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pictorial guide
Dicranopeltis
protaspis
Amphilichas
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ORDER LICHIDA (sensu Fortey 1997)
last revised 07 September 2007 by S. M. Gon III
Introduction: typically spiny with densely granulate or tuberculate
exoskeletons.
Cephalon: opisthoparian
sutures; glabella broad, large, extending to anterior border, unusal
lobation distinguishing a longitudinal lobe and lateral lobes; such
lobation relatively simple (Dameselloidea & Odontopleuroidea) to
complex with fused lateral and glabellar lobes (Lichoidea); eyes
typically present, holochroal, usually not large; conterminant
hypostome; typically with genal spines, sometimes greatly extended.
Thorax: variable, 8-13 segments, usually spine-tipped, sometimes
with distinctive spines (e.g., Odontopleuroidea).
Pygidium: typically isopygous to macropygous, but sometimes
short (e.g., Odontopleuroidea), otherwise often longer than wide, with
3 or more pairs of furrowed pleurae, typically ending in spinose tips.
Other:
similarities in protaspides of Lichidae and Odontopleuridae suggests
common ancestry, but this relationship controversial (see
Classification Notes below).
Occurrence: Middle Cambrian to Devonian (Frasnian)
Superfamilies: Lichoidea, Odontopleuroidea, Dameselloidea.
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Arctinurus
Lichakephalus
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Superfamily Lichoidea
Introduction: medium to large trilobites, typically surface
sculpturing involves two size classes of granules or tubercles.
Cephalon: opisthoparian sutures, glabella broad, extending
to anterior border, with unique complex structure (lateral glabellar and
occipital lobes often fused with each other and with cranidium), hypostome conterminant, large.
Thorax: Typically 11 segments, pleurae initially horizontal, bend
retrograde at fulcrum, end in free points.
Pygidium: large, usually flattened, often with 3 pleural pairs
of leaflike or spinose structures.
Other: wide doublure bearing terraced ridges.
Occurrence: Middle Cambrian to Upper Devonian
Families: Lichakephalidae, Lichidae
Genera:
Lichakephalidae: Acidaspidella?, Acidaspides?, Acidaspidina, Archikainella,
Belovia, Bestjubella, Brutonia, Colossaspis, Eoacidaspis, Lichakephalus,
Lichokephalina, Metaacidaspis, Paraacidaspis, Usoviana.
Lichidae: Acanthopyge (=Euarges), Akantharges, Allolichas,
Amphilichas (/Paralichas; /Platymetopus; = Acrolichas; = Kerakephalichas;
= Tetralichas), Apatolichas, Arctinurus (/Oncholichas; /Platynotus; /Pterolichas),
Autoloxolichas, Borealarges, Ceratarges (/Arges), Ceratolichas, Conolichas
(=Cypholichas), Craspedarges, Dicranogmus, Dicranopeltis (=Dicranopeltoides;
=Nonix; =Raymondarges; /Trachylichas; =Tsunyilichas), Echinolichas, Eifliarges,
Gaspelichas, Hemiarges (=Choneilobarges), Homolichas, Hoplolichas (=Cyranolichas),
Hoplolichoides, Jasperia, Leiolichas, Lichas (=Apolichas; =Autolichas),
Lobopyge (=Belenopyge), Lyralichas, Mephiarges, Metaleiolichas, Metalichas,
Metopolichas (/Metopias; =Holoubkovia; =Macroterolichas), Neolichas, Nipponarges,
Ohleum, Oinochoe, Otarozoum, Paraleiolichas, Perunaspis (=Nitidulopyge),
Platylichas (=Lingucephalichas), Probolichas, Pseudotupolichas (=Arctinuroides),
Radiolichas (=Diplolichas; =Septidenta), Richterarges, Rontrippia, Terataspis,
Terranovia, Trimerolichas, Trochurus (=Corydocephalus; =Plusiarges; =Makromuktis),
Uralichas (=Bohemolichas; =Platopolichas), Uripes.
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Kettneraspis
protaspis
Diacanthaspis
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Superfamily Odontopleuroidea
Introduction: typically very spinose and densely sculptured
trilobites.
Cephalon: convex; glabella tapering forward or subparallel,
extending to anterior margin or nearly so, less complex lobation than in
Lichoidea; eye ridges run from anterior end of glabella to palpebral lobe;
opisthoparian sutures, often placed on sutural ridges; distinct notch in
margin of free cheek adjacent to where anterior sutures cut cephalic margin;
facial sutures secondarily lost in some genera; short genal spines typically
present.
Thorax: 8 – 10 segments; tips of each bear 2 – 3 pairs of spines
(anterior pair often difficult to see, ventrally directed); often with symmetrical
row arrangements of pleural spines or tubercles.
Pygidium: micropygous, short, transverse, with 2 – 3 axial
rings (3rd often faint), one or more pairs of tubular border spines, the
largest of which connected to first axial ring by prominent ridge.
Other: doublure not
wide nor bearing terraced ridges as in Lichoidea; protaspides similar
to, but about half the size of those of Lichida.
Occurrence: Upper Cambrian to Upper Devonian (Frasnian)
Families: Odontopleuridae
Genera: Odontopleuridae: Acanthalomina, Acidaspidella?, Acidaspides?, Acidaspis, Anacaenaspis
(=Bruxaspis), Apianurus, Archaeopleura, Boedaspis, Borkopleura, Brutonaspis,
Calipernurus, Ceratocara, Ceratocephala (=Bounyoungia; =Onchaspis; /Trapelocera),
Ceratocephalinus, Ceratonurus, Chlustinia, Dalaspis, Diacanthaspis, Dicranurus,
Dudleyaspis, Edgecombeaspis, Eoleonaspis (=Bojokoralaspis), Exallaspis,
Gaotania, Globulaspis, Hispaniaspis, Isoprusia (=Mauraspis), Ivanopleura,
Kettneraspis (=Grossia), Koneprusia, Laethoprusia, Leonaspis (=Acanthaloma),
Meadowtownella, Miraspis (=Elbaspis), Ningnanaspis, Odontopleura, Orphanaspis,
Periallaspis, Primaspis, Proceratocephala (=Drummuckaspis), Radiaspis (=Xanionurus;
=Charybdaspis), Rinconaspis, Selenopeltis (=Languedopeltis; =Polyeres), Selenopeltoides,
Sinespinaspis, Stelckaspis, Taemasaspis (=Gondwanaspis; =Snoderaspis), Uriarra,
Whittingtonia.
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Damesella
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Superfamily
Dameselloidea
Introduction: similar to Odontopleuroids, surface finely to
coarsely granulose.
Cephalon: opisthoparian sutures; glabella narrow or broad based,
tapering forward, less complex lobation than in Lichoidea; genal spines
typically present.
Thorax: with up to 13 segments, less specialized than in Odontopleuroidea,
more as in Lichoidea.
Pygidium: longer pygidia than in Odontopleuroidea, with more
axial segments; tapering axis, thicker-set marginal spines, 1-7 pairs of
pleural pygidial spines of varying length
Occurrence: Middle Cambrian to Upper Cambrian(?)
Other: protaspides of Damesellidae and Odontopleuridae similar.
Family: Damesellidae
Genera: Damesellidae: ?Adelogonus, Ariaspis, Bergeronites
(=Spinopanura), Blackwelderia (=Parablackwelderia), Blackwelderioides, Chiawangella,
Cyrtoprora, Damesella (=Hybowania; =Eodamesella), Damesops (=Meringaspis;
=Paradamesops), Dipentaspis, Dipyrgotes, Drepanura, Duamsannella, Fengduia,
Guancenshania, ?Hercantyx, Histiomona, Jiawangaspis, Liuheaspis, Metashantungia,
Neodamesella, Palaeodotes, (=Pseudobergeronites), Paradamesella (=Falkopingia),
Parashantungia, Pingquania (=Oxygonaspis), Pionaspis, Protaitzehoia, Pseudoblackwelderia,
Shantungia, Stephanocare, Taihangshania, Taitzehoia, Teinistion (=Dorypygella),
Xintaia, Yanshanopyge.
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Selenopeltis
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ADDITIONAL CLASSIFICATION NOTES FOR LICHIDA:
Fortey (1997) lists Lichoidea, Odontopleuroidea, and Dameselloidea as
constituent superfamilies of Order Lichida. Some treatments recognize
an Order Odontopleurida separate from Order
Lichida, although protaspid similarities suggest the two are ultimately
related; both lichid and odontopleurid protaspides possess distinctive
paired spine or tubercle patterns on cephalon and protopygidium, have
an anterior border, distinct axis, and marginal spines on protopygidium
(Thomas & Holloway 1988). However, Whittington (1956) points out
that the lichid protaspis is twice the size of those of odontopleurids.
Odontopleurid protaspide hypostomes also lack slits on the lateral
hypostomal border borne by those of lichids (and styginids).
Despite both groups being
ornamented with tubercles and typically spiny, the lobation of the
glabella, complex in both, show some
major differences in origin (lichid lobes arising from the axial
furrow,
while odontopleurid lobes arise via standard glabella development
(Tripp
& Evitt 1981). Whittington (2002) adds that the Odontopleuridae
and
Lichidae differ in several other respects, including ornamentation (primarily
granules
and tubercles in lichids, spines in odontopleurids), extent of ventral
calcification
(extended doublure with terrace ridges in lichids, not developed in
odontopleurids),
and hypostome size (larger in lichids). Even if both lichids and odontopleurids are kept in one
order
(Lichida), it is acknowledged that despite their common origin, they
have
diverged significantly in the course of their evolution.
The primitive
family Lichakephalidae includes genera that have affinities
to Lichidae and others to Odontopleuridae, and some workers (e.g.,
Shergold et al 2000) do not accept the synonymy of Eoacidaspididae and
Lichakephalidae. Examination of Cambrian lichakephalid/eoacidaspidid
genera Acidaspides and Acidaspidella (Bruton
1983) suggest they should be assigned to Odontopleuridae. This
suggests that the Lichakephalidae as listed above is paraphyletic, and
not all members should be included in Lichoidea. If Lichakephalidae is
monophyletic, then it serves as the uniting taxon for an Order Lichida
that includes both lichoids and odontopleuroids; if not, then some
genera should be assigned to Odontopleuridae and others retained in
Lichakephalidae.
Fortey (1990) included
the M-U Cambrian Damselloidea as a sister group to
Odontopleuroidea, citing several characters: 1) narrow, ledglike
anterior cranidial border, against which glabella abuts sharply, 2)
deeply scribed, inflated eye ridges, 3) transverse hypostome with wide
posterior border, 4) spinosity, especially on pygidium and
anterolateral margins of free cheeks, 5) occipital tubercle without
thoracic homologs 6) 3rd glabellar lobe reduced or absent. Presence of Acidaspides praecurrens
and 'odontopleurid protaspides' in Upper Cambrian Kazakhstan
attributable to dameselloids further strengthen this relationship
(Fortey pers com 2007). Primitive Ordovician lichakephalids (e.g.,
Lichakephalus) bear pygidia that are unlike typical lichids,
some being arguably styginid-like, however Whittington (2002) suggests that
a close relationship between lichids and styginids appears unlikely. If so, then sister taxon to the primitive Lichida might
be found in the paraphyletic Redlichiida.
In 2005, Pollit et al applied cladistic analysis to the Superfamily
Lichoidea (Lichidae+Lichakephalidae) and proposed subfamilial and
tribal subdivisions for the family Lichidae. Click here for a cladogram
of Lichoid relationships from the Pollit et al 2005 paper (warning, large graphic file).
Expanded and complete genera listings for the families above adapted from Jell &
Adrain (2003).
For details on Lichida ontogeny, see Dr. Rudy Lerosey-Aubril's page: Larvae & Trilobite Orders: Lichida
Bruton, D. 1983. Cambrian origins of the odontopleurid trilobites. Palaeontology 26(4):875-85.
Fortey, R.A. 1990. Ontogeny, hypostome attachment,
and trilobite classification. Palaeontology 33:529-76.
Fortey, R.A. 1997. Classification. In: Kaesler, R. L., ed. Treatise on Invertebrate Paleontology, Part O, Arthropoda
1, Trilobita, revised. Volume 1: Introduction, Order Agnostida, Order Redlichiida.
xxiv + 530 pp., 309 figs. The Geological Society of America, Inc. & The
University of Kansas. Boulder, Colorado & Lawrence, Kansas.
Jell, P.A. & J.M. Adrain. 2003. Available generic names for trilobites.
Memoirs of the Queensland Museum 48(2):331-553.
Pollit, J.R., R.A. Fortey & M.A Wills.
2005. Systematics of the Trilobite families Lichidae Hawle & Corda,
1847 and Lichakephalidae Tripp, 1957: The application of Bayesian
inference to morphological data. J. Syst. Pal. 3(3):225-41.
Shergold, J.H., R. Feist & D. Vizcaino. 2000. Early Late Cambrian
trilobites of Australo-Sinian aspect from the Montagne Noir, Southern
France. Palaeontology 43(4):599-632.
Thomas A.T. and D.J. Holloway. 1988. Classification
and phylogeny of the trilobite order Lichida. Phil. Trans. Royal Soc. London
321:179-262.
Whittington, H.B. 1956. Beecher's lichid protaspis and Acanthopyge consanguinea (Trilobita). J. Paleontol. 30:1200-04.
Whittington, H.B. 2002. Lichidae (Trilobita): Morphology
and classification. J. Paleontology 76(2):306-20.
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