Formerly: Catazyga schuchertana, originally Athyris headi
- 1865 Athyris headi Billings, Pal. Foss., 1, Geol. Survv., Can., p. 147, fig. 125.
- 1893 Catazyga headi Hall and Clarke, 8, pt. 2, p. 158, fig. 151; pl. 54, figs. 24-26, 30.
- 1924 Catazyga headi Foerste, Upper Ordovician faunas of Ontario and Quebec, p. 128-130, pl. 10, fig. 17 a, b.
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Map point data provided by iDigBio.
- C5 Sequence (Waynesville)
Identification in Hand Sample
- Shells rounded, smooth. Faint costae.
- Ventral valve has a shallow sulcus.
- Pedicle valve more convex than brachial valve, weak narrow anterior brachial valve sulcus and broad pedicle valve fold
- Internally distinctive muscle fields
- Cardinal process irregular, bulky
- Articulate brachiopod. Smooth, rounded shells with faint costae. Ventral valve with shallow sulcus. Waynesville. Rare.
- “Diagnosis. Medium sized to large, globose Catazyga with maxmum width at midlength, hypercline beaks, foramen and area obscured at maturity. Pedicle valve more convex than brachial valve, often with weak narrow anterior brachial valve sulcus and broad pedicle valve fold (over all weakly uniplicate). Internally distinctive muscle fields, thick pedicle callosities, small outwardly extended deltidial plates, dental cavities horizontally elongated, teeth massive, lacking accessory lobes, cardinal process irregular, bulky; crura thick. Spiralia-jugum unstudied.”
- “Description: Shells average width, peaks at 14 mm, maximum 19 mm, depth peaking at 9 mm, mostly longer than wide (text-fig. 6), apical angles 105- 110° (average 108°). Pedicle area covered by beak in very early growth stages, before shell is 10 mm wide; sometimes pedicle opening expanded as slit in umbo. Ribs very fine posteriorly (at 5 mm, 25- 30 ribs per 5-mm arc) but at
20 mm from umbo coarsening to 8- 11 ribs per 5-mm arc; ribs round-broad crested and narrow-troughed. Brachial valve less convex but well-rounded; both valves usually sulcate with the pedicle valve having broad, flat sulcus. The adductor muscle fields are quite variable. The ventral adductor pad occupies about a quarter of the shell length, is wider than long, rectangular to rounded, and frequently skew or irregular; medially it is divided by a broad, low septum and laterally each side has three to four grooved lobes (usually three). The ventral diductors appear to be raised
on two rounded irregular lobes, fusing posteriorly and sometimes raised off the shell floor. These structures may represent pedicle muscle callosity, and if that is the case
the diductors possibly are located between the pedicle callosity and the adductor field. The dorsal muscle field is difficult to interpret. Adductors are in the form of two pairs, a posterior bean-shaped pair and an antero-medial pear-shaped pair divided by a rounded median septum. Closer to the hinge plate are one to three pairs of small depressions of unknown origin, possibly accessory diductors (text-fig. 9). The serial sections illustrated (text-figs. 10- 11) are largely self-explanatory. Most striking are the thick pedicle cavity linings (squared in outline) and massive hinge plates generally lacking in zygospirinids. The axis of the dental cavity is dorso-anteriorly ventral posteriorly and horizontal anteriorly; teeth are simple stumps, free anteriorly. The pedicle opening is either hidden or sometimes expanded into the ventral umbo as a minute, narrow slit; deltidial plates are pointed dorsally rather than medially. A cardinal process is present in the form of thick irregular outgrowths capping the ends of the socket plate, expanding well into the pedicle cavity ; the groove between the socket plates is narrow and slit-like. The crura arise from a point source hidden deep within the hinge plate, and are rounded in cross section; anteriorly they stand free as thin, raised ridges and then direct themselves ventrally and sharply laterally. Further brachidial structures still unknown (see reconstruction of complete C. anticostiensis in text-fig. 9).”
- “Remarks. C. headi, like all Catazyga, had a small functioning pedicle or loss of pedicle in maturity. Epifauna was very scarce on the shells examined, and wherefound, consisted of small serpulids (Cornuli1es?) and Hederella normally located.”
- Outline oval-oblong, strongly and evenly convex, except toward the beak where the umbo may be carinated. In some an obscure median groove extends from anterior edge of pedicle valve to within one-third of length of valve from beak, but in many it is absent, and in some a similar groove is seen along the brachial valve. Surface marked by numerous very fine, moderately elevated, radiating striae, of which eight to ten occur in width of 4 mm.
- Type Specimens. From the Waynesville member of Richmond drift, opposite Three Rivers,Que.
- Locality and Horizon. In the Cryptolithus zone, undetermined species of Catazyga occur in the Nicolet River section, also at Petite Caroline, St. Hugues, St. Hyacinthe, and at the Don brick-yard, Toronto. In the Proetus zone, Catazyga occurs at Weston, near Toronto.
- In the Waynesville member C.headi is found at Snake island, the Nicolet River section, Huron river, St. Hilaire, St. Hugues (loose), Vars, Streetsville, Workman brook near Meaford, Bass Lake road south of Little Current; at Kagawong falls.
Insouthwestern Ohio and southeastern Indiana C.headi is fairly common in the basal part of the Blanchester division of the Waynesville member and in the underlying part of the Clarksville division.
Catazyga headi from the Waynesville Formation of Waynesville, Ohio (CMC 19134)