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Flora and Fauna

What follows is a non-exhaustive (and in some cases problematic) list of the Chengjiang fossils (listed alphabetically according to phylum). If an image is available the name will appear as a link (click to view).

Algae | Arthropoda | Brachiopoda | Chordata | Cnidaria | Hemichordata
Lobopodia | Palaeoscolecida | Porifera | Priapulida | Vetulicolia
Uncertain Affinity

Algae

Algae are abundant at Chengjiang, and were probably the major food source for primary consumers. Yuknessia is also found at the Burgess Shale, and was probably attached to the seafloor with long tubular stalks extending upwards. Cinocylindrica has a slender looping form. Whereas Megaspirella is shaped like a helical coil. Cambrorhytium probably belongs in the Cnidaria.

Refs: Bottjer et al, 2002: Briggs et al, 1994.

Arthropoda

The arthropods are dominant within the Chengjiang fauna and also represent the greatest diversity (see list of species below). They include the first described specimen (Yunnanocephalus yunnanensis Mansuy, 1912) and Hou's original discovery, Naraoia longicaudata Zhang & Hou, 1985.

Amongst them are the 'mud-eaters' Fuxianhuia (with a flexible abdomen indicated by the enrollment of some specimens) and Canadaspis (cousin of the Burgess Shale C. perfecta), a bivalved arthropod with a forked, spiny tail. Chengjiangocaris exhibits a similar head to Fuxianhuia and may be a relative, but has a more slender body. Leanchoilia also has a cousin in the Burgess Shale (L. superlata). But despite its shrimp-like appearence it is not a true crustacean. Fortiforceps, another shrimp-like animal, was named foliosa due to it's foliate 'many-leaved' tail. It is also characterised by a pair of globular stalked eyes (click below to see a reconstruction). Acanthomeridion is one of the less well known animals, but we can tell from it's exoskeleton that it was quite rigid and would have been incapable of enrolling. Chuandianella was originally thought to be a direct relative of Waptia (of the Burgess Shale), but further study has shown this relationship to be more distant. Odaraia? is only known from half a specimen (see link below), but if proved to belong to that genus it will represnt the only true crustacean found in the Chengjiang fauna.

The 'trilobite-like' group includes two species of Naraoia one of the most abundant fossils found at Chengjiang and related to N.compacta of the Burgess Shale. N.longicaudata and N.spinosa are characterised by their soft-skin (indicating that they wouldn't be preserved by the normal fossilisation process). N.spinosa is also known from larvae found at Chengjiang (see image below). Retifacies is another soft-skinned animal with a long spine-like, segmented tail. Squamacula is similar to Retifacies, but with a broader, shield-shaped outline. Kuamaia is represented by two species (K.lata being larger), relatives of the Burgess Helmetia they are characterised by large ovate compound (trilobite-like) eyes. Skioldia is similar to K.lata, but is larger again. Saperion is poorly known due to the flattening and distortion shown in specimens so far recovered. Xandarella shows considerably better preservation despite having a non-mineralised exoskeleton. In fact the quality of preservation is good enough to allow quite accurate reconstructions (click below for images). Almenia is similar to Xandarella, but generally isn't so well preserved. Sinoburis also possesses large ovate compound eyes.

Isoxys is represented by two species. I. auritus may represent an ancestor of the crustaceans. Cindarella may be an ancestor of the arachnids.

True trilobites include Kuanyangia (as yet not assigned a species name) and Eoredlicha (the main biozone fossil of the Chengjiang fauna).

Refs: Hou & Bergström, 1997; Shu et al, 1994; Ramsköld et al, 1997.

Further signifigance: Chengjiang has also provided a solution to the 'arthropod head problem' (i.e. how modern arthropod heads evolved so many different organisations), see Budd, 2002. Shu et al (1999a) were able to use Kunmingella from Chengjiang to analyse their anatomy and lifestyle. Evidence from Kunmingella has also proved useful in elucidating the evolution of the Ostracoda (Hou et al, 1996). Isoxys shows evidence of early occupation of a pelagic niche (Vannier & Chen, 2000). Vannier & Chen (2002) were able to use Chengjiang arthropods to interpret digestive and feeding functions of naraoiid arthropods (i.e. Naraoia).

Brachiopoda

Lingulepis has an oval outline with some specimens showing extremely rare preservation of the pedicle (a stalk-like appendage). More recently malongensis has been reinterpretated as belonging to the Lingulellotreta genus. Lingulella matures from a juvenile oval-like form to being a more subtriangular adult. Heliomedusa has delicate features, and probably lay 'open-shelled' on the sea floor.

Refs: Bottjer et al, 2002; Holmer et al, 1997; Jin et al, 1993.

Chordata

The chordates contain the ancestors of the vertebrates (fish, amphibians, reptiles, dinosaurs, mammals and humans). Although it is known that they first appeared in the Cambrian interpretation of these specimens has often been controversial. Such debate often revolves around the appearence of vertebrate-like characteristics.

Myllokunmingia was about 3 cm in length and showed a head, gills, dorsal fin and tail. Haikouichthys was similar, but had a more slender form. Cheungkongella is known from a single specimen found attached to the trilobite Eoredlicha. Haikouella has been interpreted as a craniate-like ('vertebrate'-like) chordate. Presence of a heart, gills, neural cord, 'large' brain and possible lateral eyes have been described. Zhongxiniscus (with S-shaped muscle segments) has been interpreted as an intermediate form between Myllokunmingella, Haikouichthys and Cathaymyrus (represented by 2 species and characterised by a long, slim body). Yunnanozoon may be a hemichordate, with only superfical similarities with the true chordates.

Most recently, the discovery of a new specimen indicates that Myllokunmingia and Haikouichthys are in fact the same species. They are subsequently amalgamated under the first name (Myllokunmingia) and may be considered a primitive ancestor of the vertebrates.

Refs: Hou et al, 2002; Luo et al, 2001; Shu et al, 2001; Shu et al, 1999b; Chen et al, 1999; Enserink, 1999; Shu et al, 1996.

Cnidaria

Xianguangia has a sac-shaped body and tentacles.

Ref: Bottjer et al, 2002.

Hemichordata

Lobopodia

Hallucigenia is represented by two species, and has a row of paired spikes for protection. Microdictyon was previously known only from isolated 'plates' that are now known to be its armour. Paucipodia had six pairs of claw-ended legs, but no armoured plates. Luolishania was a predator with a body which tapers at both ends. Cardiodictyon had many legs as well as head appendages.

Ref: Hou & Bergström, 1995; Chen et al, 1995; Ramsköld & Hou, 1991.

Palaeoscolecida

Palaeoscolex is a segmented worm, but original finds were incomplete with anterior ('head') and posterior ('tail') obscured. More recent evidence shows that they had a priapulid like proboscis ('trunk-like projection') covered with spines and are more closely related to the modern parisitic Nematoda.

Refs: Hou & Sun, 1988; Hou & Bergström, 1994.

Porifera

It has been suggested that some sponges were buried in situ and many are found articulated. Sponges are the second most diverse group (after arthropods), with Demospongea (tubular forms) dominating. These include Leptomitus (2 species), Leptomitella and Paraleptomitella (all thin-walled baloon or fan-shaped forms). Choiaella is more funnel-shaped in appearence. Allantospongia is of an elongate oval shape.

Hexactinellids ('glass sponges' which show a six-rayed radial symmetry) are also found, but are quite rare. These include Quadrolaminella (spherical form), Crumillospongia (sac-shaped) and Haliochondrites (fan-shaped). Triticispongia has an oval, rounded body. Saetospongia is almost circular in appearence.

Parvulonoda is of a cylindrical form, but cannot yet be assigned to a phylum.

Ref: Bottjer et al, 2002; Rigby & Hou, 1995.

Priapulida

Cricocosmia has a cylindrical body and spiny proboscis. Maotianshania shows excellent preservation, and is similar to Cricocosmia, but more elongate in form.

Refs: Bottjer et al, 2002; Hou & Sun, 1988.

Vetulicolia

Didazoon is similar in appearence to Xidazoon and has a two-segment body with an angled 'tail' and a voluminous 'head'.

Ref: Shu et al, 2001.

Uncertain affinity

Dinomischous was described from the Burgess Shale where, like Chengjiang, it is extremely rare. It hasn't been assigned to a phylum because of it's similarity with many groups rather than its possesion of particularly unique features. Eldonia is disc-shaped animal that has been interpretated as a relative of the sea cucumbers (part of the Echinodermata). Rotadiscus is a similar disc-shaped animal, as yet unassigned. Facivermis is worm-like, sharing features with annelids (segmented worms) and lobopods. Recent evidence suggest Xidazoon belongs in the Vetulicolia, but this is contradicted by others who say it is more chordate-like.

Refs: Bottjer et al, 2002; Shu et al, 2001; Shu et al, 1999c; Briggs et al, 1994.

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