Draft:Evolution of spiralia

Spiralia are a morphologically diverse clade of protostome animals, including within their number the molluscs, annelids, platyhelminths and other taxa.The term Spiralia is applied to those phyla that exhibit canonical spiral cleavage, a pattern of early development found in most (but not all) members of the Lophotrochozoa.

list of spiralian animals

Fossil record

The first evidence of spiralia in the fossil record comes from trace fossils in Ediacaran sediments,and the first bona fide spiralia fossil is Kimberella

earlier fossils are controversial; the fossil Ikaria wariootia may be the earliest known spiralian Animal,but may also a early Bilaterian Animal. Fossils are known from around the time of Ikaria wariootia (571 million years ago) but none of these have spiralian affinities However, more recent evidence shows these fossils are actually late Paleozoic instead of Ediacaran.

Cambrian explosion

Diurodrilus is one of the first spiralian animal in the cambrian Diurdrilus is a genus of tiny marine animals that has traditionally been assigned to the annelid worms, although this affinity is not certain. With a maximum length of 0.45 mm, it has an unusual morphology with many traits not found in other annelids, including a ventral creeping foot.^[1][2] Analyses of DNA have both refuted and supported placement within the annelids,^[2][3] with the unusual morphology perhaps due to evolutionary progenesis, in which organisms develop sexual maturity while retaining the larval traits of their ancestors.^[3] and Lobatocerebrum a unknow genus of Annelid, And also the first Molluscs and Brachiopods.

Ordovician-Permian

the first spiralian animal in the Ordovician was Tentaculita an extinct class of uncertain placement ranging from the Early Ordovician to the Middle Jurassic. They were suspension feeders with a near worldwide distribution. The presence of perforate septa and "septal necks" has been used to argue for a cephalopod affinity, whereas the shell microstructure, notably the presence of punctae, points to a brachiopod relationship.^[5]

And another spiralian animal from the Ordovician was Neocephalopoda a group of cephalopod mollusks that include the coleoids and all extinct species that are more closely related to extant coleoids than to the nautilus. In cladistic terms, it is the total group of Coleoidea. In contrast, the palcephalopoda are defined as the sister group to the neocephalopoda.^[1]

After the Late Ordovician mass extinction where there more spiralian animals like Actinoceras the principal and root genus of the Actinoceratidae, a major family in the Actinocerida, that lived during the Middle and Late Ordovician. It is an extinct genus of nautiloid cephalopod that thrived in the warm waters of the United States and England during the Paleozoic era.

And the first scolecodont is the jaw of a polychaete annelid, a common type of fossil-producing segmented worm useful in invertebrate paleontology. Scolecodonts are common and diverse microfossils, which range from the Cambrian period (around half a billion years ago at the start of the Paleozoic era) to the present. They diversified profusely in the Ordovician,^[1] and are most common in the Ordovician, Silurian and Devonian marine deposits of the Paleozoic era.

Relatedly, more problematic worm-like fossils have been described in even older, Neoproterozoic era deposits in the Ediacaran Hills of southern Australia and in mid-Cambrian deposits of Burgess shale in British Columbia.

Since the other classes of annelids (specifically, the earthworms and leeches) lack hard parts, only the sea-dwelling polychaetes are frequently represented in the fossil record. Polychaetes are commonly fossilized due to their chitinous teeth and their dwelling tubes made of durable calcite (a calcium carbonate), hardened mucus (a.k.a. parchment), and/or chitin-like cement.

And then there was the Devonian and there was the first famous spiralian animals and it was the Ammonoids a extinct spiral shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) than they are to shelled nautiloids (such as the living Nautilus).^[1] The earliest ammonoids appeared during the Devonian, with the last species vanishing during or soon after the Cretaceous–Paleogene extinction event. They are often called ammonites, which is most frequently used for members of the order Ammonitida, the only living group of ammonoids from the Jurassic up until their extinction.^[2]

And then there was the Carboniferous and many animals started going on the land most of the spiralian animals on land where Gastropods and Annelida but the climate maked the earth warmer and then was the permian began and the last spiralian animal of the paleozoic was the Flatworm a phylum of relatively simple bilaterian, unsegmented, soft-bodie

d invertebrates. Being acoelomates (having no body cavity), and having no specialised circulatory and respiratory organs, they are restricted to having flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion. The digestive cavity has only one opening for both ingestion (intake of nutrients) and egestion (removal of undigested wastes); as a result, the food can not be processed continuously.

But unfortunately there was an mass extinction also know as the Permian–Triassic extinction event but then there was the Mesozoic

Mesozoic

And then Ammonites started to diverse like Protrachyceras a genus of ceratitid ammonoid cephalopods belonging to the family Trachyceratidae. and there are Goniatites and more.

After that there were advanced like Turbellariaone of the traditional sub-divisions of the phylum Platyhelminthes (flatworms), and include all the sub-groups that are not exclusively parasitic. There are about 4,500 species, which range from 1 mm (0.039 in) to large freshwater forms more than 500 mm (20 in) long^[3] or terrestrial species like Bipalium kewense which can reach 600 mm (24 in) in length. All the larger forms are flat with ribbon-like or leaf-like shapes, since their lack of respiratory and circulatory systems means that they have to rely on diffusion for internal transport of metabolites. However, many of the smaller forms are round in cross section. Most are predators, and all live in water or in moist terrestrial environments. Most forms reproduce sexually and with few exceptions all are simultaneous hermaphrodites.

But then there were 2 mass extinction in the Triassic and the Cretaceous after that is was the Paleogene it was more colder, tropical and less Oxygen and that means smaller animals and big animals started to evolve but for spiralia didn´t change and that is how the cenozic began.

Paleogene

There were many spiralian animals from the Paleogene like Antarcticeras an extinct genus of enigmatic cephalopod from the Eocene of Antarctica. It contains a single species, A. nordenskjoeldi. It is either considered the last of the "orthocone"-type cephalopods, the only member of its subclass Paracoleoidea & a descendant of the orthoceratids, and a remarkable example of convergent evolution with coleoid cephalopods, or an oegospid squid and a transitional form in the development of the modern squid gladius, of which it is the only preserved example.^[1][2]

It is named after Swedish geologist and Antarctic explorer Otto Nordenskjöld.^[1]

And the famous Rotifer a phylum (Rotifera /roʊˈtɪfərə/) of microscopic and near-microscopic pseudocoelomate animals.

They were first described by Rev. John Harris in 1696, and other forms were described by Antonie van Leeuwenhoek in 1703.^[2] Most rotifers are around 0.1–0.5 mm (0.0039–0.0197 in) long (although their size can range from 50 μm (0.0020 in) to over 2 mm (0.079 in)),^[1] and are common in freshwater environments throughout the world with a few saltwater species.

Some rotifers are free swimming and truly planktonic, others move by inchworming along a substrate, and some are sessile, living inside tubes or gelatinous holdfasts that are attached to a substrate. About 25 species are colonial (e.g., Sinantherina semibullata), either sessile or planktonic. Rotifers are an important part of the freshwater zooplankton, being a major foodsource and with many species also contributing to the decomposition of soil organic matter.^[3] Most species of the rotifers are cosmopolitan, but there are also some endemic species, like Cephalodella vittata to Lake Baikal.^[4] Recent barcoding evidence, however, suggests that some 'cosmopolitan' species, such as Brachionus plicatilis, B. calyciflorus, Lecane bulla, among others, are actually species complexes.^[5][6] In some recent treatments, rotifers are placed with acanthocephalans in a larger clade called Syndermata. And then camed a new mondern period the miocene and the Quaternary.

23-0

And then the end, now we know a bit about the spiralian clade but here are some cool spiralian animals like Cryptoconchus porosus a species of chiton, a marine polyplacophoran mollusc in the family Acanthochitonidae, and Pseudobiceros hancockanus a species of hermaphroditic marine flatworm in the family Pseudocerotidae. It is also known as Hancock's Flatworm. And finaly the end.

Image of the flatworm