Abstract Detail

A synthesis of new paleontological and phylogenomic perspectives on gymnosperm evolution

Smith, Selena [1], Matsunaga, Kelly [2].

Conifer diversity of the Maastrichtian-Danian Deccan Intertrappean Beds of India.

The Deccan Intertrappean Beds (DIB) of India record the terrestrial flora of India at a time when India was geographically isolated, and during the global Cretaceous-Paleogene biotic crisis. Fossils are preserved in chert with 3D anatomical detail, and have much potential to expand our understanding of phylogenetic and biogeographic relationships among plants. The majority of species preserved here are angiosperms, however, other major plant groups are also represented and need to be considered for a holistic reconstruction of the assemblage. Conifers are known from wood, ovules, ovulate cones, and pollen cones primarily assigned to Araucariaceae or Podocarpaceae but also some to Taxaceae or incertae sedis. Wood is the most widely distributed, being found at six localities, in contrast to ovulate cones, which have only been recovered from two localities. The fossil conifer ovulate cones that have been described are being re-investigated in order to ascertain their morphology, structure, and phylogenetic affinities. Five taxa have been recognized to date: Mohgaostrobus and Harrisostrobus from the Mohgaonkalan locality, and Takliostrobus, Pityostrobus, and Indostrobus from the Takli locality. Some taxa are known only from a single specimen (e.g., Harrisostrobus, Indostrobus) while others are represented by multiple specimens (e.g., Takliostrobus). Previous investigations proposed affinities with Araucariaceae or Pinaceae. Original peels and slides were studied, complemented by X-ray micro-computed tomography that allowed non-destructive visualization of the three-dimensional structure of these specimens. One specimen of Takliostrobus was found to represent an infructescence of the monocot Viracarpon. Takliostrobus and Indostrobus cones have two seeds per cone-scale complex and other features suggesting affinities to Pinaceae. While these taxa show some differences, such as seed shape, the overall similarity suggests they are likely congeneric. In contrast, “Pityostrobus” crassitesta, Mohgaostrobus, and Harrisostrobus all have >5 seeds per cone-scale complex. Seeds are tightly clustered together, much more elongate than wide, and appear to have relatively thick sclerotic seed coats, two chambers, and are surrounded by a parenchymatous tissue, possibly a wing. These seeds are unlike any other gymnosperm seeds we have been able to find to date, and thus raise the possibility that these conifers may represent an extinct, possibly endemic, Indian lineage. Further work is underway to determine their affinities. The taxonomy of the cones needs to be revised and affinities re-considered, but they demonstrate there was some small diversity of conifers in India at the Cretaceous-Paleogene boundary.

1 - Department Of Earth & Environmental Sciences, 1100 North University Avenue, 2534 CC Little Building, Ann Arbor, MI, 48109, United States
2 - University Of Michigan, Earth And Environmental Sciences, 1100 N University Ave, 2534 CC Little Bldg, Ann Arbor, MI, 48109, United States

Keywords:
Pinaceae
Cretaceous
seed cone
biodiversity.

Presentation Type: Colloquium Presentations
Session: C04, A synthesis of new paleontological and phylogenomic perspectives on gymnosperm evolution
Location: 102/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 3:45 PM
Number: C04009
Abstract ID:793
Candidate for Awards:None