Abstract Detail

Paleobotany

Sender, Luis Miguel [1], Doyle, James A. [2], Upchurch, Jr., Garland [3], Villanueva-Amadoz, Uxue [4], Diez, Jose Bienve [5].

Leaf and inflorescence evidence for near-basal Araceae in the latest Albian (mid-Cretaceous) of Spain.

Fossil leaves, inflorescences, and pollen from the Aptian-Albian of Brazil and Portugal have been assigned to Araceae, in the near-basal monocot order Alismatales, and increasingly diverse araceous leaves have been reported from the Late Cretaceous and Cenozoic. We report a well-preserved leaf and several inflorescences resembling Araceae from two localities in the Boundary Marls Unit (latest Albian) overlying the Utrillas Formation in Teruel Province, northestern Spain. The leaf, from Huesa del Común, shows an unthickened multistranded midrib in its lower portion, several orders of low-angle primary lateral veins, transverse veins crossing more than one order of parallel veins, additional veins connecting the finest parallel veins, and paracytic stomata on the adaxial side only. This suite of characters (but with anomocytic as well as paracytic stomata) is diagnostic of the North American genus Orontium in the near-basal araceous subfamily Orontioideae, and similar venation occurs with minor variations in later Cretaceous and early Cenozoic leaves assigned to Orontium and Orontiophyllum. However, phylogenetic analyses, using a modified version of the morphological dataset and the molecular phylogenetic tree of extant Araceae of Cusimano et al. (2011), indicate that this character combination may be ancestral for Araceae. As a result, the fossil could be either sister to Orontium, sister to Araceae as a whole, or nested at several points in a basal grade of the family, below the True Araceae clade. Several types of linear monocot-like leaves also occur at Huesa del Común. The inflorescences, from Estercuel, are spadices of closely packed, sessile flowers with usually four tepals, as in the dimerous flowers that are prevalent in perigoniate Araceae, and a long basal stipe, in contrast to derived Araceae in which the spathe is attached close to the fertile portion of the spadix. Stamens have not been identified, but a protruding central structure is presumably the gynoecium, which shows various degrees of enlargement in different specimens. Among living Araceae, similar inflorescences occur in Gymnostachys and Orontioideae. Phylogenetic analyses confirm that the inflorescences are related to Araceae, either sister to the family or nested within the same basal grade as the leaf from Huesa del Común. Considered together with reports from other regions, these results suggest that Araceae were one of the first families of monocots to diversify in the Cretaceous, but their radiation may still have been in its early stages during the late Albian.

1 - Universidad de Zaragoza, Departamento de Ciencias de la Tierra, Zaragoza, 50009, Spain
2 - University Of California Davis, DEPT OF EVOL & ECOLOGY, One Shields Avenue, Davis, CA, 95616-8537, USA
3 - Texas State University, Department Of Biology, 601 University Drive, San Marcos, TX, 78666, USA
4 - Estación Regional del Noroeste, UNAM, Instituto de Geología, Hermosillo, Sonora, 83000, Mexico
5 - Universidade de Vigo, Xeociencias Mariñas e Ordenación do Territorio, Vigo, 36310, Spain

Keywords:
angiosperms
Monocots
Araceae
Cretaceous
Paleobotany
phylogeny.

Presentation Type: Oral Paper
Session: 25, Cretaceous/Cenozoic/collections paleobotany
Location: Sundance 3/Omni Hotel
Date: Tuesday, June 27th, 2017
Time: 10:15 AM
Number: 25001
Abstract ID:398
Candidate for Awards:None