Abstract Detail

Mesozoic and Cenozoic plant evolution and biotic change: A symposium in honor of Ruth Stockey

Manchester, Steven R. [1], Kapgate, Dasrath [2], Smith, Selena Y. [3], Pigg, Kathleen B. [4], Graham, Shirley [5].

Systematic affinities of the Enigmocarpon plant (Myrtales) from the late Cretaceous of India.

Enigmocarpon parijai Sahni is known from numerous permineralized flowers and fruits from cherts of the Deccan Intertrappean beds of central India, documenting a developmental series from young flowers to mature fruits. X-ray tomography of several fruits and high-resolution light and scanning electron microscopy of pollen from the anthers supplements previous observations from physically sectioned and serially peeled specimens to make this the most thoroughly documented angiosperm of the Deccan flora. Enigmocarpon conforms to the Myrtales in the presence of a well-developed hypanthium, bisexual flowers, stamens incurved in bud, and a single style with completely connate pistil. The impressive suite of morphological and anatomical characters known for this fossil make it ideal for inclusion with extant taxa in phylogenetic analyses. The flowers of Enigmocarpon parijai, commonly treated as Sahnianthus parijai Shukla, are pedicellate, and actinomorphic, with an elongate floral cup terminated by 7–9 valvate calyx lobes. Petals are absent; stamen filaments arise from the calyx at its junction with the hypanthium. There are ca. 8–12 stamens with introrse, longitudinally dehiscent anthers bearing psilate, tricolporate, pollen. The pistil is superior, stipitate, and contains 6–12 locules, with radial septation and axile placentation, and bears a single style with an elongate, capitate stigma. The anatropous, crassinucellate ovules are borne in two rows per locule. Fruits are thick-walled loculicidal capsules with the same number of locules as the ovary and showing the arrangement of seeds in two rows per locule. Seeds have a straight or slightly curved embryo chamber bordered by a larger bisymmetrical parenchymatous chamber through which the raphe passes. Since its first description, Enigmocarpon fruits and flowers have been considered most likely to represent Lythraceae. The fossil species is readily distinguished from Myrtaceae and Onagraceae, which have inferior ovaries and a relatively low carpel number. Most Lythraceae and some Melastomataceae share with Enigmocarpon the superior ovary and moderate number of stamens (6-12), and can have loculicidal capsules, but Melastomataceae have specializations of the stamen arrangement and anther morphology not seen in Enigmocarpon. Compared with extant genera of Lythraceae, however, Enigmocarpon presents a mosaic of characters difficult to align with a particular clade of the family. Its uniqueness might reflect the geographic isolation of India from other land masses during the late Cretaceous and Paleocene, or its status as an early diverging taxon. We explore the potential placement of this genus through a combined molecular and morphological phylogenetic analysis.

1 - University Of Florida, Florida Museum Of Natural History, PO Box 117800, Gainesville, FL, 32611, USA
2 - J.M. Patel College, Department of Botany, Bhandara , M.S., 441904, India
3 - University of Michigan, Department of Earth and Environmental Sciences, 2534 CC Little Building, 1100 North University Avenue, Ann Arbor, MI, 48109-1005, USA
4 - Arizona State University, School Of Life Sciences Faculty & Admin, Box 874501, Tempe, AZ, 85287-4501, USA
5 - Missouri Botanical Garden, St. Louis, MO, USA

Keywords:
Lythraceae
Deccan Intertrappean beds.

Presentation Type: Symposium Presentation
Session: SY14
Location: Salon 5/The Shaw Conference Centre
Date: Wednesday, July 29th, 2015
Time: 10:45 AM
Number: SY14007
Abstract ID:1242
Candidate for Awards:None