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Heteromorphida
Banffozoa (also called Heteromorphida) is an extinct class of bilaterians. Most workers place it in the Vetulicolia, but the protostome-like features of some members have motivated ongoing debate. Banffozoa consists of the order Banffiata (which has only one family, Banffiidae) as well as a dwarf "Form A" that has not been formally described or named. '' Skeemella'' has been placed ''incertae sedis'' in this class, but has more recently been placed with the Banffiidae (if it is a banffozoan or vetulicolian at all). Banffozoa may be paraphyletic even if Vetulicolia is monophyletic. Description Banffozoans have a bipartite body with a smooth anterior part that generally lacks evidence of segmentation and may or may not have a lateral groove. The posterior section features far more segments than the Vetulicolida, and (except in ''Skeemella'') these segments are each much narrower as well. Lateral pouches such as those found in the Vetulicolida have not been seen, although some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vetulicolia
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. Etymology The taxon name, Vetulicolia, is derived from the type genus, '' Vetulicola'', which is a compound Latin word composed of ''vetuli'' "old" and ''cola'' "inhabitant". It was named after '' Vetulicola cuneata'', the first species of the group described in 1987. Description The vetulicolian body plan comprises two parts: a voluminous rostral (anterior) forebody, tipped with an anteri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Banffiata
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. 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. Description Banffiids have a bipartite body with a smooth anterior part that may or may not have a lateral groove, and a posterior part with many segments. Lateral pouches have not been seen, although some questions remain regarding their possible presence in ''Skeemella''. The entire body is twisted dextrally (from an anterior view). Gut diverticula may be present, but the structures interpreted as such could alternatively be a circulatory system. The anus is terminal, despite initial reports to the contrary in ''Heteromorphus''. Distribution Banffiids have been found across multiple paleocontinen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Banffiidae
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. A ''Heteromorphus''-like dwarf Banffozoa#Form A, "Form A" is allied with this group at the class level, but has not been formally described or assigned to this family. Description Banffiids have a bipartite body with a smooth anterior part that may or may not have a lateral groove, and a posterior part with many segments. Lateral pouches have not been seen, although some questions remain regarding their possible presence in ''Skeemella''. The entire body is twisted dextrally (from an anterior view). Gut diverticula may be present, but the structures interpreted as such could alternatively be a circulatory system. The anus is terminal, despite initial reports to the contrary in ''Heteromorphus''. Distribution Banffiids have been found across multiple ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Banffia Constricta
''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. Anatomy ''Banffia constricta'' is known from hundreds of fossils found in the Burgess Shales. It is up to 10 cm in length, and divided equally into anterior and posterior parts. The entire body is twisted in a clockwise spiral, as seen from the front. This is believed to be a secondary adaptation from an initial bilateral condition for a burrowing lifestyle. The anterior section is covered by two carapace-like un-mineralized shells that are fused together. A crown-like structure formed of three concentric circular features surrounds the mouth. An antenna-form structure just posterior to the mouth may be a sensory organ. The posterior section is composed of 40 to 50 segments. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambrian Stage 3
Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approximately to the first appearance of trilobites, about million years ago, though the globally asynchronous appearance of trilobites warrants the use of a separate, globally synchronous marker to define the base. The upper boundary and beginning of Cambrian Stage 4 is informally defined as the first appearance of the trilobite genera ''Olenellus'' or ''Redlichia'' around million years ago. Naming The International Commission on Stratigraphy has not officially named the 3rd stage of the Cambrian. The stage approximately corresponds to the "Atdabanian", which is used by geologists working in Siberia. Biostratigraphy The oldest trilobite known is ''Lemdadella'' which appears at the beginning of the ''Fallotaspis'' zone. The Cambrian radiation of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolutionary Grade
A grade is a taxon united by a level of morphological or physiological complexity. The term was coined by British biologist Julian Huxley, to contrast with clade, a strictly phylogenetic unit. Phylogenetics The concept of evolutionary grades arises in the context of phylogenetics: the study of the evolutionary history and relationships among or within groups of organisms. These relationships are determined by phylogenetic inference methods that focus on observed heritable traits, such as DNA sequences, protein amino acid sequences, or morphology. The result of such an analysis is a phylogenetic tree—a diagram containing a hypothesis of relationships that reflects the evolutionary history of a group of organisms. Definition of an evolutionary grade An evolutionary grade is a group of species united by morphological or physiological traits, that has given rise to another group that has major differences from the ancestral group's condition, and is thus not considered p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chordata
A chordate ( ) is a bilaterian animal belonging to the phylum Chordata ( ). All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics (Apomorphy and synapomorphy, synapomorphies) that distinguish them from other Taxon, taxa. These five synapomorphies are a notochord, a neural tube, hollow dorsal nerve cord, an endostyle or thyroid, pharyngeal slits, and a post-anus, anal tail. In addition to the morphological characteristics used to define chordates, analysis of genome sequences has identified two conserved signature indels (CSIs) in their proteins: cyclophilin-like protein and inner mitochondrial membrane protease ATP23, which are exclusively shared by all vertebrates, tunicates and cephalochordates. These CSIs provide molecular means to reliably distinguish chordates from all other animals. Chordates are divided into three phylum, subphyla: Vertebrata (fish, amphibians, reptiles, birds and mammals), whose notochor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Total Group
In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. It is thus a way of defining a clade, a group consisting of a species and all its extant or extinct descendants. For example, Neornithes (birds) can be defined as a crown group, which includes the most recent common ancestor of all modern birds, and all of its extant or extinct descendants. The concept was developed by Willi Hennig, the formulator of phylogenetic systematics, as a way of classifying living organisms relative to their extinct relatives in his "Die Stammesgeschichte der Insekten", and the "crown" and "stem" group terminology was coined by R. P. S. Jefferies in 1979. Though formulated in the 1970s, the term was not commonly used until its reintroduction in 2000 by Graham Budd and Sören Jensen. Contents of the crown gro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vetulicolidae
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. Description Members of the Vetulicolidae have relatively robust body coverings, with a subquadrate to elongate (in lateral view) anterior part and an elongate, segmented posterior part. The marginal zone of the anterior part may have short projections dorsally and postereodorsally. As diagnosed by Aldridge ''et al.'' in 2007, the anterior part is said to bear five annulations, and a lateral groove is not mentioned for the family. However, with and the addition of ''Ooedigera'' not all genera possess annulations in the anterior section, and with the re-classification of ''Yuyuannozoon'' each genus currently assigned to this family bears a lateral groove. Vetulicolids range in size from ''Beidazoon'' (around ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heteromorphus
''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. Description Like ''Banffia'', ''Heteromorphus'' has a two-part body with a notable constriction between the parts, and a crossover that effectively reverses the dorsal and ventral sides between the anterior and posterior sections. The posterior portion is segmented, although the common presence of wrinkling makes counting the segments difficult. The anterior body shape ranges from torpedo-like to more rectangular, with a near-vertical anterior edge. ''Heteromorphus'' is separated from ''Banffia'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nesonektris
''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 (the other three being '' Ooedigera'' of Sirius Passet, '' Banffia'' of the Burgess Shale, and '' Skeemella'' of the Pierson Cove Formation above the Wheeler Shale). Description ''N. aldridgei'' is known from several incomplete fossils which suggest that, in life, it was a fairly large animal (when compared to other vetulicolians). The largest fossil is about 150 millimetres ( 5.9 inches) long, leading researchers to estimate that that individual was about 170 millimetres (6.7 inches) long. The exquisitely preserved fossils show that running the length inside the tail was a notochord, thereby demonstrating the animal's chordate affinities as being related to tunicates. The forebody, and overall form are similar to vetulicolids of Vetulicol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
