Hou, Xian-guang. C6C35 '. Set in 9. Walcott's discovery of the Middle Cambrian Burgess Shale in cast a new light upon this richer fauna. Thirty years of intensive study by several specialists at the end of the last century have made this fossil fauna one of the best known in the geological column. Thanks to S. But what once seemed like a unique window on to the marine world of the Cambrian has since been supplemented by other discoveries no less remarkable.
Professor Hou's discovery of the Chengjiang biota in Yunnan Province, China, in proved to be a revelation equal to, or even exceeding, that provided by the fauna of the Burgess Shale. In the first place it was even older, taking us still closer to what has been described as the "big bang" at the dawn of complex animal life. Third, an even greater variety of organisms was preserved-some, evidently, related to Burgess Shale forms, but others with peculiarities all of their own. The fauna included what have been claimed as the earliest vertebrates sensu lata and thus has more than a passing claim to interest in our own anthropocentric species.
There are arthropods beyond imagining, "worms" of several phyla, large predators, and lumbering lobopods; while the trilobites, so long regarded as the archetypal Cambrian organism, are just one among many successful groups of animals.
This was a richly varied biota. This book brings together marvellous color photographs to provide us with an album of Cambrian life. It is the first comprehensive "field guide" to the Chengjiang fauna. Think of it as the equivalent of one of those manuals people take to the Great Barrier Reef to identify the marine life- but here the seafloor is million years old.
It is a world full of surprises. The velvet worms-today represented by tropical terrestrial animals-were then much more diverse, some of them plated, spiky, odd-looking creatures. Marvel at the preservation of the comb jelly, the most delicate of marine organisms, destroyed today by the glance of an oar, but here preserved for hundreds of millions of years in almost incredible detail.
Worms seem almost to be laid out upon the dissecting slab ready for inspection. This book is much more than a mere picture gallery. If so, what are the implications for genetic development? Could permutations in the expression of homeobox genes be responsible for the apparently rapid diversification of these animals?
One thing is certain: the evidence from China will be forever built into the scientific edifice. Or you can, if you prefer, take a delight in the aesthetic qualities of the images. Its principal concern is to bring to life worlds that would otherwise lie forgotten and undiscovered within the rocks. The abundant and exquisite fossils, preserving fine details of the hard parts and soft tissues of animals and primitive plants approximately million years old, are simply wondrous objects in their own right.
More significantly, they are vital keys in helping to unravel the evolution of multicellular organisms during a period of time when such life forms first become common in the fossil record. Much of the primary documentation is in Chinese. The number of species known from the Chengjiang biota easily exceeds It was not intended that every known species should be treated herein.
We have simply provided a selection, with phyla ordered in accordance with the phylogeny of Nielsen , to illustrate the range and nature of the biota. The systematic position of many Chengjiang species within their phyla is controversial and has in some cases attracted widely different opinions.
It is hoped that with the publication of this book the sheer beauty, diversity and scientific importance of these fossils from southwestern China will become more widely known and appreciated by scientists and the public at large. We are indebted to Professor Derek Briggs YaleUniversity for his constructive review of the manuscript. Thanks also to the staff at, or those associated with, Blackwell Publishing Oxford who were involved in bringing this book to fruition: Ian Francis for accepting the outline proposal, Delia Sandford the managing editor, and Jane Andrew, Cee Brandson, Jo Egre, and Rosie Hayden for their various editorial inputs.
Certain specimens have been illustrated previously in the scientific literature, but one of us Derek J. We have no direct record of Earth history for the first million years or so, but rocks have been found that date at least as far back as 3, million years, and perhaps even more than 4, million years. Earth history has been divided up into three eons: the Archean, the Proterozoic, and the Phanerozoic Fig. The Proterozoic is divided into three periods, the Paleoproterozoic 2,, million years , the Mesoproterozoic 1,, million years , and the Neoproterozoic 1, million years.
The earliest periodof the Phanerozoic eon is called the Cambrian, after the old Latin name for Wales, and it was during this time that almost all the animal groups we now know on Earth made their initial appearances. Some of the most important fossil evidence for these originations has come from the Chengjiang biotaof southwestChina -the subject of this book. The record of life on Earth, however, goes much further back in time, perhaps nearly as far as the record of the rocks. Possible microfossils that resemble cyanobacteria have been reported from rocks as old as 3, million years in Australia Schopf and there is circumstantial evidence from geochemical studies that carbon isotopes were being fractionated by organic processes as long ago as 3, million years Mojzsiset al.
However, there is a need to treat these reports of evidence for very early life with caution, and the further back in time the record is extended the more controversial the claims become see, for example, Brasier et al. It is quite probable, however, that fossils are present in rocks of Archean age, albeit extremely rarely. The resulting forms are commonly dome-like or columnar, and these characteristic shapes can also be recognized in Archean sediments up to 3, million years in age.
Records Brocks et al. Bronikov and Dimitri Grazhdankin. This diversification of eukaryotes continued through the Neoproterozoic. The embryos are consistently about half a millimeter in diameter, compartmentalized into two, four, eight, or more internal bodies Fig. Metazoa are characterized by the grouping together of numerous cells, with different sets of cells fulfilling different specialized functions. Molecular clock calculations, which assume a regular substitution rate within selected genes, suggest that divergence of the metazoans occurred more than 1, million years ago Wray et al.
In fact, the earliest undoubted metazoan body fossils are of about the same age as the Doushantuo embryos. These are part of the Ediacaran biota, named after sites in the Ediacara Hills of South Australia, where diverse macrofossils have been extensively studied. Ediacaran fossils are now known from more than 30 localities worldwide.
Among the earliest fossils that have been allocated to this assemblage are unomamented discs and rings that have been found in the Mackenzie Mountains of Canada Narbonne et al. The main Ediacaran organisms, however, are 6 found in rocks spanning an interval from about to million years ago, immediately above tillites that record the most extensive glacial episode in Earth history.
Many workers have related the variety of soft-bodied forms found in these strata to well-known animal phyla, principally the Cnidaria, Annelida, Mollusca, Arthropoda, and Echinodermata. More recently, Seilacheretal.
Whatever their relationships, the Ediacaran taxa almost all disappeared by the beginning of the Cambrian, with just a few specimens in Cambrian strata suggesting that these forms persisted for a while alongside their more fmniliar successors. Several of these, particularly the earlier ones, are controversial, but trace fossil assemblages are clearly recognizable in strata coeval with the Ediacaran biotas, and in CHAPTERl strata that are perhaps slightly older than the diverse Ediacaran assemblages. Mostly, these traces are simple tracks and horizontal burrows, with some meandering grazing structures, but there appears to have been insufficient activity to cause complete reworking bioturbation of the sediment.
There are recent claims of much older trace-like fossils from Western Australia, where parallel pairs of ridges, straight or curved, occur in rocks dated as more than 1, million years old Rasmussen et al. Intriguingly, these traces are associated with discoidal imprints that are possibly of biogenic origin and might represent the earliest Ediacara-type fossils discovered to date.
In essence all of the major groups of life that are known from the present day can be traced back to the Cambrian. Briggs et al. The Chengjiang biota Fig. Some authors conclude that the explosion is real Conway Morris a. In support of the latter opinion it has been argued that the presence in the Early Cambrian of relatively advanced forms of, for example, arthropods e. Siveteret al. The first soft-bodied fossils to be found were from Maotianshan Maotian Hill; Fig. From the pioneer days of geological exploration in China it had been appreciated that the Lower Cambrian of eastern Yunnan Province is richly fossiliferous.
Indeed, the sequence has long been taken as a standard for the stratigraphic subdivision and correlation of the Cambrian, not only within the Southwest China Yangtze Platform but also throughout China and beyond. That the Kunming-Chengjiang area is especially rich in bradoriids was elucidated much earlier, by Professor Yang Zui-yi, during the s see Ho As a consequence of hostilities within China, Yang's Department of Geology at Zhongshan University had moved from Guangzhou City in Guangdong Province to the village of Donglongtan, situated about 55 km southeast of Kunming and a mere 1.
Following fieldwork in Jinning County southwest of Kunming, Hou Xian-guang had travelled to Chengjiang town and then on by cart to the nearby small village of Dapotou, where a team from the Geological Bureau of Yunnan Province was living, prospecting for phosphorite deposits in the Lower Cambrian. The mudstone blocks that the farm worker dug out at Maotianshan were scoured for bradoriids.
Work was notably easier than at Dapotou and Hongjiachong, because the rock was strongly weathered. At about three o'clock in the afternoon of Sunday July 1, a semicircular white film was discovered in a split slab, and was mistakenly thought to represent the valve of an unknown crustacean. With the realization that this and a second, subelliptical exoskeleton represented a previously unreported species, breaking of the rock in a search for additional fossils continued apace.
A section on the facing west slope of the hill, below the wooded area, where the Chengjiang biota was discovered. Figure 3. As recalled by Hou Xian-guang, the specimen with appendages subsequently selected as the holotype of the arthropod Naraoia longicaudata Fig. Elated by the discovery, the searchers increased their efforts and other new soft-bodied fossils were revealed one after another. Hou's field diary for that day signaled the significance of his discovery by alluding to the Burgess Shale fauna: "The discovery of fossils in the Phyllopod Bed" Fig.
These terms were subsequently applied to three small quarries that were opened up for collecting. The mudstone of level M2 is 5 m thick and yields many species of the Chengjiang fauna; in general the number of taxa and specimens successively decreases through levels M3 and M4. Jinning some material reported by Zhang a and other trilobites from Maotianshan Zhang b , and the discovery and collection of many fossils with preserved soft parts e.
By the time of his next visit, from April to June , logistics had changed. With the support of the directors of the Nanjing Institute of Geology and Paleontology, a third field season was undertaken throughout October to December For part of this period Hou Xian-guang was joined by Chen Luan-sheng, the custodian of fossils at the museum in the Nanjing Institute. From April to September , further large-scale collecting took place, again supported by Academia Sinica, when work was concentrated mainly at Maotianshan and Jianbaobaoshan near Dapotou village.
Hou's colleagues, Chen Figure 3. Jun-yuan, Zhou Gui-qing and Zhang Jun-ming, joined the field group at that time but they left in early May and June respectively for other duties. Additional collections were made by Hou Xian-guang in November and April-May , especially from new sections such as those at nearby Fengkoushao, Xiaolantian Figs 3.
In particular, Chen Jun-yuan Nanjing Institute of Geology and Palaeontology and Shu De-gan North-west University, Xian and other Chinese scientists and their collaborators have made considerable additions to the literature on the biota see References. Sediments of the Heilinpu Formation accumulated in shallow marine conditions and overlie thick phosphorites of the upper part of the Yuhucan Formation. T he Chengjiang Lagerstatte occurs in a biozone characterized by the trilobite genera Eoredlichia and Wutingaspis, which succeeds the Parabadiella Biozone, so named after the oldest known trilobite in Yunnan Province.
The biota is therefore slightly older than, or perhaps coeval with, the Sirius Passett Lagerstatte from the Lower Cambrian of Greenland and is approximately million years old. The Yu'anshan Member occurs widely in a sedimentary basin that extends over tens of thousands of square kilometers and the Chengjiang biota is now known from many areas of eastern Yunnan Province Fig.
Figs 4. Specimens from Kanfuqing village, in Malong County, include appendages of the large carnivore Anomalocaris and are purported to be from the Canglangpu Formation, which overlies the Heilinpu Formation. In this scenario the mudstones yielding the soft-bodied biota are interpreted as distal marine deposits that in part reflect episodic turbidity current activity Lindstrom , and the upper, more sandy and silty levels are said to be prodelta deposits that accumulated prior to the delta-front basal Canglangpu sands.
Palaeolenus Sichuanolenus -Paokannia Metaredlichioides -Chengkouia 0 !. Drepanuroides z - Yiliangella cr: co E. Barren inlerval z a: al Guanshan Member c: 0. Formation Canglangpu Formation? The arrow indicates the stratigraphic position of the Chengjiang biota. Major radiation of small shelly fauna Figure4. The oldest lithofacies 1 , consisting of laminated siltstones with high organic carbon content, is thought to reflect deposition in shallow, oxygen-poor waters, early in the transgressive phase.
The very fine grain of the rock has allowed the details of the fossils to be preserved with remarkable fidelity, although the processes that led to this preservation are currently poorly understood. Most of the fossils are in the form of flat, or nearly flat, impressions, although some retain a low three-dimensional relief. These impressions are sometimes dark in color, perhaps due to the presence of carbon, left behind as the original complex organic tissues degraded.
These include the relatively tough cuticle of arthropods, which was probably similar to the outer skeleton of modem prawns, and truly soft tissues such as muscles, gills and intestines. These soft tissues would normally decay away very rap- idly and disappear within a few weeks, or even days, of death. Many of the animals found in the Chengjiang fauna had no biomineralized skeleton at all and would not normally leave any trace in the fossil record.
The high quality of preservation of soft tissues in the Chengjiang muds is commonly taken as an indication that the sediment in which they are found must have been starved of oxygen e. Babcock et al. Indeed, some specimens clearly are found exactly where they lived. This is the case, for example, with some of the lingulid brachiopods, which are preserved with their shells lying flat on the bedding planes and their long pedicles extending obliquely down into the sediment below Hou et al.
It is likely that the animals were rapidly killed by asphyxia, although there is a difference of opinion as to whether this was caused by benthic sediment flows or by the incursion of anoxic waters see Hagadorn Figure 5. The appearance of the fossils also varies with the orientation in which the dead animal rested on the sediment before it became compressed. This fact also supports the conclusion that the carcasses suffered only gentle transport before being buried.
Naraoia sp. In such circumstances we may, for instance, find evidence of the animals' food in their guts. Dead shells lying on the sediment may have provided sites for secure attachment of some individuals e. Archotuba and the brachiopod Longtancunella. Overall, the Chengjiang biota is remarkably diverse. Well over animal species have been reported, referable to several major groups Fig.
The majority of the animals were bottom-dwellers, with infaunal and epifaunal niches occupied by a variety of forms. Burrowers included the priapulid worms and the enigmatic Facivermis. In addition to these groups, a possible annelid was illustrated by Chen et al. Among the more enigmatic sessile forms, the chancelloriid Allonnia may also have been a filter feeder, and the stemmed Dinomischus also The Some of the arthropods, such as sponges, chancelloriids and data, were equipped with spinose gnathobases Dinomischus were erals quartz and muscovite Hou et al.
The anomalocarids dwellers. It has been suggested that they may were clearly fearsome predators, with large limbs have been predators and scavengers, feeding at the front of the head to capture prey. Some on sponges and other soft-bodied animals e. The water above the seabed was colonized b y a grasping food. Evidence for predation also comes from the The floaters are represented by the comb jellies occurrence of supposed fossil feces coprolites ctenophores , and perhaps by the medusoid-like containing the remains of arthropod cuticle.
Some oddities, Eldonia and Rotadiscus. Dzik et al. Trophic groups present include predators, scavengers, high and low level filterers and, it seems likely, deposit feeders. Apart from 28 modes comparable to that seen in modern seas. A general difference from the photosynthetic mosses and tracheate plants is that they live in water. Photosynthesis is concentrated in colored organelles, the plastids, and there are three main groups of algae named after the particular color present-the red algae, the green algae, and the brown group.
All of these algae are nucleate, eukaryotic organisms. Formerly a fourth group was included, the blue-green algae. These are now recognized as being anucleate prokaryotes and are commonly called cyanobacteria. The term "algae" does not have any phylogenetic meaning but rather indicates an algal mode of life. Remains of both unicellular and multicellular algae have been found in the Precambrian, but it is often difficult to place them in particular algal groups.
This is so with the four algal species, all thread-like apparently multicellular forms, that have been recorded from the Chengjiang Cambrian deposits: Megaspirellus houi, Sinocylindra yunnanensis, and Yuknessia sp. It is tightly helicoidal along its length, and so when flattened has a beaded appearance.
This species is the most abundant alga of those occurring at Chengjiang. Some specimens, at least, have been figured under the name Yuknessia Chen et al. Organs and a nervous system are absent and the few types of cells that they have are not organized into tissues. Their form varies from simple bag-shaped to stalked and elaborately branching colonies. In life they are sedentary and benthic. They filter feed from water currents pumped through minute holes ostia that lead to cavities lined with flagella-bearing cells choanocytes and thence to an interior cavity or water canal system spongocoel or atrium ; water is passed out via an apical opening osculum.
Most poriferans are shallow marine dwellers; there are also fresh-water and deep-water species. Today the latter include most of the hexactinellids, the glass sponges with their skeleton of opaline silica spicules. Sponge spicules and skeletons are common as fossils from the Cambrian onwards. Specimens are small, some mm high. The sponge body is oval to rounded and thin walled, with spongocoel constituting most of the space. The skeleton contains two moderately well organized series of small, delicate spicules with rectangular patterns.
One series of spicules has its prominent spicule axes parallel and normal to the principal axis of the sponge, and the second series has a more diagonal arrangement. This species is considered to be an early reticulosid hexactinellid sponge. Its root tuft presumably anchored the body to the substrate, as is characteristic of many Recent forms of glass sponge. Key References 34 Steiner eta1. Specimens from Yunnan Province are preserved as impressions, in low bas-relief.
This sponge has a moderately small, well-defined, almost circular body up to 3 em by 4 cm in diameter. An oscular opening is not seen, though a flattened part of its outline may be the margin of the osculum.
The skeleton consists mainly of very narrow diactine spicules, mm long and about 0. The spicules occur as dense, semiparallel, almost plumose bundles, and do not project beyond the outer margin of the sponge body. Less common, somewhat thicker spicules, up to 0. The spicules may include three-, four-, or even six-rayed hexactine forms.
Many Recent hexactinellids have a basal cluster of siliceous fibers for anchorage, but a root tuft is not evident in this species. The original specimens of S. Key References 36 Steiner etal. The type material occurs as limonite replacements of thin, spicular, vertically and diagonally flattened skeletons. In overall form the species is small and discoidal to low and broad shield-shaped or funnel-shaped.
Other than as a minor fringe, the spicules do not project beyond the margin of the disc. The genus Choiaella is monotypic. Comparisons between this skeletal pattern and that of the Recent sponge Radiella suggest that C. This species is known only from localities in the Chengjiang area. The body has a low, conical-shaped central disc up to 2cm in diameter, composed of short, thin monaxon single axis spicules that combine to give a thatch-like appearance.
Radiating from the disc there is a plethora of slender and discrete monaxon spicules, some of which are longer than the diameter of the disc itself. Choia is the type genus of the demosponge Family Choiidae. The Recent infaunal sponge Radiella, in which the skeleton is an upward and outward radiating structure, provides a possible model for Choia.
Another reconstruction has Choia resting on the sediment with spicules radiating upward and outward in many directions from the disc, in pin-cushion fashion Conway Morris References Figure 8. The type material consists of fairly complete and fragmentary limonite impression fossils that have replaced thin spicular skeletons. The body is relatively small the holotype is 14mm by lOmm and elongate ovate to sausage-shape in overall form.
Some parts of the central area of the holotype skeleton are more open-textured. The demosponge genus Allantospongia is assigned to the Family Choiidae and is known only from a single species. The life orientation of A. The species is unknown outside the Chengjiang biota.
Specimens range up to llOmm long and about 12mm wide. The body is very elongate, tube-shaped and composed of two skeletal layers, each with single-axis monaxon spicules. The dominant, outer layer consists of a vertical thatch of fine and larger spicules, which in some specimens are slightly smaller in the lower half of the skeleton.
The inner skeletal layer consists of tiny, more poorly defined, horizontally arranged spicules. A short fringe of spicules extends beyond the oscular margin. Leptomitus is the type genus of the Family Leptomitidae and is generally recognized to represent the stock from which a variety of demosponges evolved Rigby 1 In life L. A larger Leptomitus species occurs in the Burgess Shale Rigby 1 Key References 44 Rigby , Chen et al.
Specimens are flattened and have an overall conical shape a few centimeters long. The sponge body is thin-walled. The skeleton is composed of single-axis monaxon spicules arranged in two layers. The outer layer consists of a vertical thatch of fine spicules and associated vertical rods. In life it was attached to the substrate at its narrow end. Middle Cambrian of Utah. Leptomitella was originally described from the L.
Key References 46 Rigbyl,Chenetal. The fossils are flattened, and have a maximum width of 12 mm. The base of the sponge is narrow, and the oscular margin seems to be rounded. Its double-layered skeleton is formed of single-axis monaxon spicules. The outer layer consists of coarse, slightly curved oxeas monaxons having two rays, with both ends pointed that interlock with one another to form tapering, elongate areas filled with fine, vertically arranged spicules.
Bundles of horizontally arranged spicules make up the inner layer. It is assumed that P. The species has been found only in the Chengjiang biota. Key Chenet al. The lower part is elongate and tubular, some 5 mm wide, above which it expands into a balloon-like shape of around 15 mm maximum width, with a much narrower osculum.
Both layers of the skeleton consist of single-axis monaxon spicules. The outer layer has an interweaving of slightly curved, coarse oxeas monaxons having two rays, with both ends pointed , between which there is a network of fine, vertical spicules. The inner skeletal layer is comprised of fine horizontal spicules arranged in bundles. It presumably lived attached to the seafloor, by its narrow end.
Key References 50 Chenet al. The skeleton consists of four layers of single-axis monaxon spicules, arranged into two nets each of two layers. The spicules of the outermost layer are coarse, relatively widely spaced and extend virtually the entire length of the sponge; those of the second layer are finer, more closely spaced and horizontal. The spicules of the two layers of the inner net trend diagonally in opposite directions.
Quadrolaminiella is the only known genus of the Family Quadrolaminiellidae. The life position of Q. It is one of two Quadrolaminiella species, both of which are found only in the Chengjiang biota. Key Chen etai. Thus, these diploblastic metazoans differ fundamentally in body plan from other metazoans, which are characterized by having three body wall layers triploblastic and bilateral symmetry. Most cnidarians are marine dwellers. A pelagic larval stage the medusa is common, but as adults most cnidarians are benthic and anchored, with the polyps collecting food with tentacles that ring the mouth.
Most specimens are preserved laterally collapsed; a few are compressed dorsoventrally, giving an overall flower-like appearance to the fossil. The animal appears to be approximately cylindrical, is typically about 60 mm high and has a maximum width of 30 mm at its base. It consists of a seemingly smooth pedal disc, a column with external strip-like longitudinal structures, extending into a series of about 16 strip-like or tentacular structures forming a flexible ring around what is assumed to be a centrally positioned mouth.
Each tentacle appears to taper gradually to a point. Both ctenophores and a possible sea anemone, Walcott's lb Mackenzia costalis, have been identified from the Burgess Shale. Figure 9. All Recent forms, some 90 species, are marine. At one end of the typically spherical body there is a centrally positioned mouth. Many species have a pair of long, branched, contractile tentacles. Food is captured either by direct engulfment into the mouth, or by first entrapping the prey on the sticky tentacles. Ctenophores are triplobasts and although not bilateral animals they do have some cell and tissue characteristics akin to those of the Bilateria.
The fossils are preserved in two dimensions in lateral aspect. The body is, overall, spherical in shape in lateral view. These delicate features are interpreted as the combs of comb rows. The lobes converge toward each other and meet in a small button-like dome at what is presumed to be the aboral end. This species bears a compelling resemblance to Recent ctenophores. Cambrian ctenophores apparently have many more than the eight comb rows characteristic of their Recent counterparts. There are 16 rows in M. The supposed Chengjiang cnidarian Xianguangia sinica, also has longitudinally arranged strip-like tentacular structures that are 16 in number.
References Figure Figure Except for the pelagic swimmer Nectonema, which lives in marine waters, all Recent nematomorphs inhabit fresh water. In some cases its sclerites are preserved in slight relief. The reddish colored preservation that is typical of the fossils contrasts with the generally lighter, buff hue of the host rock.
Large specimens are about 50mm long and 2. The fact that many specimens of this worm have a gut filled with mud suggests that it may have been an infaunal deposit feeder. Zhao et al. This species is also illustrated in the frontispiece. It occurs as complete and fragmentary compression fossils, consisting of soft parts and embedded biomineralized elements. Many specimens are coiled. Externally each annulus bears a double transverse row of tiny ! The gut is preserved as a fairly straight, dark band.
Isolated palaeoscolecidan sclerites may be represented in the fossil record by the hadimopanellids and like forms, a range of small, button-like phosphatic Cambrian microfossils. According to one notion, palaeoscolecids may in essence be armored priapulids and possibly provide a link between that group and the arthropods and other phyla that molt their cuticle see Conway Morris Most palaeoscolecidans may have been infaunal. However, the gut in P.https://tlochusena.ml
A window on early animal evolution
Specimens occur as flattened body fossils, typically parallel to bedding. The largest individuals are about 40mm long and 2mm wide. The relatively slender trunk has slightly convex, narrow annuli permm , each covered with many tiny pits that are assumed to represent the site of sclerites.
The furrows delimiting the annuli have similar irregularly distributed pits. Similar structures are found in the Chengjiang worms Cricocosmia jinningensis and Palaeoscolex sinensis. The intestine is long, narrow and straight and is preserved as a dark film, with slight relief in some specimens. Some authors consider Maotianshania to be a palaeoscolecid and ally that group to nematomorph worms e. Many specimens show a mud-filled intestine, indicating that M.
Simple tubular burrows and trails in the host mudstone probably attest to the activities of various shelf-dwelling worms. The proboscis bears a terminal mouth and has many tiny cone-shaped external projections scalids arranged in transverse or longitudinal rows. In some species the trunk bears tiny spines and also posterior extensions that are used to anchor the worm to the substrate.
Based on molecular sequence and other data, priapulids have been allied with the arthropods and nematodes in a major grouping of triploblastic animals that molt their cuticle, called ecdysozoans Aguinaldo et al. The monophyly of the Priapulida has been unambiguously supported Wills b. Individuals are less than 10mm long. The anterior proboscis and the posterior trunk are approximately equal in size and oval-shaped in lateral view.
The trunk was possibly encased in a kind of thick cuticle, as is the case in some Recent priapulid larvae, where such cuticle is called the lorica. The gut is typically narrow and straight, but in one specimen it is curved near the posterior end of the trunk, a region surrounded by hooks. Priapulites Schram, , from the Carboniferous of Illinois, has a similar general morphology. There is no direct evidence to indicate whether it was a predatorial carnivore or a digester of sediment. The species is known only from the Lower Cambrian of Yunnan Province. Key References Conway Morris a, Hou et al.
The material consists of delicate, soft-bodied compression fossils, including complete individuals, which are detected mainly by subtle color differences against the rock matrix. The largest individuals are about lOmm long. The anterior proboscis and the short, elongate oval-shaped posterior trunk are of subequal size. When preserved everted the narrower, anterior part pharynx of the proboscis is seen to bear a regular array of tiny spines, as does the broader base of the proboscis. The trunk has a series of longitudinal external ridges, of which are visible in one specimen.
The internal part of the trunk is occupied almost entirely by what is interpreted as a multi-coiled gut. The small size of P haikouensis and P parvus, noticeable especially in the length of the trunk, contrasts with most other Recent and fossil priapulids. The Chengjiang biota species Sicyophorus rarus, from Haikou, originally described under uncertain taxonomic affinity, is probably a synonym of P.
It is likely that P haikouensis was a burrower, but possibly not a predator. As alluded to by its name, this worm was originally collected from the Lower Cambrian near Haikou. It is unknown elsewhere. Key Reference 66 Hou et al. O; Mafang. Specimens are preserved as flat impressions and many show a clear longitudinal gut trace.
Specimens are up to 45 mm long and 9 mm wide, and were probably cylindrical in life. Papillae are evident in the anterior and posterior portions of the body, regularly spaced and symmetrical across the trunk; there is also an ornament of fine spines. The gut is straight, has a striated surface and occupies a third of the width of the trunk. The gut appears to be offset from the mid-line at the posterior end, perhaps indicating a posteroventral opening. Though more circumspect about its affinity, Hou et al.
Some specimens of A. Some individuals have a broader alimentary canal, which the original authors interpreted as food filling, and this may indicate that A. The monospecific Acosmia is unknown outside the Chengjiang Lagerstatte. The fossils typically consist of an outer tube from which protrudes a spiny proboscis. Both the soft parts and the more decay-resistant organic tube are preserved as compression fossils. In some specimens the proboscis is fully everted and is clearly divided transversely into several parts, each characterized by spines of a particular size and array.
The narrow, elongate tapering tube, which presumably housed the trunk of the animal, has a total length of about 20mm and a width of about 3mm. The surface of the tube displays fine, regularly spaced annulations, representing incremental growth. The monotypic Paraselkirkia is a member of the Selkirkiidae, a family established on Burgess Shale material. The Chengjiang worm Selkirkia sinica bears close resemblance to P. It is reasonable to assume that P. It may have been orientated vertically in the sediment or arranged head-down at various angles with the posterior-most tip of the tube projecting into the water to facilitate waste disposal see Briggs et al.
The tube is elongate cone-shaped, with a maximum length of just over 50 rnm and a maximum diameter of over 6 mm. Most specimens lack any sign of ornament, but a few specimens show surface annulations, presumably representing marginal incremental growth. A dark axial structure along the middle part of some tubes may indicate the trace of the intestine Hou et al. There are examples in which several of these tubes have been found together, orientated subparallel with their apices emanating from near one another and in some cases touching, as if fixed, to a brachiopod, hyolithid or other type of shell.
In contrast, others have interpreted this species as a sessile benthic cnidarian Cambrorhytium sp. The Chengjiang taxon Selkirkia? All known occurrences of A. Key References 72 Chen et a1. Some authors regard them as a separate phylum. Two main groups have been recognized, namely the hyolithids and the orthothecids Marek Both the conch and operculum bear a variety of muscle scars. Hyolithids are generally considered to have lived on the substrate, resting on the flatter side of the shell for stability. The helens might also have aided stability in soft sediment and could perhaps have been used to facilitate what was possibly a slow, labored form of locomotion.
Many species appear to have favored living on mud substrates. Genus Linevitus Syssoiev, Linevitus opimus Yu, This relatively rare hyolithid species is known from the remains of its thin, mineralized shells, which typically are preserved flattened but retaining slight relief. The elongate, cone-shaped conch is up to 15mm wide at its apertural end and up to 30mm long, tapering gradually to a sharp apex.
The dorsal side is slightly convex and has a central longitudinal groove that tapers from aperture to apex. It may be more common at other horizons locally. Key References 74 Yu ,Hou etal. They are normally preserved flattened yet retaining an overall cone shape and, in some cases, weak relief. Of all the Chengjiang hyolithids, this species has the largest shell.
It attains a length of up to 35 mm and is up to 15 mm wide at the apertural end. The shell surface has weak growth lines parallel to the apertural margin, but lacks any form of longitudinal ornament. The Chengjiang hyolithid Glossolites magnus is closely similar to B. All known occurrences of B. The shell is elongate, cone-shaped and has straight sides. It has a maximum length of 16mm and its maximum width at the aperture is 6mm; the apex is somewhat obtuse.
Key References 78 Jiang , Chen et al. The moldic shells, originally composed of calcium carbonate, are preserved flattened with some slight relief. Soft parts are unknown. The cone-shaped shell has straight sides, a sharply pointed apex and is relatively small. The largest specimens are only about 5 mm long and 1. The external part of the shell has narrow dense growth lines, some per millimeter. A central longitudinal groove, representing a probable post-mortem "collapse" feature, is common. Key References 80 Qian , Hou et al. Their vermiform body, consisting of soft tissue and lightly sclerotized cuticle, bears uniramous appendages.
Lobopodians have been allied in particular with arthropods, figuring prominently in assessments of the origins and relationships of this major invertebrate group. Most fossil lobopodians were marine and they are known almost entirely from Cambrian rocks, the only others being from Carboniferous and Tait Tertiary deposits. Some 20 named and unnamed lobopodian species are known from the fossil record. Six named genera, each with a single species, come from the Cambrian of Yunnan Province, making it the richest source of fossil lobopodians.
Another new but as yet undescribed form has recently been reported from the province Zhang et al. It was originally described on the basis of a matching part and counterpart; subsequently five further specimens have been recovered. Specimens are preserved as essentially flattened impressions, though with some slight relief. The length of complete specimens is estimated to be about 15mm. The head is rounded and slightly elongate, separated from the trunk by a slight constriction. There are 16 pairs of annulated legs, on some of which four or five claws have been identified.
A raised structure on the dorsal mid-line between some pairs may be a third sclerite. Many of the annuli carry small nodes. Traces of the gut are evident. This association, together with its possession of clawed legs, has led to the suggestion that it crawled up and preyed on them -a lifestyle like that envisaged for Aysheaia. Photographs of the latter type of specimen are, for the first time, included here; the material will be fully descr ibed elsewhere Hou et al.
The first -described specimens have been compacted to a single extremely thin layer, with very low relief present in the claws and trunk annuli. Specimens can reach at least 80 mm in length. The head tapers anteriorly to a rounded margin, and the mouth is indicated in a terminal or near-terminal position. Fine annuli are present on the trunk, which otherwise is rather featureless, lacking any papillae or paired sclerites. An approximately centrally positioned gut r uns along the whole length of the body, though its position shows variability that probably reflects the post-mortem decay of supporting soft tissue.
The trunk is considerably extended behind the last leg pair, of which nine have now been recognized. Circular structures positioned low on the side of the trunk in the original specimens have been interpreted as leg attachment sites. Each of the legs has two broadly based, sharp claws.
Just one species of Paucipodia has been described. In particular Paucipodia is found on or near specimens of Eldonia, this occurrence probably representing a life association. Its claws would cer tainly aid attachment, and they were perhaps also used on prey or carr ion. The Chengjiang area yielded the initial finds of P. Key References Chen et al. Specimens are flattened, and sometimes show very slight relief, including a three-dimensionally preserved gut. Complete, large specimens are about 20mm long. The trunk is long, slender, tapering slightlyanteriorly and posteriorly and annulated.
Complete specimens have 23 to 25 angular, paired sclerites with raised marginal ridges regularly placed along the trunk. Sclerite morphology varies: in smaller specimens they are ventrally pointing, narrow V-shaped structures, and in larger adults they are more shield-like. Ventrally, beneath each of the successive sclerite pairs, there is a pair oflegs. The posterior trunk termination behind the last plate pair is blunt.
The gut trace is dark colored and extends along the length of the animal. Paucipodia is also included in this group, though unlike the others it lacks paired sclerites. As with the other lobopodians, Cardiodictyon is interpreted as part of the epibenthos. It is unknown outside Yunnan Province. Key Hou et al. A further 15 have been reported subsequently, but not fully described or interpreted.
One fairly complete specimen of this species is about 22mm long.
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Immediately behind the head there are two pairs of long, slender, annulated appendages that are positioned close together. A pair of curved claws may be present on each leg. Each sclerite has a base that supports a moderately long spine. Posterior to the seventh sclerite and leg pair, there is an eighth leg pair without a corresponding sclerite pair.
The trunk tapers posteriorly. Short sections of the gut are preserved in some specimens. Hallucigenia contains one other known species, H. Revision of Canadia sparsa saw it placed as the type species of Hallucigenia, a genus initially interpreted as of enigmatic affinitybefore its true identity as a lobopodian became recognized. An epibenthic, crawling mode of life is envisaged for Hallucigenia. Many retain their gut - an indication that they are not molts. Specimens range from less than 10mm to about 77 mm long.
The trunk is cylindrical. Interpretations differ as to which is the anterior, head end, and which is the posterior end. One end is long and narrow and tapers to a rounded termination, the other is very short and terminates in a small projection. There are nine pairs of trunk sclerites. Their size and shape are variable on a single specimen: relatively small and dorsoventrally compressed, round, ovoid or more rhomboidal.
The surface of each plate has hexagonal, cylindrical perforations and spiky nodes. The trunk areas that bear the plate pairs are smooth and dorsally swollen, and between them the body is annulated. All appendages have a central canal and two distal claws. Microdictyon was first established on the basis of isolated, phosphatic net-like plates of the then enigmatic M. The later discovery of Microdictyon sinicum showed that similar plates formed part of a lobopodian. Also, its net-like sclerites have been likened to compound eyes and, possibly, to be homologous with arthropod eyes Dzik All records outside China are based on sclerites.
Key Chen et al. At least 15 specimens are known. Like the other lobopodians, Onychodictyon was mostly soft-bodied or lightly sclerotized, and its fossil remains are now in the form of largely flattened impressions. This relatively large lobopodian reaches up to about 70 mm in length and 5 mm in width.
Each plate shows fine reticulate granulation, has an outer ridge and bears a sharp, dorsally directed spine. The plate shape varies from subrectangular posteriorly to more elongate and subrounded anteriorly. Beneath each plate pair there is a pair of legs, and posteriorly there is an eleventh leg pair for which a corresponding plate pair has not been identified. Each of these legs is annulated and bears small appendicules and two large, curved claws.
Anterior to the leg pair that is associated with the first plate pair, there is another pair of annulated, claw-bearing legs. These two most anterior leg pairs appear to be somewhat shorter than the others. The trunk also has very long, clearly annulated appendicules ventrally; posteriorly it does not extend beyond the last eleventh leg pair.
A linear gut trace is present, as are centrally positioned lines of uncertain nature along each leg. Onychodictyon contains just 0. The claws of Onychodictyon clearly had an attachment function, endorsing the notion that it was more adapted to crawling on other organisms than on a muddy sea-bottom. The last leg apparently has anteriorly pointing claws, that were possibly used as "anchors". Key References Hou et al. They are among the earliest known carnivores and some species reach a size suggested to be well over 1 m.
They have been regarded as related to one of these groups, or as arthropods, or as forming an unrelated group see Briggs , Chen et al. One of the Chengjiang anomalocaridids, Parapeytoia, resolves basal to a range of upper stem-group euarthropods Budd Characteristic features of the anomalocaridids include a pair of grasping appendages and a ring of hard plates, armed with projections, surrounding the mouth.
A series of large flaps extends laterally on each side of the body. These were originally thought of as lateral fins, and in other reports they are regarded as ventral appendages. A multisegmented appendage, which may have functioned as a leg, occurs below each lateral flap in some species Bergstrom , , Houet al.
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The dorsal side of anomalocaridids has been reconstructed by some authors as more or less smooth except for the presence of the eyes. Some species have two long furcal spines, the three segments just anterior of which carry flaps that are notably longer than those further forward. Four anomalocaridid genera are known from the Chengjiang biota.
The presence of the "walking" leg branch of the appendages is based on evidence from other genera. The body is fairly slender; excluding grasping appendages and furca its length is about 1. There is a pair of large, stalked eyes. There are 11 pairs of large, overlapping triangular flaps. The upper or anterior half of each flap is striated.
Behind these appendages there are an additional three pairs of longer flaps and one pair oflong, slender furcal rami. The spiniferous grasping appendages suggest that this animal was carnivorous. The large appendage flaps would probably have given the animal good swimming ability. This species is closely related to the type species of the genus, Anomalocaris canadensis Whiteaves, from the Middle Cambrian of British Columbia.
Key Briggs , Chen etal. References a b Figure Some isolated grasping appendages are at least 14 em long, which gives an idea of the overall large size of the animal. The paired eyes are large. The grasping appendages differ from those of A. As in A. A spine on the third spiniferous podomere from the proximal end is notably long. The distal end of the grasping appendage has three well-developed, curved spines. The more posterior appendages are known virtually only from their large basal flap.
The spiny grasping appendages indicate that this species was carnivorous like other anomalocaridids. The overall similarity in the grasping appendages between this species and Anamalacaris saran hints that the genera are closely related. Amplectabelua is known from a single species that is recorded only fromthe Chengjiang biota. Key References 96 Chen et al. The entire length of the animal is unknown. A trunk appendage consists of a large, striated triangular flap and a "walking" leg branch. The "walking" leg, which is estimated to be at least S. Scm long, has well-defined podomeres only in its distal part.
The leg morphology of this species demonstrates a state of incipient segmentation, a feature that also might be expected to occur in the earliest arthropods. An alternative interpretation, having anomalocaridids as stem-group arthropods, has also been suggested e. Budd , , Wills et al. Although there is only limited knowledge of the morphology of C. It is the only known species of its genus and is not recorded outside the Chengjiang fauna. Key References 98 Hou etal. The succeeding two pairs of appendages, near the mouth, are quite small and appear to have assisted in the manipulation of the food.
Behind, in the trunk, follows the typical anomalocaridid set of wide, striped flaps extending laterally. There is an indication ofthe presence of a pair of long trailing spines, as in Anomalocaris. The mouth ring is also similar to that of Anomalocaris. The paired eyes in Parapeytoia are probably positioned further back than in Anomalocaris. According to one interpretation, the dorsal side of P. The spiny grasping appendages indicate that this species was carnivorous. K ey Referen ces yunnanensis is known only from the Chengjiang fauna.
Hou et al. Those arthropods with biramous limbs, having inner endopod and outer exopod branches, include the trilobites, the crustaceans e. The Chelicerata embraces xiphosurids e. The trilobites, chelicerates, and allies are grouped as the arachnomorphs. Basal to all these there are minor but evolutionary significant groups such as the tardigrades water bears. Hi There, Did you know that you can save books into your library to create gift lists, reading lists, etc? You can also mark books that you're reading, or want to read. Forgotten your password?
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Buy Now. Arrives at our Sydney warehouse in weeks and once received will be despatched with online tracking. Please allow additional time for delivery to your address. See the Delivery tab below for more details. Synopsis Product Details Delivery The celebrated lower Cambrian Chengjiang biota of Yunnan Province, China, represents one of the most significant ever paleontological discoveries.
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