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17-816: Sardinops is a monotypic genus of sardines of the family Alosidae . The only member of the genus is Sardinops sagax . It is found in the Indo-Pacific and East Pacific oceans. Its length is up to 40 cm (16 in). It has numerous common or vernacular names, some of which more appropriately refer to subspecies, including blue pilchard , Australian pilchard ( S. s. neopilchardus ), blue-bait , Californian pilchard ( S. s. caeruleus ), Peruvian Pacific sardine ( S. s. sagax ), South American pilchard , Chilean sardine ( S. s. sagax ), Japanese pilchard ( S. s. melanostictus ), Pacific sardine , and Southern African pilchard ( S. s. ocellatus ). The South Australian sardine fishery targets Sardinops sagax and

34-602: A common ancestor ) or paraphyletic (excluding some descendants), these concepts do not apply to monotypic taxa because they contain only a single member. Monotypic taxa are part of a broader challenge in biological classification known as aphyly – situations where evolutionary relationships are poorly supported by evidence. This includes both monotypic groups and cases where traditional groupings are found to be artificial. Understanding how monotypic taxa fit into this bigger picture helps identify areas needing further research. The German lichenologist Robert Lücking suggests that

51-482: A hierarchical system. When taxonomists identify a monotypic taxon, this often reflects uncertainty about its relationships rather than true evolutionary isolation . This uncertainty is evident in many cases across different species. For instance, the diatom Licmophora juergensii is placed in a monotypic genus because scientists have not yet found clear evidence of its relationships to other species. Some taxonomists argue against monotypic taxa because they reduce

68-468: A common ancestor, but evolved independently. Monophyletic groups are typically characterised by shared derived characteristics ( synapomorphies ), which distinguish organisms in the clade from other organisms. An equivalent term is holophyly . The word "mono-phyly" means "one-tribe" in Greek. These definitions have taken some time to be accepted. When the cladistics school of thought became mainstream in

85-427: A family. Some examples of monotypic groups are: Monophyletic In biological cladistics for the classification of organisms , monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of taxa which meets these criteria: Monophyly is contrasted with paraphyly and polyphyly as shown in the second diagram. A paraphyletic grouping meets 1. but not 2., thus consisting of

102-553: A natural classification. From a cladistic perspective, which focuses on shared derived characteristics to determine evolutionary relationships, the theoretical status of monotypic taxa is complex. Some argue they can only be justified when relationships cannot be resolved through synapomorphies (shared derived characteristics); otherwise, they would necessarily exclude related species and thus be paraphyletic. However, others contend that while most taxonomic groups can be classified as either monophyletic (containing all descendants of

119-402: Is known as "Gregg's Paradox": if a single species is the only member of multiple hierarchical levels (for example, being the only species in its genus, which is the only genus in its family), then each level needs a distinct definition to maintain logical structure. Otherwise, the different taxonomic ranks become effectively identical, which creates problems for organizing biological diversity in

136-407: Is particularly associated with island species. Among 25 documented extinct monotypic genera studied, 22 occurred on islands, with flightless animals being particularly vulnerable to human impacts. Just as the term monotypic is used to describe a taxon including only one subdivision, the contained taxon can also be referred to as monotypic within the higher-level taxon, e.g. a genus monotypic within

153-485: Is the highest yielding single species fishery in Australia by volume. The fishery employs the technique of purse seining , which contributes to the sardines' status as sustainable. Schools of sardines are encircled by a net up to 1 kilometre in length which is then drawn closed at the bottom. The catch is then pumped on board the fishing vessel where it is stored in refrigerated holds at below freezing temperatures. 94% of

170-412: The 1960s, several alternative definitions were in use. Indeed, taxonomists sometimes used terms without defining them, leading to confusion in the early literature, a confusion which persists. The first diagram shows a phylogenetic tree with two monophyletic groups. The several groups and subgroups are particularly situated as branches of the tree to indicate ordered lineal relationships between all

187-700: The annual quota had increased to 38,000 metric tons (37,000 long tons; 42,000 short tons). The fishery's total landed catch peaked at 56,952 metric tons (56,053 long tons; 62,779 short tons) in the financial year 2004-05 stabilising at around 32,000 metric tons (31,000 long tons; 35,000 short tons) per year thereafter. A key area of concern for industry compliance in 2004 was quota evasion. Quota evasion had previously occurred in several forms: unloading catch directly to tuna farms, failing to report prior to unloading catch and dumping excess catch at sea. Monotypic Monotypic taxa present several important theoretical challenges in biological classification . One key issue

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204-594: The catch is used as feed in Southern bluefin tuna ranching operations off Port Lincoln , South Australia. The remaining 6% of the catch serves human consumption, recreational fishing bait and premium pet food markets. The industry commenced in South Australia in 1991 with an annual catch quota of 1,000 metric tons (980 long tons; 1,100 short tons). In 2003, the fishery's annual quota was set at 36,000 metric tons (35,000 long tons; 40,000 short tons). By 2014,

221-745: The common application of the term monotypic is frequently misleading, "since each taxon by definition contains exactly one type and is hence "monotypic", regardless of the total number of units", and suggests using "monospecific" for a genus with a single species, and "monotaxonomic" for a taxon containing only one unit. Species in monotypic genera tend to be more threatened with extinction than average species. Studies have found this pattern particularly pronounced in amphibians , where about 6.56% of monotypic genera are critically endangered , compared to birds and mammals where around 4.54% and 4.02% of monotypic genera face critical endangerment respectively. Studies have found that extinction of monotypic genera

238-415: The descendants of a common ancestor, excepting one or more monophyletic subgroups. A polyphyletic grouping meets neither criterion, and instead serves to characterize convergent relationships of biological features rather than genetic relationships – for example, night-active primates, fruit trees, or aquatic insects. As such, these characteristic features of a polyphyletic grouping are not inherited from

255-413: The fact that a monophyletic group includes organisms (e.g., genera, species) consisting of all the descendants of a unique common ancestor. Conversely, the term polyphyly , or polyphyletic , builds on the ancient Greek prefix πολύς ( polús ), meaning "many, a lot of", and refers to the fact that a polyphyletic group includes organisms arising from multiple ancestral sources. By comparison,

272-427: The information content of biological classifications. As taxonomists Backlund and Bremer explain in their critique, "'Monotypic' taxa do not provide any information about the relationships of the immediately subordinate taxon". When monotypic taxa are sister to a single larger group, they might be merged into that group; however, when they are sister to multiple other groups, they may need to remain separate to maintain

289-431: The organisms shown. Further, any group may (or may not) be considered a taxon by modern systematics , depending upon the selection of its members in relation to their common ancestor(s); see second and third diagrams. The term monophyly , or monophyletic , derives from the two Ancient Greek words μόνος ( mónos ), meaning "alone, only, unique", and φῦλον ( phûlon ), meaning "genus, species", and refers to

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