Millerocaulis (Erasmus) ex Tidwell (Osmundales, Filices) de la Formación Carrizal (Triásico Superior) de Marayes, provincia de San Juan, Argentina

Abstract

Millerocaulis (Erasmus) ex Tidwell (Osmundales, Filices) from the Carrrizal Formation
(Upper Triassic) from Marayes, San Juan province, Argentina. Based on newly found specimens, «Marayea
lutzi» Herbst 1994, of the Upper Triassic Carrizal Formation, from Marayes (San Juan province , Argentina) is
analyzed. Anatomical characters, specially those from the central cylinder, now defines the species as an ectophloicdictyoxylic
siphonostele (sensu Miller) and shows that it must be changed to Millerocaulis. Thus, Marayea
defined as a siphonostelic genus becomes invalid and an emended diagnosis for the type species is given. Also,
from the same locality and age other, rather big specimens, are described. They are not well preserved but the
available characters allow to incorporate them as Millerocaulis sp. These two species and others formerly described
of this genus, M. herbsti (Archangelsky & de la Sota) Tidwell and M. stipabonettii Herbst, from the Laguna
Colorada Formation (Santa Cruz province) and Cepeda Formation (San Juan province) respectively from Argentina
along with M. beardmorensis Schopf and Ashicaulis woolfei Rothwell, Taylor & Taylor, from the Fremouw
Formation (Antarctica) and the frond Osmunda claytoniites Phipps et. al.,as well as some petioles lacking cellular
structure but undoubtely belonging to Millerocaulis, from the Los Rastros Formation (San Juan province), all
from the upper Middle to Upper Triassic, show the diversification of the Osmundales as early as this time span,
at least in this part of Gondwana