Trilobita

The Ordovician Amphilichas halli. Photo via here.

Belongs within: Trilobitomorpha.
Contains: Proetida, Olenellus, Redlichiina, Trinucleidae, Ptychopariida.

Among the best known of all fossil arthropods, trilobites were found from the Cambrian to the Late Permian, though their greatest diversity was during the Cambrian and Ordovician (Prothero 1998). Trilobites are the earliest dominant marine arthropod group in the fossil record. An earlier classification divided the trilobites between the Miomera (with few abdominal segments, containing the Agnostida) and the Polymera (with numerous abdominal segments, containing the remaining trilobites), but this division is no longer popular as some 'polymerous' trilobites are known to show a reduction in segment number (Fortey 2001). There has also been some debate as to whether the Agnostida are correctly placed among the trilobites or whether they should be regarded as an independent arthropod lineage. Instead, the previously recognised early trilobite order Redlichiida (including the Olenellina and Redlichiina) is probably paraphyletic with regard to the remaining trilobite orders. Plesiomorphic characters of 'redlichiidans' include a large number of thoracic segments, often terminating in divergent spines, and a relatively small pygidium. The Olenellina are elongate, relatively flat trilobites known from the Lower Cambrian, often bearing prominent terminal spines on the cephalon.

The majority of more derived trilobite groups had a much larger pygidium, and terminal spines on the thoracic segments were much smaller or undeveloped. The Ordovician to Devonian Odontopleurida, however, had extremely long spines on the cephalon, thorax and pygidium, some of which could be longer than the central body. The Ordovician to Devonian Lichida had a particularly large pygidium, often larger than the cephalon and made up of three pairs of expanded, spiny pleurae (Prothero 1998).

Characters (from Fortey 2001 and Prothero 1998): Calcified exoskeleton with clear division into cephalon, thorax and pygidium. Compound eyes with calcite lenses; facial suture along cheek between eye and central glabella; hypostomal wings connected to anterior pits in the axial furrow. Three (possibly four) pairs of cephalic limbs plus filamentous antennae. Biramous legs with branched exites (probably functioning as gills). Fused pygidium with more than one segment.

Trilobita [Polymera, Redlichiida, Trilobitacea]
    |--Olenellina F01
    |    |--Olenellus P79
    |    |--Nevadella P79
    |    |--Bristolia P79
    |    |--Fallotaspis P79
    |    |--Daguinaspis P79
    |    `--Holmia kjerulfi P79
    `--+--Redlichiina F01
       `--+--Trinucleidae P98
          |--Ptychopariida F01
          |--Odontopleurida F01
          |    |--Dicranurus P98
          |    |    |--D. hamatus P98
          |    |    `--D. longispinus (Mitchell 1888) [=Acidaspis longispinis, Ceratocephala longispina] F71
          |    `--Odontopleura F71
          |         |--O. bowningensis Etheridge & Mitchell 1896 F71
          |         |--O. hartleii Mitchell 1919 F71
          |         |--O. jenkinsi Etheridge & Mitchell 1896 F71
          |         |--O. parvissima Etheridge & Mitchell 1896 F71
          |         `--O. rattei Etheridge & Mitchell 1896 F71
          |--Lichida F01
          |    |--Amphilichas halli P98
          |    `--Lichas H04
          |         |--L. hirsutus Fletcher 1850 R87
          |         `--L. palmata H04
          `--Harpes [Harpida, Harpina] P98
               |--H. macrocephalus N79
               |--H. trinucleoides Etheridge & Mitchell 1917 F71
               `--H. ungula H04

Trilobita incertae sedis:
  Cyrtosymbole LMW01
  Encrinurus EB01
    |--E. borenorensis Fletcher 1950 F71
    |--E. bowningensis F71
    |--E. duntroonensis Etheridge & Mitchell 1915 [=Cryptonymys (Encrinurus) duntroonensis] F71
    |--E. etheridgei Mitchell 1915 F71
    |--E. frontalis Mitchell 1924 F71
    |--E. mitchelli F71
    |--E. punctatus M87
    |--E. rothwellae Etheridge & Mitchell 1915 F71
    `--E. silverdalensis Etheridge & Mitchell 1915 F71
  Liocalymene EB01
  Xystridura Whitehouse 1936 K02
    `--X. browni (Etheridge 1896) [=Olenellus browni] F71
  Tonkinella HLC03
  Kootenia HLC03
  Megagraulos HLC03
    |--M. breviscapus Kobayashi 1962 S80
    `--M. medius Kobayashi 1962 S80
  Metagraulos HLC03
  Fenghuangella Yang 1978 HLC03
  Torifera Wolfart 1974 HLC03
  Goniagnostus A38
    |--G. confluens [=Agnostus nathorsti confluens] A38
    `--G. nathorsti [=Agnostus nathorsti] A38
  Triplagnostus lomondensis A38
  Xenostegium GO50
  Amorphella Rosova 1963 S80
    `--A. modesta Rosova 1963 S80
  Changshanocephalus S80
  Lioparia S80
  Irvingella S80
    |--I. taitzuhoensis S80
    `--I. tropica S80
  Erixanium sentum S80, P79
  Kaolishania S80
    |--K. australis Shergold 1972 S80
    `--K. pustulosa S80
  Tingocephalus S80
  Pseudosolenopleura kotoi S80
  Pseudoliostracina monkei S80
  Maduiya Rosova 1963 [incl. Maspakites Lazarenko 1968] S80
  Kaninia Walcott & Resser 1924 S80
  Pedinocephalus Ivshin 1956 S80
    `--‘Maladioidella’ convexolimbata Endo in Endo & Resser 1937 S80
  Taenoria expansa Palmer 1960 S80
  Kainellidae S80
    |--Kainella meridionalis SV03
    `--Richardsonella S80
         |--R. arctostriata (Raymond 1937) S80
         |--R. elongata Rasetti 1944 S80
         |--R. eurekensis Kobayashi 1935 S80
         `--R. megalops (Billings 1860) S80
  Parabolina S80
    |--P. acanthura (Angelin 1854) S80
    |--P. brevispina Westergaard 1922 S80
    `--P. spinulosa P79
  Simulolenus Palmer 1965 S80
    `--S. quadrisulcatus Palmer 1965 S80
  Parabolinites Henningsmoen 1957 S80
    `--‘Parabolinella’ laticauda Westergaard 1922 S80
  Protopeltura S80
    |--P. intermedia Westergaard 1922 S80
    `--P. praecursor P79
  Bienvillia corax S80
  Crucicephalus ocellatus Shergold 1972 S80
  Amzasskiella mirabilis Petrunina 1960 S80
  Koptura S80
    |--K. biloba Kobayashi 1935 S80
    `--K. quadrata S80
  Temnura granulosa Kobayashi 1935 [=Temnoura granosa (l. c.)] S80
  Acanthopyge (Mephiarges) TC71
    |--A. (M.) bifida TC71
    |--A. (M.) consanguinea TC71
    `--A. (M.) mephisto TC71
  Gravicalymene australis (Etheridge & Mitchell 1917) [=Calymene australis] F71
  Kiskinella cristata Romanenko & Romanenko 1962 F05
  Agraulos affinis Billings 1872 F05
  Bailiaspis inflata Lake 1940 F05
  Condylopyge F05
    |--C. carinata Westergård 1936 F05
    `--C. rex (Barrande 1846) SS84
  Staurocephalus RZJ04
    |--S. clavifrons Angelin 1854 RZJ04
    `--S. murchisoni F71
  Homalonotus Koenig 1825 C92
  Proetida F01
  Alacephalus Repina 1960 PVP85
    `--A. latus Romenenko 1978 PVP85
  Erbiopsis Lermontova 1940 PVP85
    `--E. coangustus Romanenko 1969 PVP85
  Dionide R27
    |--D. atra R27
    |--D. contrita R27
    |--D. euglypta R27
    |--D. formosa R27
    |--D. hectori Reed 1927 R27
    |--D. holdoni R27
    |--D. hybrida R27
    |--D. lapworthi R27
    `--D. richardsoni R27
  Kleptothule Budd 1995 CB04
  ‘Plutonia’ Hincks 1871 non Morelet 1864 BR05
  Paramansuyella puteata DJ71
  Maladiodella splendens DJ71
  Neoparabolina frequens VEE04
    |--N. f. frequens VEE04
    `--N. f. argentina VEE04
  Prouktaspis luta SB09
  Elicicola calva Jell 1990 SB09
  Abadiella Hupé 1953 L95
    `--A. huoi SB09
  Dolichometopus T10
    |--D. howelli T10
    `--D. tatei T10
  Conocephalites T10
    |--C. australis T10
    `--C. sulzeri R87
  Ceratocephala F71
    |--C. impedita Etheridge & Mitchell 1896 F71
    |--C. phalaenocephala Mitchell 1919 F71
    `--C. vogdesi Etheridge & Mitchell 1896 F71
  Adastocephalum teleotypicum Mitchell 1919 F71
  Amphion brevispinus Etheridge 1895-1896 F71
  Australosutura gardneri (Mitchell 1922) [=Cordania gardneri] F71
  Bounyongia bowningensis Etheridge & Mitchell 1917 F71
  Bronteus F71
    |--B. angusticaudatus Etheridge & Mitchell 1917 F71
    |--B. bowningensis Etheridge & Mitchell 1917 F71
    |--B. jenkinsi Etheridge & Mitchell 1890 F71
    |--B. longispinifex Mitchell 1887 F71
    |--B. mesembrinus Etheridge & Mitchell 1917 F71
    |--B. molongensis Etheridge & Mitchell 1917 F71
    |--B. partschi M87
    |--B. platynotus Mitchell 1924 F71
    `--B. (Goldius) singularis Mitchell 1924 F71
  Corydocephalus palmata [incl. Lichas sinuata Ratte 1886, C. palmata var. sinuata] F71
  Cromus F71
    |--C. beaumonti M87
    `--C. murchisoni F71
  Cryptonymus F71
    |--C. angustus Mitchell 1924 F71
    |--C. incertus Mitchell 1924 F71
    |--C. perannulatus Mitchell 1924 F71
    |--C. platynotus Mitchell 1924 F71
    `--C. robustus Mitchell 1924 F71
  Cyphaspis F71
    |--C. bowningensis Mitchell 1887 F71
    |--C. filmeri Mitchell 1919 F71
    |--C. horani Etheridge & Mitchell 1893 F71
    |--C. rotunda Etheridge & Mitchell 1893 F71
    `--C. yassensis Etheridge & Mitchell 1893 F71
  Odontochile F71
    |--O. loomesi (Mitchell 1919) [=Dalmanites (Hausmannia) loomesi] F71
    `--O. meridianus (Etheridge & Mitchell 1895) [=Hausmannia meridianus, Dalmanites meridianus] F71
  Dicranogmus bartonensis Fletcher 1950 F71
  Lyriaspis alroiensis (Etheridge 1919) [=Ptychoparia alroiensis; incl. P. merrotskii] F71
  Pagetia significans (Etheridge 1902) [=Microdiscus significans] F71
  Phillipsia F71
    |--P. breviceps Mitchell 1918 F71
    |--P. collinsi Mitchell 1918 F71
    |--P. coulteri Mitchell 1918 F71
    |--P. dungogensis Mitchell 1918 F71
    |--P. elongata [incl. P. dubia Etheridge 1902] F71
    |--P. grandis Etheridge 1892 [incl. P. robusta Mitchell 1918] F71
    |--P. proxima Mitchell 1918 F71
    `--P. rouchelensis Mitchell 1918 F71
  Leckwyckia Termier & Termier 1951 H75
    `--*L. enigmatica Termier & Termier 1951 H75
  Corbinia apopsis J79
  Presbynileus ibexensis J79
  Trigonocerca typica J79
  Protopliomerella contracta J79
  Hintzeia celsaora J79
  Comura defensor H79
  Acastoides henni H79
    |--A. h. henni H79
    `--A. h. posthumus H79
  Pholonyx philonyx H79
  Schizoproetus onyx H79
  Longiproetus cultrijugati H79
  Lacunoporaspis norris N79
  Ricticuloharpes reticulatus N79
  Platyscutellum brevicaulis N79
  Cornuproetus tozeri N79
  Astycorphe cimelia N79
  Leonaspis elliptica N79
  Otarion belanops N79
  Dechenella N79
    |--D. mclareni N79
    `--D. tesca N79
  Deltadechenella bathurstensis N79
  Ancyropyge manitobensis N79
  Lepidoderma Reuss 1855 B78
  Acanthomicmacca walcotti L95
  Callavia broeggeri L95
  Strenuella strenua L95
  Dalmania punctata H04
  Ampyx FO99
    |--A. linleyoides FO99
    |--A. nasutus FO99
    `--A. rouaulti H04
  Acidaspis FO99
    |--A. dufresnoyi H04
    |--A. jessi FO99
    |--A. prevosti R87
    |--A. verneuili R87
    `--A. vesiculosa R87
  Hydrocephalus saturnoides H04
  Dicellocephalus Owen 1852 W77
    |--D. cora W77
    |--D. flagricaudus White 1874 W77
    `--D. magnificus W77
  Delgadella Walcot 1912 M65
    `--*D. lusitanica (Delgado 1904) [=Lingulepis lusitanica] M65
  Hypodicranotus striatulus FO99
  Paranorwoodia venusta FO99
  Carolinites [Telephinidae] FO99
    `--C. genacinaca FO99
  Dindymene saron FO99
  Ormathops nicholsoni FO99
  Colpocoryphe [Colpocoryphinae] FO99
    `--C. taylorum FO99
  Illaenopsis harrisoni FO99
  Bergamia rushtoni FO99
  Hemiarges bigener E84
  Bynumina vescula LM05
  Eutychaspis kirkii LM05
  Rasettia wachitaensis LM05
  Bayfieldia simata LM05
  Eurekia LM05
    |--E. apopsis LM05
    `--E. eos LM05
  Apatakephaloides clivosus LM05
  Lantugula leonensis LM05
  Apoplanius rejectus LM05
  Highgatella cordilleri LM05
  Hystricurus millardensis LM05
  Ogygia buchi R87
  Arionellus ceticephalus R87
  Tomagnostella Kobayashi 1939 TS11

*Type species of generic name indicated

REFERENCES

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