Belongs within: Platytrochozoa.
Contains: Machaeridia, Leodicidae, Orthonectida, Aciculata, Mesonerilla, Echiura, Aeolosomatida, Clitellata, Scolecida, Polygordius, Saccocirrus, Protodrilus, Spionida, Cirratuliformia, Orbiniidae, Paraonidae, Maldanidae, Terebelliformia, Arenicolidae, Sabellida.
The Annelida include the segmented worms and related taxa. Most members of this clade possess homonomous segmentation, lateral chaetae and a nuchal organ at the posterior end of the prostomium, but these characters have all been modified or lost in some derived subgroups. Many classifications of the annelids have divided them between three classes: the Polychaeta (mostly marine worms which have more or less dense arrays of chaetae inserted on lateral parapodia), Oligochaeta (earthworms and related taxa which have fewer chaetae and lack parapodia) and Hirudinea (leeches). However, recent phylogenetic analyses have indicated that the latter two ‘classes’ (which together form a clade called the Clitellata) are likely to be nested within the paraphyletic ‘polychaetes’.
Exact relationships within the annelids remain otherwise much debated. Potential clades include the Sedentaria, members of which often possess grooved, ciliated palps in association with the prostomium (Parry et al. 2014). The Chaetopteridae are infaunal tube-dwelling members of this clade in which the body is regionally specialised with modified appendages on different segments. The Oweniidae inhabit tubes constructed of sand and other particles, and lack parapodia on the segments.
A number of minute, interstitial families have proven particularly difficult to place owing to their reduced morphology. The Nerillidae are mostly marine polychaetes with the prostomium fused to the peristomium and with setae on most or all segments.
Separating segments
Published 7 March 2008
Annelids have long been victim to a certain chauvinism in systematics. They’ve been treated as kind of the poor cousin to the other major animal phyla*, coupled with an idea that they were in some way “primitive”. A number of other phyla, most notably the arthropods and molluscs, have at various times been explicitly or implicitly regarded as derived from annelid ancestors. It must be stressed that in very few of these cases of proposed annelid ancestry was a direct connection made to any specific annelid subgroup. Annelid ancestry was less of a rigorous hypothesis and more of a vague assertion, in the same vein as suggestions of a “thecodont” ancestry of birds.
*Though they still had the flatworms to look down on, at least.
Things changed somewhat with the advent of recent molecular or molecular-influenced phylogenetic studies. Three phyla in particular, the annelids, onychophorans and arthropods, had been united by their metameric segmentation, the regular repetition of separated, similar body segments (this pattern of segmentation has become obscured in many arthropods by specialisation of the separate segments, but is still recognisable in groups such as centipedes and millipedes). More recent analyses have shown the onychophorans and arthropods to have evolved their segmentation separately from annelids, forming a clade with the nematodes and other smaller phyla (the Ecdysozoa) while annelids sit in a clade called the Lophotrochozoa with such phyla as molluscs and brachiopods. Within the trochozoans, metameric segmentation might have been reborn as a defining character of annelids, but the spectre of “ancestral annelids” still didn’t quite go away. For instance, while molluscs are mostly unsegmented, one supposedly basal taxon, the Neopilinida, possesses serial repetition of some organs and was suggested to demonstrate the origin of molluscs from a segmented ancestor, with the implication that “segmented” equaled “annelid” generally not too far behind.
Within the annelids, things have not been much better. Traditionally, annelids have been divided into three classes, the Polychaeta (marine worms), Oligochaeta (earthworms) and Hirudinea (leeches), but it has long been recognised that this is not a satisfactory situation. It is well-established that the earthworms and leeches form a single clade, the Clitellata, but within the Clitellata the “oligochaetes” are united only by the absence of the derived features of leeches. Relationships between the Clitellata and Polychaeta have been even more contentious—authors have differed on whether the polychaetes form a monophyletic group that is sister to the Clitellata, or whether the Clitellata is nested within the polychaetes. The polychaetes in turn have been divided between about 80 families, but relationships between those families have been almost completely unresolved.
An influential study in annelid phylogenetics was that of Rouse & Fauchauld (1997) which undertook a morphological analysis of the polychaetes. Rouse & Fauchauld found a monophyletic Polychaeta with Clitellata as sister group, and division of the polychaetes into three major clades, named Aciculata, Canalipalpata and Scolecida. They also found that the worms previously regarded as the separate phylum Pogonophora were actually highly derived annelids, as had been suggested by some authors previously. Unfortunately, support for any of the clades found was relatively low, and homoplasy was rampant. The benefits of hindsight allow us to quibble with their choice of outgroups, as well—Rouse & Fauchauld rooted their tree using the small non-segmented worm clades Sipuncula and Echiura (on which see more below) and the arthropods and onychophorans, for which many of the supposedly shared characters were probably homoplasies. A recent major molecular study (Rousset et al. 2007), despite including some 217 taxa, was unable to even demonstrate annelid monophyly, finding many of the supposed ‘outgroups’, including molluscs, brachiopods and nemerteans, scattered around within the annelids, and recovered almost none of the major clades of Rouse & Fauchauld (1997). However, support over the entire analysis was low, and large chunks of data were missing for many of the taxa included in the analysis.
And so we finally get to Struck et al. (2007). While Struck et al. did not cover quite as many taxa as Rousset et al. (2007), they included more genes and more complete data for the taxa included. Outgroup taxa were drawn from a number of other lophotrochozoan phyla, and the first major result of Struck et al. was the resolution of Annelida as a coherent clade, in contrast to earlier molecular studies. Within Annelida, polychaetes were paraphyletic with regard to Clitellata, and the closest relatives of the Clitellata were the Aeolosomatidae, previously suggested as such on morphological grounds. As for the major morphological clades of Rouse & Fauchauld, while none were strictly monophyletic, the conflict between morphological and molecular results was much reduced. Rouse & Fauchauld’s Aciculata was largely monophyletic except for the inclusion of one taxon that had been included with the Scolecida, while the majority of the Scolecida formed two branches of an unresolved trichotomy with the clade including the Clitellata.
Three small groups of worms previously classified as separate phyla were also included among the annelids. The annelid nature of the Pogonophora (corresponding to the Siboglinidae in the tree above) was confirmed, as was its position in the order Sabellida as proposed by Rouse & Fauchauld. The Echiura had also been previously suggested to be derived annelids—while the adults are non-segmented, echiurans do possess chaetae (bristles) like those of annelids and characters related to segmentation have been demonstrated in their larvae. Struck et al. found a relationship between Echiura and the polychaete family Capitellidae, as had been found in previous molecular studies.
Something that is likely to cause more debate, though, is Struck et al.‘s finding the Sipuncula within the annelids. The relationships of the Sipuncula or peanut worms have long been debatable. Some authors have favoured a relationship with annelids, while others have placed them closer to molluscs. Unfortunately, Struck et al. included only one representative of the Sipuncula, and while it was nested well within the annelids its position therein was quite unstable, moving about a lot between analyses. It is worth noting here that the large-scale analysis of animal interrelationships by Dunn et al. available from yesterday as an advance online publication at Nature also positioned Sipuncula within the Annelida. Nevertheless, I can see a lot of further study being done on this result in the future.
A lot remains to be done before we can fully understand the evolution of the annelids, but Struck et al. have certainly made an important contribution. Hopefully, the exorcism of the spectral “ancestral annelid” will encourage the study of annelids not as some relictual halfway-house on the way to somewhere else, but as a specialised and diverse grouping in their own right.
Systematics of Annelida
Annelida (see below for synonymy)
|--Pygocirrus butyricampumPE16
|--GuanshanchaetaPE16
|--+--AciculataPE16
| `--NerillidaeH-S86
| |--MesonerillaPE16
| |--Thalassochaetus Ax 1954H-S86
| | `--T. palpifoliaceus Ax 1954TS02
| |--Afronerilla Faubel 1978H-S86
| | `--A. hartwigi Faubel 1978H-S86
| |--Bathynerilla Faubel 1978H-S86
| | `--B. marina Faubel 1978H-S86
| |--Nerillidopsis Jouin 1966H-S86
| | `--N. hyalina Jouin 1966H-S86
| |--Psammoriedlia Kirsteuer 1966H-S86
| | `--P. ruperti Kirsteuer 1966H-S86
| |--Troglochaetus Delachaux 1921H-S86
| | `--T. beranecki Delachaux 1921H-S86
| |--Meganerilla Boaden 1961H-S86
| | |--M. clavata Magagnini 1966H-S86
| | `--M. swedmarki Boaden 1961TS02
| |--MicronerillaTS02
| | |--M. brevis Saphonov & Tzetlin 1997TS02
| | `--M. minutaTS02
| |--Nerilla Schmidt 1848H-S86
| | |--N. antennata Schmidt 1848H-S86
| | |--N. digitata Wieser 1957H-S86
| | |--N. inopinata Gray 1968H-S86
| | |--N. marginalis Tilzer 1970H-S86
| | |--N. mediterranea Schlieper 1925H-S86
| | |--N. parva Schmidt & Westheide 1977H-S86
| | |--N. sinica Wu, Chen & Sun 1980H-S86
| | `--N. stygicola Ax 1957H-S86
| `--Nerillidium Remane 1925H-S86
| |--N. gracile Remane 1925TS02
| |--N. levetzovi Remane 1949H-S86
| |--N. lothari Schmidt & Westheide 1977H-S86
| |--N. macropharyngeum Jouin 1970H-S86
| |--N. mediterraneum Remane 1928H-S86
| |--N. renaudae Join 1970H-S86
| |--N. simplex Levi 1953H-S86
| `--N. troglochaetoides Remane 1925H-S86
`--Sedentaria [Canalipalpata, Capitellida, Drilomorpha, Spiomorpha]PE16
| i. s.: Keilorites Allan 1927Ho62 [=Trachyderma Phillips 1848 non Latreille 1829Ho62; KeiloritidaeW93b]
| |--*K. crassituba (Chapman 1910) [=*Trachyderma crassituba]Ho62
| |--‘Trachyderma’ antiquissimaH64
| |--K. coriacea (Phillips 1848)W93b
| `--K. squamosa (Phillips 1848)W93b
|--+--+--+--EchiuraPE16
| | | `--+--AeolosomatidaSS07
| | | `--ClitellataPE16
| | `--+--ScolecidaPE16
| | `--Cossura Webster & Benedict 1887PE16, J56 [Cossuridae]
| | |--*C. longocirrataJ56
| | |--C. candida Hartman 1955J56
| | `--C. pygodactyla Jones 1956J56
| `--+--Polygordiidae [Gymnotoma]RP07
| | |--PolygordiusPE16
| | |--Rhamphogordius lacteus Rathke 1843H69
| | |--Linotrypane apogon M’Intosh 1875H69
| | `--Chaetogordius canaliculatus Moore 1904H69
| `--+--Protodriloides Jouin 1966PE16, H-S86 [Protodriloididae]
| | |--P. chaetifer (Remane 1926)H-S86
| | `--P. symbioticus (Giard 1904)H-S86
| `--+--SaccocirrusPE16
| `--ProtodrilidaeRP07
| |--ProtodrilusPE16
| `--Astomus Jouin 1979H-S86
| `--A. taenioides Jouin 1979H-S86
`--+--SpionidaPE16
`--+--+--CirratuliformiaPE16
| `--+--OrbiniidaePE16
| `--ParaonidaePE16
`--+--+--MaldanidaePE16
| `--+--TerebelliformiaPE16
| `--ArenicolidaePE16
`--+--OweniidaePE16
| |--Myriochele heeriRP07, M13
| `--OweniaPE16
| |--O. collaris Hartman 1955SS07 [=O. fusiformis collarisR68]
| |--O. fusiformis delle Chiaje 1841SS07
| `--O. mirrawa Ford & Hutchings 2005HG14
`--+--SabellidaPE16
`--ChaetopteridaePE16
| i. s.: Spiochaetopterus costarum (Claparède 1870)SS07
|--ChaetopterusRP07
| |--C. sarsi Boeck in Sars 1851RP07
| `--C. variopedatus (Renier 1804)SS07
`--+--Telepsavus costarum Claparède 1868RP07, R68
`--PhyllochaetopterusRP07
|--P. solitariusM62
|--P. verrillii Treadwell 1943H56
`--P. vitrarius (Ehlers 1908)HG14
Annelida incertae sedis:
Paranerilla limicolaGO06
Phyllobranchus Girard 1851BR05
MachaeridiaPTV14
Eumenia crassaMF02
Jugaria quadriangularisKBC03
CirceisKBC03
|--C. armoricanaKBC03
`--C. spirillumKBC03
Hermilepidonotus robustusKBC03
PolymniaKBC03
|--P. nebulosaPB02
`--P. trigonostomaKBC03
Demonax fulloKBC03
Hermonia histrixM62
Kefersteinia cirrataM62
PodarkeM62
|--P. obscuraH56
`--P. pallidaM62
Langheransia cornutaM62
Dialychone acusticaM62
JasmineiraBBB-S95
|--J. candelaM62
`--J. elegansBBB-S95
Praegeria remotaM62
Synelmis albini (Langerhans 1881)H-S86
Adyte assimilis (McIntosh 1874) [=Hermadion assimile, Scalisetosus assimilis; incl. H. echini Giard 1886]BK77
Antinoella sarsi [incl. Polynoe cirrata Grube 1876, Harmothoe cirrata]BK77
Hermadion hyalinusBK77
Hesperonoe adventorCH97
Scolecolepides benhamiHS01
Hemipodus simplexHS01
‘Hedyle’ Malmgren 1865 non Guenée 1857BR05
Psammodrilidae [Psammodrilida]H-S86
|--Psammodriloides Swedmark 1961H-S86
| `--P. fauveli Swedmark 1961H-S86
`--Psammodrilus Swedmark 1953H-S86
|--P. aedificator Kristensen & Nørrevang 1982H-S86
`--P. balanoglossoides Swedmark 1952TS02
Steblospio benedictiR96
Manayunkia speciosaKA01
Hrabeiella periglandulata Pizl & Chalupsky 1984RP07
DitrypaF71
|--D. australis Bretnall 1921F71
`--D. brazieri Bretnall 1921F71
Augeneriella lagunariP71
Theostoma oerstediBBB-S95
ArabellidaeH56
|--Notocirrus attenuatus (Treadwell 1906) [=Arabella attenuata]H56
`--ArabellaH56
|--‘Aracoda’ attenuata Treadwell 1911 [=Drilonereis attenuata]H56
|--A. iricolor (Montagu 1804) (see below for synonymy)H56
|--A. iridescens Treadwell 1906H56
|--A. mutansR68
`--A. semimaculata (Moore 1911) [=Aracoda semimaculata; incl. Arab. pacifica Treadwell 1941]H56
LaonomeBBB-S95
|--L. kroyeriBBB-S95
`--L. salmacidisBBB-S95
AudouiniaBBB-S95
|--A. filigeraBBB-S95
`--A. tentaculataBBB-S95
LeodicidaeHo62
LumbriconereidaeHo62
|--Lumbriconereites Ehlers 1869Ho62
| `--*L. deperditus Ehlers 1869Ho62
`--Lumbriconereis Grube 1840Ho62
|--*L. quadristriata Grube 1840Ho62
|--L. coccineaPP64
|--L. paradoxaPP64
`--L. tingensCV02
StaurocephalitidaeHo62
|--Staurocephalites Hinde 1879Ho62
| `--*S. niagarensis Hinde 1879Ho62
`--Marlenites Eller 1945Ho62
`--*M. marginatus (Eller 1944) [=Oenonites marginatus]Ho62
Ebetallites Žebera 1935Ho62
`--*E. ancoraeformis Žebera 1935Ho62
Ottawina Wilson 1948Ho62
`--*O. trentonensis Wilson 1948Ho62
ChloraemidaeHo62
|--Chloraema Dujardin 1838Ho62
| `--*C. edwardsii Dujardin 1838Ho62
|--Eotrophonia Ulrich 1878Ho62
| `--*E. setigera Ulrich 1878Ho62
`--Siphonostomites Roverto 1904Ho62
`--*S. hesionoides (Massalongo 1855) [=Nereites hesionoides]Ho62
Campylites Eichwald 1856Ho62
`--*C. longissimus (Sowerby 1839) [=Serpulites longissimus]Ho62
Hammatopsis Hadding 1913Ho62
`--*H. scanicus Hadding 1913Ho62
Khemisina Termier & Termier 1951Ho62
`--*K. annulata Termier & Termier 1951Ho62
Lockportia Howell 1959 [=Dactylethra Ruedemann 1925 nec Cuvier 1829 nec Meyrick 1906]Ho62
`--*L. conspicua (Ruedemann 1925) [=*Dactylethra conspicua]Ho62
Oliveirania Maury 1927Ho62
`--*O. santacatharinae Maury 1927Ho62
Ruedemannella Howell 1959 (see below for synonymy)Ho62
`--*R. obesa (Ruedemann 1925) [=*Bertiella obesa]Ho62
Tubulella Howell 1949 [incl. Urotheca Matthew 1899 non Cocteau & Bibron 1843]Ho62
|--*T. flagellum (Matthew 1899)Ho62 (see below for synonymy)
|--T. pervetus (Matthew 1899)WS93
`--T. terranovaensis Howell 1963WS93
Tubulelloides Howell 1949Ho62
`--*T. gracilis (Ruedemann 1916) [=Serpulites gracilis]Ho62
Eopolychaetus Ruedemann 1901Ho62
`--*E. albaniensis Ruedemann 1901Ho62
Pontobdellopsis Ruedemann 1901Ho62
`--*P. cometa Ruedemann 1901Ho62
Lonchosaccus Ruedemann 1925H75
`--*L. uticanus Ruedemann 1925H75
LadathecaL95
|--*L. annae (Syssoiev 1959)D94
|--L. cylindrica (Grabau 1900)L95
`--L. sysoievi (Meshkova 1974)W93a
Peronochaeta [Peronochaetidae]E-J04
`--P. dubia (Walcott 1911) [=Canadia dubia]E-J04
Insolicorypha [Insilicoryphidae]E-J04
`--I. psygma Conway Morris 1979E-J04
Stephenoscolex [Stephenoscolecidae]E-J04
`--S. argutus Conway Morris 1979E-J04
RhodinePG98
|--R. intermediaPG98
`--R. loveni [incl. R. loveni f. gracilior]PP64
Clymene lumbricoidesPP64
Scolaricia typicaPP64
Leiocapitella dollfusiPP64
Nossis Kindberg 1865KM17
Psyrmobranchus protensusG84
ArachnostegaJB12
Facivermis yunnanicus Hou & Chen 1989W93b
Maotianchaeta fuxianellaC12
OrthonectidaSRT18
Pharyngocirrus tridentigerSRT18
Ramesses Schram 1979S79
`--*R. magnus Schram 1979S79
Soris Schram 1979S79
`--*S. labiosus Schram 1979S79
Trophonia plumosaM01
Pareulepis [Pareulepidae]H56
|--P. fimbriata (Treadwell 1901) [=Eulepis fimbriata]H56
`--P. wyvillei (McIntosh 1885) [incl. Eulepis splendida Treadwell 1901]H56
EupanthalisH56
|--E. maculosa (Treadwell 1931) [=Macellicephala maculosa]H56
`--E. mutilata (Treadwell 1906) [=Polynoe mutilata; incl. E. oahuensis Treadwell 1906]H56
Eupolyodontes elongata (Treadwell 1931) [=Iphionella elongata]H56
LysaretidaeR68
|--Lysarete brasiliensis Kinberg 1865 [incl. Oenone brevimaxillata Treadwell 1931]H56
`--Aglaurides fulgidaR68
Chrysodon alveolatumG20
Thia rostrataG20
Eumolpe planaG20
Levinsenia gracilisHG98
Lysippe labiataHG98
Paraprionospio cooraPG98
Kinbergonuphis proalopusPG98
Rhamphobrachium (Spinigerum) averinceviPG98
Leitoscoloplos kerguelensisPG98
Vermiforma Cloud in Cloud et al. 1976D78, G79
`--*V. antiqua Cloud in Cloud et al. 1976G79
Hyalonaecia tubicolaD56
Telephus circinnatusPB02
LeiochonePB02
|--L. clypeataPB02
`--L. leiopygosPB02
Trace fossil: Trachyderma serrata Salter 1864Ha62
Annelida [Amphitrites, Archiannelida, Chaetopoda, Errantida, Naidina, Nereides, Palpata, Pharyngata, Plesiopora, Plesiotheca, Polychaeta, Sedentarida, Terebellida]
Arabella iricolor (Montagu 1804) [=Nereis iricolor; incl. A. dubia Treadwell 1922, Drilonereis pinnata Treadwell 1921, A. setosa Treadwell 1921]H56
Ruedemannella Howell 1959 [=Bertiella Ruedemann 1925 nec (Sacc.) Sacc. & Syd. 1899 (ICBN) nec Stiles & Hassall 1902 nec Kirschst. 1906 (ICBN)]Ho62
*Tubulella flagellum (Matthew 1899)Ho62 [=Urotheca flagellumHo62; incl. Selkirkia pennsylvanica Resser & Howell 1938SHB15]
*Type species of generic name indicated
References
[BK77] Barel, C. D. N., & P. G. N. Kramers. 1977. A survey of the echinoderm associates of the north-east Atlantic area. Zoologische Verhandelingen 156: 1–159.
[BBB-S95] Boubezari, K., G. Bitar & D. Bellan-Santini. 1995. Structure et organisation de trois moulières (Mytilus galloprovincialis et Perna perna) de la région d’Alger. Mésogée 54: 63–72.
[BR05] Bouchet, P., & J.-P. Rocroi. 2005. Classification and nomenclator of gastropod families. Malacologia 47 (1–2): 1–397.
[CV02] Canning, E. U., & J. Vavra. 2002. Phylum Microsporida Balbiani, 1882. In: Lee, J. J., G. F. Leedale & P. Bradbury (eds) An Illustrated Guide to the Protozoa: Organisms traditionally referred to as Protozoa, or newly discovered groups 2nd ed. vol. 1 pp. 39–126. Society of Protozoologists: Lawrence (Kansas).
[CH97] Castro, P., & M. E. Huber. 1997. Marine Biology 2nd ed. WCB McGraw-Hill: Boston.
[C12] Chen, J.-Y. 2012. Evolutionary scenario of the early history of the animal kingdom: evidence from Precambrian (Ediacaran) Weng’an and Early Cambrian Maotianshan biotas, China. In: Talent, J. A. (ed.) Earth and Life: Global biodiversity, extinction intervals and biogeographic perturbations through time pp. 239–379. Springer.
[D56] Dell, R. K. 1956. The archibenthal Mollusca of New Zealand. Dominion Museum Bulletin 18: 1–235.
[D78] Durham, J. W. 1978. The probable metazoan biota of the Precambrian as indicated by the subsequent record. Ann. Rev. Earth Planet Sci. 6: 21-42.
[D94] Dzik, J. 1994. Evolution of ‘small shelly fossils’ assemblages of the early Paleozoic. Acta Palaeontologica Polonica 39 (3): 247–313.
[E-J04] Eibye-Jacobsen, D. 2004. A reevaluation of Wiwaxia and the polychaetes of the Burgess Shale. Lethaia 37: 317–335.
[F71] Fletcher, H. O. 1971. Catalogue of type specimens of fossils in the Australian Museum, Sydney. Australian Museum Memoir 13: 1–167.
[GO06] Giribet, G., A. Okusu, A. R. Lindgren, S. W. Huff, M. Schrödl & M. K. Nishiguchi. 2006. Evidence for a clade composed of molluscs with serially repeated structures: monoplacophorans are related to chitons. Proceedings of the National Academy of Sciences of the USA 103 (20): 7723–7728.
[G79] Glaessner, M. F. 1979. Precambrian. In: Robison, R. A., & C. Teichert (eds) Treatise on Invertebrate Paleontology pt A. Introduction. Fossilisation (Taphonomy), Biogeography and Biostratigraphy pp. A79–A118. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).
[G20] Goldfuss, G. A. 1820. Handbuch der Naturgeschichte vol. 3. Handbuch der Zoologie pt 1. Johann Leonhard Schrag: Nürnberg.
[G84] Gruber, A. 1884. Die Protozoen des Hafens von Genua. Verhandlungen der Kaiserlichen Leopoldinisch-Carolinischen Deutschen Akademie der Naturforscher [Nova Acta Academiae Caesareae Leopoldino-Carolinae Germanicae Naturae Curiosorum] 46 (4): 473–539, pls 7–11.
[Ha62] Häntzschel, W. 1962. Trace fossils and problematica. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt W. Miscellanea: Conodonts, Conoidal Shells of Uncertain Affinities, Worms, Trace Fossils and Problematica pp. W177–W245. Geological Society of America, and University of Kansas Press.
[H75] Häntzschel, W. 1975. Treatise on Invertebrate Paleontology pt W. Miscellanea Suppl. 1. Trace Fossils and Problematica 2nd ed. The Geological Society of America: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).
[H56] Hartman, O. 1956. Polychaetous annelids erected by Treadwell, 1891 to 1948, together with a brief chronology. Bulletin of the American Museum of Natural History 109 (2): 239–310.
[H-S86] Hartmann-Schröder, G. 1986. Polychaeta (incl. Archiannelida). In: Botosaneanu, L. (ed.) Stygofauna Mundi: A Faunistic, Distributional, and Ecological Synthesis of the World Fauna inhabiting Subterranean Waters (including the Marine Interstitial) pp. 210–233. E. J. Brill/Dr W. Backhuys: Leiden.
[HS01] Hayward, B. W., A. B. Stephenson, M. S. Morley, W. M. Blom, H. R. Grenfell, F. J. Brook, J. L. Riley, F. Thompson & J. J. Hayward. 2001. Marine biota of Parengarenga Harbour, Northland, New Zealand. Records of the Auckland Museum 37: 45–80.
[H69] Hermans, C. O. 1969. The systematic position of the Archiannelida. Systematic Zoology 18 (1): 85–102.
[H64] Holl, H. B. 1864. On the metamorphic rocks of the Malvern Hills. Report of the British Association for the Advancement of Science 33 (Notices and Abstracts): 70–73.
[HG98] Holte, B., & B. Gulliksen. 1998. Common macrofaunal dominant species in the sediments of some north Norwegian and Svalbard glacial fjords. Polar Biology 19: 375–382.
[Ho62] Howell, B. F. 1962. Worms. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt W. Miscellanea: Conodonts, Conoidal Shells of Uncertain Affinities, Worms, Trace Fossils and Problematica pp. W144–W177. Geological Society of America, and University of Kansas Press.
[HG14] Hutchings, P., C. Glasby, M. Capa & A. Sampey. 2014. Kimberley marine biota. Historical data: polychaetes (Annelida). Records of the Western Australian Museum Supplement 84: 133–159.
[JB12] Johnson, M. E., & B. G. Baarli. 2012. Development of intertidal biotas through Phanerozoic time. In: Talent, J. A. (ed.) Earth and Life: Global biodiversity, extinction intervals and biogeographic perturbations through time pp. 63–128. Springer.
[J56] Jones, M. L. 1956. Cossura pygodactyla, a new annelid from San Francisco Bay (Polychaeta: Cirratulidae). Journal of the Washington Academy of Sciences 46 (4): 127–130.
[KBC03] Kashin, I. A., E. V. Bagaveeva & S. F. Chaplygina. 2003. Fouling communities of hydrotechnical constructions in Nakhodka Bay (Sea of Japan). Russian Journal of Marine Biology 29: 267–283.
[KA01] Kent, M. L., K. B. Andree, J. L. Bartholomew, M. El-Matbouli, S. S. Desser, R. H. Devlin, S. W. Feist, R. P. Hedrick, R. W. Hoffmann, J. Khattra, S. L. Hallett, R. J. G. Lester, M. Longshaw, O. Palenzuela, M. E. Siddall & C. Xiao. 2001. Recent advances in our knowledge of the Myxozoa. Journal of Eukaryotic Microbiology 48: 395–413.
[KM17] Korshunova, T., A. Martynov, T. Bakken, J. Evertsen, K. Fletcher, I. W. Mudianta, H. Saito, K. Lundin, M. Schrödl & B. Picton. 2017. Polyphyly of the traditional family Flabellinidae affects a major group of Nudibranchia: aeolidacean taxonomic reassessment with descriptions of several new families, genera, and species (Mollusca, Gastropoda). ZooKeys 717: 1–139.
[L95] Landing, E. 1995. Upper Placentian–Branchian series of mainland Nova Scotia (middle–upper Lower Cambrian): faunas, paleoenvironments, and stratigraphic revision. Journal of Paleontology 69 (3): 475–495.
[MF02] Martini, F. H., & D. Flescher. 2002. Hagfishes. Family Myxinidae. In: Collette, B. B., & G. Klein-MacPhee (eds) Bigelow and Schroeder’s Fishes of the Gulf of Maine 3rd ed. pp. 9–16. Smithsonian Institute Press: Washington.
[M01] M’Intosh, W. C. 1901. The coloration of marine animals. Annals and Magazine of Natural History, series 7, 7: 221–240.
[M13] M’Intosh, W. C. 1913. Notes from the Gatty Marine Laboratory, St. Andrews.—No. XXXV. Annals and Magazine of Natural History, series 8, 12: 153–181.
[M62] Monniot, F. 1962. Recherches sur les graviers a Amphioxus de la région de Banyuls-sur-Mer. Vie et Milieu 13: 231–322.
[PE16] Parry, L. A., G. D. Edgecombe, D. Eibye-Jacobsen & J. Vinther. 2016. The impact of fossil data on annelid phylogeny inferred from discrete morphological characters. Proceedings of the Royal Society of London Series B—Biological Sciences 283: 20161378.
[PTV14] Parry, L., A. Tanner & J. Vinther. 2014. The origin of annelids. Palaeontology 57 (6): 1091–1103.
[PP64] Peres, J. M., & J. Picard. 1964. Nouveau manuel de bionomie benthique de la mer Mediterranee. Recueil des Travaux de la Station Marine d’Endoume, Bulletin 31 (27): 5–137.
[PB02] Perkins, F. O., J. R. Barta, R. E. Clopton, M. A. Peirce & S. J. Upton. 2002. Phylum Apicomplexa Levine, 1970. In: Lee, J. J., G. F. Leedale & P. Bradbury (eds) An Illustrated Guide to the Protozoa: Organisms traditionally referred to as Protozoa, or newly discovered groups 2nd ed. vol. 1 pp. 190–369. Society of Protozoologists: Lawrence (Kansas).
[P71] Por, F. D. 1971. One hundred years of Suez Canal—a century of Lessepsian migration: retrospect and viewpoints. Systematic Zoology 20 (2): 138–159.
[PG98] Probert, P. K., & S. L. Grove. 1998. Macrobenthic assemblages of the continental shelf and upper slope off the west coast of South Island, New Zealand. Journal of the Royal Society of New Zealand 28: 259–280.
[R68] Reish, D. J. 1968. A biological survey of Bahia de Los Angeles, Gulf of California, Mexico. II. Benthic polychaetous annelids. Transactions of the San Diego Society of Natural History 15 (7): 67–106.
[R96] Roff, D. A. 1996. The evolution of threshold traits in animals. Quarterly Review of Biology 71 (1): 3–35.
Rouse, G. W., & K. Fauchald. 1997. Cladistics and polychaetes. Zoologica Scripta 26 (2): 139–204.
[RP07] Rousset, V., F. Pleijel, G. W. Rouse, C. Erséus & M. E. Siddall. 2007. A molecular phylogeny of annelids. Cladistics 23: 41–63.
[SRT18] Schiffer, P. H., H. E. Robertson & M. J. Telford. 2018. Orthonectids are highly degenerate annelid worms. Current Biology 28: 1970–1974.
[S79] Schram, F. R. 1979. Worms of the Mississippian Bear Gulch Limestone of central Montana, USA. Transactions of the San Diego Society of Natural History 19 (9): 107–120.
[SHB15] Smith, M. R., T. H. P. Harvey & N. J. Butterfield. 2015. The macro- and microfossil record of the Cambrian priapulid Ottoia. Palaeontology 58 (4): 705–721.
[SS07] Struck, T. H., N. Schutt, T. Kusen, E. Hickman, C. Bleidorn, D. McHugh & K. M. Halanych. 2007. Annelid phylogeny and the status of Sipuncula and Echiura. BMC Evolutionary Biology 7: 57.
[TS02] Tsetlin, A. B., & M. V. Safonov. 2002. Interstitial polychaetes (Annelida) from the Kandalaksha Bay of the White Sea. Zoologicheskii Zhurnal 81 (8): 899–908.
[W93a] Wills, M. A. 1993a. ?Mollusca incertae sedis. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 265–270. Chapman & Hall: London.
[W93b] Wills, M. A. 1993b. Annelida. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 271–278. Chapman & Hall: London.
[WS93] Wills, M. A., & J. J. Sepkoski Jr. 1993. Problematica. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 543–554. Chapman & Hall: London.