After Sansom, 2009 (fig. 5), and Scott & Wilson, 2014

Alternative (older) phylogeny after Janvier, 1981, Carroll, 1988, Janvier, 1997 [“The Tree of Life”], Adrian & Wilson, 1994, and Mark-Kurik & Janvier, 1995

<==o Osteostraci Lankester, 1868 [Cephalaspidiformes]
   |--o †Atelaspididae Traquair, 1899 sensu Sansom, 2009
   |  |-- †Hirella gracilis [Micraspis] L. Dev. Eu. [paraphyletic Ateleaspidae]
   |  `--o †Atelaspidinae Traquair, 1899 sensu Sansom, 2009
   |     |-- †Aceraspis robusta [Hemiteleaspis] [paraphyletic Ateleaspidae]
   |     `-- †Atelaspis tessellata [paraphyletic Ateleaspidae]
   `--+-- †Hemicyclaspis murchisoni (Egerton, 1857) L. Dev. Eu. NNA.
      `--o †Cornuta Janvier, 1985b sensu Sansom, 2009
         |--o †Cephalaspis [incl.? Alaspis] [Camptaspis; Escuminaspis; Eucephalaspis; Minestaspis; Pattenaspis; Scolenaspis] U. Sil. L. Dev. Eu. L.-M. Dev. Spits. L. Dev. EAs. L.-U. Dev. NA. [Cephalaspidida Stensiö, 1964]
         |  |-- †C. lyelli Agassiz, 1835
         |  |-- †C. producta Wängsjö, 1952
         |  |-- †C. cradleyensis Stensiö, 1932
         |  |-- †C. sollasi Stensiö, 1932
         |  |?- †C. magnifica Obruchev, 1961
         |  |?- †C. microtuberculata [Alaspis]
         |  `?- †C. powriei
         `--+--o †Zenaspidida Stensiö, 1958 sensu Sansom, 2009
            |  |--o †Spangenhelmaspis Sansom, 2009 [Cephalaspis Agassiz, 1835; Stensiö, 1927 (in partim); Securiaspis Wängsjö, 1952 (in partim); Securiaspis Janvier, 1985b (in partim)]
            |  |  |-- †S. staxrudi (Stensiö, 1927) [Cephalaspis staxrudi Stensiö, 1927]
            |  |  `-- †S. quadrata (Wängsjö, 1952) [Securiaspis quadrata Wängsjö, 1952]
            |  |--o †Parametereoaspididae Sansom, 2009
            |  |  |-- †Parametereoraspis gigas
            |  |  `--+?- †Trewinia (sedis mutabilis)
            |  |     |-- †Balticaspis latvica Lyarskaya, 1981 [incl.? Afanassievaspis Otto & Laurin, 2001]
            |  |     `--+--o †Escuminaspis [synon. of Cephalaspis]
            |  |        |  `-- †E. laticeps (Traquair, 1880) [Cephalaspis rosamundae Roberts, 1937; Alaspis macrotuberculata Ørvik, 1957; †Alaspis rosamundae (juv.)] U.Dev. ENA.
            |  |        `-- †Levesquaspis patteni (Robertson, 1936)
            |  `--+?-o †Wladysagitta Voichyshyn, 2006; L.Dev. WEu. EEu. (sedis mutabilis)
            |     |  |-- †W. janvieri Voichyshyn, 2006
            |     |  `-- †W. acutirostris (Stensiö, 1932) [†Cephalaspis acutirostris (Stensiö, 1932)]
            |     `--o †Zenaspididae Stensiö, 1958 sensu Sansom, 2009
            |        |--o †Superciliaspididae Scott & Wilson, 2014
            |        |  |-- †Glabrapelta minima Scott & Wilson, 2014
            |        |  `--+-- †Dentapelta loefflerae Scott & Wilson, 2014
            |        |     `-- †Superciliaspis gabrielsei (Dineley & Loeffler, 1976) Adrian & Wilson, 1994 [Cephalaspis? gabrielsei Dineley & Loeffler, 1976]
            |        `--+--o †Scolenaspididae
            |           |  |-- †Scolenaspis signata
            |           |  |-- †Ukrainaspis kozlowskii (Zych, 1937) (Sansom, 2009 [Cephalaspis Agassiz, 1835; Zych, 1937 (in partim); Cephalaspis Agassiz, 1835; Janvier, 1985b, 1985e (in partim); Heraspis Afanessieva, 1991, 2004 (preoccupied) non Megistaspis (Heraspis) Wandås, 1983, a trilobite subgenus]
            |           |  `--o †Machairaspis
            |           |     |-- †M. ibex Wängsjö, 1952
            |           |     `-- †M. corystis Wängsjö, 1952
            |           `--o †Zenaspididae Stensiö, 1958 sensu Scott & Wilson, 2014
            |              |--o †Tegaspis L.Dev. Spits.
            |              |  |-- †T. kolleri (Stensiö, 1927)
            |              |  `-- †T. pedata (Wängsjö, 1952)
            |              `--+--o †Stensiopelta denison, 1951a; L.Dev. Eu.
            |                 |  |-- †S. woodwardi (Stensiö, 1932) [Cephalaspis woodwardi Stensiö, 1932]
            |                 |  `-- †S. pustulata Janvier, 1985b
            |                 `--+?- †“Diademaspis”? mackenziensis Adrian & Wilson, 1994
            |                    |--o †Diademaspis Janvier, 1985b
            |                    |  |-- †D. poplinae Janvier, 1985b
            |                    |  |-- †D. jarviki (Wängsjö, 1952) Janvier, 1985b [Cephalaspis jarviki Wängsjö, 1952]
            |                    |  `-- †D. stensioei Afanassieva, 1989
            |                    `--o †Zenaspis Lankester, 1870 sensu Janvier, 1985b; L.Dev. NWEu. EEu. Spits.
            |                       |-- †Z. salweyi (Egerton, 1857) [†Cephalaspis salweyi Egerton, 1867]
            |                       |?- †Z. metopias (Wängsjö, 1952)
            |                       |-- †Z. podolica (Balabai, 1962)
            |                       `-- †Z. dzieduszyckii Voichyshyn, 2006
            `--+--+?-+--o †Zychaspis Janvier, 1985; U.Sil. WEu., U.Dev. EEu.
               |  |  |  |-- †Z. granulata Voichyshyn, 1998
               |  |  |  `-- †Z. siemiradzkii
               |  |  |--o †Pattenaspis [Cephalaspis (in partem)]
               |  |  |  |-- †P. acuminata
               |  |  |  |-- †P. deltoides
               |  |  |  |-- †P. eurhynchus (Wängsjö, 1952)
               |  |  |  `-- †P. rogalai (Balabai, 1962)
               |  |  `--+-- †Hildenaspis digitalis Janvier, 1976; E.Dev. CEu.
               |  |     `-- †Mimetaspis hoeli Stensiö, 1958
               |  `--+--+--o †Waengsjoeaspis Janvier, 1985b 
               |     |  |  |-- †W. excellens (Wängsjö , 1952) Janvier, 1985b [†Cephalaspis excellens Wängsjö , 1952]
               |     |  |  |-- †W. vogti (Stensiö, 1927) Janvier, 1985b [†Cephalaspis vogti Stensiö, 1927]
               |     |  |  `-- †W. nahanniensis Adrian & Wilson, 1994
               |     |  `--+-- †Camptaspis utahensis Branson & Mehl, 1931
               |     |     `--o †Yvonaspis Belles-Isles, 1989 [Cephalaspis (in partem)]
               |     |        |-- †Y. dawsoni (Lankester 1870)
               |     |        |-- †Y. jexi (Traquair 1893)
               |     |        |-- †Y. lunata (Pageau 1969)
               |     |        |-- †Y. peninsula (Pageau 1969)
               |     |        |-- †Y. syndenhami (Pageau 1969)
               |     |        `-- †Y. westolli (Russell 1954)
               |     `--o †Benneviaspidida Denison, 1951a (non Halstead Tarlo, 1967) sensu Sansom, 2009
               |        |-- †Ectinaspis Wängsjö, 1952 [Hoelaspis] L.Dev. Spits.
               |        `--+--o †Securiaspis Stensiö, 1932; L.Dev. Eu. Spits.
               |           |  |-- †S. kitchini Stensiö, 1932
               |           |  `-- †S. kingi Stensiö, 1932
               |           `--+-- †“Benneviaspis” longicornis
               |              `--+--o †Benneviaspis Stensiö, 1927 [incl. Citharaspis Afanassieva, 1989] L. Dev. Eu. Spits. [Benneviaspididae Denison, 1951]
               |                 |  |-- †B. anglica Stensiö
               |                 |  `--+-- †B. lankesteri Stensiö
               |                 |     `--+-- †B. urvantsevi Mark-Kurik & Janvier, 1995; L. Dev. NAs.
               |                 |        |-- †B. maxima
               |                 |        |-- †B. holtedahli
               |                 |        |-- †B. polonica Belles-Isles & Janvier, 1984
               |                 |        |-- †B. whitei Belles-Isles & Janvier, 1984
               |                 |        `-- †B. junia (Afanassieva, 1989) [Citharaspis junia Afanassieva, 1989]
               |                 `--o †Boreaspidoidei Stensiö, 1958 sensu Sansom, 2009
               |                    |-- †Hoelaspis angulata Stensiö, 1927
               |                    |-- †Severaspis rostralis Mark-Kurik & Janvier, 1995; L. Dev. NAs.
               |                    `--o †Boreaspididae Stensiö, 1958
               |                       |-- †“Boreaspisceratops
               |                       |-- †“Boreaspisintermedia
               |                       |--o †Boreaspis Stensiö, 1927 sensu stricto?; U.Dev. Spits.
               |                       |  |-- †B. puella
               |                       |  `== 12 other species?
               |                       |-- †Dicranaspis Janvier, 1985 [non Dicranaspis Mabille, 1878 (Insecta: Lepidoptera: Hesperiidae)]
               |                       `--+--o †Spatulaspis Janvier, 1985
               |                          |  |-- †S. costata (Wängsjö, 1952)
               |                          |  `-- †S. robusta (Wängsjö, 1952)
               |                          `--+-- †Belonaspis datura Haeckel, 1881
               |                             `--+-- †Hapilaspis aphales Mark-Kurik & Janvier, 1995; L. Dev. NAs.
               |                                `-- †Tauraspis rara Mark-Kurik & Janvier, 1995; L. Dev. NAs.
               `--o †Thyestiida Berg, 1940 sensu Sansom, 2009 [incl. Kiaeraspidida Stensiö, 1932; Tannuaspidida]
                  |-- †Ilemoraspis kirkinskayaeObruchev, 1961; L.Dev. WSib.
                  `--+-- †Procephalaspis oeselensis (Robertson, 1939) Denison, 1951 [Cephalaspis oeselensis Robertson, 1939] U.Sil. Eu.
                     `--+-- †Auchenaspis salteri Egerton, 1857; U.Sil. Eu.
                        `--+-- †Thyestes verrucosus [Auchenaspis] U.Sil.-L.Dev. Eu. [Thyestidae??]
                           `--+-- †Witaaspis patteni U. Sil. EEu.
                              `--+--o †Kiaeraspidoidea (Stensiö, 1932) Afanassieva, 1991
                                 |  |-- †Didymaspis grindrodi  Lankester, ?1867
                                 |  `--o †Kiaeraspididae Stensiö, 1932
                                 |     |-- †Kieraspis L.Dev. Spits.
                                 |     `--+?- †Norselaspis glacialis Janvier, 1981 (sedis mutabilis)
                                 |        `--o †Axinaspidoidea Janvier, 1981a
                                 |           |-- †Nectaspis Wängsjö, 1952; L.-M.Dev. Spits.
                                 |           `--+-- †Axinaspis Wängsjö, 1952; L.Dev. Spits.
                                 |              `--o †Acrotomaspidinae Janvier, 1981a
                                 |                 |-- †Acrotomaspis Wängsjö, 1952; L.Dev. Spits.
                                 |                 `-- †Gustavaspis trinodis (Wängsjö 1952) Janvier, 1981
                                 `--o †Tremataspidoidea (Woodward, 1891) Afanassieva, 1991 sensu Sansom, 2009
                                    |--o †Tyriaspis U.Sil. Eu.
                                    |  `-- †T. whitei
                                    |-- †Saaremaaspis [Dasylepis; ?Dictyolepis; Rotsikuellaspis obrutchevi Robertson, 1938] U. Sil. L. Dev. Eu.
                                    `--o †Tremataspididae Woodward, 1891
                                       |-- †Aestiaspis
                                       |--o †Dartmuthia [Lophosteus] U.Sil. Eu. [Dartmuthiidae]
                                       |  `-- †D. gemmifera
                                       `--+-- †Timanaspis U. Sil. EEu. L. Dev. Eu.
                                          `--+--o Tremataspidinae Woodward, 1891
                                             |  |-- †Oeselaspis [?Trachylepis] U.Sil. Eu.
                                             |  `-- †Tremataspis [Odontododus, Stigmolepis] U. Sil. Eu.
                                             `--+-- †Dobraspis
                                                `--+-- †Tannuaspis levenkoi Obruchev, 1956 [incl. Tuvaspis margaritae Obruchev, 1956] L. Dev. NAs. 
                                                   `-- †Sclerodus [Eukeraspis] L. Dev. Eu. [Sclerodontidae]

†Osteostraci incertae sedis:

Tuvaspis L. Dev. NAs. [paraphyletic Ateleaspidae]
    †Hemiteleaspis heintzii Westoll, 1945 [=? Hemicyclaspis]
    †Turinea [Cephalopterus] L.Dev. Eu.

After Sansom, 2009 (fig. 5), and Scott & Wilson, 2014

<==o Osteostraci
   |--o †Atelaspididae
   |  |-- †Hirella
   |  `--o †Atelaspidinae
   |     |-- †Aceraspis
   |     `-- †Atelaspis
   `--+-- †Hemicyclaspis
      `--o †Cornuta
         |--o †Cephalaspidida
         |  `-- Cephalaspis
         `--+--o †Zenaspidida
            |  |?- †Wladysagitta
            |  |-- †Spangenhelmaspis
            |  |--o †Parametereoaspididae
            |  |  |-- †Parametereoraspis
            |  |  `--+?- †Trewinia (sedis mutabilis)
            |  |     |-- †Balticaspis
            |  |     `--+-- †Escuminaspis
            |  |        `-- †Levesquaspis
            |  `--o †Zenaspididae
            |     |--+-- †Scolenaspis
            |     |  |-- †Ukrainaspis
            |     |  `--+-- †Machairaspis
            |     |     `-- †Superciliaspis
            |     `--+-- †Tegaspis
            |        `--+-- †Stensiopelta
            |           `--+?- †“Diademaspis”? mackenziensis
            |              |-- †Diademaspis
            |              `-- †Zenaspis
            `--+--+?-+-- †Zychaspis
               |  |  |-- †Pattenaspis
               |  |  `--+-- †Hildenaspis
               |  |     `-- †Mimetaspis
               |  `--+--+-- †Waengsjoeaspis
               |     |  `--+-- †Camptaspis
               |     |     `-- †Yvonaspis
               |     `--o †Benneviaspidida
               |        |-- †Ectinaspis
               |        `--+-- †Securiaspis
               |           `--+-- †“Benneviaspis” longicornis
               |              `--+--o †Benneviaspididae
               |                 |  `-- †Benneviaspis
               |                 `--o †Boreaspidoidei
               |                    |-- †Hoelaspis
               |                    |-- †Severaspis
               |                    `--o †Boreaspididae
               |                       |-- †“Boreaspisceratops
               |                       |-- †“Boreaspisintermedia
               |                       |-- †Boreaspis
               |                       |-- †Dicranaspis
               |                       `--+-- †Spatulaspis
               |                          `--+-- †Belonaspis
               |                             `--+-- †Hapilaspis
               |                                `-- †Tauraspis
               `--o †Thyestiida
                  |-- †Ilemoraspis
                  `--+-- †Procephalaspis
                     `--+-- †Auchenaspis
                        `--+-- †Thyestes
                           `--+-- †Witaaspis
                              `--+--o †Kiaeraspidoidea
                                 |  |-- †Didymaspis
                                 |  `--o †Kiaeraspididae
                                 |     |-- †Kieraspis
                                 |     `--+?- †Norselaspis
                                 |        `--o †Axinaspidoidea
                                 |           |-- †Nectaspis
                                 |           `--+-- †Axinaspis
                                 |              `--o †Acrotomaspidinae
                                 |                 |-- †Acrotomaspis
                                 |                 `-- †Gustavaspis
                                 `--o †Tremataspidoidea
                                    |-- †Tyriaspis
                                    |-- †Saaremaaspis
                                    `--o †Tremataspididae
                                       |-- †Aestiaspis
                                       |--o †Dartmuthiidae
                                       |  `-- †Dartmuthia
                                       `--+-- †Timanaspis
                                          `--+--o Tremataspidinae
                                             |  |-- †Oeselaspis
                                             |  `-- †Tremataspis
                                             `--+-- †Dobraspis
                                                `--+-- †Tannuaspis
                                                   `--o †Sclerodontidae
                                                      `-- Sclerodus

After Janvier, 1981, Carroll, 1988, Janvier, 1997 [“The Tree of Life”], Adrian & Wilson, 1994, and Mark-Kurik & Janvier, 1995

<==o Osteostraci Lankester, 1868 [Cephalaspidiformes]
   |?- †Atelaspis tessellata [paraphyletic Ateleaspidae]
   |-- †Aceraspis robusta [Hemiteleaspis] [paraphyletic Ateleaspidae]
   |-- †Tuvaspis L. Dev. NAs. [paraphyletic Ateleaspidae]
   `--+-- †Hirella gracilis [Micraspis] L. Dev. Eu. [paraphyletic Ateleaspidae]
      |?- †Hemiteleaspis heintzii
      `--+-- †Hemicyclaspis murchisoni (Egerton, 1857) L. Dev. Eu. NNA. [paraphyletic Ateleaspidae]
         |?- †Tannuaspis L. Dev. NAs. [Tannuaspidida]
         `--o †Cornuta Janvier, 1985b [Cephalaspididae sensu lato??]
            |--o †Cephalaspidida Stensiö, 1964
            |  |--o †Cephalaspis [incl.? Alaspis; Camptaspis; Escuminaspis; Eucephalaspis; Minestaspis; Pattenaspis; Scolenaspis] U. Sil. L. Dev. Eu. L.-M. Dev. Spits. L. Dev. EAs. L.-U. Dev. NA.
            |  |  |-- †C. lyelli?
            |  |  |-- †C. magnifica Obruchev, 1961
            |  |  |-- †C. microtuberculata [Alaspis]
            |  |  `-- †C. powriei
            |  |-- †Hildenaspis
            |  |-- †Mimetaspis
            |  |-- †Parameteoraspis
            |  `--o †Pattenaspis [synon. of Cephalaspis?]
            |     |-- †P. deltoides
            |     |-- †P. eurhynchus (Wängsjö, 1952)
            |     `-- †P. rogalai (Balabai, 1962)
            `--+--o †Zenaspidida (Stensiö, 1958) Janvier, 1985b? [Zenaspididae Stensiö, 1958]
               |  |?-o †Stensiopelta Janvier, 1985b; L.Dev. Eu.
               |  |  `-- †S. pustulata Janvier, 1985b
               |  |?-o †Zychaspis Janvier, 1985; U.Sil. WEu., U.Dev. EEu.
               |  |  |-- †Z. granulata Voichyshyn, 1998
               |  |  `-- †Z. siemiradzkii
               |  |-- †Machairaspis
               |  |-- †Scolenaspis
               |  |?- †“Diademaspis”? mackenziensis Adrian & Wilson, 1994
               |  |--o †Tegaspis L.Dev. Spits.
               |  |  |-- †T. kolleri (Stensiö, 1927)
               |  |  `-- †T. pedata (Wängsjö, 1952)
               |  |--o †Diademaspis Janvier, 1985b
               |  |  |-- †D. poplinae Janvier, 1985b
               |  |  |-- †D. jarviki (Wängshö, 1952) Janvier, 1985b [Cephalaspis jarviki Wängsjö, 1952]
               |  |  `-- †D. stensioei Afanassieva, 1989
               |  `--o †Zenaspis Lankester, 1870 sensu Janvier, 1985b; L.Dev. NWEu. EEu. Spits.
               |     |-- †Z. salweyi (Egerton, 1857) [†Cephalaspis salweyi Egerton, 1867]
               |     |?- †Z. metopias (Wängsjö, 1952)
               |     |-- †Z. podolica (Balabai, 1962)
               |     `-- †Z. dzieduszyckii Voichyshyn, 2006
               `--+--o †Benneviaspidida Denison, 1951a (non Halstead Tarlo, 1967) sensu Janvier, 1985b, and Mark-Kurik & Janvier, 1995
                  |  |-- †“Benneviaspis” lankesteri Stensiö
                  |  `--+-- †“Benneviaspis” anglica Stensiö
                  |     |-- †Tauraspis rara Mark-Kurik & Janvier, 1995; L. Dev. NAs.
                  |     `--+-- †Hapilaspis aphales Mark-Kurik & Janvier, 1995; L. Dev. NAs.
                  |        |--o †Benneviaspididae Denison, 1951
                  |        |  `--o †Benneviaspis Stebsiö, 1927 [Citharaspis] L. Dev. Eu. Spits.
                  |        |     |-- †B. urvantsevi Mark-Kurik & Janvier, 1995; L. Dev. NAs.
                  |        |     |-- †B. maxima
                  |        |     |-- †B. holtedahli
                  |        |     |-- †B. polonica
                  |        |     |-- †B. whitei Belles-Isles & Janvier, 1984
                  |        |     `-- †B. (Citharaspis) junia
                  |        `--+-- †“Benneviaspis” longicornis
                  |           `--+-- †Hoelaspis angulata Stensiö, 1927
                  |              `--+-- †Severaspis rostralis Mark-Kurik & Janvier, 1995; L. Dev. NAs.
                  |                 `--o †Boreaspididae Stensiö, 1958
                  |                    |?- †Belonaspis
                  |                    |?- †Dicranaspis
                  |                    |?- †Spatulaspis
                  |                    |-- †“Boreaspis” ceratops
                  |                    `--o †Boreaspis Stensiö, 1927 sensu stricto?; U.Dev. Spits.
                  |                       |-- †B. puella
                  |                       `== 12 other species?
                  `--+--o †Kiaeraspidida Stensiö, 1932
                     |  |-- †Kieraspis L.Dev. Spits. [Kiaeraspididae]
                     |  |-- †Norselaspis glacialis Janvier, 1981
                     |  `--o †Axinaspidoidea Janvier, 1981a
                     |     |-- †Axinaspis L.Dev. Spits.
                     |     |-- †Nectaspis L.-M.Dev. Spits.
                     |     `--o †Acrotomaspididae
                     |        |-- †Acrotomaspis L.Dev. Spits.
                     |        `-- †Gustavaspis
                     `--o †Thyestiida Berg, 1940
                        |-- †Auchenaspis U.Sil. Eu.
                        |-- †Procephalaspis U.Sil. Eu.
                        `--+-- †Witaaspis U. Sil. EEu.
                           |--o †Thyestidae??
                           |  `--o †Thyestes [Auchenaspis] U.Sil.-L.Dev. Eu.
                           |     `-- †T. verrucosus
                           `--o †Tremataspididae Woodward, 1891 sensu Janvier, 1981, 1985, 1996
                              |?- †Timanaspis U. Sil. EEu. L. Dev. Eu.
                              |?-o †Dartmuthiidae
                              |  |--o †Dartmuthia [Lophosteus] U.Sil. Eu.
                              |  |  `-- †D. gemmifera
                              |  |-- †Saaremaaspis [Dasylepis, ?Dictyolepis, Rotsikuellaspis] U. Sil. L. Dev. Eu. 
                              |  `--o †Tyriaspis U.Sil. Eu.
                              |     `-- †T. whitei
                              |?-o †Sclerodontidae
                              |  `-- †Sclerodus [Eukeraspis] L. Dev. Eu.
                              `--o †Tremataspididae Woodward, 1891 [Tremataspidinae]
                                 |-- †Oeselaspis [?Trachylepis] U.Sil. Eu.
                                 `-- †Tremataspis [Odontododus, Stigmolepis] U. Sil. Eu.

Reference(s):