The fern Konijnenburgia alata in the mid-Cretaceous of Patagonia, and the Matoniaceae fossil record

Highlights

• The fern Konijnenburgia alata (Matoniaceae) from Patagonia, is revised and emended.

• It comes from the Piedra Clavada Fm (latest Albian, Austral Basin).

• An Albian-Cenomanian increase in diversity of Matoniaceae is recorded.

• Its relation with paleo-temperature fluctuation or angiosperm rise is discussed.

Abstract

Based on new material from the uppermost Albian levels of Piedra Clavada Formation (Austral Basin, Argentina), the species Konijnenburgia alata (Matoniaceae) is re-examined, its diagnosis emended, and a formal lectotype from the historic type collection is here designated. A complete comparison with extant and fossil Matoniaceae is provided, with discussions about synonymies among fossil genera. The Matoniaceae megafossil records possess a Cretaceous acme in the Albian-Cenomanian with a cosmopolitan distribution. Its conspicuous macro and microfossil record from southern Patagonia is coherent with this fact. Reports of fossil Matoniaceae decrease following the Turonian, likely related to global temperature fall and/or increase of the angiosperm abundance and diversity in the floristic assemblages.

Introduction

The Matoniaceae are leptosporangiate ferns currently restricted to the Malay Archipielago, including New Guinea and Thailand (Kramer, 1990, Lindsay et al., 2003). They comprise only two extant genera: Matonia with two terrestrial species (M. foxworthyi Copel. and M. pectinata R. Br.) and Phanerosorus with two pendant lithophyte species (P. major Diels and P. sarmentosus (Baker) Copel.). These ferns form a monophyletic group sister to Dipteridaceae. Matoniaceae and Dipteridaceae are included in Gleicheniales, and early diverged lineage within the leptosporangiate ferns (Kato and Setoguchi, 1999, Pryer et al., 2004, Schuettpelz and Pryer, 2007).

Despite their extant restricted distribution, Matoniaceae were common and widespread ferns in Mesozoic floras (see Suppl. Mat. 1). They first appeared and diversified at latitudes higher than 40° in both Hemispheres and spread into lower latitudes during the Triassic (Skog, 2001). Permineralized petioles (Soloripteris rupex Millay and Taylor, 1990) and detached indusiate sori (Tomaniopteris katonii Klavins et al., 2004) from the lower Middle Triassic in Antarctica are the oldest unequivocal occurrences for this family. By the Middle Jurassic to the Early Cretaceous, Matoniaceae had spread to a variety of habitats and were globally distributed (Skog, 2001, Van Konijnenburg-Van Cittert, 2002); they were cosmopolitan through the mid-Cretaceous (e.g. Halle, 1913, Krassilov, 1964, Krassilov, 1967, Rushforth, 1971, Nagalingum and Cantrill, 2006, Kvaček and Dašková, 2010, Hu and Taylor, 2014, Sender et al., 2015, Abu Hamad et al., 2016), but there are few records that date to the Late Cretaceous (Givulescu et al., 1986, Nishida et al., 1998, Herman and Kvaček, 2007, Halamski and Kvaček, 2015, Halamski and Kvaček, 2016). There is uncertainty about when the family became restricted to their present geographic distribution in Malaysia-Pacific region. Tidwell and Skog (1992) reported an anatomically matoniaceous stem from the lower Cenozoic of Tasmania, but probably reworked from older strata. The Eocene permineralized rhizomes from Chile (Nishida et al., 2014) and Oligocene leaves in the Bitterfeld Amber of Europe (Schmidt and Dörfelt, 2007) suggests a wide distribution of the Matoniaceae, or at least their relictual persistence in both hemispheres until the late Paleogene.

In southern South America the fossil record of Matoniaceae was based almost exclusively on dispersed spores, mostly including in the genera Matonisporites Couper emend. Dettmann and Dictyophyllidites Couper; however, these two spore genera have been also related to Dicksoniaceae, Dipteridaceae and Cyatheaceae (Balme, 1995, Rojo and Zavattieri, 2005, Olivera et al., 2015). Therefore, those occurrences are not conclusive evidence of Matoniaceae. The oldest record of Matonisporites/Dictyophyllidites complex comes from the Triassic in the central-western Argentina (Rojo and Zavattieri, 2005). Through the Jurassic and up to the mid-Cretaceous, these spore genera are diverse and widespread in Patagonia (Volkheimer and Salas, 1976, Volkheimer and Quattrocchio, 1981, Baldoni and Archangelsky, 1983, Archangelsky and Llorens, 2003, Quattrocchio et al., 2003, Zavattieri and Volkheimer, 2003, Garcia et al., 2006, Archangelsky et al., 2008, Medina et al., 2008, Olivera et al., 2010, Olivera et al., 2015, Archangelsky et al., 2012). Matonisporites/Dictyophyllidites records are less common in the uppermost Cretaceous (Papú and Sepúlveda, 1995, Papú, 2002, Povilauskas et al., 2008, Povilauskas, 2011) although they are recognized in Patagonia until the Miocene (i.e. Archangelsky, 1973, Petriella and Archangelsky, 1975, Quattrocchio and Volkheimer, 1990, Barreda, 1997a, Barreda, 1997b, Barreda and Palamarczuk, 2000, Melendi et al., 2003, Volkheimer et al., 2007).

The macroscopic fossil record of Matoniaceae for the whole South America is sparce (Pons, 1988 and cites therein; Nishida et al., 2014) but there are several reports from southernmost Patagonia (Table 1). In this work we revise the species Konijnenburgia alata (Halle) Kvaček et Dašková, a conclusively Matoniaceae fossil taxon, which is often common in mid-Cretaceous plant communities of southern Patagonia, Argentina. We provide a complete description and emended diagnosis for the species based on the revision of the type material, abundant and well-preserved new records from the Albian Piedra Clavada Formation, and previously published specimens from same unit but other localities (Halle, 1913, Piatnitzky, 1938, Passalia, 2007). The species is analyzed into the global Cretaceous records, providing a complete comparison with extant and fossil Matoniaceae.