myllokunmingia - Synonyms for myllokunmingia

Examples of "myllokunmingia"
Perhaps the most important fossils from Chengjiang are eight possible members of phylum Chordata, the phylum to which all vertebrates belong. The most famous is "Myllokunmingia", possibly a very primitive agnathid (i.e., jawless fish). Similar to "Myllokunmingia" is "Haikouichthys ercaicunensis", another primitive fish-like animal.
For these reasons, "Zhongxiniscus" is tentatively considered to be an intermediate form between "Cathaymyrus" and the two vertebrates "Haikouichthys" and "Myllokunmingia".
There is only one specimen, which has the tip of the tail buried in sediment. Only one species is known – "Myllokunmingia fengjiaoa" (Shu, Zhang & Han).
When compared to other Cambrian chordates like the possible cephalochordate "Cathaymyrus" and the two known vertebrates "Haikouicthys" and "Myllokunmingia", "Zhongxiniscus" resembles "Cathaymyrus" in having S-shaped myomeres, but is different in having a dorsal fin and a shorter body. "Zhongxiniscus" approaches in form to "Haikouicthys" and "Myllokunmingia" in its myomeres and its dorsal fin, but differs from the latter two having zigzag myomeres and fin rays, which "Zhongxiniscus" evidently lacks.
Myllokunmingia is a genus of basal chordate from the Lower Cambrian Maotianshan shales of China, thought to be a vertebrate, although this is not conclusively proven. It is 28 mm long and 6 mm high.
The Chengjiang sediments provide what are currently the oldest known chordates, the phylum to which all vertebrates belong. The 8 chordate species include "Myllokunmingia", possibly a very primitive agnathid and "Haikouichthys", which may be related to lampreys. "Yunnanozoon" may be the oldest known hemichordate.
Myllokunmingiidae is a group of very early, jawless prehistoric fish (Agnathans) which lived during the Cambrian period. The Myllokunmingiids are the earliest known group of craniate chordates. The group contains three genera, "Haikouichthys", "Myllokunmingia", and "Zhongjianichthys". Their fossils have been found only in the Maotianshan Shales lagerstätte.
The first ancestors of fish, or animals that were probably closely related to fish, were "Pikaia", "Haikouichthys" and "Myllokunmingia". These three genera all appeared around 530 Ma. "Pikaia" had a primitive notochord, a structure that could have developed into a vertebral column later. Unlike the other fauna that dominated the Cambrian, these groups had the basic vertebrate body plan: a notochord, rudimentary vertebrae, and a well-defined head and tail. All of these early vertebrates lacked jaws in the common sense and relied on filter feeding close to the seabed.
It is similar to the form "Yunnanozoon", which is possibly a hemichordate. Still, there are anatomical differences from "Yunnanozoon", including a larger stomach and smaller (0.1 mm) pharyngeal teeth. "Haikouella" does not have bones or a movable jaw, but it otherwise resembles vertebrates. Almost certain fish "Haikouichthys" and "Myllokunmingia" have been found in the same beds. Suspected hemichordates are also known from these deposits as well as from the Middle Cambrian Burgess Shale of British Columbia. Other than possible fish scales/plates from the Upper Cambrian of Wyoming, these Chinese fish-like chordates are one of the only known pre-Ordovician craniates.
"Haikouichthys" is about long and is narrower than "Myllokunmingia", another chordate that comes from the same beds. The holotype of "Haikouichthys ercaicunensis" was found in the Yuansshan member of the Qiongzhusi Formation in the 'Eoredlichia' Zone near Haikou at Ercaicun, Kunming City, Yunnan, China, hence its name "Haikou fish from Ercaicun". The fossil was recovered among the Chengjiang fauna, in one of a series of Lagerstätten sites where thousands of exquisitely preserved soft-bodied fossils have already been found. Following the discovery of the holotype, additional Lower Cambrian fossils of "Haikouichthys ercaicunensis" have been discovered.
Although a minor element of modern marine fauna, agnathans were prominent among the early fish in the early Paleozoic. Two types of Early Cambrian animal apparently having fins, vertebrate musculature, and gills are known from the early Cambrian Maotianshan shales of China: "Haikouichthys" and "Myllokunmingia". They have been tentatively assigned to Agnatha by Janvier. A third possible agnathid from the same region is "Haikouella". A possible agnathid that has not been formally described was reported by Simonetti from the Middle Cambrian Burgess Shale of British Columbia.
Vertebrates originated about 525 million years ago during the Cambrian explosion, which saw the rise in organism diversity. The earliest known vertebrate is believed to be the "Myllokunmingia". Another early vertebrate is "Haikouichthys ercaicunensis". Unlike the other fauna that dominated the Cambrian, these groups had the basic vertebrate body plan: a notochord, rudimentary vertebrae, and a well-defined head and tail. All of these early vertebrates lacked jaws in the common sense and relied on filter feeding close to the seabed. A vertebrate group of uncertain phylogeny, small-eel-like conodonts, are known from microfossils of their paired tooth segments from the late Cambrian to the end of the Triassic.
There is a gap of about 100 million years between the beginning of the Cambrian period and the end of the Ordovician period. The early Cambrian period was the period from which numerous fossils of sponges, cnidarians ("e.g.", jellyfish), echinoderms ("e.g.", eocrinoids), molluscs ("e.g.", snails) and arthropods ("e.g.", trilobites) are found. The first animal that possessed the typical features of vertebrates, the "Arandaspis", was dated to have existed in the later Ordovician period. Thus few, if any, fossils of an intermediate type between invertebrates and vertebrates have been found, although likely candidates include the Burgess Shale animal, "Pikaia gracilens", and its Maotianshan shales relatives, "Myllokunmingia", "Yunnanozoon", "Haikouella lanceolata", and "Haikouichthys".
The notochord is the defining feature of Chordates, and was present throughout life in many of the earliest chordates. Although the stomochord of hemichordates was once thought to be homologous, it is now viewed as a convergence. Pikaia appears to have a proto-notochord, and notochords are present in several basal chordates such as Haikouella, Haikouichthys, and Myllokunmingia, all from the Cambrian. The Ordovician oceans included many diverse species of agnathan fish which possessed notochords, either with attached bony elements or without, most notably the conodonts, placoderms and ostracoderms. Even after the evolution of the vertebral column in chondrichthyes and osteichthyes, these taxa remained common and are well represented in the fossils record. Several species (see list below) have reverted to the primitive state, retaining the notochord into adulthood, though the reasons for this are not well-understood.
Jawless fishes belong to the superclass Agnatha in the phylum Chordata, subphylum Vertebrata. Agnatha comes from the Greek, and means "no jaws". It excludes all vertebrates with jaws, known as gnathostomes. Although a minor element of modern marine fauna, jawless fish were prominent among the early fish in the early Paleozoic. Two types of Early Cambrian animal apparently having fins, vertebrate musculature, and gills are known from the early Cambrian Maotianshan shales of China: "Haikouichthys" and "Myllokunmingia". They have been tentatively assigned to Agnatha by Janvier. A third possible agnathid from the same region is "Haikouella". A possible agnathid that has not been formally described was reported by Simonetti from the Middle Cambrian Burgess Shale of British Columbia.
During his re-examination of the Burgess Shale fauna in 1979, paleontologist Simon Conway Morris placed "P. gracilens" among the chordates, making it perhaps the oldest known ancestor of modern vertebrates. He did this because it seemed to have a very primitive, proto-notochord, however, the status of "Pikaia" as a chordate is not universally accepted; its preservational mode suggests that it had cuticle, which is uncharacteristic of the vertebrates (although characteristic of other cephalochordates); further, its tentacles are unknown from other vertebrate lineages. The presence of earlier chordates among the Chengjiang, including "Haikouichthys" and "Myllokunmingia", appears to show that cuticle is not necessary for preservation, overruling the taphonomic argument, but the presence of tentacles remains intriguing, and the organism cannot be assigned conclusively, even to the vertebrate stem group. Its anatomy closely resembles the modern creature "Branchiostoma".
Fossils of one major deuterostome group, the echinoderms (whose modern members include sea stars, sea urchins and crinoids), are quite common from the start of Series 2 of the Cambrian, . The Mid Cambrian fossil "Rhabdotubus johanssoni" has been interpreted as a pterobranch hemichordate. Opinions differ about whether the Chengjiang fauna fossil "Yunnanozoon", from the earlier Cambrian, was a hemichordate or chordate. Another Chengjiang fossil, "Haikouella lanceolata", also from the Chengjiang fauna, is interpreted as a chordate and possibly a craniate, as it shows signs of a heart, arteries, gill filaments, a tail, a neural chord with a brain at the front end, and possibly eyes — although it also had short tentacles round its mouth. "Haikouichthys" and "Myllokunmingia", also from the Chengjiang fauna, are regarded as fish. "Pikaia", discovered much earlier but from the Mid Cambrian Burgess Shale, is also regarded as a primitive chordate.
Most of the animals at the heart of the Cambrian explosion debate are protostomes, one of the two main groups of complex animals. The other major group, the deuterostomes, contains invertebrates such as starfish and sea urchins (echinoderms), as well as chordates (see below). Many echinoderms have hard calcite "shells," which are fairly common from the Early Cambrian small shelly fauna onwards. Other deuterostome groups are soft-bodied, and most of the significant Cambrian deuterostome fossils come from the Chengjiang fauna, a lagerstätte in China. The chordates are another major deuterostome group: animals with a distinct dorsal nerve cord. Chordates include soft-bodied invertebrates such as tunicates as well as vertebrates—animals with a backbone. While tunicate fossils predate the Cambrian explosion, the Chengjiang fossils "Haikouichthys" and "Myllokunmingia" appear to be true vertebrates, and "Haikouichthys" had distinct vertebrae, which may have been slightly mineralized. Vertebrates with jaws, such as the acanthodians, first appeared in the Late Ordovician.
Fossils of one major deuterostome group, the echinoderms (whose modern members include starfish, sea urchins and crinoids), are quite common from the start of the Cambrian, . The Mid Cambrian fossil "Rhabdotubus johanssoni" has been interpreted as a pterobranch hemichordate. Opinions differ about whether the Chengjiang fauna fossil "Yunnanozoon", from the earlier Cambrian, was a hemichordate or chordate. Another fossil, "Haikouella lanceolata", also from the Chengjiang fauna, is interpreted as a chordate and possibly a craniate, as it shows signs of a heart, arteries, gill filaments, a tail, a neural chord with a brain at the front end, and possibly eyes—although it also had short tentacles round its mouth. "Haikouichthys" and "Myllokunmingia", also from the Chengjiang fauna, are regarded as fish. "Pikaia", discovered much earlier (1911) but from the Mid Cambrian Burgess Shale (505 Ma), is also regarded as a primitive chordate. On the other hand, fossils of early chordates are very rare, since invertebrate chordates have no bones or teeth, and only one has been reported for the rest of the Cambrian.