Triassic Equisetites lateralis Phillips with strobilus in organic connection from Patagonia of Argentina and endophytic oviposition insect scars

Abstract

Equisetites lateralis Phillips (=Equisetum laterale (Phillips) Gould) (Equisetaceae) is recorded for the first time for the Triassic of Gondwana. The specimens come from the upper section of the Cañadón Largo Formation, late Ladinian–early Carnian, Santa Cruz Province, Argentina. The identification is based on sterile and fertile remains, preserved as stems, leaf sheaths, nodal diaphragms, and strobilus in organic connection. The first morphological and anatomical data of the epidermal cells and stomatal apparatus of Gondwanan Triassic Equisetites are presented. This species is characterized by having stems unbranched, 8–23–35 free leaves tips in the leaf sheaths, cart-wheel structure, internode and lower part of the leaf-sheath showing scattered sunken stomata and ovate terminal strobilus with whorls of peltate sporangiophores. Herein, we described the fine sculptures in the epidermal and subsidiary cells, as pilulae and thickenings of the outer walls surrounding the sunken stomata. The Patagonian specimens identified as E. lateralis display characters of both subgenus (Hippochaete and Equisetum) of extant Equisetum. The first record of oviposition scars tentatively assigned to Odonatoptera are described from Triassic of Argentina, and are identified as Paleoovoidus contactus. Oviposition scars and paleoenvironmental interpretation of the formation, suggest that these plants could have grown in shallow water of the local lacustrine/palustrine deposits.