Tasmanites sinuosus (Winslow)

Meehan, Kimberly C., 2022, Devonian smooth-walled tasmanids and new insights of life-cycle descriptions through fluorescence microscopy, Phytotaxa 554 (3), pp. 211-220 : 216-217

Tasmanites sinuosus (Winslow)

Remarks: The species sinuosus are characterized by having spherical vesicles usually ranging from 50 µm to 400 µm in diameter with smooth to rough rugose surfaces. The vesicle wall may be punctate, unlaminated and 2 µm to 13 µm thick (~5% vesicle thickness). Of the features available for use for speciation, overall diameter of the disseminule and wall thickness are most determinable as punctae and other ornamentation are often absent. Winslow (1962) indicates that the occurrence of T. sinuosus is limited to the Upper Devonian, but Wicander (1983) extended the range to the Middle Devonian, this was confirmed by Chamberlain et al. (2016), and herein.

Material: 283 well preserved remineralized silicate specimens ( Figs. 2–5 ) were retrieved from all sieve ranges. Mean diameter = 110 µm; std. dev. = ± 23.25 µm.

Description: The specimens illustrated in Figures 2 and 3 have diameters averaging about 120 µm. Of the six Middle Devonian Appalachian Seaway tasmanitid species listed above, only T. sinuosus has vesicles as small as these Oatka Creek tasmanitid specimens. In addition, the specimens illustrated in Figure 4 and 5 , have simple vesicle walls, which although thin compared to most tasmanitids (about 5% vesicle diameter), lie within the range of wall thickness Winslow (1962) attributes to T. sinuosus . The about 30% (85 specimens) had visible punctation pits. We thus suggest that these specimens most closely resemble T. sinuosus .

Figures

FIGURE 2. Transmitted and incident light images of silica-rich microspherules retrieved from the Oatka Creek Formation, Leroy, New York. Internal to external (left to right) focal point shift imaging approach allows for internal structures at different points within the tasmanid to be imaged: 1a–e: internal pyritic inclusions imaged throughout single tasmanid, inclusions interpreted to be portions of gamete stage internal strucres; 2a–e, surface punctae visible (2a) in addition to internal pyritic inclusions; 3 a–e conjoined or splitting tasmanid containing internal pyritic inclusions. Images taken at a magnification of 10x, average diameter of all cysts, 125 µm.

FIGURE 3. Transmitted and incident light images of silica-rich microspherules retrieved from the Oatka Creek Formation, Leroy, New York. 1a–c conjoined or splitting tasmanid containing internal pyritic inclusions, interpreted to be a dividing cyst; 2a–c single tasmanid with no pyritic inclusions but numerous surficial punctae, interpreted to be a vegetative cyst; 3a–c tasmanid with well defined internal structure interpreted to be a resting cyst. Images taken at a magnification of 10x, average diameter of all cysts, 125 µm.

FIGURE 4. Fluorescence microscopy images of select silica-rich microspherules from the Oatka Creek Formation, Leroy, New York. Black and white arrows denote locations of diminutive spherules within endocysts. Yellow arrows denote the edge of the external wall. Average diameter of tasmanid 4a–c is 125 µm; 4d diameter is 50 µm; 4e tasmanid diameter is 125 µm; 4f tasmanid horizontal diameter is 120 µm with a height of ~130 µm.

FIGURE 5. Fluorescence microscopy images of select silica-rich microspherules from the Oatka Creek Formation, Leroy, New York. 5a: tasmanid interpreted to be a gamete sack; 5b” tasmanid interpreted to be a diving stage cyst.