Cedarina schachti
- Dataset
- The Marjuman trilobite Cedarina Lochman: thoracic morphology, systematics, and new species from western Utah and eastern Nevada, USA
- Rank
- SPECIES
- Published in
- Adrain, Jonathan M., Peters, Shanan E., Westrop, Stephen R. (2009): The Marjuman trilobite Cedarina Lochman: thoracic morphology, systematics, and new species from western Utah and eastern Nevada, USA. Zootaxa 2218: 35-58, DOI: 10.5281/zenodo.189977
Classification
- kingdom
- Animalia
- phylum
- Arthropoda
- class
- Trilobita
- order
- Ptychopariida
- family
- Cedariidae
- genus
- Cedarina
- species
- Cedarina schachti
description
Description. Cephalon with sagittal length 46.6 % (42.9 – 50.4) width across base of genal spines; cranidium with sagittal length 54.3 % (49.5 – 59.8) maximum width across posterior fixigenae; width across anterior sections of facial suture 96.5 % (89.8 – 103.3) width across midlength of palpebral lobes and 47.6 % (45.5 – 50.0) width across posterior fixigenae; dorsal cephalic sculpture of fine, sparsely distributed granules on borders, prominent caecal ridges, grooves, and pits on genal fields, less well impressed and more finely pitted proximally, deeper and more radially oriented distally; fine granules on interocular fixigena, distal part of posterior fixigena, and all of glabella, and very faint small tubercles scattered over proximal posterior fixigena and rear of glabella, particularly on LO; glabella with sagittal length (including LO) 71.5 % (70.0 – 72.3) cranidial sagittal length and maximum width across LO 70.3 % (63.2 – 83.4) sagittal length; glabella low, with only weak to moderate dorsal inflation, trapezoidal in outline; axial furrows with more or less straight, anteriorly convergent course, bowed out slightly around LO, in at SO, gently out around L 1, and very slightly inward opposite remaining anterior part of glabella; preglabellar furrow variable from quite strongly anteriorly convex (Fig. 8 A) to more transverse (Fig. 6), contact with axial furrow at rounded angle; axial and preglabellar furrows similarly narrow and moderately incised; glabellar furrows effaced, visible distally as very slight indentations in lateral glabellar margin; L 1 and L 2 expressed mainly as slight swellings, L 3 not obvious dorsally; SO with transverse course, very slightly bowed forward medially, very short (sag., exsag.), slightly longer sagittally, shallow laterally, deeper in middle 80 %, and deepest sagittally; LO subrectangular, longer (sag., exsag.) than axial rings of anterior thoracic segments, slightly shorter exsagittally than sagittally, with dorsal sculpture of very fine granules, rear margin evenly posteriorly arcuate; preglabellar field long; anterior border longer sagittally than exsagittally owing to oblique course of long connective suture; border dorsally flattened on anterior aspect, sloped sharply towards border furrow posteriorly, lacking dorsal sculpture, anterior margin evenly anteriorly arcuate; anterior border furrow short (sag.; exsag.), relatively shallow; anterior sections of facial sutures strongly anteriorly divergent in front of palpebral lobe, bowing near anterior border furrow to run into oblique connective suture; palpebral lobes large, anteroposteriorly elongate, lacking dorsal sculpture, area around lateral margin raised; palpebral furrow expressed as break in slope; eye ridge running obliquely from anterior edge of palpebral lobe to just in front of L 3 (best expressed on Fig. 6); interocular fixigenae narrow, lacking sculpture; rear of palpebral lobe nearly abutting glabella; posterior section of facial suture running transversely at rear of palpebral lobe, turned anteriorly to form cedariform lobe on posterior fixigena; posterior border inflated and semicylindrical, short (exsag.) near axial furrow, longer distally; posterior border furrow deep and short (exsag.); both border and border furrow deflected posteriorly near fulcrum. Librigena with eye large and long; eye socle not obvious, but region is crushed on all available specimens; furrow separating base of visual surface from field shallow, curved subparallel with outer margin of palpebral lobe; field narrowest about 80 % of distance anteriorly, wider immediately in front of eye, and much wider posteriorly at rear of eye, with moderate dorsal inflation, transected by subparallel caecal trunks, with very subdued scattered tubercles on rear part; lateral border furrow narrow, relatively shallow, edge sharply defined along contact with border, contact with field more gently sloping, furrow curved parallel with lateral margin of border; posterior border and lateral border completely confluent across posterior section of facial suture, no sutural ridges developed; lateral border flattened in dorsal aspect anteriorly, more inflated and semicylindrical posteriorly, similar in width to anterior border anteriorly, wider posteriorly to base of genal spine, border lacking dorsal sculpture; genal spine broadest just behind base, long and robust, extending nearly to (Fig. 5) or just past (Fig. 6) rear of pygidium, curved slightly adaxially, tapering more or less evenly to sharp, slightly outwardly turned point. Hypostome known only from poorly preserved mold (Fig. 7), maximum width anteriorly about 73 percent sagittal length; lateral margins slightly posteriorly convergent, width at rear about 85 % anterior width; posterior margin deflected sharply from lateral margin, with moderate posterior curvature; hypostome was apparently quite convex. Rostral plate unknown. Thorax of 10 segments, with very long median axial spine on eighth; axial ring of similar length sagittally and exsagittally, with dorsal sculpture of fine granules and relatively densely distributed, very subdued tubercles; axial furrow narrow, sharply incised, deflected laterally around side of axial ring; pleural furrow prominent, deep, but quite short (exsag.), contacts axial furrow, with transversely straight course proximally, deflected and curved posteriorly distally at about fulcrum; both anterior and posterior pleural bands raised and ridge-like, with transverse row of very fine tubercles on each; posterior pleural band shorter distally; anterior and posterior bands unite distally to form laterally protruded, posterolaterally directed, pleural spine; axis of successive segments steadily reduced in width posteriorly; axis of eighth segment almost entirely occupied by base of robust spine; spine somewhat longer than distance from anterior margin of cranidium to posterior margin of pygidium, tapered gradually to sharp point; pleural spines small anteriorly, increasing in size posteriorly to reach maximum around seventh or eighth segment, those of ninth and tenth segment slightly smaller but more posteriorly directed. Pygidium poorly known; of typical morphology for genus, micropygous, with width about three times sagittal length; apparently composed of 3 – 4 segments; margin complete, pleurae not extended into spines as in thorax.
diagnosis
Diagnosis. Frontal area and preglabellar field long; anterior border evenly anteriorly arcuate; anterior sections of facial suture strongly anteriorly divergent; palpebral lobes large; pygidium relatively narrow and long.
discussion
Discussion. Cedarina vale Lochman, 1940, the type species from the Bonneterre Dolomite of Missouri, is known only from tiny photographs of one cranidium, one librigena, and one pygidium in the original description. Hu (1983, pl. 1, figs. 34 – 38) assigned and illustrated two cranidia, a librigena, and a pygidium. These are clearly morphologically distinct from Lochman's species. Hu (1983, p. 278) recognized this, but opined that " Comparing these morphologic differences with the present studied materials, it might assume that this species has a broad morphologic varieties within the same species population. " (sic) It is not clear why one would assume this, as a more likely explanation is that they are simply different taxa. Although Hu's material was collected by Lochman and was said to be (Hu, 1983, p. 275) " from the same general area Saline Creek at Avon, Ste. Genevieve County, Missouri, " (sic) no further stratigraphic information was given and whether Hu's material is from the same horizon as Lochman's is not known. Cedarina schachti differs from C. vale in the possession of an evenly forwardly arcuate anterior border, versus one with a strong posterior inflection medially. The anterior border is concomitantly shorter sagittally. The anterior sections of the facial sutures are more anteriorly divergent in C. schachti, the preglabellar field is longer, and the frontal areas occupy a larger area. The glabella is more nearly parallel sided, and relatively narrower at the base. The librigenal field of C. schachti is considerably wider. Although the pygidium of C. schachti is not well known, its outline (Fig. 7) clearly shows that is is relatively narrower and longer than that of C. vale.
etymology
Etymology. The species is named in honour of Robert Schacht, who collected and donated the holotype and one of the paratype specimens.
materials_examined
Type Material. Holotype, FMNH PE 57116, paratypes SUI 102868, 104476, and additional specimens USNM 437968, 437975, from the Weeks Formation (Marjuman; Cedaria Zone), Weeks Canyon, northern House Range, Millard County, western Utah, USA.
Name
- Homonyms
- Cedarina schachti
- Cedarina schachti