Seymour is a city in and the county seat of Baylor County, United States. The population was 2,740 as of the 2010 Census. Seymour is located on the Brazos River, it is 102 miles north-northeast of Abilene. According to the United States Census Bureau, the city has a total area of 2.9 square miles, of which 0.004 square miles, or 0.20%, is water. The climate is humid subtropical with an extreme temperature deviation, however much of the time the variation is always more and the warm weather prevails over the cold as the averages and the records show, its subtropical location and south of the center of a large land mass bring occasional outbreaks to a latitude and not high altitude. The climate in this area is characterized by hot, humid summers and mild to cool winters, sometimes cold. On August 12, 1936, Seymour witnessed the record highest temperature in Texas, a record, tied by the city of Monahans on June 28, 1994. Seymour is within the area underlain by Texas Red Beds, which are a strata of red-colored sedimentary rock from the Early Permian.
The fossils of Permian-era vertebrates in the Texas Red Beds were first discovered by Edward Drinker Cope in 1877. Subsequent research has revealed rare fossils of Permian-era amphibians like Trimerorhachis, as well as rich deposits of other Permian tetrapods such as Dimetrodon and Diadectes; the order Seymouriamorpha and genus Seymouria, which were first discovered in the Seymour area, are named after the city. As of the census of 2010, there were 2,740 people, a decrease of 5.78% since 2000. The racial makeup of the town was 91.28% White, 3.61% Hispanic or Latino of any race, 2.45% African American, 0.22% Native American, 0.11% Asian, 0.11% Pacific Islander, 4.11% from other races, 3.80% from two or more races. There were 1,451 housing units; as of the census of 2000, 2,908 people, 1,273 households, 790 families resided in the city. The population density was 1,067.5 people per square mile. The 1,534 housing units averaged 563.1 per square mile. The racial makeup of the city was 89.24% White, 10.45% Hispanic or Latino of any race, 4.57% African American, 0.48% Native American, 0.72% Asian, 0.10% Pacific Islander, 3.44% from other races, 1.44% from two or more races.
Of the 1,273 households, 26.0% had children under the age of 18 living with them, 49.1% were married couples living together, 10.0% had a female householder with no husband present, 37.9% were not families. The average household size was 2.25 and the average family size was 2.90. In the city, the population was distributed as 24.3% under the age of 18, 6.1% from 18 to 24, 20.9% from 25 to 44, 23.9% from 45 to 64, 24.8% who were 65 years of age or older. The median age was 44 years. For every 100 females, there were 83.2 males. For every 100 females age 18 and over, there were 79.6 males. The median income for a household in the city was $23,662, for a family was $32,917. Males had a median income of $21,891 versus $19,292 for females; the per capita income for the city was $16,062. About 15.6% of families and 19.5% of the population were below the poverty line, including 31.8% of those under age 18 and 10.7% of those age 65 or over. The local Seymour Chamber of Commerce, Seymour Council for the Arts & Enrichment, Rodeo Association, Lions Club, Garden Club are amongst the many organizations in Seymour, as well as an active Relay for Life Event.
Seymour is home to the Whiteside Museum of Natural History, a small museum which displays fossils collected from the surrounding area. The museum employs a team of paleontologists to analyze new findings, with the help of volunteers from the community. Seymour is served by the Seymour Independent School District. Seymour was founded by settlers from Oregon. A post office was established in 1879, when the town's name was changed to honor local cowboy Seymour Munday, after whom nearby Munday was named. Commerce, a newspaper, a hotel, the county courthouse all followed soon after, as did violence between cowboys and settlers; the town experienced two distinct economic booms: the first, short-lived, was with the construction of the Wichita Valley rail line in 1880, the second was due to the discovery of oil in 1906. The population grew from 500 in 1884 to 3800 in 1950. Agribusiness, as well as some tourism from nearby Lake Kemp, has overtaken oil as the driving factor of the local economy; the Old Settlers Reunion and Rodeo has been held each July since 1896.
The town calls itself "the crossroads of North Texas" because it is located at the junction of five highways: U. S. highways 82, 277, 183, 283, State Highway 114. On August 12, 1936, the temperature at Seymour reached 120 °F, the highest temperature recorded in the state of Texas; the Seymour Division of La Escalera Ranch is located north of Seymour in Baylor County and consists of 34,000 contiguous acres in Baylor and Archer Counties. Known as Circle Bar Ranch, La Escalera Limited Partnership purchased the ranch from the Claude Cowan, Sr. Trust in January 2005. La Escalera partner Jo Lyda Granberg and husband K. G. Granberg manage
The Permian is a geologic period and system which spans 47 million years from the end of the Carboniferous Period 298.9 million years ago, to the beginning of the Triassic period 251.902 Mya. It is the last period of the Paleozoic era; the concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the city of Perm. The Permian witnessed the diversification of the early amniotes into the ancestral groups of the mammals, turtles and archosaurs; the world at the time was dominated by two continents known as Pangaea and Siberia, surrounded by a global ocean called Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior. Amniotes, who could better cope with these drier conditions, rose to dominance in place of their amphibian ancestors; the Permian ended with the Permian–Triassic extinction event, the largest mass extinction in Earth's history, in which nearly 96% of marine species and 70% of terrestrial species died out.
It would take well into the Triassic for life to recover from this catastrophe. Recovery from the Permian–Triassic extinction event was protracted; the term "Permian" was introduced into geology in 1841 by Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Édouard de Verneuil; the region now lies in the Perm Krai of Russia. Official ICS 2017 subdivisions of the Permian System from most recent to most ancient rock layers are: Lopingian epoch Changhsingian Wuchiapingian Others: Waiitian Makabewan Ochoan Guadalupian epoch Capitanian stage Wordian stage Roadian stage Others: Kazanian or Maokovian Braxtonian stage Cisuralian epoch Kungurian stage Artinskian stage Sakmarian stage Asselian stage Others: Telfordian Mangapirian Sea levels in the Permian remained low, near-shore environments were reduced as all major landmasses collected into a single continent—Pangaea; this could have in part caused the widespread extinctions of marine species at the end of the period by reducing shallow coastal areas preferred by many marine organisms.
During the Permian, all the Earth's major landmasses were collected into a single supercontinent known as Pangaea. Pangaea straddled the equator and extended toward the poles, with a corresponding effect on ocean currents in the single great ocean, the Paleo-Tethys Ocean, a large ocean that existed between Asia and Gondwana; the Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, causing the Paleo-Tethys Ocean to shrink. A new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic era. Large continental landmass interiors experience climates with extreme variations of heat and cold and monsoon conditions with seasonal rainfall patterns. Deserts seem to have been widespread on Pangaea; such dry conditions favored gymnosperms, plants with seeds enclosed in a protective cover, over plants such as ferns that disperse spores in a wetter environment. The first modern trees appeared in the Permian. Three general areas are noted for their extensive Permian deposits—the Ural Mountains and the southwest of North America, including the Texas red beds.
The Permian Basin in the U. S. states of Texas and New Mexico is so named because it has one of the thickest deposits of Permian rocks in the world. The climate in the Permian was quite varied. At the start of the Permian, the Earth was still in an ice age. Glaciers receded around the mid-Permian period as the climate warmed, drying the continent's interiors. In the late Permian period, the drying continued although the temperature cycled between warm and cool cycles. Permian marine deposits are rich in fossil mollusks and brachiopods. Fossilized shells of two kinds of invertebrates are used to identify Permian strata and correlate them between sites: fusulinids, a kind of shelled amoeba-like protist, one of the foraminiferans, ammonoids, shelled cephalopods that are distant relatives of the modern nautilus. By the close of the Permian, trilobites and a host of other marine groups became extinct. Terrestrial life in the Permian included diverse plants, fungi and various types of tetrapods; the period saw a massive desert covering the interior of Pangaea.
The warm zone spread in the northern hemisphere. The rocks formed at that time were stained red by iron oxides, the result of intense heating by the sun of a surface devoid of vegetation cover. A number of older types of plants and animals became marginal elements; the Permian began with the Carboniferous flora still flourishing. About the middle of the Permian a major transition in vegetation began; the swamp-loving
Baylor County, Texas
Baylor County is a county located in the U. S. state of Texas. As of the 2010 census, its population was 3,726, its county seat is Seymour. The county was created in 1858 and organized in 1879, it is named for Henry Weidner Baylor, a surgeon in the Texas Rangers during the Mexican–American War. Baylor County is not to be confused with Baylor University, located about 230 miles southeast in McLennan County, nor should its namesake be confused with Confederate Colonel George W. Baylor, who fought in Louisiana during the American Civil War. Baylor County is represented in the Texas House of Representatives by the Republican James Frank, a businessman from Wichita Falls. According to the U. S. Census Bureau, the county has a total area of 901 square miles, of which 867 square miles is land and 34 square miles is covered by water. U. S. Highway 82 U. S. Highway 183 U. S. Highway 277 U. S. Highway 283 State Highway 114 Baylor County is part of the Texas Red Beds, which are a strata of red-colored sedimentary rock from the Early Permian.
The fossils of Permian-era vertebrates in the Texas Red Beds were first discovered by Edward Drinker Cope in 1877. Subsequent research has revealed rare fossils of Permian-era amphibians like Trimerorhachis, as well as rich deposits of other Permian tetrapods such as Dimetrodon and Diadectes. Seymouria baylorensis, a species of Seymouria, was first discovered and named after Baylor County and the city of Seymour; as of the census of 2000, 4,093 people, 1,791 households, 1,156 families resided in the county. The population density was five people per square mile; the 2,820 housing units averaged three per square mile. The racial makeup of the county was 90.96% White, 3.35% Black or African American, 0.59% Native American, 0.51% Asian, 0.12% Pacific Islander, 3.32% from other races] and 1.15% from two or more races. Of the 1,791 households, 25.2% had children under the age of 18 residing in them, 53.5% were married couples living together, 8.2% had a female householder with no husband present, 35.4% were not families.
In addition, 33.30% of all households were made up of individuals and 19.2% had someone living alone, 65 years of age or older. The average household size was 2.26 and the average family size was 2.86. In the county, the population was distributed as 23.4% under the age of 18, 5.5% from 18 to 24, 21.4% from 25 to 44, 25.6% from 45 to 64, 24.1% who were 65 years of age or older. The median age was 45 years. For every 100 females, there were 89.50 males. For every 100 females age 18 and over, there were 86.70 males. The median income for a household in the county was $24,627, for a family was $34,583. Males had a median income of $21,607 versus $19,571 for females; the per capita income for the county was $16,384. About 16.1% of the population and 12.9% of families were below the poverty line, 26.3% of those under the age of 18 and 9% of those 65 and older were living below the poverty line. According to the 2000 census, 21.2% of those aged over 25 did not have a high school diploma, while 32.7% did.
8.7% of the population had a bachelor's degree, 2.3% had a master's degree, 0.2% had a doctoral degree. No males had doctoral degrees. All of Baylor County is served by the Seymour Independent School District, which serves portions of adjacent counties. A small portion is served by the Olney Independent School District; the OISD portion was served by the Megargel Independent School District until MISD closed after May 2006. Seymour Bomarton Mabelle Recorded Texas Historic Landmarks in Baylor County Baylor County from the Handbook of Texas Online Baylor County from the Texas Almanac Baylor County from the TXGenWeb Project Baylor County Profile from the Texas Association of Counties Baylor County Website
The Cenozoic Era meaning "new life", is the current and most recent of the three Phanerozoic geological eras, following the Mesozoic Era and extending from 66 million years ago to the present day. The Cenozoic is known as the Age of Mammals, because the extinction of many groups allowed mammals to diversify so that large mammals dominated it; the continents moved into their current positions during this era. Early in the Cenozoic, following the K-Pg extinction event, most of the fauna was small, included small mammals, birds and amphibians. From a geological perspective, it did not take long for mammals and birds to diversify in the absence of the large reptiles that had dominated during the Mesozoic. A group of avians known as the "terror birds" grew larger than the average human and were formidable predators. Mammals came to occupy every available niche, some grew large, attaining sizes not seen in most of today's mammals; the Earth's climate had begun a drying and cooling trend, culminating in the glaciations of the Pleistocene Epoch, offset by the Paleocene-Eocene Thermal Maximum.
Cenozoic, meaning "new life," is derived from Greek καινός kainós "new," and ζωή zōḗ "life." The era is known as the Cænozoic, Caenozoic, or Cainozoic. The name "Cenozoic" was proposed in 1840 by the British geologist John Phillips; the Cenozoic is divided into three periods: the Paleogene and Quaternary. The Quaternary Period was recognized by the International Commission on Stratigraphy in June 2009, the former term, Tertiary Period, became disused in 2004 due to the need to divide the Cenozoic into periods more like those of the earlier Paleozoic and Mesozoic eras; the common use of epochs during the Cenozoic helps paleontologists better organize and group the many significant events that occurred during this comparatively short interval of time. Knowledge of this era is more detailed than any other era because of the young, well-preserved rocks associated with it; the Paleogene spans from the extinction of non-avian dinosaurs, 66 million years ago, to the dawn of the Neogene, 23.03 million years ago.
It features three epochs: the Paleocene and Oligocene. The Paleocene epoch lasted from 66 million to 56 million years ago. Modern placental mammals originated during this time; the Paleocene is a transitional point between the devastation, the K-T extinction, to the rich jungle environment, the Early Eocene. The Early Paleocene saw the recovery of the earth; the continents began to take their modern shape, but all the continents and the subcontinent of India were separated from each other. Afro-Eurasia was separated by the Tethys Sea, the Americas were separated by the strait of Panama, as the isthmus had not yet formed; this epoch featured a general warming trend, with jungles reaching the poles. The oceans were dominated by sharks. Archaic mammals filled the world such as creodonts; the Eocene Epoch ranged from 56 million years to 33.9 million years ago. In the Early-Eocene, species living in dense forest were unable to evolve into larger forms, as in the Paleocene. There was nothing over the weight of 10 kilograms.
Among them were early primates and horses along with many other early forms of mammals. At the top of the food chains were huge birds, such as Paracrax; the temperature was 30 degrees Celsius with little temperature gradient from pole to pole. In the Mid-Eocene, the Circumpolar-Antarctic current between Australia and Antarctica formed; this disrupted ocean currents worldwide and as a result caused a global cooling effect, shrinking the jungles. This allowed mammals to grow to mammoth proportions, such as whales which, by that time, had become fully aquatic. Mammals like Andrewsarchus were at the top of the food-chain; the Late Eocene saw the rebirth of seasons, which caused the expansion of savanna-like areas, along with the evolution of grass. The end of the Eocene was marked by the Eocene-Oligocene extinction event, the European face of, known as the Grande Coupure; the Oligocene Epoch spans from 33.9 million to 23.03 million years ago. The Oligocene featured the expansion of grass which had led to many new species to evolve, including the first elephants, dogs and many other species still prevalent today.
Many other species of plants evolved in this period too. A cooling period featuring seasonal rains was still in effect. Mammals still continued to grow larger; the Neogene spans from 23.03 million to 2.58 million years ago. It features 2 epochs: the Miocene, the Pliocene; the Miocene epoch spans from 23.03 to 5.333 million years ago and is a period in which grass spread further, dominating a large portion of the world, at the expense of forests. Kelp forests evolved, encouraging the evolution such as sea otters. During this time, perissodactyla thrived, evolved into many different varieties. Apes evolved into 30 species; the Tethys Sea closed with the creation of the Arabian Peninsula, leaving only remnants as the Black, Red and Caspian Seas. This increased aridity. Many new plants evolved: 95% of modern seed plants evolved in the mid-Miocene; the Pliocene epoch lasted from 5.333 to 2.58 million years ago. The Pliocene featured dramatic climactic changes, which led to modern species and plants; the Mediterranean Sea dried up for several million years (because the ice ages reduced sea levels, disconnecting the Atlantic from
Hercosestria is an extinct genus of brachiopods from the Lower and Middle Permian. They were important reef-forming organisms because of their conical shapes, attaching spines, gregarious habits, it is related to Richthofenia. Species of the genus have been found in Texas and Guatemala
Seymouria was a reptile-like tetrapod from the early Permian of North America and Europe. It was small, only 2 ft long. Seymouria was well adapted to life on land, with many reptilian features—so many, in fact, that it was first thought to be a primitive reptile. Seymouria individuals were robustly built animals, with a large head, short neck, stocky limbs, broad feet; the skull was boxy and triangular when seen from above, but it was lower and longer than that of most other seymouriamorphs. The vertebrae had swollen neural arches; as a whole the body shape was similar to that of contemporary reptiles and reptile-like tetrapods such as captorhinids and parareptiles. Collectively these types of animals have been referred to as "cotylosaurs" in the past, although they do not form a clade; the skull was composed of many smaller plate-like bones. The configuration of skull bones present in Seymouria was similar to that of far more ancient tetrapods and tetrapod relatives. For example, it retains an intertemporal bone, the plesiomorphic condition present in animals like Ventastega and embolomeres.
The skull bones were textured, as was typical for ancient amphibians and captorhinid reptiles. In addition, the rear part of the skull had a large incision stretching along its side; this incision has been termed an otic notch, a similar incision in the same general area is common to most Paleozoic amphibians, but unknown in amniotes. The lower edge of the otic notch was formed by the squamosal bone, while the upper edge was formed by downturned flanges of the supratemporal and tabular bones; the tabular has a second downturned flange visible from the rear of the skull. The development of the otic and occipital flanges is greater in Seymouria than in any other seymouriamorph; the sensory apparatus of the skull deserves mention for an array of unique features. The orbits were about midway down the length of the skull, although they were a bit closer to the snout in juveniles, they were more rhomboidal than the circular orbits of other seymouriamorphs, with an acute front edge. Several authors have noted that a few specimens of Seymouria possessed indistinct grooves present in bones surrounding the orbits and in front of the otic notch.
These grooves were remnants of a lateral line system, a web of pressure-sensing organs useful for aquatic animals, including the presumed larval stage of Seymouria. Many specimens do not retain any remnant of their lateral lines, not juveniles. In the middle of the parietal bones was a small hole known as a pineal foramen, which may have held a sensory organ known as a parietal eye; the pineal foramen is smaller in Seymouria than in other seymouriamorphs. The stapes, a rod-like bone which lies between the braincase and the wall of the skull, was tapered, it connected the braincase to the upper edge of the otic notch, served as a conduit of vibrations received by a tympanum which lied within the otic notch. In this way it could transmit sound from the outside world to the brain; the configuration of the stapes is intermediate between non-amniote amniotes. On the one hand, its connection to the otic notch is unusual, since true reptiles and other amniotes have lost an otic notch, forcing the tympanum and stapes to shift downwards towards the quadrate bone of the jaw joint.
On the other hand, the thin, sensitive structure of Seymouria's stapes is a specialization over most non-amniote tetrapods, which have a thick stapes useless for hearing yet useful for reinforcing the skull. The palate had some similarities with both non-amniote tetrapods. On the one hand, it retained a few isolated fangs with maze-like internal enamel folding, as is characteristic for "labyrinthodont" amphibians. On the other hand, the vomer bones at the front of the mouth were narrow, the adjacent choanae were large and close together, as in amniotes; the palate is solid bone, with only vestigial interpteryoid vacuities separated by a long and thin cultriform process. Apart from the isolated fangs, the palate is covered with small denticles radiating out from the rear part of the pterygoid bones. Seymouria has a few amniote-like characteristics of the palate, such as the presence of a prong-like branch of the pterygoid as well as an epipterygoid bone, separate from the pterygoid. However, these characteristics have been observed in various non-amniote tetrapods, so they do not signify its status as an amniote.
The lower jaw retained a few plesiomorphic characteristics. For example, the inner edge of the mandible possessed three coronoid bones; the mandible retained at least one large hole along its inner edge known as a meckelian fenestra, although this feature was only confirmed during a 2005 re-investigation of one of the Cutler Formation specimens. Neither of these traits are common in amniotes; the braincase had a mosaic of features in common with various tetrapodomorphs. The system of grooves and nerve openings on the side of the braincase were unusually similar to those of the fish Megalichthys, the cartilaginous base is another plesiomorphic feature. However, the internal carotid arteries perforate the bra
Conodonts are extinct agnathan chordates resembling eels, classified in the class Conodonta. For many years, they were known only from tooth-like microfossils found in isolation and now called conodont elements. Knowledge about soft tissues remains limited; the animals are called Conodontophora to avoid ambiguity. Conodonts are considered index fossils, fossils used to identify geological periods; the conodonts first appeared during the Cambrian Stage 2. The still unnamed Cambrian Stage 10 can be defined as the first appearance of Eoconodontus notchpeakensis; the upper boundary is defined as the appearance of Iapetognathus fluctivagus which marks the beginning of the Tremadocian and is radiometrically dated as 485.4 ± 1.9 million years ago. The Cambrian–Ordovician extinction event occurred 488 million years ago; this early Paleozoic extinction event extirpated many conodonts. The Lau event, about 420 million years ago, a minor mass extinction during the Silurian period, had a major impact on conodont populations.
The Kačák Event was a period of significant extinctions. The group most affected was the Ammonoidea, although there were faunal turnovers amongst conodonts and dacryoconarids; the entire class is postulated to have been wiped out in the Triassic–Jurassic extinction event, which occurred 200 million years ago. Near the end of the Triassic deadly marine biocalcification began to occur, along with oceanic acidification, sea-level fluctuations and the Central Atlantic Magmatic Province releasing carbon dioxide, sulfur dioxide and aerosols; these environmental catastrophes caused the extinction of the conodonts, along with 34% of other marine genera. Conodonts were first discovered by Heinz Christian Pander, the results published, in Saint Petersburg, Russia, in 1856; the name pander is a common part, in scientific names of conodonts. The 11 known fossil imprints of conodont animals record an eel-like creature with 15 or, more 19 elements that form a bilaterally symmetrical array in the head; the organisms range from a centimeter or so to 40 cm in length.
It is now agreed that conodonts had large eyes, fins with fin rays, chevron-shaped muscles and a notochord. Conodont teeth are the earliest found in the fossil record; the evolution of mineralized tissues has been puzzling for more than a century. It has been hypothesized that the first mechanism of mammalian tissue mineralization began either in the oral skeleton of conodont or the dermal skeleton of early agnathans; the element array constituted a feeding apparatus, radically different from the jaws of modern animals. They are now termed "conodont elements" to avoid confusion; the three forms of teeth, i.e. coniform cones, ramiform bars, pectiniform platforms performed different functions. For many years, conodonts were known only from enigmatic tooth-like microfossils, which occur but not always in isolation, were not associated with any other fossil; until the early 1980s, conodont teeth had not been found in association with fossils of the host organism, in a konservat lagerstätte. This is because the conodont animal was soft-bodied, thus everything but the teeth was unsuited for preservation under normal circumstances.
These microfossils are made of hydroxylapatite. The conodont elements can be extracted from rock using adequate solvents, they are used in biostratigraphy. Conodont elements are used as paleothermometers, a proxy for thermal alteration in the host rock, because under higher temperatures, the phosphate undergoes predictable and permanent color changes, measured with the conodont alteration index; this has made them useful for petroleum exploration where they are known, in rocks dating from the Cambrian to the Late Triassic. The conodont apparatus may comprise a number of discrete elements, including the spathognathiform, trichonodelliform and other forms. In the 1930s, the concept of conodont assemblages was described by Hermann Schmidt and by Harold W. Scott in 1934; the feeding apparatus of ozarkodinids is composed at the front of an axial Sa element, flanked by two groups of four close-set elongate Sb and Sc elements which were inclined obliquely inwards and forwards. Above these elements inward pointing M elements.
Behind the S-M array lay transversely oriented and bilaterally opposed Pb and Pa elements. The "teeth" of some conodonts have been interpreted as filter-feeding apparatuses, filtering plankton from the water and passing it down the throat. Others have been interpreted as a "grasping and crushing array"; the lateral position of the eyes makes it unlikely. The preserved musculature suggests that some conodonts were efficient cruisers, but incapable of bursts of speed. A study on the population dynamics of Alternognathus has been published. Among other things, it demonstrates that at least this taxon had short lifespans lasting around a month; as of 2012, scientists classify the conodonts in the phylum Chordata on the basis of their fins with fin rays, chevron-shaped muscles and notochord. Milsom and Rigby envision them as vertebrates similar in appearance to modern hagfish and lampreys, phylogenetic analysis suggests they are more derived than either of these groups. However, this analysis comes with one caveat: early forms of conodonts, the protoconodonts, appear to form a distinct clade from the paraconodonts and euconodonts.
Protoconodonts represent a stem group to the phylum that includes chaetognath worms.