Map point data provided by iDigBio.
- C5 Sequence (Lower Whitewater)
- C2 Sequence (Fairview: Fairmount, Mount Hope)
Identification in Hand Sample
- Zoarium Morphology: Frondose, branching; smaller stems
- Zoecia: Direct; thin walled (sometimes crenulated); small, variable acanthopores; 9 in 2mm
- Mesozooids: Few, generally clustered
- Monticules: Surface smooth
- Maculae: Larger cell apertures
Brown & Daly (1985):
- Diagnosis: Zoaria ramose, with thick-walled zooecia in narrow exozone, diaphragms absent in endozone but common in exozone, abundant cystiphragms, no mesozooecia, and numerous small acanthopores.
- Description: Zooecia in endozone polygonal to angular, rising straight and bending very slightly outward, then bending sharply into narrow exozone; new zooecia having slender, pointed proximal tips. Intermonticular zooecia in exozone polygonal, small (9+ in 2 mm, 0.164 mm MZD; table 16), and somewhat oblique to surface. Zooecial apertures typically polygonal to subpolygonal and showing cut edges of cystiphragms or diaphragms; a few apertures slightly inflected by acanthopores.
Zooecial walls in endozone thin, typically straight but locally slightly wavy, thickening shortly at base of exozone, moderately thick (0.048 mm ZWT) in exozone, but thickening irregularly to surface. Walls composed of faintly defined, bluntly pointed laminae abutting to form an irregular dark median line. In tangential sections walls having a granular-appearing dark inner zone flanked by a more translucent outer layer, or appearing faintly laminate with a poorly developed median line. Faintness of wall structure reflecting uniform translucency of laminae; no dark wall laminae present.
Diaphragms absent in endozone, a few present in curve to exozone and several irregularly distributed throughout exozone, generally widely space, remote, or absent to surface. Diaphragms typically thin and straight, horizontal or inclined, merging into the walls with long diaphragm-wall lining units but adding no appreciable thickness to the walls.
Cystiphragms arising in early part of exozone in overlapping series, generally along distal wall only, occasionally in multiple overlappings as compound forms, commonly thick walled, and contributing significantly to wall thickness.
No mesozooecia. Acanthopores abundant to common, generally small (0.037 mm MAD), at wall angles and in between, generally appearing in tangential sections as dark spots, some with faint lumen; deep sections showing a few offset into the tube opening. Longitudinal sections showing acanthopores arising within exozone and extending along walls, some to surface, and consisting of inconspicuous, sharply pointed, concentrically laminated tissue about a faint central core; few in tangential sections having any trace of concentric laminations.
Monticules low to nearly flush, consisting of several large angular zooecia with slightly thinner walls, and, commonly, more numerous small dark acanthopores than in intermonticular areas. Numerous small tubes in center and in between megazooecia probably young zooecia rather than mesozooecia.
- Discussion: The Dillsboro specimens typically have thin exozones with slightly oblique zooecia. Bassler reported that this species had direct zooecia, but his illustration (1903, pl. 21, fig. 8) showed that they were slightly oblique. Bassler also reported the presence of mesozooecia, but we can detect no trace of them in his illustrations and believe that they were young zooecia.
- Zoarium small, composed of cylindrical to subfrondescent branching stems 2-4 mm. in diameter. Surface smooth, zooecia direct, about nine in 2 mm. Mesopores moderately developed in maculae and elsewhere. Acanthopores small, variable in number, sometimes 8-10 around a zooecium.
Common in the Fairmount of the southern Bluegrass.
- Zoarium small, generally less than 3 cm. in height, ramose, dividing rather regularly at short intervals; branches subcylindrical but with a tendency to become frondescent, 2 to 4 mm. thick and 3 to 9 mm. wide. Surface commonly smooth, the clusters of usually larger cells rarely forming low monticules. Zooecial apertures angular, direct, about nine in 2 mm. A moderate number of mesopores present both in the clusters and elsewhere. Acanthopores small, varying in number, sometimes as many as eight or ten surrounding a zooecium. Diaphragms and cystiphragms rather numerous and developed in the peripheral region only.
- The shape of the zoarium, the small cells, and smooth surface characterize this species. The points of difference from H. dumosa, probably its nearest relative, are indicated under the description of that form.