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The Loricifera are one of the more recently described and least studied of the meiofaunal phyla (Kristensen 1983, Kristensen, Heiner, and Higgins 2007). They are exclusively marine, meiobenthic, bilaterally symmetrical metazoans; the sexually dimorphic adults are usually less than 0.250 mm, but up to 0.500 mm in length. Despite their tiny size, they are extremely complex; the head bears approximately 200–400 specialized, cuticular appendages (Kristensen 1991a). Their life cycle is equally complex, as most have a free-living larva, called a Higgins larva, which has features of both kinorhynchs and rotifers. The larvae have been observed swimming by means of propeller-like toes (Kristensen 1991a). At least some species also possess a cystlike instar considered to be a postlarva, somewhat like the pupa of holometabolic insects, which might delay metamorphosis to the adult (Gad 2005). Some of the postlarval forms are up to 6 times larger than the adults (Gad 2005). Some species apparently have direct development (Kristensen 1991b), but the larvae of others contain a large number of eggs, suggesting paedogenesis (Gad 2005). An alternation of parthenogenesis and bisexual reproduction has also been suggested (Kristensen 1991a). At least one postlarva has been collected that contained an adult (Heiner and Neuhaus 2007). Because they have a lorica and molt, Loricifera are ecdysozoans, sharing many morphological traits with the phyla Priapulida and Kinorhyncha, and commonly are included within the group Scalidophora. A few systematists ally the phyla Priapulida, Kinorhyncha, Loricifera, and Nematomorpha within the phylum Cephalorhyncha (Malakhov 1980, Adrianov, Malakhov, and Yushin 1990). Other systematists ally them with the Tardigrada (Higgins and Kristensen 1988) and some suggest the adult loriciferans are neotenic forms of Priapulida or Kinorhyncha (Kristensen 1991a); their phylogenetic position remains controversial. Worldwide, a total of approximately 50 species are known to exist (Kristensen 1991a), but only 21 species havebeendescribedin2familiesand6genera(Kristensen, Heiner, and Higgins 2007). Many new species that have been collected await descriptions. Loriciferans primarily have been collected from subtidal or littoral habitats, but now they are believed to be widely distributed in the deep sea. Approximately 160 samples from the Angola Basin in 1127 63 Loricifera of the Gulf of Mexico Thomas C. Shirley  Loricifera. After Higgins and Kristensen 1986. 1128 ~ Loricifera 4. Heiner, I., and B. Neuhaus. 2007. Loricifera from the deep sea at the Galapagos spreading center, with a description of Spinoloricus turbatio gen. et sp. nov. (Nanaloricidae). Helgoländer Meeresuntersuchungen 61: 167–182. 5. Higgins, R. P., and R. M. Kristensen. 1988. Loricifera. Pp. 319–321 in R. P. Higgins and H. Thiel, eds. Introduction to the Study of Meiofauna. Smithsonian Institution Press, Washington, D.C. 6. Hubbard, G. F., R. L. Howard, and B. J. Gallaway. 1988. Loricifera, a recently described phylum occurring in the northern Gulf of Mexico. Northeast Gulf Science 10: 49–50. 7. Kristensen, R. M. 1983. Loricifera, a new phylum with Aschelminthes characters from the meiobenthos. Zeitschrift für zoologische Systematik und Evolutionsforschung 21: 163–180. 8. Kristensen, R. M. 1991a. Chapter 9—Loricifera. Pp. 351–375 in F. W. Harrison, ed. Microscopic Anatomy of Invertebrates. Volume 4: Aschelminthes. Wiley-Liss, New York. 9. Kristensen, R. M. 1991b. Loricifera—A general biological and phylogenetic overview. Verhandlungen der Deutschen Zoologischen Gesellschaft (Stuttgart) 84: 231–246. 10. Kristensen, R. M., I. Heiner, and R. P. Higgins. 2007. Morphology and life cycle of a new loriciferan from the Atlantic coast of Florida with an emended diagnosis and life cycle of Nanoloricidae (Loricifera). Invertebrate Biology 126(2): 120–137. 11. Malakhov, V. V. 1980. Cephalorhyncha, a new type of animal phylum of animal kingdom uniting Priapulida, Kinorhyncha, Gordiacea, and a system of Aschelminthes worms. Zoologicheskii Zhurnal 59(4): 485–499. [In Russian, English summary.] the Atlantic produced 280 Loricifera representing 14 new species, with most belonging to new genera (Gad 2001). Loriciferans were not included in the original Bulletin 89, as the widespread and apparently speciose phylum surprisingly had not yet been discovered. Their extremely small size and the tenacity with which they cling to sediments probably explain the delay in their discovery. LoriciferansareexpectedtooccurthroughouttheGulfofMex ico , from the shallow subtidal to its deepest depths, in both coarse and fine sediments. They have been reported from numerous faunal surveys, but specimens have been identified only to phyletic rank. Hubbard, Howard, and Gallaway (1988) collected 506 loriciferan specimens from 40 sampling locations in 298 to 2959 m depths from 1983 to 1985 in the northern Gulf of Mexico. At the time of the publication, the collections significantly increased the reported depth range for...

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