ERA GEOLÓGICA ORDOVICICO

ORDOVICICO - ORDEN LICHIDA .-

Dicranopeltis  protaspis Amphilichas	ORDER LICHIDA (sensu Fortey 1997)last revised 07 September 2011 by S. M. Gon III Introduction: typically spiny with densely granulate or tuberculate exoskeletons. This is a concept of the order that includes the Odontopleuridae and Damesellidae, more recently considered members of a related, but distinct orderOdontopleurida. Examine an alternate handling of Order Lichida that does not include the odontopleurids or damsellids. 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.
Arctinurus  Lichakephalus	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.
Kettneraspis  protaspis Diacanthaspis	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.
Damesella	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.
Selenopeltis	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.