Cryptolithus tesselatus

Classification
Phylum: Arthropoda
Class: Trilobita
Order: Asaphida
Family: Trinucleidae
Genus: Cryptolithus
Species: Cryptolithus tesselatus (Green, 1832)

Taxonomic Details

    Includes: Shaw and Lesperance (1984) regard C. lorettensis Foerste and C. bellulus (Ulrich) as “morphs, races, or regional variants” of C. tesselatus that do not merit formal taxonomic status.
    Synonyms: Sometimes called the “lace-bone trilobite” due to its distinct cephalic fringe.

Stratigraphic Occurrences

C.tesselatus

Geographic Occurrences

		
Map point data provided by iDigBio.

Stratigraphic Description

Sequences (Formations)

  • C3 Sequence (Mount Auburn, Corryville)
  • C2 Sequence (Bellevue, Fairview: Fairmount, Mount Hope)
  • C1 Sequence (Clays Ferry/Kope: McMicken, Southgate, Economy/Fulton)

Identification in Hand Sample

  • Cephalon short, wide, semi-elliptical.
  • Cephalic fringe distinct, ornamented by concentric and radiating rows of pits.
  • Glabella convex and prominent, smooth.
  • Lacks eyes.
  • Thorax with 6 segments.
  • Pygidium is short, wide, and rounded to sub-triangular in outline.

Cryptolithus tesselatus from Whitewater Formation of Butler County, Ohio (MUGM 28928, left) and from Eden Formation of Kenton County, Kentucky (OUIP 16)

Published Description

Holland (UGA Strat Lab, 2013):

  • “Note: Shaw and Lesperance (1984) regard C. lorettensis Foerste and C. bellulus (Ulrich) as “morphs, races, or regional variants” of C. tessellates that do not merit formal taxonomic status. Also note that the McMicken through Mount Auburn occurrences are based on Dalve, 1948. These occurrences cannot be confirmed and are considered here as suspect. Foerste (1910) reports that Cryptolithus ranges up to the middle Southgate.”

Davis (1998):

  • Trilobite. Fig. 11: almost complete specimen showing the cephalon with protruding glabella, the few thoracic segments, and the short, road pygidium.
  • Fig. 12: a fragment of the “lace collar” and one long genal spine. Edenian and Maysvillian; common in the Southgate. (Specimens of C. bellulus commonly have been misidentified as C. tesselatus, which does not occur in the local rocks).
  • Fig. 13: Cephalon showing the broad, semi-circular fringe which runs around the edge of the cephalon and is pitted in such a way as to have earned this species the name “lace-collar trilobite.”

Fossils of Ohio (1996):

  • Cryptolithus (Green) has an exoskeleton up to 3 cm in length. The cephalon is short, wide, semielliptical in outline, and has a wide fringe that is ornamented by concentric and radiating rows of pits; pleural areas are nearly twice as wide as the axis. The glabella is convex, expanding forward, and has three short pairs of lateral glabellar furrows. The occipital ring has a moderately long medial spine. Eyes are absent. Facial sutures are marginal. Pleural areas of fixigenae, inside fringe, are smooth and convex. Genal spines are long, narrow, and directed posteriorly. The thorax has 6 segments; pleural areas are wider than the axis; each pleaura is nearly straight and terminates bluntly. The pygidium is short, wide, and rounded-subtriangular in outline. The axis has several axial rings, and a terminal piece. Pleural fields have several pairs of shallow interpleural furrows.”
  • Crytpolithus, which is sometimes called the lace-collar trilobite (Davis, 1985) because of its distinct cephalic fringe, is present through much of the Cincinnatian Series strata of SW Ohio. Most specimens have been collected from the Kope, Fairview, and Grant Lake Formations.”
  • “Only one species (C. tesselatus) seems to be present in the Cincinnatian of Ohio. In some older literature, this species was identified as C. bellulus.”

McFarlan (1931):

  • Head semicircular or subcrescentic, typically about, 10 mm. long, 15 mm. wide, convexity of about 6 mm. Genal angles with or without spines. Glabella smooth, very prominent, produced posteriorly into a short, blunt spine. Anterior and lateral margins surrounded by a broad flattened border, marked by 3-5 concentric rows of deep rounded pits in front and one or two additional rows laterally, becoming irregular toward the genal angles. More familiarly known as “Trinucleus concentricus.” Particularly common in the Eden, also in the Cynthiana. It is listed by Nickles from the Point Pleasant beds (1902, p. 64). It occurs in large numbers thirty feet above the Cornishville and about 75 feet below the Plectambonites layers of the Million in Lincoln and Boyle counties.

Green (1832):

  • Outline of the buckler hemispherical, the edge surrounded by a semicircular border of tessellated or rounded punctures, in three concentric rows in front on each side near the posterior angle of the buckler, these rows of punctures are more numerous; the front is highly convex; is rounded before, and gradually tapers towards the abdomen. The cheeks form spherical triangles and are entirely destitute of oculiferous tubercles or any other markings, their posterior angles project beyond the sides of the abdomen. Abdomen and tail very much compressed and composed of about ten articulations; costal arches of the lateral lobes grooved, tail attenuated. Whole length half an inch. The Cryptolithus tessellatus resembles a good deal the Entomostracites granulatus of Wahlenberg and which Dr. Dalman calls Asaphus granulatus. The figure of this animal given by Brongniart, table 3 fig. 7, appears to be quite imperfect and is very unlike except in the buckler, the representation of Wahlenberg’s fossil given by Dalman, table 2 fig. 6. Though the angles of the buckler in the Asaphus granulatus are much more elongated than those of the C. tessellatus, it may perhaps be another species of the same genus.
  • The Cryptolithus tessellatus occurs also in the limestone, which according to Dr. Bigsby, overlays the sandstone in the island of Montreal. At most of its localities it is associated with the Isotelus, the Calymene, and with several species of Asaphus. The Cryptolithus which is entirely destitute of eyes, being thus found with the oculiferous species, is an interesting fact and controverts the opinion of Professor Wahlenberg that the trilobites which are without eyes belong to a geological epoch more ancient than those which are furnished with oculiform tubercles. That organic remains furnish us with the most satisfactory evidence of the identity or dissimilarity of certain formations is a disputed point with some geologists. It cannot reasonably be doubted that new and isolated facts have been made, the basis of a too hasty generalization.