Abstract Detail

Paleobotany

Matsunaga, Kelly K.S. [1], Manchester, Steven R [2], Smith, Selena [3], Srivastava, Rashmi [4], Kapgate, Dashrath [5].

Investigating taxonomic diversity and synonymy among fossil palms from the K-Pg transition of India.

The Arecaceae have an extensive fossil record that extends back to the Late Cretaceous, with the earliest unequivocal macrofossils dated as Coniacian-Santonian (~86 Ma) and putative representatives as early as the Aptian. One particularly rich palm flora inhabited the Indian subcontinent during the Late Cretaceous–early Paleogene (Maastrichtian­–Danian ~66 Ma) of India, and is represented by about 164 species described from the Deccan intertrappean beds (DIB). However, this number probably overestimates the true taxonomic diversity within the flora because it includes morphospecies described from different organs, some of which likely originated from the same taxon. Moreover, owing to challenges associated with resolving the taxonomy of fossil palm stems (Palmoxylon), which comprise the majority of described species in the DIB, better estimates of the true taxonomic diversity may come from studies on fruits. The fruit component of the flora includes 33 described species which have been assigned to or compared with the extant genera Nypa, Cocos, Hyphaene, and Areca, as well as the morphogenera Palmocarpon and Arecoidocarpon. Here we focus on species assigned to the genus Arecoidocarpon through reinvestigations of type specimens and comparisons with new fossil collections. Three species have been described: A. kulkarnii and A. prismaticum from Mohgaonkalan, and A. palasundarensis from Palasundar. Additionally, several Arecoidocarpon specimens closely resembling A. kulkarnii and A. palasundarensis have been collected recently from the localities Keria and Dhangaon. Arecoidocarpon prismaticum fruits can be readily distinguished from the others by the presence of an outer prismatic layer in the endocarp and longitudinal fibrovascular bundles in the mesocarp. In contrast, A. kulkarnii, A. palasundarensis, and the Keria/Dhangaon Arecoidocarpon all possess an endocarp comprised of up to six layers of the fibrovascular bundles, and mesocarp with fibrovascular bundles oriented perpendicular to the endocarp. Similarities in pericarp anatomy seen in these four Arecoidocarpon occurrences indicate that, rather than representing four difference species, these fossils correspond to a single widespread species and was probably abundant in the flora. Furthermore, Mohgaonkalan and Keria are situated in the western edge of the Mandla Lobe of the Deccan volcanic province, while Palasundar and Dhangaon are in the eastern region. Ar-Ar dating of the eastern Mandla Lobe indicates an early Paleogene age, while the western localities are considered Maastrichtian (Late Cretaceous). While precise age constraints of the fossil-bearing localities remain unclear, the geographic distribution of these Arecoidocarpon fossils implicates this taxon as one that potentially crossed the K-Pg boundary in India.

1 - University Of Michigan, Earth and Environmental Sciences, 1100 North University Avenue, Ann Arbor, MI, 48109, USA
2 - University Of Florida, Florida Museum Of Natural History, PO BOX 117800, Gainesville, FL, 32611, USA
3 - University Of Michigan, Department of Earth and Environmental Sciences, 1100 North University Avenue, 2534 CC Little Building, Ann Arbor, MI, 48109, USA
4 - Birbal Sahni Institute of Palaeobotany, 53 University Road, Lucknow 226 007, India
5 - J.M. Patel College, Department of Botany, Bhandara 441904-M.S., India

Keywords:
India
fossil
Cretaceous
Paleogene
K-Pg
Arecaceae
palm
Fruit.

Presentation Type: Oral Paper
Session: 7, Cookson/Moseley award presentations
Location: Sundance 4/Omni Hotel
Date: Monday, June 26th, 2017
Time: 11:00 AM
Number: 7004
Abstract ID:380
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award