. During regeneration, however, only expression in the dorsal iris is significantly increased. Such an increase is seen in ventral irises only when they are induced to transdifferentiate by six-3 and retinoic acid or by BMP inhibitors. These data suggest that lens regeneration can be achieved in noncompetent adult tissues and that this regeneration occurs through a gene regulatory mechanism that is more complex than the dorsal expression of lens regeneration-specific genes.