|Trace fossil classification|
|This bird-related article is a stub. You can help Wikipedia by expanding it.|
|Trace fossil classification|
|This bird-related article is a stub. You can help Wikipedia by expanding it.|
Birds known as Aves, are a group of endothermic vertebrates, characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, a strong yet lightweight skeleton. Birds range in size from the 5 cm bee hummingbird to the 2.75 m ostrich. They rank as the world's most numerically-successful class of tetrapods, with ten thousand living species, more than half of these being passerines, sometimes known as perching birds. Birds have wings which are less developed depending on the species. Wings, which evolved from forelimbs, gave birds the ability to fly, although further evolution has led to the loss of flight in flightless birds, including ratites and diverse endemic island species of birds; the digestive and respiratory systems of birds are uniquely adapted for flight. Some bird species of aquatic environments seabirds and some waterbirds, have further evolved for swimming; the fossil record demonstrates that birds are modern feathered dinosaurs, having evolved from earlier feathered dinosaurs within the theropod group, which are traditionally placed within the saurischian dinosaurs.
The closest living relatives of birds are the crocodilians. Primitive bird-like dinosaurs that lie outside class Aves proper, in the broader group Avialae, have been found dating back to the mid-Jurassic period, around 170 million years ago. Many of these early "stem-birds", such as Archaeopteryx, were not yet capable of powered flight, many retained primitive characteristics like toothy jaws in place of beaks, long bony tails. DNA-based evidence finds that birds diversified around the time of the Cretaceous–Palaeogene extinction event 66 million years ago, which killed off the pterosaurs and all the non-avian dinosaur lineages, but birds those in the southern continents, survived this event and migrated to other parts of the world while diversifying during periods of global cooling. This makes them the sole surviving dinosaurs according to cladistics; some birds corvids and parrots, are among the most intelligent animals. Many species annually migrate great distances. Birds are social, communicating with visual signals and bird songs, participating in such social behaviours as cooperative breeding and hunting and mobbing of predators.
The vast majority of bird species are monogamous for one breeding season at a time, sometimes for years, but for life. Other species have breeding systems that are polygynous or polyandrous. Birds produce offspring by laying eggs, they are laid in a nest and incubated by the parents. Most birds have an extended period of parental care after hatching; some birds, such as hens, lay eggs when not fertilised, though unfertilised eggs do not produce offspring. Many species of birds are economically important as food for human consumption and raw material in manufacturing, with domesticated and undomesticated birds being important sources of eggs and feathers. Songbirds and other species are popular as pets. Guano is harvested for use as a fertiliser. Birds prominently figure throughout human culture. About 120–130 species have become extinct due to human activity since the 17th century, hundreds more before then. Human activity threatens about 1,200 bird species with extinction, though efforts are underway to protect them.
Recreational birdwatching is an important part of the ecotourism industry. The first classification of birds was developed by Francis Willughby and John Ray in their 1676 volume Ornithologiae. Carl Linnaeus modified that work in 1758 to devise the taxonomic classification system in use. Birds are categorised as the biological class Aves in Linnaean taxonomy. Phylogenetic taxonomy places Aves in the dinosaur clade Theropoda. Aves and a sister group, the clade Crocodilia, contain the only living representatives of the reptile clade Archosauria. During the late 1990s, Aves was most defined phylogenetically as all descendants of the most recent common ancestor of modern birds and Archaeopteryx lithographica. However, an earlier definition proposed by Jacques Gauthier gained wide currency in the 21st century, is used by many scientists including adherents of the Phylocode system. Gauthier defined Aves to include only the crown group of the set of modern birds; this was done by excluding most groups known only from fossils, assigning them, instead, to the Avialae, in part to avoid the uncertainties about the placement of Archaeopteryx in relation to animals traditionally thought of as theropod dinosaurs.
Gauthier identified four different definitions for the same biological name "Aves", a problem. Gauthier proposed to reserve the term Aves only for the crown group consisting of the last common ancestor of all living birds and all of its descendants, which corresponds to meaning number 4 below, he assigned other names to the other groups. Aves can mean all archosaurs closer to birds than to crocodiles Aves can mean those advanced archosaurs with feathers Aves can mean those feathered dinosaurs that fly Aves can mean the last common ancestor of all the living birds and all of its descendants (a "c
An ichnotaxon is defined by the International Code of Zoological Nomenclature as "a taxon based on the fossilized work of an organism", that is, the non-human equivalent of an artifact. Ichnotaxa are names used to identify and distinguish morphologically distinctive ichnofossils, more known as trace fossils, they are assigned genus and species ranks by ichnologists, much like organisms in Linnaean taxonomy. These are known as ichnogenera and ichnospecies, respectively. "Ichnogenus" and "ichnospecies" are abbreviated as "igen." and "isp.". The binomial names of ichnospecies and their genera are to be written in italics. Most researchers classify trace fossils only as far as the ichnogenus rank, based upon trace fossils that resemble each other in morphology but have subtle differences; some authors have constructed detailed hierarchies up to ichnosuperclass, recognizing such fine detail as to identify ichnosuperorder and ichnoinfraclass, but such attempts are controversial. Ichnotaxa comes from the Greek ίχνος, ichnos meaning track and ταξις, taxis meaning ordering.
Due to the chaotic nature of trace fossil classification, several ichnogenera hold names affiliated with animal body fossils or plant fossils. For example, many ichnogenera are named with the suffix -phycus due to misidentification as algae. Edward Hitchcock was the first to use the now common -ichnus suffix in 1858, with Cochlichnus. Due to trace fossils' history of being difficult to classify, there have been several attempts to enforce consistency in the naming of ichnotaxa. In 1961, the International Commission on Zoological Nomenclature ruled that most trace fossil taxa named after 1930 would be no longer available. Bird ichnology Trace fossil classification Glossary of scientific naming Comments on the draft proposal to amend the Code with respect to trace fossils Trace Fossils - Kansas University Catalogue of Ichnotaxa
Trace fossils are classified in various ways for different purposes. Traces can be classified taxonomically and toponomically, that is, according to their relationship to the surrounding sedimentary layers. Except in the rare cases where the original maker of a trace fossil can be identified with confidence, phylogenetic classification of trace fossils is an unreasonable proposition; the taxonomic classification of trace fossils parallels the taxonomic classification of organisms under the International Code of Zoological Nomenclature. In trace fossil nomenclature a Latin binomial name is used, just as in animal and plant taxonomy, with a genus and specific epithet. However, the binomial names are not linked to an organism, but rather just a trace fossil; this is due to the rarity of association between a trace fossil and a specific organism or group of organisms. Trace fossils are therefore included in an ichnotaxon separate from Linnaean taxonomy; when referring to trace fossils, the terms ichnogenus and ichnospecies parallel genus and species respectively.
The most promising cases of phylogenetic classification are those in which similar trace fossils show details complex enough to deduce the makers, such as bryozoan borings, large trilobite trace fossils such as Cruziana, vertebrate footprints. However, most trace fossils lack sufficiently complex details to allow such classification. Adolf Seilacher was the first to propose a broadly accepted ethological basis for trace fossil classification, he recognized that most trace fossils are created by animals in one of five main behavioural activities, named them accordingly: Cubichnia are the traces of organisms left on the surface of a soft sediment. This behaviour may be resting as in the case of a starfish, but might evidence the hiding place of prey, or the ambush position of a predator. Domichnia are dwelling structures that reflect the life positions of organisms, for example the subsurface burrows or borings of suspension feeders, are the most common of the established ethological classes.
Fodinichnia are feeding traces which are formed as a result of organisms disturbing the sediment in their search for food. They are created by deposit feeders as they tunnel through soft sediments producing a 3D structure. Pascichnia are a different type of feeding trace for which the trophic guild responsible are grazers, they create 2D features as they scour the surface of a hard or soft substrate in order to obtain nutriment. Repichnia are locomotory tracks that show evidence of organisms moving from one station to another in a near-straight to curved line. Most of the few traces to be verifiably assigned to a specific organism are in this category, such as various arthropod and vertebrate trackways. Since the inception of behavioural categorization, several other ethological classes have been suggested and accepted, as follows: Aedificichnia: evidence of organisms building structures outside of the infaunal realm, such as termite mounds or wasp nests. Agrichnia: so called "gardening traces", which are systematic burrow networks designed to capture migrating meiofauna or even to culture bacteria.
The organism would have continually inspected this burrow system to prey on any smaller organisms that strayed into it. Calichnia: structures that were created by organisms for breeding purposes, e.g. bee cells. Equilibrichnia: burrows within the sediment that show evidence for organisms' responses to variations in sedimentation rate; this evidence will be in the form of spreiten, which are small laminations in the sediment that reflect previous positions the organisms were in. Fugichnia: "escape traces" that are formed as a result of organisms' attempts to escape burial in sudden high-sedimentation events like turbidity currents; the burrows are marked with chevron patterns showing the upward direction the organisms were tunnelling. Praedichnia: trace fossils that show evidence of predatory behaviour, such as the drill holes left in shells by carnivorous gastropods, or more the bite marks found on some vertebrate bones. Over the years several other behavioural groups have been proposed, but in general they have been discarded by the ichnological community.
Some of the failed proposals are listed below, with a brief description. Chemichnia: a type of agrichnia applied to those instances of bacterial harvesting. Cecidoichnia: a plant trace in which a gall is left on the plant as a result of interaction with animals, bacteria, or other plants. Corrosichnia: traces that are left by plant roots as a result of their corrosive action on the sediments. Cursichnia: a subgroup of the repichnia, created by a crawling or walking habit. Fixichnia: traces left by sessile organisms that anchored themselves to a hard substrate. Mordichnia: a praedichnial subgroup that shows evidence of the prey's death as a result of the attack. Natichnia: a type of repichnia caused by disturbances to a soft sediment by a swimming organism, e.g. a benthic fish. Polychresichnia: traces that show an origin in the combination of two or more established trace-producing behaviours, e.g. domichnia that served as the feeding position of the organisms. Sphenoichnia: a plant trace created by the bioturbational action of roots.
Taphichnia: fugichnia in which the organism failed to escape and was buried resulting in its body fossil being found in association with the trace. Volichnia: traces that show the position a flying organism landed on a soft sediment. Fixichnia is the group with the most weight as a candidate for the next accepted ethological class, being not describe