This is Mazon Monday post #115. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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Crenulopteris acadica is one of the most common flora fossils found in the Mazon Creek biota. Some of the localities seem to be absolutely full of it. The fossils can range in size from a few inches to over a foot. It is a true fern belonging to the group Filicopsida, which is a subdivision of Pteridophyta. Pteridophyta includes all extant and extinct ferns and first appears in the fossil record during the Devonian Period.
George Langford called it Asterotheca lamuriana. ESCONI's "Keys to Mazon Creek Plants" referred to it as Pecopteris lamuriana. While in Jack Wittry's "Mazon Creek Fossil Flora", it can found as Lobatopteris lamuriana. For Wittry's vastly updated book "A Comprehensive Guide to the Fossil Flora of Mazon Creek", it moved to Crenulopteris acadica. For a very common fossil, its naming has a very complicated history.
Crenulopteris acadica (Bell) Wittry et al., 2014
1880. Pecopteris villosa? Brongniart; Lesquereux: p. 253
1899. Pecopteris villosa? Brongniart; White: p. 94
1924. Asterotheca miltoni (non Artis); Kidston: pl. 121, figs. 4, (?)2; (non pl. 122 = Pecopteris camertonensis other figured specimens probably correctly identified)
1925. Pecopteris vestita (non Lesquereux); Noé: pl. 29, fig 2; pl. 30, fig. 2
1925. Pecopteris miltoni (non Artis); Noé: pl. 34, fig. 4
1938. Pecopteris miltoni (non Artis); Bell: p. 71, pl. 67, figs. 2, 4 (non fig. 3 = Diplazites unita); pl. 68; pl. 69, figs. 1-3
1958. Asterotheca lamuriana (non Heer); Langford: p. 166, fig. 282
1958. Asterotheca lepidorachis (non Brongniart); Langford: p. 167, fig. 283
1959. Lobatopteris vestita (non Lesquereux); Wagner: p. 22
1962. Pecopteris acadica Bell: p. 32, pl. 25, figs. 1-3; pl. 56 fig. 7
1969. Pecopteris lamuriana (non Heer); Darrah: p. 138, pl. 20, fig. 1; pl. 24, fig. 1; pl. 62, figs. 1, 2; (non pl. 15, figs. 3, 4 = Pecopteris subcrenulata)
1979. Pecopteris miltoni (non Artis); Janssen: p. 127; p. 128, figs. 109, 110; p. 129, fig. 111
1979. Asterotheca arborescens (non Schlotheim); Janssen: text in part p. 130; p. 131, fig. 113, non fig. 117n
1980. Pecopteris acadica Bell; Zodrow: p. 59, pl. 72, fig. 2; pl. 77 fig. 2; (non pl. 74, figs. 1, 2; pl. 75, fig. 1; pl. 77, fig. 1; pl. 78, fig. 1 = Pecopteris camertonensis; pl, 76, figs. 1, 2 = indeterminate))
1982. Pecopteris lamuriana (non Heer); Oleksyshyn: p. 80, fig. 16, E-G
1994. Lobatopteris vestita (non Lesquereux) Wagner; Cleal: p. 155, fig. 77D
2014. Crenulopteris acadica Wittry et al.: pp. 615-643DESCRIPTION: The primary pinnae are very large, possibly up to a meter in width, with smooth and punctate rachises. The penultimate pinnae are linear-lanceolate and taper very gently toward a small, round lobe at the apex. The pinnules remain free all the way to the tip. The rachises are thick, straight, longitudinally striated, and punctate. The ultimate pinnae are linear to sublanceolate, alternate, rise from the rachis at an angle of anywhere from 10° to nearly perpendicular, and terminate obtusely or subacutely. They consist of ten lobes per side when fully mature. The lobes on the ultimate pinnae are alternate, small, obtuse, and attached by their full bases. Both entire pinnules and lobed ultimate pinnae are of different lengths along the rachis. The venation in entire linear pinnules consists of a strong, straight midvein and arcuate lateral veins that rise from the midvein at an angle of 45°, and fork once near their base. The upper vein divides one to three times before meeting the margin at near ly a right angle. In the lobed ultimate pinnae, the veins form bundles that correspond to each of the lobes. A villous coating on both sides of the pinnules usually obscures the venation from view. The isolated spores are correlated with Punctatosporites/Laevigatosporites minutus. The sori have an asterothecoid appearance with typically five sporangia.
REMARKS: Crenulopteris acadica is the second most common flora species found in the Mazon Creek flora, though fertile examples (see Fig. 7) are rarely found. The amount of variability figured here is due to variations in the frond form during the growth stages of large tree ferns. The synonymy list shows how other authors have tried to interpret this form, making it the most confused taxon in the Mazon Creek flora. Also see Kankakeea grundyi.
One of C. acadica distinguishing features are the crenulations on its pinnules.
Specimens
