Tactopoda information

Tactopoda; Temporal range: Fortunian–Present PreꞒ Ꞓ O S D C P T J K Pg N
	The tardigrade Hypsibius dujardini
	The blue crab Callinectes sapidus, an arthropod
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Subkingdom:	Eumetazoa
Clade:	ParaHoxozoa
Clade:	Bilateria
Clade:	Nephrozoa
(unranked):	Protostomia
Superphylum:	Ecdysozoa
(unranked):	Panarthropoda
(unranked):	Tactopoda; Budd, 2001

Tactopoda or Arthropodoidea is a proposed clade of protostome animals that includes the phyla Tardigrada and Euarthropoda, supported by various morphological observations.^[1]^[2]^[3] The cladogram below shows the relationships implied by this hypothesis.

Panarthropoda

Onychophora

Tactopoda

	Tardigrada

	Euarthropoda

The competing hypothesis is that Antennopoda^[4]^[5] (= Euarthropoda + Onychophora, the arthropods and the velvet worms) is monophyletic,^[6] and tardigrades lie outside this grouping.

Panarthropoda

Tardigrada

Antennopoda

	Onychophora

	Euarthropoda

Anatomic arguments for the tactopoda monophyly include similarities in the anatomies of head, legs, and muscles between the arthropods and the tardigrades. Anatomic arguments against it include that tardigrades lack the kind of circulatory system (including a dorsal heart) which the arthropods and the velvet worms share. Graham Budd argued that the lack of this system in recent tardigrades is due to their miniature size, which makes a complex circulatory system superfluous; thus, the loss of this feature would be a secondary property, acquired as the tardigrade stem group turned smaller, and both the Euarthropoda+Onychophora circulatory system and a relatively large size should be a feature of the last common ancestor of all three groups.^[1] However, Gregory Edgecombe also invoked phylogenomic evidence in favour of the alternative Euarthropoda+Onychophora grouping.^[6]

^ ^a ^b ^c Graham E. Budd (2001). "Tardigrades as 'stem-group arthropods': the evidence from the Cambrian fauna" (PDF). Zoologischer Anzeiger. 240 (3–4): 265–279. doi:10.1078/0044-5231-00034. Archived from the original (PDF) on 2016-03-03.
'^ Smith, M. R.; Ortega-Hernández, J. (2014). "Hallucigenias onychophoran-like claws and the case for Tactopoda". Nature. 514 (7522): 363–366. Bibcode:2014Natur.514..363S. doi:10.1038/nature13576. PMID 25132546. S2CID 205239797.
^ De Haro, A. (1998). "Origen y relaciones fitogenéticas entre Artrópodos, Onicóforos, Anélidos y Lofoforados, según datos moleculares y morfológicos". Boletín de la Real Sociedad Española de Historia Natural Sección Biológica. 94 (1–2): 103–113.
^ Smith, Frank W.; Goldstein, Bob (2017-05-01). "Segmentation in Tardigrada and diversification of segmental patterns in Panarthropoda". Arthropod Structure & Development. Evolution of Segmentation. 46 (3): 328–340. Bibcode:2017ArtSD..46..328S. doi:10.1016/j.asd.2016.10.005. ISSN 1467-8039. PMID 27725256.
^ Ortega-Hernández, Javier (2014-12-21). "Making sense of 'lower' and 'upper' stem-group Euarthropoda, with comments on the strict use of the name Arthropoda von Siebold, 1848: Upper and lower stem-Euarthropoda". Biological Reviews. 91 (1): 255–273. doi:10.1111/brv.12168. PMID 25528950. S2CID 7751936.
^ ^a ^b Gregory D. Edgecombe (2010). "Arthropod phylogeny: An overview from the perspectives of morphology, molecular data and the fossil record". Arthropod Structure & Development. 39 (2–3): 74–87. Bibcode:2010ArtSD..39...74E. doi:10.1016/j.asd.2009.10.002. PMID 19854297.

[Budd-1] Graham E. Budd (2001). "Tardigrades as 'stem-group arthropods': the evidence from the Cambrian fauna" (PDF). Zoologischer Anzeiger. 240 (3–4): 265–279. doi:10.1078/0044-5231-00034. Archived from the original (PDF) on 2016-03-03.

[SOH2014-2] '^ Smith, M. R.; Ortega-Hernández, J. (2014). "Hallucigenias onychophoran-like claws and the case for Tactopoda". Nature. 514 (7522): 363–366. Bibcode:2014Natur.514..363S. doi:10.1038/nature13576. PMID 25132546. S2CID 205239797.

[:0-3] De Haro, A. (1998). "Origen y relaciones fitogenéticas entre Artrópodos, Onicóforos, Anélidos y Lofoforados, según datos moleculares y morfológicos". Boletín de la Real Sociedad Española de Historia Natural Sección Biológica. 94 (1–2): 103–113.

[4] Smith, Frank W.; Goldstein, Bob (2017-05-01). "Segmentation in Tardigrada and diversification of segmental patterns in Panarthropoda". Arthropod Structure & Development. Evolution of Segmentation. 46 (3): 328–340. Bibcode:2017ArtSD..46..328S. doi:10.1016/j.asd.2016.10.005. ISSN 1467-8039. PMID 27725256.

[5] Ortega-Hernández, Javier (2014-12-21). "Making sense of 'lower' and 'upper' stem-group Euarthropoda, with comments on the strict use of the name Arthropoda von Siebold, 1848: Upper and lower stem-Euarthropoda". Biological Reviews. 91 (1): 255–273. doi:10.1111/brv.12168. PMID 25528950. S2CID 7751936.

[Edgecombe-6] Gregory D. Edgecombe (2010). "Arthropod phylogeny: An overview from the perspectives of morphology, molecular data and the fossil record". Arthropod Structure & Development. 39 (2–3): 74–87. Bibcode:2010ArtSD..39...74E. doi:10.1016/j.asd.2009.10.002. PMID 19854297.

Tactopoda information

and 26 Related for: Tactopoda information

Tactopoda

Protostome

Bilateria

Panarthropoda

Arthropod

Lists of animals

Ecdysozoa

Hallucigenia

Tardigrade

Onychophora

Eumetazoa

Priapulida

List of bilaterian orders

Lobopodia

Maotianshan Shales

Chuandianella

Opabinia

Antennopoda

Erratus

Onychodictyon

2023 in paleontology

Hallucigeniidae

Luolishania

Diania

Archeolimulus

Thanahita

Tactopoda Temporal range: Fortunian–Present PreꞒ Ꞓ O S D C P T J K Pg N

The tardigrade Hypsibius dujardini

The blue crab Callinectes sapidus, an arthropod
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Subkingdom:	Eumetazoa
Clade:	ParaHoxozoa
Clade:	Bilateria
Clade:	Nephrozoa
(unranked):	Protostomia
Superphylum:	Ecdysozoa
(unranked):	Panarthropoda
(unranked):	Tactopoda Budd, 2001 ^[1]