Cheungkongella Temporal range: Cambrian Stage 3, | |
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Restoration of C. ancestralis. | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Subphylum: | Tunicata |
Class: | Ascidiacea |
Genus: | † Cheungkongella Shu et al., 2001 |
Type species | |
†Cheungkongella ancestralis Shu et al., 2001 | |
Species | |
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Cheungkongella is a fossil organism from the lower Cambrian Chengjiang lagerstatte, the affinity of which has been the subject of debate. It was announced as a "probable" tunicate while noting the lack of definitive Cambrian fossils from that group. [2] However, this affinity was later disputed in a paper announcing the discovery of Shankouclava , also from Chengjiang, as the oldest known tunicate. [3] Cheungkongella has been accepted as a distinct taxon and possible tunicate by multiple workers not involved in its discovery, [4] [5] [6] [7] but the dispute remains unresolved. [3] [8]
"Cheungkong" is "a metaphor of China" and honors the Cheungkong Scholars Programme's support for the work leading to the fossil's discovery. "Ancestralis" refers to the fossil's possible primitive taxonomic position. [2]
Cheungkongella has a club-shaped body similar to the extant ascidian Styela , with a bucket-shaped main body with thick, tapering stem beneath it. A large oral siphon with short tentacles at the top of the animal leads to a pharynx occupying two-thirds of the main body, with a structure presumed to ben an alimentary canal beneath it. A small cloacal siphon emerges from the side above the transition to the stem. [9]
Cheungkongella was placed in the class Ascidiacea based on its resemblance Styela. [2] This classification was initially accepted by other workers. [10]
A 2003 paper announcing Shankouclava as the oldest known tunicate both disputed Cheungkongella's affinities and proposed that it is a junior synonym of Phlogites , which was though to be a lophophorate at the time [11]
The paper stated that Cheungkongella is "indistinguishable" from Phlogites, but proceeded to note several differences, most notably the lack of any "obvious" arms in Cheungkongella despite acknowledging that three or five such arms are a prominent feature of Phlogites. The paper speculated that this is "perhaps because its arms broke off or are covered by rock." The lack of a coiled gut in Cheunkongella was dismissed by noting that not all specimens of Phlogites display one. [11]
The original description of Cheungkongella noted light dots in the area interpreted as a pharynx that could be gill slits, but stated that the interpretation required confirmation. The Shankouclava paper suggested that these dots are taphonomic artifacts due to their irregular pattern. However, the paper's other arguments against tunicate affinities were based on newly discovered specimens of Phlogites. [11] Phlogites is now known to be a cambroernid, and has never been assigned to the tunicates except as a result of Cheungkongella being considered a synonym. [12] [13]
A responding paper disputing the synonymization with Phlogites provided the image shown on this page in response to criticisms of poor image quality in past publications. [14]
A paper on the affinities of Phlogites accepted the synonymization, but did not discuss the Cheungkongella fossil except to note a similar thickness of stem between it and a subset of the new Phlogites specimens. [15] The similarity of the lower section has also been noted by workers who consider the two taxa to be separate. [9] [16]
The resemblance between Cheunkongella and Phlogites has been dismissed as "superficial" by a researcher not involved with the discoveries of either of those taxa or of Shankcouklava. [4] Other sources not directly involved in the dispute have recognized both Cheungkongella (as distinct from Phlogites) and Shankouclava as possible (if debatable) tunicates, [5] [6] or recognize Cheungkongella as a tunicate and Shankouclava as chordate. [7]
The dispute remains unresolved, as has been noted by sources that accept or tentatively accept the synonymization. [3] [8]
Vetulicolia is a group of bilaterian marine animals encompassing several extinct species from the Cambrian, and possibly Ediacaran, periods. As of 2023, the majority of workers favor placing Vetulicolians in the stem group of the Chordata, but some continue to favor a more crownward placement as a sister group to the Tunicata. It was initially erected as a monophyletic clade with the rank of phylum in 2001, with subsequent work supporting its monophyly. However, more recent research suggests that vetulicolians may be paraphyletic and form a basal evolutionary grade of stem chordates.
The Maotianshan Shales (帽天山页岩) are a series of Early Cambrian sedimentary deposits in the Chiungchussu Formation, famous for their Konservat Lagerstätten, deposits known for the exceptional preservation of fossilized organisms or traces. The Maotianshan Shales form one of some forty Cambrian fossil locations worldwide exhibiting exquisite preservation of rarely preserved, non-mineralized soft tissue, comparable to the fossils of the Burgess Shale of British Columbia, Canada. They take their name from Maotianshan Hill in Chengjiang County, Yunnan Province, China.
Vetulicola is an extinct genus of marine animal discovered from the Cambrian of China. It is the eponymous member of the enigmatic phylum Vetulicolia, which is of uncertain affinities but may belong to the deuterostomes. The name was derived from Vetulicola cuneata, the first species described by Hou Xian-guang in 1987 from the Lower Cambrian Chiungchussu Formation in Chengjiang, China.
Didazoon haoae is an extinct species of vetulicolid vetulicolian described by Shu, et al. based on fossils found in the Qiongzhusi (Chiungchussu) Formation, Yu'anshan Member, Lower Cambrian, in the Dabanqiao area (Kunming), about 60 km northwest of Chengjiang, China.
Pomatrum is an extinct vetulicolian, the senior synonym of Xidazoon; the latter taxon was described by Shu, et al. (1999) based on fossils found in the Qiongzhusi (Chiungchussu) Formation, Yu'anshan Member, Lower Cambrian, Haikou, (Kunming), about 50 km west of Chengjiang, China.
Banffia is a genus of animals described from Middle Cambrian fossils. The genus commemorates Banff, Alberta, near where the first fossil specimens were discovered. Its placement in higher taxa is controversial, with it mostly being considered to be a member of the enigmatic phylum Vetulicolia.
Vetulicolida is a class of vetulicolians. It consists of the order Vetulicolata and the genus Nesonektris, which is of uncertain placement. It is distinguished from the Banffozoa by the number and size of posterior segments as well as features of the anterior section.
Vetulicolidae is a vetulicolian family from the Cambrian Stage 3 Maotianshan Shale and Sirius Passet Lagerstätte that consists of Vetulicola, Beidazoon, and Ooedigera. It is distinguished from the Didazoonidae by a harder body wall and the lack of an oral disc.
Didazoonidae is a vetulicolian family within the order Vetulicolata. It is charaterized by a relatively thin-walled, non-biomineralized body and a large, round anterior opening surrounded by an oral disc. It may be paraphyletic, even if the phylum Vetulicolia is monophyletic.
Yuyuanozoon magnificissimi, from the Cambrian Stage 3 Chengjiang lagerstatte, is the largest known vetulicolian, with specimens up to 20 cm in length compared to 5–14 cm for other vetulicolian species.
Phlogites is a member of the extinct ambulacrarian stem group Cambroernida, occupying an intermediate position between the basal Herpetogaster and the more derived Eldonioidea. It is known from the Lower Cambrian Haikou Chengjiang deposits of China.
The Cambroernida are a clade of unusual Paleozoic animals with coiled bodies and filamentous tentacles. They include a number of early to middle Paleozoic genera noted as "bizarre" or "orphan" taxa, meaning that their affinities with other animals, living or extinct, have long been uncertain. While initially defined as an "informal stem group," later work with better-preserved fossils has strengthened the argument for Cambroernida as a monophyletic clade.
Cotyledion tylodes is an extinct, stalked filter-feeder known from the Chengjiang lagerstatten. The living animal reached a couple of centimetres in height, and bore a loose scleritome of ovoid sclerites. Its interpretation has been controversial, but it is currently thought to be a member of the Entoprocta stem group.
Vetulicola rectangulata is a species of extinct animal from the Early Cambrian of the Chengjiang biota of China. Regarded as a deuterostome, it has characteristic rectangular anterior body on which the posterior tail region is attached. It was described by Luo Huilin and Hu Shi-xue in 1999.
Nesonektris aldridgei is an extinct vetulicolian from the Late Botomian-aged Emu Bay Shale Lagerstätte in Kangaroo Island, Australia. So far, it is the fourth described vetulicolian that is not restricted to the Maotianshan Shales.
Shankouclava is an extinct genus of tunicates. It is one of two candidates for the oldest member of this group, dating to 518 million years ago. It has been found in the Lower Cambrian Maotianshan Shale at Shankou village, Anning, near Kunming. Each of the eight specimens found and used for description were isolated, suggesting that the genus was solitary and not colonial.
Beidazoon venustum is a marine deuterostome from the group Vetulicolia. It originates from the lower Cambrian Chengjiang biota of Yunnan Province, China, and was discovered in 2005. It is known as the smallest described vetulicolian, and for its surface being covered in many small nodes.
Banfiidae is a family of extinct banffozoan animals from North America and China. The family name is sometimes spelt Banffidae. It includes Banffia, Heteromorphus, and possibly Skeemella. The family may be paraphyletic. The family may be paraphyletic. A Heteromorphus-like dwarf "Form A" is allied with this group at the class level, but has not been formally described or assigned to this family.
Vetulocystidae is the only family of the taxon Vetulocystida, which is a group of extinct deuterostomes of uncertain phylogenetic position. Vetulocystidae is made up of the genera Vetulocystis, Dianchicystis and Thylacocercus.
Heteromorphus is an extinct genus of banffiid from the lower Cambrian Chengjiang lagerstatte. It contains one broadly accepted species, Heteromorphus confusus, as well as a proposed junior synonym, Heteromorphus longicaudatus that may prove to be a separate species as additional specimens are examined. A much smaller species labeled "Form A" is allied with Heteromorphus at the class level but has not been formally described or assigned to Heteromorphus itself.