Protodriliformia

Protodriliformia
	Protodrilus mirabilis
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Annelida
Clade:	Pleistoannelida
Subclass:	Errantia
Clade:	Protodriliformia; Struck et al. 2015
Orders and families
	Polygordiidae; Protodrilida Protodrilidae; Protodriloidae; Saccocirridae; ;

Protodriliformia is a clade of small marine polychaetes, comprised by the groups of meiofaunal interstitial worms Protodrilida and Polygordiidae, formerly considered "archiannelids". It is the most basal clade of Errantia.^[1]^[2]

Evolutionary history

Phylogenetic analysis of annelids has found Protodriliformia to be the earliest diverging clade of Errantia. At the same time, the other half of "archiannelid" worms, Orbiniida, was found to be the earliest diverging clade of Sedentaria. The convergence between these two groups occurred through progenesis and miniaturization, as a way to adapt to the marine interstitial ecosystem between sand grains (i.e. interstitium). This means that the larval or juvenile stages of a larger pleistoannelid ancestor temporarily inhabiting the interstitium stopped their somatic growth, became sexually mature and stayed in the interstitium permanently.^[1]

Protodriliformia

	Protodriloididae

	Protodrilidae

Saccocirridae

Polygordiidae

Sedentaria

	Orbiniida

	other Sedentaria

'Archiannelids'

References

^ ^a ^b ^c Struck TH, Golombek A, Weigert A, Franke FA, Westheide W, Purschke G, Bleidorn C, Halanych KM (3 August 2015). "The evolution of annelids reveals two adaptive routes to the interstitial realm". Curr Biol. 25 (15): 1993–1999. doi:10.1016/j.cub.2015.06.007. PMID 26212885.
^ Struck TH (2019). "Phylogeny". In Purschke G, Böggemann M, Westheide W (eds.). Handbook of Zoology: Annelida. Vol. 1: Annelida Basal Groups and Pleistoannelida, Sedentaria I. De Gruyter. doi:10.1515/9783110291582-002. ISBN 9783110291469.

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[Two_adaptive_routes_Annelida-1] Struck TH, Golombek A, Weigert A, Franke FA, Westheide W, Purschke G, Bleidorn C, Halanych KM (3 August 2015). "The evolution of annelids reveals two adaptive routes to the interstitial realm". Curr Biol. 25 (15): 1993–1999. doi:10.1016/j.cub.2015.06.007. PMID 26212885.

[Handbook_Zoology_Annelida_1-2] Struck TH (2019). "Phylogeny". In Purschke G, Böggemann M, Westheide W (eds.). Handbook of Zoology: Annelida. Vol. 1: Annelida Basal Groups and Pleistoannelida, Sedentaria I. De Gruyter. doi:10.1515/9783110291582-002. ISBN 9783110291469.

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