Lichidae

Classification
Phylum: Arthropoda
Class: Trilobita
Order: Lichida
Family: Lichidae (Hawle & Corda, 1847)
Cincinnatian Genus: Amphilichas

Geologic Range
Early Ordovician – Late Devonian

Common Paleoecology
Lichidae is a family of extinct fast-moving low-level epifaunal carnivores

Description of the Family

  • Moderately convex cranidium but can range from flattened to extremely convex
  • Broad and subrectangular Glabella
  • Median lobe expanded toward the anterior end
  • Pre-glabellar field absent
  • Axial furrows tend to die out or to be diverted posteriorly

Published Descriptions

Treatise on Invertebrate Paleontology, Part O (1959):

  • Cranidium usually moderately convex, but ranging from flattened to extremely convex; glabella broad and subrectangular; median lobe expanded anteriorly, basal area tending to become depressed; foremost pair of lateral glabellar furrows extended backward to form longitudinal furrows, which may reach occipital furrow; middle lateral furrows obsolete or represented by notches on longitudinal furrows; basal lateral furrows may be complete (bicomposit lobes then usually circumscribed), or incomplete (bicomposite lobes then partially defined), or lacking (lateral lobes then tricomposite); axial furrows tend to die out or to be diverted posteriorly; circumscribed occipital lobes present (Lichas and other genera) but commonly fused with posterior lateral glabellar lobes; occipital ring broad; glabellar lobes vary greatly in definition and inflation in some genera becoming bulbous; pre-glabellar field absent; anterior border may be ill-defined or strongly developed and projecting at an angle; fixigenae subtriangular; palpebral lobes marked off by furrows; anterior sections of facial sutures converging forward running parallel and close to axial furrows ; posterior sections curving backward-outward to cross posterior borders; eyes of moderate size, pedunculate in some species, usually situated behind mid-length of glabella and close to it; librigenae usually broadly falciform but may develop broad subgenal notch inside librigenal spine . Rostral plate usually subtrapezoidal, transversely elongate, bounded laterally by connective sutures continuous with faciail sutures; flattened or convex; produced anteriorly beneath cranidial projection in some species. Hypostoma subquadrate; posterior margin transverse or indented; middle body swollen, circumscribed or undefined at rear; posterior lateral lobes of middle body varying in size and definition; lateral borders moderately broad to broad, anterior wings more or less strongly developed; surface tuberculate, pitted, and with anastomosing raised lines. Thorax composed of 11 segments in species with 3 pairs of pleurae in pygidium (one species has 10 segments in thorax and 4 pairs of pleurae in pygidium); axis broad, arched transversely; articulating half-rings short; axial furrows shallow; pleurae horizontal and transverse proximally, bent downward and backward at fulcra, terminating in short free points; submedial pleural furrows usually present. Pygidium with axis extending part or whole of length, wide anteriorly, tapering or flaring posteriorly; with 1 to 5 axial rings; posterior pair of pleurae may be unfurrowed; pleurae usually end in free points, but margin of posterior pair may be rounded or produced into a posterior spine, of great length in some species; pygidium modified in certain Devonian ceratarginids. Doublure broad, particularly on pygidium, carrying usual terrace lines, spaced far apart. Apodemes not developed. Dorsal surface characteristically marked by scattered large tubercles with smaller tubercles between them but may be smooth or punctuate; some forms, especially among Devonian genera tend to develop spines or skeletal outgrowths on parts of dorsal exoskeleton. Most species medium-sized but some are exceptionally large.

Amphilichas