View source for Vetulicolia

{{short description|Extinct Cambrian group of animals}}
{{not to be confused with|Vetulicola}}
{{Automatic taxobox
| fossil_range = about {{Fossilrange|earliest=545|520|501}} [[Cambrian Stage 3]]—[[Drumian]]
(Possible [[Ediacaran]] record)<ref name=Liu2024>{{harvnb|Liu|Chen|Li|Tang|2024}} {{small|(Note that while the paper leaves the classification of ''Alienum'' uncertain in its systematic paleontology, it also states on page 4 that "''Alienum velamenus'' might belong to a clade of extinct Vetulicolia that formed during the early evolution of ''Vetulicola''." It is tentatively included here on these grounds.)}}</ref>
| image = {{multiple image|direction=vertical|total_width=270
   | image1 = Vetulicola cuneata ウェツリコラ クニエータ 1.jpg
   | caption1  = Fossil of ''[[Vetulicola cuneata]]''
   | image2 = Banffia-constricta-fossils.png
   | caption2 = ''Fossil of [[Banffia constricta]]''
   | image3 = Didazoon haoae.jpg
   | caption3 = ''[[Didazoon haoae]]''
   | border = infobox
   | footer = Restorations and fossils of vetulicolians
}}
| authority = Shu ''et al.'' 2001
| taxon = Vetulicolia
| type_species = †''[[Vetulicola cuneata]]''
| type_species_authority = Hou, 1987
| subdivision_ranks = Classes
| subdivision = * {{extinct}}[[Banffozoa]]
* {{extinct}}[[Vetulicolida]]
* ''[[incertae sedis]]''
** ? {{extinct}}''[[Alienum]]''
** {{extinct}}''[[Shenzianyuloma]]''
}}

'''Vetulicolia''' is a group of [[bilaterian]] marine [[animal]]s encompassing several [[extinct]] species from the [[Cambrian]],<ref name=Gee2018>{{harvnb|Gee|2018|pages=188–189}}</ref> and possibly [[Ediacaran]],<ref name=Liu2024 /> periods.  As of 2023, the majority of scientists favor placing Vetulicolians in the [[stem group]] of the [[Chordata]],<ref name=Onai2023>{{harvnb|Onai|Aramaki|Takai|Kakiguchi|2023|page=202}}</ref> but some continue to favor a more [[crown group|crownward]] placement as a sister group to the [[Tunicata]].<ref name=Gee2018 />  It was initially erected as a [[monophyletic]] [[clade]] with the [[taxonomic rank|rank]] of [[phylum]] in 2001,<ref name="Shu2001">{{harvnb|Shu|Conway Morris|Han|Chen|2001}}</ref> with subsequent work supporting its monophyly.<ref>{{harvnb|Aldridge|Hou|Siveter|Siveter|2007|page=154}}</ref>  However, more recent research suggests that vetulicolians may be [[paraphyletic]] and form a basal [[evolutionary grade]] of stem chordates.<ref name="Mussini2024">{{harvnb|Mussini|Smith|Vinther|Rahman|2024}}</ref>

==Etymology==
The taxon name, Vetulicolia, is derived from the type genus, ''[[Vetulicola]]'', which is a compound [[Latin]] word composed of ''vetulus'' "old" and ''-cola'' "inhabitant".  It was named after ''[[Vetulicola cuneata]]'', the first species of the group described in 1987.<ref>{{harvnb|Lacalli|2002|page=208}}</ref>

==Description==
[[File:Ou et al. 2012 f07.jpg|thumb|left|Schematic of ''V. rectangulata''<br />{{small|pharynx and alimentary canal: dashed line; ventral food grooves: dotted line; gill slits: pink}}]]

The vetulicolian [[body plan]] comprises two parts: a voluminous [[rostral (anatomical term)|rostral]] ([[anatomical terms of location|anterior]]) forebody, tipped with an anteriorly positioned [[mouth]] and lined with a lateral row of five round to oval-shaped openings on each side, which have been interpreted as [[gill]]s (or at least [[body orifice|orifice]]s in the vicinity of the [[pharynx]]); and a [[caudal (anatomical term)|caudal]] ([[posterior (anatomy)|posterior]]) section that primitively comprises seven [[body segment]]s and functions as a [[tail]]. All vetulicolians lack preserved [[appendage]]s of any kind, having no legs, feelers or even [[simple eye in invertebrates|eye spot]]s.<ref name=Chen2003>{{harvnb|Chen|Feng|Zhu|Ma|2003}}</ref> The area where the anterior and posterior parts join is constricted in most genera.<ref>{{harvnb|Conway Morris|Halgedahl|Selden|Jarrard|2015|pages=3–4}}</ref><ref>{{harvnb|Aldridge|Hou|Siveter|Siveter|2007|page=133}}</ref> [[Notochord]]-like structures have been found in some vetulicolian fossils.<ref name=GB2014>{{harvnb|García-Bellido|Lee|Edgecombe|Jago|2014}}</ref>

== Ecology and lifestyle ==
From their superficially tadpole-like forms, leaf or paddle-shaped tails, and various degrees of streamlining, it is assumed that all vetulicolians discovered to date were swimming animals that spent much, if not all, of their time living in water.<ref name=Aldridge>{{harvnb|Aldridge|Hou|Siveter|Siveter|2007}}</ref> Some groups, like the genus ''Vetulicola'', were more streamlined (complete with ventral [[keel]]s) than other groups, such as the tadpole-like [[Didazoonidae]].<ref name=Aldridge />

Because all vetulicolians had mouths which had no features for chewing or grasping, it is assumed that they were not predators.<ref name="Aldridge" /> Since vetulicolians possessed gill slits, many researchers regard these organisms as [[planktivores]]. The sediment infills in the guts of their fossils have caused some to suggest that they were deposit feeders. This idea has been contested, as deposit feeders tend to have straight guts, whereas the hindguts of vetulicolians were spiral-shaped. Some researchers propose that the vetulicolians were "selective deposit-feeders" which actively swam from one region of the seafloor to another, while supplementing their nutrition with filter-feeding.<ref name="Aldridge" />

The earliest vetulicolians appear to have lived in shallow water, with the first deeper water specimens appearing in the Balang biota and possibly in the [[Qingjiang biota]].<ref name="MaEtAl2025">The first deep water vetulicolians were described by [[Shuhan Ma]] in: {{cite journal |last=Ma |first=Shuhan |author2=Julien Kimmig |author3=James D. Schiffbauer |author4=Ruibo Li |author5=Shanchi Peng |author6=Xianfeng Yang |date=22 January 2025 |title=Deep water vetulicolians from the lower Cambrian of China |journal=[[PeerJ]] |volume=13 |doi=10.7717/peerj.18864 |pmc=11760202 |pmid=39866560 |doi-access=free |article-number=e18864}}</ref>

==Taxonomy and evolution==
{{multiple image
| direction         = vertical
| header            = Banffozoans
| image1            = Banffia constricta.JPG
| caption1          = Life restoration of ''[[Banffia constricta]]''
| image2            = Skeemella clavula KUMIP 310501.jpg
| caption2          = Fossil of ''[[Skeemella clavula]]''
}}

The phylum Vetulicolia was erected in 2001 to group the genera ''Vetulicola'', ''Didazoon'', and ''Xidazoon'' (later deemed a junior synonym of ''Pomatrum'').<ref name=flowering>{{harvnb|Hou|Siveter|Siveter|Aldridge|2017|page=272}}</ref>  Prior to this the [[class (biology)|class]] Vetulicolida had been defined in 1997 to group ''Vetulicola'' with the previously enigmatic genus ''[[Banffia]]'' due to its similar two-part construction, as well as apparent gill slits in a newly discovered specimen.<ref>{{harvnb|Chen|Zhou|1997|pages=95–96}}</ref>  Further work split ''Banffia'' into a separate class called [[Banffozoa]], which was soon expanded to encompass similar species such as ''Heteromorphus''.<ref>{{harvnb|Aldridge|Hou|Siveter|Siveter|2007|pages=151–152}} {{small|(Note: See [[Banffozoa#Preference for Banffozoa over Heteromorphida]] regarding whether Banffozoa or Heteromorphida is the preferred name.)}}</ref>
While subsequent studies supported the [[monophyly]] of Vetulicolia, it has also been noted that this would preclude vetulicolians representing a stepwise development of deuterostome characteristics, as the genus with the most such characteristics, ''Vetulicola'', is one of the most derived in the group.<ref name=flowering />

A 2024 phylogenetic analysis by Mussini and colleagues found vetulicolians to be a [[paraphyletic]] group of [[Stem group|stem]]-chordates, lying outside a clade formed by ''[[Yunnanozoon]]'', ''[[Cathaymyrus]]'', ''[[Pikaia]]'' and [[Crown group|crown]]-chordates.<ref name="Mussini2024"/> This is in part due to the [[Cambroernida]], which are basal stem-[[ambulacrarians]], being discovered to share with vetulicolians a lack of crown-group chordate characters such as a post-anal tail, despite such characteristics previously being believed to be present in the last common ancestor of deuterostomes.<ref name=ancestral>{{harvnb|Mussini|Smith|Vinther|Rahman|2024|page=6}}</ref> However, ascidian larvae have been noted to have endoderm extending to the terminal end, which could suggest that the ancestral tunicate also had a terminal anus.<ref name="GB2014" />

Other possible placements are suggested by the [[Centroneuralia]] hypothesis, which features a paraphyletic [[Deuterostomia]] with chordates as the sister-group to protostomes.  If proven true, pharyngeal slits would no longer require a deuterostome placement and vetulicolians could prove to be stem protostomes that lost the post-anal tail.  In such a scenario, Banffozoa could be a more derived stem protostome group than Vetulicolida.<ref>{{harvnb|Kapli|Natsidis|Leite|Fursman|2021|page=6}}</ref>

===Cladograms===
The following cladograms show two possible placements of the Vetulicolia.

First, on the left, a monophyletic Vetulicolia is shown as the sister group to [[Tunicata]], but with all internal relationships unresolved.<ref>{{harvnb|García-Bellido|Lee|Edgecombe|Jago|2014|page=9}}</ref>

Next, on the right, the two proposed classes are shown as the earlier (Banffozoa) and later (Vetulicolida) parts of the vetulicolian grade.<ref name=MussiniCladogram>{{harvnb|Mussini|Smith|Vinther|Rahman|2024|pages=6–7}}</ref> Within the Vetulicolida, the family Vetulicolidae as defined by Li ''et al.'' (2018)<ref name=Li2018>{{harvnb|Li|Williams|Gabbott|Chen|2018|pages=1083–1084}} {{small|(Note: See [[Banffozoa#Preference for Banffozoa over Heteromorphida]] regarding the use of Heteromorphida in this classification.)}}</ref> is recovered as monophyletic, while the three widely accepted members of the [[Didazoonidae]]<ref name=Didazoonidae>{{cite web|title=†family Didazoonidae Shu and Han 2001 |website=Paleobiology Database |url=https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=txn:378668 |accessdate=December 8, 2024}}</ref> are in a [[polytomy]] with the clade of crownward chordates.

The possible presence of a notochord in ''Nesonektris'' and the lack of clear evidence for one in ''Pikaia'' is relevant to the validity of the following cladograms.  Proponents of a monophyletic Vetulicolia as the sister group of Tunicata note that scoring the notochord as "unknown" in ''Nesonektris'' produces the same topology, albeit with less support for certain nodes.<ref>{{harvnb|García-Bellido|Lee|Edgecombe|Jago|2014|page=10}}</ref>  Proponents of a paraphyletic Vetulicolia, who assume that both ''Pikaia'' and ''Nesonektris'' lacked a notochord, similarly note that scoring ''Nesonektris'' as having a notochord did not significantly change their topology.<ref>{{harvnb|Mussini|Smith|Vinther|Rahman|Murdock|Harper|Dunn|2024|loc=supplemental data figure S4, tree B}}</ref>  They also noted that fossils of unambiguous crown-group chordates also frequently lack a visible notochord,<ref>{{harvnb|Mussini|Smith|Vinther|Rahman|Murdock|Harper|Dunn|2024|page=3}}</ref> but the paper cited regarding this lack lists the notochord as one of the last anatomical structures to decay, with other structures preserved in ''Pikaia'' more likely to decay more quickly.<ref>{{harvnb|Sansom|Gabbott|Purnell|2010|pages=798–799}}</ref> Alternatively, a separate paper examining hypotheses regarding a notochord in ''Pikaia'' notes that it may have been lost as other structures evolved to take over its function.<ref>{{harvnb|Lacalli|2024|page=10}}</ref>

{{col-float}}
<!-- empty barlabel needed to keep this cladogram and the next displaying at the same level -->
{{barlabel|style=font-size:80%;line-height:80%
|cladogram={{Cladogram
   |title=Simplified from García-Bellido ''et al.'' (2014)
   |clades={{Clade
      |label1=[[Chordata]]
      |1={{Clade
         |1=[[Cephalochordata]]
         |label2=[[Olfactores]]
         |2={{Clade
            |label1=[[Vertebrata]]
            |sublabel1={{small|([[total group]])}}
            |1={{Clade
               |1=[[Yunnanozoa]]†
               |2={{Clade
                  |1=''[[Pikaia]]''†
                  |2={{Clade
                     |1=[[Conodonta]]†
                     |2=[[Vertebrata]]<br />{{small|([[crown group]])}}
                  }}
               }}
            }}
            |label2=[[Tunicata]]
            |sublabel2={{small|([[total group]])}}
            |2={{Clade
               |label1='''Vetulicolia'''†
               |1={{Clade
                  |1=''[[Vetulicola]]''†
                  |2=''[[Pomatrum]]''† / ''[[Xidazoon]]''†
                  |3=''[[Didazoon]]''†
                  |4=''[[Beidazoon]]''†
                  |5=''[[Yuyuanozoon]]''†
                  |6=''[[Banffia]]''†
                  |7=''[[Heteromorphus]]''†
                  |8=''[[Ooedigera]]''†
                  |9=''[[Nesonektris]]''†
               }} 
               |2=[[Tunicata]]<br />{{small|([[crown group]])}}
      }} }} }}
      |label2=[[Ambulacraria]]
      |2={{Clade
         |1=[[Enteropneusta]]
         |2=[[Echinodermata]]
}} }}
}} }}
{{col-float-break}}
{{barlabel|style=font-size:80%;line-height:80%
|size=27
|at1=0 |label1="Banffozoa" |bar1=indigo
|at2=6 |label2="Vetulicolida" |bar2=purple
|cladogram={{cladogram
   |title=Simplified from Mussini ''et al.'' (2024)
   |clades={{Clade
      |label1=[[Chordata]]
      |sublabel1={{small|([[total group]])}}
      |1={{Clade
         |1=''[[Banffia]]''† |barbegin1=indigo
         |2=''[[Heteromorphus]]''† |bar2=indigo
         |3={{Clade
            |1=''[[Skeemella]]''† |barend1=indigo
            |2={{Clade
               |1=''[[Nesonektris]]''† |barbegin1=purple
               |2={{Clade
                  |label1=[[Vetulicolidae]]†
                  |1={{Clade
                     |1=''[[Ooedigera]]''†
                     |2={{Clade
                        |1=''[[Vetulicola cuneata]]''†
                        |2=''[[Vetulicola gantoucunensis]]''†
                        |3=''[[Vetulicola longbaoshanensis]]''†
                        |4=''[[Vetulicola rectangulata]]''†
                        |5={{Clade
                           |1=''[[Vetulicola monile]]''†
                           |2=''[[Beidazoon]]''†
                     }} }} }} |bar1=purple
                  |2={{Clade
                     |1=''[[Didazoon]]''† |bar1=purple
                     |2=''[[Pomatrum]]''† |bar2=purple
                     |3=''[[Yuyuanozoon]]''† |barend3=purple
                     |4={{Clade
                        |1=''[[Yunnanozoon]]''†
                        |2={{Clade
                           |1=''[[Cathaymyrus]]''†
                           |2=''[[Pikaia]]''†
                           |label3=[[Chordata]]
                           |sublabel3={{small|([[crown group]])}}
                           |3={{Clade
                              |1=[[Lancelet|Cephalochordata]]
                              |2={{Clade
                                 |1=[[Tunicate|Tunicata]]
                                 |2={{Clade
                                    |1=''[[Metaspriggina]]''†
                                    |2={{Clade
                                       |1=''[[Myllokunmingia]]''†
                                       |2=[[Vertebrate|Vertebrata]]
      }} }} }} }} }} }} }} }} }} }} }}
      |label2=[[Ambulacraria]]
      |sublabel2={{small|([[total group]])}}
      |2={{Clade
         |label1=[[Cambroernida]]†
         |1={{Clade
            |1=''[[Herpetogaster]]''†
            |2={{Clade
               |1=''[[Phlogites]]''†
               |2=[[Eldonioidea]]†
            }}
         }}
         |label2=[[Ambulacraria]]
         |sublabel2={{small|([[crown group]])}}
         |2={{Clade
            |1=[[Hemichordata]]
            |2=[[Echinodermata]]
}} }} }} }}
}}
{{col-float-end}}

=== Classification ===
{{ external media
| headerimage=
| float  = right
| width  = 320px
| video1 = [https://www.youtube.com/watch?v=KBzlkPS7ZUw&ab_channel=Kiabugboy Cambrian Not-Fishes (3D Paleoart)] - ''YouTube''
}}

The following classification is taken from Li ''et al.'' (2018)<ref name=Li2018 /> except where noted.

* Phylum '''Vetulicolia''' {{small|Shu ''et al.'' 2001}}<ref>{{harvnb|Shu|2005|page=2346}}</ref>
** ? Genus ''[[Alienum]]'' {{small|Liu ''et al.'' 2024}}<ref name="Liu2024" />
*** ''[[Alienum velamenus|A. velamenus]]'' {{small|Liu ''et al.'' 2024}}
** Genus ''[[Shenzianyuloma]]'' {{small|McMenamin 2019}}<ref>{{harvnb|McMenamin|2019|page=11}}</ref>
*** ''[[Shenzianyuloma yunnanense|S. yunnanense]]'' {{small|McMenamin 2019}}
** Class [[Heteromorphida]] {{small|Shu 2005}} (= [[Banffozoa]] {{small|Caron 2006}})<ref name=Li2018 /><!-- repeated here for the note about Banffozoa vs Heteromorphida -->
*** [[Banffozoa#Form A|"Form A"]] {{small|Shu 2005}}<ref>{{harvnb|Shu|2005|page=2349}} {{small|(Note: Shu assigned "Form A" to class Heteromorphida, but not to ''Heteromorphus'' on account of its very small size, highly sclerotized shell, and details of the anterior section; no order or family was specified; see also [[Banffozoa#Preference for Banffozoa over Heteromorphida]])}}</ref>
*** Order [[Banffiata]] {{small|Aldridge ''et al.'' 2007}}
**** Family [[Banffiidae]] {{small|Caron 2006}}<ref name=Caron2005 /><ref>{{cite web |title=†family Banffiidae Caron 2006 |website=Paleobiology Database |url=https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=txn:425116 |access-date=2024-12-17}}</ref>
***** Genus ''[[Banffia]]'' {{small|Walcott 1911}}
****** ''[[Banffia constricta|B. constricta]]'' {{small|Walcott 1911}}
****** ''[[Banffia episoma|B. episoma]]'' {{small|Conway Morris and Selden 2015}}
***** Genus ''[[Heteromorphus]]'' {{small|Luo and Hu ''in'' Luo ''et al.'' 1999}}
****** ''[[Heteromorphus confusus|H. confusus]]'' {{small|Chen and Zhou 1997}} (= ''[[Banffia confusa]]'') {{small|Chen and Zhou 1997}}; = ''[[Heteromorphus longicaudatus|H. longicaudatus]]'' {{small|Luo and Hu ''in'' Luo ''et al.'' 1999}})
***** Genus ''[[Skeemella]]'' {{small|Briggs ''et al.'' 2005}}
****** ''[[Skeemella clavula|S. clavula]]'' {{small|Briggs ''et al.'' 2005}}
** Class [[Vetulicolida]] {{small|Chen and Zhou 1997}}
*** Genus ''[[Nesonektris]]'' {{small|García-Bellido ''et al.'' 2014}}<ref name="GB2014" /><ref>{{cite web|title=†Nesonektris García-Bellido et al. 2014 |website=Paleobiology Database |url=https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=txn:358335 |accessdate=December 8, 2024}}</ref>
**** ''[[Nesonektris aldridgei|N. aldridgei]]'' {{small|García-Bellido ''et al.'' 2014}}
*** Order [[Vetulicolata]] {{small|Hou and Bergström 1997}}
**** Family [[Vetulicolidae]] {{small|Hou and Bergström 1997}}
***** Genus ''[[Vetulicola]]'' {{small|Hou 1987}}
****** ''[[Vetulicola cuneata|V. cuneata]]'' {{small|Hou 1987}}
****** ''[[Vetulicola rectangulata|V. rectangulata]]''  {{small|Luo and Hu ''in'' Luo ''et al.'' 1999}}
****** ''[[Vetulicola gantoucunensis|V. gantoucunensis]]'' {{small|Luo ''et al.'' 2005}}
****** ''[[Vetulicola monile|V. monile]]'' {{small|Aldridge ''et al.'' 2007}}
****** ''[[Vetulicola longbaoshanensis|V. longbaoshanensis]]'' {{small|Yang ''et al.'' 2010}}
***** Genus ''[[Ooedigera]]'' {{small|Vinther ''et al.'' 2011}}
****** ''[[Ooedigera peeli|O. peeli]]'' {{small|Vinther ''et al.'' 2011}}
***** Genus ''[[Beidazoon]]'' {{small|Shu 2005}} (= ''[[Bullivetula]]'' {{small|Aldridge ''et al.'' 2007}})
****** ''[[Beidazoon venustum|B. venustum]]'' {{small|Shu 2005}} (= ''[[Bullivetula variola|B. variola]]'' {{small|Aldridge ''et al.'' 2007}})
**** Family [[Didazoonidae]] {{small|Shu and Han ''in'' Shu ''et al.'', 2001}}
***** Genus ''[[Didazoon]]'' {{small|Shu and Han ''in'' Shu ''et al.'', 2001}}
****** ''[[Didazoon|D. haoae]]'' {{small|Shu and Han ''in'' Shu ''et al.'', 2001}}
***** Genus ''[[Pomatrum]]'' {{small|Luo and Hu, ''in'' Luo ''et al.'' 1999}} (= ''[[Xidazoon]]'' {{small|Shu, Conway Morris and Zhang ''in'' Shu ''et al.'' 1999}})
****** ''[[Pomatrum|P. ventralis]]'' {{small|Luo and Hu, ''in'' Luo ''et al.'' 1999}} (= ''[[Xidazoon stephanus|X. stephanus]]'' {{small|Shu, Conway Morris and Zhang ''in'' Shu ''et al.'' 1999}})
***** Genus ''[[Yuyuanozoon]]'' {{small|Chen, Feng and Zhu ''in'' Chen ''et al.'', 2003}}
****** ''[[Yuyuanozoon|Y. magnificissimi]]'' {{small|Chen, Feng and Zhu ''in'' Chen ''et al.'', 2003}}

===History of identification===
[[File:Ou et al. 2012 f06.jpg|thumb|Evidence for the presence of a pharynx and dorsal/ventral feeding gutters in vetulicolians, supporting their placement among the [[Deuterostomes]].  Click through for detailed description.]]
The current consensus view is that vetulicolians are [[stem group]] [[chordates]], although some researchers continue to raise other possibilities.<ref name=Onai2023 />  The possible identification of an [[endostyle]] bolstered theories of a [[tunicate]] affinity, but was later retracted, while the tentative identification of a [[notochord]] in ''[[Nesonektris]]'' and ''[[Vetulicola]]'' has further supported overall chordate affinities.<ref name=Gee2018 /><ref name="GB2014" /> Other characters that have been used to support a tunicate affinity include the limiting of the notochord to the tail and the presence of a stiff cuticle (tunic).<ref name="GB2014" />

Recent research has strengthened the arguments for placing vetulicolians in the chordate stem lineage rather than near the tunicates.  Like vetulicolians, members of the [[basal (phylogenetics)|basal]] [[ambulacrarian]] clade [[Cambroernida]] have a terminal anus rather than a post-anal tail.  Since Ambulacraria is the sister-group of the chordates within the deuterostomes, this suggests that the last common ancestor of both groups lacked a post-anal tail.<ref name=ancestral /> However, ascidian larvae have been noted to have endoderm extending to the terminal end, which could suggest that tunicates also lacked post-anal tails ancestrally.<ref name="GB2014" />

Some workers have questioned the inclusion of Banffozoa within this group due to their lack of gill slits and apparent gut diverticula, and have theorized that they may fit within Protostomia instead.<ref name=Caron2005>{{harvnb|Caron|2005}}</ref> ''[[Skeemella]]'', in particular, has been noted as having striking arthropod-like characteristics.<ref>{{harvnb|Shu|2005|page=2352}}</ref> However, ''[[Herpetogaster]]'', the most basal cambroernid, is thought to have non-serialized pores for pharyngial openings.  If banffozoans are the most basal vetulicolians, this could explain why they also lack serialized pharyngeal structures.<ref name=ancestral /> Additionally, a comprehensive review of the Vetulicolia in 2007 did not find evidence of gut diverticula in their material while acknowledging the previous report regarding ''Banffia''.<ref>{{harvnb|Aldridge|Hou|Siveter|Siveter|2007|pages=151–152}}</ref>  ''[[Shenzianyuloma]]'' has been interpreted as a vetulicolian with both a notochord (a definitively deuterostome trait) and gut diverticula. However, the single fossil of this genus is of unusual provenance (a "crystal and fossil vendor"), and has not yet been examined by other researchers.<ref>{{harvnb|McMenamin|2019|pages=15–16}}</ref>

{{thumb|width=450|content=<div style="text-align:left;">
</div>
{{Clade|style=font-size:75%;line-height:75%
   |label1=Protostomia
   |1={{Clade
      |1=[[Spiralia]]
      |label2=[[Ecdysozoa]]
      |2={{Clade
         |label1=[[Kinorhyncha]]
         |sublabel1={{small|([[total group]])}}
         |1={{Clade
            |label1=
            |1=? Vetulicolia† |state1=dashed
            |2=[[Kinorhyncha]]<br />{{small|([[crown group]])}}
         }}
         |label2=[[Panarthropoda]]
         |2={{Clade
            |label1=
            |1=? Vetulicolia† |state1=dashed
            |2={{Clade
               |1=[[Onychophora]]
               |2={{Clade
                  |1={{Clade
                     |label1=
                     |1=? Vetulicolia† |state1=dashed
                     |2=[[Anomalocaridid|Anomalocaridida]]†
                  }}
                  |label2=[[Arthropoda]]
                  |sublabel2={{small|([[total group]])}}
                  |2={{Clade
                     |label1=
                     |1=? Vetulicolia† |state1=dashed
                     |2=[[Arthropoda]]<br />{{small|([[crown group]])}}
                  }}
               }}
            }}
         }}
      }}
   }}
   |label2=[[Deuterostomia]]
   |2={{Clade
      |1=? Vetulicolia† |state1=dashed
      |2={{Clade
         |label1=[[Ambulacraria]]
         |1={{Clade
            |1=? Vetulicolia† |state1=dashed
            |2={{Clade
               |1=[[Hemichordata]]
               |label2=[[Echinodermata]]
               |sublabel2={{small|([[total group]])}}
               |2={{Clade
                  |label1=
                  |1=? Vetulicolia† |state1=dashed
                  |2=[[Echinodermata]]<br />{{small|([[crown group]])}}
               }}
            }}
         }}
         |label2=[[Chordata]]
         |2={{Clade
            |1=? Vetulicolia† |state1=dashed
            |2={{Clade
               |label1=[[Tunicata]]
               |sublabel1={{small|([[total group]])}}
               |1={{Clade
                  |label1=
                  |1=? Vetulicolia† |state1=dashed
                  |2=[[Tunicata]]<br />{{small|([[crown group]])}}
               }}
               |label2=[[Euchordata]]
               |sublabel2={{small|([[total group]])}}
               |2={{Clade
                  |label1=
                  |1=? Vetulicolia† |state1=dashed
                  |label2=[[Euchordata]]
                  |sublabel2={{small|([[crown group]])}}
                  |2={{Clade
                     |1=[[Cephalochordata]]
                     |2=[[Vertebrata]]
                  }}
               }}
            }}        
         }}
      }}
   }}
}}
|caption=Adapted from cladograms in Aldridge ''et al.'' 2007, showing each possible placement for Vetulicolia considered in the paper;<ref>{{harvnb|Aldridge|Hou|Siveter|Siveter|2007|pages=156, 158}}</ref> note the presence of the [[Euchordata]] clade rather than the now-favored [[Olfactores]].
}}

Vetulicolians were thought to be stem [[arthropods]] when ''[[Vetulicola]]'' was first discovered, but around 2001 the focus of most theories shifted towards stem [[deuterostomes]] due to the discovery of pharyngial gill slits (a deuterostome characteristic), as well as the mounting evidence that vetuicolians have no appendages of any kind.<ref name=TreeOfLife>{{harvnb|Giribet|Edgecombe|2020|page=105}}</ref>  A theory grouping both vetulicolians and [[vetulocystida|vetulocystids]] with ''[[Saccorhytus]]'' was disproven when the alleged pharyngial openings of ''[[Saccorhytus]]'' were shown to be remnants of spines that had broken off; the saccorhytids are now considered to be [[ecdysozoans]].<ref>{{harvnb|Liu|Carlisle|Zhang|Yang|2022}}</ref>

== References ==
{{Reflist}}

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{{refend}}

== External links ==
{{Wikispecies}}
{{Commons category}}
* [https://web.archive.org/web/20070218072622/http://www.geolsoc.org.uk/template.cfm?name=OFNANP New phylum on the block] – Accessed January 3, 2008
* [http://www.nature.com/nature/journal/v414/n6862/extref/414419aa.html Photos and drawings of fossils of various Vetulicolians] – Accessed January 3, 2008

{{Vetulicolia}}
{{Taxonbar|from=Q1261437}}

[[Category:Vetulicolia| ]]
[[Category:Bilaterian phyla]]