Gleicheniales Schimper, 1869

Bodnar, Josefina, Drovandi, Juan Martín, Morel, Eduardo Manuel & Ganuza, Daniel Gustavo, 2018, Middle Triassic dipterid ferns from west-central Argentina and their relationship to palaeoclimatic changes, Acta Palaeontologica Polonica 63 (2), pp. 397-416 : 399-400

Order Gleicheniales Schimper, 1869 Family Dipteridaceae Seward and Dale, 1901

Type genus: Dipteris Reinwardt, 1828 .

Remarks.—The leaves of fossil Dipteridaceae are characterized by the frond rachis that initially dichotomizes into two arms, each of which may then exhibit unequal dichotomies in an anadromic direction (i.e., toward the median plane of the frond; Cantrill 1995). The manner of division of the fronds, mode of disposition of pinnae, degree of dissection of laminae, and soral characters were utilized by Ôishi and Yamasita (1936) to recognize the subfamilies Dipteroideae, Goeppertelloideae, and Camptopteroideae. The Goeppertelloideae subfamily contains one fossil genus, Goeppertella , and is distinctive in being the only subfamily that has bipinnate pinnae and rachial pinnulae ( Ôishi and Yamasita 1936; Arrondo and Petriella 1982). The Camptopteroideae, comprising the fossil genus Camptopteris , is similar to Dipteroideae, except the fact that the pinnae are spirally disposed on the rachial arms ( Nathorst 1906). In the Dipteroideae, the frond lamina undergoes an initial dichotomy producing two equal halves, which can be entire or pinnate ( Ôishi and Yamasita 1936; Cantrill 1995). Boundaries between fossil taxa of this subfamily have been subject to much discussion ( Herbst 1992a, b; Cantrill 1995). Ôishi and Yamasita (1936) first included the genera Dipteris , Hausmannia (with two subgenera Hausmannia and Protorhipis), Clathropteris , Dictyophyllum , and Thaumatopteris in the Dipteroideae. Webb (1982) synonymized Thaumatopteris with Dictyophyllum , and afterwards Herbst (1992a, b) included the genera Clathropteris , Dictyophyllum , and Thaumatopteris as subgenera within Dictyophyllum . However, these proposals have found little acceptance, and the genera Thaumatopteris and Clathropteris are still widely used till date (e.g., Zhou 1995; Popa 1999; van Konijnenburg-van Cittert 2002; Wang 2002; Popa et al. 2003; Guignard et al. 2009; Schweitzer et al. 2009; Taylor et al. 2009; Bomfleur and Kerp 2010; Kustatscher et al. 2014; Choo et al. 2016).

Here, we consider Hausmannia , Clathropteris , Dictyophyllum , and Thaumatopteris as independent genera, without any subgeneric divisions. Hausmannia has a leaf lamina that dichotomizes once into two fan-shaped halves and is not pinnate, although the lamina is commonly greatly dissected ( Cantrill 1995). Clathropteris is distinguished by the lamina that is divided for more than two-thirds of the total length and the conspicuous orthogonal venation pattern formed by secondary and tertiary veins (e.g., Ôishi and Yamasita 1936; Bomfleur and Kerp 2010; Choo et al. 2016). Dictyophyllum is characterized by a once-pinnate lamina and polygonal but not orthogonal areoles (e.g., Ôishi and Yamasita 1936). In Thaumatopteris , the pinnae are disposed in a funnel shape at the top of the petiole and are deeply dissected, often giving rise to pinnulae (e.g., Ôishi and Yamasita 1936).