DOI: 10.5061/dryad.z8w9ghxq2
title: Fossil snakes from the Eocene of India: New material with comments on phylogenetic relations and biogeographic and palaeoecological implications

description: Eocene snakes of India have the potential to shed light on the nature of
 snake diversification on the subcontinent following the Deccan volcanism
 at the Cretaceous–Paleogene boundary (K-Pg), when India was still a
 northward drifting isolated landmass prior to its collision with Asia.
 Here we report a diverse snake fauna from the Eocene of Kutch, western
 India. The fauna, dominated by aquatic forms, include palaeophiids, a
 giant madtsoiid and a possible nigerophiid. The palaeophiids from the
 middle Eocene (late Lutetian) comprise ?Palaeophis and Pterosphenus
 rannensis sp. nov. Together, these taxa enrich the record of fossil snakes
 the poorly known late Lutetian of India and represent the youngest record
 of Palaeophiidae from the Indian subcontinent. Pt. rannensis shows
 intermediate morphology between Palaeophis and Pterosphenus-grade snakes,
 and is phylogenetically the earliest-diverging member of Pterosphenus.
 Additionally, the middle Eocene Pt. biswasi is reassessed and retained as
 a valid taxon based on pterapophyseal morphology and overall form.
 Biogeographic considerations highlight the importance of Indian fossil
 record in understanding the origin and diversification of the genus
 Pterosphenus. The prevalence of niche partitioning is suggested for the
 palaeophiids, with Pt. rannensis recovered from a tidal setting and
 ?Palaeophis sp. from a marsh/swamp setting. The new Indian madtsoiid from
 the middle Eocene (early Lutetian) represents a sympatric taxon with the
 terrestrial/semi-aquatic giant Vasuki indicus co-existing in a back swamp
 marsh setting. The early Eocene (Ypresian) nigerophiid is among the oldest
 Cenozoic occurrences of this family globally.
description: # Fossil snakes from the Eocene of India: New material with comments on
 phylogenetic relations and biogeographic and palaeoecological implications
 [https://doi.org/10.5061/dryad.z8w9ghxq2](https://doi.org/10.5061/dryad.z8w9ghxq2) ## Description of the data and file structure This folder contains the appendices associated with the paper entitled "Fossil snakes from the Eocene of India: New material with comments on phylogenetic relations and biogeographic and palaeoecological implications". The data in these files are important for identification of the examined fossils; support and reproduction of the results of the anatomical and comparative study and phylogenetic analysis. These appendices are .txt files that contains the following: 1. Appendix 1- List of fossil specimens examined with information on their taxonomic designation and anatomical position. Abbreviation used: IITR/VPL/SB, Vertebrate Paleontology Laboratory, Indian Institute of Technology Roorkee, Roorkee, India 2. Appendix 2- Measurements of different parameters of the examined vertebrae. Institutional abbreviation: IITR/VPL/SB, Vertebrate Paleontology Laboratory, Indian Institute of Technology Roorkee, Roorkee, India Abbreviations for measured parameters: CL, centrum length; COH, cotyle height; COW, cotyle width; CNH, condyle height; CNW, condyle width; NAW, neural arch width; NCH, neural canal; NCW, neural canal width; NSH, neural spine height; NSW, neural spine width; POFL, postzygapophyseal facet length; POFW, postzygapophyseal facet width; POW, postzygapophyseal width; POα, postzygapohyseal angle; PRFL, prezygapophyseal facet length; PRFW, prezygapophyseal facet width; PRW, prezygapophyseal width; PRα, prezygapophyseal angle; PTH, height of pterapophysis; PT. VH, vertebral height from base of condyle to dorsal tip of pterapophysis; SYW, synapophyseal width; TVH, total vertebral height; ZSFL, zygosphenal facet length; ZSFW, zygosphenal facet width; ZSH, zygosphene height; ZSW, zygosphene width; ZSβ, zygosphene angle; ZS. VH, vertebral height from base of condyle to dorsal tip of zygapophysis. 3. Appendix 3-  List of characters along with the respective character states for the phylogenetic analysis carried out in this study. Abbreviations used: CL, centrum length; PTH, height of pterapophysis. **Software** The dataset for the phylogenetic analysis, based on the characters provided in Appendix 3, was edited using the software PAUP* version 4 3.99.169.0, and run using TNT version 1.6. To perform the phylogenetic analysis  the software (TNT) memory was set to retain 10,000 trees and a display buffer of 10 Mb. The Traditional Search option was used where the analysis constrains included 50 replications of Wagner trees, with bisection reconnection as the swapping algorithm, and 10 trees saved per replication. A detailed description of how the analysis was performed is given in the paper. ## Access information * Information for accessing the phylogenetic analysis dataset is given in the paper. Data was derived from the following sources: * The source of information for the dataset for the phylogenetic analysis and information on the taxa used are provided in the paper and Appendix 3.